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Sample records for tissue equivalent materials

  1. Dose distribution around ion track in tissue equivalent material

    International Nuclear Information System (INIS)

    Zhang Wenzhong; Guo Yong; Luo Yisheng

    2007-01-01

    Objective: To study the energy deposition micro-specialty of ions in body-tissue or tissue equivalent material (TEM). Methods: The water vapor was determined as the tissue equivalent material, based on the analysis to the body-tissue, and Monte Carlo method was used to simulate the behavior of proton in the tissue equivalent material. Some features of the energy deposition micro-specialty of ion in tissue equivalent material were obtained through the analysis to the data from calculation. Results: The ion will give the energy by the way of excitation and ionization in material, then the secondary electrons will be generated in the progress of ionization, these electron will finished ions energy deposition progress. When ions deposited their energy, large amount energy will be in the core of tracks, and secondary electrons will devote its' energy around ion track, the ion dose distribution is then formed in TEM. Conclusions: To know biological effects of radiation , the research to dose distribution of ions is of importance(significance). (authors)

  2. Detection of ultraviolet radiation using tissue equivalent radiochromic gel materials

    International Nuclear Information System (INIS)

    Bero, M A; Abukassem, I

    2009-01-01

    Ferrous Xylenol-orange Gelatin gel (FXG) is known to be sensitive to ionising radiation such as γ and X-rays. The effect of ionising radiation is to produce an increase in the absorption over a wide region of the visible spectrum, which is proportional to the absorbed dose. This study demonstrates that FXG gel is sensitive to ultraviolet radiation and therefore it could functions as UV detector. Short exposure to UV radiation produces linear increase in absorption measured at 550nm, however high doses of UV cause the ion indicator colour to fad away in a manner proportional to the incident UV energy. Light absorbance increase at the rate of 1.1% per minute of irradiation was monitored. The exposure level at which the detector has linear response is comparable to the natural summer UV radiation. Evaluating the UV ability to pass through tissue equivalent gel materials shows that most of the UV gets absorbed in the first 5mm of the gel materials, which demonstrate the damaging effects of this radiation type on human skin and eyes. It was concluded that FXG gel dosimeter has the potential to offer a simple, passive ultraviolet radiation detector with sensitivity suitable to measure and visualises the natural sunlight UV exposure directly by watching the materials colour changes.

  3. Detection of ultraviolet radiation using tissue equivalent radiochromic gel materials

    Science.gov (United States)

    Bero, M. A.; Abukassem, I.

    2009-05-01

    Ferrous Xylenol-orange Gelatin gel (FXG) is known to be sensitive to ionising radiation such as γ and X-rays. The effect of ionising radiation is to produce an increase in the absorption over a wide region of the visible spectrum, which is proportional to the absorbed dose. This study demonstrates that FXG gel is sensitive to ultraviolet radiation and therefore it could functions as UV detector. Short exposure to UV radiation produces linear increase in absorption measured at 550nm, however high doses of UV cause the ion indicator colour to fad away in a manner proportional to the incident UV energy. Light absorbance increase at the rate of 1.1% per minute of irradiation was monitored. The exposure level at which the detector has linear response is comparable to the natural summer UV radiation. Evaluating the UV ability to pass through tissue equivalent gel materials shows that most of the UV gets absorbed in the first 5mm of the gel materials, which demonstrate the damaging effects of this radiation type on human skin and eyes. It was concluded that FXG gel dosimeter has the potential to offer a simple, passive ultraviolet radiation detector with sensitivity suitable to measure and visualises the natural sunlight UV exposure directly by watching the materials colour changes.

  4. Characterization of tissue-equivalent materials for use in construction of physical phantoms

    International Nuclear Information System (INIS)

    Souza, Edvan V. de; Oliveira, Alex C.H. de; Vieira, Jose W.; Lima, Fernando R.A.

    2013-01-01

    Phantoms are physical or computational models used to simulate the transport of ionizing radiation, their interactions with human body tissues and evaluate the deposition of energy. Depending on the application, you can build phantoms of various types and features. The physical phantoms are made of materials with behavior similar to human tissues exposed to ionizing radiation, the so-called tissue-equivalent materials. The characterization of various tissue-equivalent materials is important for the choice of materials to be used is appropriate, seeking a better cost-benefit ratio. The main objective of this work is to produce tables containing the main characteristics of tissue-equivalent materials. These tables were produced in Microsoft Office Excel. Among the main features of tissue-equivalent materials that were added to the tables, are density, chemical composition, physical state, chemical stability and solubility. The main importance of this work is to contribute to the construction of high-quality physical phantoms and avoid the waste of materials

  5. Polyurethane as a base for a family of tissue equivalent materials

    International Nuclear Information System (INIS)

    Griffith, R.V.

    1980-01-01

    Recent experience gained in the selection of tissue equivalent materials for the construction of whole body counting phantoms has shown that commercially available polyurethane can be used as a base for a variety of tissue equivalent materials. Tissues simulated include lung, adipose, muscle, cartilage and rib bone. When selecting tissue equivalent materials it is important to understand what tissue properties must be simulated. Materials that simply simulate the linear attenuation of low energy photons for example, are not very likely to simulate neutron interaction properties accurately. With this in mind, we have developed more than one simulation composition for a given tissue, depending on the purpose to which the simulant is to be applied. Simple simulation of linear attenuation can be achieved by addition of carefully measured amounts of higher Z material, such as calcium carbonate to the polyurethane. However, the simulation necessary for medical scanning purposes, or for use in mixed radiation fields requires more complex formulations to yield proper material density, hydrogen and nitrogen content, electron density, and effective atomic number. Though polyurethane has limitations for simulation of tissues that differ markedly from its inherent composition (such as compacted bone), it is safe and easily used in modestly equipped laboratories. The simulants are durable and generally flexible. They can also be easily cast in irregular shapes to simulate specific organ geometries. (author)

  6. Polyurethane as a base for a family of tissue equivalent materials

    International Nuclear Information System (INIS)

    Griffith, R.V.

    1980-01-01

    Polyurethane was used as a base material for a wide variety of tissue simulating applications. The technique in fabrication is similar to that of epoxy, however, the end products are generally more flexible for use in applications where flexibility is valuable. The material can be fabricated with relatively small laboratory equipment. The use of polyurethane provides the dosimetrist with the capability of making specific, accurate, on-the-spot tissue equivalent formulations to meet situations which require immediate calibration and response

  7. Measurement of californium-252 gamma photons depth dose distribution in tissue equivalent material. Vol. 4

    Energy Technology Data Exchange (ETDEWEB)

    Fadel, M A; El-Fiki, M A; Eissa, H M; Abdel-Hafez, A; Naguib, S H [National Institute of Standards, Cairo (Egypt)

    1996-03-01

    Phantom of tissue equivalent material with and without bone was used measuring depth dose distribution of gamma-rays from californium-252 source. The source was positioned at center of perspex walled phantom. Depth dose measurements were recorded for X, Y and Z planes at different distances from source. TLD 700 was used for measuring the dose distribution. Results indicate that implantation of bone in tissue equivalent medium cause changes in the gamma depth dose distribution which varies according to variation in bone geometry. 9 figs.

  8. SU-D-BRC-04: Development of Proton Tissue Equivalent Materials for Calibration and Dosimetry Studies

    Energy Technology Data Exchange (ETDEWEB)

    Olguin, E [Gainesville, FL (United States); Flampouri, S [University of Florida Proton Therapy Institute, Jacksonville, FL (United States); Lipnharski, I [University of Florida, Gainesville, FL (United States); Bolch, W [University Florida, Gainesville, FL (United States)

    2016-06-15

    Purpose: To develop new proton tissue equivalent materials (PTEM), urethane and fiberglass based, for proton therapy calibration and dosimetry studies. Existing tissue equivalent plastics are applicable only for x-rays because they focus on matching mass attenuation coefficients. This study aims to create new plastics that match mass stopping powers for proton therapy applications instead. Methods: New PTEMs were constructed using urethane and fiberglass resin materials for soft, fat, bone, and lung tissue. The stoichiometric analysis method was first used to determine the elemental composition of each unknown constituent. New initial formulae were then developed for each of the 4 PTEMs using the new elemental compositions and various additives. Samples of each plastic were then created and exposed to a well defined proton beam at the UF Health Proton Therapy Institute (UFHPTI) to validate its mass stopping power. Results: The stoichiometric analysis method revealed the elemental composition of the 3 components used in creating the PTEMs. These urethane and fiberglass based resins were combined with additives such as calcium carbonate, aluminum hydroxide, and phenolic micro spheres to achieve the desired mass stopping powers and densities. Validation at the UFHPTI revealed adjustments had to be made to the formulae, but the plastics eventually had the desired properties after a few iterations. The mass stopping power, density, and Hounsfield Unit of each of the 4 PTEMs were within acceptable tolerances. Conclusion: Four proton tissue equivalent plastics were developed: soft, fat, bone, and lung tissue. These plastics match each of the corresponding tissue’s mass stopping power, density, and Hounsfield Unit, meaning they are truly tissue equivalent for proton therapy applications. They can now be used to calibrate proton therapy treatment planning systems, improve range uncertainties, validate proton therapy Monte Carlo simulations, and assess in-field and out

  9. SU-F-T-181: Proton Therapy Tissue-Equivalence of 3D Printed Materials

    International Nuclear Information System (INIS)

    Taylor, P; Craft, D; Followill, D; Howell, R

    2016-01-01

    Purpose: This work investigated the proton tissue-equivalence of various 3D printed materials. Methods: Three 3D printers were used to create 5 cm cubic phantoms made of different plastics with varying percentages of infill. White resin, polylactic acid (PLA), and NinjaFlex plastics were used. The infills ranged from 15% to 100%. Each phantom was scanned with a CT scanner to obtain the HU value. The relative linear stopping power (RLSP) was then determined using a multi-layer ion chamber in a 200 MeV proton beam. The RLSP was measured both parallel and perpendicular to the print direction for each material. Results: The HU values of the materials ranged from lung-equivalent (−820 HU σ160) when using a low infill, to soft-tissue-equivalent 159 (σ12). The RLSP of the materials depended on the orientation of the beam relative to the print direction. When the proton beam was parallel to the print direction, the RLSP was generally higher than the RLSP in the perpendicular orientation, by up to 45%. This difference was smaller (less than 6%) for the materials with 100% infill. For low infill cubes irradiated parallel to the print direction, the SOBP curve showed extreme degradation of the beam in the distal region. The materials with 15–25% infill had wide-ranging agreement with a clinical HU-RLSP conversion curve, with some measurements falling within 1% of the curve and others deviating up to 45%. The materials with 100% infill all fell within 7% of the curve. Conclusion: While some materials tested fall within 1% of a clinical HU-RLSP curve, caution should be taken when using 3D printed materials with proton therapy, as the orientation of the beam relative to the print direction can result in a large change in RLSP. Further investigation is needed to measure how the infill pattern affects the material RLSP. This work was supported by PHS grant CA180803.

  10. SU-F-T-181: Proton Therapy Tissue-Equivalence of 3D Printed Materials

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P; Craft, D; Followill, D; Howell, R [UT MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: This work investigated the proton tissue-equivalence of various 3D printed materials. Methods: Three 3D printers were used to create 5 cm cubic phantoms made of different plastics with varying percentages of infill. White resin, polylactic acid (PLA), and NinjaFlex plastics were used. The infills ranged from 15% to 100%. Each phantom was scanned with a CT scanner to obtain the HU value. The relative linear stopping power (RLSP) was then determined using a multi-layer ion chamber in a 200 MeV proton beam. The RLSP was measured both parallel and perpendicular to the print direction for each material. Results: The HU values of the materials ranged from lung-equivalent (−820 HU σ160) when using a low infill, to soft-tissue-equivalent 159 (σ12). The RLSP of the materials depended on the orientation of the beam relative to the print direction. When the proton beam was parallel to the print direction, the RLSP was generally higher than the RLSP in the perpendicular orientation, by up to 45%. This difference was smaller (less than 6%) for the materials with 100% infill. For low infill cubes irradiated parallel to the print direction, the SOBP curve showed extreme degradation of the beam in the distal region. The materials with 15–25% infill had wide-ranging agreement with a clinical HU-RLSP conversion curve, with some measurements falling within 1% of the curve and others deviating up to 45%. The materials with 100% infill all fell within 7% of the curve. Conclusion: While some materials tested fall within 1% of a clinical HU-RLSP curve, caution should be taken when using 3D printed materials with proton therapy, as the orientation of the beam relative to the print direction can result in a large change in RLSP. Further investigation is needed to measure how the infill pattern affects the material RLSP. This work was supported by PHS grant CA180803.

  11. Positron range in tissue-equivalent materials: experimental microPET studies

    Science.gov (United States)

    Alva-Sánchez, H.; Quintana-Bautista, C.; Martínez-Dávalos, A.; Ávila-Rodríguez, M. A.; Rodríguez-Villafuerte, M.

    2016-09-01

    In this work an experimental investigation was carried out to study the effect that positron range has over positron emission tomography (PET) scans through measurements of the line spread function (LSF) in tissue-equivalent materials. Line-sources consisted of thin capillary tubes filled with 18F, 13N or 68Ga water-solution inserted along the axis of symmetry of cylindrical phantoms constructed with the tissue-equivalent materials: lung (inhale and exhale), adipose tissue, solid water, trabecular and cortical bone. PET scans were performed with a commercial small-animal PET scanner and image reconstruction was carried out with filtered-backprojection. Line-source distributions were analyzed using radial profiles taken on axial slices from which the spatial resolution was determined through the full-width at half-maximum, tenth-maximum, twentieth-maximum and fiftieth-maximum. A double-Gaussian model of the LSFs was used to fit experimental data which can be incorporated into iterative reconstruction methods. In addition, the maximum activity concentration in the line-sources was determined from reconstructed images and compared to the known values for each case. The experimental data indicates that positron range in different materials has a strong effect on both spatial resolution and activity concentration quantification in PET scans. Consequently, extra care should be taken when computing standard-uptake values in PET scans, in particular when the radiopharmaceutical is taken up by different tissues in the body, and more even so with high-energy positron emitters.

  12. SU-E-T-424: Feasibility of 3D Printed Radiological Equivalent Customizable Tissue Like Materials

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D; Ferreira, C; Ahmad, S [University of Oklahoma Health Science Center, Oklahoma City, OK (United States)

    2015-06-15

    Purpose: To investigate the feasibility of 3D printing CT# specific radiological equivalent tissue like materials. Methods: A desktop 3D printer was utilized to create a series of 3 cm x 3 cm x 2 cm PLA plastic blocks of varying fill densities. The fill pattern was selected to be hexagonal (Figure 1). A series of blocks was filled with paraffin and compared to a series filled with air. The blocks were evaluated with a “GE Lightspeed” 16 slice CT scanner and average CT# of the centers of the materials was determined. The attenuation properties of the subsequent blocks were also evaluated through their isocentric irradiation via “TrueBeam” accelerator under six beam energies. Blocks were placed upon plastic-water slabs of 4 cm in thickness assuring electronic equilibrium and data was collected via Sun Nuclear “Edge” diode detector. Relative changes in dose were compared with those predicted by Varian “Eclipse” TPS. Results: The CT# of 3D printed blocks was found to be a controllable variable. The fill material was able to narrow the range of variability in each sample. The attenuation of the block tracked with the density of the total fill structure. Assigned CT values in the TPS were seen to fall within an expected range predicted by the CT scans of the 3D printed blocks. Conclusion: We have demonstrated that it is possible to 3D print materials of varying tissue equivalencies, and that these materials have radiological properties that are customizable and predictable.

  13. SU-E-T-424: Feasibility of 3D Printed Radiological Equivalent Customizable Tissue Like Materials

    International Nuclear Information System (INIS)

    Johnson, D; Ferreira, C; Ahmad, S

    2015-01-01

    Purpose: To investigate the feasibility of 3D printing CT# specific radiological equivalent tissue like materials. Methods: A desktop 3D printer was utilized to create a series of 3 cm x 3 cm x 2 cm PLA plastic blocks of varying fill densities. The fill pattern was selected to be hexagonal (Figure 1). A series of blocks was filled with paraffin and compared to a series filled with air. The blocks were evaluated with a “GE Lightspeed” 16 slice CT scanner and average CT# of the centers of the materials was determined. The attenuation properties of the subsequent blocks were also evaluated through their isocentric irradiation via “TrueBeam” accelerator under six beam energies. Blocks were placed upon plastic-water slabs of 4 cm in thickness assuring electronic equilibrium and data was collected via Sun Nuclear “Edge” diode detector. Relative changes in dose were compared with those predicted by Varian “Eclipse” TPS. Results: The CT# of 3D printed blocks was found to be a controllable variable. The fill material was able to narrow the range of variability in each sample. The attenuation of the block tracked with the density of the total fill structure. Assigned CT values in the TPS were seen to fall within an expected range predicted by the CT scans of the 3D printed blocks. Conclusion: We have demonstrated that it is possible to 3D print materials of varying tissue equivalencies, and that these materials have radiological properties that are customizable and predictable

  14. Experimental evaluation of the thermal properties of two tissue equivalent phantom materials.

    Science.gov (United States)

    Craciunescu, O I; Howle, L E; Clegg, S T

    1999-01-01

    Tissue equivalent radio frequency (RF) phantoms provide a means for measuring the power deposition of various hyperthermia therapy applicators. Temperature measurements made in phantoms are used to verify the accuracy of various numerical approaches for computing the power and/or temperature distributions. For the numerical simulations to be accurate, the electrical and thermal properties of the materials that form the phantom should be accurately characterized. This paper reports on the experimentally measured thermal properties of two commonly used phantom materials, i.e. a rigid material with the electrical properties of human fat, and a low concentration polymer gel with the electrical properties of human muscle. Particularities of the two samples required the design of alternative measuring techniques for the specific heat and thermal conductivity. For the specific heat, a calorimeter method is used. For the thermal diffusivity, a method derived from the standard guarded comparative-longitudinal heat flow technique was used for both materials. For the 'muscle'-like material, the thermal conductivity, density and specific heat at constant pressure were measured as: k = 0.31 +/- 0.001 W(mK)(-1), p = 1026 +/- 7 kgm(-3), and c(p) = 4584 +/- 107 J(kgK)(-1). For the 'fat'-like material, the literature reports on the density and specific heat such that only the thermal conductivity was measured as k = 0.55 W(mK)(-1).

  15. Evaluation of tissue-equivalent materials to be used as human brain tissue substitute in dosimetry for diagnostic radiology

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, C.C., E-mail: cassio.c.ferreira@gmail.co [Departamento de Fisica, Universidade Federal de Sergipe, Postal Code 353, Sergipe-SE 49100-000 (Brazil); Ximenes Filho, R.E.M., E-mail: raimundoximenes@hotmail.co [Departamento de Fisica, Universidade Federal de Sergipe, Postal Code 353, Sergipe-SE 49100-000 (Brazil); Vieira, J.W., E-mail: jwvieira@br.inter.ne [Centro Federal de Educacao Tecnologica de Pernambuco (CEFET-PE), Av. Professor Luiz Freire, 500 Curado, CEP 50740-540, Recife (Brazil); Escola Politecnica de Pernambuco, Universidade de Pernambuco (EPP/UPE), Rua Benfica, 455, Madalena, CEP 50720-001, Recife (Brazil); Tomal, A., E-mail: alessandratomal@pg.ffclrp.usp.b [Departamento de Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, Ribeirao Preto-SP 14040-90 (Brazil); Poletti, M.E., E-mail: poletti@ffclrp.usp.b [Departamento de Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, Ribeirao Preto-SP 14040-90 (Brazil); Garcia, C.A.B., E-mail: cgarcia@ufs.b [Departamento de Quimica, Universidade Federal de Sergipe, Postal Code 353, Sergipe-SE 49100-000 (Brazil); Maia, A.F., E-mail: afmaia@ufs.b [Departamento de Fisica, Universidade Federal de Sergipe, Postal Code 353, Sergipe-SE 49100-000 (Brazil)

    2010-08-15

    Tissue-equivalent materials to be used as substitutes for human brain tissue in dosimetry for diagnostic radiology have been investigated in terms of calculated total mass attenuation coefficient ({mu}/{rho}), calculated mass energy-absorption coefficient ({mu}{sub en}/{rho}) and absorbed dose. Measured linear attenuation coefficients ({mu}) have been used for benchmarking the calculated total mass attenuation coefficient ({mu}/{rho}). The materials examined were bolus, nylon (registered) , orange articulation wax, red articulation wax, PMMA (polymethylmethacrylate), bees wax, paraffin I, paraffin II, pitch and water. The results show that water is the best substitute for brain among the materials investigated. The average percentage differences between the calculated {mu}/{rho} and {mu}{sub en}/{rho} coefficients for water and those for brain were 1.0% and 2.5%, respectively. Absorbed doses determined by Monte Carlo methods confirm water as being the best brain substitute to be used in dosimetry for diagnostic radiology, showing maximum difference of 0.01%. Additionally this study showed that PMMA, a material often used for the manufacturing of head phantoms for computed tomography, cannot be considered to be a suitable substitute for human brain tissue in dosimetry.

  16. Assessment of doses caused by electrons in thin layers of tissue-equivalent materials, using MCNP.

    Science.gov (United States)

    Heide, Bernd

    2013-10-01

    Absorbed doses caused by electron irradiation were calculated with Monte Carlo N-Particle transport code (MCNP) for thin layers of tissue-equivalent materials. The layers were so thin that the calculation of energy deposition was on the border of the scope of MCNP. Therefore, in this article application of three different methods of calculation of energy deposition is discussed. This was done by means of two scenarios: in the first one, electrons were emitted from the centre of a sphere of water and also recorded in that sphere; and in the second, an irradiation with the PTB Secondary Standard BSS2 was modelled, where electrons were emitted from an (90)Sr/(90)Y area source and recorded inside a cuboid phantom made of tissue-equivalent material. The speed and accuracy of the different methods were of interest. While a significant difference in accuracy was visible for one method in the first scenario, the difference in accuracy of the three methods was insignificant for the second one. Considerable differences in speed were found for both scenarios. In order to demonstrate the need for calculating the dose in thin small zones, a third scenario was constructed and simulated as well. The third scenario was nearly equal to the second one, but a pike of lead was assumed to be inside the phantom in addition. A dose enhancement (caused by the pike of lead) of ∼113 % was recorded for a thin hollow cylinder at a depth of 0.007 cm, which the basal-skin layer is referred to in particular. Dose enhancements between 68 and 88 % were found for a slab with a radius of 0.09 cm for all depths. All dose enhancements were hardly noticeable for a slab with a cross-sectional area of 1 cm(2), which is usually applied to operational radiation protection.

  17. Determination of tissue equivalent materials of a physical 8-year-old phantom for use in computed tomography

    International Nuclear Information System (INIS)

    Akhlaghi, Parisa; Miri Hakimabad, Hashem; Rafat Motavalli, Laleh

    2015-01-01

    This paper reports on the methodology applied to select suitable tissue equivalent materials of an 8-year phantom for use in computed tomography (CT) examinations. To find the appropriate tissue substitutes, first physical properties (physical density, electronic density, effective atomic number, mass attenuation coefficient and CT number) of different materials were studied. Results showed that, the physical properties of water and polyurethane (as soft tissue), B-100 and polyvinyl chloride (PVC) (as bone) and polyurethane foam (as lung) agree more with those of original tissues. Then in the next step, the absorbed doses in the location of 25 thermoluminescent dosimeters (TLDs) as well as dose distribution in one slice of phantom were calculated for original and these proposed materials by Monte Carlo simulation at different tube voltages. The comparisons suggested that at tube voltages of 80 and 100 kVp using B-100 as bone, water as soft tissue and polyurethane foam as lung is suitable for dosimetric study in pediatric CT examinations. In addition, it was concluded that by considering just the mass attenuation coefficient of different materials, the appropriate tissue equivalent substitutes in each desired X-ray energy range could be found. - Highlights: • A methodology to select tissue equivalent materials for use in CT was proposed. • Physical properties of different materials were studied. • TLDs dose and dose distribution were calculated for original and proposed materials. • B-100 as bone, and water as soft tissue are best substitute materials at 80 kVp. • Mass attenuation coefficient is determinant for selecting best tissue substitutes

  18. The analysis for energy distribution and biological effects of the clusters from electrons in the tissue equivalent material

    International Nuclear Information System (INIS)

    Zhang Wenzhong; Guo Yong; Luo Yisheng; Wang Yong

    2004-01-01

    Objective: To study energy distribution of the clusters from electrons in the tissue equivalent material, and discuss the important aspects of these clusters on inducing biological effects. Methods: Based on the physical mechanism for electrons interacting with tissue equivalent material, the Monte Carlo (MC) method was used. The electron tracks were lively simulated on an event-by-event (ionization, excitation, elastic scattering, Auger electron emission) basis in the material. The relevant conclusions were drawn from the statistic analysis of these events. Results: The electrons will deposit their energy in the form (30%) of cluster in passing through tissue equivalent material, and most clusters (80%) have the energy amount of more than 50 eV. The cluster density depends on its diameter and energy of electrons, and the deposited energy in the cluster depends on the type and energy of radiation. Conclusion: The deposited energy in cluster is the most important factor in inducing all sort of lesions on DNA molecules in tissue cells

  19. Critical study of some soft-tissue equivalent material. Sensitivity to neutrons of 1 keV to 14 MeV

    International Nuclear Information System (INIS)

    Kerviler, H. de; Pages, L.; Tardy-Joubert, Ph.

    1965-01-01

    Authors have studied the elastic and inelastic reactions on various elements contribution to kerma in standard soft tissue and as a function of neutron energy from 1 keV to 14 MeV the ratio of kerma in tissue equivalent material to kerma in soft tissue. The results of calculations are made for materials without hydrogen in view to state exactly their neutron sensitivity and for the following hydrogenous materials: Rossi and Failla plastic, MixD, pure polyethylene and a new CEA tissue equivalent (a magnesium fluoride and polyethylene compound). Results for γ-rays are given. (authors) [fr

  20. Energy absorption buildup factors for thermoluminescent dosimetric materials and their tissue equivalence

    DEFF Research Database (Denmark)

    Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

    2010-01-01

    Gamma ray energy-absorption buildup factors were computed using the five-parameter geometric progression (G-P) fitting formula for seven thermoluminescent dosimetric (TLD) materials in the energy range 0.015-15 MeV, and for penetration depths up to 40 mfp (mean free path). The generated energy-absorption...

  1. A simple method to evaluate the composition of tissue-equivalent phantom materials

    International Nuclear Information System (INIS)

    Geske, G.

    1977-01-01

    A description is given of a method to calculate the composition of phantom materials with given density and radiation-physical parameters mixed of components, of which are known their chemical composition and their effective specific volumes. By an example of a simple composition with three components the method is illustrated. The results of this example and some experimental details that must be considered are discussed. (orig.) [de

  2. Tissue equivalence in neutron dosimetry

    International Nuclear Information System (INIS)

    Nutton, D.H.; Harris, S.J.

    1980-01-01

    A brief review is presented of the essential features of neutron tissue equivalence for radiotherapy and gives the results of a computation of relative absorbed dose for 14 MeV neutrons, using various tissue models. It is concluded that for the Bragg-Gray equation for ionometric dosimetry it is not sufficient to define the value of W to high accuracy and that it is essential that, for dosimetric measurements to be applicable to real body tissue to an accuracy of better than several per cent, a correction to the total absorbed dose must be made according to the test and tissue atomic composition, although variations in patient anatomy and other radiotherapy parameters will often limit the benefits of such detailed dosimetry. (U.K.)

  3. Characterization of tissue-equivalent materials for use in construction of physical phantoms; Caracterizacao de materiais tecido-equivalentes para uso em construcao de fantomas fisicos

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Edvan V. de, E-mail: edvanmsn@hotmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFFPE), Recife, PE (Brazil); Oliveira, Alex C.H. de, E-mail: oliveira_ach@yahoo.com [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Vieira, Jose W., E-mail: jose.wilson59@uol.com.br [Escola Politecnica de Pernambuco (UPE), Recife, PE (Brazil); Lima, Fernando R.A., E-mail: falima@cenen.gov.br [Centro Regional de Ciencias Nucleares (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

    2013-07-01

    Phantoms are physical or computational models used to simulate the transport of ionizing radiation, their interactions with human body tissues and evaluate the deposition of energy. Depending on the application, you can build phantoms of various types and features. The physical phantoms are made of materials with behavior similar to human tissues exposed to ionizing radiation, the so-called tissue-equivalent materials. The characterization of various tissue-equivalent materials is important for the choice of materials to be used is appropriate, seeking a better cost-benefit ratio. The main objective of this work is to produce tables containing the main characteristics of tissue-equivalent materials. These tables were produced in Microsoft Office Excel. Among the main features of tissue-equivalent materials that were added to the tables, are density, chemical composition, physical state, chemical stability and solubility. The main importance of this work is to contribute to the construction of high-quality physical phantoms and avoid the waste of materials.

  4. Preliminary studies on fragmentation in tissue-equivalent material produced by 55 MeV/u 40Ar17+ ion beam

    International Nuclear Information System (INIS)

    Dang Bingrong; Wei Zengquan; Duan Limin; Zhang Baoguo; Li Songlin; Yin Xu; Zhu Yongtai; Li Wenjian; Li Qiang; Yuan Shibin

    2002-01-01

    By using a 55 MeV/u 40 Ar 17+ beam produced by HIRFL, the distribution of fragments in 1.5 mm lucite on three different directions were measured at the radiobiology terminal. Feasibilities of the phoswich detector composed of fast plastic scintillator and CsI(Tl) detectors for determination of angular distribution of fragments in tissue-equivalent materials were investigated. The results obtained were satisfactory

  5. Preparation of A-150 tissue-equivalent plastic films

    International Nuclear Information System (INIS)

    Saion, E.B.; Shaari, A.H.; Watt, D.E.

    1992-01-01

    A-150 tissue-equivalent (TE) plastic is widely used as a wall material for tissue-equivalent proportional counters (TEPCS) used in experimental microdosimetry. The objective of this note is to give a technical account of how A-150 TE plastic film can be fabricated in the laboratory from commercially available A-150 TE plastic. (author)

  6. Determination of dose equivalent with tissue-equivalent proportional counters

    International Nuclear Information System (INIS)

    Dietze, G.; Schuhmacher, H.; Menzel, H.G.

    1989-01-01

    Low pressure tissue-equivalent proportional counters (TEPC) are instruments based on the cavity chamber principle and provide spectral information on the energy loss of single charged particles crossing the cavity. Hence such detectors measure absorbed dose or kerma and are able to provide estimates on radiation quality. During recent years TEPC based instruments have been developed for radiation protection applications in photon and neutron fields. This was mainly based on the expectation that the energy dependence of their dose equivalent response is smaller than that of other instruments in use. Recently, such instruments have been investigated by intercomparison measurements in various neutron and photon fields. Although their principles of measurements are more closely related to the definition of dose equivalent quantities than those of other existing dosemeters, there are distinct differences and limitations with respect to the irradiation geometry and the determination of the quality factor. The application of such instruments for measuring ambient dose equivalent is discussed. (author)

  7. Open-air ionisation chambers with walls of soft-tissue equivalent material for measuring photon doses

    International Nuclear Information System (INIS)

    Vialettes, H.; Anceau, J.C.; Grand, M.; Petit, G.

    1968-01-01

    The ionisation chambers presented in this report constitute a contribution to research into methods of carrying out correct determinations in the field of health physics. The use of a mixture of teflon containing 42.5 per cent by weight of carbon for the chamber walls makes it possible to measure directly the dose absorbed in air through 300 mg/cm 2 of soft tissue and, consequently, the dose absorbed in the soft tissues with a maximum error of 10 per cent for photon energies of between 10 keV and 10 MeV. Furthermore since this material does not contain hydrogen, the chamber has a sensitivity to neutrons which is much less than other chambers in current use. Finally the shape of these chambers has been studied with a view to obtaining a satisfactory measurement from the isotropy point of view; for example for gamma radiation of 27 keV, the 3 litre chamber is isotropic to within 10 per cent over 270 degrees, and the 12 litre chamber is isotropic to within 10 per cent over 300 degrees; for 1.25 MeV gamma radiation this range is extended over 330 degrees for the 3 litre chamber, and 360 degrees for the 12 litre chamber. This report presents the measurements carried out with these chambers as well as the results obtained. These results are then compared to those obtained with other chambers currently used in the field of health physics. (authors) [fr

  8. A formulation of tissue- and water-equivalent materials using the stoichiometric analysis method for CT-number calibration in radiotherapy treatment planning

    Science.gov (United States)

    Yohannes, Indra; Kolditz, Daniel; Langner, Oliver; Kalender, Willi A.

    2012-03-01

    Tissue- and water-equivalent materials (TEMs) are widely used in quality assurance and calibration procedures, both in radiodiagnostics and radiotherapy. In radiotherapy, particularly, the TEMs are often used for computed tomography (CT) number calibration in treatment planning systems. However, currently available TEMs may not be very accurate in the determination of the calibration curves due to their limitation in mimicking radiation characteristics of the corresponding real tissues in both low- and high-energy ranges. Therefore, we are proposing a new formulation of TEMs using a stoichiometric analysis method to obtain TEMs for the calibration purposes. We combined the stoichiometric calibration and the basic data method to compose base materials to develop TEMs matching standard real tissues from ICRU Report 44 and 46. First, the CT numbers of six materials with known elemental compositions were measured to get constants for the stoichiometric calibration. The results of the stoichiometric calibration were used together with the basic data method to formulate new TEMs. These new TEMs were scanned to validate their CT numbers. The electron density and the stopping power calibration curves were also generated. The absolute differences of the measured CT numbers of the new TEMs were less than 4 HU for the soft tissues and less than 22 HU for the bone compared to the ICRU real tissues. Furthermore, the calculated relative electron density and electron and proton stopping powers of the new TEMs differed by less than 2% from the corresponding ICRU real tissues. The new TEMs which were formulated using the proposed technique increase the simplicity of the calibration process and preserve the accuracy of the stoichiometric calibration simultaneously.

  9. SU-E-J-210: Characterizing Tissue Equivalent Materials for the Development of a Dual MRI-CT Heterogeneous Anthropomorphic Phantom Designed Specifically for MRI Guided Radiotherapy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Steinmann, A; Stafford, R; Yung, J; Followill, D [UT MD Anderson Cancer Center, Houston, TX (United States)

    2015-06-15

    Purpose: MRI guided radiotherapy (MRIgRT) is an emerging technology which will eventually require a proficient quality auditing system. Due to different principles in which MR and CT acquire images, there is a need for a multi-imaging-modality, end-to-end QA phantom for MRIgRT. The purpose of this study is to identify lung, soft tissue, and tumor equivalent substitutes that share similar human-like CT and MR properties (i.e. Hounsfield units and relaxation times). Methods: Materials of interested such as common CT QA phantom materials, and other proprietary gels/silicones from Polytek, SmoothOn, and CompositeOne were first scanned on a GE 1.5T Signa HDxT MR. Materials that could be seen on both T1-weighted and T2-weighted images were then scanned on a GE Lightspeed RT16 CT simulator and a GE Discovery 750HD CT scanner and their HU values were then measured. The materials with matching HU values of lung (−500 to −700HU), muscle (+40HU) and soft tissue (+100 to +300HU) were further scanned on GE 1.5T Signa HDx to measure their T1 and T2 relaxation times from varying parameters of TI and TE. Results: Materials that could be visualized on T1-weighted and T2-weighted images from a 1.5T MR unit and had an appropriate average CT number, −650, −685, 46,169, and 168 HUs were: compressed cork saturated with water, Polytek Platsil™ Gel-00 combined with mini styrofoam balls, radiotherapy bolus material, SmoothOn Dragon-Skin™ and SmoothOn Ecoflex™, respectively. Conclusion: Post processing analysis is currently being performed to accurately map T1 and T2 values for each material tested. From previous MR visualization and CT examinations it is expected that Dragon-Skin™, Ecoflex™ and bolus will have values consistent with tissue and tumor substitutes. We also expect compressed cork statured with water, and Polytek™-styrofoam combination to have approximate T1 and T2 values suitable for lung-equivalent materials.

  10. SU-E-J-210: Characterizing Tissue Equivalent Materials for the Development of a Dual MRI-CT Heterogeneous Anthropomorphic Phantom Designed Specifically for MRI Guided Radiotherapy Systems

    International Nuclear Information System (INIS)

    Steinmann, A; Stafford, R; Yung, J; Followill, D

    2015-01-01

    Purpose: MRI guided radiotherapy (MRIgRT) is an emerging technology which will eventually require a proficient quality auditing system. Due to different principles in which MR and CT acquire images, there is a need for a multi-imaging-modality, end-to-end QA phantom for MRIgRT. The purpose of this study is to identify lung, soft tissue, and tumor equivalent substitutes that share similar human-like CT and MR properties (i.e. Hounsfield units and relaxation times). Methods: Materials of interested such as common CT QA phantom materials, and other proprietary gels/silicones from Polytek, SmoothOn, and CompositeOne were first scanned on a GE 1.5T Signa HDxT MR. Materials that could be seen on both T1-weighted and T2-weighted images were then scanned on a GE Lightspeed RT16 CT simulator and a GE Discovery 750HD CT scanner and their HU values were then measured. The materials with matching HU values of lung (−500 to −700HU), muscle (+40HU) and soft tissue (+100 to +300HU) were further scanned on GE 1.5T Signa HDx to measure their T1 and T2 relaxation times from varying parameters of TI and TE. Results: Materials that could be visualized on T1-weighted and T2-weighted images from a 1.5T MR unit and had an appropriate average CT number, −650, −685, 46,169, and 168 HUs were: compressed cork saturated with water, Polytek Platsil™ Gel-00 combined with mini styrofoam balls, radiotherapy bolus material, SmoothOn Dragon-Skin™ and SmoothOn Ecoflex™, respectively. Conclusion: Post processing analysis is currently being performed to accurately map T1 and T2 values for each material tested. From previous MR visualization and CT examinations it is expected that Dragon-Skin™, Ecoflex™ and bolus will have values consistent with tissue and tumor substitutes. We also expect compressed cork statured with water, and Polytek™-styrofoam combination to have approximate T1 and T2 values suitable for lung-equivalent materials

  11. Neutron dosimetry using proportional counters with tissue equivalent walls

    International Nuclear Information System (INIS)

    Kerviller, H. de

    1965-01-01

    The author reminds the calculation method of the neutron absorbed dose in a material and deduce of it the conditions what this material have to fill to be equivalent to biological tissues. Various proportional counters are mode with walls in new tissue equivalent material and filled with various gases. The multiplication factor and neutron energy response of these counters are investigated and compared with those obtained with ethylene lined polyethylene counters. The conditions of working of such proportional counters for neutron dosimetry in energy range 10 -2 to 15 MeV are specified. (author) [fr

  12. Technical Note: Radiation properties of tissue- and water-equivalent materials formulated using the stoichiometric analysis method in charged particle therapy

    Energy Technology Data Exchange (ETDEWEB)

    Yohannes, Indra; Vasiliniuc, Stefan [Radiation Oncology, University Hospital Erlangen, Erlangen 91054 (Germany); Hild, Sebastian [Faculty of Medicine, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen 91054, Germany and Department of Biophysics, GSI - Helmholtz Centre for Heavy Ion Research, Darmstadt 64291 (Germany); Langner, Oliver [QRM - Quality Assurance in Radiology and Medicine GmbH, Möhrendorf 91096 (Germany); Graeff, Christian [Department of Biophysics, GSI - Helmholtz Centre for Heavy Ion Research, Darmstadt 64291 (Germany); Bert, Christoph, E-mail: christoph.bert@uk-erlangen.de [Radiation Oncology, University Hospital Erlangen, Erlangen 91054 (Germany); Faculty of Medicine, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen 91054 (Germany); Department of Biophysics, GSI - Helmholtz Centre for Heavy Ion Research, Darmstadt 64291 (Germany)

    2016-01-15

    Purpose: Five tissue- and water-equivalent materials (TEMs) mimicking ICRU real tissues have been formulated using a previously established stoichiometric analysis method (SAM) to be applied in charged particle therapy. The purpose of this study was an experimental verification of the TEMs-SAM against charged particle beam measurements and for different computed tomography (CT) scanners. The potential of the TEMs-SAM to be employed in the dosimetry was also investigated. Methods: Experimental verification with three CT scanners was carried out to validate the calculated Hounsfield units (HUs) of the TEMs. Water-equivalent path lengths (WEPLs) of the TEMs for proton (106.8 MeV/u), helium (107.93 MeV/u), and carbon (200.3 MeV/u) ions were measured to be compared with the computed relative stopping powers. HU calibration curves were also generated. Results: Differences between the measured HUs of the TEMs and the calculated HUs of the ICRU real tissues for all CT scanners were smaller than 4 HU except for the skeletal tissues which deviated up to 21 HU. The measured WEPLs verified the calculated WEPLs of the TEMs (maximum deviation was 0.17 mm) and were in good agreement with the calculated WEPLs of the ICRU real tissues (maximum deviation was 0.23 mm). Moreover, the relative stopping powers converted from the measured WEPLs differed less than 0.8% and 1.3% from the calculated values of the SAM and the ICRU, respectively. Regarding the relative nonelastic cross section per unit of volume for 200 MeV protons, the ICRU real tissues were generally well represented by the TEMs except for adipose which differed 3.8%. Further, the HU calibration curves yielded the mean and the standard deviation of the errors not larger than 0.5% and 1.9%, respectively. Conclusions: The results of this investigation implied the potential of the TEMs formulated using the SAM to be employed for both, beam dosimetry and HU calibration in charged particle therapy.

  13. Technical Note: Radiation properties of tissue- and water-equivalent materials formulated using the stoichiometric analysis method in charged particle therapy

    International Nuclear Information System (INIS)

    Yohannes, Indra; Vasiliniuc, Stefan; Hild, Sebastian; Langner, Oliver; Graeff, Christian; Bert, Christoph

    2016-01-01

    Purpose: Five tissue- and water-equivalent materials (TEMs) mimicking ICRU real tissues have been formulated using a previously established stoichiometric analysis method (SAM) to be applied in charged particle therapy. The purpose of this study was an experimental verification of the TEMs-SAM against charged particle beam measurements and for different computed tomography (CT) scanners. The potential of the TEMs-SAM to be employed in the dosimetry was also investigated. Methods: Experimental verification with three CT scanners was carried out to validate the calculated Hounsfield units (HUs) of the TEMs. Water-equivalent path lengths (WEPLs) of the TEMs for proton (106.8 MeV/u), helium (107.93 MeV/u), and carbon (200.3 MeV/u) ions were measured to be compared with the computed relative stopping powers. HU calibration curves were also generated. Results: Differences between the measured HUs of the TEMs and the calculated HUs of the ICRU real tissues for all CT scanners were smaller than 4 HU except for the skeletal tissues which deviated up to 21 HU. The measured WEPLs verified the calculated WEPLs of the TEMs (maximum deviation was 0.17 mm) and were in good agreement with the calculated WEPLs of the ICRU real tissues (maximum deviation was 0.23 mm). Moreover, the relative stopping powers converted from the measured WEPLs differed less than 0.8% and 1.3% from the calculated values of the SAM and the ICRU, respectively. Regarding the relative nonelastic cross section per unit of volume for 200 MeV protons, the ICRU real tissues were generally well represented by the TEMs except for adipose which differed 3.8%. Further, the HU calibration curves yielded the mean and the standard deviation of the errors not larger than 0.5% and 1.9%, respectively. Conclusions: The results of this investigation implied the potential of the TEMs formulated using the SAM to be employed for both, beam dosimetry and HU calibration in charged particle therapy

  14. Technical Note: Radiation properties of tissue- and water-equivalent materials formulated using the stoichiometric analysis method in charged particle therapy.

    Science.gov (United States)

    Yohannes, Indra; Hild, Sebastian; Vasiliniuc, Stefan; Langner, Oliver; Graeff, Christian; Bert, Christoph

    2016-01-01

    Five tissue- and water-equivalent materials (TEMs) mimicking ICRU real tissues have been formulated using a previously established stoichiometric analysis method (SAM) to be applied in charged particle therapy. The purpose of this study was an experimental verification of the TEMs-SAM against charged particle beam measurements and for different computed tomography (CT) scanners. The potential of the TEMs-SAM to be employed in the dosimetry was also investigated. Experimental verification with three CT scanners was carried out to validate the calculated Hounsfield units (HUs) of the TEMs. Water-equivalent path lengths (WEPLs) of the TEMs for proton (106.8 MeV/u), helium (107.93 MeV/u), and carbon (200.3 MeV/u) ions were measured to be compared with the computed relative stopping powers. HU calibration curves were also generated. Differences between the measured HUs of the TEMs and the calculated HUs of the ICRU real tissues for all CT scanners were smaller than 4 HU except for the skeletal tissues which deviated up to 21 HU. The measured WEPLs verified the calculated WEPLs of the TEMs (maximum deviation was 0.17 mm) and were in good agreement with the calculated WEPLs of the ICRU real tissues (maximum deviation was 0.23 mm). Moreover, the relative stopping powers converted from the measured WEPLs differed less than 0.8% and 1.3% from the calculated values of the SAM and the ICRU, respectively. Regarding the relative nonelastic cross section per unit of volume for 200 MeV protons, the ICRU real tissues were generally well represented by the TEMs except for adipose which differed 3.8%. Further, the HU calibration curves yielded the mean and the standard deviation of the errors not larger than 0.5% and 1.9%, respectively. The results of this investigation implied the potential of the TEMs formulated using the SAM to be employed for both, beam dosimetry and HU calibration in charged particle therapy.

  15. Frequency of occurrence of various nuclear reactions when fast neutrons (greater than or equal to 50 MeV) pass through tissue-equivalent material

    International Nuclear Information System (INIS)

    Alsmiller, R.G. Jr.

    1975-07-01

    Calculated results are presented for the frequency with which various partial nuclear-reaction cross sections are utilized when fast neutrons (less than or equal to 50 MeV) are transported through a tissue-equivalent phantom to obtain an indication of which cross sections are of most importance for radiotherapy applications and are therefore in need of experimental verification. (6 tables) (U.S.)

  16. Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material

    International Nuclear Information System (INIS)

    Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

    2013-01-01

    When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5° angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure. (author)

  17. Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material.

    Science.gov (United States)

    Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

    2013-09-01

    When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure.

  18. Critical study of some soft-tissue equivalent material. Sensitivity to neutrons of 1 keV to 14 MeV; Etude critique de quelques materiaux equivalents aux tissus mous. Sensibilite aux neutrons de 1 keV a 14 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Kerviler, H de; Pages, L; Tardy-Joubert, Ph [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    Authors have studied the elastic and inelastic reactions on various elements contribution to kerma in standard soft tissue and as a function of neutron energy from 1 keV to 14 MeV the ratio of kerma in tissue equivalent material to kerma in soft tissue. The results of calculations are made for materials without hydrogen in view to state exactly their neutron sensitivity and for the following hydrogenous materials: Rossi and Failla plastic, MixD, pure polyethylene and a new CEA tissue equivalent (a magnesium fluoride and polyethylene compound). Results for {gamma}-rays are given. (authors) [French] Les auteurs ont etudie la contribution au kerma total des reactions elastiques et inelastiques sur les divers composants du tissu mou standard et la variation, en fonction de l'energie des neutrons de 1 keV a 14 MeV, du rapport des kermas dans differents materiaux equivalents au tissu au kerma dans les tissus mous. Les materiaux etudies sont des materiaux sans hydrogene afin de preciser leur sensibilite aux neutrons et les materiaux hydrogenes suivants: plastique de Rossi et Failla, polyethylene pur, MixD, nouveau plastique CEA a base de polyethylene et de fluorure de magnesium. Les resultats pour les photons sont egalement rappeles. (auteurs)

  19. Tissue Equivalents Based on Cell-Seeded Biodegradable Microfluidic Constructs

    Directory of Open Access Journals (Sweden)

    Sarah L. Tao

    2010-03-01

    Full Text Available One of the principal challenges in the field of tissue engineering and regenerative medicine is the formation of functional microvascular networks capable of sustaining tissue constructs. Complex tissues and vital organs require a means to support oxygen and nutrient transport during the development of constructs both prior to and after host integration, and current approaches have not demonstrated robust solutions to this challenge. Here, we present a technology platform encompassing the design, construction, cell seeding and functional evaluation of tissue equivalents for wound healing and other clinical applications. These tissue equivalents are comprised of biodegradable microfluidic scaffolds lined with microvascular cells and designed to replicate microenvironmental cues necessary to generate and sustain cell populations to replace dermal and/or epidermal tissues lost due to trauma or disease. Initial results demonstrate that these biodegradable microfluidic devices promote cell adherence and support basic cell functions. These systems represent a promising pathway towards highly integrated three-dimensional engineered tissue constructs for a wide range of clinical applications.

  20. Neutron kerma factors, and water equivalence of some tissue substitutes

    International Nuclear Information System (INIS)

    Singh, V. P.; Badiger, N. M.; Vega C, H. R.

    2014-08-01

    The kerma factors and kerma relative to air and water of 24 compounds used as tissue substitutes were calculated for neutron energy from 2.53 x 10 -8 up to 29 MeV. The kerma ratio of the tissue substitutes relative to air and water were calculated by the ratio of kerma factors of the tissue substitute to air and water respectively. The water equivalence of the selected tissue substitutes was observed above neutron energies 100 eV. Kerma ratio relative to the air for Poly-vinylidene fluoride and Teflon are found to be nearest to unity in very low energy (up to 1 eV) and above 63 eV respectively. It was found that the natural rubber as a water equivalent tissue substitute compound. The results of the kerma factors in our investigation shows a very good agreement with those published in ICRU-44. We found that at higher neutron energies, the kerma factors and kerma ratios of the selected tissue substitute compounds are approximately same, but differences are large for energies below 100 eV. (Author)

  1. Evaluation of a tissue equivalent ionization chamber in X-ray beams

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E., E-mail: aperini@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Frimaio, Audrew [Seal Technology Ind. Com. Ltda, Sao Paulo, SP (Brazil); Costa, Paulo R. [Universidade de Sao Paulo (USP/IF), Sao Paulo, SP (Brazil). Inst. de Fisica

    2014-07-01

    Tissue equivalent materials present a variety of uses, including routine quality assurance and quality control programs in both diagnostic and therapeutic physics. They are frequently used in research facilities to measure doses delivered to patients undergoing various clinical procedures. This work presents the development and evaluation of a tissue equivalent ionization chamber, with a sensitive volume of 2.3 cm{sup 3}, for routine use in X-rays beams. This ionization chamber was developed at the Calibration Laboratory/IPEN. The new tissue equivalent material was developed at the Physics Institute of the University of Sao Paulo. In order to evaluate the dosimetric performance of the new ionization chamber, several tests described by international standards were undertaken, and all results were within the recommended limits. (author)

  2. Evaluation of a tissue equivalent ionization chamber in X-ray beams

    International Nuclear Information System (INIS)

    Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E.; Frimaio, Audrew; Costa, Paulo R.

    2014-01-01

    Tissue equivalent materials present a variety of uses, including routine quality assurance and quality control programs in both diagnostic and therapeutic physics. They are frequently used in research facilities to measure doses delivered to patients undergoing various clinical procedures. This work presents the development and evaluation of a tissue equivalent ionization chamber, with a sensitive volume of 2.3 cm 3 , for routine use in X-rays beams. This ionization chamber was developed at the Calibration Laboratory/IPEN. The new tissue equivalent material was developed at the Physics Institute of the University of Sao Paulo. In order to evaluate the dosimetric performance of the new ionization chamber, several tests described by international standards were undertaken, and all results were within the recommended limits. (author)

  3. Development of solid water-equivalent radioactive certified reference materials

    International Nuclear Information System (INIS)

    Finke, E.; Greupner, H.; Groche, K.; Rittwag, R.; Geske, G.

    1991-01-01

    This paper presents a brief description of the development of solid water-equivalent beta volume radioactive certified reference materials. These certified reference materials were prepared for the beta fission nuclides 90 Sr/ 90 Y, 137 Cs, 147 Pm and 204 Tl. Comparative measurements of liquid and solid water-equivalent beta volume radioactive certified reference materials are discussed. (author)

  4. Composition of MRI phantom equivalent to human tissues

    International Nuclear Information System (INIS)

    Kato, Hirokazu; Kuroda, Masahiro; Yoshimura, Koichi; Yoshida, Atsushi; Hanamoto, Katsumi; Kawasaki, Shoji; Shibuya, Koichi; Kanazawa, Susumu

    2005-01-01

    We previously developed two new MRI phantoms (called the CAG phantom and the CAGN phantom), with T1 and T2 relaxation times equivalent to those of any human tissue at 1.5 T. The conductivity of the CAGN phantom is equivalent to that of most types of human tissue in the frequency range of 1 to 130 MHz. In this paper, the relaxation times of human tissues are summarized, and the composition of the corresponding phantoms are provided in table form. The ingredients of these phantoms are carrageenan as the gelling agent, GdCl 3 as a T1 modifier, agarose as a T2 modifier, NaCl (CAGN phantom only) as a conductivity modifier, NaN 3 as an antiseptic, and distilled water. The phantoms have T1 values of 202-1904 ms and T2 values of 38-423 ms when the concentrations of GdCl 3 and agarose are varied from 0-140 μmol/kg, and 0%-1.6%, respectively, and the CAGN phantom has a conductivity of 0.27-1.26 S/m when the NaCl concentration is varied from 0%-0.7%. These phantoms have sufficient strength to replicate a torso without the use of reinforcing agents, and can be cut by a knife into any shape. We anticipate the CAGN phantom to be highly useful and practical for MRI and hyperthermia-related research

  5. Development of solid water-equivalent radioactive certified reference materials

    Energy Technology Data Exchange (ETDEWEB)

    Finke, E.; Greupner, H.; Groche, K.; Rittwag, R. (Office for Standardization, Metrology and Quality Control (ASMW), Berlin (Germany, F.R.)); Geske, G. (Jena Univ. (Germany, F.R.))

    1991-01-01

    This paper presents a brief description of the development of solid water-equivalent beta volume radioactive certified reference materials. These certified reference materials were prepared for the beta fission nuclides {sup 90}Sr/{sup 90}Y, {sup 137}Cs, {sup 147}Pm and {sup 204}Tl. Comparative measurements of liquid and solid water-equivalent beta volume radioactive certified reference materials are discussed. (author).

  6. Tissue Equivalent Phantom Design for Characterization of a Coherent Scatter X-ray Imaging System

    Science.gov (United States)

    Albanese, Kathryn Elizabeth

    Scatter in medical imaging is typically cast off as image-related noise that detracts from meaningful diagnosis. It is therefore typically rejected or removed from medical images. However, it has been found that every material, including cancerous tissue, has a unique X-ray coherent scatter signature that can be used to identify the material or tissue. Such scatter-based tissue-identification provides the advantage of locating and identifying particular materials over conventional anatomical imaging through X-ray radiography. A coded aperture X-ray coherent scatter spectral imaging system has been developed in our group to classify different tissue types based on their unique scatter signatures. Previous experiments using our prototype have demonstrated that the depth-resolved coherent scatter spectral imaging system (CACSSI) can discriminate healthy and cancerous tissue present in the path of a non-destructive x-ray beam. A key to the successful optimization of CACSSI as a clinical imaging method is to obtain anatomically accurate phantoms of the human body. This thesis describes the development and fabrication of 3D printed anatomical scatter phantoms of the breast and lung. The purpose of this work is to accurately model different breast geometries using a tissue equivalent phantom, and to classify these tissues in a coherent x-ray scatter imaging system. Tissue-equivalent anatomical phantoms were designed to assess the capability of the CACSSI system to classify different types of breast tissue (adipose, fibroglandular, malignant). These phantoms were 3D printed based on DICOM data obtained from CT scans of prone breasts. The phantoms were tested through comparison of measured scatter signatures with those of adipose and fibroglandular tissue from literature. Tumors in the phantom were modeled using a variety of biological tissue including actual surgically excised benign and malignant tissue specimens. Lung based phantoms have also been printed for future

  7. The materials used in bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Tereshchenko, V. P., E-mail: tervp@ngs.ru; Kirilova, I. A.; Sadovoy, M. A.; Larionov, P. M. [Novosibirsk Research Institute of Traumatology and Orthopedics n.a. Ya.L. Tsivyan, Novosibirsk (Russian Federation)

    2015-11-17

    Bone tissue engineering looking for an alternative solution to the problem of skeletal injuries. The method is based on the creation of tissue engineered bone tissue equivalent with stem cells, osteogenic factors, and scaffolds - the carriers of these cells. For production of tissue engineered bone equivalent is advisable to create scaffolds similar in composition to natural extracellular matrix of the bone. This will provide optimal conditions for the cells, and produce favorable physico-mechanical properties of the final construction. This review article gives an analysis of the most promising materials for the manufacture of cell scaffolds. Biodegradable synthetic polymers are the basis for the scaffold, but it alone cannot provide adequate physical and mechanical properties of the construction, and favorable conditions for the cells. Addition of natural polymers improves the strength characteristics and bioactivity of constructions. Of the inorganic compounds, to create cell scaffolds the most widely used calcium phosphates, which give the structure adequate stiffness and significantly increase its osteoinductive capacity. Signaling molecules do not affect the physico-mechanical properties of the scaffold, but beneficial effect is on the processes of adhesion, proliferation and differentiation of cells. Biodegradation of the materials will help to fulfill the main task of bone tissue engineering - the ability to replace synthetic construct by natural tissues that will restore the original anatomical integrity of the bone.

  8. New technique for tissue-equivalent gamma ray dosimetry

    International Nuclear Information System (INIS)

    Squillante, M.R.; Stern, I.; Nagarkar, V.; Entine, G.

    1992-01-01

    The use of semiconductor sensors in dosimeters is attractive for a variety of reasons including potential low cost and high sensitivity. However, the accurate measurement of the radiation dose to tissue using solid state detectors is made difficult by the relatively high atomic number of semiconductor materials. This leads to an over response to gamma ray energies below 100 keV and an under response above that. If the energy spectrum is known, corrections can be applied to yield accurate dose. In real life situations, however, the energy spectrum is not always known and may be difficult to determine at high flux rates. Also, in some cases, the energy spectrum may change with time. This paper reports that, by operating a custom-designed CdTe sensor in the pulse mode and measuring the average energy deposited, a nearly-linear relationship between the tissue dose rate and the sensor signal was obtained. Based on this technique, a prototype detector and dosimeter system were developed

  9. Microcystin-LR equivalent concentrations in fish tissue during a ...

    African Journals Online (AJOL)

    The effects of a decomposing cyanobacteria bloom on water quality and the accumulation of microcystin-LR equivalent toxin in fish at Loskop Dam were studied in May 2012. Enzyme-linked immunosorbent assay [ELISA] was used to confirm the presence of microcystin-LR equivalent in the water and to determine the ...

  10. The performance of low pressure tissue-equivalent chambers and a new method for parameterising the dose equivalent

    International Nuclear Information System (INIS)

    Eisen, Y.

    1986-01-01

    The performance of Rossi-type spherical tissue-equivalent chambers with equivalent diameters between 0.5 μm and 2 μm was tested experimentally using monoenergetic and polyenergetic neutron sources in the energy region of 10 keV to 14.5 MeV. In agreement with theoretical predictions both chambers failed to provide LET information at low neutron energies. A dose equivalent algorithm was derived that utilises the event distribution but does not attempt to correlate event size with LET. The algorithm was predicted theoretically and confirmed by experiment. The algorithm that was developed determines the neutron dose equivalent, from the data of the 0.5 μm chamber, to better than +-20% over the energy range of 30 keV to 14.5 MeV. The same algorithm also determines the dose equivalent from the data of the 2 μm chamber to better than +-20% over the energy range of 60 keV to 14.5 MeV. The efficiency of the chambers is 33 counts per μSv, or equivalently about 10 counts s -1 per mSv.h -1 . This efficiency enables the measurement of dose equivalent rates above 1 mSv.h -1 for an integration period of 3 s. Integrated dose equivalents can be measured as low as 1 μSv. (author)

  11. Neutron measurements with a tissue-equivalent phantom

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J W [Health Physics Division, Atomic Energy Establishment, Harwell (United Kingdom)

    1962-03-15

    This Appendix 3E of the dosimetry experiment at the R-B reactor describes the apparatus used and presents the obtained results. The phantom used was a 1/4-inch thick polythene container, 60 cm high, of elliptical cross-section, with a major axis of 36 cm and a minor axis of 20 cm. This was filled with an approximately tissue-equivalent liquid. A light but rigid internal framework of Perspex supported a series of small detectors through the phantom. The detectors used in the first high-level run at Vinca, to measure flux above 0.5 MeV, were 0.5-cm wide track plates wrapped in cadmium foil. Each track plate was a sandwich of two Ilford El 50 - mu emulsions, with glass backing, separated by a 250-mu polythene radiator, and was oriented at an angle of 45 deg to the front surface of the phantom. Under these conditions the response is constant with neutron energy between 0.5 MeV and 8 MeV at 1.26 X 10 sup - sup 3 tracks/neutron to within +- 15%. The detectors used in the second high-level run were gold foils (260 mg/cm sup 2 thick) for determination of the show neutron distribution. Previous experiments with 0.13 MeV, 2.5 MeV, 14 MeV and Po-Be neutrons have shown that the shape of the curve through a phantom obtained from these gold foils is the same as that given by either manganese foils or sodium samples despite the difference in resonance integrals. From the relaxation length of the neutron flux in the phantom, as measured by the track plates, the mean energy of the neutrons with energies greater than 0.5 MeV may be found by comparison with the relaxation lengths obtained by irradiation of the phantom with monoenergetic neutrons. The results of these experiments are given. Track plate results from the Vinca experiment are shown. It can be seen that the backscattered fast flux is about one-third of the incident fast flux and that the energy indicated by the shape of the curve is considerably lower than the energy of the direct neutrons. It seems possible that the high

  12. Neutron measurements with a tissue-equivalent phantom

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J W [Health Physics Division, Atomic Energy Establishment, Harwell (United Kingdom)

    1962-03-01

    This Appendix 3E of the dosimetry experiment at the R-B reactor describes the apparatus used and presents the obtained results. The phantom used was a 1/4-inch thick polythene container, 60 cm high, of elliptical cross-section, with a major axis of 36 cm and a minor axis of 20 cm. This was filled with an approximately tissue-equivalent liquid. A light but rigid internal framework of Perspex supported a series of small detectors through the phantom. The detectors used in the first high-level run at Vinca, to measure flux above 0.5 MeV, were 0.5-cm wide track plates wrapped in cadmium foil. Each track plate was a sandwich of two Ilford El 50 - {mu} emulsions, with glass backing, separated by a 250-{mu} polythene radiator, and was oriented at an angle of 45 deg to the front surface of the phantom. Under these conditions the response is constant with neutron energy between 0.5 MeV and 8 MeV at 1.26 X 10{sup -3} tracks/neutron to within {+-} 15%. The detectors used in the second high-level run were gold foils (260 mg/cm{sup 2} thick) for determination of the show neutron distribution. Previous experiments with 0.13 MeV, 2.5 MeV, 14 MeV and Po-Be neutrons have shown that the shape of the curve through a phantom obtained from these gold foils is the same as that given by either manganese foils or sodium samples despite the difference in resonance integrals. From the relaxation length of the neutron flux in the phantom, as measured by the track plates, the mean energy of the neutrons with energies greater than 0.5 MeV may be found by comparison with the relaxation lengths obtained by irradiation of the phantom with monoenergetic neutrons. The results of these experiments are given. Track plate results from the Vinca experiment are shown. It can be seen that the backscattered fast flux is about one-third of the incident fast flux and that the energy indicated by the shape of the curve is considerably lower than the energy of the direct neutrons. It seems possible that the

  13. Radicals formation in the PVC/DOP plastisol radiolysis used as equivalent-tissue in radiotherapy

    International Nuclear Information System (INIS)

    Pezzin, A.P.T.; Salman, K.D.; Mei, L.H.I.

    1997-01-01

    Recently, a tissue simulator called bolus was developed at FEQ/UNICAMP, which is made of dioctyl phthalate and poly (vinyl chloride) (DOC/PVC). This bolus has the function of displacing the maximum dose the skin surface in radiation therapy of skin and breast cancer. In this way the healthy tissues around the tumor are protected. Research at the Center for Women's Health (CAISM) of the Clinical Hospital of UNICAMP has shown that this material can be used as the tissue-equivalent of skin. In the present work, bolus samples were irradiated by gamma rays and the radicals formed were investigated by electron paramagnetic resonance at 110K. The results showed the radicals formation as a consequence of the homolytic scissions of the chemical bonds of DOP and the air presence interfere in the quantity of observed paramagnetic species. (author)

  14. Construction of a self-supporting tissue-equivalent dividing wall and operational characteristics of a coaxial double-cylindrical tissue-equivalent proportional counter

    International Nuclear Information System (INIS)

    Saion, E.B.; Watt, D.E.

    1994-01-01

    An additional feature incorporated in a coaxial double-cylindrical tissue-equivalent proportional counter, is the presence of a common tissue-equivalent dividing wall between the inner and outer counters of thickness equivalent to the corresponding maximum range of protons at the energy of interest. By appropriate use of an anti-coincidence arrangement with the outer counter, the inner counter could be used to discriminate microdosimetric spectra of neutrons at the desired low energy range from those of the faster neutrons. The construction of an A-150 self-supporting tissue-equivalent dividing wall and an anti-coincidence unit are described. Some operational characteristic tests have been performed to determine the operation of the new microdosimeter. (author)

  15. MCNP modelling of the wall effects observed in tissue-equivalent proportional counters.

    Science.gov (United States)

    Hoff, J L; Townsend, L W

    2002-01-01

    Tissue-equivalent proportional counters (TEPCs) utilise tissue-equivalent materials to depict homogeneous microscopic volumes of human tissue. Although both the walls and gas simulate the same medium, they respond to radiation differently. Density differences between the two materials cause distortions, or wall effects, in measurements, with the most dominant effect caused by delta rays. This study uses a Monte Carlo transport code, MCNP, to simulate the transport of secondary electrons within a TEPC. The Rudd model, a singly differential cross section with no dependence on electron direction, is used to describe the energy spectrum obtained by the impact of two iron beams on water. Based on the models used in this study, a wall-less TEPC had a higher lineal energy (keV.micron-1) as a function of impact parameter than a solid-wall TEPC for the iron beams under consideration. An important conclusion of this study is that MCNP has the ability to model the wall effects observed in TEPCs.

  16. Analysis of biological tissues in infant chest for the development of an equivalent radiographic phantom

    International Nuclear Information System (INIS)

    Pina, D. R.; Souza, Rafael T. F.; Duarte, Sergio B.; Alvarez, Matheus; Miranda, Jose R. A.

    2012-01-01

    Purpose: The main purpose of the present study was to determine the amounts of different tissues in the chest of the newborn patient (age ≤1 year), with the aim of developing a homogeneous phantom chest equivalent. This type of phantom is indispensable in the development of optimization procedures for radiographic techniques, including dosimetric control, which is a crucial aspect of pediatric radiology. The authors present a systematic set of procedures, including a computational algorithm, to estimate the amounts of tissues and thicknesses of the corresponding simulator material plates used to construct the phantom. Methods: The Gaussian fit of computed tomographic (CT) analysis was applied to classify and quantify different biological tissues. The methodology is summarized with a computational algorithm, which was used to quantify tissues through automated CT analysis. The thicknesses of the equivalent homogeneous simulator material plates were determined to construct the phantom. Results: A total of 180 retrospective CT examinations with anterior-posterior diameter values ranging 8.5-13.0 cm were examined. The amounts of different tissues were evaluated. The results provided elements to construct a phantom to simulate the infant chest in the posterior-anterior or anterior-posterior (PA/AP) view. Conclusions: To our knowledge, this report represents the first demonstration of an infant chest phantom dedicated to the radiology of children younger than one year. This phantom is a key element in the development of clinical charts for optimizing radiographic technique in pediatric patients. Optimization procedures for nonstandard patients were reported previously [Pina et al., Phys. Med. Biol. 49, N215-N226 (2004) and Pina et al., Appl. Radiat. Isot. 67, 61-69 (2009)]. The constructed phantom represents a starting point to obtain radiologic protocols for the infant patient.

  17. Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities

    International Nuclear Information System (INIS)

    Langen, K M; Binns, P J; Schreuder, A N; Lennox, A J; Deluca, P M Jr.

    2003-01-01

    The ICRU tissue to A-150 tissue equivalent plastic kerma ratio is needed for neutron therapy dosimetry. The current ICRU protocol for neutron dosimetry recommends using a common conversion factor of 0.95 at all high-energy neutron therapy facilities. In an effort to determine facility specific ICRU tissue to A-150 plastic kerma ratios, an experimental approach was pursued. Four low pressure proportional counters that differed in wall materials (i.e. A-150, carbon, zirconium and zirconium-oxide) were used as dosimeters and integral kerma ratios were determined directly in the clinical beam. Measurements were performed at two p(66)Be facilities: iThemba LABS near Cape Town and Fermilab near Chicago. At the iThemba facility the clinical neutron beam is routinely filtered by a flattening and hardening filter combination. The influence of beam filtration on the kerma ratio was evaluated. Using two recent gas-to-wall dose conversion factor (r m,g value) evaluations a mean ICRU tissue to A-150 plastic kerma ratio of 0.93 ± 0.05 was determined for the clinical beam at iThemba LABS. The respective value for the Fermilab beam is 0.95 ± 0.05. The experimentally determined ICRU tissue to A-150 plastic kerma ratios for the two clinical beams are in agreement with theoretical evaluations. Beam filtration reduces the kerma ratio by 3 ± 2%

  18. Joint use of developed collagen-containing complexes and cell cultures in creating new tissue equivalents

    Directory of Open Access Journals (Sweden)

    K. V. Kulakova

    2016-01-01

    Full Text Available The purpose of the study is to assess the possibility of applying the integrated module as the basis of a celltissue equivalent for treatment of wounds of skin and soft tissues. In the frame of the set task the following problems were being solved: research of the spatial structure and architectonics of the surface of the developed base collagen-containing materials and their biocompatibility with cell cultures.Materials and methods. The study of a material which is a two-layer complex film, consisting of collagen and polysaccharide components was carried out. The collagen was separated from the dermis and was then impregnated with particulate demineralized bone matrix (DCM according to the original methodology. For the purposes of the study the dehydrated material was created in the form of a film. Electron microscopic examination of surfaces was performed on scanning electron microscope JEOL JSM-IT300LV in high vacuum and at low values of probe current (< 0,1 nА. Studies to assess the viability of the cells cultivated on films of collagen material (tested for cytotoxicity and the adhesive capacity were performed in vitro using strains of diploid human fibroblasts 4–6 passage. The culture condition was visually assessed using an inverted Leica microscope DM IL (Carl Zeiss, Austria, equipped with a computerizes program of control of culture growth (Leica IM 1000.Results. The data obtained in the study of the surface structure of the developed complex module showed that it seems to be promising as a basic component of the cellular-tissue system with its large number of structural formations for fixation of the cells and a well-organized barrier layer capable of vapor - permeability. Experiments in vitro confirmed the absence of toxicity of the material being studied in relation to the culture of dermal human fibroblasts, suggesting the possibility of creation on its basis of cell-tissue complex and further experimental studies in vivo

  19. Study on the neutron dosimetric characteristics of Tissue Equivalent Proportional Counter

    Energy Technology Data Exchange (ETDEWEB)

    Nunomiya, T.; Kim, E.; Kurosawa, T.; Taniguchi, S.; Nakamura, T. [Tohoku Univ., Sendai (Japan). Cyclotron and Radioisotope Center; Tsujimura, N.; Momose, T.; Shinohara, K. [Japan Nuclear Cycle Development Inst., Environment and Safety Division, Tokai Works, Tokai, Ibaraki (Japan)

    1999-03-01

    The neutron dosimetric characteristics of TEPC (Tissue Equivalent Proportional Counter) has been investigated under a cooperative study between Tohoku University and JNC since 1997. This TEPC is a spherical, large volume, single-wire proportional counter (the model LETSW-5, manufactured by Far West Technology, Inc.) and filled with a tissue equivalent gas in a spherical detector of the A-150 tissue equivalent plastic. The TEPC can measure the spectra of absorbed dose in LET and easily estimate the tissue equivalent dose to neutron. This report summarizes the dosimetric characteristics of TEPC to the monoenergetic neutrons with energy from 8 keV to 15 MeV. It is found that TEPC can estimate the ambient dose equivalent, H*(10), with an accuracy from 0.9 to 2 to the neutron above 0.25 MeV and TEPC has a good counting efficiency enough to measure neutron doses with low dose rate at the stray neutron fields. (author)

  20. Ignition Delay of Combustible Materials in Normoxic Equivalent Environments

    Science.gov (United States)

    McAllister, Sara; Fernandez-Pello, Carlos; Ruff, Gary; Urban, David

    2009-01-01

    Material flammability is an important factor in determining the pressure and composition (fraction of oxygen and nitrogen) of the atmosphere in the habitable volume of exploration vehicles and habitats. The method chosen in this work to quantify the flammability of a material is by its ease of ignition. The ignition delay time was defined as the time it takes a combustible material to ignite after it has been exposed to an external heat flux. Previous work in the Forced Ignition and Spread Test (FIST) apparatus has shown that the ignition delay in the currently proposed space exploration atmosphere (approximately 58.6 kPa and32% oxygen concentration) is reduced by 27% compared to the standard atmosphere used in the Space Shuttle and Space Station. In order to determine whether there is a safer environment in terms of material flammability, a series of piloted ignition delay tests using polymethylmethacrylate (PMMA) was conducted in the FIST apparatus to extend the work over a range of possible exploration atmospheres. The exploration atmospheres considered were the normoxic equivalents, i.e. reduced pressure conditions with a constant partial pressure of oxygen. The ignition delay time was seen to decrease as the pressure was reduced along the normoxic curve. The minimum ignition delay observed in the normoxic equivalent environments was nearly 30% lower than in standard atmospheric conditions. The ignition delay in the proposed exploration atmosphere is only slightly larger than this minimum. Interms of material flammability, normoxic environments with a higher pressure relative to the proposed pressure would be desired.

  1. Operation and application of tissue-equivalent proportional counters

    International Nuclear Information System (INIS)

    Gerdung, S.; Roos, H.

    1995-01-01

    The application of TEPCs during the past decades in dosimetry, radiation protection and radiation therapy has revealed their large potential but also the necessity of careful operation. This paper reviews the experience gathered in the past and summarises the experimental procedures to ensure proper TEPC operation. The measurement system is described including detector, electronics and quality assurance. The pulse height analysis and its interpretation in terms of microdosimetric spectra and mean values are presented as well as the variance method. On the basis of these evaluation procedures, the second part of the paper presents some typical examples of TEPC applications: dose spectrometry, time-of-flight techniques and the measurement of dose equivalent quantities. Special attention is paid to possible extensions but also to limitations of the use of TEPCs in the various fields of application. (Author)

  2. Specification and tests of three prototypes from tissue-equivalent ionization chamber

    International Nuclear Information System (INIS)

    Teixeira, D.L.; Cardoso, D.O.; Pereira, O.S.; Nobre Filho, L.S.; Cabral, T.S.

    1992-01-01

    Three prototypes of tissue-equivalent ionization chamber are specified and tested. The results obtained by these prototypes are presented, aiming the determination of operation parameters, defined by IEC 395 standard. (C.G.C.)

  3. Characterization of tissues equivalent to the human body by the Monte Carlo method for X-rays

    International Nuclear Information System (INIS)

    Vega R, J.; Huamani T, Y.; Mullisaca P, A. F.; Yauri C, L.

    2017-10-01

    There is a need to have materials equivalent to the human body that have the appropriate characteristics to be used as a substitute tissue in the clinical practices of radio-diagnosis, radiotherapy. In Arequipa, Peru, there are two health centers in radiotherapy applications, one with a Theratron Co-60 gamma irradiator and another with Elekta Linac; the Medical Physics Area of the School of Physics of the National University of San Agustin de Arequipa, were four equivalent materials based on epoxy resin, phenolitic spheres, calcium carbonate, etc. were built, such as bone tissue, soft tissue, adipose and lung tissue compared with water, whit the purpose of studying and applying them in future clinical applications. In this work we describe its physical and dosimetric characterization to determine its use as an equivalent material or manikin. The materials are 1 cm thick and 30 cm in diameter, the materials are non-malleable solids, they do not degrade, they have stability in their consistency due to temperature and irradiation, they are not toxic in their use, determining densities from 0.32 g/cm 3 for the lung tissue to 1.8 g/cm 3 for the bone material. These materials were analyzed by scanning electron microscopy, giving the percentages by weight of the elements found to determine their effective atomic number, the physical analysis to determine their mass absorption and energy coefficients, which were studied for energy photons between 1 KeV at 20 MeV. The simulation of the equivalent materials and the physical and dosimetric study were found using the code Penelope 2008 Monte Carlo method and validated by the Nist database. The results obtained according to their coefficients of mass attenuation of each material, show lung, bone, soft and adipose tissue with differences with respect to the same Nist materials. The range maximum and minimum Rd deviation found was 35.65 - 3.16 for bone, 28.5 - 6.74 for lung, 33.78 - 9.06 for soft tissue and 86.42 - 1.28 for

  4. TH-AB-209-12: Tissue Equivalent Phantom with Excised Human Tissue for Assessing Clinical Capabilities of Coherent Scatter Imaging Applications

    Energy Technology Data Exchange (ETDEWEB)

    Albanese, K; Morris, R; Spencer, J [Medical Physics Graduate Program, Duke University, Durham, NC (United States); Greenberg, J [Dept. of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Kapadia, A [Carl E Ravin Advanced Imaging Laboratories, Durham, NC (United States)

    2016-06-15

    Purpose: Previously we reported the development of anthropomorphic tissue-equivalent scatter phantoms of the human breast. Here we present the first results from the scatter imaging of the tissue equivalent breast phantoms for breast cancer diagnosis. Methods: A breast phantom was designed to assess the capability of coded aperture coherent x-ray scatter imaging to classify different types of breast tissue (adipose, fibroglandular, tumor). The phantom geometry was obtained from a prone breast geometry scanned on a dedicated breast CT system. The phantom was 3D printed using the segmented DICOM breast CT data. The 3D breast phantom was filled with lard (as a surrogate for adipose tissue) and scanned in different geometries alongside excised human breast tissues (obtained from lumpectomy and mastectomy procedures). The raw data were reconstructed using a model-based reconstruction algorithm and yielded the location and form factor (i.e., momentum transfer (q) spectrum) of the materials that were imaged. The measured material form factors were then compared to the ground truth measurements acquired by x-ray diffraction (XRD) imaging. Results: Our scatter imaging system was able to define the location and composition of the various materials and tissues within the phantom. Cancerous breast tissue was detected and classified through automated spectral matching and an 86% correlation threshold. The total scan time for the sample was approximately 10 minutes and approaches workflow times for clinical use in intra-operative or other diagnostic tasks. Conclusion: This work demonstrates the first results from an anthropomorphic tissue equivalent scatter phantom to characterize a coherent scatter imaging system. The functionality of the system shows promise in applications such as intra-operative margin detection or virtual biopsy in the diagnosis of breast cancer. Future work includes using additional patient-derived tissues (e.g., human fat), and modeling additional organs

  5. Tissue equivalent detector measurements on Mir space station. Comparison with other data

    Energy Technology Data Exchange (ETDEWEB)

    Bottollier-Depois, J.F. [CEA Centre d`Etudes de Fontenay-aux-Roses, 92 (France). Dept. de Protection de la Sante de l`Homme et de Dosimetrie; Siegrist, M. [Centre National d`Etudes Spatiales (CNES), 31 - Toulouse (France); Duvivier, E.; Almarcha, B. [STEEL Technologies, Mazeres sur Salat (France); Dachev, T.P.; Semkova, J.V. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Central Lab. of Solar Energy and New Energy Sources; Petrov, V.M.; Bengin, V.; Koslova, S.B. [Institute of Biomedical Problems, Moscow (Russian Federation)

    1995-12-31

    The measurement of the dose received by the cosmonauts, due to cosmic radiations, during a space mission is an important parameter to estimate the radiological risk. Tissue equivalent measurements of radiation environment inside the MIR space station were performed continuously since July 1992. Interesting results about radiation measurements show (a) the South Atlantic Anomaly (SAA) crossing, (c) the increase of radiation near the poles and (d) the effects of solar eruptions. These data are compared with solid state detector (SSD) and other tissue equivalent proportional counter (TEPC) results. (authors). 4 refs., 7 figs.

  6. Tissue equivalent detector measurements on Mir space station. Comparison with other data

    International Nuclear Information System (INIS)

    Bottollier-Depois, J.F.; Duvivier, E.; Almarcha, B.; Dachev, T.P.; Semkova, J.V.

    1995-01-01

    The measurement of the dose received by the cosmonauts, due to cosmic radiations, during a space mission is an important parameter to estimate the radiological risk. Tissue equivalent measurements of radiation environment inside the MIR space station were performed continuously since July 1992. Interesting results about radiation measurements show (a) the South Atlantic Anomaly (SAA) crossing, (c) the increase of radiation near the poles and (d) the effects of solar eruptions. These data are compared with solid state detector (SSD) and other tissue equivalent proportional counter (TEPC) results. (authors). 4 refs., 7 figs

  7. Equivalence between short-time biphasic and incompressible elastic material responses.

    Science.gov (United States)

    Ateshian, Gerard A; Ellis, Benjamin J; Weiss, Jeffrey A

    2007-06-01

    Porous-permeable tissues have often been modeled using porous media theories such as the biphasic theory. This study examines the equivalence of the short-time biphasic and incompressible elastic responses for arbitrary deformations and constitutive relations from first principles. This equivalence is illustrated in problems of unconfined compression of a disk, and of articular contact under finite deformation, using two different constitutive relations for the solid matrix of cartilage, one of which accounts for the large disparity observed between the tensile and compressive moduli in this tissue. Demonstrating this equivalence under general conditions provides a rationale for using available finite element codes for incompressible elastic materials as a practical substitute for biphasic analyses, so long as only the short-time biphasic response is sought. In practice, an incompressible elastic analysis is representative of a biphasic analysis over the short-term response deltatelasticity tensor, and K is the hydraulic permeability tensor of the solid matrix. Certain notes of caution are provided with regard to implementation issues, particularly when finite element formulations of incompressible elasticity employ an uncoupled strain energy function consisting of additive deviatoric and volumetric components.

  8. Open-air ionisation chambers with walls of soft-tissue equivalent material for measuring photon doses; Chambres d'ionisation d'ambiance a parois en materiau equivalent aux tissus mous pour la mesure des doses absorbees dues aux photons

    Energy Technology Data Exchange (ETDEWEB)

    Vialettes, H.; Anceau, J.C.; Grand, M.; Petit, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    The ionisation chambers presented in this report constitute a contribution to research into methods of carrying out correct determinations in the field of health physics. The use of a mixture of teflon containing 42.5 per cent by weight of carbon for the chamber walls makes it possible to measure directly the dose absorbed in air through 300 mg/cm{sup 2} of soft tissue and, consequently, the dose absorbed in the soft tissues with a maximum error of 10 per cent for photon energies of between 10 keV and 10 MeV. Furthermore since this material does not contain hydrogen, the chamber has a sensitivity to neutrons which is much less than other chambers in current use. Finally the shape of these chambers has been studied with a view to obtaining a satisfactory measurement from the isotropy point of view; for example for gamma radiation of 27 keV, the 3 litre chamber is isotropic to within 10 per cent over 270 degrees, and the 12 litre chamber is isotropic to within 10 per cent over 300 degrees; for 1.25 MeV gamma radiation this range is extended over 330 degrees for the 3 litre chamber, and 360 degrees for the 12 litre chamber. This report presents the measurements carried out with these chambers as well as the results obtained. These results are then compared to those obtained with other chambers currently used in the field of health physics. (authors) [French] Les chambres d'ionisation presentees dans ce rapport apportent une contribution a la recherche de moyens dosimetriques adaptes aux mesures a effectuer pour assurer une dosimetrie correcte dans le domaine de la radioprotection. L'utilisation d'un melange de teflon charge a 42.5 pour cent en masse de carbone comme materiau constituant les parois de la chambre permet de realiser un dosimetre mesurant directement la dose absorbee dans l'air sous 3OO mg/cm{sup 2} de tissu mou et, par consequent, la dose absorbee dans les tissus mous avec une erreur maximale de 10 pour cent, pour des photons d

  9. Calculation of dose distribution for 252Cf fission neutron source in tissue equivalent phantoms using Monte Carlo method

    International Nuclear Information System (INIS)

    Ji Gang; Guo Yong; Luo Yisheng; Zhang Wenzhong

    2001-01-01

    Objective: To provide useful parameters for neutron radiotherapy, the author presents results of a Monte Carlo simulation study investigating the dosimetric characteristics of linear 252 Cf fission neutron sources. Methods: A 252 Cf fission source and tissue equivalent phantom were modeled. The dose of neutron and gamma radiations were calculated using Monte Carlo Code. Results: The dose of neutron and gamma at several positions for 252 Cf in the phantom made of equivalent materials to water, blood, muscle, skin, bone and lung were calculated. Conclusion: The results by Monte Carlo methods were compared with the data by measurement and references. According to the calculation, the method using water phantom to simulate local tissues such as muscle, blood and skin is reasonable for the calculation and measurements of dose distribution for 252 Cf

  10. Bio-fabrication and physiological self-release of tissue equivalents using smart peptide amphiphile templates.

    Science.gov (United States)

    Gouveia, Ricardo M; Hamley, Ian W; Connon, Che J

    2015-10-01

    In this study we applied a smart biomaterial formed from a self-assembling, multi-functional synthetic peptide amphiphile (PA) to coat substrates with various surface chemistries. The combination of PA coating and alignment-inducing functionalised substrates provided a template to instruct human corneal stromal fibroblasts to adhere, become aligned and then bio-fabricate a highly-ordered, multi-layered, three-dimensional tissue by depositing an aligned, native-like extracellular matrix. The newly-formed corneal tissue equivalent was subsequently able to eliminate the adhesive properties of the template and govern its own complete release via the action of endogenous proteases. Tissues recovered through this method were structurally stable, easily handled, and carrier-free. Furthermore, topographical and mechanical analysis by atomic force microscopy showed that tissue equivalents formed on the alignment-inducing PA template had highly-ordered, compact collagen deposition, with a two-fold higher elastic modulus compared to the less compact tissues produced on the non-alignment template, the PA-coated glass. We suggest that this technology represents a new paradigm in tissue engineering and regenerative medicine, whereby all processes for the bio-fabrication and subsequent self-release of natural, bio-prosthetic human tissues depend solely on simple template-tissue feedback interactions.

  11. Equivalent viscous damping procedure for multi-material systems

    International Nuclear Information System (INIS)

    Ahmed, H.; Ma, D.

    1979-01-01

    The inclusion of accurate viscous damping effects in the seismic analysis of nuclear power plants is discussed. A procedure to evaluate and use equivalent viscous damping coefficients in conjunction with the substructure method of finite element analysis is outlined in detail

  12. Piezoelectric materials for tissue regeneration: A review.

    Science.gov (United States)

    Rajabi, Amir Hossein; Jaffe, Michael; Arinzeh, Treena Livingston

    2015-09-01

    The discovery of piezoelectricity, endogenous electric fields and transmembrane potentials in biological tissues raised the question whether or not electric fields play an important role in cell function. It has kindled research and the development of technologies in emulating biological electricity for tissue regeneration. Promising effects of electrical stimulation on cell growth and differentiation and tissue growth has led to interest in using piezoelectric scaffolds for tissue repair. Piezoelectric materials can generate electrical activity when deformed. Hence, an external source to apply electrical stimulation or implantation of electrodes is not needed. Various piezoelectric materials have been employed for different tissue repair applications, particularly in bone repair, where charges induced by mechanical stress can enhance bone formation; and in neural tissue engineering, in which electric pulses can stimulate neurite directional outgrowth to fill gaps in nervous tissue injuries. In this review, a summary of piezoelectricity in different biological tissues, mechanisms through which electrical stimulation may affect cellular response, and recent advances in the fabrication and application of piezoelectric scaffolds will be discussed. The discovery of piezoelectricity, endogenous electric fields and transmembrane potentials in biological tissues has kindled research and the development of technologies using electrical stimulation for tissue regeneration. Piezoelectric materials generate electrical activity in response to deformations and allow for the delivery of an electrical stimulus without the need for an external power source. As a scaffold for tissue engineering, growing interest exists due to its potential of providing electrical stimulation to cells to promote tissue formation. In this review, we cover the discovery of piezoelectricity in biological tissues, its connection to streaming potentials, biological response to electrical stimulation and

  13. Absorbed dose measurement by using tissue equivalent ionization chamber (pair ionization chamber) in the Yayoi reactor

    International Nuclear Information System (INIS)

    Sasuga, N.; Okamura, K.; Terakado, T.; Mabuchi, Y.; Nakagawa, T.; Sukegawa, Toshio; Aizawa, C.; Saito, I.; Oka, Yoshiaki

    1998-01-01

    Each dose rate of neutron and gamma ray in the thermal column of the Yayoi reactor, in which an epithermal neutron field will be used for the boron neutron capture therapy, was measured by using a tissue equivalent ionization chamber and a graphite chamber. The tissue equivalent ionization chamber has some response to both neutron and gamma ray, but the graphite chamber has a few response to the neutron, so called pair ionization chamber method. The epithermal neutron fluxes of the thermal column were calculated by ANISN (one dimensional neutron-gamma transport code). A measured value for gamma dose rate by the pair ionization chamber agrees relevantly with a calculated result. For neutron dose rate, however, the measured value was too much small in comparison with the calculated result. The discrepancy between the measured value and the calculated result for neutron dose rate is discussed in detail in the report. (M. Suetake)

  14. Gas electron multiplier (GEM) operation with tissue-equivalent gases at various pressures

    International Nuclear Information System (INIS)

    Farahmand, M.; Bos, A.J.J.; Eijk, C.W.E. van

    2003-01-01

    We have studied the operation of two different Gas Electron Multiplier (GEM) structures in both methane and propane based Tissue-Equivalent (TE) gases at different pressures varying from 0.1 to 1 atm. This work was motivated to explore the possibility of using a GEM for a new type of Tissue Equivalent Proportional Counter. In methane based TE gas, a maximum safe GEM gain of 1.5x10 3 has been reached while in propane based TE gas this is 6x10 3 . These maxima have been reached at different gas pressures depending on GEM structure and TE gas. Furthermore, we observed a decrease of the GEM gain in time before it becomes stable. Charge up/polarisation effects can explain this

  15. Ignition delay of combustible materials in normoxic equivalent environments

    Science.gov (United States)

    Sara McAllister; Carlos Fernandez-Pello; Gary Ruff; David Urban

    2009-01-01

    Material flammability is an important factor in determining the pressure and composition (fraction of oxygen and nitrogen) of the atmosphere in the habitable volume of exploration vehicles and habitats. The method chosen in this work to quantify the flammability of a material is by its ease of ignition. The ignition delay time was defined as the time it takes a...

  16. Dose determination algorithms for a nearly tissue equivalent multi-element thermoluminescent dosimeter

    International Nuclear Information System (INIS)

    Moscovitch, M.; Chamberlain, J.; Velbeck, K.J.

    1988-01-01

    In a continuing effort to develop dosimetric systems that will enable reliable interpretation of dosimeter readings in terms of the absorbed dose or dose-equivalent, a new multi-element TL dosimeter assembly for Beta and Gamma dose monitoring has been designed. The radiation-sensitive volumes are four LiF-TLD elements, each covered by its own unique filter. For media-matching, care has been taken to employ nearly tissue equivalent filters of thicknesses of 1000 mg/cm 2 and 300 mg/cm 2 for deep dose and dose to the lens-of-the-eye measurements respectively. Only one metal filter (Cu) is employed to provide low energy photon discrimination. A Thin TL element (0.09 mm thick) is located behind an open window designed to improve the energy under-response to low energy beta rays and to provide closer estimate of the shallow dose equivalent. The deep and shallow dose equivalents are derived from the correlation of the response of the various TL elements to the above quantities through computations based on previously defined relationships obtained from experimental results. The theoretical formalization for the dose calculation algorithms is described in detail, and provides a useful methodology which can be applied to different tissue-equivalent dosimeter assemblies. Experimental data has been obtained by performing irradiation according to the specifications established by DOELAP, using 27 types of pure and mixed radiation fields including Cs-137 gamma rays, low energy photons down to 20 keV, Sr/Y-90, Uranium, and Tl-204 beta particles

  17. Tissue-equivalent torso phantom for calibration of transuranic-nuclide counting facilities

    International Nuclear Information System (INIS)

    Griffith, R.V.; Anderson, A.L.; Dean, P.N.; Fisher, J.C.; Sundbeck, C.W.

    1986-01-01

    Several tissue-equivalent human-torso phantoms have been constructed for the calibration of counting systems used for in-vivo measurement of transuranic radionuclides. The phantoms contain a simulated human rib cage (in some cases, real bone) and removable model organs, and they include tissue-equivalent chest plates that can be placed over the torso to simulate people with a wide range of statures. The organs included are the lungs, liver, and tracheobronchial lymph nodes. Polyurethane with varying concentrations of added calcium was used to simulate the linear photon-attenuation properties of various human tissues, including lean muscle, adipose-muscle mixtures, cartilage, and bone. Foamed polyurethane was used to simulate lung tissue. Organs have been loaded with highly pure 238 Pu, 239 Pu, 241 Am, and other radionuclides of interest. The validity of the phantom as a calibration standard has been checked in separate intercomparison studies using human subjects whose lungs contained a plutonium simulant. The resulting phantom calibration factors generally compared to within +-20% of the average calibration factors obtained for the human subjects

  18. Equivalent circuit of frog atrial tissue as determined by voltage clamp-unclamp experiments.

    Science.gov (United States)

    Tarr, M; Trank, J

    1971-11-01

    The equivalent circuit that has been used in the analysis of nerve voltage-clamp data is that of the membrane capacity in parallel with the membrane resistance. Voltage-clamp experiments on frog atrial tissue indicate that this circuit will not suffice for this cardiac tissue. The change in membrane current associated with a step change in membrane potential does not show a rapid spike of capacitive current as would be expected for the simple parallel resistance-capacitance network. Rather, there is a step change in current followed by an exponential decay in current with a time constant of about 1 msec. This relatively slow capacitive charging current suggests that there is a resistance in series with the membrane capacity. A possible equivalent circuit is that of a series resistance external to the parallel resistance-capacitance network of the cell membranes. Another possible circuit assumes that the series resistance is an integral part of the cell membrane. The data presented in this paper demonstrate that the equivalent circuit of a bundle of frog atrial muscle is that of an external resistance in series with the cell membranes.

  19. Simulated Response of a Tissue-equivalent Proportional Counter on the Surface of Mars.

    Science.gov (United States)

    Northum, Jeremy D; Guetersloh, Stephen B; Braby, Leslie A; Ford, John R

    2015-10-01

    Uncertainties persist regarding the assessment of the carcinogenic risk associated with galactic cosmic ray (GCR) exposure during a mission to Mars. The GCR spectrum peaks in the range of 300(-1) MeV n to 700 MeV n(-1) and is comprised of elemental ions from H to Ni. While Fe ions represent only 0.03% of the GCR spectrum in terms of particle abundance, they are responsible for nearly 30% of the dose equivalent in free space. Because of this, radiation biology studies focusing on understanding the biological effects of GCR exposure generally use Fe ions. Acting as a thin shield, the Martian atmosphere alters the GCR spectrum in a manner that significantly reduces the importance of Fe ions. Additionally, albedo particles emanating from the regolith complicate the radiation environment. The present study uses the Monte Carlo code FLUKA to simulate the response of a tissue-equivalent proportional counter on the surface of Mars to produce dosimetry quantities and microdosimetry distributions. The dose equivalent rate on the surface of Mars was found to be 0.18 Sv y(-1) with an average quality factor of 2.9 and a dose mean lineal energy of 18.4 keV μm(-1). Additionally, albedo neutrons were found to account for 25% of the dose equivalent. It is anticipated that these data will provide relevant starting points for use in future risk assessment and mission planning studies.

  20. Investigation of real tissue water equivalent path lengths using an efficient dose extinction method

    Science.gov (United States)

    Zhang, Rongxiao; Baer, Esther; Jee, Kyung-Wook; Sharp, Gregory C.; Flanz, Jay; Lu, Hsiao-Ming

    2017-07-01

    For proton therapy, an accurate conversion of CT HU to relative stopping power (RSP) is essential. Validation of the conversion based on real tissue samples is more direct than the current practice solely based on tissue substitutes and can potentially address variations over the population. Based on a novel dose extinction method, we measured water equivalent path lengths (WEPL) on animal tissue samples to evaluate the accuracy of CT HU to RSP conversion and potential variations over a population. A broad proton beam delivered a spread out Bragg peak to the samples sandwiched between a water tank and a 2D ion-chamber detector. WEPLs of the samples were determined from the transmission dose profiles measured as a function of the water level in the tank. Tissue substitute inserts and Lucite blocks with known WEPLs were used to validate the accuracy. A large number of real tissue samples were measured. Variations of WEPL over different batches of tissue samples were also investigated. The measured WEPLs were compared with those computed from CT scans with the Stoichiometric calibration method. WEPLs were determined within  ±0.5% percentage deviation (% std/mean) and  ±0.5% error for most of the tissue surrogate inserts and the calibration blocks. For biological tissue samples, percentage deviations were within  ±0.3%. No considerable difference (extinction measurement took around 5 min to produce ~1000 WEPL values to be compared with calculations. This dose extinction system measures WEPL efficiently and accurately, which allows the validation of CT HU to RSP conversions based on the WEPL measured for a large number of samples and real tissues.

  1. Development and Characterization of Tissue Equivalent Proportional Counter for Radiation Monitoring in International Space Station

    Directory of Open Access Journals (Sweden)

    Uk-Won Nam

    2013-06-01

    Full Text Available Tissue equivalent proportional counter (TEPC can measure the Linear Energy Transfer (LET spectrum and calculate the equivalent dose for the complicated radiation field in space. In this paper, we developed and characterized a TEPC for radiation monitoring in International Space Station (ISS. The prototype TEPC which can simulate a 2 μm of the site diameter for micro-dosimetry has been tested with a standard alpha source (241Am, 5.5 MeV. Also, the calibration of the TEPC was performed by the 252Cf neutron standard source in Korea Research Institute of Standards and Science (KRISS. The determined calibration factor was kf = 3.59×10-7 mSv/R.

  2. Changes of Dielectric Properties induced by Fast neutrons in Tissue Equivalent Plastic A-150

    International Nuclear Information System (INIS)

    Abdou, M.S.

    2000-01-01

    Tissue equivalent plastic A-150 (TEP A-150) samples are exposed to fast neutrons. Dielectric studies for TEP A-150 are carried out in the frequency range from 40 Hz to 4 MHz in the temperature range 295-343 K. The obtained data revealed that, both the dielectric properties and conductivity sigma ac (omega) of TEP A-150 are altered when irradiated by a relatively high fast neutron dose (15 Sv). The values of dielectric constant and conductivity are increased for the irradiated samples to about 24% than the blank samples

  3. Radiation protection instruments based on tissue equivalent proportional counters: Part II of an international intercomparison

    International Nuclear Information System (INIS)

    Alberts, W.G.; Dietz, E.; Guldbakke, S.; Kluge, H.; Schumacher, H.

    1988-04-01

    This report describes the irradiation conditions and procedures of Part II of an international intercomparison of tissue-equivalent proportional counters used for radiation protection measurements. The irradiations took place in monoenergetic reference neutron fields produced by the research reactor and accelerator facilities of the PTB Braunschweig in the range from thermal neutrons to 14.8 MeV. In addition measurements were performed in 60 Co and D 2 O-moderated 252 Cf radiation fields. Prototype instruments from 7 European groups were investigated. The results of the measurements are summarized and compared with the reference data of the irradiations. (orig.) [de

  4. Use of tissue equivalent proportional counters to characterize radiation quality on the space shuttle

    International Nuclear Information System (INIS)

    Braby, L.A.; Conroy, T.J.; Elegy, D.C.; Brackenbush, L.W.

    1992-04-01

    Tissue equivalent proportional counters (TEPC) are essentially cavity ionization chambers operating at low pressure and with gas gain. A small, battery powered, TEPC spectrometer, which records lineal energy spectra at one minute intervals, has been used on several space shuttle missions. The data it has collected clearly show the South Atlantic anomaly and indicate a mean quality factor somewhat higher than expected. An improved type of instrument has been developed with sufficient memory to record spectra at 10 second intervals, and with increased resolution for low LET events. This type of instrument will be used on most future space shuttle flights and in some international experiments

  5. Natural Origin Materials for Osteochondral Tissue Engineering.

    Science.gov (United States)

    Bonani, Walter; Singhatanadgige, Weerasak; Pornanong, Aramwit; Motta, Antonella

    2018-01-01

    Materials selection is a critical aspect for the production of scaffolds for osteochondral tissue engineering. Synthetic materials are the result of man-made operations and have been investigated for a variety of tissue engineering applications. Instead, the products of physiological processes and the metabolic activity of living organisms are identified as natural materials. Over the recent decades, a number of natural materials, namely, biopolymers and bioceramics, have been proposed as the main constituent of osteochondral scaffolds, but also as cell carriers and signaling molecules. Overall, natural materials have been investigated both in the bone and in the cartilage compartment, sometimes alone, but often in combination with other biopolymers or synthetic materials. Biopolymers and bioceramics possess unique advantages over their synthetic counterparts due similarity with natural extracellular matrix, the presence of cell recognition sites and tunable chemistry. However, the characteristics of natural origin materials can vary considerably depending on the specific source and extraction process. A deeper understanding of the relationship between material variability and biological activity and the definition of standardized manufacturing procedures will be crucial for the future of natural materials in tissue engineering.

  6. MOSFET dosimeter depth-dose measurements in heterogeneous tissue-equivalent phantoms at diagnostic x-ray energies

    International Nuclear Information System (INIS)

    Jones, A.K.; Pazik, F.D.; Hintenlang, D.E.; Bolch, W.E.

    2005-01-01

    The objective of the present study was to explore the use of the TN-1002RD metal-oxide-semiconductor field effect transistor (MOSFET) dosimeter for measuring tissue depth dose at diagnostic photon energies in both homogeneous and heterogeneous tissue-equivalent materials. Three cylindrical phantoms were constructed and utilized as a prelude to more complex measurements within tomographic physical phantoms of pediatric patients. Each cylindrical phantom was constructed as a stack of seven 5-cm-diameter and 1-cm-thick discs of materials radiographically representative of either soft tissue (S), bone (B), or lung tissue (L) at diagnostic photon energies. In addition to a homogeneous phantom of soft tissue (SSSSSSS), two heterogeneous phantoms were constructed: SSBBSSS and SBLLBSS. MOSFET dosimeters were then positioned at the interface of each disc, and the phantoms were then irradiated at 66 kVp and 200 mAs. Measured values of absorbed dose at depth were then compared to predicated values of point tissue dose as determined via Monte Carlo radiation transport modeling. At depths exceeding 2 cm, experimental results matched the computed values of dose with high accuracy regardless of the dosimeter orientation (epoxy bubble facing toward or away from the x-ray beam). Discrepancies were noted, however, between measured and calculated point doses near the surface of the phantom (surface to 2 cm depth) when the dosimeters were oriented with the epoxy bubble facing the x-ray beam. These discrepancies were largely eliminated when the dosimeters were placed with the flat side facing the x-ray beam. It is therefore recommended that the MOSFET dosimeters be oriented with their flat sides facing the beam when they are used at shallow depths or on the surface of either phantoms or patients

  7. Photoprotection by pistachio bioactives in a 3-dimensional human skin equivalent tissue model.

    Science.gov (United States)

    Chen, C-Y Oliver; Smith, Avi; Liu, Yuntao; Du, Peng; Blumberg, Jeffrey B; Garlick, Jonathan

    2017-09-01

    Reactive oxygen species (ROS) generated during ultraviolet (UV) light exposure can induce skin damage and aging. Antioxidants can provide protection against oxidative injury to skin via "quenching" ROS. Using a validated 3-dimensional (3D) human skin equivalent (HSE) tissue model that closely mimics human skin, we examined whether pistachio antioxidants could protect HSE against UVA-induced damage. Lutein and γ-tocopherol are the predominant lipophilic antioxidants in pistachios; treatment with these compounds prior to UVA exposure protected against morphological changes to the epithelial and connective tissue compartments of HSE. Pistachio antioxidants preserved overall skin thickness and organization, as well as fibroblast morphology, in HSE exposed to UVA irradiation. However, this protection was not substantiated by the analysis of the proliferation of keratinocytes and apoptosis of fibroblasts. Additional studies are warranted to elucidate the basis of these discordant results and extend research into the potential role of pistachio bioactives promoting skin health.

  8. Measurement of the first Townsend ionization coefficient in a methane-based tissue-equivalent gas

    Energy Technology Data Exchange (ETDEWEB)

    Petri, A.R. [Instituto de Pesquisas Energéticas e Nucleares, Cidade Universitária, 05508-000 São Paulo (Brazil); Gonçalves, J.A.C. [Instituto de Pesquisas Energéticas e Nucleares, Cidade Universitária, 05508-000 São Paulo (Brazil); Departamento de Física, Pontifícia Universidade Católica de São Paulo, 01303-050 São Paulo (Brazil); Mangiarotti, A. [Instituto de Física - Universidade de São Paulo, Cidade Universitária, 05508-080 São Paulo (Brazil); Botelho, S. [Instituto de Pesquisas Energéticas e Nucleares, Cidade Universitária, 05508-000 São Paulo (Brazil); Bueno, C.C., E-mail: ccbueno@ipen.br [Instituto de Pesquisas Energéticas e Nucleares, Cidade Universitária, 05508-000 São Paulo (Brazil)

    2017-03-21

    Tissue-equivalent gases (TEGs), often made of a hydrocarbon, nitrogen, and carbon dioxide, have been employed in microdosimetry for decades. However, data on the first Townsend ionization coefficient (α) in such mixtures are scarce, regardless of the chosen hydrocarbon. In this context, measurements of α in a methane-based tissue-equivalent gas (CH{sub 4} – 64.4%, CO{sub 2} – 32.4%, and N{sub 2} – 3.2%) were performed in a uniform field configuration for density-normalized electric fields (E/N) up to 290 Td. The setup adopted in our previous works was improved for operating at low pressures. The modifications introduced in the apparatus and the experimental technique were validated by comparing our results of the first Townsend ionization coefficient in nitrogen, carbon dioxide, and methane with those from the literature and Magboltz simulations. The behavior of α in the methane-based TEG was consistent with that observed for pure methane. All the experimental results are included in tabular form in the .

  9. Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter.

    Science.gov (United States)

    Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem

    2016-01-01

    To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

  10. Test of tissue-equivalent scintillation detector for dose measurement of megavoltage beams

    International Nuclear Information System (INIS)

    Geso, M.; Ackerly, T.; Clift, M.A.

    2000-01-01

    Full text: The measurement of depth doses and profiles for a stereotactic radiotherapy beam presents special problems associated with the small beam size compared to the dosimeter's active detection area. In this work a locally fabricated organic plastic scintillator detector has been used to measure the depth dose and profile of a stereotactic radiotherapy beam. The 6MV beam is 1.25 cm diameter at isocentre, typical of small field stereotactic radiosurgery. The detector is a water/tissue equivalent plastic scintillator that is accompanied by Cerenkov subtraction detector. In this particular application, a negligible amount of Cerenkov light was detected. A photodiode and an electronic circuit is used instead of a photomultiplier for signal amplification. Comparison with data using a diode detector and a small size ionization chamber, indicate that the organic plastic scintillator detector is a valid detector for stereotactic radiosurgery dosimetry. The tissue equivalence of the organic scintillator also holds the promise of accurate dosimetry in the build up region. Depth doses measured using our plastic scintillator agree to within about 1% with those obtained using commercially available silicon diodes. Beam profiles obtained using plastic scintillator presents correct field width to within 0.35 mm, however some artifacts are visible in the profiles. These artifacts are about 5% discrepancy which has been shown not to be a significant factor in stereotactic radiotherapy dosimetry. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

  11. Microdosimetry of 14.7 MeV neutrons in tissue equivalent phantom

    International Nuclear Information System (INIS)

    Amols, H.I.

    1974-01-01

    An experimental and theoretical investigation has been made of energy deposition in tissue by neutrons. A one-half inch diameter Rossi type proportional counter was used to simulate a one-micron sphere of tissue. Event-size spectra were taken in air, and at various positions in a large volume of tissue equivalent fluid. From the raw spectra, LET distributions were determined, as well as dose fractions for protons, alphas, and heavy ions, and dose average and track-average LET values. The shape of the D(L) vs. LET curve is found to undergo significant change in the phantom due to moderation of the neutron beam. In addition, previous calculations of LET spectra in air are shown to be in error, and theoretical RBE and OER values, based on data from this experiment are in better agreement with biological results. A two-step theoretical calculation has also been carried out. An original Monte Carlo computer code was used to calculate neutron fluences in phantom (1), which were converted to LET distributions via standard algorithms (2). Agreement with experiment is very good, both in air and in phantom. Edge effects, backscatter effects, and effects of phantom size were also studied

  12. Equivalent Electromagnetic Constants for Microwave Application to Composite Materials for the Multi-Scale Problem

    Directory of Open Access Journals (Sweden)

    Keisuke Fujisaki

    2013-11-01

    Full Text Available To connect different scale models in the multi-scale problem of microwave use, equivalent material constants were researched numerically by a three-dimensional electromagnetic field, taking into account eddy current and displacement current. A volume averaged method and a standing wave method were used to introduce the equivalent material constants; water particles and aluminum particles are used as composite materials. Consumed electrical power is used for the evaluation. Water particles have the same equivalent material constants for both methods; the same electrical power is obtained for both the precise model (micro-model and the homogeneous model (macro-model. However, aluminum particles have dissimilar equivalent material constants for both methods; different electric power is obtained for both models. The varying electromagnetic phenomena are derived from the expression of eddy current. For small electrical conductivity such as water, the macro-current which flows in the macro-model and the micro-current which flows in the micro-model express the same electromagnetic phenomena. However, for large electrical conductivity such as aluminum, the macro-current and micro-current express different electromagnetic phenomena. The eddy current which is observed in the micro-model is not expressed by the macro-model. Therefore, the equivalent material constant derived from the volume averaged method and the standing wave method is applicable to water with a small electrical conductivity, although not applicable to aluminum with a large electrical conductivity.

  13. Calculation of W for low energy electrons in tissue-equivalent gas. [<10 keV

    Energy Technology Data Exchange (ETDEWEB)

    Dayashankar, [Bhabha Atomic Research Centre, Bombay (India). Div. of Radiation Protection

    1977-11-01

    The mean energy expended per ion pair formed (W-value) in the tissue-equivalent gas for incident electrons of energy up to 10 keV has been calculated in the continuous slowing-down approximation. The effect of secondary and tertiary electrons has been considered by utilizing recent measurements of Opal et al., (1971, J. Chem. Phys., 55,4100) on the energy spectra of low-energy secondary electrons and the Mott formula for the spectra of high-energy secondaries. The results, which are provisional in nature due to the limitations on the accuracy of the input cross-section data and the neglect of the discrete nature of energy loss process, are compared with the available measurements.

  14. Development of a drift tissue equivalent proportional counter for radiation protection personnel dosimetry

    International Nuclear Information System (INIS)

    Bordy, J.M.

    1992-04-01

    A new multicellular geometry for proportional counter has been developed. It is made of several drift regions which are some holes drilled in the cathode in front of anodes wires. The present work is made of 3 parts: 1) A theoretical evaluation of the multicellular counter characteristics: the sensitivity increases by a factor 15 vs the Tinelli Merlin-Gerin counter; the chord length distribution study shows the possibility to use a Dirac function for the dosimetry calculations; a tissue equivalent gas mixture based on argon and propane is designed. 2) The production of a monocellular prototype made of a hole and a needle shaped anode. 3) An experimental study of the prototype electrical characteristics and a computation of the electrical field in the counter. The focalization and the electron drift into the hole, the proportional operating mode are shown. Irradiations in front of photon and neutron sources verify these results

  15. Investigation of 1-cm dose equivalent for photons behind shielding materials

    International Nuclear Information System (INIS)

    Hirayama, Hideo; Tanaka, Shun-ichi

    1991-03-01

    The ambient dose equivalent at 1-cm depth, assumed equivalent to the 1-cm dose equivalent in practical dose estimations behind shielding slabs of water, concrete, iron or lead for normally incident photons having various energies was calculated by using conversion factors for a slab phantom. It was compared with the 1-cm depth dose calculated with the Monte Carlo code EGS4. It was concluded from this comparison that the ambient dose equivalent calculated by using the conversion factors for the ICRU sphere could be used for the evaluation of the 1-cm dose equivalent for the sphere phantom within 20% errors. Average and practical conversion factors are defined as the conversion factors from exposure to ambient dose equivalent in a finite slab or an infinite one, respectively. They were calculated with EGS4 and the discrete ordinates code PALLAS. The exposure calculated with simple estimation procedures such as point kernel methods can be easily converted to ambient dose equivalent by using these conversion factors. The maximum value between 1 and 30 mfp can be adopted as the conversion factor which depends only on material and incident photon energy. This gives the ambient dose equivalent on the safe side. 13 refs., 7 figs., 2 tabs

  16. Derivation of Accident-Specific Material-at-Risk Equivalency Factors

    Energy Technology Data Exchange (ETDEWEB)

    Jason P. Andrus; Dr. Chad L. Pope

    2012-05-01

    A novel method for calculating material at risk (MAR) dose equivalency developed at the Idaho National Laboratory (INL) now allows for increased utilization of dose equivalency for facility MAR control. This method involves near-real time accounting for the use of accident and material specific release and transport. It utilizes all information from the committed effective dose equation and the five factor source term equation to derive dose equivalency factors which can be used to establish an overall facility or process MAR limit. The equivalency factors allow different nuclide spectrums to be compared for their respective dose consequences by relating them to a specific quantity of an identified reference nuclide. The ability to compare spectrums to a reference limit ensures that MAR limits are in fact bounding instead of attempting to establish a representative or bounding spectrum which may lead to unintended or unanalyzed configurations. This methodology is then coupled with a near real time material tracking system which allows for accurate and timely material composition information and corresponding MAR equivalency values. The development of this approach was driven by the complex nature of processing operations in some INL facilities. This type of approach is ideally suited for facilities and processes where the composition of the MAR and possible release mechanisms change frequently but in well defined fashions and in a batch-type nature.

  17. A test material for tissue characterisation and system calibration in MRI

    International Nuclear Information System (INIS)

    Walker, P.M.; Lerski, R.A.

    1989-01-01

    A tissue-equivalent test material for MR1 has been produced from a polysaccharide gel, agarose, containing gadolinium chloride chelated to EDTA. By varying the amounts of each constituent, the T 1 and T 2 of the material can be varied independently. As a result, the entire range of in vivo tissue relaxation times can be covered. Through the mathematical modelling of the 1 H relaxation theories for both the gel and chelated paramagnetic ion, it has been possible to create a material with relaxation properties and behaviour predictable as functions of both the Larmor frequency and temperature. The similarity of the material to in vivo tissues, in terms of its biological and physical NMR characteristics, makes it an excellent tissue-equivalent substance, in addition to being an accurate calibration standard for routine MRI. (author)

  18. Equivalent material properties of perforated plate with triangular or square penetration pattern for dynamic analysis

    International Nuclear Information System (INIS)

    Jhung, Myung Jo; Jo, Jong Chull

    2006-01-01

    For a perforated plate, it is challenging to develop a finite element model due to the necessity of the fine meshing of the plate, especially if it is submerged in fluid. This necessitates the use of a solid plate with equivalent material properties. Unfortunately, the effective elastic constants suggested by the ASME code are deemed not valid for a model analysis. Therefore, in this study the equivalent material properties of a perforated plate are suggested by performing several finite element analyses with respect to the ligament efficiencies

  19. Biomimetic material strategies for cardiac tissue engineering

    International Nuclear Information System (INIS)

    Prabhakaran, Molamma P.; Venugopal, J.; Kai, Dan; Ramakrishna, Seeram

    2011-01-01

    Cardiovascular disease precedes many serious complications including myocardial infarction (MI) and it remains a major problem for the global community. Adult mammalian heart has limited ability to regenerate and compensate for the loss of cardiomyocytes. Restoration of cardiac function by replacement of diseased myocardium with functional cardiomyocytes is an intriguing strategy because it offers a potential cure for MI. Biomaterials are fabricated in nanometer scale dimensions by combining the chemical, biological, mechanical and electrical aspects of material for potential tissue engineering (TE) applications. Synthetic polymers offer advantageous in their ability to tailor the mechanical properties, and natural polymers offer cell recognition sites necessary for cell, adhesion and proliferation. Cardiac tissue engineering (TE) aim for the development of a bioengineered construct that can provide physical support to the damaged cardiac tissue by replacing certain functions of the damaged extracellular matrix and prevent adverse cardiac remodeling and dysfunction after MI. Electrospun nanofibers are applied as heart muscle patches, while hydrogels serve as a platform for controlled delivery of growth factors, prevent mechanical complications and assist in cell recruitment. This article reviews the applications of different natural and synthetic polymeric materials utilized as cardiac patches, injectables or 3D constructs for cardiac TE. Smart organization of nanoscale assemblies with synergistic approaches of utilizing nanofibers and hydrogels could further advance the field of cardiac tissue engineering. Rapid innovations in biomedical engineering and cell biology will bring about new insights in the development of optimal scaffolds and methods to create tissue constructs with relevant contractile properties and electrical integration to replace or substitute the diseased myocardium.

  20. Biomimetic material strategies for cardiac tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, Molamma P., E-mail: nnimpp@nus.edu.sg [Health Care and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Venugopal, J. [Health Care and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Kai, Dan [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore (Singapore); Ramakrishna, Seeram [Health Care and Energy Materials Laboratory, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore)

    2011-04-08

    Cardiovascular disease precedes many serious complications including myocardial infarction (MI) and it remains a major problem for the global community. Adult mammalian heart has limited ability to regenerate and compensate for the loss of cardiomyocytes. Restoration of cardiac function by replacement of diseased myocardium with functional cardiomyocytes is an intriguing strategy because it offers a potential cure for MI. Biomaterials are fabricated in nanometer scale dimensions by combining the chemical, biological, mechanical and electrical aspects of material for potential tissue engineering (TE) applications. Synthetic polymers offer advantageous in their ability to tailor the mechanical properties, and natural polymers offer cell recognition sites necessary for cell, adhesion and proliferation. Cardiac tissue engineering (TE) aim for the development of a bioengineered construct that can provide physical support to the damaged cardiac tissue by replacing certain functions of the damaged extracellular matrix and prevent adverse cardiac remodeling and dysfunction after MI. Electrospun nanofibers are applied as heart muscle patches, while hydrogels serve as a platform for controlled delivery of growth factors, prevent mechanical complications and assist in cell recruitment. This article reviews the applications of different natural and synthetic polymeric materials utilized as cardiac patches, injectables or 3D constructs for cardiac TE. Smart organization of nanoscale assemblies with synergistic approaches of utilizing nanofibers and hydrogels could further advance the field of cardiac tissue engineering. Rapid innovations in biomedical engineering and cell biology will bring about new insights in the development of optimal scaffolds and methods to create tissue constructs with relevant contractile properties and electrical integration to replace or substitute the diseased myocardium.

  1. Operation of gas electron multiplier (GEM) with propane gas at low pressure and comparison with tissue-equivalent gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    De Nardo, L., E-mail: laura.denardo@unipd.it [University of Padova, Physics and Astronomy Department and PD-INFN, via Marzolo 8, I-35131 Padova (Italy); Farahmand, M., E-mail: majid.farahmand@rivm.nl [Centre for Environmental Safety and Security, National Institute for Public Health and the Environment (RIVM), PO Box 1, NL-3720 BA Bilthoven (Netherlands)

    2016-05-21

    A Tissue-Equivalent Proportional Counter (TEPC), based on a single GEM foil of standard geometry, has been tested with pure propane gas at low pressure, in order to simulate a tissue site of about 1 µm equivalent size. In this work, the performance of GEM with propane gas at a pressure of 21 and 28 kPa will be presented. The effective gas gain was measured in various conditions using a {sup 244}Cm alpha source. The dependence of effective gain on the electric field strength along the GEM channel and in the drift and induction region was investigated. A maximum effective gain of about 5×10{sup 3} has been reached. Results obtained in pure propane gas are compared with gas gain measurements in gas mixtures commonly employed in microdosimetry, that is propane and methane based Tissue-Equivalent gas mixtures.

  2. Characterization of paraffin based breast tissue equivalent phantom using a CdTe detector pulse height analysis.

    Science.gov (United States)

    Cubukcu, Solen; Yücel, Haluk

    2016-12-01

    In this study, paraffin was selected as a base material and mixed with different amounts of CaSO 4 ·2H 2 O and H 3 BO 3 compounds in order to mimic breast tissue. Slab phantoms were produced with suitable mixture ratios of the additives in the melted paraffin. Subsequently, these were characterized in terms of first half-value layer (HVL) in the mammographic X-ray range using a pulse-height spectroscopic analysis with a CdTe detector. Irradiations were performed in the energy range of 23-35 kV p under broad beam conditions from Mo/Mo and Mo/Rh target/filter combinations. X-ray spectra were acquired with a CdTe detector without and with phantom material interposition in increments of 1 cm thickness and then evaluated to obtain the transmission data. The net integral areas of the spectra for the slabs were used to plot the transmission curves and these curves were fitted to the Archer model function. The results obtained for the slabs were compared with those of standard mammographic phantoms such as CIRS BR series phantoms and polymethylmethacrylate plates (PMMA). From the evaluated transmission curves, the mass attenuation coefficients and HVLs of some mixtures are close to those of the commercially available standard mammography phantoms. Results indicated that when a suitable proportion of H 3 BO 3 and CaSO 4 ·2H 2 O is added to the paraffin, the resulting material may be a good candidate for a breast tissue equivalent phantom.

  3. TU-H-CAMPUS-IeP2-05: Breast and Soft Tissue-Equivalent 3D Printed Phantoms for Imaging and Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Hintenlang, D; Terracino, B [University Florida, Gainesville, FL (United States)

    2016-06-15

    Purpose: The study has the goal to demonstrate that breast and soft tissue-equivalent phantoms for dosimetry applications in the diagnostic energy range can be fabricated using common 3D printing methods. Methods: 3D printing provides the opportunity to rapidly prototype uniquely designed objects from a variety of materials. Common 3D printers are usually limited to printing objects based on thermoplastic materials such as PLA, or ABS. The most commonly available plastic is PLA, which has a density significantly greater than soft tissue. We utilized a popular 3D printer to demonstrate that tissue specific phantom materials can be generated through the careful selection of 3D printing parameters. A series of stepwedges were designed and printed using a Makerbot Replicator2 3D printing system. The print file provides custom adjustment of the infill density, orientation and position of the object on the printer stage, selection of infill patterns, and other control parameters. The x-ray attenuation and uniformity of fabricated phantoms were evaluated and compared to common tissue-equivalent phantom materials, acrylic and BR12. X-ray exposure measurements were made using narrow beam geometry on a clinical mammography unit at 28 kVp on the series of phantoms. The 3D printed phantoms were imaged at 28 kVp to visualize the internal structure and uniformity in different planes of the phantoms. Results: By utilizing specific in-fill density and patterns we are able to produce a phantom closely matching the attenuation characteristics of BR12 at 28 kVp. The in-fill patterns used are heterogeneous, so a judicious selection of fill pattern and the orientation of the fill pattern must be made in order to obtain homogenous attenuation along the intended direction of beam propagation. Conclusions: By careful manipulation of the printing parameters, breast and soft tissue-equivalent phantoms appropriate for use at imaging energies can be fabricated using 3D printing techniques.

  4. TU-H-CAMPUS-IeP2-05: Breast and Soft Tissue-Equivalent 3D Printed Phantoms for Imaging and Dosimetry

    International Nuclear Information System (INIS)

    Hintenlang, D; Terracino, B

    2016-01-01

    Purpose: The study has the goal to demonstrate that breast and soft tissue-equivalent phantoms for dosimetry applications in the diagnostic energy range can be fabricated using common 3D printing methods. Methods: 3D printing provides the opportunity to rapidly prototype uniquely designed objects from a variety of materials. Common 3D printers are usually limited to printing objects based on thermoplastic materials such as PLA, or ABS. The most commonly available plastic is PLA, which has a density significantly greater than soft tissue. We utilized a popular 3D printer to demonstrate that tissue specific phantom materials can be generated through the careful selection of 3D printing parameters. A series of stepwedges were designed and printed using a Makerbot Replicator2 3D printing system. The print file provides custom adjustment of the infill density, orientation and position of the object on the printer stage, selection of infill patterns, and other control parameters. The x-ray attenuation and uniformity of fabricated phantoms were evaluated and compared to common tissue-equivalent phantom materials, acrylic and BR12. X-ray exposure measurements were made using narrow beam geometry on a clinical mammography unit at 28 kVp on the series of phantoms. The 3D printed phantoms were imaged at 28 kVp to visualize the internal structure and uniformity in different planes of the phantoms. Results: By utilizing specific in-fill density and patterns we are able to produce a phantom closely matching the attenuation characteristics of BR12 at 28 kVp. The in-fill patterns used are heterogeneous, so a judicious selection of fill pattern and the orientation of the fill pattern must be made in order to obtain homogenous attenuation along the intended direction of beam propagation. Conclusions: By careful manipulation of the printing parameters, breast and soft tissue-equivalent phantoms appropriate for use at imaging energies can be fabricated using 3D printing techniques.

  5. Emergent material properties of developing epithelial tissues.

    Science.gov (United States)

    Machado, Pedro F; Duque, Julia; Étienne, Jocelyn; Martinez-Arias, Alfonso; Blanchard, Guy B; Gorfinkiel, Nicole

    2015-11-23

    Force generation and the material properties of cells and tissues are central to morphogenesis but remain difficult to measure in vivo. Insight is often limited to the ratios of mechanical properties obtained through disruptive manipulation, and the appropriate models relating stress and strain are unknown. The Drosophila amnioserosa epithelium progressively contracts over 3 hours of dorsal closure, during which cell apices exhibit area fluctuations driven by medial myosin pulses with periods of 1.5-6 min. Linking these two timescales and understanding how pulsatile contractions drive morphogenetic movements is an urgent challenge. We present a novel framework to measure in a continuous manner the mechanical properties of epithelial cells in the natural context of a tissue undergoing morphogenesis. We show that the relationship between apicomedial myosin fluorescence intensity and strain during fluctuations is consistent with a linear behaviour, although with a lag. We thus used myosin fluorescence intensity as a proxy for active force generation and treated cells as natural experiments of mechanical response under cyclic loading, revealing unambiguous mechanical properties from the hysteresis loop relating stress to strain. Amnioserosa cells can be described as a contractile viscoelastic fluid. We show that their emergent mechanical behaviour can be described by a linear viscoelastic rheology at timescales relevant for tissue morphogenesis. For the first time, we establish relative changes in separate effective mechanical properties in vivo. Over the course of dorsal closure, the tissue solidifies and effective stiffness doubles as net contraction of the tissue commences. Combining our findings with those from previous laser ablation experiments, we show that both apicomedial and junctional stress also increase over time, with the relative increase in apicomedial stress approximately twice that of other obtained measures. Our results show that in an epithelial

  6. Errors in estimating neutron quality factor using lineal energy distributions measured in tissue-equivalent proportional counters

    International Nuclear Information System (INIS)

    Borak, T.B.; Stinchcomb, T.G.

    1982-01-01

    Neutron dose equivalent is obtained from quality factors which are defined in terms of LET. It is possible to estimate the dose averaged quality factor, antiQ, directly from distributions in lineal energy, y, that are measured in tissue-equivalent proportional counters. This eliminates a mathematical transformation of the absorbed dose from D(y) to D(L). We evaluate the inherent error in computing Q from D(y) rather than D(L) for neutron spectra below 4 MeV. The effects of neutron energy and simulated tissue diameters within a gas cavity are examined in detail. (author)

  7. Dosimetry with tissue-equivalent ionisation chambers in fast neutron fields for biomedical applications

    International Nuclear Information System (INIS)

    Zoetelief, J.; Broerse, J.J.

    1983-01-01

    The use of calibrated tissue-equivalent (TE) ionisation chambers is commonly considered to be the most practical method for total absorbed dose determinations in mixed neutron-photon fields for biomedical applications. The total absorbed dose can be derived from the charge produced within the cavity of an ionisation chamber employing a number of physical parameters. To arrive at the charge produced in the cavity several correction factors have to be introduced which are related to the operational characteristics of the chambers. Information on the operational characteristics of four TE ionisation chambers is presented in relation to ion collection, density and composition of gas in the cavity, wall thickness and effective point of measurement. In addition, some recent results from an ionisation chamber operated at high gas pressures are presented. The total absorbed doses derived from TE ionisation chambers show agreement within the uncertainty limits with results from other independent dosimetry methods, i.e., differential fluence measurements and a TE calorimeter. Conscientious experimentation and a common data base can provide dosimetry results with TE ionisation chambers with variations of less than +-2%. (author)

  8. Effective atomic numbers, electron densities, and tissue equivalence of some gases and mixtures for dosimetry of radiation detectors

    Directory of Open Access Journals (Sweden)

    Singh Vishwanath P.

    2012-01-01

    Full Text Available Total mass attenuation coefficients, µm, effective atomic number, Zeff, and effective electron density, Neff, of different gases - carbon dioxide, methane, acetylene, propane, butane, and pentane used in radiation detectors, have been calculated for the photon energy of 1 keV to 100 GeV. Each gas has constant Zeff values between 0.10 to 10 MeV photon energies; however, these values are way far away from ICRU tissue. Carbon dioxide gas shows the closest tissue equivalence in the entire photon energy spectrum. Relative tissue equivalences of the mixtures of gases with respect to ICRU tissue are in the range of 0.998-1.041 for air, argon (4.5% + methane (95.5%, argon (0.5% + carbon dioxide (99.5%, and nitrogen (5% + methane (7% + carbon dioxide (88%. The gas composition of xenon (0.5% + carbon dioxide (99.5% shows 1.605 times higher tissue equivalence compared to the ICRU tissue. The investigated photon interaction parameters are useful for exposure and energy absorption buildup factors calculation and design, and fabrication of gaseous detectors for ambient radiation measurement by the Geiger-Muller detector, ionization chambers and proportional counters.

  9. Performance tests and comparison of microdosimetric measurements with four tissue-equivalent proportional counters in scanning proton therapy

    Czech Academy of Sciences Publication Activity Database

    Farah, J.; De Saint-Hubert, M.; Mojzeszek, N.; Chiriotti, S.; Gryzinski, M.; Ploc, Ondřej; Trompier, F.; Turek, Karel; Vanhavere, F.; Olko, P.

    2017-01-01

    Roč. 96, JAN (2017), s. 42-52 ISSN 1350-4487 EU Projects: European Commission(XE) 662287 - CONCERT Institutional support: RVO:61389005 Keywords : tissue-equivalent proportional counters * microdosimetry * proton therapy * stray neutrons and prothons Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 1.442, year: 2016

  10. The projected relative index of consequence equivalence of transport of radioactive materials

    International Nuclear Information System (INIS)

    Nandakumar, A.N.

    1999-01-01

    The need exists for defining a unit risk factor to enable analysis to make a proper decision when faced with many options relating to the transport of radioactive materials between sites. A method is discussed for deriving such a factor with reference to the collective dose receivable due to the transport of radioactive material incidental to the production of one GWe.a of nuclear power. This quantity would enable the analyst to determine the projected relative index of consequence equivalence (PRICE) for the transport of various types of radioactive materials. (author)

  11. Biodegradable electroactive materials for tissue engineering applications

    Science.gov (United States)

    Guimard, Nathalie Kathryn

    polymerization can be achieved at the surface of these functionalized films and that the extent of polymer immobilization appears to be affected by the presence of immobilized thiophene. The results reported in this dissertation lead the author to suggest that it is possible to generate biodegradable electroactive materials. Further, she believes that with additional optimization these materials may prove beneficial for the regeneration of peripheral nerves and possibly other tissues that respond favorably to electrical stimulation.

  12. Bioactive Polymeric Materials for Tissue Repair

    Directory of Open Access Journals (Sweden)

    Diane R. Bienek

    2017-01-01

    Full Text Available Bioactive polymeric materials based on calcium phosphates have tremendous appeal for hard tissue repair because of their well-documented biocompatibility. Amorphous calcium phosphate (ACP-based ones additionally protect against unwanted demineralization and actively support regeneration of hard tissue minerals. Our group has been investigating the structure/composition/property relationships of ACP polymeric composites for the last two decades. Here, we present ACP’s dispersion in a polymer matrix and the fine-tuning of the resin affects the physicochemical, mechanical, and biological properties of ACP polymeric composites. These studies illustrate how the filler/resin interface and monomer/polymer molecular structure affect the material’s critical properties, such as ion release and mechanical strength. We also present evidence of the remineralization efficacy of ACP composites when exposed to accelerated acidic challenges representative of oral environment conditions. The utility of ACP has recently been extended to include airbrushing as a platform technology for fabrication of nanofiber scaffolds. These studies, focused on assessing the feasibility of incorporating ACP into various polymer fibers, also included the release kinetics of bioactive calcium and phosphate ions from nanofibers and evaluate the biorelevance of the polymeric ACP fiber networks. We also discuss the potential for future integration of the existing ACP scaffolds into therapeutic delivery systems used in the precision medicine field.

  13. Evaluation of two water-equivalent phantom materials for output calibration of photon and electron beams

    International Nuclear Information System (INIS)

    Liu Lizhong; Prasad, Satish C.; Bassano, Daniel A.

    2003-01-01

    Two commercially available water-equivalent solid phantom materials were evaluated for output calibration in both photon (6-15 MV) and electron (6-20 MeV) beams. The solid water 457 and virtual water materials have the same chemical composition but differ in manufacturing process and density. A Farmer-type ionization chamber was used for measuring the output of the photon beams at 5- and 10-cm depth and electron beams at maximum buildup depth in the solid phantoms and in natural water. The water-equivalency correction factor for the solid materials is defined as the ratio of the chamber reading in natural water to that in the solid at the same linear depth. For photon beams, the correction factor was found to be independent of depth and was 0.987 and 0.993 for 6- and 15-MV beams, respectively, for solid water. For virtual water, the corresponding correction factors were 0.993 and 0.998 for 6- and 15-MV beams, respectively. For electron beams, the correction factors ranged from 1.013 to 1.007 for energies of 6 to 20 MeV for both solid materials. This indicated that the water-equivalency of these materials is within ± 1.3%, making them suitable substitutes for natural water in both photon and electron beam output measurements over a wide energy range. These correction factors are slightly larger than the manufacturers' advertised values (± 1.0% for solid water and ± 0.5% for virtual water). We suggest that these corrections are large enough in most cases and should be applied in the calculation of beam outputs

  14. Temperature dependence of HU values for various water equivalent phantom materials

    International Nuclear Information System (INIS)

    Homolka, P.; Nowotny, R.; Gahleitner, A.

    2002-01-01

    The temperature dependence of water equivalent phantom materials used in radiotherapy and diagnostic imaging has been investigated. Samples of phantom materials based on epoxy resin, polyethylene, a polystyrene-polypropylene mixture and commercially available phantom materials (Solid Water TM , Gammex RMI and Plastic Water TM , Nuclear Associates) were scanned at temperatures from 15 to 40 deg. C and HU values determined. At a reference temperature of 20 deg. C materials optimized for CT applications give HU values close to zero while the commercial materials show an offset of 119.77 HU (Plastic Water) and 27.69 HU (Solid Water). Temperature dependence was lowest for epoxy-based materials (EPX-W: -0.23 HU deg. C -1 ; Solid Water: -0.25 HU deg. C -1 ) and highest for a polyethylene-based material (X0: -0.72 HU deg. C -1 ). A material based on a mixture of polystyrene and polypropylene (PSPP1: -0.27 HU deg. C -1 ) is comparable to epoxy-based materials and water (-0.29 HU deg. C -1 ). (author)

  15. Dose equivalent near the bone-soft tissue interface from nuclear fragments produced by high-energy protons

    Science.gov (United States)

    Shavers, M. R.; Poston, J. W.; Cucinotta, F. A.; Wilson, J. W.

    1996-01-01

    During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments. These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon. That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication. To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons transversing bone and red bone marrow. In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and "worst-case" geometry are used. The use of conventional dosimetry (absorbed dose weighted by aa linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed.

  16. A LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) for biological tissue impedance analysis and equivalent circuit modelling

    KAUST Repository

    Bera, Tushar Kanti

    2016-12-05

    Under an alternating electrical signal, biological tissues produce a complex electrical bioimpedance that is a function of tissue composition and applied signal frequencies. By studying the bioimpedance spectra of biological tissues over a wide range of frequencies, we can noninvasively probe the physiological properties of these tissues to detect possible pathological conditions. Electrical impedance spectroscopy (EIS) can provide the spectra that are needed to calculate impedance parameters within a wide range of frequencies. Before impedance parameters can be calculated and tissue information extracted, impedance spectra should be processed and analyzed by a dedicated software program. National Instruments (NI) Inc. offers LabVIEW, a fast, portable, robust, user-friendly platform for designing dataanalyzing software. We developed a LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) to analyze the electrical impedance spectra for tissue characterization in medical, biomedical and biological applications. Here, we test, calibrate and evaluate the performance of LEBISDI on the impedance data obtained from simulation studies as well as the practical EIS experimentations conducted on electronic circuit element combinations and the biological tissue samples. We analyze the Nyquist plots obtained from the EIS measurements and compare the equivalent circuit parameters calculated by LEBISDI with the corresponding original circuit parameters to assess the accuracy of the program developed. Calibration studies show that LEBISDI not only interpreted the simulated and circuitelement data accurately, but also successfully interpreted tissues impedance data and estimated the capacitive and resistive components produced by the compositions biological cells. Finally, LEBISDI efficiently calculated and analyzed variation in bioimpedance parameters of different tissue compositions, health and temperatures. LEBISDI can also be used for human tissue

  17. A LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) for biological tissue impedance analysis and equivalent circuit modelling

    KAUST Repository

    Bera, Tushar Kanti; Jampana, Nagaraju; Lubineau, Gilles

    2016-01-01

    Under an alternating electrical signal, biological tissues produce a complex electrical bioimpedance that is a function of tissue composition and applied signal frequencies. By studying the bioimpedance spectra of biological tissues over a wide range of frequencies, we can noninvasively probe the physiological properties of these tissues to detect possible pathological conditions. Electrical impedance spectroscopy (EIS) can provide the spectra that are needed to calculate impedance parameters within a wide range of frequencies. Before impedance parameters can be calculated and tissue information extracted, impedance spectra should be processed and analyzed by a dedicated software program. National Instruments (NI) Inc. offers LabVIEW, a fast, portable, robust, user-friendly platform for designing dataanalyzing software. We developed a LabVIEW-based electrical bioimpedance spectroscopic data interpreter (LEBISDI) to analyze the electrical impedance spectra for tissue characterization in medical, biomedical and biological applications. Here, we test, calibrate and evaluate the performance of LEBISDI on the impedance data obtained from simulation studies as well as the practical EIS experimentations conducted on electronic circuit element combinations and the biological tissue samples. We analyze the Nyquist plots obtained from the EIS measurements and compare the equivalent circuit parameters calculated by LEBISDI with the corresponding original circuit parameters to assess the accuracy of the program developed. Calibration studies show that LEBISDI not only interpreted the simulated and circuitelement data accurately, but also successfully interpreted tissues impedance data and estimated the capacitive and resistive components produced by the compositions biological cells. Finally, LEBISDI efficiently calculated and analyzed variation in bioimpedance parameters of different tissue compositions, health and temperatures. LEBISDI can also be used for human tissue

  18. Fabrication of a tissue-equivalent torso phantom for intercalibration of in-vivo transuranic-nuclide counting facilities

    International Nuclear Information System (INIS)

    Griffith, R.V.; Dean, P.N.; Anderson, A.L.; Fisher, J.C.

    1978-01-01

    A tissue-equivalent human-torso phantom has been constructed for calibration of the counting systems used for in-vivo measurement of transuranic nuclides. The phantom contains a human male rib cage, removable model organs, and includes tissue-equivalent chest plates that can be placed over the torso to simulate people with a wide range of statures. The organs included are lungs, heart, liver, kidneys, spleen, and tracheo-bronchial lymph nodes. Polyurethane with different concentrations of calcium carbonate was used to simulate the linear photon-attenuation properties of various human tissues--lean muscle, adipose-muscle mixtures, and cartilage. Foamed polyurethane with calcium carbonate simulates lung tissue. Transuranic isotopes can be incorporated uniformly in the phantom's lungs and other polyurethane-based organs by dissolution of the nitrate form in acetone with lanthanum nitrate carrier. Organs have now been labelled with highly pure 238 Pu, 239 Pu, and 241 Am for calibration measurements. This phantom is the first of three that will be used in a U.S. Department of Energy program of intercomparisons involving more than ten laboratories. The results of the intercomparison will allow participating laboratories to prepare sets of transmission curves that can be used to predict the performance of their counting systems for a wide range of subject builds and organ depositions. The intercomparison will also provide valuable information on the relative performance of a variety of detector systems and counting techniques

  19. Water equivalence of some plastic-water phantom materials for clinical proton beam dosimetry

    International Nuclear Information System (INIS)

    Al-Sulaiti, L.; Shipley, D.; Thomas, R.; Owen, P.; Kacperek, A.; Regan, P.H.; Palmans, H.

    2012-01-01

    Plastic-water phantom materials are not exactly water equivalent since they have a different elemental composition and different interaction cross sections for protons than water. Several studies of the water equivalence of plastic-water phantom materials have been reported for photon and electron beams, but none for clinical proton beams. In proton beams, the difference between non-elastic nuclear interactions in plastic-water phantom materials compared to those in water should be considered. In this work, the water equivalence of Plastic Water ® (PW) 1 , Plastic Water ® Diagnostic Therapy (PWDT) 1 and solid water (WT1) 2 phantoms was studied for clinical proton energies of 60 MeV and 200 MeV. This was done by evaluating the fluence correction factor at equivalent depths; first with respect to water and then with respect to graphite by experiment and Monte Carlo (MC) simulations using FLUKA. MC simulations showed that the fluence correction with respect to water was less than 0.5% up to the entire penetration depth of the protons at 60 MeV and less than 1% at 200 MeV up to 20 cm depth for PWDT, PW and WT1. With respect to graphite the fluence correction was about 0.5% for 60 MeV and about 4% for 200 MeV. The experimental results for modulated and un-modulated 60 MeV proton beams showed good agreement with the MC simulated fluence correction factors with respect to graphite deviating less than 1% from unity for the three plastic-water phantoms. - Highlights: ► We study plastic-water in clinical proton beams by experiment and Monte Carlo. ► We obtain fluence correction factors for water and graphite. ► The correction factor for water was close to 1 at 60 MeV and <0.990 at 200 MeV. ► The correction factor for graphite was ∼0.5% at 60 MeV and up to 4% at 200 MeV.

  20. Development of Equivalent Material Properties of Microbump for Simulating Chip Stacking Packaging

    Directory of Open Access Journals (Sweden)

    Chang-Chun Lee

    2015-08-01

    Full Text Available three-dimensional integrated circuit (3D-IC structure with a significant scale mismatch causes difficulty in analytic model construction. This paper proposes a simulation technique to introduce an equivalent material composed of microbumps and their surrounding wafer level underfill (WLUF. The mechanical properties of this equivalent material, including Young’s modulus (E, Poisson’s ratio, shear modulus, and coefficient of thermal expansion (CTE, are directly obtained by applying either a tensile load or a constant displacement, and by increasing the temperature during simulations, respectively. Analytic results indicate that at least eight microbumps at the outermost region of the chip stacking structure need to be considered as an accurate stress/strain contour in the concerned region. In addition, a factorial experimental design with analysis of variance is proposed to optimize chip stacking structure reliability with four factors: chip thickness, substrate thickness, CTE, and E-value. Analytic results show that the most significant factor is CTE of WLUF. This factor affects microbump reliability and structural warpage under a temperature cycling load and high-temperature bonding process. WLUF with low CTE and high E-value are recommended to enhance the assembly reliability of the 3D-IC architecture.

  1. Tribological behaviour of skin equivalents and ex-vivo human skin against the material components of artificial turf in sliding

    NARCIS (Netherlands)

    Morales Hurtado, Marina; Peppelman, P.; Zeng, Xiangqiong; van Erp, P.E.J.; van der Heide, Emile

    2016-01-01

    This research aims to analyse the interaction of three artificial skin equivalents and human skin against the main material components of artificial turf. The tribological performance of Lorica, Silicone Skin L7350 and a recently developed Epidermal Skin Equivalent (ESE) were studied and compared to

  2. The water equivalence of solid materials used for dosimetry with small proton beams

    International Nuclear Information System (INIS)

    Schneider, Uwe; Pemler, Peter; Besserer, Juergen; Dellert, Matthias; Moosburger, Martin; Boer, Jorrit de; Pedroni, Eros; Boehringer, Terence

    2002-01-01

    Various solid materials are used instead of water for absolute dosimetry with small proton beams. This may result in a dose measurement different to that in water, even when the range of protons in the phantom material is considered correctly. This dose difference is caused by the diverse cross sections for inelastic nuclear scattering in water and in the phantom materials respectively. To estimate the magnitude of this effect, flux and dose measurements with a 177 MeV proton pencil beam having a width of 0.6 cm (FWHM) were performed. The proton flux and the deposited dose in the beam path were determined behind water, lucite, polyethylene, teflon, and aluminum of diverse thicknesses. The number of out-scattered protons due to inelastic nuclear scattering was determined for water and the different materials. The ratios of the number of scattered protons in the materials relative to that in water were found to be 1.20 for lucite, 1.16 for polyethylene, 1.22 for teflon, and 1.03 for aluminum. The difference between the deposited dose in water and in the phantom materials taken in the center of the proton pencil beam, was estimated from the flux measurements, always taking the different ranges of protons in the materials into account. The estimated dose difference relative to water in 15 cm water equivalent thickness was -2.3% for lucite, -1.7% for polyethylene, -2.5% for teflon, and -0.4% for aluminum. The dose deviation was verified by a measurement using an ionization chamber. It should be noted that the dose error is larger when the effective point of measurement in the material is deeper or when the energy is higher

  3. Artificial implant materials - role of biomaterials in the tissue engineering

    International Nuclear Information System (INIS)

    Lewandowska-Szumiel, M.

    2007-01-01

    Lecture presents different materials applicable in production of implants. All these materials should be sterilized, however some of them can be modified using by irradiation (e.g. polymers). Numerous examples of tissue engineering are presented

  4. Low technology tissue culture materials for initiation and ...

    African Journals Online (AJOL)

    Low technology tissue culture materials for initiation and multiplication of banana plants. ... African Crop Science Journal ... locally available macronutrients, micronutrients, sugar, equipment and facility reduced the cost of consumable material

  5. [Strategies to choose scaffold materials for tissue engineering].

    Science.gov (United States)

    Gao, Qingdong; Zhu, Xulong; Xiang, Junxi; Lü, Yi; Li, Jianhui

    2016-02-01

    Current therapies of organ failure or a wide range of tissue defect are often not ideal. Transplantation is the only effective way for long time survival. But it is hard to meet huge patients demands because of donor shortage, immune rejection and other problems. Tissue engineering could be a potential option. Choosing a suitable scaffold material is an essential part of it. According to different sources, tissue engineering scaffold materials could be divided into three types which are natural and its modified materials, artificial and composite ones. The purpose of tissue engineering scaffold is to repair the tissues or organs damage, so could reach the ideal recovery in its function and structure aspect. Therefore, tissue engineering scaffold should even be as close as much to the original tissue or organs in function and structure. We call it "organic scaffold" and this strategy might be the drastic perfect substitute for the tissues or organs in concern. Optimized organization with each kind scaffold materials could make up for biomimetic structure and function of the tissue or organs. Scaffold material surface modification, optimized preparation procedure and cytosine sustained-release microsphere addition should be considered together. This strategy is expected to open new perspectives for tissue engineering. Multidisciplinary approach including material science, molecular biology, and engineering might find the most ideal tissue engineering scaffold. Using the strategy of drawing on each other strength and optimized organization with each kind scaffold material to prepare a multifunctional biomimetic tissue engineering scaffold might be a good method for choosing tissue engineering scaffold materials. Our research group had differentiated bone marrow mesenchymal stem cells into bile canaliculi like cells. We prepared poly(L-lactic acid)/poly(ε-caprolactone) biliary stent. The scaffold's internal played a part in the long-term release of cytokines which

  6. Water equivalence of various materials for clinical proton dosimetry by experiment and Monte Carlo simulation

    International Nuclear Information System (INIS)

    Al-Sulaiti, Leena; Shipley, David; Thomas, Russell; Kacperek, Andrzej; Regan, Patrick; Palmans, Hugo

    2010-01-01

    The accurate conversion of dose to various materials used in clinical proton dosimetry to dose-to-water is based on fluence correction factors, accounting for attenuation of primary protons and production of secondary particles due to non-elastic nuclear interactions. This work aims to investigate the depth dose distribution and the fluence correction with respect to water or graphite at water equivalent depths (WED) in different target materials relevant for dosimetry such as polymethyl methacrylate (PMMA), graphite, A-150, aluminium and copper at 60 and 200 MeV. This was done through a comparison between Monte Carlo simulation using MCNPX 2.5.0, analytical model calculations and experimental measurements at Clatterbridge Centre of Oncology (CCO) in a 60 MeV modulated and un-modulated proton beam. MCNPX simulations indicated small fluence corrections for all materials with respect to graphite and water in 60 and 200 MeV except for aluminium. The analytical calculations showed an increase in the fluence correction factor to a few percent for all materials with respect to water at 200 MeV. The experimental measurements for 60 MeV un-modulated beam indicated a good agreement with MCNPX. For the modulated beam the fluence correction factor was found to be decreasing below unity by up to few percent with depth for aluminium and copper but almost constant and unity for A-150.

  7. Study of the equivalent dose distribution in organs and tissues using periapical odontological radiography

    International Nuclear Information System (INIS)

    Santos, H.F.S.; Cipeli, J.F.; Fortes, M.A.B.; Federico, C.A.

    2017-01-01

    In this article presents a study of the doses obtained in periapical odontological radiography in main tissues of the head, using thermoluminescent dosemeters of type TLD-700H applied to a anthropomorphic simulator. The results indicate that the skin and salivary glands received the highest doses and the risk of calculated injury was 1.44 x 10 -6 Sv -1 per radiograph

  8. ORION: a computer code for evaluating environmental concentrations and dose equivalent to human organs or tissue from airborne radionuclides

    International Nuclear Information System (INIS)

    Shinohara, K.; Nomura, T.; Iwai, M.

    1983-05-01

    The computer code ORION has been developed to evaluate the environmental concentrations and the dose equivalent to human organs or tissue from air-borne radionuclides released from multiple nuclear installations. The modified Gaussian plume model is applied to calculate the dispersion of the radionuclide. Gravitational settling, dry deposition, precipitation scavenging and radioactive decay are considered to be the causes of depletion and deposition on the ground or on vegetation. ORION is written in the FORTRAN IV language and can be run on IBM 360, 370, 303X, 43XX and FACOM M-series computers. 8 references, 6 tables

  9. Effect of lunar materials on plant tissue culture.

    Science.gov (United States)

    Walkinshaw, C. H.; Venketeswaran, S.; Baur, P. S.; Croley, T. E.; Scholes, V. E.; Weete, J. D.; Halliwell, R. S.; Hall, R. H.

    1973-01-01

    Lunar material collected during the Apollo 11, 12, 14, and 15 missions has been used to treat 12 species of higher plant tissue cultures. Biochemical and morphological studies have been conducted on several of these species. Tobacco tissue cultures treated with 0.22 g of lunar material exhibited increased greening more complex chloroplasts, less cytoplasmic vacuolation and greater vesiculation. Pine tissue cultures reacted to treatment by an increased deposition of tannin-like materials. The percentage of dry weight and soluble protein was increased in cultures treated with either lunar or terrestrial rock materials.

  10. Electrospun Nanofibrous Materials for Neural Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Yee-Shuan Lee

    2011-02-01

    Full Text Available The use of biomaterials processed by the electrospinning technique has gained considerable interest for neural tissue engineering applications. The tissue engineering strategy is to facilitate the regrowth of nerves by combining an appropriate cell type with the electrospun scaffold. Electrospinning can generate fibrous meshes having fiber diameter dimensions at the nanoscale and these fibers can be nonwoven or oriented to facilitate neurite extension via contact guidance. This article reviews studies evaluating the effect of the scaffold’s architectural features such as fiber diameter and orientation on neural cell function and neurite extension. Electrospun meshes made of natural polymers, proteins and compositions having electrical activity in order to enhance neural cell function are also discussed.

  11. Development of a tissue-engineered human oral mucosa equivalent based on an acellular allogeneic dermal matrix: a preliminary report of clinical application to burn wounds.

    Science.gov (United States)

    Iida, Takuya; Takami, Yoshihiro; Yamaguchi, Ryo; Shimazaki, Shuji; Harii, Kiyonori

    2005-01-01

    Tissue-engineered skin equivalents composed of epidermal and dermal components have been widely investigated for coverage of full-thickness skin defects. We developed a tissue-engineered oral mucosa equivalent based on an acellular allogeneic dermal matrix and investigated its characteristics. We also tried and assessed its preliminary clinical application. Human oral mucosal keratinocytes were separated from a piece of oral mucosa and cultured in a chemically-defined medium. The keratinocytes were seeded on to the acellular allogeneic dermal matrix and cultured. Histologically, the mucosa equivalent had a well-stratified epithelial layer. Immunohistochemical study showed that it was similar to normal oral mucosa. We applied this equivalent in one case with an extensive burn wound. The equivalent was transplanted three weeks after the harvest of the patient's oral mucosa and about 30% of the graft finally survived. We conclude that this new oral mucosa equivalent could become a therapeutic option for the treatment of extensive burns.

  12. Effect of chest wall radiotherapy in different manners using tissue equivalent bolus on skin and lung of cavia cobayas

    International Nuclear Information System (INIS)

    Huang Wei; Qu Yaqin; Song Xiangfu; Liu Shixin; Jia Xiaojing; Guo He; Yang Lei

    2009-01-01

    Objective: To probe the influence of electron beam radiotherapy in different manners using different tissue equivalent boluses on skin and lung. Methods: Adult female cavia cobayas were randomly divided into four groups as control group, half-time with bolus group, half-time with bolus group and without bolus group. Acute-irradiation animal models were established using electron beam in different manners with or without 0.5 cm tissue equivalent bolus. Pathological changes in lung, hair vesicle and fibroblast cell count were analyzed 40 clays after irradiation. Results: The radiation dermatitis in the group with bolus was slighter than that of the group without bolus, but the radiation pneumonia was reverse. With bolus, the radiation dermatitis of haft-time group was slighter than that of full-time group. The injury repair of half-time group was more active than full-time group. Conclusions: The treatment of haft-time bolus could protect lung without serious skin complications. (authors)

  13. A new formula for normal tissue complication probability (NTCP) as a function of equivalent uniform dose (EUD).

    Science.gov (United States)

    Luxton, Gary; Keall, Paul J; King, Christopher R

    2008-01-07

    To facilitate the use of biological outcome modeling for treatment planning, an exponential function is introduced as a simpler equivalent to the Lyman formula for calculating normal tissue complication probability (NTCP). The single parameter of the exponential function is chosen to reproduce the Lyman calculation to within approximately 0.3%, and thus enable easy conversion of data contained in empirical fits of Lyman parameters for organs at risk (OARs). Organ parameters for the new formula are given in terms of Lyman model m and TD(50), and conversely m and TD(50) are expressed in terms of the parameters of the new equation. The role of the Lyman volume-effect parameter n is unchanged from its role in the Lyman model. For a non-homogeneously irradiated OAR, an equation relates d(ref), n, v(eff) and the Niemierko equivalent uniform dose (EUD), where d(ref) and v(eff) are the reference dose and effective fractional volume of the Kutcher-Burman reduction algorithm (i.e. the LKB model). It follows in the LKB model that uniform EUD irradiation of an OAR results in the same NTCP as the original non-homogeneous distribution. The NTCP equation is therefore represented as a function of EUD. The inverse equation expresses EUD as a function of NTCP and is used to generate a table of EUD versus normal tissue complication probability for the Emami-Burman parameter fits as well as for OAR parameter sets from more recent data.

  14. A new formula for normal tissue complication probability (NTCP) as a function of equivalent uniform dose (EUD)

    International Nuclear Information System (INIS)

    Luxton, Gary; Keall, Paul J; King, Christopher R

    2008-01-01

    To facilitate the use of biological outcome modeling for treatment planning, an exponential function is introduced as a simpler equivalent to the Lyman formula for calculating normal tissue complication probability (NTCP). The single parameter of the exponential function is chosen to reproduce the Lyman calculation to within ∼0.3%, and thus enable easy conversion of data contained in empirical fits of Lyman parameters for organs at risk (OARs). Organ parameters for the new formula are given in terms of Lyman model m and TD 50 , and conversely m and TD 50 are expressed in terms of the parameters of the new equation. The role of the Lyman volume-effect parameter n is unchanged from its role in the Lyman model. For a non-homogeneously irradiated OAR, an equation relates d ref , n, v eff and the Niemierko equivalent uniform dose (EUD), where d ref and v eff are the reference dose and effective fractional volume of the Kutcher-Burman reduction algorithm (i.e. the LKB model). It follows in the LKB model that uniform EUD irradiation of an OAR results in the same NTCP as the original non-homogeneous distribution. The NTCP equation is therefore represented as a function of EUD. The inverse equation expresses EUD as a function of NTCP and is used to generate a table of EUD versus normal tissue complication probability for the Emami-Burman parameter fits as well as for OAR parameter sets from more recent data

  15. Evaluation of brain tissue applying equivalent cross-relaxation rate using MRI

    International Nuclear Information System (INIS)

    Obata, Hideaki; Inaba, Tadashi; Tokuda, Masataka; Matsushima, Shigeru; Kinosada, Yasutomi

    2003-01-01

    The equivalent cross-relaxation rate (ECR) is a measurement method that can evaluate a change in organization structure quantitatively utilizing MRI. The goal of this study is to discover a parameter that we can use to evaluate aging of the human brain using ECR. Fourteen patients diagnosed with diseases other than those located in the cranium were imaged using a SIGNA model of GE Medical Systems equipped with a 1.5 T clinical scanner. The ECR values were defined as the percentage of signal loss between unsaturated and saturated images. It was found that the ECR value of gray matter was lower than subcortical white matter. At ages under 70 years old, the mean of ECR values of subcortical white matter showed stable values with insignificant variance. Furthermore, there was no correlation between age and ECR value of every region calculated. On the other hand, it was found that there was a negative correlation for the ECR values of subcortical white matter and gray matter at ages slightly over 70 years old. It is possible that the reduction in ECR value shows demyelination by aging in the senium. When the offset frequency is near the water resonance frequency, the ECR values mean information about neurocytes. Accordingly, the ECR (320)/ECR (1200) value probably shows that information is related to the amount or activity of neurons. (author)

  16. Optical coherence tomography detection of shear wave propagation in inhomogeneous tissue equivalent phantoms and ex-vivo carotid artery samples

    Science.gov (United States)

    Razani, Marjan; Luk, Timothy W.H.; Mariampillai, Adrian; Siegler, Peter; Kiehl, Tim-Rasmus; Kolios, Michael C.; Yang, Victor X.D.

    2014-01-01

    In this work, we explored the potential of measuring shear wave propagation using optical coherence elastography (OCE) in an inhomogeneous phantom and carotid artery samples based on a swept-source optical coherence tomography (OCT) system. Shear waves were generated using a piezoelectric transducer transmitting sine-wave bursts of 400 μs duration, applying acoustic radiation force (ARF) to inhomogeneous phantoms and carotid artery samples, synchronized with a swept-source OCT (SS-OCT) imaging system. The phantoms were composed of gelatin and titanium dioxide whereas the carotid artery samples were embedded in gel. Differential OCT phase maps, measured with and without the ARF, detected the microscopic displacement generated by shear wave propagation in these phantoms and samples of different stiffness. We present the technique for calculating tissue mechanical properties by propagating shear waves in inhomogeneous tissue equivalent phantoms and carotid artery samples using the ARF of an ultrasound transducer, and measuring the shear wave speed and its associated properties in the different layers with OCT phase maps. This method lays the foundation for future in-vitro and in-vivo studies of mechanical property measurements of biological tissues such as vascular tissues, where normal and pathological structures may exhibit significant contrast in the shear modulus. PMID:24688822

  17. Nonlinear ultrasound propagation through layered liquid and tissue-equivalent media: computational and experimental results at high frequency

    International Nuclear Information System (INIS)

    Williams, Ross; Cherin, Emmanuel; Lam, Toby Y J; Tavakkoli, Jahangir; Zemp, Roger J; Foster, F Stuart

    2006-01-01

    Nonlinear propagation has been demonstrated to have a significant impact on ultrasound imaging. An efficient computational algorithm is presented to simulate nonlinear ultrasound propagation through layered liquid and tissue-equivalent media. Results are compared with hydrophone measurements. This study was undertaken to investigate the role of nonlinear propagation in high frequency ultrasound micro-imaging. The acoustic field of a focused transducer (20 MHz centre frequency, f-number 2.5) was simulated for layered media consisting of water and tissue-mimicking phantom, for several wide-bandwidth source pulses. The simulation model accounted for the effects of diffraction, attenuation and nonlinearity, with transmission and refraction at layer boundaries. The parameter of nonlinearity, B/A, of the water and tissue-mimicking phantom were assumed to be 5.2 and 7.4, respectively. The experimentally measured phantom B/A value found using a finite-amplitude insert-substitution method was shown to be 7.4 ± 0.6. Relative amounts of measured second and third harmonic pressures as a function of the fundamental pressures at the focus were in good agreement with simulations. Agreement within 3% was found between measurements and simulations of the beam widths of the fundamental and second harmonic signals following propagation through the tissue phantom. The results demonstrate significant nonlinear propagation effects for high frequency imaging beams

  18. Characterization of tissues equivalent to the human body by the Monte Carlo method for X-rays; Caracterizacion de tejidos equivalentes al cuerpo humano mediante el metodo Monte Carlo para rayos X

    Energy Technology Data Exchange (ETDEWEB)

    Vega R, J.; Huamani T, Y.; Mullisaca P, A. F.; Yauri C, L., E-mail: josevegaramirez@yahoo.es [Universidad Nacional de San Agustin de Arequipa, Av. Independencia s/n, 04000 Arequipa (Peru)

    2017-10-15

    There is a need to have materials equivalent to the human body that have the appropriate characteristics to be used as a substitute tissue in the clinical practices of radio-diagnosis, radiotherapy. In Arequipa, Peru, there are two health centers in radiotherapy applications, one with a Theratron Co-60 gamma irradiator and another with Elekta Linac; the Medical Physics Area of the School of Physics of the National University of San Agustin de Arequipa, were four equivalent materials based on epoxy resin, phenolitic spheres, calcium carbonate, etc. were built, such as bone tissue, soft tissue, adipose and lung tissue compared with water, whit the purpose of studying and applying them in future clinical applications. In this work we describe its physical and dosimetric characterization to determine its use as an equivalent material or manikin. The materials are 1 cm thick and 30 cm in diameter, the materials are non-malleable solids, they do not degrade, they have stability in their consistency due to temperature and irradiation, they are not toxic in their use, determining densities from 0.32 g/cm{sup 3} for the lung tissue to 1.8 g/cm{sup 3} for the bone material. These materials were analyzed by scanning electron microscopy, giving the percentages by weight of the elements found to determine their effective atomic number, the physical analysis to determine their mass absorption and energy coefficients, which were studied for energy photons between 1 KeV at 20 MeV. The simulation of the equivalent materials and the physical and dosimetric study were found using the code Penelope 2008 Monte Carlo method and validated by the Nist database. The results obtained according to their coefficients of mass attenuation of each material, show lung, bone, soft and adipose tissue with differences with respect to the same Nist materials. The range maximum and minimum Rd deviation found was 35.65 - 3.16 for bone, 28.5 - 6.74 for lung, 33.78 - 9.06 for soft tissue and 86.42 - 1

  19. Water equivalent thickness values of materials used in beams of protons, helium, carbon and iron ions.

    Science.gov (United States)

    Zhang, Rui; Taddei, Phillip J; Fitzek, Markus M; Newhauser, Wayne D

    2010-05-07

    Heavy charged particle beam radiotherapy for cancer is of increasing interest because it delivers a highly conformal radiation dose to the target volume. Accurate knowledge of the range of a heavy charged particle beam after it penetrates a patient's body or other materials in the beam line is very important and is usually stated in terms of the water equivalent thickness (WET). However, methods of calculating WET for heavy charged particle beams are lacking. Our objective was to test several simple analytical formulas previously developed for proton beams for their ability to calculate WET values for materials exposed to beams of protons, helium, carbon and iron ions. Experimentally measured heavy charged particle beam ranges and WET values from an iterative numerical method were compared with the WET values calculated by the analytical formulas. In most cases, the deviations were within 1 mm. We conclude that the analytical formulas originally developed for proton beams can also be used to calculate WET values for helium, carbon and iron ion beams with good accuracy.

  20. Measurement of characteristic prompt gamma rays emitted from oxygen and carbon in tissue-equivalent samples during proton beam irradiation.

    Science.gov (United States)

    Polf, Jerimy C; Panthi, Rajesh; Mackin, Dennis S; McCleskey, Matt; Saastamoinen, Antti; Roeder, Brian T; Beddar, Sam

    2013-09-07

    The purpose of this work was to characterize how prompt gamma (PG) emission from tissue changes as a function of carbon and oxygen concentration, and to assess the feasibility of determining elemental concentration in tissues irradiated with proton beams. For this study, four tissue-equivalent water-sucrose samples with differing densities and concentrations of carbon, hydrogen, and oxygen were irradiated with a 48 MeV proton pencil beam. The PG spectrum emitted from each sample was measured using a high-purity germanium detector, and the absolute detection efficiency of the detector, average beam current, and delivered dose distribution were also measured. Changes to the total PG emission from (12)C (4.44 MeV) and (16)O (6.13 MeV) per incident proton and per Gray of absorbed dose were characterized as a function of carbon and oxygen concentration in the sample. The intensity of the 4.44 MeV PG emission per incident proton was found to be nearly constant for all samples regardless of their carbon concentration. However, we found that the 6.13 MeV PG emission increased linearly with the total amount (in grams) of oxygen irradiated in the sample. From the measured PG data, we determined that 1.64 × 10(7) oxygen PGs were emitted per gram of oxygen irradiated per Gray of absorbed dose delivered with a 48 MeV proton beam. These results indicate that the 6.13 MeV PG emission from (16)O is proportional to the concentration of oxygen in tissue irradiated with proton beams, showing that it is possible to determine the concentration of oxygen within tissues irradiated with proton beams by measuring (16)O PG emission.

  1. Analysis of Deformation and Equivalent Stress during Biomass Material Compression Molding

    Science.gov (United States)

    Xu, Guiying; Wei, Hetao; Zhang, Zhien; Yu, Shaohui; Wang, Congzhe; Huang, Guowen

    2018-02-01

    Ansys is adopted to analyze mold deformation and stress field distribution rule during the process of compressing biomass under pressure of 20Mpa. By means of unit selection, material property setting, mesh partition, contact pair establishment, load and constraint applying, and solver setting, the stress and strain of overall mold are analyzed. Deformation and equivalent Stress of compression structure, base, mold, and compression bar were analyzed. We can have conclusions: The distribution of stress forced on compressor is not completely uniform, where the stress at base is slightly decreased; the stress and strain of compression bar is the largest, and stress concentration my occur at top of compression bar, which goes against compression bar service life; the overall deformation of main mold is smaller; although there is slight difference between upper and lower part, the overall variation is not obvious, but the stress difference between upper and lower part of main mold is extremely large so that reaches to 10 times; the stress and strain in base decrease in circular shape, but there is still stress concentration in ledge, which goes against service life; contact stress does not distribute uniformly, there is increasing or decreasing trend in adjacent parts, which is very large in some parts. in constructing both.

  2. Realisation and qualification of a tissue equivalent proportional counter with a multi-cellular geometry for the individual neutron dosimetry

    International Nuclear Information System (INIS)

    Hoflack, Ch.

    1999-01-01

    The present day dosimetry means for radiations with a strong ionization density cannot fulfill the future radioprotection regulations which will require an individual dosimetry with active dosemeters. The aim of this work is the study and development of an individual dosemeter based on a tissue equivalent proportional counter and with a multi-cellular geometry allowing to reach a sensibility equivalent to environmental dosemeters. A pressure regulation bench has been added to the detector in order to reduce the degassing of the detector parts and to reach a sufficient service life for the implementation of the characterization tests. The hole counter system has been adopted for the first prototypes in order to reduce the sensibility of the wires multiplication system with respect to mechanical vibrations. Tests performed with an internal alpha source have shown that a better electrical efficiency can be reached when more severe mechanical limits are adopted during the construction. The dose equivalent response of the prototype for mono-energy neutrons of 144 keV to 2.5 MeV is analyzed experimentally and by simulation. During experiments with normal incidence neutrons, the prototype fulfills the requirements of the CEI N O 1323 standard for energies comprised between 400 keV and 2.5 MeV, while the simulation indicates a satisfactory response up to 200 keV. A preliminary study of the behaviour of the detector with respect to the neutrons incidence indicates that the multi-cellular geometry is efficient for large angles (the sensibility of the prototype is increased by a factor 3). Finally, simulation studies have to be made to optimize the electrical operation and the geometry of the next prototype. (J.S.)

  3. A new Monte Carlo program for calculations of dose distributions within tissue equivalent phantoms irradiated from π--meson beams

    International Nuclear Information System (INIS)

    Przybilla, G.

    1980-11-01

    The present paper reports on the structure and first results from a new Monte Carlo programme for calculations of energy distributions within tissue equivalent phantoms irradiated from π - -beams. Each pion or generated secondary particle is transported until to the complete loss of its kinetic energy taking into account pion processes like multiple Coulomb scattering, pion reactions in flight and absorption of stopped pions. The code uses mainly data from experiments, and physical models have been added only in cases of lacking data. Depth dose curves for a pensil beam of 170 MeV/c within a water phantom are discussed as a function of various parameters. Isodose contours are plotted resulting from a convolution of an extended beam profile and the dose distribution of a pencil beams. (orig.) [de

  4. Peptide-Based Materials for Cartilage Tissue Regeneration.

    Science.gov (United States)

    Hastar, Nurcan; Arslan, Elif; Guler, Mustafa O; Tekinay, Ayse B

    2017-01-01

    Cartilaginous tissue requires structural and metabolic support after traumatic or chronic injuries because of its limited capacity for regeneration. However, current techniques for cartilage regeneration are either invasive or ineffective for long-term repair. Developing alternative approaches to regenerate cartilage tissue is needed. Therefore, versatile scaffolds formed by biomaterials are promising tools for cartilage regeneration. Bioactive scaffolds further enhance the utility in a broad range of applications including the treatment of major cartilage defects. This chapter provides an overview of cartilage tissue, tissue defects, and the methods used for regeneration, with emphasis on peptide scaffold materials that can be used to supplement or replace current medical treatment options.

  5. Material parameter identification and inverse problems in soft tissue biomechanics

    CERN Document Server

    Evans, Sam

    2017-01-01

    The articles in this book review hybrid experimental-computational methods applied to soft tissues which have been developed by worldwide specialists in the field. People developing computational models of soft tissues and organs will find solutions for calibrating the material parameters of their models; people performing tests on soft tissues will learn what to extract from the data and how to use these data for their models and people worried about the complexity of the biomechanical behavior of soft tissues will find relevant approaches to address this complexity.

  6. Skin equivalent tissue-engineered construct: co-cultured fibroblasts/ keratinocytes on 3D matrices of sericin hope cocoons.

    Directory of Open Access Journals (Sweden)

    Sunita Nayak

    Full Text Available The development of effective and alternative tissue-engineered skin replacements to autografts, allografts and xenografts has became a clinical requirement due to the problems related to source of donor tissue and the perceived risk of disease transmission. In the present study 3D tissue engineered construct of sericin is developed using co-culture of keratinocytes on the upper surface of the fabricated matrices and with fibroblasts on lower surface. Sericin is obtained from "Sericin Hope" silkworm of Bombyx mori mutant and is extracted from cocoons by autoclave. Porous sericin matrices are prepared by freeze dried method using genipin as crosslinker. The matrices are characterized biochemically and biophysically. The cell proliferation and viability of co-cultured fibroblasts and keratinocytes on matrices for at least 28 days are observed by live/dead assay, Alamar blue assay, and by dual fluorescent staining. The growth of the fibroblasts and keratinocytes in co-culture is correlated with the expression level of TGF-β, b-FGF and IL-8 in the cultured supernatants by enzyme-linked immunosorbent assay. The histological analysis further demonstrates a multi-layered stratified epidermal layer of uninhibited keratinocytes in co-cultured constructs. Presence of involucrin, collagen IV and the fibroblast surface protein in immuno-histochemical stained sections of co-cultured matrices indicates the significance of paracrine signaling between keratinocytes and fibroblasts in the expression of extracellular matrix protein for dermal repair. No significant amount of pro inflammatory cytokines (TNF-α, IL-1β and nitric oxide production are evidenced when macrophages grown on the sericin matrices. The results all together depict the potentiality of sericin 3D matrices as skin equivalent tissue engineered construct in wound repair.

  7. Influence of length of interval between pulses in PDR brachytherapy (PDRBT on value of Biologically Equivalent Dose (BED in healthy tissues

    Directory of Open Access Journals (Sweden)

    Tomasz Piotrowski

    2010-07-01

    Full Text Available Purpose: Different PDR treatment schemas are used in clinical practice, however optimal length of interval between pulses still remains unclear. The aim of this work was to compare value of BED doses measured in surrounded healthy tissues according to different intervals between pulses in PDRBT. Influence of doses optimization on BED values was analyzed.Material and methods: Fifty-one patients treated in Greater Poland Cancer Centre were qualified for calculations.Calculations of doses were made in 51 patients with head and neck cancer, brain tumor, breast cancer, sarcoma, penis cancer and rectal cancer. Doses were calculated with the use of PLATO planning system in chosen critical points in surrounded healthy tissues. For all treatment plans the doses were compared using Biologically Equivalent Dose formula.Three interval lengths (1, 2 and 4 hours between pulses were chosen for calculations. For statistical analysis Friedman ANOVA test and Kendall ratio were used.Results: The median value of BED in chosen critical points in healthy tissues was statistically related to the length of interval between PDR pulses and decreased exponentially with 1 hour interval to 4 hours (Kendall = from 0.48 to 1.0; p = from 0.002 to 0.00001.Conclusions: Prolongation of intervals between pulses in PDR brachytherapy was connected with lower values of BED doses in healthy tissues. It seems that longer intervals between pulses reduced the risk of late complications, but also decreased the tumour control. Furthermore, optimization influenced the increase of doses in healthy tissues.

  8. Early recognition of autonomous thyroid tissue by a combination of quantitative thyroid pertechnetate scintigraphy with the free T4 equivalent

    International Nuclear Information System (INIS)

    Joseph, K.; Mahlstedt, J.; Welcke, U.

    1980-01-01

    A suspicion of AFTT can be raised in 80% of still euthyroid patients by a combined evaluation of an equivalent to the free T 4 (FTE) and an equavilant to the clearance using a quantitative evaluation of the thyroid technetium scan (TcTU). The suppression test not only confirms the autonomy in a qualitative manner but also provides an estimate of the volume of autonomous tissue because The TcTU after suppression strictly correlates linearly with the volume of the AFTT. Since after iodine administration FTE increases proportionally to the volume of AFTT, the procedure can be of some prognostic value: those with autonomous tissue in excess of a critical volume will almost certainly develop hyperthyroidism following a certain minimum rate of iodine administration. A prospective study of patients under age 50 whose thyroids contained various amounts of AFTT has shown that prophylactic dietary iodine supplementation will not cause hyperthyroidism to develop provided the additional iodine intake does not exceed 100 μg per day. (orig./MG) [de

  9. Biomimetic Materials and Fabrication Approaches for Bone Tissue Engineering.

    Science.gov (United States)

    Kim, Hwan D; Amirthalingam, Sivashanmugam; Kim, Seunghyun L; Lee, Seunghun S; Rangasamy, Jayakumar; Hwang, Nathaniel S

    2017-12-01

    Various strategies have been explored to overcome critically sized bone defects via bone tissue engineering approaches that incorporate biomimetic scaffolds. Biomimetic scaffolds may provide a novel platform for phenotypically stable tissue formation and stem cell differentiation. In recent years, osteoinductive and inorganic biomimetic scaffold materials have been optimized to offer an osteo-friendly microenvironment for the osteogenic commitment of stem cells. Furthermore, scaffold structures with a microarchitecture design similar to native bone tissue are necessary for successful bone tissue regeneration. For this reason, various methods for fabricating 3D porous structures have been developed. Innovative techniques, such as 3D printing methods, are currently being utilized for optimal host stem cell infiltration, vascularization, nutrient transfer, and stem cell differentiation. In this progress report, biomimetic materials and fabrication approaches that are currently being utilized for biomimetic scaffold design are reviewed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. SU-F-T-517: Determining the Tissue Equivalence of a Brass Mesh Bolus in a Reconstructed Chest Wall Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shekel, E; Epstein, D; Levin, D [Dept of radiotherapy, Assuta Medical Centers, Tel Aviv (Israel)

    2016-06-15

    Purpose: To determine the tissue equivalence of a brass mesh bolus (RPD) in the setting of a reconstructed chest wall irradiation Methods: We measured breast skin dose delivered by a tangential field plan on an anthropomorphic phantom using Mosfet and nanoDot (Landauer) dosimeters in five different locations on the breast. We also measured skin dose using no bolus, 5mm and 10 mm superflab bolus. In the Eclipse treatment planning system (Varian, Palo Alto, CA) we calculated skin dose for different bolus thicknesses, ranging from 0 to 10 mm, in order to evaluate which calculation best matches the brass mesh measurements, as the brass mesh cannot be simulated due to artefacts.Finally, we measured depth dose behavior with the brass mesh bolus to verify that the bolus does not affect the dose to the breast itself beyond the build-up region. Results: Mosfet and nanoDot measurements were consistent with each other.As expected, skin dose measurements with no bolus had the least agreement with Eclipse calculation, while measurements for 5 and 10 mm agreed well with the calculation despite the difficulty in conforming superflab bolus to the breast contour. For the brass mesh the best agreement was for 3 mm bolus Eclipse calculation. For Mosfets, the average measurement was 90.8% of the expected dose, and for nanoDots 88.33% compared to 83.34%, 88.64% and 93.94% (2,3 and 5 mm bolus calculation respectively).The brass mesh bolus increased skin dose by approximately 25% but there was no dose increase beyond the build-up region. Conclusion: Brass mesh bolus is most equivalent to a 3 mm bolus, and does not affect the dose beyond the build-up region. The brass mesh cannot be directly calculated in Eclipse, hence a 3mm bolus calculation is a good reflection of the dose response to the brass mesh bolus.

  11. Method of tissue repair using a composite material

    Energy Technology Data Exchange (ETDEWEB)

    Hutchens, Stacy A.; Woodward, Jonathan; Evans, Barbara R.; O' Neill, Hugh M.

    2016-03-01

    A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

  12. Method of tissue repair using a composite material

    Science.gov (United States)

    Hutchens, Stacy A; Woodward, Jonathan; Evans, Barbara R; O'Neill, Hugh M

    2014-03-18

    A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

  13. 2,3,7,8-Tetrachlorodibenzo-p-dioxin equivalents in tissues of birds at Green Bay, Wisconsin, USA

    Science.gov (United States)

    Jones, Paul D.; Giesy, John P.; Newsted, John L.; Verbrugge, David A.; Beaver, Donald L.; Ankley, Gerald T.; Tillitt, Donald E.; Lodge, Keith B.; Niemi, Gerald J.

    1993-01-01

    The environment has become contaminated with complex mixtures of planar, chlorinated hydrocarbons (PCHs) such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and structurally similar compounds. Because the potencies of individual congeners to cause the same adverse effects vary greatly and the relative as well as absolute concentrations of individual PCH vary among samples from different locations, it is difficult to assess the toxic effects of these mixtures on wildlife. These compounds can cause a number of adverse effects, however, because the toxic effects which occur at ecologically-relevant concentrations such as embryo-lethality and birth defects appear to be mediated through the same mechanism, the potency of individual congeners can be reported relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) which is the most toxic congener in the PCH class. The concentations of 2,3,7,8-TCDD Equivalents (TCDD-EQ) were determined in the tissues of aquatic and terrestrial birds of Green Bay, Wisconsin by the H4IIE bioassay system and compared toxic equivalency factors (TEFs) with the concentration predicted by the use of toxic equivalency factors applied to concentrations of PCH, which were determined by instrumental analyses. Concentrations of TCDD-EQ ranged from 0.52 to 440 ng/kg, wet weight. The greatest concentrations occurred in the fish-eating birds. Concentrations of TCDD-EQ, which were determined by the two methods were significantly correlated, but the additive model which used the TEFs with concentrations of measured PCB, PCDD and PCDF congeners underestimated the concentrations of TCDD-EQ measured by the H4IIE bioassay by an average of 57%. This is thought to be due to contributions from un-quantified PCH, which are known to occur in the environment. Of the quantified PCH congeners, PCDD and PCDF contributed a small portion of the TCDD-EQ in the aquatic birds, while most of the

  14. Stem cell homing-based tissue engineering using bioactive materials

    Science.gov (United States)

    Yu, Yinxian; Sun, Binbin; Yi, Chengqing; Mo, Xiumei

    2017-06-01

    Tissue engineering focuses on repairing tissue and restoring tissue functions by employing three elements: scaffolds, cells and biochemical signals. In tissue engineering, bioactive material scaffolds have been used to cure tissue and organ defects with stem cell-based therapies being one of the best documented approaches. In the review, different biomaterials which are used in several methods to fabricate tissue engineering scaffolds were explained and show good properties (biocompatibility, biodegradability, and mechanical properties etc.) for cell migration and infiltration. Stem cell homing is a recruitment process for inducing the migration of the systemically transplanted cells, or host cells, to defect sites. The mechanisms and modes of stem cell homing-based tissue engineering can be divided into two types depending on the source of the stem cells: endogenous and exogenous. Exogenous stem cell-based bioactive scaffolds have the challenge of long-term culturing in vitro and for endogenous stem cells the biochemical signal homing recruitment mechanism is not clear yet. Although the stem cell homing-based bioactive scaffolds are attractive candidates for tissue defect therapies, based on in vitro studies and animal tests, there is still a long way before clinical application.

  15. Evolution of the Deep-space Galactic Cosmic Ray Lineal Energy Transfer Spectrum through Tissue Equivalent Plastic

    Science.gov (United States)

    Case, A. W.; Kasper, J. C.; Spence, H. E.; Golightly, M. J.; Schwadron, N. A.; Mazur, J. E.; Blake, J. B.; Looper, M. D.; Townsend, L.; Zeitlin, C. J.

    2011-12-01

    The Cosmic Ray Telescope for the Effects of Radiation is an energetic particle telescope that resides on the Lunar Reconnaissance Orbiter spacecraft, currently in a 50 km circular lunar polar orbit. The telescope consists of 6 silicon semi-conductor detectors placed in pairs that surround two pieces of Tissue Equivalent Plastic (TEP), which serve to absorb energy from particles as they transit through the instrument. Particles with energies greater than 12 MeV/nucleon can penetrate the outermost shield and be measured by the instrument. The primary measurement made by the instrument is of the Linear Energy Transfer (LET) of energetic particles as they transit through the telescope. CRaTER measures the LET spectrum with unprecedented energy resolution and has done so during a period of historically low solar activity that led to record high intensities of Galactic Cosmic Rays (GCR). These LET spectra are used to study changes in the properties of the incoming particles, and to make detailed measurements of the radiation doses human explorers will experience in deep space on missions to the moon, to asteroids, or to Mars. We present LET spectra accumulated during 2009 and 2010. We show how the LET spectrum evolves through the instrument as the GCR interact with the TEP. Due to the importance of these measurements for human effects, our extensive absolute calibration procedures are presented. Of particular note is a significant reduction in the flux of particles with LET greater than 10 keV/um for detectors that lie deeper within the telescope stack, due to the attenuation of high LET particles within the TEP. By measuring this attenuation we can estimate the depth in human tissue where the highest LET particles that are most likely to cause genetic damage pose the greatest threat to humans in space.

  16. Demineralized dentin matrix composite collagen material for bone tissue regeneration.

    Science.gov (United States)

    Li, Jianan; Yang, Juan; Zhong, Xiaozhong; He, Fengrong; Wu, Xiongwen; Shen, Guanxin

    2013-01-01

    Demineralized dentin matrix (DDM) had been successfully used in clinics as bone repair biomaterial for many years. However, particle morphology of DDM limited it further applications. In this study, DDM and collagen were prepared to DDM composite collagen material. The surface morphology of the material was studied by scanning electron microscope (SEM). MC3T3-E1 cells responses in vitro and tissue responses in vivo by implantation of DDM composite collagen material in bone defect of rabbits were also investigated. SEM analysis showed that DDM composite collagen material evenly distributed and formed a porous scaffold. Cell culture and animal models results indicated that DDM composite collagen material was biocompatible and could support cell proliferation and differentiation. Histological evaluation showed that DDM composite collagen material exhibited good biocompatibility, biodegradability and osteoconductivity with host bone in vivo. The results suggested that DDM composite collagen material might have a significant clinical advantage and potential to be applied in bone and orthopedic surgery.

  17. Establishing Substantial Equivalence: Transcriptomics

    Science.gov (United States)

    Baudo, María Marcela; Powers, Stephen J.; Mitchell, Rowan A. C.; Shewry, Peter R.

    Regulatory authorities in Western Europe require transgenic crops to be substantially equivalent to conventionally bred forms if they are to be approved for commercial production. One way to establish substantial equivalence is to compare the transcript profiles of developing grain and other tissues of transgenic and conventionally bred lines, in order to identify any unintended effects of the transformation process. We present detailed protocols for transcriptomic comparisons of developing wheat grain and leaf material, and illustrate their use by reference to our own studies of lines transformed to express additional gluten protein genes controlled by their own endosperm-specific promoters. The results show that the transgenes present in these lines (which included those encoding marker genes) did not have any significant unpredicted effects on the expression of endogenous genes and that the transgenic plants were therefore substantially equivalent to the corresponding parental lines.

  18. Thermoluminescence and radioluminescence properties of tissue equivalent Cu-doped Li2B4O7 for radiation dosimetry

    International Nuclear Information System (INIS)

    Cruz Z, E.; Furetta, C.; Marcazzo, J.; Santiago, M.; Guarneros, C.; Pacio, M.; Palomino, R.

    2015-10-01

    Thermoluminescence (Tl) and radioluminescence (Rl) properties of lithium tetraborate (Li 2 B 4 O 7 ) doped with different concentration of copper (0.25, 0.5, 1 wt %) under gamma and beta irradiation has been investigated. The feasibility of using this borate in radiation dosimetry at low doses has been evaluated. Tissue equivalent Li 2 B 4 O 7 was prepared by solid state reaction using mixing stoichiometric compositions of lithium carbonate (Li 2 CO 3 ) and boric acid (H 3 BO 3 ) and a solution of CuCl 2 as dopant. The glow curve, of the most efficient copper doped borate (Li 2 B 4 O 7 :Cu 0.5 wt %), shows a main stable peak centered at 225 degrees C and a second low temperature peak centered at 80 degrees C. The low temperature peak disappears completely after 24 hours of storage in darkness and at room temperature or after an annealing at 120 degrees C for 10 seconds. The main peak of the Li 2 B 4 O 7 :Cu remains constant. The Tl response of Li 2 B 4 O 7 :Cu shows good linearity in the analyzed dose range. The stability and repeatability of Rl signals of the borate have been studied and the Li 2 B 4 O 7 :Cu (0.5 wt %) shown the higher Rl emission and a stable and repetitive response. Results show that Li 2 B 4 O 7 :Cu has prospects to be used in gamma and beta radiation dosimetry. (Author)

  19. Supercritical carbon dioxide extracted extracellular matrix material from adipose tissue

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun Kit; Luo, Baiwen; Guneta, Vipra [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Li, Liang; Foo, Selin Ee Min [School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551 (Singapore); Dai, Yun; Tan, Timothy Thatt Yang [School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore); Tan, Nguan Soon [School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551 (Singapore); Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, 61 Biopolis Drive, Proteos, Singapore 138673 (Singapore); KK Research Centre, KK Women' s and Children' s Hospital, 100 Bukit Timah Road, Singapore 229899 (Singapore); Choong, Cleo, E-mail: cleochoong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); KK Research Centre, KK Women' s and Children' s Hospital, 100 Bukit Timah Road, Singapore 229899 (Singapore); Wong, Marcus Thien Chong [Plastic, Reconstructive & Aesthetic Surgery, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433 (Singapore)

    2017-06-01

    Adipose tissue is a rich source of extracellular matrix (ECM) material that can be isolated by delipidating and decellularizing the tissue. However, the current delipidation and decellularization methods either involve tedious and lengthy processes or require toxic chemicals, which may result in the elimination of vital proteins and growth factors found in the ECM. Hence, an alternative delipidation and decellularization method for adipose tissue was developed using supercritical carbon dioxide (SC-CO{sub 2}) that eliminates the need of any harsh chemicals and also reduces the amount of processing time required. The resultant SC-CO{sub 2}-treated ECM material showed an absence of nuclear content but the preservation of key proteins such as collagen Type I, collagen Type III, collagen Type IV, elastin, fibronectin and laminin. In addition, other biological factors such as glycosaminoglycans (GAGs) and growth factors such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were also retained. Subsequently, the resulting SC-CO{sub 2}-treated ECM material was used as a bioactive coating on tissue culture plastic (TCP). Four different cell types including adipose tissue-derived mesenchymal stem cells (ASCs), human umbilical vein endothelial cells (HUVECs), immortalized human keratinocyte (HaCaT) cells and human monocytic leukemia cells (THP-1) were used in this study to show that the SC-CO{sub 2}-treated ECM coating can be potentially used for various biomedical applications. The SC-CO{sub 2}-treated ECM material showed improved cell-material interactions for all cell types tested. In addition, in vitro scratch wound assay using HaCaT cells showed that the presence of SC-CO{sub 2}-treated ECM material enhanced keratinocyte migration whilst the in vitro cellular studies using THP-1-derived macrophages showed that the SC-CO{sub 2}-treated ECM material did not evoke pro-inflammatory responses from the THP-1-derived macrophages. Overall

  20. Supercritical carbon dioxide extracted extracellular matrix material from adipose tissue.

    Science.gov (United States)

    Wang, Jun Kit; Luo, Baiwen; Guneta, Vipra; Li, Liang; Foo, Selin Ee Min; Dai, Yun; Tan, Timothy Thatt Yang; Tan, Nguan Soon; Choong, Cleo; Wong, Marcus Thien Chong

    2017-06-01

    Adipose tissue is a rich source of extracellular matrix (ECM) material that can be isolated by delipidating and decellularizing the tissue. However, the current delipidation and decellularization methods either involve tedious and lengthy processes or require toxic chemicals, which may result in the elimination of vital proteins and growth factors found in the ECM. Hence, an alternative delipidation and decellularization method for adipose tissue was developed using supercritical carbon dioxide (SC-CO 2 ) that eliminates the need of any harsh chemicals and also reduces the amount of processing time required. The resultant SC-CO 2 -treated ECM material showed an absence of nuclear content but the preservation of key proteins such as collagen Type I, collagen Type III, collagen Type IV, elastin, fibronectin and laminin. In addition, other biological factors such as glycosaminoglycans (GAGs) and growth factors such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were also retained. Subsequently, the resulting SC-CO 2 -treated ECM material was used as a bioactive coating on tissue culture plastic (TCP). Four different cell types including adipose tissue-derived mesenchymal stem cells (ASCs), human umbilical vein endothelial cells (HUVECs), immortalized human keratinocyte (HaCaT) cells and human monocytic leukemia cells (THP-1) were used in this study to show that the SC-CO 2 -treated ECM coating can be potentially used for various biomedical applications. The SC-CO 2 -treated ECM material showed improved cell-material interactions for all cell types tested. In addition, in vitro scratch wound assay using HaCaT cells showed that the presence of SC-CO 2 -treated ECM material enhanced keratinocyte migration whilst the in vitro cellular studies using THP-1-derived macrophages showed that the SC-CO 2 -treated ECM material did not evoke pro-inflammatory responses from the THP-1-derived macrophages. Overall, this study shows the efficacy

  1. Supercritical carbon dioxide extracted extracellular matrix material from adipose tissue

    International Nuclear Information System (INIS)

    Wang, Jun Kit; Luo, Baiwen; Guneta, Vipra; Li, Liang; Foo, Selin Ee Min; Dai, Yun; Tan, Timothy Thatt Yang; Tan, Nguan Soon; Choong, Cleo; Wong, Marcus Thien Chong

    2017-01-01

    Adipose tissue is a rich source of extracellular matrix (ECM) material that can be isolated by delipidating and decellularizing the tissue. However, the current delipidation and decellularization methods either involve tedious and lengthy processes or require toxic chemicals, which may result in the elimination of vital proteins and growth factors found in the ECM. Hence, an alternative delipidation and decellularization method for adipose tissue was developed using supercritical carbon dioxide (SC-CO 2 ) that eliminates the need of any harsh chemicals and also reduces the amount of processing time required. The resultant SC-CO 2 -treated ECM material showed an absence of nuclear content but the preservation of key proteins such as collagen Type I, collagen Type III, collagen Type IV, elastin, fibronectin and laminin. In addition, other biological factors such as glycosaminoglycans (GAGs) and growth factors such as basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were also retained. Subsequently, the resulting SC-CO 2 -treated ECM material was used as a bioactive coating on tissue culture plastic (TCP). Four different cell types including adipose tissue-derived mesenchymal stem cells (ASCs), human umbilical vein endothelial cells (HUVECs), immortalized human keratinocyte (HaCaT) cells and human monocytic leukemia cells (THP-1) were used in this study to show that the SC-CO 2 -treated ECM coating can be potentially used for various biomedical applications. The SC-CO 2 -treated ECM material showed improved cell-material interactions for all cell types tested. In addition, in vitro scratch wound assay using HaCaT cells showed that the presence of SC-CO 2 -treated ECM material enhanced keratinocyte migration whilst the in vitro cellular studies using THP-1-derived macrophages showed that the SC-CO 2 -treated ECM material did not evoke pro-inflammatory responses from the THP-1-derived macrophages. Overall, this study shows the efficacy

  2. EFFECTS OF DIFFERENT SUTURE MATERIALS ON TISSUE HEALING

    Directory of Open Access Journals (Sweden)

    Fırat SELVİ

    2016-01-01

    Full Text Available Purpose: The purpose of this study was to investigate the healing differences in between four different widely used suture materials in the oral surgery practice, including silk (Perma- Hand; Ethicon, INC., Somerville, NJ, USA, polypropylene (Prolene; Ethicon, INC., Somerville, NJ, USA, coated polyglactin 910 (Ethicon, INC., Somerville, NJ, USA. and polyglecaprone 25 (Ethicon, INC., Somerville, NJ, USA . Materials and Methods: 20 male rats were randomly allocated into two groups depending on their sacrification days (post-operative 1st and the 7th days. Four longitudinal incision wounds, each 1cm in size, were created on the dorsum of each animal which were then primarily closed with four different types of sutures. Results: The effects of these suture materials on soft tissue healing were compared histopathologically, by means of density of the cells, necrosis, fibrosis, foreign body reaction, the presence of cells of acute and chronic infection. No statistically significant difference was observed between the groups regarding the density of the cells, necrosis, fibrosis, foreign body reaction, and the presence of the cells of acute & chronic infections. Of note, propylene showed slightly less tissue reaction among the other materials. Conclusion: The results of our study showed that there is no only one ideal suture material for surgical practice. The factors related to the patient, the type of the surgery and the quality of the tissue are important to decide an appropriate suture material.

  3. A model of engineering materials inspired by biological tissues

    Directory of Open Access Journals (Sweden)

    Holeček M.

    2009-12-01

    Full Text Available The perfect ability of living tissues to control and adapt their mechanical properties to varying external conditions may be an inspiration for designing engineering materials. An interesting example is the smooth muscle tissue since this "material" is able to change its global mechanical properties considerably by a subtle mechanism within individual muscle cells. Multi-scale continuum models may be useful in designing essentially simpler engineering materials having similar properties. As an illustration we present the model of an incompressible material whose microscopic structure is formed by flexible, soft but incompressible balls connected mutually by linear springs. This simple model, however, shows a nontrivial nonlinear behavior caused by the incompressibility of balls and is very sensitive on some microscopic parameters. It may elucidate the way by which "small" changes in biopolymer networks within individual muscular cells may control the stiffness of the biological tissue, which outlines a way of designing similar engineering materials. The 'balls and springs' material presents also prestress-induced stiffening and allows elucidating a contribution of extracellular fluids into the tissue’s viscous properties.

  4. Bionic Design, Materials and Performance of Bone Tissue Scaffolds

    Directory of Open Access Journals (Sweden)

    Tong Wu

    2017-10-01

    Full Text Available Design, materials, and performance are important factors in the research of bone tissue scaffolds. This work briefly describes the bone scaffolds and their anatomic structure, as well as their biological and mechanical characteristics. Furthermore, we reviewed the characteristics of metal materials, inorganic materials, organic polymer materials, and composite materials. The importance of the bionic design in preoperative diagnosis models and customized bone scaffolds was also discussed, addressing both the bionic structure design (macro and micro structure and the bionic performance design (mechanical performance and biological performance. Materials and performance are the two main problems in the development of customized bone scaffolds. Bionic design is an effective way to solve these problems, which could improve the clinical application of bone scaffolds, by creating a balance between mechanical performance and biological performance.

  5. Fabrication and characterisation of biomimetic, electrospun gelatin fibre scaffolds for tunica media-equivalent, tissue engineered vascular grafts

    Energy Technology Data Exchange (ETDEWEB)

    Elsayed, Y. [Advanced Materials Group, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Lekakou, C., E-mail: C.Lekakou@surrey.ac.uk [Advanced Materials Group, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Labeed, F. [Centre of Biomedical Engineering, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Tomlins, P. [National Physical Laboratory (NPL), Teddington, Middlesex TW11 0LW (United Kingdom)

    2016-04-01

    It is increasingly recognised that biomimetic, natural polymers mimicking the extracellular matrix (ECM) have low thrombogenicity and functional motifs that regulate cell–matrix interactions, with these factors being critical for tissue engineered vascular grafts especially grafts of small diameter. Gelatin constitutes a low cost substitute of soluble collagen but gelatin scaffolds so far have shown generally low strength and suture retention strength. In this study, we have devised the fabrication of novel, electrospun, multilayer, gelatin fibre scaffolds, with controlled fibre layer orientation, and optimised gelatin crosslinking to achieve not only compliance equivalent to that of coronary artery but also for the first time strength of the wet tubular acellular scaffold (swollen with absorbed water) same as that of the tunica media of coronary artery in both circumferential and axial directions. Most importantly, for the first time for natural scaffolds and in particular gelatin, high suture retention strength was achieved in the range of 1.8–1.94 N for wet acellular scaffolds, same or better than that for fresh saphenous vein. The study presents the investigations to relate the electrospinning process parameters to the microstructural parameters of the scaffold, which are further related to the mechanical performance data of wet, crosslinked, electrospun scaffolds in both circumferential and axial tubular directions. The scaffolds exhibited excellent performance in human smooth muscle cell (SMC) proliferation, with SMCs seeded on the top surface adhering, elongating and aligning along the local fibres, migrating through the scaffold thickness and populating a transverse distance of 186 μm and 240 μm 9 days post-seeding for scaffolds of initial dry porosity of 74 and 83%, respectively. - Highlights: • Novel crosslinked electrospun gelatin scaffolds of specific fibre layer orientation • These scaffolds have compliance equivalent to that of coronary

  6. Electrospun nanofibrous materials for tissue engineering and drug delivery

    Directory of Open Access Journals (Sweden)

    Wenguo Cui, Yue Zhou and Jiang Chang

    2010-01-01

    Full Text Available The electrospinning technique, which was invented about 100 years ago, has attracted more attention in recent years due to its possible biomedical applications. Electrospun fibers with high surface area to volume ratio and structures mimicking extracellular matrix (ECM have shown great potential in tissue engineering and drug delivery. In order to develop electrospun fibers for these applications, different biocompatible materials have been used to fabricate fibers with different structures and morphologies, such as single fibers with different composition and structures (blending and core-shell composite fibers and fiber assemblies (fiber bundles, membranes and scaffolds. This review summarizes the electrospinning techniques which control the composition and structures of the nanofibrous materials. It also outlines possible applications of these fibrous materials in skin, blood vessels, nervous system and bone tissue engineering, as well as in drug delivery.

  7. Hydrocortisone and triiodothyronine regulate hyaluronate synthesis in a tissue-engineered human dermal equivalent through independent pathways.

    Science.gov (United States)

    Deshpande, Madhura; Papp, Suzanne; Schaffer, Lana; Pouyani, Tara

    2015-02-01

    Hydrocortisone (HC) and triiodothyronine (T3) have both been shown to be capable of independently inhibiting hyaluronate (HA, hyaluronic acid) synthesis in a self-assembled human dermal equivalent (human dermal matrix). We sought to investigate the action of these two hormones in concert on extracellular matrix formation and HA inhibition in the tissue engineered human dermal matrix. To this end, neonatal human dermal fibroblasts were cultured in defined serum-free medium for 21 days in the presence of each hormone alone, or in combination, in varying concentrations. Through a process of self-assembly, a substantial dermal extracellular matrix formed that was characterized. The results of these studies demonstrate that combinations of the hormones T3 and hydrocortisone showed significantly higher levels of hyaluronate inhibition as compared to each hormone alone in the human dermal matrix. In order to gain preliminary insight into the genes regulating HA synthesis in this system, a differential gene array analysis was conducted in which the construct prepared in the presence of 200 μg/mL HC and 0.2 nM T3 was compared to the normal construct (0.4 μg/mL HC and 20 pM T3). Using a GLYCOv4 gene chip containing approximately 1260 human genes, we observed differential expression of 131 genes. These data suggest that when these two hormones are used in concert a different mechanism of inhibition prevails and a combination of degradation and inhibition of HA synthesis may be responsible for HA regulation in the human dermal matrix. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  8. Comparison of average glandular dose in screen-film and digital mammography using breast tissue-equivalent phantom

    International Nuclear Information System (INIS)

    Shin, Gwi Soon; Kim, Jung Min; Kim, You Hyun; Choi, Jong Hak; Kim, Chang Kyun

    2007-01-01

    In recent years, mammography system is changed rapidly from conventional screen-film system to digital system for application to screening and diagnosis. Digital mammography system provides several advantages over screen-film mammography system. According to the information provided by the manufacturer, digital mammography system offers radiation dose reduction in comparison with screen-film mammography system, because of digital detector, particularly direct digital detector has higher x-ray absorption efficiency than screen-film combination or imaging plate (IP). We measured average glandular doses (ADG) in screen-film mammography (SFM) system with slow screen-film combination, computed mammography (CM) system, indirect digital mammography (IDM) system and direct digital mammography (DDM) system using breast tissue-equivalent phantom (glandularity 30%, 50% and 70%). The results were shown as follows: AGD values for DDM system were highest than those for other systems. Although automatic exposure control (AEC) mode was selected, the curve of the AGD values against thickness or glandularity increased significantly for the SFM system with the uniform target/filter (Mo/Mo) combination. Therefore, the AGD values for the high energy examinations were highest in the SFM system, and those for the low energy examinations were highest in the DDM system. But the curve of the AGD values against thickness and glandularity increased gently for CM system with the automatic selection of the target/filter combination (from Mo/Mo to Mo/Rh or from Mo/Rh to Rh/Rh), and the AGD values were lowest. Consequently, the parameters in mammography for each exposure besides detection efficiency play an important role in order to estimate a patient radiation dose

  9. Preclinical study of mouse pluripotent parthenogenetic embryonic stem cell derivatives for the construction of tissue-engineered skin equivalent.

    Science.gov (United States)

    Rao, Yang; Cui, Jihong; Yin, Lu; Liu, Wei; Liu, Wenguang; Sun, Mei; Yan, Xingrong; Wang, Ling; Chen, Fulin

    2016-10-22

    Embryonic stem cell (ESC) derivatives hold great promise for the construction of tissue-engineered skin equivalents (TESE). However, harvesting of ESCs destroys viable embryos and may lead to political and ethical concerns over their application. In the current study, we directed mouse parthenogenetic embryonic stem cells (pESCs) to differentiate into fibroblasts, constructed TESE, and evaluated its function in vivo. The stemness marker expression and the pluripotent differentiation ability of pESCs were tested. After embryoid body (EB) formation and adherence culture, mesenchymal stem cells (MSCs) were enriched and directed to differentiate into fibroblastic lineage. Characteristics of derived fibroblasts were assessed by quantitative real-time PCR and ELISA. Functional ability of the constructed TESE was tested by a mouse skin defects repair model. Mouse pESCs expressed stemness marker and could form teratoma containing three germ layers. MSCs could be enriched from outgrowths of EBs and directed to differentiate into fibroblastic lineage. These cells express a high level of growth factors including FGF, EGF, VEGF, TGF, PDGF, and IGF1, similar to those of ESC-derived fibroblasts and mouse fibroblasts. Seeded into collagen gels, the fibroblasts derived from pESCs could form TESE. Mouse skin defects could be successfully repaired 15 days after transplantation of TESE constructed by fibroblasts derived from pESCs. pESCs could be induced to differentiate into fibroblastic lineage, which could be applied to the construction of TESE and skin defect repair. Particularly, pESC derivatives avoid the limitations of political and ethical concerns, and provide a promising source for regenerative medicine.

  10. Elastic properties of synthetic materials for soft tissue modeling

    International Nuclear Information System (INIS)

    Mansy, H A; Grahe, J R; Sandler, R H

    2008-01-01

    Mechanical models of soft tissue are useful for studying vibro-acoustic phenomena. They may be used for validating mathematical models and for testing new equipment and techniques. The objective of this study was to measure density and visco-elastic properties of synthetic materials that can be used to build such models. Samples of nine different materials were tested under dynamic (0.5 Hz) compressive loading conditions. The modulus of elasticity of the materials was varied, whenever possible, by adding a softener during manufacturing. The modulus was measured over a nine month period to quantify the effect of ageing and softener loss on material properties. Results showed that a wide range of the compression elasticity modulus (10 to 1400 kPa) and phase (3.5 0 -16.7 0 ) between stress and strain were possible. Some materials tended to exude softener over time, resulting in a weight loss and elastic properties change. While the weight loss under normal conditions was minimal in all materials (<3% over nine months), loss under accelerated weight-loss conditions can reach 59%. In the latter case an elasticity modulus increase of up to 500% was measured. Key advantages and limitations of candidate materials were identified and discussed

  11. On the Rule of Mixtures for Predicting Stress-Softening and Residual Strain Effects in Biological Tissues and Biocompatible Materials

    Directory of Open Access Journals (Sweden)

    Alex Elías-Zúñiga

    2014-01-01

    Full Text Available In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects. For the isotropic energy part, we select the amended non-Gaussian strain energy density model, while the energy fiber effects are added by considering the equivalent anisotropic volumetric fraction contribution, as well as the isotropized representation form of the eight-chain energy model that accounts for the material anisotropic effects. Furthermore, our proposed material model uses a phenomenological non-monotonous softening function that predicts stress softening effects and has an energy term, derived from the pseudo-elasticity theory, that accounts for residual strain deformations. The model’s theoretical predictions are compared with experimental data collected from human vaginal tissues, mice skin, poly(glycolide-co-caprolactone (PGC25 3-0 and polypropylene suture materials and tracheal and brain human tissues. In all cases examined here, our equivalent material model closely follows stress-softening and residual strain effects exhibited by experimental data.

  12. On the Rule of Mixtures for Predicting Stress-Softening and Residual Strain Effects in Biological Tissues and Biocompatible Materials

    Science.gov (United States)

    Elías-Zúñiga, Alex; Baylón, Karen; Ferrer, Inés; Serenó, Lídia; Garcia-Romeu, Maria Luisa; Bagudanch, Isabel; Grabalosa, Jordi; Pérez-Recio, Tania; Martínez-Romero, Oscar; Ortega-Lara, Wendy; Elizalde, Luis Ernesto

    2014-01-01

    In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects. For the isotropic energy part, we select the amended non-Gaussian strain energy density model, while the energy fiber effects are added by considering the equivalent anisotropic volumetric fraction contribution, as well as the isotropized representation form of the eight-chain energy model that accounts for the material anisotropic effects. Furthermore, our proposed material model uses a phenomenological non-monotonous softening function that predicts stress softening effects and has an energy term, derived from the pseudo-elasticity theory, that accounts for residual strain deformations. The model’s theoretical predictions are compared with experimental data collected from human vaginal tissues, mice skin, poly(glycolide-co-caprolactone) (PGC25 3-0) and polypropylene suture materials and tracheal and brain human tissues. In all cases examined here, our equivalent material model closely follows stress-softening and residual strain effects exhibited by experimental data. PMID:28788466

  13. Degradation of proton depth dose distributions attributable to microstructures in lung-equivalent material

    Energy Technology Data Exchange (ETDEWEB)

    Titt, Uwe, E-mail: utitt@mdanderson.org; Mirkovic, Dragan; Mohan, Radhe [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Sell, Martin [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and Department of Medical Physics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 (United States); Bangert, Mark [Department of Medical Physics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Oelfke, Uwe [Department of Medical Physics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120, Germany and Department of Physics, The Institute of Cancer Research, 123 Old Brompton Road, London SW7 3RP (United Kingdom)

    2015-11-15

    Purpose: The purpose of the work reported here was to investigate the influence of sub-millimeter size heterogeneities on the degradation of the distal edges of proton beams and to validate Monte Carlo (MC) methods’ ability to correctly predict such degradation. Methods: A custom-designed high-resolution plastic phantom approximating highly heterogeneous, lung-like structures was employed in measurements and in Monte Carlo simulations to evaluate the degradation of proton Bragg curves penetrating heterogeneous media. Results: Significant differences in distal falloff widths and in peak dose values were observed in the measured and the Monte Carlo simulated curves compared to pristine proton Bragg curves. Furthermore, differences between simulations of beams penetrating CT images of the phantom did not agree well with the corresponding experimental differences. The distal falloff widths in CT image-based geometries were underestimated by up to 0.2 cm in water (corresponding to 0.8–1.4 cm in lung tissue), and the peak dose values of pristine proton beams were overestimated by as much as ~35% compared to measured curves or depth-dose curves simulated on the basis of true geometry. The authors demonstrate that these discrepancies were caused by the limited spatial resolution of CT images that served as a basis for dose calculations and lead to underestimation of the impact of the fine structure of tissue heterogeneities. A convolution model was successfully applied to mitigate the underestimation. Conclusions: The results of this study justify further development of models to better represent heterogeneity effects in soft-tissue geometries, such as lung, and to correct systematic underestimation of the degradation of the distal edge of proton doses.

  14. Degradation of proton depth dose distributions attributable to microstructures in lung-equivalent material

    International Nuclear Information System (INIS)

    Titt, Uwe; Mirkovic, Dragan; Mohan, Radhe; Sell, Martin; Unkelbach, Jan; Bangert, Mark; Oelfke, Uwe

    2015-01-01

    Purpose: The purpose of the work reported here was to investigate the influence of sub-millimeter size heterogeneities on the degradation of the distal edges of proton beams and to validate Monte Carlo (MC) methods’ ability to correctly predict such degradation. Methods: A custom-designed high-resolution plastic phantom approximating highly heterogeneous, lung-like structures was employed in measurements and in Monte Carlo simulations to evaluate the degradation of proton Bragg curves penetrating heterogeneous media. Results: Significant differences in distal falloff widths and in peak dose values were observed in the measured and the Monte Carlo simulated curves compared to pristine proton Bragg curves. Furthermore, differences between simulations of beams penetrating CT images of the phantom did not agree well with the corresponding experimental differences. The distal falloff widths in CT image-based geometries were underestimated by up to 0.2 cm in water (corresponding to 0.8–1.4 cm in lung tissue), and the peak dose values of pristine proton beams were overestimated by as much as ~35% compared to measured curves or depth-dose curves simulated on the basis of true geometry. The authors demonstrate that these discrepancies were caused by the limited spatial resolution of CT images that served as a basis for dose calculations and lead to underestimation of the impact of the fine structure of tissue heterogeneities. A convolution model was successfully applied to mitigate the underestimation. Conclusions: The results of this study justify further development of models to better represent heterogeneity effects in soft-tissue geometries, such as lung, and to correct systematic underestimation of the degradation of the distal edge of proton doses

  15. Multiscale mechanics of hierarchical structure/property relationships in calcified tissues and tissue/material interfaces

    International Nuclear Information System (INIS)

    Katz, J. Lawrence; Misra, Anil; Spencer, Paulette; Wang, Yong; Bumrerraj, Sauwanan; Nomura, Tsutomu; Eppell, Steven J.; Tabib-Azar, Massood

    2007-01-01

    This paper presents a review plus new data that describes the role hierarchical nanostructural properties play in developing an understanding of the effect of scale on the material properties (chemical, elastic and electrical) of calcified tissues as well as the interfaces that form between such tissues and biomaterials. Both nanostructural and microstructural properties will be considered starting with the size and shape of the apatitic mineralites in both young and mature bovine bone. Microstructural properties for human dentin and cortical and trabecular bone will be considered. These separate sets of data will be combined mathematically to advance the effects of scale on the modeling of these tissues and the tissue/biomaterial interfaces as hierarchical material/structural composites. Interfacial structure and properties to be considered in greatest detail will be that of the dentin/adhesive (d/a) interface, which presents a clear example of examining all three material properties, (chemical, elastic and electrical). In this case, finite element modeling (FEA) was based on the actual measured values of the structure and elastic properties of the materials comprising the d/a interface; this combination provides insight into factors and mechanisms that contribute to premature failure of dental composite fillings. At present, there are more elastic property data obtained by microstructural measurements, especially high frequency ultrasonic wave propagation (UWP) and scanning acoustic microscopy (SAM) techniques. However, atomic force microscopy (AFM) and nanoindentation (NI) of cortical and trabecular bone and the dentin-enamel junction (DEJ) among others have become available allowing correlation of the nanostructural level measurements with those made on the microstructural level

  16. Adhesive protein interactions with chitosan: consequences for valve endothelial cell growth on tissue-engineering materials.

    Science.gov (United States)

    Cuy, Janet L; Beckstead, Benjamin L; Brown, Chad D; Hoffman, Allan S; Giachelli, Cecilia M

    2003-11-01

    Stable endothelialization of a tissue-engineered heart valve is essential for proper valve function, although adhesive characteristics of the native valve endothelial cell (VEC) have rarely been explored. This research evaluated VEC adhesive qualities and attempted to enhance VEC growth on the biopolymer chitosan, a novel tissue-engineering scaffold material with promising biological and chemical properties. Aortic VEC cultures were isolated and found to preferentially adhere to fibronectin, collagen types IV and I over laminin and osteopontin in a dose-dependent manner. Seeding of VEC onto comparison substrates revealed VEC growth and morphology to be preferential in the order: tissue culture polystyrene > gelatin, poly(DL-lactide-co-glycolide), chitosan > poly(hydroxy alkanoate). Adhesive protein precoating of chitosan did not significantly enhance VEC growth, despite equivalent protein adsorption as to polystyrene. Initial cell adhesion to protein-precoated chitosan, however, was higher than for polystyrene. Composite chitosan/collagen type IV films were investigated as an alternative to simple protein precoatings, and were shown to improve VEC growth and morphology over chitosan alone. These findings suggest potential manipulation of chitosan properties to improve amenability to valve tissue-engineering applications. Copyright 2003 Wiley Periodicals, Inc.

  17. Evaluation of some water - equivalent plastics as phantom materials for electron dosimetry

    International Nuclear Information System (INIS)

    Mihailescu, D.; Borcia, C.

    2005-01-01

    In the International Code of Practice for Dosimetry TRS-398 published by the International Atomic Energy Agency (IAEA), water is recommended as the reference medium for the determination of absorbed dose for high-energy electron beams. Plastic phantoms may be used under certain circumstances (electron energy below 10 MeV, R 50 2 ) for electron beam dosimetry. In this case, a depth-scaling factor is required for the conversion of depth in solid phantoms to depth in water. A fluence-scaling factor is also necessary for converting ionization chamber readings in plastic phantom to readings in water. The aim of this paper is to calculate, using Monte Carlo simulations, the depth-scaling factors c pl and fluence-scaling factors h pl of some commercially available water substitute solid phantoms in order to evaluate their water equivalency. Two sets of calculations were performed: one for electron pencil beams and another for 10 x 10 cm 2 parallel beams, both of which are normally incident on water and solid phantoms. We used only mono-energetic beams of 6, 9, 12, 15, and 18 MeV. The results were compared with TRS-398 recommended values. In the case of pencil beams, we found that by applying the TRS-398 protocol, unacceptable uncertainties (up to 10%) were introduced in the dose distribution calculations. By contrast, TRS-398 can safely be used for 10 x 10 cm 2 beams (reference beams). In this case, uncertainties lower than 1% were obtained, what was in agreement with other published data. (authors)

  18. Controlling human corneal stromal stem cell contraction to mediate rapid cell and matrix organization of real architecture for 3-dimensional tissue equivalents.

    Science.gov (United States)

    Mukhey, Dev; Phillips, James B; Daniels, Julie T; Kureshi, Alvena K

    2018-02-01

    The architecture of the human corneal stroma consists of a highly organized extracellular matrix (ECM) interspersed with keratocytes. Their progenitor cells; corneal stromal stem cells (CSSC) are located at the periphery, in the limbal stroma. A highly organized corneal ECM is critical for effective transmission of light but this structure may be compromised during injury or disease, resulting in loss of vision. Re-creating normal organization in engineered tissue equivalents for transplantation often involves lengthy culture times that are inappropriate for clinical use or utilisation of synthetic substrates that bring complications such as corneal melting. CSSC have great therapeutic potential owing to their ability to reorganize a disorganized matrix, restoring transparency in scarred corneas. We examined CSSC contractile behavior to assess whether this property could be exploited to rapidly generate cell and ECM organization in Real Architecture For 3D Tissues (RAFT) tissue equivalents (TE) for transplantation. Free-floating collagen gels were characterized to assess contractile behavior of CSSC and establish optimum cell density and culture times. To mediate cell and collagen organization, tethered collagen gels seeded with CSSC were cultured and subsequently stabilized with the RAFT process. We demonstrated rapid creation of biomimetic RAFT TE with tunable structural properties. These displayed three distinct regions of varying degrees of cellular and collagen organization. Interestingly, increased organization coincided with a dramatic loss of PAX6 expression in CSSC, indicating rapid differentiation into keratocytes. The organized RAFT TE system could be a useful bioengineering tool to rapidly create an organized ECM while simultaneously controlling cell phenotype. For the first time, we have demonstrated that human CSSC exhibit the phenomenon of cellular self-alignment in tethered collagen gels. We found this mediated rapid co-alignment of collagen fibrils

  19. Dosimetry of radium equivalent in construction material of brick works in Sao Jose do Sabugi City - Paraiba, Brazil

    International Nuclear Information System (INIS)

    Araujo, Eduardo Eudes Nobrega de; Santos Junior, Jose Araujo dos; Amaral, Romilton dos Santos; Santos, Josineide Marques do Nascimento; Spacov, Isabel Cristina Guerra; Fernandez, Zahily Herrero

    2015-01-01

    The earth's crust has in its composition the Naturally Occurring Radioactive Material (NORM) that may have increased concentration due to activities of exploration and extraction of environmental resources. The civil construction is an economic activity that requires the use of much of the natural resources, such as the raw material of brick works, like clays, mainly used for the production of bricks and tiles. These construction materials may contain high levels of natural radioactive elements, even with concentrations higher than the limits established, given that the levels vary according to the composition of rocks and soil, due to the geological formation and may result in increased exposure of humans to natural radioactive activities. In this context, the radioecological dosimetry is defined in terms of Radium Equivalent activity (Ra eq ), that ensure radiometric conditions for the use of material derived from clays before its final application in housing construction, an initiative that ensures the radioecological safety of population. Thus, this study aimed to establish the calculation of Ra eq in the raw material of brick works located in Sao Jose do Sabugi city, state of Paraiba, in an area adjacent to the uranium deposits of Espinharas, to estimate the risks associated with primordial radionuclides attributed to TENORM activities (Technologically Enhanced Naturally Occurring Radioactive Materials) from the extraction and use of clay as a raw material in the manufacture of bricks and tiles. Analyses were performed by High Resolution Gamma Spectrometry, with HPGe-Be detector, assuming the state of secular radioactive equilibrium. The results ranged from 183.2 to 747.78 Bq/kg, with an average of 494.6 Bq/kg which exceeded the limit of 370 Bq/kg established by UNSCEAR for construction materials. Some samples obtained values exceeded by up the double this limit, suggesting control and radiometric certification for application of this material. (author)

  20. Dosimetry of radium equivalent in construction material of brick works in Sao Jose do Sabugi City - Paraiba, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Eduardo Eudes Nobrega de; Santos Junior, Jose Araujo dos; Amaral, Romilton dos Santos; Santos, Josineide Marques do Nascimento; Spacov, Isabel Cristina Guerra; Fernandez, Zahily Herrero, E-mail: eduardo.eudes@ufpe.br, E-mail: jaraujo@ufpe.br, E-mail: romilton@ufpe.br, E-mail: neideden@hotmail.com, E-mail: isabelspacov@gmail.com, E-mail: zahily1985@gmail.com [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear. Grupo de Radioecologia

    2015-07-01

    The earth's crust has in its composition the Naturally Occurring Radioactive Material (NORM) that may have increased concentration due to activities of exploration and extraction of environmental resources. The civil construction is an economic activity that requires the use of much of the natural resources, such as the raw material of brick works, like clays, mainly used for the production of bricks and tiles. These construction materials may contain high levels of natural radioactive elements, even with concentrations higher than the limits established, given that the levels vary according to the composition of rocks and soil, due to the geological formation and may result in increased exposure of humans to natural radioactive activities. In this context, the radioecological dosimetry is defined in terms of Radium Equivalent activity (Ra{sub eq}), that ensure radiometric conditions for the use of material derived from clays before its final application in housing construction, an initiative that ensures the radioecological safety of population. Thus, this study aimed to establish the calculation of Ra{sub eq} in the raw material of brick works located in Sao Jose do Sabugi city, state of Paraiba, in an area adjacent to the uranium deposits of Espinharas, to estimate the risks associated with primordial radionuclides attributed to TENORM activities (Technologically Enhanced Naturally Occurring Radioactive Materials) from the extraction and use of clay as a raw material in the manufacture of bricks and tiles. Analyses were performed by High Resolution Gamma Spectrometry, with HPGe-Be detector, assuming the state of secular radioactive equilibrium. The results ranged from 183.2 to 747.78 Bq/kg, with an average of 494.6 Bq/kg which exceeded the limit of 370 Bq/kg established by UNSCEAR for construction materials. Some samples obtained values exceeded by up the double this limit, suggesting control and radiometric certification for application of this material

  1. 2, 3-Dihydrazone cellulose: Prospective material for tissue engineering scaffolds

    International Nuclear Information System (INIS)

    Verma, Vipin; Verma, Poonam; Ray, Pratima; Ray, Alok R.

    2008-01-01

    Cellulose was oxidized by sodium metaperiodate to give rise to 2, 3-dialdehyde cellulose with 92% oxidation ratio, which was further reacted with hydrazine to form 2, 3-dihydrazone cellulose for the incorporation of NH 2 groups. Two forms of matrix, i.e. films and sponges were fabricated. The materials were characterized by FTIR spectroscopy. Scanning electron microscopy revealed its porous architecture with an average pore size of 150 μm. Swelling studies were carried out in phosphate buffer saline (PBS) at physiological pH 7.4. The contact angle of the 2, 3-dihydrazone cellulose surface was determined for assessing its hydrophilicity which came out to be 23 deg. ± 2 deg. NIH3T3 mice fibroblast cells were used for determining the cytocompatibility of the surfaces. The morphology of the cells was observed through optical inverted microscopy. The results show that 2, 3-dihydrazone cellulose can be used as scaffold material in tissue engineering

  2. Microcystin-LR equivalent concentrations in fish tissue during a postbloom Microcystis exposure in Loskop Dam, South Africa

    CSIR Research Space (South Africa)

    Nchabeleng, T

    2014-12-01

    Full Text Available The effects of a decomposing cyanobacteria bloom on water quality and the accumulation of microcystin-LR equivalent toxin in fish at Loskop Dam were studied in May 2012. Enzyme-linked immunosorbent assay [ELISA] was used to confirm the presence...

  3. Radium equivalent activity of building materials and gamma ray dose rates in ordinary houses of Sao Paulo, Brazil

    International Nuclear Information System (INIS)

    Campos, M.P.; Pecequilo, B.R.S.

    1994-01-01

    The external radiation exposure from natural radioactivity represents, approximately, 50% of the average annual dose caused to the human body by all natural and artificial radiation sources. Natural radioactivity in building materials is the most important source of external radiation exposure in dwellings because of the gamma rays emitted from potassium 40 and member of the uranium 238 and thorium 232 decay chains. Concrete is one of the most potential sources of elevated radiation exposure, however, little is known about the natural radioactivity of Brazilian construction materials. A study to predict the exposure rates of several ordinary houses built almost of concrete, consisting of 38 samples of 6 different materials was conducted by using high resolution gamma-ray spectrometry. The radium equivalent activity was calculated for all 38 samples in order to compare the specific activities of the construction materials containing different amounts of radium, thorium, and potassium. The effective dose rate due to the indoor gamma radiation from the building materials was performed following the 1988 UNSCEAR procedures

  4. Preliminary study of silica aerogel as a gas-equivalent material in ionization chambers

    Science.gov (United States)

    Caresana, M.; Zorloni, G.

    2017-12-01

    Since about two decades, a renewed interest on aerogels has risen. These peculiar materials show fairly unique properties. Thus, they are under investigation for both scientific and commercial purposes and new optimized production processes are studied. In this work, the possibility of using aerogel in the field of radiation detection is explored. The idea is to substitute the gas filling in a ionization chamber with the aerogel. The material possesses a density about 100 times greater than ambient pressure air. Where as the open-pore structure should allow the charge carriers to move freely. Small hydrophobic silica aerogel samples were studied. A custom ionization chamber, capable of working both with aerogel or in the classic gas set up, was built. The response of the chamber in current mode was investigated using an X-ray tube. The results obtained showed, under proper conditions, an enhancement of about 60 times of the current signal in the aerogel configuration with respect to the classic gas one. Moreover, some unusual behaviours were observed, i.e. time inertia of the signal and super-/sub-linear current response with respect to the dose rate. While testing high electric fields, aerogel configuration seemed to enhance the Townsend's effects. In order to represent the observed trends, a trapping-detrapping model is proposed, which is capable to predict semi-empirically the steady state currents measured. The time evolution of the signal is semi-quantitatively represented by the same model. The coefficients estimated by the fits are in agreement with similar trapping problems in the literature. In particular, a direct comparison between the benchmark of the FET silica gates and aerogel case endorses the idea that the same type of phenomenon occurs in the studied case.

  5. An Earth-Based Equivalent Low Stretch Apparatus to Assess Material Flammability for Microgravity and Extraterrestrial Fire-Safety Applications

    Science.gov (United States)

    Olson, S. L.; Beeson, H.; Haas, J. P.

    2003-01-01

    The objective of this project is to modify the standard oxygen consumption (cone) calorimeter (described in ASTM E 1354 and NASA STD 6001 Test 2) to provide a reproducible bench-scale test environment that simulates the buoyant or ventilation flow that would be generated by or around a burning surface in a spacecraft or extraterrestrial gravity level. This apparatus will allow us to conduct normal gravity experiments that accurately and quantitatively evaluate a material's flammability characteristics in the real-use environment of spacecraft or extra-terrestrial gravitational acceleration. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone geometry with the sample burning in a ceiling fire configuration that provides a reproducible bench-scale test environment that simulates the buoyant or ventilation flow that would be generated by a flame in a spacecraft or extraterrestrial gravity level. Prototype unit testing results are presented in this paper. Ignition delay times and regression rates for PMMA are presented over a range of radiant heat flux levels and equivalent stretch rates which demonstrate the ability of ELSA to simulate key features of microgravity and extraterrestrial fire behavior.

  6. Tissue reaction and material characteristics of four bone substitutes

    DEFF Research Database (Denmark)

    Jensen, S S; Aaboe, M; Pinholt, E M

    1996-01-01

    and Interpore 500 HA/CC) were implanted into 5-mm bur holes in rabbit tibiae. There was no difference in the amount of newly formed bone around the four biomaterials. Interpore 500 HA/CC resorbed completely, whereas the other three biomaterials did not undergo any detectable biodegradation. Bio......The aim of the present study was to qualitatively and quantitatively compare the tissue reactions around four different bone substitutes used in orthopedic and craniofacial surgery. Cylinders of two bovine bone substitutes (Endobon and Bio-Oss) and two coral-derived bone substitutes (Pro Osteon 500......-Oss was osseointegrated to a higher degree than the other biomaterials. Material characteristics obtained by diffuse reflectance infrared Fourier transform spectrometry analysis and energy-dispersive spectrometry did not explain the differences in biologic behavior....

  7. Probability of cavitation for single ultrasound pulses applied to tissues and tissue-mimicking materials.

    Science.gov (United States)

    Maxwell, Adam D; Cain, Charles A; Hall, Timothy L; Fowlkes, J Brian; Xu, Zhen

    2013-03-01

    In this study, the negative pressure values at which inertial cavitation consistently occurs in response to a single, two-cycle, focused ultrasound pulse were measured in several media relevant to cavitation-based ultrasound therapy. The pulse was focused into a chamber containing one of the media, which included liquids, tissue-mimicking materials, and ex vivo canine tissue. Focal waveforms were measured by two separate techniques using a fiber-optic hydrophone. Inertial cavitation was identified by high-speed photography in optically transparent media and an acoustic passive cavitation detector. The probability of cavitation (P(cav)) for a single pulse as a function of peak negative pressure (p(-)) followed a sigmoid curve, with the probability approaching one when the pressure amplitude was sufficient. The statistical threshold (defined as P(cav) = 0.5) was between p(-) = 26 and 30 MPa in all samples with high water content but varied between p(-) = 13.7 and >36 MPa in other media. A model for radial cavitation bubble dynamics was employed to evaluate the behavior of cavitation nuclei at these pressure levels. A single bubble nucleus with an inertial cavitation threshold of p(-) = 28.2 megapascals was estimated to have a 2.5 nm radius in distilled water. These data may be valuable for cavitation-based ultrasound therapy to predict the likelihood of cavitation at various pressure levels and dimensions of cavitation-induced lesions in tissue. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Feasibility of salvage interstitial microwave thermal therapy for prostate carcinoma following failed brachytherapy: studies in a tissue equivalent phantom

    International Nuclear Information System (INIS)

    McCann, Claire; Kumaradas, J Carl; Gertner, Mark R; Davidson, Sean R H; Dolan, Alfred M; Sherar, Michael D

    2003-01-01

    Thermal therapy is an experimental treatment to destroy solid tumours by heating them to temperatures ranging from 55 deg C to 90 deg C, inducing thermal coagulation and necrosis of the tumour. We are investigating the feasibility of interstitial microwave thermal therapy as a salvage treatment for prostate cancer patients with local recurrence following failed brachytherapy. Due to the electrical and thermal conductivity of the brachytherapy seeds, we hypothesized that the seeds could scatter the microwave energy and cause unpredictable heating. To investigate this, a 915 MHz helical antenna was inserted into a muscle-equivalent phantom with and without brachytherapy seeds. Following a 10 W, 5 s input to the antenna, the temperature rise was used to calculate absorbed power, also referred to as specific absorption rate (SAR). Plane wave models based on Maxwell's equations were also used to characterize the electromagnetic scattering effect of the seeds. In addition, the phantom was heated with 8 W for 5 min to quantify the effect of the seeds on the temperature distribution during extended heating. SAR measurements indicated that the seeds had no significant effect on the shape and size of the SAR pattern of the antenna. However, the plane wave simulations indicated that the seeds could scatter the microwave energy resulting in hot spots at the seed edges. Lack of experimental evidence of these hot spots was probably due to the complex polarization of the microwaves emitted by the helical antenna. Extended heating experiments also demonstrated that the seeds had no significant effect on the temperature distributions and rates of temperature rise measured in the phantom. The results indicate that brachytherapy seeds are not a technical impediment to interstitial microwave thermal therapy as a salvage treatment following failed brachytherapy

  9. The influence of freezing and tissue porosity on the material properties of vegetable tissues

    Energy Technology Data Exchange (ETDEWEB)

    Ralfs, Julie D

    2002-07-01

    Tissue porosity and fluid flow have been shown to be important parameters affecting the mechanical and sensorial behaviour of edible plant tissues. The quantity of fluid and the manner with which it was released on compression of the plant tissue were also important regarding the sensory perception and a good indication of any structural damage resulting from freezing, for example. Potato, carrot and Chinese water chestnut were used to study the effects freezing has on model plant tissues. Mechanical and structural measurements of the plant tissue were correlated with sensory analysis. Conventional freezing was shown to cause severe structural damage predominantly in the form of cavities between or through cells, resulting in decreases in mechanical strength and stiffness, and samples that were perceived in the mouth as 'soft' and 'wet'. The location and size of the cavities formed from ice crystals, depended on the particular plant tissue being frozen, the processing it was subjected to prior to freezing, the size of the sample and the cooling regime employed to freeze the tissue. Cavitation in the tissue resulted in an increase in tissue porosity, which enabled fluid to flow more easily from the tissue on compression, thus affecting the mechanical properties and sensory perception. Freezing damage to plant tissues was shown to be reduced, and sometimes prevented, when active antifreeze proteins (AFPs) were introduced into the tissues by vacuum infiltration or transformation and the tissue was frozen at a suitable cooling rate. Theoretical modelling was applied to the fluid flow and porosity data to test the validity of the models and to subsequently predict the mechanical behaviour of potato from the structural properties of the tissue. (author)

  10. The influence of freezing and tissue porosity on the material properties of vegetable tissues

    International Nuclear Information System (INIS)

    Ralfs, Julie D.

    2002-01-01

    Tissue porosity and fluid flow have been shown to be important parameters affecting the mechanical and sensorial behaviour of edible plant tissues. The quantity of fluid and the manner with which it was released on compression of the plant tissue were also important regarding the sensory perception and a good indication of any structural damage resulting from freezing, for example. Potato, carrot and Chinese water chestnut were used to study the effects freezing has on model plant tissues. Mechanical and structural measurements of the plant tissue were correlated with sensory analysis. Conventional freezing was shown to cause severe structural damage predominantly in the form of cavities between or through cells, resulting in decreases in mechanical strength and stiffness, and samples that were perceived in the mouth as 'soft' and 'wet'. The location and size of the cavities formed from ice crystals, depended on the particular plant tissue being frozen, the processing it was subjected to prior to freezing, the size of the sample and the cooling regime employed to freeze the tissue. Cavitation in the tissue resulted in an increase in tissue porosity, which enabled fluid to flow more easily from the tissue on compression, thus affecting the mechanical properties and sensory perception. Freezing damage to plant tissues was shown to be reduced, and sometimes prevented, when active antifreeze proteins (AFPs) were introduced into the tissues by vacuum infiltration or transformation and the tissue was frozen at a suitable cooling rate. Theoretical modelling was applied to the fluid flow and porosity data to test the validity of the models and to subsequently predict the mechanical behaviour of potato from the structural properties of the tissue. (author)

  11. The response of a spherical tissue-equivalent proportional counter to 56-Fe particles from 200-1000 MeV/nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Gersey, Bradford B.; Borak, Thomas B.; Guetersloh, Stephen B.; Zeitlin, Cary J.; Miller, J.; Heilbronn, L.; Murakami, T.; Iwata, Y.

    2001-09-04

    The radiation environment aboard the space shuttle and the International Space Station includes high-Z and high-energy (HZE) particles that are part of the galactic cosmic radiation (GCR) spectrum. Iron-56 is considered to be one of the most biologically important parts of the GCR spectrum. Tissue-equivalent proportional counters (TEPC) are used as active dosimeters on manned space flights. These TEPC's are further used to determine average quality factor for each space mission. A TEPC simulating a 1 micron diameter sphere of tissue was exposed as part of a particle spectrometer to iron-56 at energies from 200-1000 MeV/nucleon. The response of TEPC in terms of frequency-averaged lineal energy, dose-averaged lineal energy, as well as energy deposited at different impact parameters through detector was determined for six different incident energies of iron-56 in this energy range. Calculations determined that charged particle equilibrium was achieved for each of the six experiments. Energy depositions at different impact parameters were calculated using a radial dose distribution model and the results compared to experimental data.

  12. Tutorial: Electroporation of cells in complex materials and tissue

    Science.gov (United States)

    Rems, L.; Miklavčič, D.

    2016-05-01

    Electroporation is being successfully used in biology, medicine, food processing, and biotechnology, and in some environmental applications. Recent applications also include in addition to classical electroporation, where cells are exposed to micro- or milliseconds long pulses, exposures to extremely short nanosecond pulses, i.e., high-frequency electroporation. Electric pulses are applied to cells in different structural configurations ranging from suspended cells to cells in tissues. Understanding electroporation of cells in tissues and other complex environments is a key to its successful use and optimization in various applications. Thus, explanation will be provided theoretically/numerically with relation to experimental observations by scaling our understanding of electroporation from the molecular level of the cell membrane up to the tissue level.

  13. Effects of Apollo 12 lunar material on lipid levels of tobacco tissue and slash pine cultures

    Science.gov (United States)

    Weete, J. D.

    1972-01-01

    Investigations of the lipid components of pine tissues (Pinus elloitii) are discussed, emphasizing fatty acids and steroids. The response by slash pine tissue cultures to growth in contact with Apollo lunar soil, earth basalt, and Iowa soil is studied. Tissue cultures of tobacco grown for 12 weeks in contact with lunar material from Apollo 12 flight contained 21 to 35 percent more total pigment than control tissues. No differences were noted in the fresh or dry weight of the experimental and control samples.

  14. Nanomechanical strength mechanisms of hierarchical biological materials and tissues.

    Science.gov (United States)

    Buehler, Markus J; Ackbarow, Theodor

    2008-12-01

    Biological protein materials (BPMs), intriguing hierarchical structures formed by assembly of chemical building blocks, are crucial for critical functions of life. The structural details of BPMs are fascinating: They represent a combination of universally found motifs such as alpha-helices or beta-sheets with highly adapted protein structures such as cytoskeletal networks or spider silk nanocomposites. BPMs combine properties like strength and robustness, self-healing ability, adaptability, changeability, evolvability and others into multi-functional materials at a level unmatched in synthetic materials. The ability to achieve these properties depends critically on the particular traits of these materials, first and foremost their hierarchical architecture and seamless integration of material and structure, from nano to macro. Here, we provide a brief review of this field and outline new research directions, along with a review of recent research results in the development of structure-property relationships of biological protein materials exemplified in a study of vimentin intermediate filaments.

  15. Equivalent Lagrangians

    International Nuclear Information System (INIS)

    Hojman, S.

    1982-01-01

    We present a review of the inverse problem of the Calculus of Variations, emphasizing the ambiguities which appear due to the existence of equivalent Lagrangians for a given classical system. In particular, we analyze the properties of equivalent Lagrangians in the multidimensional case, we study the conditions for the existence of a variational principle for (second as well as first order) equations of motion and their solutions, we consider the inverse problem of the Calculus of Variations for singular systems, we state the ambiguities which emerge in the relationship between symmetries and conserved quantities in the case of equivalent Lagrangians, we discuss the problems which appear in trying to quantize classical systems which have different equivalent Lagrangians, we describe the situation which arises in the study of equivalent Lagrangians in field theory and finally, we present some unsolved problems and discussion topics related to the content of this article. (author)

  16. Penelope simulation of electron beams 6 MeV from a linear accelerator for studies in different materials equivalent to human body

    International Nuclear Information System (INIS)

    Apaza V, D.; Cardena R, R.; Cayllahua Q, F.; Vega R, J.; Urquizo B, R.

    2015-10-01

    In systems of radiotherapy treatment for cancer, always looking to maximize the radiation dose on the target (tumor) and minimize to the organs at risk or healthy, so they resort to using electron beams that have properties and characteristics of higher dose deposition at fixed depths, directing and focusing the higher dose in the tumor, without harming healthy tissues to which seeks to radiate in the least possible. Simulating the interaction of electron beams with different equivalent tissues to the human body leads to a better dosimetric evaluation, improving the quality of treatment planning. The aim of this study is the comparison from the characterization of several equivalent tissues to the human body such as soft tissue, bone and lung. Based on the simulation of a calibration beam in water phantom with Penelope code and compared with the results of the calibration curves of beams in water vat by a linear accelerator Elekta Synergy of Hospital Nacional Carlos Alberto Seguin Escobedo EsSalud of Arequipa (Peru). From this to evaluate the behavior of electron beams in a homogeneous medium and then further evaluation in the human body homogeneities, for better evaluation and specific treatment planning. (Author)

  17. Progress on materials and scaffold fabrications applied to esophageal tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Qiuxiang; Shi, Peina; Gao, Mongna; Yu, Xuechan; Liu, Yuxin; Luo, Ling; Zhu, Yabin, E-mail: zhuyabin@nbu.edu.cn

    2013-05-01

    The mortality rate from esophageal disease like atresia, carcinoma, tracheoesophageal fistula, etc. is increasing rapidly all over the world. Traditional therapies such as surgery, radiotherapy or chemotherapy have been met with very limited success resulting in reduced survival rate and quality of patients' life. Tissue-engineered esophagus, a novel substitute possessing structure and function similar to native tissue, is believed to be an effective therapy and a promising replacement in the future. However, research on esophageal tissue engineering is still at an early stage. Considerable research has been focused on developing ideal scaffolds with optimal materials and methods of fabrication. This article gives a review of materials and scaffold fabrications currently applied in esophageal tissue engineering research. - Highlights: ► Natural and synthesized materials are being developed as scaffold matrices. ► Several technologies have been applied to reconstruct esophagus tissue scaffold. ► Tissue-engineered esophagus is a promising artificial replacement.

  18. SU-F-J-193: Efficient Dose Extinction Method for Water Equivalent Path Length (WEPL) of Real Tissue Samples for Validation of CT HU to Stopping Power Conversion

    International Nuclear Information System (INIS)

    Zhang, R; Baer, E; Jee, K; Sharp, G; Flanz, J; Lu, H

    2016-01-01

    Purpose: For proton therapy, an accurate model of CT HU to relative stopping power (RSP) conversion is essential. In current practice, validation of these models relies solely on measurements of tissue substitutes with standard compositions. Validation based on real tissue samples would be much more direct and can address variations between patients. This study intends to develop an efficient and accurate system based on the concept of dose extinction to measure WEPL and retrieve RSP in biological tissue in large number of types. Methods: A broad AP proton beam delivering a spread out Bragg peak (SOBP) is used to irradiate the samples with a Matrixx detector positioned immediately below. A water tank was placed on top of the samples, with the water level controllable in sub-millimeter by a remotely controlled dosing pump. While gradually lowering the water level with beam on, the transmission dose was recorded at 1 frame/sec. The WEPL were determined as the difference between the known beam range of the delivered SOBP (80%) and the water level corresponding to 80% of measured dose profiles in time. A Gammex 467 phantom was used to test the system and various types of biological tissue was measured. Results: RSP for all Gammex inserts, expect the one made with lung-450 material (<2% error), were determined within ±0.5% error. Depends on the WEPL of investigated phantom, a measurement takes around 10 min, which can be accelerated by a faster pump. Conclusion: Based on the concept of dose extinction, a system was explored to measure WEPL efficiently and accurately for a large number of samples. This allows the validation of CT HU to stopping power conversions based on large number of samples and real tissues. It also allows the assessment of beam uncertainties due to variations over patients, which issue has never been sufficiently studied before.

  19. SU-F-J-193: Efficient Dose Extinction Method for Water Equivalent Path Length (WEPL) of Real Tissue Samples for Validation of CT HU to Stopping Power Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R; Baer, E; Jee, K; Sharp, G; Flanz, J; Lu, H [Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States)

    2016-06-15

    Purpose: For proton therapy, an accurate model of CT HU to relative stopping power (RSP) conversion is essential. In current practice, validation of these models relies solely on measurements of tissue substitutes with standard compositions. Validation based on real tissue samples would be much more direct and can address variations between patients. This study intends to develop an efficient and accurate system based on the concept of dose extinction to measure WEPL and retrieve RSP in biological tissue in large number of types. Methods: A broad AP proton beam delivering a spread out Bragg peak (SOBP) is used to irradiate the samples with a Matrixx detector positioned immediately below. A water tank was placed on top of the samples, with the water level controllable in sub-millimeter by a remotely controlled dosing pump. While gradually lowering the water level with beam on, the transmission dose was recorded at 1 frame/sec. The WEPL were determined as the difference between the known beam range of the delivered SOBP (80%) and the water level corresponding to 80% of measured dose profiles in time. A Gammex 467 phantom was used to test the system and various types of biological tissue was measured. Results: RSP for all Gammex inserts, expect the one made with lung-450 material (<2% error), were determined within ±0.5% error. Depends on the WEPL of investigated phantom, a measurement takes around 10 min, which can be accelerated by a faster pump. Conclusion: Based on the concept of dose extinction, a system was explored to measure WEPL efficiently and accurately for a large number of samples. This allows the validation of CT HU to stopping power conversions based on large number of samples and real tissues. It also allows the assessment of beam uncertainties due to variations over patients, which issue has never been sufficiently studied before.

  20. Modeling and Characterization of Capacitive Elements With Tissue as Dielectric Material for Wireless Powering of Neural Implants.

    Science.gov (United States)

    Erfani, Reza; Marefat, Fatemeh; Sodagar, Amir M; Mohseni, Pedram

    2018-05-01

    This paper reports on the modeling and characterization of capacitive elements with tissue as the dielectric material, representing the core building block of a capacitive link for wireless power transfer to neural implants. Each capacitive element consists of two parallel plates that are aligned around the tissue layer and incorporate a grounded, guarded, capacitive pad to mitigate the adverse effect of stray capacitances and shield the plates from external interfering electric fields. The plates are also coated with a biocompatible, insulating, coating layer on the inner side of each plate in contact with the tissue. A comprehensive circuit model is presented that accounts for the effect of the coating layers and is validated by measurements of the equivalent capacitance as well as impedance magnitude/phase of the parallel plates over a wide frequency range of 1 kHz-10 MHz. Using insulating coating layers of Parylene-C at a thickness of and Parylene-N at a thickness of deposited on two sets of parallel plates with different sizes and shapes of the guarded pad, our modeling and characterization results accurately capture the effect of the thickness and electrical properties of the coating layers on the behavior of the capacitive elements over frequency and with different tissues.

  1. Gradient Material Strategies for Hydrogel Optimization in Tissue Engineering Applications

    Science.gov (United States)

    2018-01-01

    Although a number of combinatorial/high-throughput approaches have been developed for biomaterial hydrogel optimization, a gradient sample approach is particularly well suited to identify hydrogel property thresholds that alter cellular behavior in response to interacting with the hydrogel due to reduced variation in material preparation and the ability to screen biological response over a range instead of discrete samples each containing only one condition. This review highlights recent work on cell–hydrogel interactions using a gradient material sample approach. Fabrication strategies for composition, material and mechanical property, and bioactive signaling gradient hydrogels that can be used to examine cell–hydrogel interactions will be discussed. The effects of gradients in hydrogel samples on cellular adhesion, migration, proliferation, and differentiation will then be examined, providing an assessment of the current state of the field and the potential of wider use of the gradient sample approach to accelerate our understanding of matrices on cellular behavior. PMID:29485612

  2. Apollo 12 lunar material - Effects on lipid levels of tobacco tissue cultures.

    Science.gov (United States)

    Weete, J. D.; Walkinshaw, C. H.; Laseter, J. L.

    1972-01-01

    Tobacco tissue cultures grown in contact with lunar material from Apollo 12, for a 12-week period, resulted in fluctuations of both the relative and absolute concentrations of endogenous sterols and fatty acids. The experimental tissues contained higher concentrations of sterols than the controls did. The ratio of campesterol to stigmasterol was greater than 1 in control tissues, but less than 1 in the experimental tissues after 3 weeks. High relative concentrations (17.1 to 22.2 per cent) of an unidentified compound or compounds were found only in control tissues that were 3 to 9 weeks of age.

  3. Nanoscale tissue engineering: spatial control over cell-materials interactions

    Science.gov (United States)

    Wheeldon, Ian; Farhadi, Arash; Bick, Alexander G.; Jabbari, Esmaiel; Khademhosseini, Ali

    2011-01-01

    Cells interact with the surrounding environment by making tens to hundreds of thousands of nanoscale interactions with extracellular signals and features. The goal of nanoscale tissue engineering is to harness the interactions through nanoscale biomaterials engineering in order to study and direct cellular behaviors. Here, we review the nanoscale tissue engineering technologies for both two- and three-dimensional studies (2- and 3D), and provide a holistic overview of the field. Techniques that can control the average spacing and clustering of cell adhesion ligands are well established and have been highly successful in describing cell adhesion and migration in 2D. Extension of these engineering tools to 3D biomaterials has created many new hydrogel and nanofiber scaffolds technologies that are being used to design in vitro experiments with more physiologically relevant conditions. Researchers are beginning to study complex cell functions in 3D, however, there is a need for biomaterials systems that provide fine control over the nanoscale presentation of bioactive ligands in 3D. Additionally, there is a need for 2- and 3D techniques that can control the nanoscale presentation of multiple bioactive ligands and the temporal changes in cellular microenvironment. PMID:21451238

  4. Nanoscale tissue engineering: spatial control over cell-materials interactions

    International Nuclear Information System (INIS)

    Wheeldon, Ian; Farhadi, Arash; Bick, Alexander G; Khademhosseini, Ali; Jabbari, Esmaiel

    2011-01-01

    Cells interact with the surrounding environment by making tens to hundreds of thousands of nanoscale interactions with extracellular signals and features. The goal of nanoscale tissue engineering is to harness these interactions through nanoscale biomaterials engineering in order to study and direct cellular behavior. Here, we review two- and three-dimensional (2- and 3D) nanoscale tissue engineering technologies, and provide a holistic overview of the field. Techniques that can control the average spacing and clustering of cell adhesion ligands are well established and have been highly successful in describing cell adhesion and migration in 2D. Extension of these engineering tools to 3D biomaterials has created many new hydrogel and nanofiber scaffold technologies that are being used to design in vitro experiments with more physiologically relevant conditions. Researchers are beginning to study complex cell functions in 3D. However, there is a need for biomaterials systems that provide fine control over the nanoscale presentation of bioactive ligands in 3D. Additionally, there is a need for 2- and 3D techniques that can control the nanoscale presentation of multiple bioactive ligands and that can control the temporal changes in the cellular microenvironment. (topical review)

  5. Estimating raw material equivalents on a macro-level: comparison of multi-regional input-output analysis and hybrid LCI-IO.

    Science.gov (United States)

    Schoer, Karl; Wood, Richard; Arto, Iñaki; Weinzettel, Jan

    2013-12-17

    The mass of material consumed by a population has become a useful proxy for measuring environmental pressure. The "raw material equivalents" (RME) metric of material consumption addresses the issue of including the full supply chain (including imports) when calculating national or product level material impacts. The RME calculation suffers from data availability, however, as quantitative data on production practices along the full supply chain (in different regions) is required. Hence, the RME is currently being estimated by three main approaches: (1) assuming domestic technology in foreign economies, (2) utilizing region-specific life-cycle inventories (in a hybrid framework), and (3) utilizing multi-regional input-output (MRIO) analysis to explicitly cover all regions of the supply chain. While the first approach has been shown to give inaccurate results, this paper focuses on the benefits and costs of the latter two approaches. We analyze results from two key (MRIO and hybrid) projects modeling raw material equivalents, adjusting the models in a stepwise manner in order to quantify the effects of individual conceptual elements. We attempt to isolate the MRIO gap, which denotes the quantitative impact of calculating the RME of imports by an MRIO approach instead of the hybrid model, focusing on the RME of EU external trade imports. While, the models give quantitatively similar results, differences become more pronounced when tracking more detailed material flows. We assess the advantages and disadvantages of the two approaches and look forward to ways to further harmonize data and approaches.

  6. Cellulose-based materials as scaffolds for tissue engineering

    Czech Academy of Sciences Publication Activity Database

    Novotná, Katarína; Havelka, P.; Sopuch, T.; Kolářová, K.; Vosmanská, V.; Lisá, Věra; Švorčík, V.; Bačáková, Lucie

    2013-01-01

    Roč. 20, č. 5 (2013), s. 2263-2278 ISSN 0969-0239 R&D Projects: GA ČR(CZ) GAP108/12/1168; GA MPO(CZ) 2A-1TP1/073 Institutional research plan: CEZ:AV0Z50110509 Institutional support: RVO:67985823 Keywords : polysacharide materials * oxidized cellulose * vascular smooth muscle cells * chitosan Subject RIV: FR - Pharmacology ; Medidal Chemistry Impact factor: 3.033, year: 2013

  7. Soft tissue augmentation techniques and materials used in the oral cavity : an overview

    NARCIS (Netherlands)

    Wolff, J.; Farré-Guasch, E.; Sándor, G.K.; Gibbs, S.; Jager, D.J.; Forouzanfar, T.

    2016-01-01

    Purpose: Oral soft tissue augmentation or grafting procedures are often necessary to achieve proper wound closure after deficits resulting from tumor excision, clefts, trauma, dental implants, and tooth recessions. Materials and Methods: Autologous soft tissue grafts still remain the gold standard

  8. Engineering spinal fusion: evaluating ceramic materials for cell based tissue engineered approaches

    NARCIS (Netherlands)

    Wilson, C.E.

    2011-01-01

    The principal aim of this thesis was to advance the development of tissue engineered posterolateral spinal fusion by investigating the potential of calcium phosphate ceramic materials to support cell based tissue engineered bone formation. This was accomplished by developing several novel model

  9. Hard tissue regeneration using bone substitutes: an update on innovations in materials.

    Science.gov (United States)

    Sarkar, Swapan Kumar; Lee, Byong Taek

    2015-05-01

    Bone is a unique organ composed of mineralized hard tissue, unlike any other body part. The unique manner in which bone can constantly undergo self-remodeling has created interesting clinical approaches to the healing of damaged bone. Healing of large bone defects is achieved using implant materials that gradually integrate with the body after healing is completed. Such strategies require a multidisciplinary approach by material scientists, biological scientists, and clinicians. Development of materials for bone healing and exploration of the interactions thereof with the body are active research areas. In this review, we explore ongoing developments in the creation of materials for regenerating hard tissues.

  10. Response of human limbal epithelial cells to wounding on 3D RAFT tissue equivalents: effect of airlifting and human limbal fibroblasts.

    Science.gov (United States)

    Massie, Isobel; Levis, Hannah J; Daniels, Julie T

    2014-10-01

    Limbal epithelial stem cell deficiency can cause blindness but may be treated by human limbal epithelial cell (hLE) transplantation, normally on human amniotic membrane. Clinical outcomes using amnion can be unreliable and so we have developed an alternative tissue equivalent (TE), RAFT (Real Architecture for 3D Tissue), which supports hLE expansion, and stratification when airlifted. Human limbal fibroblasts (hLF) may be incorporated into RAFT TEs, where they support overlying hLE and improve phenotype. However, the impact of neither airlifting nor hLF on hLE function has been investigated. hLE on RAFT TEs (±hLF and airlifting) were wounded using heptanol and re-epithelialisation (fluorescein diacetate staining), and percentage putative stem cell marker p63α and proliferative marker Ki67 expression (wholemount immunohistochemistry), measured. Airlifted, hLF- RAFT TEs were unable to close the wound and p63α expression was 7 ± 0.2% after wounding. Conversely, non-airlifted, hLF- RAFT TEs closed the wound within 9 days and p63α expression was higher at 22 ± 5% (p < 0.01). hLE on both hLF- and hLF+ RAFT TEs (non-airlifted) closed the wound and p63α expression was 26 ± 8% and 36 ± 3% respectively (ns). Ki67 expression by hLE increased from 1.3 ± 0.5% before wounding to 7.89 ± 2.53% post-wounding for hLF- RAFT TEs (p < 0.01), and 0.8 ± 0.08% to 17.68 ± 10.88% for hLF+ RAFT TEs (p < 0.05), suggesting that re-epithelialisation was a result of proliferation. These data suggest that neither airlifting nor hLF are necessarily required to maintain a functional epithelium on RAFT TEs, thus simplifying and shortening the production process. This is important when working towards clinical application of regenerative medicine products. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Limbal Fibroblasts Maintain Normal Phenotype in 3D RAFT Tissue Equivalents Suggesting Potential for Safe Clinical Use in Treatment of Ocular Surface Failure.

    Science.gov (United States)

    Massie, Isobel; Dale, Sarah B; Daniels, Julie T

    2015-06-01

    Limbal epithelial stem cell deficiency can cause blindness, but transplantation of these cells on a carrier such as human amniotic membrane can restore vision. Unfortunately, clinical graft manufacture using amnion can be inconsistent. Therefore, we have developed an alternative substrate, Real Architecture for 3D Tissue (RAFT), which supports human limbal epithelial cells (hLE) expansion. Epithelial organization is improved when human limbal fibroblasts (hLF) are incorporated into RAFT tissue equivalent (TE). However, hLF have the potential to transdifferentiate into a pro-scarring cell type, which would be incompatible with therapeutic transplantation. The aim of this work was to assess the scarring phenotype of hLF in RAFT TEs in hLE+ and hLE- RAFT TEs and in nonairlifted and airlifted RAFT TEs. Diseased fibroblasts (dFib) isolated from the fibrotic conjunctivae of ocular mucous membrane pemphigoid (Oc-MMP) patients were used as a pro-scarring positive control against which hLF were compared using surrogate scarring parameters: matrix metalloproteinase (MMP) activity, de novo collagen synthesis, α-smooth muscle actin (α-SMA) expression, and transforming growth factor-β (TGF-β) secretion. Normal hLF and dFib maintained different phenotypes in RAFT TE. MMP-2 and -9 activity, de novo collagen synthesis, and α-SMA expression were all increased in dFib cf. normal hLF RAFT TEs, although TGF-β1 secretion did not differ between normal hLF and dFib RAFT TEs. Normal hLF do not progress toward a scarring-like phenotype during culture in RAFT TEs and, therefore, may be safe to include in therapeutic RAFT TE, where they can support hLE, although in vivo work is required to confirm this. dFib RAFT TEs (used in this study as a positive control) may be useful toward the development of an ex vivo disease model of Oc-MMP.

  12. Thermoluminescence and radioluminescence properties of tissue equivalent Cu-doped Li{sub 2}B{sub 4}O{sub 7} for radiation dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Z, E.; Furetta, C. [UNAM, Instituto de Ciencias Nucleares, Apdo. Postal 70543, 04510 Mexico D. F. (Mexico); Marcazzo, J.; Santiago, M. [Instituto de Fisica Arroyo Seco / UNICEN, Gral. Pinto 399, 7000 Tandil, Buenos Aires (Argentina); Guarneros, C. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Altamira Km 14.5, 896000 Altamira, Tamaulipas (Mexico); Pacio, M. [Benemerita Universidad Autonoma de Puebla, Instituto de Ciencias, Centro de Investigacion en Dispositivos Semiconductores, Av. 14 Sur, 72570 Puebla, Pue. (Mexico); Palomino, R., E-mail: ecruz@nucleares.unam.mx [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Fisico-Matematicas, Av. San Claudio y 18 Sur, 72570 Puebla Pue. (Mexico)

    2015-10-15

    Thermoluminescence (Tl) and radioluminescence (Rl) properties of lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) doped with different concentration of copper (0.25, 0.5, 1 wt %) under gamma and beta irradiation has been investigated. The feasibility of using this borate in radiation dosimetry at low doses has been evaluated. Tissue equivalent Li{sub 2}B{sub 4}O{sub 7} was prepared by solid state reaction using mixing stoichiometric compositions of lithium carbonate (Li{sub 2}CO{sub 3}) and boric acid (H{sub 3}BO{sub 3}) and a solution of CuCl{sub 2} as dopant. The glow curve, of the most efficient copper doped borate (Li{sub 2}B{sub 4}O{sub 7}:Cu 0.5 wt %), shows a main stable peak centered at 225 degrees C and a second low temperature peak centered at 80 degrees C. The low temperature peak disappears completely after 24 hours of storage in darkness and at room temperature or after an annealing at 120 degrees C for 10 seconds. The main peak of the Li{sub 2}B{sub 4}O{sub 7}:Cu remains constant. The Tl response of Li{sub 2}B{sub 4}O{sub 7}:Cu shows good linearity in the analyzed dose range. The stability and repeatability of Rl signals of the borate have been studied and the Li{sub 2}B{sub 4}O{sub 7}:Cu (0.5 wt %) shown the higher Rl emission and a stable and repetitive response. Results show that Li{sub 2}B{sub 4}O{sub 7}:Cu has prospects to be used in gamma and beta radiation dosimetry. (Author)

  13. Beta-ray depth dose in tissue equivalent material due to gaseous radioactive effluents from nuclear power plants

    International Nuclear Information System (INIS)

    Schadt, W.W.

    1978-01-01

    The magnitude of the absorbed dose to skin from beta particles emitted by the radionuclides in gaseous effluents from boiling water nuclear power reactors is investigated in this dissertation. Using the radionuclide release patterns of F. Brutschy and the beta dosimetry methods of M. Berger, an equation is derived which gives the dose rate in rads per day when the total radionuclide concentration is one microcurie per gram of air. The coefficients in the equation are presented for a wide range of reactor gas hold-up times (48 minutes to 6 days) and plume environmental transit time (0.5 to 60 minutes). The beta dose rates at the skin surface are found to range from 3.9 to 26.7 rads per day. An upper limit of the relative standard deviation in the dose rate is estimated to be 30 percent. The techniques used to develop the equation are applied to data from the Millstone Nuclear Power Station obtained during the summer of 1972. The beta dose at a site 1.7 miles from the reactor is determined to have been 675 millirads per year at the skin surface and 476 millirads per year at a depth of 200 micrometers. At a site 5.1 miles from the reactor these dose rates were 138 and 100 millirads per year respectively

  14. Scale-up of nature’s tissue weaving algorithms to engineer advanced functional materials

    Science.gov (United States)

    Ng, Joanna L.; Knothe, Lillian E.; Whan, Renee M.; Knothe, Ulf; Tate, Melissa L. Knothe

    2017-01-01

    We are literally the stuff from which our tissue fabrics and their fibers are woven and spun. The arrangement of collagen, elastin and other structural proteins in space and time embodies our tissues and organs with amazing resilience and multifunctional smart properties. For example, the periosteum, a soft tissue sleeve that envelops all nonarticular bony surfaces of the body, comprises an inherently “smart” material that gives hard bones added strength under high impact loads. Yet a paucity of scalable bottom-up approaches stymies the harnessing of smart tissues’ biological, mechanical and organizational detail to create advanced functional materials. Here, a novel approach is established to scale up the multidimensional fiber patterns of natural soft tissue weaves for rapid prototyping of advanced functional materials. First second harmonic generation and two-photon excitation microscopy is used to map the microscopic three-dimensional (3D) alignment, composition and distribution of the collagen and elastin fibers of periosteum, the soft tissue sheath bounding all nonarticular bone surfaces in our bodies. Then, using engineering rendering software to scale up this natural tissue fabric, as well as multidimensional weaving algorithms, macroscopic tissue prototypes are created using a computer-controlled jacquard loom. The capacity to prototype scaled up architectures of natural fabrics provides a new avenue to create advanced functional materials.

  15. Estimation of collective effective dose equivalent from environmental radiation and radioactive materials in Japan. A preliminary study

    International Nuclear Information System (INIS)

    Maruyama, Takashi; Noda, Yutaka; Takeshita, Mitsue; Iwai, Kazuo.

    1994-01-01

    The peaceful uses of nuclear power and radiations have been developed into a stage of practical applications for human life. Radiation causes harmful effects to human beings, although human beings receives a number of invaluable benefits from the nuclear energy and the uses of radiation. In order to examine the optimization of radiation protection in these practices, collective effective dose equivalent from environmental exposures due to natural and artificial radiations have been preliminarily evaluated using most recent data. The resultant collective doses were compared with those from medical and occupational exposures. It is noted that, in Japan, the collective effective dose from environmental radiation sources can be approximately same to that from medical exposure. (author)

  16. Comparison of the dynamic behaviour of brain tissue and two model materials

    NARCIS (Netherlands)

    Brands, D.W.A.; Bovendeerd, P.H.M.; Peters, G.W.M.; Wismans, J.S.H.M.; Paas, M.H.J.W.; Bree, van J.L.M.J.; Brands, D.W.A.

    1999-01-01

    Linear viscoelastic material parameters of porcine brain tissue and two brain substitute/ materials for use in mechanical head models (edible bone gelatin and dielectric silicone gel) were determined in small deformation, oscillatory shear experiments. Frequencies to 1000 Hertz could be obtained

  17. Theoretical and experimental estimation of the lead equivalent for some materials used in finishing of diagnostic x-ray rooms in Syria

    International Nuclear Information System (INIS)

    Shwekani, R.; Suman, H.; Takeyeddin, M.; Suleiman, J.

    2003-11-01

    This work aimed at estimating the lead equivalent values for finishing materials, which are frequently used in Syria. These materials are ceramic and marble. In the past, many studies were performed to estimate the lead equivalent values for different types of bricks, which are widely used in Syria. Therefore, this work could be considered as a follow up in order to be able to estimate the structural shielding of diagnostic X-ray rooms and accurately perform the shielding calculations to reduce unnecessary added shields. The work was done in two ways, theoretical using MCNP computer code and experimental in the secondary standard laboratory. The theoretical work was focused on generalizing the results scope to cover the real existing variations in the structure of the materials used in the finishing or the variations in the X-ray machines. Therefore, quantifying different sources of errors were strongly focused on using the methodology of sensitivity analysis. While, the experiment measurements were performed to make sure that their results will be within the error range produced by the theoretical study. The obtained results showed a strong correlation between theoretical and experimental data. (author)

  18. Evaluation of the in vitro biocompatibility of polymeric materials for the regeneration of cutaneous tissue

    International Nuclear Information System (INIS)

    Escudero Castellanos, A.

    2016-01-01

    The problems associated with medical cases of functional tissue loss or organ failure are destructive and expensive, even more frequent than could be perceived, sometime if not properly treated, even deathly. Tissue engineering is an interdisciplinary field that emerged to address these clinical problems, it is based on researching and development of biomaterials that have evolved along with areas such as cell biology, molecular and materials science and engineering. Today, the technique is based on seeding cells onto prefabricated scaffold biomaterials, like the hydrogels, that are three-dimensional networks with hydrophilic properties. These materials are characterized as being porous and sticky, favoring the support for the proliferation of certain cells in order to lead the regeneration of injured tissue. As a prerequisite for the use of materials in tissue engineering is testing biocompatibility which is the ability of the bio material to allow contact with any tissue, existing a favorable host response, accepting it as their own and restoring previously lost function. The first step for evaluating biocompatibility is to perform the in vitro assays. These assays have been demonstrated more reproducibility and predictability than in vivo assays, therefore the in vitro assays are used to produce high quality scaffolds and testing on animals as less as possible. This test is essential to establish the benefits and limitations of biomaterials tested in order to improve the scaffolds. This work will focus on assessing the biocompatibility of three polymeric materials with potential use in tissue engineering by means of cytological compatibility tests and hemo compatibility tests. Furthermore, disinfection techniques and gamma sterilization were evaluated to produce sterile materials that can be used in tissue engineering. (Author)

  19. Construction of computational program of aging in insulating materials for searching reversed sequential test conditions to give damage equivalent to simultaneous exposure of heat and radiation

    International Nuclear Information System (INIS)

    Fuse, Norikazu; Homma, Hiroya; Okamoto, Tatsuki

    2013-01-01

    Two consecutive numerical calculations on degradation of polymeric insulations under thermal and radiation environment are carried out to simulate so-called reversal sequential acceleration test. The aim of the calculation is to search testing conditions which provide material damage equivalent to the case of simultaneous exposure of heat and radiation. At least following four parameters are needed to be considered in the sequential method; dose rate and exposure time in radiation, as well as temperature and aging time in heating. The present paper discusses the handling of these parameters and shows some trial calculation results. (author)

  20. An Earth-Based Equivalent Low Stretch Apparatus to Assess Material Flammability for Microgravity & Extraterrestrial Fire-Safety Applications

    Science.gov (United States)

    Olson, S. L.; Beeson, H.; Haas, J.

    2001-01-01

    One of the performance goals for NASA's enterprise of Human Exploration and Development of Space (HEDS) is to develop methods, data bases, and validating tests for material flammability characterization, hazard reduction, and fire detection/suppression strategies for spacecraft and extraterrestrial habitats. This work addresses these needs by applying the fundamental knowledge gained from low stretch experiments to the development of a normal gravity low stretch material flammability test method. The concept of the apparatus being developed uses the low stretch geometry to simulate the conditions of the extraterrestrial environment through proper scaling of the sample dimensions to reduce the buoyant stretch in normal gravity. The apparatus uses controlled forced-air flow to augment the low stretch to levels which simulate Lunar or Martian gravity levels. In addition, the effect of imposed radiant heat flux on material flammability can be studied with the cone heater. After breadboard testing, the apparatus will be integrated into NASA's White Sands Test Facility's Atmosphere-Controlled Cone Calorimeter for evaluation as a new materials screening test method.

  1. Gyrokinetic equivalence

    International Nuclear Information System (INIS)

    Parra, Felix I; Catto, Peter J

    2009-01-01

    We compare two different derivations of the gyrokinetic equation: the Hamiltonian approach in Dubin D H E et al (1983 Phys. Fluids 26 3524) and the recursive methodology in Parra F I and Catto P J (2008 Plasma Phys. Control. Fusion 50 065014). We prove that both approaches yield the same result at least to second order in a Larmor radius over macroscopic length expansion. There are subtle differences in the definitions of some of the functions that need to be taken into account to prove the equivalence.

  2. Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials.

    Science.gov (United States)

    Kemerink, Gerrit J; Visser, Mariëlle G W; Franssen, Renee; Beijer, Emiel; Zamburlini, Mariangela; Halders, Servé G E A; Brans, Boudewijn; Mottaghy, Felix M; Teule, Gerrit J J

    2011-05-01

    The aim of this study was to investigate the effect of positron range on visualization and quantification in (18)F, (68)Ga and (124)I positron emission tomography (PET)/CT of lung-like tissue. Different sources were measured in air, in lung-equivalent foams and in water, using a clinical PET/CT and a microPET system. Intensity profiles and curves with the cumulative number of annihilations were derived and numerically characterized. (68)Ga and (124)I gave similar results. Their intensity profiles in lung-like foam had a peak similar to that for (18)F, and tails of very low intensity, but extending over distances of centimetres and containing a large fraction of all annihilations. For 90% recovery, volumes of interest with diameters up to 50 mm were required, and recovery within the 10% intensity isocontour was as low as 30%. In contrast, tailing was minor for (18)F. Lung lesions containing (18)F, (68)Ga or (124)I will be visualized similarly, and at least as sharp as in soft tissue. Nevertheless, for quantification of (68)Ga and (124)I large volumes of interest are needed for complete activity recovery. For clinical studies containing noise and background, new quantification approaches may have to be developed.

  3. Is Graphene a Promising Nano-Material for Promoting Surface Modification of Implants or Scaffold Materials in Bone Tissue Engineering?

    Science.gov (United States)

    Gu, Ming; Liu, Yunsong; Chen, Tong; Du, Feng; Zhao, Xianghui; Xiong, Chunyang

    2014-01-01

    Bone tissue engineering promises to restore bone defects that are caused by severe trauma, congenital malformations, tumors, and nonunion fractures. How to effectively promote the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) or seed cells has become a hot topic in this field. Many researchers are studying the ways of conferring a pro-osteodifferentiation or osteoinductive capability on implants or scaffold materials, where osteogenesis of seed cells is promoted. Graphene (G) provides a new kind of coating material that may confer the pro-osteodifferentiation capability on implants and scaffold materials by surface modification. Here, we review recent studies on the effects of graphene on surface modifications of implants or scaffold materials. The ability of graphene to improve the mechanical and biological properties of implants or scaffold materials, such as nitinol and carbon nanotubes, and its ability to promote the adhesion, proliferation, and osteogenic differentiation of MSCs or osteoblasts have been demonstrated in several studies. Most previous studies were performed in vitro, but further studies will explore the mechanisms of graphene's effects on bone regeneration, its in vivo biocompatibility, its ability to promote osteodifferentiation, and its potential applications in bone tissue engineering. PMID:24447041

  4. Is graphene a promising nano-material for promoting surface modification of implants or scaffold materials in bone tissue engineering?

    Science.gov (United States)

    Gu, Ming; Liu, Yunsong; Chen, Tong; Du, Feng; Zhao, Xianghui; Xiong, Chunyang; Zhou, Yongsheng

    2014-10-01

    Bone tissue engineering promises to restore bone defects that are caused by severe trauma, congenital malformations, tumors, and nonunion fractures. How to effectively promote the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) or seed cells has become a hot topic in this field. Many researchers are studying the ways of conferring a pro-osteodifferentiation or osteoinductive capability on implants or scaffold materials, where osteogenesis of seed cells is promoted. Graphene (G) provides a new kind of coating material that may confer the pro-osteodifferentiation capability on implants and scaffold materials by surface modification. Here, we review recent studies on the effects of graphene on surface modifications of implants or scaffold materials. The ability of graphene to improve the mechanical and biological properties of implants or scaffold materials, such as nitinol and carbon nanotubes, and its ability to promote the adhesion, proliferation, and osteogenic differentiation of MSCs or osteoblasts have been demonstrated in several studies. Most previous studies were performed in vitro, but further studies will explore the mechanisms of graphene's effects on bone regeneration, its in vivo biocompatibility, its ability to promote osteodifferentiation, and its potential applications in bone tissue engineering.

  5. Determination of optical properties of tissue and other bio-materials

    CSIR Research Space (South Africa)

    Singh, A

    2008-11-01

    Full Text Available appears less diffusively scattered. Determination of optical properties of tissue and other bio-materials A SINGH, AE KARSTEN, JS DAM CSIR National Laser Centre, Biophotonics Group PO Box 395, Pretoria, 0001, South Africa Email: ASingh1@csir.co.za K...

  6. Incidence of late rectal bleeding in high-dose conformal radiotherapy of prostate cancer using equivalent uniform dose-based and dose-volume-based normal tissue complication probability models

    International Nuclear Information System (INIS)

    Soehn, Matthias; Yan Di; Liang Jian; Meldolesi, Elisa; Vargas, Carlos; Alber, Markus

    2007-01-01

    Purpose: Accurate modeling of rectal complications based on dose-volume histogram (DVH) data are necessary to allow safe dose escalation in radiotherapy of prostate cancer. We applied different equivalent uniform dose (EUD)-based and dose-volume-based normal tissue complication probability (NTCP) models to rectal wall DVHs and follow-up data for 319 prostate cancer patients to identify the dosimetric factors most predictive for Grade ≥ 2 rectal bleeding. Methods and Materials: Data for 319 patients treated at the William Beaumont Hospital with three-dimensional conformal radiotherapy (3D-CRT) under an adaptive radiotherapy protocol were used for this study. The following models were considered: (1) Lyman model and (2) logit-formula with DVH reduced to generalized EUD (3) serial reconstruction unit (RU) model (4) Poisson-EUD model, and (5) mean dose- and (6) cutoff dose-logistic regression model. The parameters and their confidence intervals were determined using maximum likelihood estimation. Results: Of the patients, 51 (16.0%) showed Grade 2 or higher bleeding. As assessed qualitatively and quantitatively, the Lyman- and Logit-EUD, serial RU, and Poisson-EUD model fitted the data very well. Rectal wall mean dose did not correlate to Grade 2 or higher bleeding. For the cutoff dose model, the volume receiving > 73.7 Gy showed most significant correlation to bleeding. However, this model fitted the data more poorly than the EUD-based models. Conclusions: Our study clearly confirms a volume effect for late rectal bleeding. This can be described very well by the EUD-like models, of which the serial RU- and Poisson-EUD model can describe the data with only two parameters. Dose-volume-based cutoff-dose models performed worse

  7. Mixed field dose equivalent measuring instruments

    International Nuclear Information System (INIS)

    Brackenbush, L.W.; McDonald, J.C.; Endres, G.W.R.; Quam, W.

    1985-01-01

    In the past, separate instruments have been used to monitor dose equivalent from neutrons and gamma rays. It has been demonstrated that it is now possible to measure simultaneously neutron and gamma dose with a single instrument, the tissue equivalent proportional counter (TEPC). With appropriate algorithms dose equivalent can also be determined from the TEPC. A simple ''pocket rem meter'' for measuring neutron dose equivalent has already been developed. Improved algorithms for determining dose equivalent for mixed fields are presented. (author)

  8. A biocompatible hybrid material with simultaneous calcium and strontium release capability for bone tissue repair

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, J. Carlos [CICECO — Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Wacha, András [Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok körútja 2, Budapest 1117 (Hungary); Gomes, Pedro S. [Laboratory for Bone Metabolism and Regeneration, Faculdade de Medicina Dentária, Universidade do Porto (Portugal); Alves, Luís C. [C2TN, Instituto Superior Técnico, Universidade de Lisboa, E.N.10, 2695-066 Bobadela LRS (Portugal); Fernandes, M. Helena Vaz [CICECO — Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Salvado, Isabel M. Miranda, E-mail: isabelmsalvado@ua.pt [CICECO — Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Fernandes, M. Helena R. [Laboratory for Bone Metabolism and Regeneration, Faculdade de Medicina Dentária, Universidade do Porto (Portugal)

    2016-05-01

    The increasing interest in the effect of strontium in bone tissue repair has promoted the development of bioactive materials with strontium release capability. According to literature, hybrid materials based on the system PDMS–SiO{sub 2} have been considered a plausible alternative as they present a mechanical behavior similar to the one of the human bone. The main purpose of this study was to obtain a biocompatible hybrid material with simultaneous calcium and strontium release capability. A hybrid material, in the system PDMS–SiO{sub 2}–CaO–SrO, was prepared with the incorporation of 0.05 mol of titanium per mol of SiO{sub 2}. Calcium and strontium were added using the respective acetates as sources, following a sol–gel technique previously developed by the present authors. The obtained samples were characterized by FT-IR, solid-state NMR, and SAXS, and surface roughness was analyzed by 3D optical profilometry. In vitro studies were performed by immersion of the samples in Kokubo's SBF for different periods of time, in order to determine the bioactive potential of these hybrids. Surfaces of the immersed samples were observed by SEM, EDS and PIXE, showing the formation of calcium phosphate precipitates. Supernatants were analyzed by ICP, revealing the capability of the material to simultaneously fix phosphorus ions and to release calcium and strontium, in a concentration range within the values reported as suitable for the induction of the bone tissue repair. The material demonstrated to be cytocompatible when tested with MG63 osteoblastic cells, exhibiting an inductive effect on cell proliferation and alkaline phosphatase activity. - Highlights: • A hybrid PDMS–SiO{sub 2}–CaO–SrO material was prepared with the incorporation of Ti. • Sr was released in concentrations suitable for the induction of bone tissue repair. • The material demonstrated to be cytocompatible when tested with osteoblastic cells.

  9. Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

    Directory of Open Access Journals (Sweden)

    John G. Hardy

    2016-07-01

    Full Text Available Materials based on biodegradable polyesters, such as poly(butylene terephthalate (PBT or poly(butylene terephthalate-co-poly(alkylene glycol terephthalate (PBTAT, have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16, that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.

  10. Tissue mimicking materials for a multi-imaging modality prostate phantom

    International Nuclear Information System (INIS)

    D'Souza, Warren D.; Madsen, Ernest L.; Unal, Orhan; Vigen, Karl K.; Frank, Gary R.; Thomadsen, Bruce R.

    2001-01-01

    Materials that simultaneously mimic soft tissue in vivo for magnetic resonance imaging (MRI), ultrasound (US), and computed tomography (CT) for use in a prostate phantom have been developed. Prostate and muscle mimicking materials contain water, agarose, lipid particles, protein, Cu ++ , EDTA, glass beads, and thimerosal (preservative). Fat was mimicked with safflower oil suffusing a random mesh (network) of polyurethane. Phantom material properties were measured at 22 deg. C. (22 deg. C is a typical room temperature at which phantoms are used.) The values of material properties should match, as well as possible, the values for tissues at body temperature, 37 deg. C. For MRI, the primary properties of interest are T1 and T2 relaxations times, for US they are the attenuation coefficient, propagation speed, and backscatter, and for CT, the x-ray attenuation. Considering the large number of parameters to be mimicked, rather good agreement was found with actual tissue values obtained from the literature. Using published values for prostate parenchyma, T1 and T2 at 37 deg. C and 40 MHz are estimated to be about 1100 and 98 ms, respectively. The CT number for in vivo prostate is estimated to be 45 HU (Hounsfield units). The prostate mimicking material has a T1 of 937 ms and a T2 of 88 ms at 22 deg. C and 40 MHz; the propagation speed and attenuation coefficient slope are 1540 m/s and 0.36 dB/cm/MHz, respectively, and the CT number of tissue mimicking prostate is 43 HU. Tissue mimicking (TM) muscle differs from TM prostate in the amount of dry weight agarose, Cu ++ , EDTA, and the quality and quantity of glass beads. The 18 μm glass beads used in TM muscle increase US backscatter and US attenuation; the presence of the beads also has some effect on T1 but no effect on T2. The composition of tissue-mimicking materials developed is such that different versions can be placed in direct contact with one another in a phantom with no long term change in US, MRI, or CT

  11. Study on Material Parameters Identification of Brain Tissue Considering Uncertainty of Friction Coefficient

    Science.gov (United States)

    Guan, Fengjiao; Zhang, Guanjun; Liu, Jie; Wang, Shujing; Luo, Xu; Zhu, Feng

    2017-10-01

    Accurate material parameters are critical to construct the high biofidelity finite element (FE) models. However, it is hard to obtain the brain tissue parameters accurately because of the effects of irregular geometry and uncertain boundary conditions. Considering the complexity of material test and the uncertainty of friction coefficient, a computational inverse method for viscoelastic material parameters identification of brain tissue is presented based on the interval analysis method. Firstly, the intervals are used to quantify the friction coefficient in the boundary condition. And then the inverse problem of material parameters identification under uncertain friction coefficient is transformed into two types of deterministic inverse problem. Finally the intelligent optimization algorithm is used to solve the two types of deterministic inverse problems quickly and accurately, and the range of material parameters can be easily acquired with no need of a variety of samples. The efficiency and convergence of this method are demonstrated by the material parameters identification of thalamus. The proposed method provides a potential effective tool for building high biofidelity human finite element model in the study of traffic accident injury.

  12. Ultrashort pulse laser processing of hard tissue, dental restoration materials, and biocompatibles

    Science.gov (United States)

    Yousif, A.; Strassl, M.; Beer, F.; Verhagen, L.; Wittschier, M.; Wintner, E.

    2007-07-01

    During the last few years, ultra-short laser pulses have proven their potential for application in medical tissue treatment in many ways. In hard tissue ablation, their aptitude for material ablation with negligible collateral damage provides many advantages. Especially teeth representing an anatomically and physiologically very special region with less blood circulation and lower healing rates than other tissues require most careful treatment. Hence, overheating of the pulp and induction of microcracks are some of the most problematic issues in dental preparation. Up till now it was shown by many authors that the application of picosecond or femtosecond pulses allows to perform ablation with very low damaging potential also fitting to the physiological requirements indicated. Beside the short interaction time with the irradiated matter, scanning of the ultra-short pulse trains turned out to be crucial for ablating cavities of the required quality. One main reason for this can be seen in the fact that during scanning the time period between two subsequent pulses incident on the same spot is so much extended that no heat accumulation effects occur and each pulse can be treated as a first one with respect to its local impact. Extension of this advantageous technique to biocompatible materials, i.e. in this case dental restoration materials and titanium plasma-sprayed implants, is just a matter of consequence. Recently published results on composites fit well with earlier data on dental hard tissue. In case of plaque which has to be removed from implants, it turns out that removal of at least the calcified version is harder than tissue removal. Therefore, besides ultra-short lasers, also Diode and Neodymium lasers, in cw and pulsed modes, have been studied with respect to plaque removal and sterilization. The temperature increase during laser exposure has been experimentally evaluated in parallel.

  13. Measurement of extrapolation curves for the secondary pattern of beta radiation Nr. 86 calibrated in rapidity of absorbed dose for tissue equivalent by the Physikalisch Technische Bundesanstalt

    International Nuclear Information System (INIS)

    Alvarez R, J.T.

    1988-10-01

    The following report has as objective to present the obtained results of measuring - with a camera of extrapolation of variable electrodes (CE) - the dose speed absorbed in equivalent fabric given by the group of sources of the secondary pattern of radiation Beta Nr. 86, (PSB), and to compare this results with those presented by the calibration certificates that accompany the PSB extended by the primary laboratory Physikalisch Technische Bundesanstalt, (PTB), of the R.F.A. as well as the uncertainties associated to the measure process. (Author)

  14. Promoted new bone formation in maxillary distraction osteogenesis using a tissue-engineered osteogenic material.

    Science.gov (United States)

    Kinoshita, Kazuhiko; Hibi, Hideharu; Yamada, Yoichi; Ueda, Minoru

    2008-01-01

    Bilateral maxillary distraction was performed at a higher rate in rabbits to determine whether locally applied tissue-engineered osteogenic material (TEOM) enhances bone regeneration. The material was an injectable gel composed of autologous mesenchymal stem cells, which were cultured then induced to be osteogenic in character, and platelet-rich plasma (PRP). After a 5-day latency period, distraction devices were activated at a rate of 2.0 mm once daily for 4 days. Twelve rabbits were divided into 2 groups. At the end of distraction, the experimental group of rabbits received an injection of TEOM into the distracted tissue on one side, whereas, saline solution was injected into the distracted tissue on the contralateral side as the internal control. An additional control group received an injection of PRP or saline solution into the distracted tissue in the same way as the experimental group. The distraction regenerates were assessed by radiological and histomorphometric analyses. The radiodensity of the distraction gap injected with TEOM was significantly higher than that injected with PRP or saline solution at 2, 3, and 4 weeks postdistraction. The histomorphometric analysis also showed that both new bone zone and bony content in the distraction gap injected with TEOM were significantly increased when compared with PRP or saline solution. Our results demonstrated that the distraction gap injected with TEOM showed significant new bone formation. Therefore, injections of TEOM may be able to compensate for insufficient distraction gaps.

  15. Biopolymer-based hydrogels as injectable materials for tissue repair scaffolds

    International Nuclear Information System (INIS)

    Fiejdasz, Sylwia; Szczubiałka, Krzysztof; Lewandowska-Łańcucka, Joanna; Nowakowska, Maria; Osyczka, Anna M

    2013-01-01

    The progress in tissue regeneration is strongly dependent on the development of biocompatible materials with properties resembling those of a native tissue. Also, the application of noninvasive methods of delivering the scaffold into the tissue defect is of great importance. In this study we present a group of biopolymer-based materials as potential injectable scaffolds. In contrast to other studies involving collagen neutralization or additional incubation of gel in genipin solution, we propose collagen and collagen–chitosan gels crosslinked in situ with genipin. Since some parameters of the cells should be considered in the microscale, the steady-state fluorescence anisotropy was applied to study the microenvironment of the gels. To our knowledge we are the first to report on microrheological properties, such as gel time and microviscosity, for this group of hydrogels. Rapid gelation at physiological temperatures found makes these materials of special interest in applications requiring gel injectability. Physico-chemical investigation showed the influence of the crosslinking agent concentration and chitosan addition on the crosslinking degree, swelling ratio, gel microviscosity, and the degradation rate. Strong correlation was revealed between the surface wettability and the viability of cultured mesenchymal stem cells. Cytotoxicity studies indicated that the collagen–chitosan hydrogels showed the best biocompatibility. (paper)

  16. Tissue

    Directory of Open Access Journals (Sweden)

    David Morrissey

    2012-01-01

    Full Text Available Purpose. In vivo gene therapy directed at tissues of mesenchymal origin could potentially augment healing. We aimed to assess the duration and magnitude of transene expression in vivo in mice and ex vivo in human tissues. Methods. Using bioluminescence imaging, plasmid and adenoviral vector-based transgene expression in murine quadriceps in vivo was examined. Temporal control was assessed using a doxycycline-inducible system. An ex vivo model was developed and optimised using murine tissue, and applied in ex vivo human tissue. Results. In vivo plasmid-based transgene expression did not silence in murine muscle, unlike in liver. Although maximum luciferase expression was higher in muscle with adenoviral delivery compared with plasmid, expression reduced over time. The inducible promoter cassette successfully regulated gene expression with maximum levels a factor of 11 greater than baseline. Expression was re-induced to a similar level on a temporal basis. Luciferase expression was readily detected ex vivo in human muscle and tendon. Conclusions. Plasmid constructs resulted in long-term in vivo gene expression in skeletal muscle, in a controllable fashion utilising an inducible promoter in combination with oral agents. Successful plasmid gene transfection in human ex vivo mesenchymal tissue was demonstrated for the first time.

  17. Novel scalable silicone elastomer and poly(2-hydroxyethyl methacrylate) (PHEMA) composite materials for tissue engineering and drug delivery applications

    DEFF Research Database (Denmark)

    Mohanty, Soumyaranjan; Hemmingsen, Mette; Wojcik, Magdalena

    2013-01-01

    material with increased hydrophilicity in regard to virgin silicone elastomer, making it suitable as a scaffold for tissue engineering and with the concomitant possibility for delivering drug from the scaffold to the tissue. Interpenetrating polymer networks (IPNs) of silicone elastomer and PHEMA......In recent years hydrogels have received increasing attention as potential materials for applications in regenerative medicine. They can be used for scaffold materials providing structural integrity to tissue constructs, for controlled delivery of drugs and proteins to cell and tissues......, and for support materials in tissue growth. However, the real challenge is to obtain sufficiently good mechanical properties of the hydrogel. The present study shows the combination of two normally non-compatible materials, silicone elastomer and poly(2-hydroxyethyl methacrylate) (PHEMA), into a novel composite...

  18. Wear measurement of dental tissues and materials in clinical studies: A systematic review.

    Science.gov (United States)

    Wulfman, C; Koenig, V; Mainjot, A K

    2018-06-01

    This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently. An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered. After duplicates' removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results. There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

  19. Equivalent Circuit Modeling of the Dielectric Loaded Microwave Biosensor

    Directory of Open Access Journals (Sweden)

    M. T. Jilani

    2014-12-01

    Full Text Available This article describes the modeling of biological tissues at microwave frequency using equivalent lumped elements. A microwave biosensor based on microstrip ring resonator (MRR, that has been utilized previously for meat quality evaluation is used for this purpose. For the first time, the ring-resonator loaded with the lossy and high permittivity dielectric material, such as; biological tissue, in a partial overlay configuration is analyzed. The equivalent circuit modeling of the structure is then performed to identify the effect of overlay thickness on the resonance frequency. Finally, the relationship of an overlay thickness with the corresponding RC values of the meat equivalent circuit is established. Simulated, calculated and measured results are then compared for validation. Results are well agreed while the observed discrepancy is in acceptable limit.

  20. Abutment Material Effect on Peri-implant Soft Tissue Color and Perceived Esthetics.

    Science.gov (United States)

    Kim, Aram; Campbell, Stephen D; Viana, Marlos A G; Knoernschild, Kent L

    2016-12-01

    The purpose of this study was to evaluate the effect of implant abutment material on peri-implant soft tissue color using intraoral spectrophotometric analysis and to compare the clinical outcomes with patient and clinician perception and satisfaction. Thirty patients and four prosthodontic faculty members participated. Abutments were zirconia, gold-hued titanium, and titanium. Peri-implant mucosa color of a single anterior implant restoration was compared to the patient's control tooth. Spectrophotometric analysis using SpectroShade TM Micro data determined the color difference (ΔE, ΔL*, Δa*, Δb*) between the midfacial peri-implant soft tissue for each abutment material and the marginal gingiva of the control tooth. Color difference values of the abutment groups were compared using ANOVA (α = 0.05). Patient and clinician satisfaction surveys were also conducted using a color-correcting light source. The results of each patient and clinician survey question were compared using chi-square analysis (α = 0.05). Pearson correlation analyses identified the relationship between the total color difference (ΔE) and the patient/clinician perception and satisfaction, as well as between ΔE and tissue thickness. Zirconia abutments displayed significantly smaller spectrophotometric gingival color difference (ΔE) compared to titanium and gold-hued titanium abutments (respectively, 3.98 ± 0.99; 7.22 ± 3.31; 5.65 ± 2.11; p abutment materials, and no correlation between ΔE and the patient and clinician satisfaction. Patient satisfaction was significantly higher than clinician, and patient-perceived differences were lower than clinicians' (p abutments demonstrated significantly lower mean color difference compared to titanium or gold-hued titanium abutments as measured spectrophotometrically; however, no statistical difference in patient or clinician perception/satisfaction among abutment materials was demonstrated. Patients were significantly more satisfied than

  1. Development of a molecular dynamic based cohesive zone model for prediction of an equivalent material behavior for Al/Al2O3 composite

    Energy Technology Data Exchange (ETDEWEB)

    Sazgar, A. [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Movahhedy, M.R., E-mail: movahhed@sharif.edu [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Mahnama, M. [School of Mechanical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Sohrabpour, S. [Center of Excellence in Design, Robotics and Automation, Department of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2017-01-02

    The interfacial behavior of composites is often simulated using a cohesive zone model (CZM). In this approach, a traction-separation (T-S) relation between the matrix and reinforcement particles, which is often obtained from experimental results, is employed. However, since the determination of this relation from experimental results is difficult, the molecular dynamics (MD) simulation may be used as a virtual environment to obtain this relation. In this study, MD simulations under the normal and shear loadings are used to obtain the interface behavior of Al/Al2O3 composite material and to derive the T-S relation. For better agreement with Al/Al2O3 interfacial behavior, the exponential form of the T-S relation suggested by Needleman [1] is modified to account for thermal effects. The MD results are employed to develop a parameterized cohesive zone model which is implemented in a finite element model of the matrix-particle interactions. Stress-strain curves obtained from simulations under different loading conditions and volume fractions show a close correlation with experimental results. Finally, by studying the effects of strain rate and volume fraction of particles in Al(6061-T6)/Al2O3 composite, an equivalent homogeneous model is introduced which can predict the overall behavior of the composite.

  2. Time-lapse cinematography in living Drosophila tissues: preparation of material.

    Science.gov (United States)

    Davis, Ilan; Parton, Richard M

    2006-11-01

    The fruit fly, Drosophila melanogaster, has been an extraordinarily successful model organism for studying the genetic basis of development and evolution. It is arguably the best-understood complex multicellular model system, owing its success to many factors. Recent developments in imaging techniques, in particular sophisticated fluorescence microscopy methods and equipment, now allow cellular events to be studied at high resolution in living material. This ability has enabled the study of features that tend to be lost or damaged by fixation, such as transient or dynamic events. Although many of the techniques of live cell imaging in Drosophila are shared with the greater community of cell biologists working on other model systems, studying living fly tissues presents unique difficulties in keeping the cells alive, introducing fluorescent probes, and imaging through thick hazy cytoplasm. This protocol outlines the preparation of major tissue types amenable to study by time-lapse cinematography and different methods for keeping them alive.

  3. Development of reference material for proficiency tests: arsenic in fish tissue

    International Nuclear Information System (INIS)

    Santana, Luciana Vieira de; Sarkis, Jorge E.S.; Ulrich, Joao C.; Hortellani, Marcos Antonio

    2013-01-01

    Proficiency tests (PT) are extensively used to evaluate the analytical competence of laboratories, and are also used as a part of accreditation processes. For this reason are important tool for quality control of laboratories including laboratories that act directly with food exporting companies. In Brazil there are no providers of proficiency testing for toxic metals, such as arsenic in fish tissue. This study presents a protocol to produce reference material to be used in proficiency test for arsenic in fish tissue following the recommendations of the ISO Guide 35. The preparation scheme consisted of: selecting of individuals, cleaning of scale and skin, trituration, homogenization, and spiking with arsenic at two levels of concentration. The mixture was then irradiated in a cyclotron Cyclone 30 Applications ion beam with cobalt 60 at 10.00 ± 1.05 KGy, before being packed into sachets. To verify the efficacy of the irradiation procedure, 26 (randomly selected) irradiated sachets and 26 non-irradiated sachets were assessed for homogeneity and stability. The results indicate that irradiation with cobalt 60 is crucial for ensuring the preservation of the integrity of the material, providing stable material at room temperature for 2 months. The samples can therefore be transported at room temperature. (author)

  4. Development of reference material for proficiency tests: arsenic in fish tissue

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Luciana Vieira de; Sarkis, Jorge E.S.; Ulrich, Joao C.; Hortellani, Marcos Antonio, E-mail: santana-luciana@ig.com.br, E-mail: jesarkis@ipen.br, E-mail: jculrich@ipen.br, E-mail: mahortel@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    Proficiency tests (PT) are extensively used to evaluate the analytical competence of laboratories, and are also used as a part of accreditation processes. For this reason are important tool for quality control of laboratories including laboratories that act directly with food exporting companies. In Brazil there are no providers of proficiency testing for toxic metals, such as arsenic in fish tissue. This study presents a protocol to produce reference material to be used in proficiency test for arsenic in fish tissue following the recommendations of the ISO Guide 35. The preparation scheme consisted of: selecting of individuals, cleaning of scale and skin, trituration, homogenization, and spiking with arsenic at two levels of concentration. The mixture was then irradiated in a cyclotron Cyclone 30 Applications ion beam with cobalt 60 at 10.00 ± 1.05 KGy, before being packed into sachets. To verify the efficacy of the irradiation procedure, 26 (randomly selected) irradiated sachets and 26 non-irradiated sachets were assessed for homogeneity and stability. The results indicate that irradiation with cobalt 60 is crucial for ensuring the preservation of the integrity of the material, providing stable material at room temperature for 2 months. The samples can therefore be transported at room temperature. (author)

  5. David valve-sparing aortic root replacement: equivalent mid-term outcome for different valve types with or without connective tissue disorder.

    Science.gov (United States)

    Kvitting, John-Peder Escobar; Kari, Fabian A; Fischbein, Michael P; Liang, David H; Beraud, Anne-Sophie; Stephens, Elizabeth H; Mitchell, R Scott; Miller, D Craig

    2013-01-01

    Although implicitly accepted by many that the durability of valve-sparing aortic root replacement in patients with bicuspid aortic valve disease and connective tissue disorders will be inferior, this hypothesis has not been rigorously investigated. From 1993 to 2009, 233 patients (27% bicuspid aortic valve, 40% Marfan syndrome) underwent Tirone David valve-sparing aortic root replacement. Follow-up averaged 4.7 ± 3.3 years (1102 patient-years). Freedom from adverse outcomes was determined using log-rank calculations. Survival at 5 and 10 years was 98.7% ± 0.7% and 93.5% ± 5.1%, respectively. Freedom from reoperation (all causes) on the aortic root was 92.2% ± 3.6% at 10 years; 3 reoperations were aortic valve replacement owing to structural valve deterioration. Freedom from structural valve deterioration at 10 years was 96.1% ± 2.1%. No significant differences were found in survival (P = .805, P = .793, respectively), reoperation (P = .179, P = .973, respectively), structural valve deterioration (P = .639, P = .982, respectively), or any other functional or clinical endpoints when patients were stratified by valve type (tricuspid aortic valve vs bicuspid aortic valve) or associated connective tissue disorder. At the latest echocardiographic follow-up (95% complete), 202 patients (94.8%) had none or trace aortic regurgitation, 10 (4.7%) mild, 0 had moderate to severe, and 1 (0.5%) had severe aortic regurgitation. Freedom from greater than 2+ aortic regurgitation at 10 years was 95.3% ± 2.5%. Six patients sustained acute type B aortic dissection (freedom at 10 years, 90.4% ± 5.0%). Tirone David reimplantation valve-sparing aortic root replacement in carefully selected young patients was associated with excellent clinical and echocardiographic outcome in patients with either a tricuspid aortic valve or bicuspid aortic valve. No demonstrable adverse influence was found for Marfan syndrome or connective tissue disorder on durability, clinical outcome

  6. Push-out bond strength of bioceramic materials in a synthetic tissue fluid.

    Directory of Open Access Journals (Sweden)

    Noushin Shokouhinejad

    2013-12-01

    Full Text Available This study compared the push-out bond strength of EndoSequence Root Repair Material (ERRM and Bioaggregate (BA, new bioceramic materials, to that of mineral trioxide aggregate (MTA after incubation in phosphate-buffered saline (PBS, a synthetic tissue fluid, for either 1 week or 2 months.One-hundred and twenty root sections were filled with ProRoot MTA, BA, or ERRM. Each tested material was then randomly divided into two subgroups (n = 20: root sections were immersed in PBS for 1 week or 2 months. The bond strengths were measured using a universal testing machine. After that, the failure modes were examined with stereomicroscopy and scanning electron microscopy (SEM. The push-out data and failure mode categories were analyzed by two-way ANOVA and chi-square tests, respectively.The bond strength of ERRM was significantly higher than that of BA and MTA at both incubation periods. No significant difference was found between the bond strength of MTA and BA at either 1 week or 2 months. Increasing the incubation time to 2 months resulted in a significant increase in bond strength of all the materials. The failure mode was mainly mixed for MTA and BA, but cohesive for ERRM at both incubation periods.ERRM had significantly higher bond strength to root canal walls compared to MTA and BA. Increasing the incubation time significantly improved the bond strength and bioactive reaction products of all materials.

  7. Paraffin-gel tissue-mimicking material for ultrasound-guided needle biopsy phantom.

    Science.gov (United States)

    Vieira, Sílvio L; Pavan, Theo Z; Junior, Jorge E; Carneiro, Antonio A O

    2013-12-01

    Paraffin-gel waxes have been investigated as new soft tissue-mimicking materials for ultrasound-guided breast biopsy training. Breast phantoms were produced with a broad range of acoustical properties. The speed of sound for the phantoms ranged from 1425.4 ± 0.6 to 1480.3 ± 1.7 m/s at room temperature. The attenuation coefficients were easily controlled between 0.32 ± 0.27 dB/cm and 2.04 ± 0.65 dB/cm at 7.5 MHz, depending on the amount of carnauba wax added to the base material. The materials do not suffer dehydration and provide adequate needle penetration, with a Young's storage modulus varying between 14.7 ± 0.2 kPa and 34.9 ± 0.3 kPa. The phantom background material possesses long-term stability and can be employed in a supine position without changes in geometry. These results indicate that paraffin-gel waxes may be promising materials for training radiologists in ultrasound biopsy procedures. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Modelling of Cortical Bone Tissue as a Fluid Saturated Double-Porous Material - Parametric Study

    Directory of Open Access Journals (Sweden)

    Jana TURJANICOVÁ

    2013-06-01

    Full Text Available In this paper, the cortical bone tissue is considered as a poroelastic material with periodic structure represented at microscopic and mesoscopic levels. The pores of microscopic scale are connected with the pores of mesoscopic scale creating one system of connected network filled with compressible fluid. The method of asymptotic homogenization is applied to upscale the microscopic model of the fluid-solid interaction under a static loading. Obtained homogenized coefficients describe material properties of the poroelastic matrix fractured by fluid-filled pores whose geometry is described at the mesoscopic level. The second-level upscaling provides homogenized poroelastic coefficients relevant on the macroscopic scale. Furthermore, we study the dependence of these coefficients on geometrical parameters on related microscopic and macroscopic scales.

  9. Research trends in biomimetic medical materials for tissue engineering: 3D bioprinting, surface modification, nano/micro-technology and clinical aspects in tissue engineering of cartilage and bone.

    Science.gov (United States)

    Chen, Cen; Bang, Sumi; Cho, Younghak; Lee, Sahnghoon; Lee, Inseop; Zhang, ShengMin; Noh, Insup

    2016-01-01

    This review discusses about biomimetic medical materials for tissue engineering of bone and cartilage, after previous scientific commentary of the invitation-based, Korea-China joint symposium on biomimetic medical materials, which was held in Seoul, Korea, from October 22 to 26, 2015. The contents of this review were evolved from the presentations of that symposium. Four topics of biomimetic medical materials were discussed from different research groups here: 1) 3D bioprinting medical materials, 2) nano/micro-technology, 3) surface modification of biomaterials for their interactions with cells and 4) clinical aspects of biomaterials for cartilage focusing on cells, scaffolds and cytokines.

  10. Prediction of Local Ultimate Strain and Toughness of Trabecular Bone Tissue by Raman Material Composition Analysis

    Directory of Open Access Journals (Sweden)

    Roberto Carretta

    2015-01-01

    Full Text Available Clinical studies indicate that bone mineral density correlates with fracture risk at the population level but does not correlate with individual fracture risk well. Current research aims to better understand the failure mechanism of bone and to identify key determinants of bone quality, thus improving fracture risk prediction. To get a better understanding of bone strength, it is important to analyze tissue-level properties not influenced by macro- or microarchitectural factors. The aim of this pilot study was to identify whether and to what extent material properties are correlated with mechanical properties at the tissue level. The influence of macro- or microarchitectural factors was excluded by testing individual trabeculae. Previously reported data of mechanical parameters measured in single trabeculae under tension and bending and its compositional properties measured by Raman spectroscopy was evaluated. Linear and multivariate regressions show that bone matrix quality but not quantity was significantly and independently correlated with the tissue-level ultimate strain and postyield work (r=0.65–0.94. Principal component analysis extracted three independent components explaining 86% of the total variance, representing elastic, yield, and ultimate components according to the included mechanical parameters. Some matrix parameters were both included in the ultimate component, indicating that the variation in ultimate strain and postyield work could be largely explained by Raman-derived compositional parameters.

  11. Chitosan: An undisputed bio-fabrication material for tissue engineering and bio-sensing applications.

    Science.gov (United States)

    Baranwal, Anupriya; Kumar, Ashutosh; Priyadharshini, A; Oggu, Gopi Suresh; Bhatnagar, Ira; Srivastava, Ananya; Chandra, Pranjal

    2018-04-15

    Biopolymers have been serving the mankind in various ways since long. Over the last few years, these polymers have found great demand in various domains which includes bio medicine, tissue engineering, bio sensor fabrications etc. because of their excellent bio compatibility. In this context, chitosan has found global attention due to its environmentally benign nature, biocompatibility, biodegradability, and ease of availability. In last one decade or so, extensive research in active biomaterials, like chitosan has led to the development of novel delivery systems for drugs, genes, and biomolecules; and regenerative medicine. Additionally, chitosan has also witnessed its usage in functionalization of biocompatible materials, nanoparticle (NP) synthesis, and immobilization of various bio-recognition elements (BREs) to form active bio-surfaces with great ease. Keeping these aspects in mind, we have written a comprehensive review which aims to acquaint its readers with the exceptional properties of chitosan and its usage in the domain of biomedicine, tissue engineering, and biosensor fabrication. Herein, we have briefly explained various aspects of direct utilization of chitosan and then presented vivid strategies towards formulation of chitosan based nanocomposites for biomedicine, tissue engineering, and biosensing applications. Copyright © 2018 Elsevier B.V. All rights reserved.

  12. WE-F-16A-05: Use of 3D-Printers to Create a Tissue Equivalent 3D-Bolus for External Beam Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Burleson, S; Baker, J; Hsia, A; Xu, Z [Stony Brook Medicine, Stony Brook, NY (United States)

    2014-06-15

    Purpose: The purpose of this project is to demonstrate that a non-expensive 3D-printer can be used to manufacture a 3D-bolus for external beam therapy. The printed bolus then can be modeled in our treatment planning system to ensure accurate dose delivery to the patient. Methods: We developed a simple method to manufacture a patient-specific custom 3Dbolus. The bolus is designed using Eclipse Treatment Planning System, contoured onto the patients CT images. The bolus file is exported from Eclipse to 3D-printer software, and then printed using a 3D printer. Various tests were completed to determine the properties of the printing material. Percent depth dose curves in this material were measured with electron and photon beams for comparison to other materials. In order to test the validity of the 3D printed bolus for treatment planning, a custom bolus was printed and tested on the Rando phantom using film for a dose plane comparison. We compared the dose plane measured on the film to the same dose plane exported from our treatment planning system using Film QA software. The gamma-dose distribution tool was used in our film analysis. Results: We compared point measurements throughout the dose plane and were able to achieve greater than 95% passing rate at 3% dose difference and 3 mm distance to agreement, which is our departments acceptable gamma pixel parameters. Conclusion: The printed 3D bolus has proven to be accurately modeled in our treatment planning system, it is more conformal to the patient surface and more durable than other bolus currently used (wax, superflab etc.). It is also more convenient and less costly than comparable bolus from milling machine companies.

  13. WE-F-16A-05: Use of 3D-Printers to Create a Tissue Equivalent 3D-Bolus for External Beam Therapy

    International Nuclear Information System (INIS)

    Burleson, S; Baker, J; Hsia, A; Xu, Z

    2014-01-01

    Purpose: The purpose of this project is to demonstrate that a non-expensive 3D-printer can be used to manufacture a 3D-bolus for external beam therapy. The printed bolus then can be modeled in our treatment planning system to ensure accurate dose delivery to the patient. Methods: We developed a simple method to manufacture a patient-specific custom 3Dbolus. The bolus is designed using Eclipse Treatment Planning System, contoured onto the patients CT images. The bolus file is exported from Eclipse to 3D-printer software, and then printed using a 3D printer. Various tests were completed to determine the properties of the printing material. Percent depth dose curves in this material were measured with electron and photon beams for comparison to other materials. In order to test the validity of the 3D printed bolus for treatment planning, a custom bolus was printed and tested on the Rando phantom using film for a dose plane comparison. We compared the dose plane measured on the film to the same dose plane exported from our treatment planning system using Film QA software. The gamma-dose distribution tool was used in our film analysis. Results: We compared point measurements throughout the dose plane and were able to achieve greater than 95% passing rate at 3% dose difference and 3 mm distance to agreement, which is our departments acceptable gamma pixel parameters. Conclusion: The printed 3D bolus has proven to be accurately modeled in our treatment planning system, it is more conformal to the patient surface and more durable than other bolus currently used (wax, superflab etc.). It is also more convenient and less costly than comparable bolus from milling machine companies

  14. Bio-based materials with novel characteristics for tissue engineering applications - A review.

    Science.gov (United States)

    Bedian, Luis; Villalba-Rodríguez, Angel M; Hernández-Vargas, Gustavo; Parra-Saldivar, Roberto; Iqbal, Hafiz M N

    2017-05-01

    Recently, a wider spectrum of bio-based materials and materials-based novel constructs and systems has been engineered with high interests. The key objective is to help for an enhanced/better quality of life in a secure way by avoiding/limiting various adverse effects of some in practice traditional therapies. In this context, different methodological approaches including in vitro, in vivo, and ex vivo techniques have been exploited, so far. Among them, bio-based therapeutic constructs are of supreme interests for an enhanced and efficient delivery in the current biomedical sector of the modern world. The development of new types of novel, effective and highly reliable materials-based novel constructs for multipurpose applications is essential and a core demand to tackle many human health related diseases. Bio-based materials possess several complementary functionalities, e.g. unique chemical structure, bioactivity, non-toxicity, biocompatibility, biodegradability, recyclability, etc. that position them well in the modern world's materials sector. In this context, the utilization of biomaterials provides extensive opportunities for experimentation in the field of interdisciplinary and multidisciplinary scientific research. With an aim to address the global dependence on petroleum-based polymers, researchers have been redirecting their interests to the engineering of biological materials for targeted applications in different industries including cosmetics, pharmaceuticals, and other biotechnological or biomedical applications. Herein, we reviewed biotechnological advancements at large and tissue engineering from a biomaterials perspective in particular and envision directions of future developments. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Politico-economic equivalence

    DEFF Research Database (Denmark)

    Gonzalez Eiras, Martin; Niepelt, Dirk

    2015-01-01

    Traditional "economic equivalence'' results, like the Ricardian equivalence proposition, define equivalence classes over exogenous policies. We derive "politico-economic equivalence" conditions that apply in environments where policy is endogenous and chosen sequentially. A policy regime and a st......Traditional "economic equivalence'' results, like the Ricardian equivalence proposition, define equivalence classes over exogenous policies. We derive "politico-economic equivalence" conditions that apply in environments where policy is endogenous and chosen sequentially. A policy regime...... their use in the context of several applications, relating to social security reform, tax-smoothing policies and measures to correct externalities....

  16. Range-energy relations and stopping power of water, water vapour and tissue equivalent liquid for α particles over the energy range 0.5 to 8 MeV

    International Nuclear Information System (INIS)

    Palmer, R.B.J.; Akhavan-Rezayat, Ahmad

    1978-01-01

    Experimental range-energy relations are presented for alpha particles in water, water vapour and tissue equivalent liquid at energies up to 8 MeV. From these relations differential stopping powers are derived at 0.25 MeV energy intervals. Consideration is given to sources of error in the range-energy measurements and to the uncertainties that these will introduce into the stopping power values. The ratio of the differential stopping power of muscle equivalent liquid to that of water over the energy range 0.5 to 7.5 MeV is discussed in relation to the specific gravity and chemical composition of the muscle equivalent liquid. Theoretical molecular stopping power calculations based upon the Bethe formula are also presented for water. The effect of phase upon the stopping power of water is discussed. The molecular stopping power of water vapour is shown to be significantly higher than that of water for energies below 1.25 MeV and above 2.5 MeV, the ratio of the two stopping powers rising to 1.39 at 0.5 MeV and to 1.13 at 7.0 MeV. Stopping power measurements for other liquids and vapours are compared with the results for water and water vapour and some are observed to have stopping power ratios in the vapour and liquid phases which vary with energy in a similar way to water. It is suggested that there may be several factors contributing to the increased stopping power of liquids. The need for further experimental results on a wider range of liquids is stressed

  17. Nerve autografts and tissue-engineered materials for the repair of peripheral nerve injuries: a 5-year bibliometric analysis

    Directory of Open Access Journals (Sweden)

    Yuan Gao

    2015-01-01

    Full Text Available With advances in biomedical methods, tissue-engineered materials have developed rapidly as an alternative to nerve autografts for the repair of peripheral nerve injuries. However, the materials selected for use in the repair of peripheral nerve injuries, in particular multiple injuries and large-gap defects, must be chosen carefully. Various methods and materials for protecting the healthy tissue and repairing peripheral nerve injuries have been described, and each method or material has advantages and disadvantages. Recently, a large amount of research has been focused on tissue-engineered materials for the repair of peripheral nerve injuries. Using the keywords "pe-ripheral nerve injury", "autotransplant", "nerve graft", and "biomaterial", we retrieved publications using tissue-engineered materials for the repair of peripheral nerve injuries appearing in the Web of Science from 2010 to 2014. The country with the most total publications was the USA. The institutions that were the most productive in this field include Hannover Medical School (Germany, Washington University (USA, and Nantong University (China. The total number of publications using tissue-engineered materials for the repair of peripheral nerve injuries grad-ually increased over time, as did the number of Chinese publications, suggesting that China has made many scientific contributions to this field of research.

  18. Updated Lagrangian finite element formulations of various biological soft tissue non-linear material models: a comprehensive procedure and review.

    Science.gov (United States)

    Townsend, Molly T; Sarigul-Klijn, Nesrin

    2016-01-01

    Simplified material models are commonly used in computational simulation of biological soft tissue as an approximation of the complicated material response and to minimize computational resources. However, the simulation of complex loadings, such as long-duration tissue swelling, necessitates complex models that are not easy to formulate. This paper strives to offer the updated Lagrangian formulation comprehensive procedure of various non-linear material models for the application of finite element analysis of biological soft tissues including a definition of the Cauchy stress and the spatial tangential stiffness. The relationships between water content, osmotic pressure, ionic concentration and the pore pressure stress of the tissue are discussed with the merits of these models and their applications.

  19. Laser tissue welding in genitourinary reconstructive surgery: assessment of optimal suture materials.

    Science.gov (United States)

    Poppas, D P; Klioze, S D; Uzzo, R G; Schlossberg, S M

    1995-02-01

    Laser tissue welding in genitourinary reconstructive surgery has been shown in animal models to decrease operative time, improve healing, and decrease postoperative fistula formation when compared with conventional suture controls. Although the absence of suture material is the ultimate goal, this has not been shown to be practical with current technology for larger repairs. Therefore, suture-assisted laser tissue welding will likely be performed. This study sought to determine the optimal suture to be used during laser welding. The integrity of various organic and synthetic sutures exposed to laser irradiation were analyzed. Sutures studied included gut, clear Vicryl, clear polydioxanone suture (PDS), and violet PDS. Sutures were irradiated with a potassium titanyl phosphate (KTP)-532 laser or an 808-nm diode laser with and without the addition of a light-absorbing chromophore (fluorescein or indocyanine green, respectively). A remote temperature-sensing device obtained real-time surface temperatures during lasing. The average temperature, time, and total energy at break point were recorded. Overall, gut suture achieved significantly higher temperatures and withstood higher average energy delivery at break point with both the KTP-532 and the 808-nm diode lasers compared with all other groups (P welding appears to be between 60 degrees and 80 degrees C. Gut suture offers the greatest margin of error for KTP and 808-nm diode laser welding with or without the use of a chromophore.

  20. Modeling material-degradation-induced elastic property of tissue engineering scaffolds.

    Science.gov (United States)

    Bawolin, N K; Li, M G; Chen, X B; Zhang, W J

    2010-11-01

    The mechanical properties of tissue engineering scaffolds play a critical role in the success of repairing damaged tissues/organs. Determining the mechanical properties has proven to be a challenging task as these properties are not constant but depend upon time as the scaffold degrades. In this study, the modeling of the time-dependent mechanical properties of a scaffold is performed based on the concept of finite element model updating. This modeling approach contains three steps: (1) development of a finite element model for the effective mechanical properties of the scaffold, (2) parametrizing the finite element model by selecting parameters associated with the scaffold microstructure and/or material properties, which vary with scaffold degradation, and (3) identifying selected parameters as functions of time based on measurements from the tests on the scaffold mechanical properties as they degrade. To validate the developed model, scaffolds were made from the biocompatible polymer polycaprolactone (PCL) mixed with hydroxylapatite (HA) nanoparticles and their mechanical properties were examined in terms of the Young modulus. Based on the bulk degradation exhibited by the PCL/HA scaffold, the molecular weight was selected for model updating. With the identified molecular weight, the finite element model developed was effective for predicting the time-dependent mechanical properties of PCL/HA scaffolds during degradation.

  1. MRI-based morphological modeling, synthesis and characterization of cardiac tissue-mimicking materials.

    Science.gov (United States)

    Kossivas, Fotis; Angeli, S; Kafouris, D; Patrickios, C S; Tzagarakis, V; Constantinides, C

    2012-06-01

    This study uses standard synthetic methodologies to produce tissue-mimicking materials that match the morphology and emulate the in vivo murine and human cardiac mechanical and imaging characteristics, with dynamic mechanical analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM) and magnetic resonance imaging. In accordance with such aims, poly(glycerol sebacate) (PGS) elastomeric materials were synthesized (at two different glycerol (G)-sebacic (S) acid molar ratios; the first was synthesized using a G:S molar ratio of 2:2, while the second from a 2:5 G:S molar ratio, resulting in PGS2:2 and PGS2:5 elastomers, respectively). Unlike the synthesized PGS2:2 elastomers, the PGS2:5 materials were characterized by an overall mechanical instability in their loading behavior under the three successive loading conditions tested. An oscillatory response in the mechanical properties of the synthesized elastomers was observed throughout the loading cycles, with measured increased storage modulus values at the first loading cycle, stabilizing to lower values at subsequent cycles. These elastomers were characterized at 4 °C and were found to have storage modulus values of 850 and 1430 kPa at the third loading cycle, respectively, in agreement with previously reported values of the rat and human myocardium. SEM of surface topology indicated minor degradation of synthesized materials at 10 and 20 d post-immersion in the PBS buffer solution, with a noted cluster formation on the PGS2:5 elastomers. AFM nanoindentation experiments were also conducted for the measurement of the Young modulus of the sample surface (no bulk contribution). Correspondingly, the PGS2:2 elastomer indicated significantly decreased surface Young's modulus values 20 d post-PBS immersion, compared to dry conditions (Young's modulus = 1160 ± 290 kPa (dry) and 200 ± 120 kPa (20 d)). In addition to the two-dimensional (2D) elastomers, an integrative platform for accurate construction of

  2. MRI-based morphological modeling, synthesis and characterization of cardiac tissue-mimicking materials

    International Nuclear Information System (INIS)

    Kossivas, Fotis; Angeli, S; Constantinides, C; Kafouris, D; Patrickios, C S; Tzagarakis, V

    2012-01-01

    This study uses standard synthetic methodologies to produce tissue-mimicking materials that match the morphology and emulate the in vivo murine and human cardiac mechanical and imaging characteristics, with dynamic mechanical analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM) and magnetic resonance imaging. In accordance with such aims, poly(glycerol sebacate) (PGS) elastomeric materials were synthesized (at two different glycerol (G)–sebacic (S) acid molar ratios; the first was synthesized using a G:S molar ratio of 2:2, while the second from a 2:5 G:S molar ratio, resulting in PGS2:2 and PGS2:5 elastomers, respectively). Unlike the synthesized PGS2:2 elastomers, the PGS2:5 materials were characterized by an overall mechanical instability in their loading behavior under the three successive loading conditions tested. An oscillatory response in the mechanical properties of the synthesized elastomers was observed throughout the loading cycles, with measured increased storage modulus values at the first loading cycle, stabilizing to lower values at subsequent cycles. These elastomers were characterized at 4 °C and were found to have storage modulus values of 850 and 1430 kPa at the third loading cycle, respectively, in agreement with previously reported values of the rat and human myocardium. SEM of surface topology indicated minor degradation of synthesized materials at 10 and 20 d post-immersion in the PBS buffer solution, with a noted cluster formation on the PGS2:5 elastomers. AFM nanoindentation experiments were also conducted for the measurement of the Young modulus of the sample surface (no bulk contribution). Correspondingly, the PGS2:2 elastomer indicated significantly decreased surface Young's modulus values 20 d post-PBS immersion, compared to dry conditions (Young's modulus = 1160 ± 290 kPa (dry) and 200 ± 120 kPa (20 d)). In addition to the two-dimensional (2D) elastomers, an integrative platform for accurate construction of

  3. Cytoskeletal remodeling of connective tissue fibroblasts in response to static stretch is dependent on matrix material properties

    Science.gov (United States)

    Abbott, Rosalyn D; Koptiuch, Cathryn; Iatridis, James C; Howe, Alan K; Badger, Gary J; Langevin, Helene M

    2012-01-01

    In areolar “loose” connective tissue, fibroblasts remodel their cytoskeleton within minutes in response to static stretch resulting in increased cell body cross-sectional area that relaxes the tissue to a lower state of resting tension. It remains unknown whether the loosely arranged collagen matrix, characteristic of areolar connective tissue, is required for this cytoskeletal response to occur. The purpose of this study was to evaluate cytoskeletal remodeling of fibroblasts in and dissociated from areolar and dense connective tissue in response to 2 hours of static stretch in both native tissue and collagen gels of varying crosslinking. Rheometric testing indicated that the areolar connective tissue had a lower dynamic modulus and was more viscous than the dense connective tissue. In response to stretch, cells within the more compliant areolar connective tissue adopted a large “sheet-like” morphology that was in contrast to the smaller dendritic morphology in the dense connective tissue. By adjusting the in vitro collagen crosslinking, and the resulting dynamic modulus, it was demonstrated that cells dissociated from dense connective tissue are capable of responding when seeded into a compliant matrix, while cells dissociated from areolar connective tissue can lose their ability to respond when their matrix becomes stiffer. This set of experiments indicated stretch-induced fibroblast expansion was dependent on the distinct matrix material properties of areolar connective tissues as opposed to the cells’ tissue of origin. These results also suggest that disease and pathological processes with increased crosslinks, such as diabetes and fibrosis, could impair fibroblast responsiveness in connective tissues. PMID:22552950

  4. Certification of methylmercury content in two fresh-frozen reference materials: SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis)

    International Nuclear Information System (INIS)

    Davis, W.C.; Christopher, S.J.; Pugh, Rebecca S.; Donard, O.F.X.; Krupp, Eva A.; Point, David; Horvat, Milena; Gibicar, D.; Kljakovic-Gaspic, Z.; Porter, Barbara J.; Schantz, Michele M.

    2007-01-01

    This paper describes the development of two independent analytical methods for the extraction and quantification of methylmercury from marine biota. The procedures involve microwave extraction, followed by derivatization and either headspace solid-phase microextraction (SPME) with a polydimethylsiloxane (PDMS)-coated silica fiber or back-extraction into iso-octane. The identification and quantification of the extracted compounds is carried out by capillary gas chromatography/mass spectrometric (GC/MS) and inductively coupled plasma mass spectrometric (GC/ICP-MS) detection. Both methods were validated for the determination of methylmercury (MeHg) concentrations in a variety of biological standard reference materials (SRMs) including fresh-frozen tissue homogenates of SRM 1946 Lake Superior fish tissue and SRM 1974a organics in mussel tissue (Mytilus edulis) and then applied to the certification effort of SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis). While past certifications of methylmercury in tissue SRMs have been based on two independent methods from the National Institute of Standards and Technology (NIST) and participating laboratories, the methods described within provide improved protocols and will allow future certification efforts to be based on at least two independent analytical methods within NIST. (orig.)

  5. Certification of methylmercury content in two fresh-frozen reference materials: SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis)

    Energy Technology Data Exchange (ETDEWEB)

    Davis, W.C.; Christopher, S.J.; Pugh, Rebecca S. [National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Analytical Chemistry Division, Charleston, SC (United States); Donard, O.F.X.; Krupp, Eva A. [LCABIE/CNRS Helioparc Pau-Pyrenees, Pau (France); Point, David [National Institute of Standards and Technology (NIST), Hollings Marine Laboratory, Analytical Chemistry Division, Charleston, SC (United States); LCABIE/CNRS Helioparc Pau-Pyrenees, Pau (France); Horvat, Milena; Gibicar, D. [Jozef Stefan Institute, Ljubljana (Slovenia); Kljakovic-Gaspic, Z. [Jozef Stefan Institute, Ljubljana (Slovenia); Institute for Medical Research and Occupational Health, Zagreb (Croatia); Porter, Barbara J.; Schantz, Michele M. [National Institute of Standards and Technology (NIST), Analytical Chemistry Division, Gaithersburg, MD (United States)

    2007-04-15

    This paper describes the development of two independent analytical methods for the extraction and quantification of methylmercury from marine biota. The procedures involve microwave extraction, followed by derivatization and either headspace solid-phase microextraction (SPME) with a polydimethylsiloxane (PDMS)-coated silica fiber or back-extraction into iso-octane. The identification and quantification of the extracted compounds is carried out by capillary gas chromatography/mass spectrometric (GC/MS) and inductively coupled plasma mass spectrometric (GC/ICP-MS) detection. Both methods were validated for the determination of methylmercury (MeHg) concentrations in a variety of biological standard reference materials (SRMs) including fresh-frozen tissue homogenates of SRM 1946 Lake Superior fish tissue and SRM 1974a organics in mussel tissue (Mytilus edulis) and then applied to the certification effort of SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis). While past certifications of methylmercury in tissue SRMs have been based on two independent methods from the National Institute of Standards and Technology (NIST) and participating laboratories, the methods described within provide improved protocols and will allow future certification efforts to be based on at least two independent analytical methods within NIST. (orig.)

  6. Proteomic patterns analysis with multivariate calculations as a promising tool for prompt differentiation of early stage lung tissue with cancer and unchanged tissue material

    Directory of Open Access Journals (Sweden)

    Grodzki Tomasz

    2011-03-01

    Full Text Available Abstract Background Lung cancer diagnosis in tissue material with commonly used histological techniques is sometimes inconvenient and in a number of cases leads to ambiguous conclusions. Frequently advanced immunostaining techniques have to be employed, yet they are both time consuming and limited. In this study a proteomic approach is presented which may help provide unambiguous pathologic diagnosis of tissue material. Methods Lung tissue material found to be pathologically changed was prepared to isolate proteome with fast and non selective procedure. Isolated peptides and proteins in ranging from 3.5 to 20 kDa were analysed directly using high resolution mass spectrometer (MALDI-TOF/TOF with sinapic acid as a matrix. Recorded complex spectra of a single run were then analyzed with multivariate statistical analysis algorithms (principle component analysis, classification methods. In the applied protocol we focused on obtaining the spectra richest in protein signals constituting a pattern of change within the sample containing detailed information about its protein composition. Advanced statistical methods were to indicate differences between examined groups. Results Obtained results indicate changes in proteome profiles of changed tissues in comparison to physiologically unchanged material (control group which were reflected in the result of principle component analysis (PCA. Points representing spectra of control group were located in different areas of multidimensional space and were less diffused in comparison to cancer tissues. Three different classification algorithms showed recognition capability of 100% regarding classification of examined material into an appropriate group. Conclusion The application of the presented protocol and method enabled finding pathological changes in tissue material regardless of localization and size of abnormalities in the sample volume. Proteomic profile as a complex, rich in signals spectrum of proteins

  7. Tunable geometry of bacterial inclusion bodies as substrate materials for tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    GarcIa-Fruitos, Elena; Seras-Franzoso, JoaquIn; Vazquez, Esther; Villaverde, Antonio [CIBER en BioingenierIa, Biomateriales y Nanomedicina, Bellaterra, 08193 Barcelona (Spain); Institut de Biotecnologia i de Biomedicina and Departament de Genetica i de Microbiologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Cerdanyola del Valles), Barcelona (Spain)

    2010-05-21

    A spectrum of materials for biomedical applications is produced in bacteria, and some of them, such as metals or polyhydroxyalkanoates, are straightforwardly obtained as particulate entities. We have explored the biofabrication process of bacterial inclusion bodies, particulate proteinaceous materials (ranging from 50 to 500 nm in diameter) recently recognized as suitable for surface topographical modification and tissue engineering. Inclusion bodies have been widely described as spherical or pseudo-spherical particles with only minor morphological variability, mostly restricted to their size. Here we have identified a cellular gene in Escherichia coli (clpP) that controls the in vivo fabrication process of inclusion bodies. In the absence of the encoded protease, the dynamics of protein deposition is perturbed, resulting in unusual tear-shaped particles with enhanced surface-volume ratios. This fact modifies the ability of inclusion bodies to promote mammalian cell attachment and differentiation upon surface decoration. The implications of the genetic control of inclusion body geometry are discussed in the context of their biological fabrication and regarding the biomedical potential of these protein clusters in regenerative medicine.

  8. Tunable geometry of bacterial inclusion bodies as substrate materials for tissue engineering

    International Nuclear Information System (INIS)

    GarcIa-Fruitos, Elena; Seras-Franzoso, JoaquIn; Vazquez, Esther; Villaverde, Antonio

    2010-01-01

    A spectrum of materials for biomedical applications is produced in bacteria, and some of them, such as metals or polyhydroxyalkanoates, are straightforwardly obtained as particulate entities. We have explored the biofabrication process of bacterial inclusion bodies, particulate proteinaceous materials (ranging from 50 to 500 nm in diameter) recently recognized as suitable for surface topographical modification and tissue engineering. Inclusion bodies have been widely described as spherical or pseudo-spherical particles with only minor morphological variability, mostly restricted to their size. Here we have identified a cellular gene in Escherichia coli (clpP) that controls the in vivo fabrication process of inclusion bodies. In the absence of the encoded protease, the dynamics of protein deposition is perturbed, resulting in unusual tear-shaped particles with enhanced surface-volume ratios. This fact modifies the ability of inclusion bodies to promote mammalian cell attachment and differentiation upon surface decoration. The implications of the genetic control of inclusion body geometry are discussed in the context of their biological fabrication and regarding the biomedical potential of these protein clusters in regenerative medicine.

  9. Decellularized cartilage may be a chondroinductive material for osteochondral tissue engineering.

    Directory of Open Access Journals (Sweden)

    Amanda J Sutherland

    Full Text Available Extracellular matrix (ECM-based materials are attractive for regenerative medicine in their ability to potentially aid in stem cell recruitment, infiltration, and differentiation without added biological factors. In musculoskeletal tissue engineering, demineralized bone matrix is widely used, but recently cartilage matrix has been attracting attention as a potentially chondroinductive material. The aim of this study was thus to establish a chemical decellularization method for use with articular cartilage to quantify removal of cells and analyze the cartilage biochemical content at various stages during the decellularization process, which included a physically devitalization step. To study the cellular response to the cartilage matrix, rat bone marrow-derived mesenchymal stem cells (rBMSCs were cultured in cell pellets containing cells only (control, chondrogenic differentiation medium (TGF-β, chemically decellularized cartilage particles (DCC, or physically devitalized cartilage particles (DVC. The chemical decellularization process removed the vast majority of DNA and about half of the glycosaminoglycans (GAG within the matrix, but had no significant effect on the amount of hydroxyproline. Most notably, the DCC group significantly outperformed TGF-β in chondroinduction of rBMSCs, with collagen II gene expression an order of magnitude or more higher. While DVC did not exhibit a chondrogenic response to the extent that DCC did, DVC had a greater down regulation of collagen I, collagen X and Runx2. A new protocol has been introduced for cartilage devitalization and decellularization in the current study, with evidence of chondroinductivity. Such bioactivity along with providing the 'raw material' building blocks of regenerating cartilage may suggest a promising role for DCC in biomaterials that rely on recruiting endogenous cell recruitment and differentiation for cartilage regeneration.

  10. Histological evaluation of tissue reactions to newly synthetized calcium silicate- and hydroxyapatite-based bioactive materials: in vivo study

    Directory of Open Access Journals (Sweden)

    Opačić-Galić Vanja

    2017-01-01

    Full Text Available Introduction/Objective. Development of materials which could be used as biological bone substitutes is one of the most valuable and active fields of biomaterial research. The goal of the study was to research the reaction of tissue on calcium silicate- (CS and hydroxyapatitebased (CS-HA newly synthesized nanomaterials, after being implanted into the subcutaneous tissue of a rats and direct pulp capping of rabbit teeth. Methods. The tested materials were implanted in 40 Wistar male rats, sacrificed after seven, 15, 30, and 60 days. The direct pulp capping was performed on the teeth of rabbits. Cavities were prepared on the vestibular surface of the incisors. The animals were sacrificed after 10 and 15 days. The control material was mineral trioxide aggregate (MTA. Histological analysis covered the tracking of inflammatory reaction cellular components, presence of gigantic cells, and necrosis of the tissue. Results. Seven days after the implantation, the strongest inflammatory response was given by the MTA (3.3 Ѓ} 0.48, while CS and CS-HA scored 3 ± 0.71. After 60 days, the rate of inflammatory reactions dropped, which was the least visible with CS-HA (0.2 ± 0.45. The least visible inflammatory reaction of the rabbits’ pulp tissue was spotted with the CS (1.83 ± 0.75, than with the MTA and CS-HA (2.67 ± 1.53, 3 ± 0.63. Conclusion. The newly synthesized materials caused a slight reaction of the subcutaneous tissue. CS-HA showed the best tissue tolerance. Nanostructural biomaterials caused a slight to moderate inflammatory reaction of the rabbits’ pulp tissue only in the immediate vicinity of the implanted material.

  11. Design, Materials, and Mechanobiology of Biodegradable Scaffolds for Bone Tissue Engineering

    Science.gov (United States)

    Velasco, Marco A.; Narváez-Tovar, Carlos A.; Garzón-Alvarado, Diego A.

    2015-01-01

    A review about design, manufacture, and mechanobiology of biodegradable scaffolds for bone tissue engineering is given. First, fundamental aspects about bone tissue engineering and considerations related to scaffold design are established. Second, issues related to scaffold biomaterials and manufacturing processes are discussed. Finally, mechanobiology of bone tissue and computational models developed for simulating how bone healing occurs inside a scaffold are described. PMID:25883972

  12. Equivalence principles and electromagnetism

    Science.gov (United States)

    Ni, W.-T.

    1977-01-01

    The implications of the weak equivalence principles are investigated in detail for electromagnetic systems in a general framework. In particular, it is shown that the universality of free-fall trajectories (Galileo weak equivalence principle) does not imply the validity of the Einstein equivalence principle. However, the Galileo principle plus the universality of free-fall rotation states does imply the Einstein principle.

  13. Evaluation of temperature rise in a tissue mimicking material during HIFU exposure

    International Nuclear Information System (INIS)

    Maruvada, S; Liu, Y; Herman, B A; Harris, G R

    2011-01-01

    In pre-clinical testing it is essential to characterize clinical high intensity focused ultrasound (HIFU) devices using tissue-mimicking materials (TMMs) with well known characteristics, including temperature rise and cavitation properties. The purpose of this study was to monitor cavitation behavior and correlate its effect with temperature rise in a HIFU TMM containing an embedded thermocouple. A 75-μm fine wire thermocouple was embedded in a hydrogel-based TMM previously developed for HIFU. HIFU at 1.1 and 3.3 MHz was focused at the thermocouple junction. Focal pressures from 1-11 MPa were applied and the temperature profiles were recorded. Three hydrophones were used to monitor cavitation activity during sonication. A hydrophone confocal with the HIFU transducer and a cylindrical hydrophone lateral to the HIFU beam were used as passive cavitation detectors for spectral analysis of signals, and a needle hydrophone placed beyond the HIFU focus was used to record changes in the pressure amplitude due to blockage by bubbles at or near the focus. B-mode imaging scans were employed to visualize bubble presence during sonication. In a separate measurement, schlieren imaging was used to monitor the change in field distribution behind the TMM. All hydrophone methods correlated well with cavitation in the TMM.

  14. Evaluation of temperature rise in a tissue mimicking material during HIFU exposure

    Energy Technology Data Exchange (ETDEWEB)

    Maruvada, S; Liu, Y; Herman, B A; Harris, G R, E-mail: subha.maruvada@fda.hhs.gov [Food and Drug Administration, Center for Devices and Radiological Health, 10903 New Hampshire Ave., Bldg., Silver Spring, MD 20993 (United States)

    2011-02-01

    In pre-clinical testing it is essential to characterize clinical high intensity focused ultrasound (HIFU) devices using tissue-mimicking materials (TMMs) with well known characteristics, including temperature rise and cavitation properties. The purpose of this study was to monitor cavitation behavior and correlate its effect with temperature rise in a HIFU TMM containing an embedded thermocouple. A 75-{mu}m fine wire thermocouple was embedded in a hydrogel-based TMM previously developed for HIFU. HIFU at 1.1 and 3.3 MHz was focused at the thermocouple junction. Focal pressures from 1-11 MPa were applied and the temperature profiles were recorded. Three hydrophones were used to monitor cavitation activity during sonication. A hydrophone confocal with the HIFU transducer and a cylindrical hydrophone lateral to the HIFU beam were used as passive cavitation detectors for spectral analysis of signals, and a needle hydrophone placed beyond the HIFU focus was used to record changes in the pressure amplitude due to blockage by bubbles at or near the focus. B-mode imaging scans were employed to visualize bubble presence during sonication. In a separate measurement, schlieren imaging was used to monitor the change in field distribution behind the TMM. All hydrophone methods correlated well with cavitation in the TMM.

  15. Intercalated chitosan/hydroxyapatite nanocomposites: Promising materials for bone tissue engineering applications.

    Science.gov (United States)

    Nazeer, Muhammad Anwaar; Yilgör, Emel; Yilgör, Iskender

    2017-11-01

    Preparation and characterization of chitosan/hydroxyapatite (CS/HA) nanocomposites displaying an intercalated structure is reported. Hydroxyapatite was synthesized through sol-gel process. Formic acid was introduced as a new solvent to obtain stable dispersions of nano-sized HA particles in polymer solution. CS/HA dispersions with HA contents of 5, 10 and 20% by weight were prepared. Self-assembling of HA nanoparticles during the drying of the solvent cast films led to the formation of homogeneous CS/HA nanocomposites. Composite films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-rays (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-rays diffraction (XRD) analysis and thermogravimetric analysis (TGA). SEM and AFM confirmed the presence of uniformly distributed HA nanoparticles on the chitosan matrix surface. XRD patterns and cross-sectional SEM images showed the formation of layered nanocomposites. Complete degradation of chitosan matrix in TGA experiments, led to the formation of nanoporous 3D scaffolds containing hydroxyapatite, β-tricalcium phosphate and calcium pyrophosphate. CS/HA composites can be considered as promising materials for bone tissue engineering applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Development of Synthetic and Natural Materials for Tissue Engineering Applications Using Adipose Stem Cells

    Directory of Open Access Journals (Sweden)

    Yunfan He

    2016-01-01

    Full Text Available Adipose stem cells have prominent implications in tissue regeneration due to their abundance and relative ease of harvest from adipose tissue and their abilities to differentiate into mature cells of various tissue lineages and secrete various growth cytokines. Development of tissue engineering techniques in combination with various carrier scaffolds and adipose stem cells offers great potential in overcoming the existing limitations constraining classical approaches used in plastic and reconstructive surgery. However, as most tissue engineering techniques are new and highly experimental, there are still many practical challenges that must be overcome before laboratory research can lead to large-scale clinical applications. Tissue engineering is currently a growing field of medical research; in this review, we will discuss the progress in research on biomaterials and scaffolds for tissue engineering applications using adipose stem cells.

  17. Attainment of radiation equivalency principle

    International Nuclear Information System (INIS)

    Shmelev, A.N.; Apseh, V.A.

    2004-01-01

    Problems connected with the prospects for long-term development of the nuclear energetics are discussed. Basic principles of the future large-scale nuclear energetics are listed, primary attention is the safety of radioactive waste management of nuclear energetics. The radiation equivalence principle means close of fuel cycle and management of nuclear materials transportation with low losses on spent fuel and waste processing. Two aspects are considered: radiation equivalence in global and local aspects. The necessity of looking for other strategies of fuel cycle management in full-scale nuclear energy on radioactive waste management is supported [ru

  18. Waste Determination Equivalency - 12172

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, Rebecca D. [Savannah River Remediation (United States)

    2012-07-01

    The Savannah River Site (SRS) is a Department of Energy (DOE) facility encompassing approximately 800 square kilometers near Aiken, South Carolina which began operations in the 1950's with the mission to produce nuclear materials. The SRS contains fifty-one tanks (2 stabilized, 49 yet to be closed) distributed between two liquid radioactive waste storage facilities at SRS containing carbon steel underground tanks with storage capacities ranging from 2,800,000 to 4,900,000 liters. Treatment of the liquid waste from these tanks is essential both to closing older tanks and to maintaining space needed to treat the waste that is eventually vitrified or disposed of onsite. Section 3116 of the Ronald W. Reagan National Defense Authorization Act of Fiscal Year 2005 (NDAA) provides the Secretary of Energy, in consultation with the Nuclear Regulatory Commission (NRC), a methodology to determine that certain waste resulting from prior reprocessing of spent nuclear fuel are not high-level radioactive waste if it can be demonstrated that the waste meets the criteria set forth in Section 3116(a) of the NDAA. The Secretary of Energy, in consultation with the NRC, signed a determination in January 2006, pursuant to Section 3116(a) of the NDAA, for salt waste disposal at the SRS Saltstone Disposal Facility. This determination is based, in part, on the Basis for Section 3116 Determination for Salt Waste Disposal at the Savannah River Site and supporting references, a document that describes the planned methods of liquid waste treatment and the resulting waste streams. The document provides descriptions of the proposed methods for processing salt waste, dividing them into 'Interim Salt Processing' and later processing through the Salt Waste Processing Facility (SWPF). Interim Salt Processing is separated into Deliquification, Dissolution, and Adjustment (DDA) and Actinide Removal Process/Caustic Side Solvent Extraction Unit (ARP/MCU). The Waste Determination was signed

  19. Polyvinyl chloride as a multimodal tissue-mimicking material with tuned mechanical and medical imaging properties.

    Science.gov (United States)

    Li, Weisi; Belmont, Barry; Greve, Joan M; Manders, Adam B; Downey, Brian C; Zhang, Xi; Xu, Zhen; Guo, Dongming; Shih, Albert

    2016-10-01

    The mechanical and imaging properties of polyvinyl chloride (PVC) can be adjusted to meet the needs of researchers as a tissue-mimicking material. For instance, the hardness can be adjusted by changing the ratio of softener to PVC polymer, mineral oil can be added for lubrication in needle insertion, and glass beads can be added to scatter acoustic energy similar to biological tissue. Through this research, the authors sought to develop a regression model to design formulations of PVC with targeted mechanical and multimodal medical imaging properties. The design of experiment was conducted by varying three factors-(1) the ratio of softener to PVC polymer, (2) the mass fraction of mineral oil, and (3) the mass fraction of glass beads-and measuring the mechanical properties (elastic modulus, hardness, viscoelastic relaxation time constant, and needle insertion friction force) and the medical imaging properties [speed of sound, acoustic attenuation coefficient, magnetic resonance imaging time constants T 1 and T 2 , and the transmittance of the visible light at wavelengths of 695 nm (T λ695 ) and 532 nm (T λ532 )] on twelve soft PVC samples. A regression model was built to describe the relationship between the mechanical and medical imaging properties and the values of the three composition factors of PVC. The model was validated by testing the properties of a PVC sample with a formulation distinct from the twelve samples. The tested soft PVC had elastic moduli from 6 to 45 kPa, hardnesses from 5 to 50 Shore OOO-S, viscoelastic stress relaxation time constants from 114.1 to 191.9 s, friction forces of 18 gauge needle insertion from 0.005 to 0.086 N/mm, speeds of sound from 1393 to 1407 m/s, acoustic attenuation coefficients from 0.38 to 0.61 (dB/cm)/MHz, T 1 relaxation times from 426.3 to 450.2 ms, T 2 relaxation times from 21.5 to 28.4 ms, T λ695 from 46.8% to 92.6%, and T λ532 from 41.1% to 86.3%. Statistically significant factors of each property were

  20. The Effect of Arch Height and Material Hardness of Personalized Insole on Correction and Tissues of Flatfoot

    Directory of Open Access Journals (Sweden)

    Shonglun Su

    2017-01-01

    Full Text Available Flat foot is one of the common deformities in the youth population, seriously affecting the weight supporting and daily exercising. However, there is lacking of quantitative data relative to material selection and shape design of the personalized orthopedic insole. This study was to evaluate the biomechanical effects of material hardness and support height of personalized orthopedic insole on foot tissues, by in vivo experiment and finite element modeling. The correction of arch height increased with material hardness and support height. The peak plantar pressure increased with the material hardness, and these values by wearing insoles of 40° were apparently higher than the bare feet condition. Harder insole material results in higher stress in the joint and ligament stress than softer material. In the calcaneocuboid joint, the stress increased with the arch height of insoles. The material hardness did not apparently affect the stress in the ankle joints, but the support heights of insole did. In general, insole material and support design are positively affecting the correction of orthopedic insole, but negatively resulting in unreasonable stress on the stress in the joint and ligaments. There should be an integration of improving correction and reducing stress in foot tissues.

  1. Calcium Phosphate as a Key Material for Socially Responsible Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Vuk Uskoković

    2016-06-01

    Full Text Available Socially responsible technologies are designed while taking into consideration the socioeconomic, geopolitical and environmental limitations of regions in which they will be implemented. In the medical context, this involves making therapeutic platforms more accessible and affordable to patients in poor regions of the world wherein a given disease is endemic. This often necessitates going against the reigning trend of making therapeutic nanoparticles ever more structurally complex and expensive. However, studies aimed at simplifying materials and formulations while maintaining the functionality and therapeutic response of their more complex counterparts seldom provoke a significant interest in the scientific community. In this review we demonstrate that such compositional simplifications are meaningful when it comes to the design of a solution for osteomyelitis, a disease that is in its natural, non-postoperative form particularly prevalent in the underdeveloped parts of the world wherein poverty, poor sanitary conditions, and chronically compromised defense lines of the immune system are the norm. We show that calcium phosphate nanoparticles, which are inexpensive to make, could be chemically designed to possess the same functionality as a hypothetic mixture additionally composed of: (a a bone growth factor; (b an antibiotic for prophylactic or anti-infective purposes; (c a bisphosphonate as an antiresorptive compound; (d a viral vector to enable the intracellular delivery of therapeutics; (e a luminescent dye; (f a radiographic component; (g an imaging contrast agent; (h a magnetic domain; and (i polymers as viscous components enabling the injectability of the material and acting as carriers for the sustained release of a drug. In particular, calcium phosphates could: (a produce tunable drug release profiles; (b take the form of viscous and injectable, self-setting pastes; (c be naturally osteo-inductive and inhibitory for osteoclastogenesis

  2. ROMP-Derived cyclooctene-based monolithic polymeric materials reinforced with inorganic nanoparticles for applications in tissue engineering

    Directory of Open Access Journals (Sweden)

    Franziska Weichelt

    2010-12-01

    Full Text Available Porous monolithic inorganic/polymeric hybrid materials have been prepared via ring-opening metathesis copolymerization starting from a highly polar monomer, i.e., cis-5-cyclooctene-trans-1,2-diol and a 7-oxanorborn-2-ene-derived cross-linker in the presence of porogenic solvents and two types of inorganic nanoparticles (i.e., CaCO3 and calcium hydroxyapatite, respectively using the third-generation Grubbs initiator RuCl2(Py2(IMesH2(CHPh. The physico-chemical properties of the monolithic materials, such as pore size distribution and microhardness were studied with regard to the nanoparticle type and content. Moreover, the reinforced monoliths were tested for the possible use as scaffold materials in tissue engineering, by carrying out cell cultivation experiments with human adipose tissue-derived stromal cells.

  3. Preparation of a Carbon Doped Tissue-Mimicking Material with High Dielectric Properties for Microwave Imaging Application

    Directory of Open Access Journals (Sweden)

    Siang-Wen Lan

    2016-07-01

    Full Text Available In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were 2 wt %, 4 wt %, and 6 wt %. The effect of doping material and amount on the microwave dielectric properties including dielectric constant and conductivity were investigated over an ultra-wide frequency range from 2 GHz to 20 GHz. The coaxial open-ended reflection technology was used to evaluate the microwave dielectric properties. Six measured values in different locations of each sample were averaged and the standard deviations of all the measured dielectric properties, including dielectric constant and conductivity, were less than one, indicating a good uniformity of the prepared samples. Without doping, the dielectric constant was equal to 23 ± 2 approximately. Results showed with doping of carbon based materials that the dielectric constant and conductivity both increased about 5% to 20%, and the increment was dependent on the doping amount. By proper selection of doping amount of the carbon based materials, the prepared material could map the required dielectric properties of special tissues. The proposed materials were suitable for the phantom used in the microwave medical imaging system.

  4. Equivalent drawbead performance in deep drawing simulations

    NARCIS (Netherlands)

    Meinders, Vincent T.; Geijselaers, Hubertus J.M.; Huetink, Han

    1999-01-01

    Drawbeads are applied in the deep drawing process to improve the control of the material flow during the forming operation. In simulations of the deep drawing process these drawbeads can be replaced by an equivalent drawbead model. In this paper the usage of an equivalent drawbead model in the

  5. Effective dose equivalent

    International Nuclear Information System (INIS)

    Huyskens, C.J.; Passchier, W.F.

    1988-01-01

    The effective dose equivalent is a quantity which is used in the daily practice of radiation protection as well as in the radiation hygienic rules as measure for the health risks. In this contribution it is worked out upon which assumptions this quantity is based and in which cases the effective dose equivalent can be used more or less well. (H.W.)

  6. Characterization of revenue equivalence

    NARCIS (Netherlands)

    Heydenreich, B.; Müller, R.; Uetz, Marc Jochen; Vohra, R.

    2009-01-01

    The property of an allocation rule to be implementable in dominant strategies by a unique payment scheme is called revenue equivalence. We give a characterization of revenue equivalence based on a graph theoretic interpretation of the incentive compatibility constraints. The characterization holds

  7. Characterization of Revenue Equivalence

    NARCIS (Netherlands)

    Heydenreich, Birgit; Müller, Rudolf; Uetz, Marc Jochen; Vohra, Rakesh

    2008-01-01

    The property of an allocation rule to be implementable in dominant strategies by a unique payment scheme is called \\emph{revenue equivalence}. In this paper we give a characterization of revenue equivalence based on a graph theoretic interpretation of the incentive compatibility constraints. The

  8. On the operator equivalents

    International Nuclear Information System (INIS)

    Grenet, G.; Kibler, M.

    1978-06-01

    A closed polynomial formula for the qth component of the diagonal operator equivalent of order k is derived in terms of angular momentum operators. The interest in various fields of molecular and solid state physics of using such a formula in connection with symmetry adapted operator equivalents is outlined

  9. Recovery of material parameters of soft hyperelastic tissue by an inverse spectral technique

    KAUST Repository

    Gou, Kun; Joshi, Sunnie; Walton, Jay R.

    2012-01-01

    An inverse spectral method is developed for recovering a spatially inhomogeneous shear modulus for soft tissue. The study is motivated by a novel use of the intravascular ultrasound technique to image arteries. The arterial wall is idealized as a

  10. The properties of connective tissue membrane and pig skin as raw materials for cooked sausage.

    Science.gov (United States)

    Puolanne, E; Ruusunen, M

    1981-09-01

    Pig skin and epimysial membrane from young bulls were comminuted in a colloid grinder and mixed with water and additives. The resultant mixture was heated in a water bath to give an internal temperature of 72°C, and centrifuged while still hot. Such variations in the amount of water added, the salt content, the phosphate content and the pH value as are possible in cooked sausage heated to over 65°C during processing did not cause marked changes in the amount of water bound by the connective tissues, the amount of dissolved protein or the gel strength of the liquid released from the connective tissues. As the temperature rose the amount of bound water dropped, but the amount of dissolved protein and the gel strength increased. The liquid released from the connective tissue membranes formed a gel at 32°C and re-melted at 49°C. For pig skin, the corresponding temperatures were 23°C and 47°C. On the basis of this study it appears that connective tissue may be important for the water-binding capacity and firmness of cold sausage. The connective tissue membranes obtained from young bulls and pig skin are of roughly equal value in this respect, although the gel formed from connective tissue membrane is tougher. Copyright © 1981. Published by Elsevier Ltd.

  11. Synthesis and characterization of cycloaliphatic hydrophilic polyurethanes, modified with L-ascorbic acid, as materials for soft tissue regeneration

    International Nuclear Information System (INIS)

    Kucinska-Lipka, J.; Gubanska, I.; Strankowski, M.; Cieśliński, H.; Filipowicz, N.; Janik, H.

    2017-01-01

    In this paper we described synthesis and characteristic of obtained hydrophilic polyurethanes (PURs) modified with ascorbic acid (commonly known as vitamin C). Such materials may find an application in the biomedical field, for example in the regenerative medicine of soft tissues, according to ascorbic acid wide influence on tissue regeneration Flora (2009), Szymańska-Pasternak et al. (2011), Taikarimi and Ibrahim (2011), Myrvik and Volk (1954), Li et al. (2001), Cursino et al. (2005) . Hydrophilic PURs were obtained with the use of amorphous α,ω-dihydroxy(ethylene-butylene adipate) (dHEBA) polyol, 1,4-butanediol (BDO) chain extender and aliphatic 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI). HMDI was chosen as a nontoxic diisocyanate, suitable for biomedical PUR synthesis. Modification with L-ascorbic acid (AA) was performed to improve obtained PUR materials biocompatibility. Chemical structure of obtained PURs was provided and confirmed by Fourier transform infrared spectroscopy (FTIR) and Proton nuclear magnetic resonance spectroscopy ( 1 HNMR). Differential scanning calorimetry (DSC) was used to indicate the influence of ascorbic acid modification on such parameters as glass transition temperature, melting temperature and melting enthalpies of obtained materials. To determine how these materials may potentially behave, after implementation in tissue, degradation behavior of obtained PURs in various chemical environments, which were represented by canola oil, saline solution, distilled water and phosphate buffered saline (PBS) was estimated. The influence of AA on hydrophilic-hydrophobic character of obtained PURs was established by contact angle study. This experiment revealed that ascorbic acid significantly improves hydrophilicity of obtained PUR materials and the same cause that they are more suitable candidates for biomedical applications. Good hemocompatibility characteristic of studied PUR materials was confirmed by the hemocompatibility test with

  12. Synthesis and characterization of cycloaliphatic hydrophilic polyurethanes, modified with L-ascorbic acid, as materials for soft tissue regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Kucinska-Lipka, J., E-mail: juskucin@pg.gda.pl [Gdank University of Technology, Faculty of Chemistry, Department of Polymer Technology, Narutowicza St. 11/12, 80-233 Gdansk (Poland); Gubanska, I.; Strankowski, M. [Gdank University of Technology, Faculty of Chemistry, Department of Polymer Technology, Narutowicza St. 11/12, 80-233 Gdansk (Poland); Cieśliński, H.; Filipowicz, N. [Gdansk University of Technology, Faculty of Chemistry, Department of Microbiology, Narutowicza St. 11/12, 80-233 Gdansk (Poland); Janik, H. [Gdank University of Technology, Faculty of Chemistry, Department of Polymer Technology, Narutowicza St. 11/12, 80-233 Gdansk (Poland)

    2017-06-01

    In this paper we described synthesis and characteristic of obtained hydrophilic polyurethanes (PURs) modified with ascorbic acid (commonly known as vitamin C). Such materials may find an application in the biomedical field, for example in the regenerative medicine of soft tissues, according to ascorbic acid wide influence on tissue regeneration Flora (2009), Szymańska-Pasternak et al. (2011), Taikarimi and Ibrahim (2011), Myrvik and Volk (1954), Li et al. (2001), Cursino et al. (2005) . Hydrophilic PURs were obtained with the use of amorphous α,ω-dihydroxy(ethylene-butylene adipate) (dHEBA) polyol, 1,4-butanediol (BDO) chain extender and aliphatic 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI). HMDI was chosen as a nontoxic diisocyanate, suitable for biomedical PUR synthesis. Modification with L-ascorbic acid (AA) was performed to improve obtained PUR materials biocompatibility. Chemical structure of obtained PURs was provided and confirmed by Fourier transform infrared spectroscopy (FTIR) and Proton nuclear magnetic resonance spectroscopy ({sup 1}HNMR). Differential scanning calorimetry (DSC) was used to indicate the influence of ascorbic acid modification on such parameters as glass transition temperature, melting temperature and melting enthalpies of obtained materials. To determine how these materials may potentially behave, after implementation in tissue, degradation behavior of obtained PURs in various chemical environments, which were represented by canola oil, saline solution, distilled water and phosphate buffered saline (PBS) was estimated. The influence of AA on hydrophilic-hydrophobic character of obtained PURs was established by contact angle study. This experiment revealed that ascorbic acid significantly improves hydrophilicity of obtained PUR materials and the same cause that they are more suitable candidates for biomedical applications. Good hemocompatibility characteristic of studied PUR materials was confirmed by the hemocompatibility test

  13. Degradability of injectable calcium sulfate/mineralized collagen-based bone repair material and its effect on bone tissue regeneration

    International Nuclear Information System (INIS)

    Chen, Zonggang; Kang, Lingzhi; Meng, Qing-Yuan; Liu, Huanye; Wang, Zhaoliang; Guo, Zhongwu; Cui, Fu-Zhai

    2014-01-01

    The nHAC/CSH composite is an injectable bone repair material with controllable injectability and self-setting properties prepared by introducing calcium sulfate hemihydrate (CSH) into mineralized collagen (nHAC). When mixed with water, the nHAC/CSH composites can be transformed into mineralized collagen/calcium sulfate dihydrate (nHAC/CSD) composites. The nHAC/CSD composites have good biocompatibility and osteogenic capability. Considering that the degradation behavior of bone repair material is another important factor for its clinical applications, the degradability of nHAC/CSD composites was studied. The results showed that the degradation ratio of the nHAC/CSD composites with lower nHAC content increased with the L/S ratio increase of injectable materials, but the variety of L/S ratio had no significant effect on the degradation ratio of the nHAC/CSD composites with higher nHAC content. Increasing nHAC content in the composites could slow down the degradation of nHAC/CSD composite. Setting accelerator had no significant effect on the degradability of nHAC/CSD composites. In vivo histological analysis suggests that the degradation rate of materials can match the growth rate of new mandibular bone tissues in the implanted site of rabbit. The regulable degradability of materials resulting from the special prescriptions of injectable nHAC/CSH composites will further improve the workability of nHAC/CSD composites. - Highlights: • The nHAC/CSH composite can be as an injectable bone repair material. • The L/S ratio and nHAC content have a significant effect on material degradability. • The degradability of bone materials can be regulated to match tissue repair. • The regulable degradability will further improve the workability of bone materials

  14. Degradability of injectable calcium sulfate/mineralized collagen-based bone repair material and its effect on bone tissue regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zonggang, E-mail: chenzg@sdu.edu.cn [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Kang, Lingzhi [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Meng, Qing-Yuan [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, Huanye [Department of Prosthodontics, School of Stomatology, China Medical University, Shenyang 110001 (China); Wang, Zhaoliang [Jinan Military General Hospital of PLA, Jinan 250031 (China); Guo, Zhongwu, E-mail: zwguo@sdu.edu.cn [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Cui, Fu-Zhai, E-mail: cuifz@mail.tsinghua.edu.cn [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2014-12-01

    The nHAC/CSH composite is an injectable bone repair material with controllable injectability and self-setting properties prepared by introducing calcium sulfate hemihydrate (CSH) into mineralized collagen (nHAC). When mixed with water, the nHAC/CSH composites can be transformed into mineralized collagen/calcium sulfate dihydrate (nHAC/CSD) composites. The nHAC/CSD composites have good biocompatibility and osteogenic capability. Considering that the degradation behavior of bone repair material is another important factor for its clinical applications, the degradability of nHAC/CSD composites was studied. The results showed that the degradation ratio of the nHAC/CSD composites with lower nHAC content increased with the L/S ratio increase of injectable materials, but the variety of L/S ratio had no significant effect on the degradation ratio of the nHAC/CSD composites with higher nHAC content. Increasing nHAC content in the composites could slow down the degradation of nHAC/CSD composite. Setting accelerator had no significant effect on the degradability of nHAC/CSD composites. In vivo histological analysis suggests that the degradation rate of materials can match the growth rate of new mandibular bone tissues in the implanted site of rabbit. The regulable degradability of materials resulting from the special prescriptions of injectable nHAC/CSH composites will further improve the workability of nHAC/CSD composites. - Highlights: • The nHAC/CSH composite can be as an injectable bone repair material. • The L/S ratio and nHAC content have a significant effect on material degradability. • The degradability of bone materials can be regulated to match tissue repair. • The regulable degradability will further improve the workability of bone materials.

  15. Preserved microstructure and mineral distribution in tooth and periodontal tissues in early fossil hominin material from Koobi Fora, Kenya.

    Science.gov (United States)

    Klinge, R Furseth; Dean, M C; Risnes, S; Erambert, M; Gunnaes, A E

    2009-01-01

    The aim of this study was to explore further the preservation of tissues and the mineral distribution in 1.6 million-year-old fossil hominin material from Koobi Fora, Kenya attributed to Paranthropus boisei (KNM-ER 1817). Bone, dentine and cementum microstructure were well preserved. Electron microprobe analysis of dentine and bone revealed an F-bearing apatite. Calcite now filled the original soft tissue spaces. The average Ca/P atomic ratio was 1.93, as compared to 1.67 in biological hydroxyapatite, indicating that the Ca-content had increased during fossilization. Analytical sums for mineral content were approximately 90 wt%. Some of the remaining 10 wt% may be preserved organic material. Demineralized dentine fragments showed irregularly distributed tubules encircled with a fibrous-like electron-dense material. A similar material was observed in demineralized dentine. Within this, structures resembling bacteria were seen. In demineralized bone an electron-dense material with a fibrous appearance and a banding pattern that repeated every 64 nm, similar to that of collagen, was noted. SEM of an enamel fragment (KNM-ER 6081) showed signs of demineralization/remineralization. Retzius lines, Hunter-Schreger bands and prism cross-striations spaced 3.7-7.1.microm apart were noted. Prisms were arranged in a pattern 3 configuration and deeper areas containing aprismatic enamel were occasionally observed. We conclude that a great deal of informative microstructure and ultrastructure remains preserved in this fossil material. We also hypothesize that the high mineral content of the tissues may 'protect' parts of the organic matrix from degradation, since our findings indicate that some organic matrix may still be present. Copyright (c) 2009 S. Karger AG, Basel.

  16. Materials from Mussel-Inspired Chemistry for Cell and Tissue Engineering Applications.

    Science.gov (United States)

    Madhurakkat Perikamana, Sajeesh Kumar; Lee, Jinkyu; Lee, Yu Bin; Shin, Young Min; Lee, Esther J; Mikos, Antonios G; Shin, Heungsoo

    2015-09-14

    Current advances in biomaterial fabrication techniques have broadened their application in different realms of biomedical engineering, spanning from drug delivery to tissue engineering. The success of biomaterials depends highly on the ability to modulate cell and tissue responses, including cell adhesion, as well as induction of repair and immune processes. Thus, most recent approaches in the field have concentrated on functionalizing biomaterials with different biomolecules intended to evoke cell- and tissue-specific reactions. Marine mussels produce mussel adhesive proteins (MAPs), which help them strongly attach to different surfaces, even under wet conditions in the ocean. Inspired by mussel adhesiveness, scientists discovered that dopamine undergoes self-polymerization at alkaline conditions. This reaction provides a universal coating for metals, polymers, and ceramics, regardless of their chemical and physical properties. Furthermore, this polymerized layer is enriched with catechol groups that enable immobilization of primary amine or thiol-based biomolecules via a simple dipping process. Herein, this review explores the versatile surface modification techniques that have recently been exploited in tissue engineering and summarizes polydopamine polymerization mechanisms, coating process parameters, and effects on substrate properties. A brief discussion of polydopamine-based reactions in the context of engineering various tissue types, including bone, blood vessels, cartilage, nerves, and muscle, is also provided.

  17. Synthetic bone substitute material comparable with xenogeneic material for bone tissue regeneration in oral cancer patients: First and preliminary histological, histomorphometrical and clinical results.

    Science.gov (United States)

    Ghanaati, Shahram; Barbeck, Mike; Lorenz, Jonas; Stuebinger, Stefan; Seitz, Oliver; Landes, Constantin; Kovács, Adorján F; Kirkpatrick, Charles J; Sader, Robert A

    2013-07-01

    The present study was first to evaluate the material-specific cellular tissue response of patients with head and neck cancer to a nanocrystalline hydroxyapatite bone substitute NanoBone (NB) in comparison with a deproteinized bovine bone matrix Bio-Oss (BO) after implantation into the sinus cavity. Eight patients with tumor resection for oral cancer and severely resorbed maxillary bone received materials according to a split mouth design for 6 months. Bone cores were harvested prior to implantation and analyzed histologically and histomorphometrically. Implant survival was followed-up to 2 years after placement. Histologically, NB underwent a higher vascularization and induced significantly more tartrate-resistant acid phosphatase-positive (TRAP-positive) multinucleated giant cells when compared with BO, which induced mainly mononuclear cells. No significant difference was observed in the extent of new bone formation between both groups. The clinical follow-up showed undisturbed healing of all implants in the BO-group, whereas the loss of one implant was observed in the NB-group. Within its limits, the present study showed for the first time that both material classes evaluated, despite their induction of different cellular tissue reactions, may be useful as augmentation materials for dental and maxillofacial surgical applications, particularly in patients who previously had oral cancer.

  18. 4D printing of polymeric materials for tissue and organ regeneration.

    Science.gov (United States)

    Miao, Shida; Castro, Nathan; Nowicki, Margaret; Xia, Lang; Cui, Haitao; Zhou, Xuan; Zhu, Wei; Lee, Se-Jun; Sarkar, Kausik; Vozzi, Giovanni; Tabata, Yasuhiko; Fisher, John; Zhang, Lijie Grace

    2017-12-01

    Four dimensional (4D) printing is an emerging technology with great capacity for fabricating complex, stimuli-responsive 3D structures, providing great potential for tissue and organ engineering applications. Although the 4D concept was first highlighted in 2013, extensive research has rapidly developed, along with more-in-depth understanding and assertions regarding the definition of 4D. In this review, we begin by establishing the criteria of 4D printing, followed by an extensive summary of state-of-the-art technological advances in the field. Both transformation-preprogrammed 4D printing and 4D printing of shape memory polymers are intensively surveyed. Afterwards we will explore and discuss the applications of 4D printing in tissue and organ regeneration, such as developing synthetic tissues and implantable scaffolds, as well as future perspectives and conclusions.

  19. Accelerator based nuclear analytical methods for trace element studies in materials- calcified tissues

    International Nuclear Information System (INIS)

    Chaudhri, M. Anwar

    2006-01-01

    Full text: Various nuclear analytical methods have been developed and applied to determine the elemental composition of calcified tissues (teeth and bones). Fluorine was determined by prompt gamma activation analysis through the 19 F(p,αγ) 16 O reaction. Carbon was measured by activation analysis with He-3 ions, and the technique of Proton-Induced X-ray Emission (PIXE) was applied to simultaneously determine Ca, P, and trace elements in well-documented teeth. Dental hard tissues: enamel, dentine, cementum, and their junctions, as well as different parts of the same tissue, were examined separately. Furthermore, using a Proton Microprobe, we measured the surface distribution of F and other elements on and around carious lesions on the enamel. The depth profiles of F, and other elements, were also measured right up to the amelodentin junction. (author)

  20. Effects of collagen microstructure and material properties on the deformation of the neural tissues of the lamina cribrosa.

    Science.gov (United States)

    Voorhees, A P; Jan, N-J; Sigal, I A

    2017-08-01

    It is widely considered that intraocular pressure (IOP)-induced deformation within the neural tissue pores of the lamina cribrosa (LC) contributes to neurodegeneration and glaucoma. Our goal was to study how the LC microstructure and mechanical properties determine the mechanical insult to the neural tissues within the pores of the LC. Polarized light microscopy was used to measure the collagen density and orientation in histology sections of three sheep optic nerve heads (ONH) at both mesoscale (4.4μm) and microscale (0.73μm) resolutions. Mesoscale fiber-aware FE models were first used to calculate ONH deformations at an IOP of 30mmHg. The results were then used as boundary conditions for microscale models of LC regions. Models predicted large insult to the LC neural tissues, with 95th percentile 1st principal strains ranging from 7 to 12%. Pores near the scleral boundary suffered significantly higher stretch compared to pores in more central regions (10.0±1.4% vs. 7.2±0.4%; p=0.014; mean±SD). Variations in material properties altered the minimum, median, and maximum levels of neural tissue insult but largely did not alter the patterns of pore-to-pore variation, suggesting these patterns are determined by the underlying structure and geometry of the LC beams and pores. To the best of our knowledge, this is the first computational model that reproduces the highly heterogeneous neural tissue strain fields observed experimentally. The loss of visual function associated with glaucoma has been attributed to sustained mechanical insult to the neural tissues of the lamina cribrosa due to elevated intraocular pressure. Our study is the first computational model built from specimen-specific tissue microstructure to consider the mechanics of the neural tissues of the lamina separately from the connective tissue. We found that the deformation of the neural tissue was much larger than that predicted by any recent microstructure-aware models of the lamina. These results

  1. Equivalent Dynamic Models.

    Science.gov (United States)

    Molenaar, Peter C M

    2017-01-01

    Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results. The known equivalent vector autoregressive model types, standard and structural, are given a new interpretation in which they are conceived of as the extremes of an innovating type of hybrid vector autoregressive models. It is shown that consideration of hybrid models solves many problems, in particular with Granger causality testing.

  2. Calculation of equivalent dose index for electrons from 5,0 to 22,0 MeV by the Monte Carlo method

    International Nuclear Information System (INIS)

    Peixoto, J.E.

    1979-01-01

    The index of equivalent dose in depth and in a sphere surface of a soft tissue equivalent material were determined by Monte Carlo method for electron irradiations from 5,0 to 22.00 MeV. The effect of different irradiation geometries which simulate the incidence of onedirectional opposite rotational and isotropic beams was studied. It is also shown that the detector of wall thickness with 0.5g/cm 2 and isotropic response com be used to measure index of equivalent dose for fast electrons. The alternative concept of average equivalent dose for radiation protection is discussed. (M.C.K.) [pt

  3. Biomimetic materials and design: biointerfacial strategies, tissue engineering, and targeted drug delivery

    National Research Council Canada - National Science Library

    Dillow, Angela K; Lowman, Anthony M

    2002-01-01

    ... significant immune responses or toxicity issues- became the focus of the rational decision for materials to be used within the body. Biodegradable polymers also became (and still are) a focus of much research in the area of biomaterials science. Using biodegradable materials, the goal is to produce polymers with appropriate mechanical properties that de...

  4. 3D Printing of Lotus Root-Like Biomimetic Materials for Cell Delivery and Tissue Regeneration.

    Science.gov (United States)

    Feng, Chun; Zhang, Wenjie; Deng, Cuijun; Li, Guanglong; Chang, Jiang; Zhang, Zhiyuan; Jiang, Xinquan; Wu, Chengtie

    2017-12-01

    Biomimetic materials have drawn more and more attention in recent years. Regeneration of large bone defects is still a major clinical challenge. In addition, vascularization plays an important role in the process of large bone regeneration and microchannel structure can induce endothelial cells to form rudimentary vasculature. In recent years, 3D printing scaffolds are major materials for large bone defect repair. However, these traditional 3D scaffolds have low porosity and nonchannel structure, which impede angiogenesis and osteogenesis. In this study, inspired by the microstructure of natural plant lotus root, biomimetic materials with lotus root-like structures are successfully prepared via a modified 3D printing strategy. Compared with traditional 3D materials, these biomimetic materials can significantly improve in vitro cell attachment and proliferation as well as promote in vivo osteogenesis, indicating potential application for cell delivery and bone regeneration.

  5. 3D Printing of Lotus Root‐Like Biomimetic Materials for Cell Delivery and Tissue Regeneration

    Science.gov (United States)

    Feng, Chun; Zhang, Wenjie; Deng, Cuijun; Li, Guanglong; Chang, Jiang; Zhang, Zhiyuan

    2017-01-01

    Abstract Biomimetic materials have drawn more and more attention in recent years. Regeneration of large bone defects is still a major clinical challenge. In addition, vascularization plays an important role in the process of large bone regeneration and microchannel structure can induce endothelial cells to form rudimentary vasculature. In recent years, 3D printing scaffolds are major materials for large bone defect repair. However, these traditional 3D scaffolds have low porosity and nonchannel structure, which impede angiogenesis and osteogenesis. In this study, inspired by the microstructure of natural plant lotus root, biomimetic materials with lotus root‐like structures are successfully prepared via a modified 3D printing strategy. Compared with traditional 3D materials, these biomimetic materials can significantly improve in vitro cell attachment and proliferation as well as promote in vivo osteogenesis, indicating potential application for cell delivery and bone regeneration. PMID:29270348

  6. On uncertainties in definition of dose equivalent

    International Nuclear Information System (INIS)

    Oda, Keiji

    1995-01-01

    The author has entertained always the doubt that in a neutron field, if the measured value of the absorbed dose with a tissue equivalent ionization chamber is 1.02±0.01 mGy, may the dose equivalent be taken as 10.2±0.1 mSv. Should it be 10.2 or 11, but the author considers it is 10 or 20. Even if effort is exerted for the precision measurement of absorbed dose, if the coefficient being multiplied to it is not precise, it is meaningless. [Absorbed dose] x [Radiation quality fctor] = [Dose equivalent] seems peculiar. How accurately can dose equivalent be evaluated ? The descriptions related to uncertainties in the publications of ICRU and ICRP are introduced, which are related to radiation quality factor, the accuracy of measuring dose equivalent and so on. Dose equivalent shows the criterion for the degree of risk, or it is considered only as a controlling quantity. The description in the ICRU report 1973 related to dose equivalent and its unit is cited. It was concluded that dose equivalent can be considered only as the absorbed dose being multiplied by a dimensionless factor. The author presented the questions. (K.I.)

  7. New Coll–HA/BT composite materials for hard tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Zanfir, Andrei Vlad [Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Material Science, “Politehnica” University of Bucharest, 1-7 Gh. Polizu Street, RO-011061 Bucharest (Romania); Voicu, Georgeta, E-mail: getav2001@yahoo.co.uk [Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Material Science, “Politehnica” University of Bucharest, 1-7 Gh. Polizu Street, RO-011061 Bucharest (Romania); Busuioc, Cristina; Jinga, Sorin Ion [Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Material Science, “Politehnica” University of Bucharest, 1-7 Gh. Polizu Street, RO-011061 Bucharest (Romania); Albu, Madalina Georgiana [Department of Collagen, Branch of Leather and Footwear Research, National Institute of Research and Development for Textile and Leather, 93 I. Minulescu Street, RO-031215 Bucharest (Romania); Iordache, Florin [Department of Fetal and Adult Stem Cell Therapy, “Nicolae Simionescu” Institute of Cellular Biology and Pathology of Romanian Academy, 8 B.P. Hasdeu Street, RO-050568 Bucharest (Romania)

    2016-05-01

    The integration of ceramic powders in composite materials for bone scaffolds can improve the osseointegration process. This work was aimed to the synthesis and characterization of new collagen–hydroxyapatite/barium titanate (Coll–HA/BT) composite materials starting from barium titanate (BT) nanopowder, hydroxyapatite (HA) nanopowder and collagen (Coll) gel. BT nanopowder was produced by combining two wet-chemical approaches, sol–gel and hydrothermal methods. The resulting materials were characterized in terms of phase composition and microstructure by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Moreover, the biocompatibility and bioactivity of the composite materials were assessed by in vitro tests. The synthesized BT particles exhibit an average size of around 35 nm and a spherical morphology, with a pseudo-cubic or tetragonal symmetry. The diffraction spectra of Coll–HA and Coll–HA/BT composite materials indicate a pronounced interaction between Col and the mineral phases, meaning a good mineralization of Col fibres. As well, the in vitro tests highlight excellent osteoinductive properties for all biological samples, especially for Coll–HA/BT composite materials, fact that can be attributed to the ferromagnetic properties of BT. - Highlights: • Collagen–hydroxyapatite/barium titanate composite materials were synthesized. • Barium titanate was produced by combining the sol–gel and hydrothermal methods. • The in vitro tests highlight excellent osteoinductive properties for all samples.

  8. New Coll–HA/BT composite materials for hard tissue engineering

    International Nuclear Information System (INIS)

    Zanfir, Andrei Vlad; Voicu, Georgeta; Busuioc, Cristina; Jinga, Sorin Ion; Albu, Madalina Georgiana; Iordache, Florin

    2016-01-01

    The integration of ceramic powders in composite materials for bone scaffolds can improve the osseointegration process. This work was aimed to the synthesis and characterization of new collagen–hydroxyapatite/barium titanate (Coll–HA/BT) composite materials starting from barium titanate (BT) nanopowder, hydroxyapatite (HA) nanopowder and collagen (Coll) gel. BT nanopowder was produced by combining two wet-chemical approaches, sol–gel and hydrothermal methods. The resulting materials were characterized in terms of phase composition and microstructure by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Moreover, the biocompatibility and bioactivity of the composite materials were assessed by in vitro tests. The synthesized BT particles exhibit an average size of around 35 nm and a spherical morphology, with a pseudo-cubic or tetragonal symmetry. The diffraction spectra of Coll–HA and Coll–HA/BT composite materials indicate a pronounced interaction between Col and the mineral phases, meaning a good mineralization of Col fibres. As well, the in vitro tests highlight excellent osteoinductive properties for all biological samples, especially for Coll–HA/BT composite materials, fact that can be attributed to the ferromagnetic properties of BT. - Highlights: • Collagen–hydroxyapatite/barium titanate composite materials were synthesized. • Barium titanate was produced by combining the sol–gel and hydrothermal methods. • The in vitro tests highlight excellent osteoinductive properties for all samples.

  9. Nonlinear and anisotropic tensile properties of graft materials used in soft tissue applications.

    Science.gov (United States)

    Yoder, Jonathon H; Elliott, Dawn M

    2010-05-01

    The mechanical properties of extracellular matrix grafts that are intended to augment or replace soft tissues should be comparable to the native tissue. Such grafts are often used in fiber-reinforced tissue applications that undergo multi-axial loading and therefore knowledge of the anisotropic and nonlinear properties are needed, including the moduli and Poisson's ratio in two orthogonal directions within the plane of the graft. The objective of this study was to measure the tensile mechanical properties of several marketed grafts: Alloderm, Restore, CuffPatch, and OrthADAPT. The degree of anisotropy and non-linearity within each graft was evaluated from uniaxial tensile tests and compared to their native tissue. The Alloderm graft was anisotropic in both the toe- and linear-region of the stress-strain response, was highly nonlinear, and generally had low properties. The Restore and CuffPatch grafts had similar stress-strain responses, were largely isotropic, had a linear-region modulus of 18MPa, and were nonlinear. OrthADAPT was anisotropic in the linear-region (131 MPA vs 47MPa in the toe-region) and was highly nonlinear. The Poisson ratio for all grafts was between 0.4 and 0.7, except for the parallel orientation of Restore which was greater than 1.0. Having an informed understanding of how the available grafts perform mechanically will allow for better assessment by the physician for which graft to apply depending upon its application. Copyright 2010 Elsevier Ltd. All rights reserved.

  10. Silicone-based composite materials simulate breast tissue to be used as ultrasonography training phantoms.

    Science.gov (United States)

    Ustbas, Burcin; Kilic, Deniz; Bozkurt, Ayhan; Aribal, Mustafa Erkin; Akbulut, Ozge

    2018-03-02

    A silicone-based composite breast phantom is fabricated to be used as an education model in ultrasonography training. A matrix of silicone formulations is tracked to mimic the ultrasonography and tactile response of human breast tissue. The performance of two different additives: (i) silicone oil and (ii) vinyl-terminated poly (dimethylsiloxane) (PDMS) are monitored by a home-made acoustic setup. Through the use of 75 wt% vinyl-terminated PDMS in two-component silicone elastomer mixture, a sound velocity of 1.29 ± 0.09 × 10 3  m/s and an attenuation coefficient of 12.99 ± 0.08 dB/cm-values those match closely to the human breast tissue-are measured with 5 MHz probe. This model can also be used for needle biopsy as well as for self-exam trainings. Herein, we highlight the fabrication of a realistic, durable, accessible, and cost-effective training platform that contains skin layer, inner breast tissue, and tumor masses. Copyright © 2018. Published by Elsevier B.V.

  11. Biocompatible nanocomposite of TiO2 incorporated bi-polymer for articular cartilage tissue regeneration: A facile material.

    Science.gov (United States)

    Cao, Lei; Wu, Xiaofeng; Wang, Qiugen; Wang, Jiandong

    2018-01-01

    The development and design of polymeric hydrogels for articular cartilage tissue engineering have been a vital biomedical research for recent days. Organic/inorganic combined hydrogels with improved surface activity have shown potential for the repair and regeneration of hard tissues, but have not been broadly studied for articular cartilage tissue engineering applications. In this work, bi-polymeric hydrogel composite was designed with the incorporation some quantities of stick-like TiO 2 nanostructures for favorable surface behavior and enhancement of osteoblast adhesions. The microscopic investigations clearly exhibited that the stick-like TiO 2 nanostructured materials are highly inserted into the PVA/PVP bi-polymeric matrix, due to the long-chain PVA molecules are promoted to physical crosslinking density in hydrogel network. The results of improved surface topography of hydrogel matrixes show that more flatted cell morphologies and enhanced osteoblast attachment on the synthesized nanocomposites. The crystalline bone and stick-like TiO 2 nanocomposites significantly improved the bioactivity via lamellipodia and filopodia extension of osteoblast cells, due to its excellent intercellular connection and regulated cell responses. Consequently, these hydrogel has been enhanced the antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial pathogens. Hence it is concluded that these hydrogel nanocomposite with improved morphology, osteoblast behavior and bactericidal activity have highly potential candidates for articular cartilage tissue regeneration applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. The effect of disinfectant agents on dimensional stability and surface roughness of a tissue conditioner material

    Directory of Open Access Journals (Sweden)

    Amiralireza Khaledi

    2011-01-01

    Conclusion: The results showed that the disinfectant solutions used in this study did not have a significant effect on the surface quality and dimensional accuracy of Visco-gel as a functional impression material.

  13. P(3HB) based magnetic nanocomposites: smart materials for bone tissue engineering

    Czech Academy of Sciences Publication Activity Database

    Akaraonye, E.; Filip, J.; Šafaříková, Miroslava; Salih, V.; Keshavarz, T.; Knowles, J.C.; Roy, I.

    -, č. 2016 (2016), č. článku 3897592. ISSN 1687-4110 Institutional support: RVO:60077344 Keywords : composite films * dispersions * elastic moduli * intelligent materials * nanocomposites Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.871, year: 2016

  14. Novel bio-synthetic hybrid materials and coculture systems for musculoskeletal tissue engineering

    Science.gov (United States)

    Lee, Hyeseung Janice

    Tissue Engineering is a truly exciting field of this age, trying to regenerate and repair impaired tissues. Unlike the old artificial implants, tissue engineering aims at making a long-term functional biological replacement. One strategy for such tissue engineering requires the following three components: cells, scaffolds, and soluble factors. Cells are cultured in a three-dimensional (3D) scaffold with medium containing various soluble factors. Once a tissue is developed in vitro, then it is implanted in vivo. The overall goal of this thesis was to develop novel bio-synthetic hybrid scaffolds and coculture system for musculoskeletal tissue engineering. The most abundant cartilage extracellular matrix (ECM) components are collagen and glycosaminoglycan (GAG), which are the natural scaffold for chondrocytes. As two different peptides, collagen mimetic peptide (CMP) and hyaluronic acid binding peptide (HABPep) were previously shown to bind to collagen and hyaluronic acid (HA) of GAG, respectively, it was hypothesized that immobilizing CMP and HABP on 3D scaffold would results in an interaction between ECM components and synthetic scaffolds via peptide-ECM bindings. CMP or HABPep-conjugated photopolymerizable poly(ethylene oxide) diacrylate (PEODA) hydrogels were synthesized and shown to retain encapsulated collagen or HA, respectively. This result supported that conjugated CMP and HABPep can interact with collagen and HA, respectively, and can serve as biological linkers in 3D synthetic hydrogels. When chondrocytes or mesenchymal stem cells (MSCs) were seeded, cells in CMP-conjugated scaffolds produced significantly more amount of type II collagen and GAG, compared to those in control scaffolds. Moreover, MSCs cultured in CMP-conjugated scaffolds exhibited lower level of hypertrophic markers, cbfa-1 and type X collagen. These results demonstrated that enhanced interaction between collagen and scaffold via CMP improves chondrogenesis of chondrocytes and MSCs and

  15. Introgression of genetic material from Zea mays ssp. Mexicana into cultivated maize was facilitated by tissue culture

    International Nuclear Information System (INIS)

    Wang, L.; Gu, X.; Qu, M.; Luan, J.; Zhang, J.

    2012-01-01

    Zea mays ssp. mexicana, a wild relative of cultivated maize (Z. mays ssp. mays), is a useful gene resource for maize breeding. In this study, two populations were generated by conventional breeding scheme (population I) or tissue culture regime (population II), respectively, to introgress genetic material of Z. mays ssp. mexicana into maize. Karyotype analysis showed that the arm ratios of 10 pairs of chromosomes in parent maize Ye515 and derivative lines from 2 different populations with 26% and 38% chromosome variation frequencies, respectively. Alien chromatin was detected in the root tip cells of progeny plants through genomic in situ hybridization (GISH). There were 3.3 chromosomes carrying alien chromatin on average in population I and 6.5 in population II. The hybridization signals were located mainly at the terminal or sub terminal regions of the chromosomes and the sizes were notably variant among lines. Based on those results, it is concluded that the introgression of genetic material from Z. mays ssp. mexicana into cultivated maize was facilitated by tissue culture, and subsequently some excellent materials for maize breeding were created. (author)

  16. Electrospun collagen-based nanofibres: A sustainable material for improved antibiotic utilisation in tissue engineering applications.

    Science.gov (United States)

    Hall Barrientos, Ivan J; Paladino, Eleonora; Szabó, Peter; Brozio, Sarah; Hall, Peter J; Oseghale, Charles I; Passarelli, Melissa K; Moug, Susan J; Black, Richard A; Wilson, Clive G; Zelkó, Romana; Lamprou, Dimitrios A

    2017-10-05

    For the creation of scaffolds in tissue engineering applications, it is essential to control the physical morphology of fibres and to choose compositions which do not disturb normal physiological function. Collagen, the most abundant protein in the human body, is a well-established biopolymer used in electrospinning compositions. It shows high in-vivo stability and is able to maintain a high biomechanical strength over time. In this study, the effects of collagen type I in polylactic acid-drug electrospun scaffolds for tissue engineering applications are examined. The samples produced were subsequently characterised using a range of techniques. Scanning electron microscopy analysis shows that the fibre morphologies varied across PLA-drug and PLA-collagen-drug samples - the addition of collagen caused a decrease in average fibre diameter by nearly half, and produced nanofibres. Atomic force microscopy imaging revealed collagen-banding patterns which show the successful integration of collagen with PLA. Solid-state characterisation suggested a chemical interaction between PLA and drug compounds, irgasan and levofloxacin, and the collagen increased the amorphous regions within the samples. Surface energy analysis of drug powders showed a higher dispersive surface energy of levofloxacin compared with irgasan, and contact angle goniometry showed an increase in hydrophobicity in PLA-collagen-drug samples. The antibacterial studies showed a high efficacy of resistance against the growth of both E. coli and S. Aureus, except with PLA-collagen-LEVO which showed a regrowth of bacteria after 48h. This can be attributed to the low drug release percentage incorporated into the nanofibre during the in vitro release study. However, the studies did show that collagen helped shift both drugs into sustained release behaviour. These ideal modifications to electrospun scaffolds may prove useful in further research regarding the acceptance of human tissue by inhibiting the potential

  17. Proton energy determinations in water and in tissue-like material

    Energy Technology Data Exchange (ETDEWEB)

    Laitano, R F [Ist. Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA, Roma (Italy); Rosetti, M [Div. di Fisica Applicata, ENEA, Bologna (Italy)

    1997-09-01

    The mean energy of proton beams in water and in a tissue substitute, respectively, were determined as a function of SOBP width, beam size and initial energy spread. Then an analytical expression to obtain the proton mean energy as a function of phantom depth and initial energy was established. This expression differs from the analogous ones reported in some current dosimetry protocols in that it accounts for the nuclear interaction effects in determining the mean energy. The preliminary results of the calculations referred to above are reported together with some comments on the specification of the proton beam quality for clinical dosimetry. (orig.)

  18. Preparation, characterization and use of a reference material to proficiency testing for determination of metals in fish tissue in natura

    International Nuclear Information System (INIS)

    Santana, Luciana Vieira de

    2013-01-01

    The proficiency tests are widely used to evaluate the analytical capacity of laboratories and also as part of the accreditation process. For this reason, are important tools for the control of the quality of the analytical results obtained in the laboratories that work directly with seafood companies. In Brazil there are no providers of proficiency testing for metals potentially toxic in fish tissues. In this work will be described all steps used for the production of reference materials to be used in a proficiency testing pilot study for As, Cd, Pb and Hg in fish tissue following the recommendations of the ISO Guide 35. He preparation scheme consisted in selecting the individuals, cleaning, grinding, homogenization and fortification with As, Cd and Pb in two concentration levels. The preparation resulted in 164 sachets of 10 g each. In order to evaluate the effect of gamma irradiation in the samples conservation 52 sachets were irradiated with 60 Co (10.00 ± 1.05 kGy) in a gamma cell. This material with others non irradiated 52 sachets were used for the homogeneity and stability studies. The remaining 60 were used for the proficiency testing. The results demonstrated that both materials were homogeneous and presented good stability (during a period of 45 days). However, the irradiated material present better integrity, concerning biological degradation, when stored in ambient temperature. For this reason they were used to the proficiency testing pilot program. Ten laboratories participated in the proficiency testing pilot study and the results were evaluated using the following tests: z-score, confidence ellipse and En numbers. This work demonstrates the capability of the laboratory to produce reference materials as well as to organize and conduct proficiency testing. (author)

  19. Beneficial effects of a N-terminally modified GIP agonist on tissue-level bone material properties.

    Science.gov (United States)

    Mabilleau, Guillaume; Mieczkowska, Aleksandra; Irwin, Nigel; Simon, Yannick; Audran, Maurice; Flatt, Peter R; Chappard, Daniel

    2014-06-01

    Bone remodeling is under complex regulation from nervous, hormonal and local signals, including gut hormones. Among the gut hormones, a role for the glucose-dependent insulinotropic polypeptide (GIP) has been suggested. However, the rapid degradation of GIP in the bloodstream by the ubiquitous enzyme dipeptidyl peptidase-4 (DPP-4) precludes therapeutic use. To circumvent this problem, a series of N-terminally modified GIP agonists have been developed, with N-AcGIP being the most promising. The aims of the present study were to investigate the effects of N-AcGIP on bone at the micro-level using trabecular and cortical microstructural morphology, and at the tissue-level in rats. Copenhagen rats were randomly assigned into control or N-AcGIP-treated groups and received daily injection for 4 weeks. Bone microstructural morphology was assessed by microCT and dynamic histomorphometry and tissue-level properties by nanoindentation, qBEI and infra-red microscopy. Four week treatment with N-AcGIP did not alter trabecular or cortical microstructural morphology. In addition, no significant modifications of mechanical response and properties at the tissue-level were observed in trabecular bone. However, significant augmentations in maximum load (12%), hardness (14%), indentation modulus (13%) and dissipated energy (16%) were demonstrated in cortical bone. These beneficial modifications of mechanical properties at the tissue-level were associated with increased mineralization (22%) and collagen maturity (13%) of the bone matrix. Taken together, the results support a beneficial role of GIP, and particularly stable analogs such as N-AcGIP, on tissue material properties of bone. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Development and characterization of a synthetic PVC/DEHP myocardial tissue analogue material for CT imaging applications.

    Science.gov (United States)

    Ramadan, Sherif; Paul, Narinder; Naguib, Hani E

    2018-04-01

    A simple myocardial analogue material has great potential to help researchers in the creation of medical CT Imaging phantoms. This work aims to outline a Bis(2-ethylhexyl) phthalate (DEHP) plasticizer/PVC material to achieve this. DEHP-PVC was manufactured in three ratios, 75, 80, and 85% DEHP by heating at 110 °C for 10 min to promote DEHP-PVC binding followed by heating at 150 °C to melt the blend. The material was then tested utilizing FTIR, tensile testing, dynamic mechanical analysis and imaged with computed tomography. The FTIR testing finds the presence of C-CL and carbonyl bonds that demonstrate the binding required in this plasticized material. The tensile testing finds a modulus of 180-20 kPa that increases with the proportion of plasticizer. The dynamic mechanical analysis finds a linear increase in viscoelastic properties with a storage/loss modulus of 6/.5-120/18 kPa. Finally, the CT number of the material increases with higher PVC content from 55 to 144HU. The 80% DEHP-PVC ratio meets the mechanical and CT properties necessary to function as a myocardial tissue analogue.

  1. Derived equivalences for group rings

    CERN Document Server

    König, Steffen

    1998-01-01

    A self-contained introduction is given to J. Rickard's Morita theory for derived module categories and its recent applications in representation theory of finite groups. In particular, Broué's conjecture is discussed, giving a structural explanation for relations between the p-modular character table of a finite group and that of its "p-local structure". The book is addressed to researchers or graduate students and can serve as material for a seminar. It surveys the current state of the field, and it also provides a "user's guide" to derived equivalences and tilting complexes. Results and proofs are presented in the generality needed for group theoretic applications.

  2. Modelling radiation fields of ion beams in tissue-like materials

    International Nuclear Information System (INIS)

    Burigo, Lucas Norberto

    2014-01-01

    Fast nuclei are ionizing radiation which can cause deleterious effects to irradiated cells. The modelling of the interactions of such ions with matter and the related effects are very important to physics, radiobiology, medicine and space science and technology. A powerful method to study the interactions of ionizing radiation with biological systems was developed in the field of microdosimetry. Microdosimetry spectra characterize the energy deposition to objects of cellular size, i.e., a few micrometers. In the present thesis the interaction of ions with tissue-like media was investigated using the Monte Carlo model for Heavy-Ion Therapy (MCHIT) developed at the Frankfurt Institute for Advanced Studies. MCHIT is a Geant4-based application intended to benchmark the physical models of Geant4 and investigate the physical properties of therapeutic ion beams. We have implemented new features in MCHIT in order to calculate microdosimetric quantities characterizing the radiation fields of accelerated nucleons and nuclei. The results of our Monte Carlo simulations were compared with recent experimental microdosimetry data. In addition to microdosimetry calculations with MCHIT, we also investigated the biological properties of ion beams, e.g. their relative biological effectiveness (RBE), by means of the modified Microdosimetric-Kinetic model (MKM). The MKM uses microdosimetry spectra in describing cell response to radiation. MCHIT+MKM allowed us to study the physical and biological properties of ion beams. The main results of the thesis are as follows: MCHIT is able to describe the spatial distribution of the physical dose in tissue-like media and microdosimetry spectra for ions with energies relevant to space research and ion-beam cancer therapy; MCHIT+MKM predicts a reduction of the biological effectiveness of ions propagating in extended medium due to nuclear fragmentation reactions; We predicted favourable biological dose-depth profiles for monoenergetic helium and

  3. The principle of equivalence

    International Nuclear Information System (INIS)

    Unnikrishnan, C.S.

    1994-01-01

    Principle of equivalence was the fundamental guiding principle in the formulation of the general theory of relativity. What are its key elements? What are the empirical observations which establish it? What is its relevance to some new experiments? These questions are discussed in this article. (author). 11 refs., 5 figs

  4. Radioactive waste equivalence

    International Nuclear Information System (INIS)

    Orlowski, S.; Schaller, K.H.

    1990-01-01

    The report reviews, for the Member States of the European Community, possible situations in which an equivalence concept for radioactive waste may be used, analyses the various factors involved, and suggests guidelines for the implementation of such a concept. Only safety and technical aspects are covered. Other aspects such as commercial ones are excluded. Situations where the need for an equivalence concept has been identified are processes where impurities are added as a consequence of the treatment and conditioning process, the substitution of wastes from similar waste streams due to the treatment process, and exchange of waste belonging to different waste categories. The analysis of factors involved and possible ways for equivalence evaluation, taking into account in particular the chemical, physical and radiological characteristics of the waste package, and the potential risks of the waste form, shows that no simple all-encompassing equivalence formula may be derived. Consequently, a step-by-step approach is suggested, which avoids complex evaluations in the case of simple exchanges

  5. Equivalent Colorings with "Maple"

    Science.gov (United States)

    Cecil, David R.; Wang, Rongdong

    2005-01-01

    Many counting problems can be modeled as "colorings" and solved by considering symmetries and Polya's cycle index polynomial. This paper presents a "Maple 7" program link http://users.tamuk.edu/kfdrc00/ that, given Polya's cycle index polynomial, determines all possible associated colorings and their partitioning into equivalence classes. These…

  6. Correspondences. Equivalence relations

    International Nuclear Information System (INIS)

    Bouligand, G.M.

    1978-03-01

    We comment on sections paragraph 3 'Correspondences' and paragraph 6 'Equivalence Relations' in chapter II of 'Elements de mathematique' by N. Bourbaki in order to simplify their comprehension. Paragraph 3 exposes the ideas of a graph, correspondence and map or of function, and their composition laws. We draw attention to the following points: 1) Adopting the convention of writting from left to right, the composition law for two correspondences (A,F,B), (U,G,V) of graphs F, G is written in full generality (A,F,B)o(U,G,V) = (A,FoG,V). It is not therefore assumed that the co-domain B of the first correspondence is identical to the domain U of the second (EII.13 D.7), (1970). 2) The axiom of choice consists of creating the Hilbert terms from the only relations admitting a graph. 3) The statement of the existence theorem of a function h such that f = goh, where f and g are two given maps having the same domain (of definition), is completed if h is more precisely an injection. Paragraph 6 considers the generalisation of equality: First, by 'the equivalence relation associated with a map f of a set E identical to (x is a member of the set E and y is a member of the set E and x:f = y:f). Consequently, every relation R(x,y) which is equivalent to this is an equivalence relation in E (symmetrical, transitive, reflexive); then R admits a graph included in E x E, etc. Secondly, by means of the Hilbert term of a relation R submitted to the equivalence. In this last case, if R(x,y) is separately collectivizing in x and y, theta(x) is not the class of objects equivalent to x for R (EII.47.9), (1970). The interest of bringing together these two subjects, apart from this logical order, resides also in the fact that the theorem mentioned in 3) can be expressed by means of the equivalence relations associated with the functions f and g. The solutions of the examples proposed reveal their simplicity [fr

  7. Recovery of material parameters of soft hyperelastic tissue by an inverse spectral technique

    KAUST Repository

    Gou, Kun

    2012-07-01

    An inverse spectral method is developed for recovering a spatially inhomogeneous shear modulus for soft tissue. The study is motivated by a novel use of the intravascular ultrasound technique to image arteries. The arterial wall is idealized as a nonlinear isotropic cylindrical hyperelastic body. A boundary value problem is formulated for the response of the arterial wall within a specific class of quasistatic deformations reflective of the response due to imposed blood pressure. Subsequently, a boundary value problem is developed via an asymptotic construction modeling intravascular ultrasound interrogation which generates small amplitude, high frequency time harmonic vibrations superimposed on the static finite deformation. This leads to a system of second order ordinary Sturm-Liouville boundary value problems that are then employed to reconstruct the shear modulus through a nonlinear inverse spectral technique. Numerical examples are demonstrated to show the viability of the method. © 2012 Elsevier Ltd. All rights reserved.

  8. Integrin expression by human osteoblasts cultured on degradable polymeric materials applicable for tissue engineered bone.

    Science.gov (United States)

    El-Amin, Saadiq F; Attawia, Mohamed; Lu, Helen H; Shah, Asist K; Chang, Richard; Hickok, Noreen J; Tuan, Rocky S; Laurencin, Cato T

    2002-01-01

    The use of biodegradable polymers in the field of orthopaedic surgery has gained increased popularity, as surgical pins and screws, and as potential biological scaffolds for repairing cartilage and bone defects. One such group of polymers that has gained considerable attention are the polyesters, poly(lactide-co-glycolide) (PLAGA) and polylactic acid (PLA), because of their minimal tissue inflammatory response, favorable biocompatibility and degradation characteristics. The objective of this study was to evaluate human osteoblastic cell adherence and growth on PLAGA and PLA scaffolds by examining integrin receptor (alpha2, alpha3, alpha4, alpha5, alpha6 and beta1) expression. Primary human osteoblastic cells isolated from trabecular bone adhered efficiently to both PLAGA and PLA, with the rate of adherence on PLAGA comparable to that of control tissue culture polystyrene (TCPS), and significantly higher than on PLA polymers at 3, 6 and 12 h. Human osteoblastic phenotypic expression, alkaline phosphatase (ALP) activity was positive on both degradable matrices, whereas osteocalcin levels were significantly higher on cells grown on PLAGA than on PLA composites. Interestingly, the integrin subunits, alpha2, alpha3, alpha4, alpha5, alpha6 and beta1 were all expressed at higher levels by osteoblasts cultured on PLAGA than those on PLA as analyzed by westerns blots and by flow cytometry. Among the integrins, alpha2, beta5 and beta1 showed the greatest difference in levels between the two surfaces. Thus, both PLA and PLAGA support osteoblastic adhesion and its accompanying engagement of integrin receptor and expression of osteocalcin and ALP. However PLAGA consistently appeared to be a better substrate for osteoblastic cells based on these parameters. This study is one of the first to investigate the ability of primary human osteoblastic cells isolated from trabecular bone to adhere to the biodegradable polymers PLAGA and PLA, and to examine the expression of their key

  9. Nanomaterial translocation - the biokinetics, tissue accumulation, toxicity and fate of materials in secondary organs

    DEFF Research Database (Denmark)

    Kermanizadeh, Ali; Balharry, Dominique; Wallin, Håkan

    2015-01-01

    into the toxicity posed by the NMs in these secondary organs is expanding due to the realisation that some materials may reach and accumulate in these target sites. The translocation to secondary organs includes, but is not limited to, the hepatic, central nervous, cardiovascular and renal systems. Current data...... dioxide and quantum dots) or fast (e.g. zinc oxide) solubility. The translocation of NMs following intratracheal, intranasal and pharyngeal aspiration is higher (up to 10% of administered dose), however the relevance of these routes for risk assessment is questionable. Uptake of the materials from....... For toxicological and risk evaluation, further information on the toxicokinetics and persistence of NMs is crucial. The overall aim of this review is to outline the data currently available in the literature on the biokinetics, accumulation, toxicity and eventual fate of NMs in order to assess the potential risks...

  10. Nanoscale definition of substrate materials to direct human adult stem cells towards tissue specific populations.

    Science.gov (United States)

    Curran, Judith M; Chen, Rui; Stokes, Robert; Irvine, Eleanor; Graham, Duncan; Gubbins, Earl; Delaney, Deany; Amro, Nabil; Sanedrin, Raymond; Jamil, Haris; Hunt, John A

    2010-03-01

    The development of homogenously nano-patterned chemically modified surfaces that can be used to initiate a cellular response, particularly stem cell differentiation, in a highly controlled manner without the need for exogenous biological factors has never been reported, due to that fact that precisely defined and reproducible systems have not been available that can be used to study cell/material interactions and unlock the potential of a material driven cell response. Until now material driven stem cell (furthermore any cell) responses have been variable due to the limitations in definition and reproducibility of the underlying substrate and the lack of true homogeneity of modifications that can dictate a cellular response at a sub-micron level that can effectively control initial cell interactions of all cells that contact the surface. Here we report the successful design and use of homogenously molecularly nanopatterned surfaces to control initial stem cell adhesion and hence function. The highly specified nano-patterned arrays were compared directly to silane modified bulk coated substrates that have previously been proven to initiate mesenchymal stem cell (MSC) differentiation in a heterogenous manner, the aim of this study was to prove the efficiency of these previously observed cell responses could be enhanced by the incorporation of nano-patterns. Nano-patterned surfaces were prepared by Dip Pen Nanolithography (DPN) to produce arrays of 70 nm sized dots separated by defined spacings of 140, 280 and 1000 nm with terminal functionalities of carboxyl, amino, methyl and hydroxyl and used to control cell growth. These nanopatterned surfaces exhibited unprecedented control of initial cell interactions and will change the capabilities for stem cell definition in vitro and then cell based medical therapies. In addition to highlighting the ability of the materials to control stem cell functionality on an unprecedented scale this research also introduces the

  11. Preparation, characteristics and assessment of a novel gelatin-chitosan sponge scaffold as skin tissue engineering material.

    Science.gov (United States)

    Han, Fei; Dong, Yang; Su, Zhen; Yin, Ran; Song, Aihua; Li, Sanming

    2014-12-10

    In order to develop a skin tissue engineering material for wound dressing application, a novel gelatin-chitosan sponge scaffold was designed and studied. The effect of chitosan and gelatin ratio on the morphology, pore size, porosity, water uptake capacity, water retention capacity and the degradation behavior were evaluated. Biocompatibility was investigated by both MTT method and AO/EB staining method. Antibacterial assessment and in vivo pharmacodynamic was also studied to evaluate the potential for wound healing. Results showed the sponge scaffold have uniform porous structure with pore size range between 120 and 140 μm, high porosity (>90%), high water uptake capacity (>1500%), high water retention capacity (>400%), and degradation percent in 28 days between 38.3 and 53.9%. Biocompatibility results showed that the activity of cells could not be affected by the nature of the sponge and it was suitable for cell adhesion and proliferation for 21 days. In vivo evaluation indicated that the sponge scaffold could offer effective support and attachment to cells for skin wound healing. In conclusion, the developed sponge scaffold was a potential skin tissue engineering material with appropriate physical properties and good biocompatibility. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Multi and mixed 3D-printing of graphene-hydroxyapatite hybrid materials for complex tissue engineering.

    Science.gov (United States)

    Jakus, Adam E; Shah, Ramille N

    2017-01-01

    With the emergence of three-dimensional (3D)-printing (3DP) as a vital tool in tissue engineering and medicine, there is an ever growing need to develop new biomaterials that can be 3D-printed and also emulate the compositional, structural, and functional complexities of human tissues and organs. In this work, we probe the 3D-printable biomaterials spectrum by combining two recently established functional 3D-printable particle-laden biomaterial inks: one that contains hydroxyapatite microspheres (hyperelastic bone, HB) and another that contains graphene nanoflakes (3D-graphene, 3DG). We demonstrate that not only can these distinct, osteogenic, and neurogenic inks be co-3D-printed to create complex, multimaterial constructs, but that composite inks of HB and 3DG can also be synthesized. Specifically, the printability, microstructural, mechanical, electrical, and biological properties of a hybrid material comprised of 1:1 HA:graphene by volume is investigated. The resulting HB-3DG hybrid exhibits mixed characteristics of the two distinct systems, while maintaining 3D-printability, electrical conductivity, and flexibility. In vitro assessment of HB-3DG using mesenchymal stem cells demonstrates the hybrid material supports cell viability and proliferation, as well as significantly upregulates both osteogenic and neurogenic gene expression over 14 days. This work ultimately demonstrates a significant step forward towards being able to 3D-print graded, multicompositional, and multifunctional constructs from hybrid inks for complex composite tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 274-283, 2017. © 2016 Wiley Periodicals, Inc.

  13. Effect of crystallinity and plasticizer on mechanical properties and tissue integration of starch-based materials from two botanical origins.

    Science.gov (United States)

    Velasquez, Diego; Pavon-Djavid, Graciela; Chaunier, Laurent; Meddahi-Pellé, Anne; Lourdin, Denis

    2015-06-25

    The application of starch-based materials for biomedical purposes has attracted significant interest due to their biocompatibility. The physical properties and crystal structure of materials based on potato starch (PS) and amylomaize starch (AMS) were studied under physiological conditions. PS plasticized with 20% glycerol presented the best mechanical properties with an elastic modulus of 1.6MPa and a weak swelling, remaining stable for 30 days. The in vitro cell viability of 3T3 cells after contact with extracts from PS and AMS with 20% glycerol is 72% and 80%, respectively. PS presented good tissue integration and no significant inflammation or foreign body response after 30 days intra-muscular implantation in a rat model, contrary to AMS. It was shown that glycerol plasticization favors a fast B-type crystallization of PS materials, enhancing their mechanical strength and durability, and making them a good candidate for bioresorbable and biocompatible materials for implantable medical devices. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Chemical pollutants in field-collected canvasback tissues, eggs, and food materials

    Science.gov (United States)

    White, D.H.; Dieter, M.P.; Stendell, R.C.

    1976-01-01

    In 1972 studies began on the levels of environmental pollutants in canvasback tissues, eggs, and food items. The purpose of the studies were to determine if the levels of toxic chemicals found in canvasbacks were of the magnitude to cause problems affecting reproduction and survival. Overall, levels of organochlorine pesticides and PCB's were low in canvasbacks and their eggs. Some individual birds, however, laid eggs with elevated residues of DDE (12.1 ppm) or PCB's (28.6 ppm). There was no significant difference between eggshell thicknesses of 1972-73 and pre-1946 collections. About 12% of the canvasbacks analyzed had elevated levels of blood lead with reduced ALAD enzyme activity. Adult canvasbacks collected from the Chesapeake Bay in 1975 had moderate to high levels of cadmium in their kidneys. Cadmium, in excessive amounts is very toxic and can curtail spermatogenesis in male birds. Although no single toxic chemical found in wild canvasbacks appears to be a major factor in population declines, the cumulative effects of sublethal levels of all the pollutants may render birds susceptible to disease, hunting pressure or predation.

  15. Vascular Tissue Engineering: Effects of Integrating Collagen into a PCL Based Nanofiber Material

    Directory of Open Access Journals (Sweden)

    Ulf Bertram

    2017-01-01

    Full Text Available The engineering of vascular grafts is a growing field in regenerative medicine. Although numerous attempts have been made, the current vascular grafts made of polyurethane (PU, Dacron®, or Teflon® still display unsatisfying results. Electrospinning of biopolymers and native proteins has been in the focus of research to imitate the extracellular matrix (ECM of vessels to produce a small caliber, off-the-shelf tissue engineered vascular graft (TEVG as a substitute for poorly performing PU, Dacron, or Teflon prostheses. Blended poly-ε-caprolactone (PCL/collagen grafts have shown promising results regarding biomechanical and cell supporting features. In order to find a suitable PCL/collagen blend, we fabricated plane electrospun PCL scaffolds using various collagen type I concentrations ranging from 5% to 75%. We analyzed biocompatibility and morphological aspects in vitro. Our results show beneficial features of collagen I integration regarding cell viability and functionality, but also adverse effects like the loss of a confluent monolayer at high concentrations of collagen. Furthermore, electrospun PCL scaffolds containing 25% collagen I seem to be ideal for engineering vascular grafts.

  16. The equivalence theorem

    International Nuclear Information System (INIS)

    Veltman, H.

    1990-01-01

    The equivalence theorem states that, at an energy E much larger than the vector-boson mass M, the leading order of the amplitude with longitudinally polarized vector bosons on mass shell is given by the amplitude in which these vector bosons are replaced by the corresponding Higgs ghosts. We prove the equivalence theorem and show its validity in every order in perturbation theory. We first derive the renormalized Ward identities by using the diagrammatic method. Only the Feynman-- 't Hooft gauge is discussed. The last step of the proof includes the power-counting method evaluated in the large-Higgs-boson-mass limit, needed to estimate the leading energy behavior of the amplitudes involved. We derive expressions for the amplitudes involving longitudinally polarized vector bosons for all orders in perturbation theory. The fermion mass has not been neglected and everything is evaluated in the region m f ∼M much-lt E much-lt m Higgs

  17. Development of multisubstituted hydroxyapatite nanopowders as biomedical materials for bone tissue engineering applications.

    Science.gov (United States)

    Baba Ismail, Yanny M; Wimpenny, Ian; Bretcanu, Oana; Dalgarno, Kenneth; El Haj, Alicia J

    2017-06-01

    Ionic substitutions have been proposed as a tool to control the functional behavior of synthetic hydroxyapatite (HA), particularly for Bone Tissue Engineering applications. The effect of simultaneous substitution of different levels of carbonate (CO 3 ) and silicon (Si) ions in the HA lattice was investigated. Furthermore, human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured on multi-substituted HA (SiCHA) to determine if biomimetic chemical compositions were osteoconductive. Of the four different compositions investigates, SiCHA-1 (0.58 wt % Si) and SiCHA-2 (0.45 wt % Si) showed missing bands for CO 3 and Si using FTIR analysis, indicating competition for occupation of the phosphate site in the HA lattice; 500°C was considered the most favorable calcination temperature as: (i) the powders produced possessed a similar amount of CO 3 (2-8 wt %) and Si (<1.0 wt %) as present in native bone; and (ii) there was a minimal loss of CO 3 and Si from the HA structure to the surroundings during calcination. Higher Si content in SiCHA-1 led to lower cell viability and at most hindered proliferation, but no toxicity effect occurred. While, lower Si content in SiCHA-2 showed the highest ALP/DNA ratio after 21 days culture with hMSCs, indicating that the powder may stimulate osteogenic behavior to a greater extent than other powders. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1775-1785, 2017. © 2017 Wiley Periodicals, Inc.

  18. Effect of chemical composition on corneal tissue response to photopolymerized materials comprising 2-hydroxyethyl methacrylate and acrylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Jui-Yang, E-mail: jylai@mail.cgu.edu.tw

    2014-01-01

    The purpose of this work was to investigate the relationship between the feed composition of 2-hydroxyethyl methacrylate (HEMA)/acrylic acid (AAc) and hydrogel material compatibility towards ocular anterior segment tissues, particularly the corneal endothelium. The monomer solutions of HEMA and AAc were mixed at varying volume ratios of 92:0, 87:5, 82:10, 77:15, and 72:20, and were subjected to UV irradiation. Then, the 7-mm-diameter membrane implants made from photopolymerized materials were placed into the ocular anterior chamber for 4 days and assessed by biomicroscopic examinations, corneal thickness measurements, and quantitative real-time reverse transcription polymerase chain reaction analyses. The poly(HEMA-co-AAc) implants prepared from the solution mixture containing 0–10 vol.% AAc displayed good biocompatibility. However, with increasing volume ratio of AAc and HEMA from 15:77 to 20:72, the enhanced inflammatory response, decreased endothelial cell density, and increased ocular score and corneal thickness were observed, probably due to the influence of surface charge of copolymer membranes. On the other hand, the ionic pump function of corneal endothelium exposed to photopolymerized membranes was examined by analyzing the Na{sup +},K{sup +}-ATPase alpha 1 subunit (ATP1A1) expression level. The presence of the implants having higher amount of AAc incorporated in the copolymers (i.e., 15.1 to 24.7 μmol) and zeta potential (i.e., -38.6 to − 56.5 mV) may lead to abnormal transmembrane transport. It is concluded that the chemical composition of HEMA/AAc has an important influence on the corneal tissue responses to polymeric biomaterials. - Highlights: • We examine the corneal tissue responses to photopolymerized biomaterials. • Carboxyl groups in copolymers increased with increasing volume ratio of AAc/HEMA. • 15–20 vol.% AAc raised ocular score and caused corneal endothelial loss and edema. • High anionic charge density stimulated inflammation

  19. Infections in the tissue material and their impact on the loss of transplants in the Laboratory of in vitro Cell and Tissue Culture with Tissue Bank in the years 2011-2015.

    Science.gov (United States)

    Kitala, D; Klama-Baryła, A; Kawecki, M; Kraut, M; Łabuś, W; Glik, J; Ples, M; Tomanek, E; Nowak, M

    2017-03-01

    Radiation sterilization eliminates microbiological infections but causes the degradation of the cell factor. The negative result of microbiological examination for tissue transplants is one of the conditions for approval for distribution in patients. The study attempts to verify impact of the presence of microbes onto material for transplant loss. In the 2011-2015 period, we analyzed 293 donors of skin and amnion. Microbiological sampling was performed. The total of 21 strains of bacteria, molds and fungi was identified in collected tissue. The widest spectrum of strains was found in skin (17), followed by amnia (8). The total number of positive findings was 147 and was again highest in skin (129), while the number of positive findings in amnia was 18 only. The general percentage of fungal infections was very low. The presence of fungal strains was only observed in allogeneic skin (2%). Large number of microorganisms isolated from the skin before sterilization was observed, so it seems impossible to use allogeneic intravital skin. However, the intravital application of allogeneic amnion obtained from cesarean section remains to be considered.

  20. Regeneration of skull bones in adult rabbits after implantation of commercial osteoinductive materials and transplantation of a tissue-engineering construct.

    Science.gov (United States)

    Volkov, A V; Alekseeva, I S; Kulakov, A A; Gol'dshtein, D V; Shustrov, S A; Shuraev, A I; Arutyunyan, I V; Bukharova, T B; Rzhaninova, A A; Bol'shakova, G B; Grigor'yan, A S

    2010-10-01

    We performed a comparative study of reparative osteogenesis in rabbits with experimental critical defects of the parietal bones after implantation of commercial osteoinductive materials "Biomatrix", "Osteomatrix", "BioOss" in combination with platelet-rich plasma and transplantation of a tissue-engineering construct on the basis of autogenic multipotent stromal cells from the adipose tissue predifferentiated in osteogenic direction. It was found that experimental reparative osteogenesis is insufficiently stimulated by implantation materials and full-thickness trepanation holes were not completely closed. After transplantation of the studied tissue-engineering construct, the defect was filled with full-length bone regenerate (in the center of the regenerate and from the maternal bone) in contrast to control and reference groups, where the bone tissue was formed only on the side of the maternal bone. On day 120 after transplantation of the tissue-engineering construct, the percent of newly-formed bone tissue in the regenerate was 24% (the total percent of bone tissue in the regenerate was 39%), which attested to active incomplete regenerative process in contrast to control and reference groups. Thus, the study demonstrated effective regeneration of the critical defects of the parietal bones in rabbits 120 days after transplantation of the tissue-engineering construct in contrast to commercial osteoplastic materials for directed bone regeneration.

  1. Multifunctional zirconium oxide doped chitosan based hybrid nanocomposites as bone tissue engineering materials.

    Science.gov (United States)

    Bhowmick, Arundhati; Jana, Piyali; Pramanik, Nilkamal; Mitra, Tapas; Banerjee, Sovan Lal; Gnanamani, Arumugam; Das, Manas; Kundu, Patit Paban

    2016-10-20

    This paper reports the development of multifunctional zirconium oxide (ZrO2) doped nancomposites having chitosan (CTS), organically modified montmorillonite (OMMT) and nano-hydroxyapatite (HAP). Formation of these nanocomposites was confirmed by various characterization techniques such as Fourier transform infrared spectroscopy and powder X-ray diffraction. Scanning electron microscopy images revealed uniform distribution of OMMT and nano-HAP-ZrO2 into CTS matrix. Powder XRD study and TEM study revealed that OMMT has partially exfoliated into the polymer matrix. Enhanced mechanical properties in comparison to the reported literature were obtained after the addition of ZrO2 nanoparticle into the nanocomposites. In rheological measurements, CMZH I-III exhibited greater storage modulus (G') than loss modulus (G″). TGA results showed that these nanocomposites are thermally more stable compare to pure CTS film. Strong antibacterial zone of inhibition and the lowest minimum inhibition concentration (MIC) value of these nanocomposites against bacterial strains proved that these materials have the ability to prevent bacterial infection in orthopedic implants. Compatibility of these nanocomposites with pH and blood of human body was established. It was observed from the swelling study that the swelling percentage was increased with decreasing the hydrophobic OMMT content. Human osteoblastic MG-63 cell proliferations were observed on the nanocomposites and cytocompatibility of these nanocomposites was also established. Moreover, addition of 5wt% OMMT and 5wt% nano-HAP-ZrO2 into 90wt% CTS matrix provides maximum tensile strength, storage modulus, aqueous swelling and cytocompatibility along with strong antibacterial effect, pH and erythrocyte compatibility. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Revolutionizing orthopaedic biomaterials: The potential of biodegradable and bioresorbable magnesium-based materials for functional tissue engineering.

    Science.gov (United States)

    Farraro, Kathryn F; Kim, Kwang E; Woo, Savio L-Y; Flowers, Jonquil R; McCullough, Matthew B

    2014-06-27

    In recent years, there has been a surge of interest in magnesium (Mg) and its alloys as biomaterials for orthopaedic applications, as they possess desirable mechanical properties, good biocompatibility, and biodegradability. Also shown to be osteoinductive, Mg-based materials could be particularly advantageous in functional tissue engineering to improve healing and serve as scaffolds for delivery of drugs, cells, and cytokines. In this paper, we will present two examples of Mg-based orthopaedic devices: an interference screw to accelerate ACL graft healing and a ring to aid in the healing of an injured ACL. In vitro tests using a robotic/UFS testing system showed that both devices could restore function of the goat stifle joint. Under a 67-N anterior tibial load, both the ACL graft fixed with the Mg-based interference screw and the Mg-based ring-repaired ACL could restore anterior tibial translation (ATT) to within 2mm and 5mm, respectively, of the intact joint at 30°, 60°, and 90° of flexion. In-situ forces in the replacement graft and Mg-based ring-repaired ACL were also similar to those of the intact ACL. Further, early in vivo data using the Mg-based interference screw showed that after 12 weeks, it was non-toxic and the joint stability and graft function reached similar levels as published data. Following these positive results, we will move forward in incorporating bioactive molecules and ECM bioscaffolds to these Mg-based biomaterials to test their potential for functional tissue engineering of musculoskeletal and other tissues. © 2013 Published by Elsevier Ltd.

  3. Equivalence, commensurability, value

    DEFF Research Database (Denmark)

    Albertsen, Niels

    2017-01-01

    Deriving value in Capital Marx uses three commensurability arguments (CA1-3). CA1 establishes equivalence in exchange as exchangeability with the same third commodity. CA2 establishes value as common denominator in commodities: embodied abstract labour. CA3 establishes value substance...... as commonality of labour: physiological labour. Tensions between these logics have permeated Marxist interpretations of value. Some have supported value as embodied labour (CA2, 3), others a monetary theory of value and value as ‘pure’ societal abstraction (ultimately CA1). They all are grounded in Marx....

  4. Instrument for determining the complex shear modulus of soft-tissue-like materials from 10 to 300 Hz

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, E L; Frank, G R; Hobson, M A; Hall, T J; Jiang, J; Stiles, T A [Medical Physics Department, 1005 Wisconsin, Institute for Medical Research, Madison, WI 53705 (United States); Lin-Gibson, S [Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)], E-mail: elmadsen@wisc.edu

    2008-10-07

    Accurate determination of the complex shear modulus of soft tissues and soft-tissue-like materials in the 10-300 Hz frequency range is very important to researchers in MR elastography and acoustic radiation force impulse (ARFI) imaging. A variety of instruments for making such measurements has been reported, but none of them is easily reproduced, and none have been tested to conform to causality via the Kramers-Kronig (K-K) relations. A promising linear oscillation instrument described in a previous brief report operates between 20 and 160 Hz, but results were not tested for conformity to the K-K relations. We have produced a similar instrument with our own version of the electronic components and have also accounted for instrumental effects on the data reduction, which is not addressed in the previous report. The improved instrument has been shown to conform to an accurate approximation of the K-K relations over the 10-300 Hz range. The K-K approximation is based on the Weichert mechanical circuit model. We also found that the sample thickness must be small enough to obtain agreement with a calibrated commercial rheometer. A complete description of the improved instrument is given, facilitating replication in other labs.

  5. SU-E-T-409: Evaluation of Tissue Composition Effect On Dose Distribution in Radiotherapy with 6 MV Photon Beam of a Medical Linac

    Energy Technology Data Exchange (ETDEWEB)

    Ghorbani, M; Tabatabaei, Z; Noghreiyan, A Vejdani [Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Meigooni, A Soleimani [Comprehensive Cancer Center of Nevada, Las Vegas, NV (United States)

    2015-06-15

    Purpose: The aim of this study is to evaluate soft tissue composition effect on dose distribution for various soft tissues and various depths in radiotherapy with 6 MV photon beam of a medical linac. Methods: A phantom and Siemens Primus linear accelerator were simulated using MCNPX Monte Carlo code. In a homogeneous cubic phantom, six types of soft tissue and three types of tissue-equivalent materials were defined separately. The soft tissues were muscle (skeletal), adipose tissue, blood (whole), breast tissue, soft tissue (9-component) and soft tissue (4-component). The tissue-equivalent materials included: water, A-150 tissue-equivalent plastic and perspex. Photon dose relative to dose in 9-component soft tissue at various depths on the beam’s central axis was determined for the 6 MV photon beam. The relative dose was also calculated and compared for various MCNPX tallies including,F8, F6 and,F4. Results: The results of the relative photon dose in various materials relative to dose in 9-component soft tissue and using different tallies are reported in the form of tabulated data. Minor differences between dose distributions in various soft tissues and tissue-equivalent materials were observed. The results from F6 and F4 were practically the same but different with,F8 tally. Conclusion: Based on the calculations performed, the differences in dose distributions in various soft tissues and tissue-equivalent materials are minor but they could be corrected in radiotherapy calculations to upgrade the accuracy of the dosimetric calculations.

  6. Periapical tissue response after use of intermediate restorative material, gutta-percha, reinforced zinc oxide cement, and mineral trioxide aggregate as retrograde root-end filling materials: a histologic study in dogs.

    Science.gov (United States)

    Wälivaara, Dan-Åke; Abrahamsson, Peter; Isaksson, Sten; Salata, Luiz Antonio; Sennerby, Lars; Dahlin, Christer

    2012-09-01

    To investigate the periapical tissue response of 4 different retrograde root-filling materials, ie, intermediate restorative material, thermoplasticized gutta-percha, reinforced zinc oxide cement (Super-EBA), and mineral trioxide aggregate (MTA), in conjunction with an ultrasonic root-end preparation technique in an animal model. Vital roots of the third and fourth right mandibular premolars in 6 healthy mongrel dogs were apicectomized and sealed with 1 of the materials using a standardized surgical procedure. After 120 days, the animals were sacrificed and the specimens were analyzed radiologically, histologically, and scanning electron microscopically. The Fisher exact test was performed on the 2 outcome values. Twenty-three sections were analyzed histologically. Evaluation showed better re-establishment of the periapical tissues and generally lower inflammatory infiltration in the sections from teeth treated with the intermediate restorative material and the MTA. New root cement on the resected dentin surfaces was seen on all sections regardless of the used material. New hard tissue formation, directly on the surface of the material, was seen only in the MTA sections. There was no statistical difference in outcome among the tested materials. The results from this dog model favor the intermediate restorative material and MTA as retrograde fillings when evaluating the bone defect regeneration. MTA has the most favorable periapical tissue response when comparing the biocompatibility of the materials tested. Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  7. Mechanical, Biological and Electrochemical Investigations of Advanced Micro/Nano Materials for Tissue Engineering and Energy Storage

    Science.gov (United States)

    Pu, Juan

    Various micro/nano materials have been extensively studied for applications in tissue engineering and energy storage. Tissue engineering seeks to repair or replace damaged tissue by integrating approaches from cellular/molecular biology and material chemistry/engineering. A major challenge is the consistent design of three-dimensional (3D) scaffolds that mimic the structure and biological functions of extracellular matrix (ECM), guide cell migration, provide mechanical support, and regulate cell activity. Electrospun micro/nanofibers have been investigated as promising tissue engineering scaffolds because they resemble native ECM and possess tunable surface morphologies. Supercapacitors, one of the energy storage devices, bridge the performance gap between rechargeable batteries and conventional capacitors. Active electrode materials of supercapacitors must possess high specific surface area, high conductivity, and good electrochemical properties. Carbon-based micro/nano-particles, such as graphene, activated carbon (AC), and carbon nanotubes, are commonly used as active electrode materials for storing charge in supercapacitors by the electrical double layer mechanism due to their high specific surface area and excellent conductivity. In this thesis, the mechanical properties of electrospun bilayer microfibrous membranes were investigated for potential applications in tissue engineering. Bilayer microfibrous membranes of poly(l-lactic acid) (PLLA) were fabricated by electrospinning using a parallel-disk mandrel configuration, which resulted in the sequential deposition of a layer with aligned fibers (AFL) across the two parallel disks and a layer with random fibers (RFL), both deposited by a single process step. The membrane structure and fiber alignment were characterized by scanning electron microscopy and two-dimensional fast Fourier transform. Because of the intricacies of the generated electric field, the bilayer membranes exhibited higher porosity than the

  8. Establishing Substantial Equivalence: Proteomics

    Science.gov (United States)

    Lovegrove, Alison; Salt, Louise; Shewry, Peter R.

    Wheat is a major crop in world agriculture and is consumed after processing into a range of food products. It is therefore of great importance to determine the consequences (intended and unintended) of transgenesis in wheat and whether genetically modified lines are substantially equivalent to those produced by conventional plant breeding. Proteomic analysis is one of several approaches which can be used to address these questions. Two-dimensional PAGE (2D PAGE) remains the most widely available method for proteomic analysis, but is notoriously difficult to reproduce between laboratories. We therefore describe methods which have been developed as standard operating procedures in our laboratory to ensure the reproducibility of proteomic analyses of wheat using 2D PAGE analysis of grain proteins.

  9. Quantification of the equivalence principle

    International Nuclear Information System (INIS)

    Epstein, K.J.

    1978-01-01

    Quantitative relationships illustrate Einstein's equivalence principle, relating it to Newton's ''fictitious'' forces arising from the use of noninertial frames, and to the form of the relativistic time dilatation in local Lorentz frames. The equivalence principle can be interpreted as the equivalence of general covariance to local Lorentz covariance, in a manner which is characteristic of Riemannian and pseudo-Riemannian geometries

  10. Alteration of the bone tissue material properties in type 1 diabetes mellitus: A Fourier transform infrared microspectroscopy study.

    Science.gov (United States)

    Mieczkowska, Aleksandra; Mansur, Sity Aishah; Irwin, Nigel; Flatt, Peter R; Chappard, Daniel; Mabilleau, Guillaume

    2015-07-01

    Type 1 diabetes mellitus (T1DM) is a severe disorder characterized by hyperglycemia and hypoinsulinemia. A higher occurrence of bone fractures has been reported in T1DM, and although bone mineral density is reduced in this disorder, it is also thought that bone quality may be altered in this chronic pathology. Vibrational microscopies such as Fourier transform infrared microspectroscopy (FTIRM) represent an interesting approach to study bone quality as they allow investigation of the collagen and mineral compartment of the extracellular matrix in a specific bone location. However, as spectral feature arising from the mineral may overlap with those of the organic component, the demineralization of bone sections should be performed for a full investigation of the organic matrix. The aims of the present study were to (i) develop a new approach, based on the demineralization of thin bone tissue section to allow a better characterization of the bone organic component by FTIRM, (ii) to validate collagen glycation and collagen integrity in bone tissue and (iii) to better understand what alterations of tissue material properties in newly forming bone occur in T1DM. The streptozotocin-injected mouse (150 mg/kg body weight, injected at 8 weeks old) was used as T1DM model. Animals were randomly allocated to control (n = 8) or diabetic (n = 10) groups and were sacrificed 4 weeks post-STZ injection. Bones were collected at necropsy, embedded in polymethylmethacrylate and sectioned prior to examination by FTIRM. FTIRM collagen parameters were collagen maturity (area ratio between 1660 and 1690 cm(-1) subbands), collagen glycation (area ratio between the 1032 cm(-1) subband and amide I) and collagen integrity (area ratio between the 1338 cm(-1) subband and amide II). No significant differences in the mineral compartment of the bone matrix could be observed between controls and STZ-injected animals. On the other hand, as compared with controls, STZ-injected animals presented with

  11. Mussel tissue (T-31) - A new analytical quality control material for the determination of mercury and arsenic in mussels

    Energy Technology Data Exchange (ETDEWEB)

    Gawlik, B. [Joint Research Centre Ispra, Ispra, Varese (Italy). Environment Institute]|[Muenchen, Technische Universitaet (Germany). Lehrstuhl fuer Oekologische Chemie und Umweltanalytik; Druges, M. [Thomson Microelectronics, Crolles (France); Bianchi, M.; Muntau, H. [Joint Research Centre Ispra, Ispra, Varese (Italy). Environment Institute; Bortoli, A. [ULSS 12, Venice (Italy). Presidio Multizonale di Prevenzione; Kettrup, A. [Muenchen, Technische Universitaet (Germany). Lehrstuhl fur Oekologische Chemie und Umweltanalytik]|[GSF Forschungszentrum fuer Umwelt und Gesundheit, Oberschleissheim (Germany). Inst. fuer Oekologische Chemie

    1998-05-01

    The use of filter-feeding molluscs for the monitoring of selected contaminant levels in the marine environment is well-known in the scientific community. In the order to assure the quality of those analysis and to prepare laboratories for accreditation procedures certified reference materials and proficiency testing campaigns were introduced. However, there is still a need for the introduction of suitable analytical quality materials of high quality which can be used on a daily basis. This paper therefore describes the preparation of a mussel tissue material for the internal quality control of Hg and As analysis in bivalves, as well as the principle of preparation and the analytical characterisation of such a material. The total concentration for arsenic (8.98 {+-} 0.67 {mu}g/g) and mercury (0.169 {+-} 0.005 {mu}g/g) was determined by the use of different techniques. Additionally, indicative values for major constituents (C, H, N, Na, Cl, P, S, K, Mg, Ca, Si, Fe, Al, Br, Zn, Sr) and some trace elements (Cu, Cd, Pb, Ni) were measured. [Italiano] L`uso di molluschi filtratori nel monitoraggio dei livelli di contaminazione in ambiente marino e` ben noto in ambito scientifico. Per assicurare la qualita` di queste analisi e preparare i laboratori alle procedure di accreditamento e stato introdotto l`uso di materiali di riferimento certificati accoppiato alla partecipazione a campagne di controllo interlaboratoriale. Attualmente non sono ancora disponibili materiali di riferimento appropriati e di alta qualita`, che possano essere usati su base quotidiana. Questo lavoro descrive la preparazione di un materiale di riferimanto di cozze da usare come mezzo di controllo di qualita` interna e i principi di preparazione e di caratterizzazione analitica di un materiale di questo tipo. La concentrazione totale dell`arsenico (8.98 {+-} 0.67 {mu}g/g) e del mercurio (0.169 {+-} 0.005 {mu}g/g) sono state determinati mediante l`uso di differenti tecniche. Sono stati in oltre misurati

  12. New recommendations for dose equivalent

    International Nuclear Information System (INIS)

    Bengtsson, G.

    1985-01-01

    In its report 39, the International Commission on Radiation Units and Measurements (ICRU), has defined four new quantities for the determination of dose equivalents from external sources: the ambient dose equivalent, the directional dose equivalent, the individual dose equivalent, penetrating and the individual dose equivalent, superficial. The rationale behind these concepts and their practical application are discussed. Reference is made to numerical values of these quantities which will be the subject of a coming publication from the International Commission on Radiological Protection, ICRP. (Author)

  13. System equivalent model mixing

    Science.gov (United States)

    Klaassen, Steven W. B.; van der Seijs, Maarten V.; de Klerk, Dennis

    2018-05-01

    This paper introduces SEMM: a method based on Frequency Based Substructuring (FBS) techniques that enables the construction of hybrid dynamic models. With System Equivalent Model Mixing (SEMM) frequency based models, either of numerical or experimental nature, can be mixed to form a hybrid model. This model follows the dynamic behaviour of a predefined weighted master model. A large variety of applications can be thought of, such as the DoF-space expansion of relatively small experimental models using numerical models, or the blending of different models in the frequency spectrum. SEMM is outlined, both mathematically and conceptually, based on a notation commonly used in FBS. A critical physical interpretation of the theory is provided next, along with a comparison to similar techniques; namely DoF expansion techniques. SEMM's concept is further illustrated by means of a numerical example. It will become apparent that the basic method of SEMM has some shortcomings which warrant a few extensions to the method. One of the main applications is tested in a practical case, performed on a validated benchmark structure; it will emphasize the practicality of the method.

  14. Measurements of mechanical anisotropy in brain tissue and implications for transversely isotropic material models of white matter

    Science.gov (United States)

    Feng, Yuan; Okamoto, Ruth J.; Namani, Ravi; Genin, Guy M.; Bayly, Philip V.

    2013-01-01

    White matter in the brain is structurally anisotropic, consisting largely of bundles of aligned, myelin-sheathed axonal fibers. White matter is believed to be mechanically anisotropic as well. Specifically, transverse isotropy is expected locally, with the plane of isotropy normal to the local mean fiber direction. Suitable material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy–Green strain tensor to account for the effects of relatively stiff fibers. The pseudo-invariant I4 is the square of the stretch ratio in the fiber direction; I5 contains contributions of shear strain in planes parallel to the fiber axis. Most, if not all, published models of white matter depend on I4 but not on I5. Here, we explore the small strain limits of these models in the context of experimental measurements that probe these dependencies. Models in which strain energy depends on I4 but not I5 can capture differences in Young’s (tensile) moduli, but will not exhibit differences in shear moduli for loading parallel and normal to the mean direction of axons. We show experimentally, using a combination of shear and asymmetric indentation tests, that white matter does exhibit such differences in both tensile and shear moduli. Indentation tests were interpreted through inverse fitting of finite element models in the limit of small strains. Results highlight that: (1) hyperelastic models of transversely isotropic tissues such as white matter should include contributions of both the I4 and I5 strain pseudo-invariants; and (2) behavior in the small strain regime can usefully guide the choice and initial parameterization of more general material models of white matter. PMID:23680651

  15. Construction of a preclinical multimodality phantom using tissue-mimicking materials for quality assurance in tumor size measurement.

    Science.gov (United States)

    Lee, Yongsook C; Fullerton, Gary D; Goins, Beth A

    2013-07-29

    World Health Organization (WHO) and the Response Evaluation Criteria in Solid Tumors (RECIST) working groups advocated standardized criteria for radiologic assessment of solid tumors in response to anti-tumor drug therapy in the 1980s and 1990s, respectively. WHO criteria measure solid tumors in two-dimensions, whereas RECIST measurements use only one-dimension which is considered to be more reproducible (1, 2, 3,4,5). These criteria have been widely used as the only imaging biomarker approved by the United States Food and Drug Administration (FDA) (6). In order to measure tumor response to anti-tumor drugs on images with accuracy, therefore, a robust quality assurance (QA) procedures and corresponding QA phantom are needed. To address this need, the authors constructed a preclinical multimodality (for ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI)) phantom using tissue-mimicking (TM) materials based on the limited number of target lesions required by RECIST by revising a Gammex US commercial phantom (7). The Appendix in Lee et al. demonstrates the procedures of phantom fabrication (7). In this article, all protocols are introduced in a step-by-step fashion beginning with procedures for preparing the silicone molds for casting tumor-simulating test objects in the phantom, followed by preparation of TM materials for multimodality imaging, and finally construction of the preclinical multimodality QA phantom. The primary purpose of this paper is to provide the protocols to allow anyone interested in independently constructing a phantom for their own projects. QA procedures for tumor size measurement, and RECIST, WHO and volume measurement results of test objects made at multiple institutions using this QA phantom are shown in detail in Lee et al. (8).

  16. The equivalence principle

    International Nuclear Information System (INIS)

    Smorodinskij, Ya.A.

    1980-01-01

    The prerelativistic history of the equivalence principle (EP) is presented briefly. Its role in history of the general relativity theory (G.R.T.) discovery is elucidated. A modern idea states that the ratio of inert and gravitational masses does not differ from 1 at least up to the 12 sign after comma. Attention is paid to the difference of the gravitational field from electromagnetic one. The difference is as follows, the energy of the gravitational field distributed in space is the source of the field. These fields always interact at superposition. Electromagnetic fields from different sources are put together. On the basis of EP it is established the Sun field interact with the Earth gravitational energy in the same way as with any other one. The latter proves the existence of gravitation of the very gravitational field to a heavy body. A problem on gyroscope movement in the Earth gravitational field is presented as a paradox. The calculation has shown that gyroscope at satellite makes a positive precession, and its axis turns in an angle equal to α during a turn of the satellite round the Earth, but because of the space curvature - into the angle two times larger than α. A resulting turn is equal to 3α. It is shown on the EP basis that the polarization plane in any coordinate system does not turn when the ray of light passes in the gravitational field. Together with the historical value of EP noted is the necessity to take into account the requirements claimed by the EP at description of the physical world

  17. Cobalt deposition in mineralized bone tissue after metal-on-metal hip resurfacing: Quantitative μ-X-ray-fluorescence analysis of implant material incorporation in periprosthetic tissue.

    Science.gov (United States)

    Hahn, Michael; Busse, Björn; Procop, Mathias; Zustin, Jozef; Amling, Michael; Katzer, Alexander

    2017-10-01

    Most resurfacing systems are manufactured from cobalt-chromium alloys with metal-on-metal (MoM) bearing couples. Because the quantity of particulate metal and corrosion products which can be released into the periprosthetic milieu is greater in MoM bearings than in metal-on-polyethylene (MoP) bearings, it is hypothesized that the quantity and distribution of debris released by the MoM components induce a compositional change in the periprosthetic bone. To determine the validity of this claim, nondestructive µ-X-ray fluorescence analysis was carried out on undecalcified histological samples from 13 femoral heads which had undergone surface replacement. These samples were extracted from the patients after gradient time points due to required revision surgery. Samples from nonintervened femoral heads as well as from a MoP resurfaced implant served as controls. Light microscopy and µ-X-ray fluorescence analyses revealed that cobalt debris was found not only in the soft tissue around the prosthesis and the bone marrow, but also in the mineralized bone tissue. Mineralized bone exposed to surface replacements showed significant increases in cobalt concentrations in comparison with control specimens without an implant. A maximum cobalt concentration in mineralized hard tissue of up to 380 ppm was detected as early as 2 years after implantation. Values of this magnitude are not found in implants with a MoP surface bearing until a lifetime of more than 20 years. This study demonstrates that hip resurfacing implants with MoM bearings present a potential long-term health risk due to rapid cobalt ion accumulation in periprosthetic hard tissue. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1855-1862, 2017. © 2016 Wiley Periodicals, Inc.

  18. Electrothermal Equivalent Three-Dimensional Finite-Element Model of a Single Neuron.

    Science.gov (United States)

    Cinelli, Ilaria; Destrade, Michel; Duffy, Maeve; McHugh, Peter

    2018-06-01

    We propose a novel approach for modelling the interdependence of electrical and mechanical phenomena in nervous cells, by using electrothermal equivalences in finite element (FE) analysis so that existing thermomechanical tools can be applied. First, the equivalence between electrical and thermal properties of the nerve materials is established, and results of a pure heat conduction analysis performed in Abaqus CAE Software 6.13-3 are validated with analytical solutions for a range of steady and transient conditions. This validation includes the definition of equivalent active membrane properties that enable prediction of the action potential. Then, as a step toward fully coupled models, electromechanical coupling is implemented through the definition of equivalent piezoelectric properties of the nerve membrane using the thermal expansion coefficient, enabling prediction of the mechanical response of the nerve to the action potential. Results of the coupled electromechanical model are validated with previously published experimental results of deformation for squid giant axon, crab nerve fibre, and garfish olfactory nerve fibre. A simplified coupled electromechanical modelling approach is established through an electrothermal equivalent FE model of a nervous cell for biomedical applications. One of the key findings is the mechanical characterization of the neural activity in a coupled electromechanical domain, which provides insights into the electromechanical behaviour of nervous cells, such as thinning of the membrane. This is a first step toward modelling three-dimensional electromechanical alteration induced by trauma at nerve bundle, tissue, and organ levels.

  19. 针对组织工程多孔生物陶瓷的组织学技术优化探讨%Technique improvement of hard tissue slicing of bioceramic scaffold materials applied in bone tissue engineering

    Institute of Scientific and Technical Information of China (English)

    李林; 智伟; 桑力; 张成栋; 李金雨; 张聪; 娄延举; 夏天; 翁杰

    2013-01-01

    目的 改进硬组织切片技术以适应生物陶瓷材料在骨组织工程中的研究.方法 探索硬组织切片的厚度、漂片温度、裱片方法、烤片温度和时间的最佳组合,针对阳离子防脱载玻片的使用条件进行反复比较,通过改进操作流程中的关键技术和需避免的问题,摸索出阳离子载玻片在硬组织切片裱片中的最佳应用条件,克服了硬组织切片制作技术中标本易破碎、切片易脱落及染色时染料容易吸附的缺点.结果 通过技术探索与改进,生物陶瓷支架材料体内植入后的类骨修复体标本的硬组织切片能保持其杂化后的组织结构与比较完整的材料结构,可进行Masson三色染色、苏木精-伊红(HE)及甲苯胺蓝染色.染色后镜下观察显示支架内杂化生长的组织结构完整、细胞形态清晰、切片质量好、生物陶瓷支架脱片少.荧光显微镜可观察到类骨修复体钙沉积现象完整.结论 改善了传统硬组织切片技术处理生物陶瓷材料时易于破坏组织-材料结构的缺点.改进的硬组织切片技术适应生物陶瓷材料在骨组织工程领域研究.%Objective Purpose To improve the hard tissue slicing technology to adapt to the study of the bioceramic materials in bone tissue engineering.Methods Purpose To improve the hard tissue slicing technology to adapt to the study of the bioceramic materials in bone tissue engineering.Results The improved techniques in hard tissue slicing could keep the morphosis and structure of hybrid tissues,and easily stain with Masson,HE and toluidine blue.The stained hard tissue slicing had an intact tissue structure,clear cell form,good slicing quality,little shedding.Fluorescence microscope showed an intact calcium deposition of homologous bone restoration.Conclusion The method overcome the shortcomings of easy to destroy the tissue-material structure happened in the traditional hard tissue slicing of bioceramic materials

  20. Logically automorphically equivalent knowledge bases

    OpenAIRE

    Aladova, Elena; Plotkin, Tatjana

    2017-01-01

    Knowledge bases theory provide an important example of the field where applications of universal algebra and algebraic logic look very natural, and their interaction with practical problems arising in computer science might be very productive. In this paper we study the equivalence problem for knowledge bases. Our interest is to find out how the informational equivalence is related to the logical description of knowledge. Studying various equivalences of knowledge bases allows us to compare d...

  1. Testing statistical hypotheses of equivalence

    CERN Document Server

    Wellek, Stefan

    2010-01-01

    Equivalence testing has grown significantly in importance over the last two decades, especially as its relevance to a variety of applications has become understood. Yet published work on the general methodology remains scattered in specialists' journals, and for the most part, it focuses on the relatively narrow topic of bioequivalence assessment.With a far broader perspective, Testing Statistical Hypotheses of Equivalence provides the first comprehensive treatment of statistical equivalence testing. The author addresses a spectrum of specific, two-sided equivalence testing problems, from the

  2. Certification of methylmercury in cod fish tissue certified reference material by species-specific isotope dilution mass spectrometric analysis

    Energy Technology Data Exchange (ETDEWEB)

    Inagaki, Kazumi; Kuroiwa, Takayoshi; Narukawa, Tomohiro; Yarita, Takashi; Takatsu, Akiko; Okamoto, Kensaku; Chiba, Koichi [National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Environmental Standard Section, Tsukuba, Ibaraki (Japan)

    2008-07-15

    A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass bottles (10 g each), which were sterilized with {gamma}-ray irradiation. The certification was carried out using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICPMS), where {sup 202}Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods (KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses. In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total mercury was determined by ID-ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was estimated by GC-ICPMS. The certified value given for MeHg is 0.58 {+-} 0.02 mg kg{sup -1} as Hg. (orig.)

  3. Tissue level material composition and mechanical properties in Brtl/+ mouse model of Osteogenesis Imperfecta after sclerostin antibody treatment

    Science.gov (United States)

    Lloyd, William R.; Sinder, Benjamin P.; Salemi, Joseph; Ominsky, Michael S.; Marini, Joan C.; Caird, Michelle S.; Morris, Michael D.; Kozloff, Kenneth M.

    2015-02-01

    Osteogenesis imperfecta (OI) is a genetic disorder resulting in defective collagen or collagen-associated proteins and fragile, brittle bones. To date, therapies to improve OI bone mass, such as bisphosphonates, have increased bone mass in the axial skeleton of OI patients, but have shown limited effects at reducing long bone fragility. Sclerostin antibody (Scl- Ab), currently in clinical trials for osteoporosis, stimulates bone formation and may have the potential to reduce long bone fracture rates in OI patients. Scl-Ab has been investigated as an anabolic therapy for OI in the Brtl/+ mouse model of moderately severe Type IV OI. While Scl-Ab increases long bone mass in the Brtl/+ mouse, it is not known whether material properties and composition changes also occur. Here, we report on the effects of Scl-Ab on wild type and Brtl/+ young (3 week) and adult (6 month) male mice. Scl-Ab was administered over 5 weeks (25mg/kg, 2x/week). Raman microspectroscopy and nanoindentation are used for bone composition and biomechanical bone property measurements in excised bone. Fluorescent labels (calcein and alizarin) at 4 time points over the entire treatment period are used to enable measurements at specific tissue age. Differences between wild type and Brtl/+ groups included variations in the mineral and matrix lattices, particularly the phosphate v1, carbonate v1, and the v(CC) proline and hydroxyproline stretch vibrations. Results of Raman spectroscopy corresponded to nanoindentation findings which indicated that old bone (near midcortex) is stiffer (higher elastic modulus) than new bone. We compare and contrast mineral to matrix and carbonate to phosphate ratios in young and adult mice with and without treatment.

  4. Assessment of stability of trace elements in two natural matrix environmental standard reference materials. NIST-SRM 1547 Peach leaves and NIST-SRM 1566a Oyster Tissue

    International Nuclear Information System (INIS)

    Mackey, E.A.; Spatz, R.O.

    2009-01-01

    The NIST program for environmental Standard Reference Materials (SRM) includes materials covering a range of matrices, mass fraction values and analytes. For many SRMs, mass fraction data are accumulated, incidentally, over time, as these are used routinely for quality assurance purposes. Although these are not formal stability studies, data generated may be useful in assessing stability. To evaluate the potential for assessing material stability from incidental use of SRMs, results of neutron activation analysis performed from 1992 through 2008 were compiled for SRM 1547 Peach Leaves and SRM 1566a Oyster Tissue. Results indicate that incidental use of SRMs yields useful information on SRM stability. (author)

  5. Penelope simulation of electron beams 6 MeV from a linear accelerator for studies in different materials equivalent to human body; Simulacion Penelope de haces de electrones de 6 MeV de un acelerador lineal para estudios en diferentes materiales equivalentes al cuerpo humano

    Energy Technology Data Exchange (ETDEWEB)

    Apaza V, D.; Cardena R, R.; Cayllahua Q, F.; Vega R, J. [Universidad Nacional de San Agustin de Arequipa, Av. Independencia s/n, Hexagonos de Fisica, Arequipa (Peru); Urquizo B, R., E-mail: dgav02@gmail.com [Hospital Nacional Carlos Alberto Seguin Escobedo, Esquina de Peral y Filtro s/n, Arequipa (Peru)

    2015-10-15

    In systems of radiotherapy treatment for cancer, always looking to maximize the radiation dose on the target (tumor) and minimize to the organs at risk or healthy, so they resort to using electron beams that have properties and characteristics of higher dose deposition at fixed depths, directing and focusing the higher dose in the tumor, without harming healthy tissues to which seeks to radiate in the least possible. Simulating the interaction of electron beams with different equivalent tissues to the human body leads to a better dosimetric evaluation, improving the quality of treatment planning. The aim of this study is the comparison from the characterization of several equivalent tissues to the human body such as soft tissue, bone and lung. Based on the simulation of a calibration beam in water phantom with Penelope code and compared with the results of the calibration curves of beams in water vat by a linear accelerator Elekta Synergy of Hospital Nacional Carlos Alberto Seguin Escobedo EsSalud of Arequipa (Peru). From this to evaluate the behavior of electron beams in a homogeneous medium and then further evaluation in the human body homogeneities, for better evaluation and specific treatment planning. (Author)

  6. SAPONIFICATION EQUIVALENT OF DASAMULA TAILA

    OpenAIRE

    Saxena, R. B.

    1994-01-01

    Saponification equivalent values of Dasamula taila are very useful for the technical and analytical work. It gives the mean molecular weight of the glycerides and acids present in Dasamula Taila. Saponification equivalent values of Dasamula taila are reported in different packings.

  7. Saponification equivalent of dasamula taila.

    Science.gov (United States)

    Saxena, R B

    1994-07-01

    Saponification equivalent values of Dasamula taila are very useful for the technical and analytical work. It gives the mean molecular weight of the glycerides and acids present in Dasamula Taila. Saponification equivalent values of Dasamula taila are reported in different packings.

  8. A study on lead equivalent

    International Nuclear Information System (INIS)

    Lin Guanxin

    1991-01-01

    A study on the rules in which the lead equivalent of lead glass changes with the energy of X rays or γ ray is described. The reason of this change is discussed and a new testing method of lead equivalent is suggested

  9. Influence of abutment material on peri-implant soft tissues in anterior areas with thin gingival biotype: a multicentric prospective study.

    Science.gov (United States)

    Lops, Diego; Stellini, Edoardo; Sbricoli, Luca; Cea, Niccolò; Romeo, Eugenio; Bressan, Eriberto

    2017-10-01

    The aim of the present clinical trial was to analyze, through spectrophotometric digital technology, the influence of the abutment material on the color of the peri-implant soft tissue in patients with thin gingival biotype. Thirty-seven patients received an endosseous dental implant in the anterior maxilla. At time of each definitive prosthesis delivery, an all-ceramic crown has been tried on gold, titanium and zirconia abutment. Peri-implant soft-tissue color has been measured through a spectrophotometer after the insertion of each single abutment. Also facial peri-implant soft-tissue thickness was measured at the level of the implant neck through a caliper. A specific software has been utilized to identify a standardized tissue area and to collect the data before the statistical analysis in Lab* color space. ΔE parameters of the selected abutments were tested for correlation with mucosal thickness. Pearson correlation test was used. Only 15 patients met the study inclusion criteria on peri-implant soft-tissue thickness. Peri-implant soft-tissue color was different from that around natural teeth, no matter which type of restorative material was selected. Measurements regarding all the abutments were above the critical threshold of ΔE 8.74 for intraoral color distinction by the naked eye. The ΔE mean values of gold and zirconium abutments were similar (11.43 and 11.37, respectively) and significantly lower (P = 0.03 and P = 0.04, respectively) than the titanium abutment (13.55). In patients with a facial soft-tissue thickness ≤2 mm, the ΔE mean value of gold and zirconia abutments was significantly lower than that of titanium abutments (P = 0.03 and P = 0.04, respectively) and much more close to the reference threshold of 8.74. For peri-implant soft tissue of ≤2 mm, gold or zirconia abutments could be selected in anterior areas treatment. Moreover, the thickness of the peri-implant soft tissue seemed to be a crucial factor in the abutment impact

  10. Subcritical CO{sub 2} sintering of microspheres of different polymeric materials to fabricate scaffolds for tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Bhamidipati, Manjari; Sridharan, BanuPriya [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Scurto, Aaron M. [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS (United States); Detamore, Michael S., E-mail: detamore@ku.edu [Bioengineering Graduate Program, University of Kansas, Lawrence, KS (United States); Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS (United States)

    2013-12-01

    The aim of this study was to use CO{sub 2} at sub-critical pressures as a tool to sinter 3D, macroporous, microsphere-based scaffolds for bone and cartilage tissue engineering. Porous scaffolds composed of ∼ 200 μm microspheres of either poly(lactic-co-glycolic acid) (PLGA) or polycaprolactone (PCL) were prepared using dense phase CO{sub 2} sintering, which were seeded with rat bone marrow mesenchymal stromal cells (rBMSCs), and exposed to either osteogenic (PLGA, PCL) or chondrogenic (PLGA) conditions for 6 weeks. Under osteogenic conditions, the PLGA constructs produced over an order of magnitude more calcium than the PCL constructs, whereas the PCL constructs had far superior mechanical and structural integrity (125 times stiffer than PLGA constructs) at week 6, along with twice the cell content of the PLGA constructs. Chondrogenic cell performance was limited in PLGA constructs, perhaps as a result of the polymer degradation rate being too high. The current study represents the first long-term culture of CO{sub 2}-sintered microsphere-based scaffolds, and has established important thermodynamic differences in sintering between the selected formulations of PLGA and PCL, with the former requiring adjustment of pressure only, and the latter requiring the adjustment of both pressure and temperature. Based on more straightforward sintering conditions and more favorable cell performance, PLGA may be the material of choice for microspheres in a CO{sub 2} sintering application, although a different PLGA formulation with the encapsulation of growth factors, extracellular matrix-derived nanoparticles, and/or buffers in the microspheres may be advantageous for achieving a more superior cell performance than observed here. - Highlights: • The first long-term culture of CO{sub 2}-sintered microsphere-based scaffolds. • Established important thermodynamic differences between sintering PLGA and PCL. • PCL sintering with CO{sub 2} required manipulation of both

  11. What is correct: equivalent dose or dose equivalent

    International Nuclear Information System (INIS)

    Franic, Z.

    1994-01-01

    In Croatian language some physical quantities in radiation protection dosimetry have not precise names. Consequently, in practice either terms in English or mathematical formulas are used. The situation is even worse since the Croatian language only a limited number of textbooks, reference books and other papers are available. This paper compares the concept of ''dose equivalent'' as outlined in International Commission on Radiological Protection (ICRP) recommendations No. 26 and newest, conceptually different concept of ''equivalent dose'' which is introduced in ICRP 60. It was found out that Croatian terminology is both not uniform and unprecise. For the term ''dose equivalent'' was, under influence of Russian and Serbian languages, often used as term ''equivalent dose'' even from the point of view of ICRP 26 recommendations, which was not justified. Unfortunately, even now, in Croatia the legal unit still ''dose equivalent'' defined as in ICRP 26, but the term used for it is ''equivalent dose''. Therefore, in Croatian legislation a modified set of quantities introduced in ICRP 60, should be incorporated as soon as possible

  12. Synthesis and characterization of biodegradable poly (ethylene glycol) and poly (caprolactone diol) end capped poly (propylene fumarate) cross linked amphiphilic hydrogel as tissue engineering scaffold material.

    Science.gov (United States)

    Krishna, Lekshmi; Jayabalan, Muthu

    2009-12-01

    Biodegradable poly (caprolactone diol-co-propylene fumarate-co-ethylene glycol) amphiphilic polymer with poly (ethylene glycol) and poly (caprolactone diol) chain ends (PCL-PPF-PEG) was prepared. PCL-PPF-PEG undergoes fast setting with acrylamide (aqueous solution) by free radical polymerization and produces a crosslinked hydrogel. The cross linked and freeze-dried amphiphilic material has porous and interconnected network. It undergoes higher degree of swelling and water absorption to form hydrogel with hydrophilic and hydrophobic domains at the surface and appreciable tensile strength. The present hydrogel is compatible with L929 fibroblast cells. PCL-PPF-PEG/acrylamide hydrogel is a candidate scaffold material for tissue engineering applications.

  13. Geometric and mechanical properties evaluation of scaffolds for bone tissue applications designing by a reaction-diffusion models and manufactured with a material jetting system

    Directory of Open Access Journals (Sweden)

    Marco A. Velasco

    2016-10-01

    Full Text Available Scaffolds are essential in bone tissue engineering, as they provide support to cells and growth factors necessary to regenerate tissue. In addition, they meet the mechanical function of the bone while it regenerates. Currently, the multiple methods for designing and manufacturing scaffolds are based on regular structures from a unit cell that repeats in a given domain. However, these methods do not resemble the actual structure of the trabecular bone which may work against osseous tissue regeneration. To explore the design of porous structures with similar mechanical properties to native bone, a geometric generation scheme from a reaction-diffusion model and its manufacturing via a material jetting system is proposed. This article presents the methodology used, the geometric characteristics and the modulus of elasticity of the scaffolds designed and manufactured. The method proposed shows its potential to generate structures that allow to control the basic scaffold properties for bone tissue engineering such as the width of the channels and porosity. The mechanical properties of our scaffolds are similar to trabecular tissue present in vertebrae and tibia bones. Tests on the manufactured scaffolds show that it is necessary to consider the orientation of the object relative to the printing system because the channel geometry, mechanical properties and roughness are heavily influenced by the position of the surface analyzed with respect to the printing axis. A possible line for future work may be the establishment of a set of guidelines to consider the effects of manufacturing processes in designing stages.

  14. Comparison of soft tissue effects of conventional ionic, low osmolar ionic and nonionic iodine containing contrast material in experimental animals

    International Nuclear Information System (INIS)

    McAlister, W.H.; Kissane, J.M.

    1990-01-01

    Conventional, low osmolar, and non-ionic iodine containing contrast media and saline controls were placed in the paws, muscles, and subcutaneous tissues of Sprague-Dawley rat thighs. The paw injections were observed and photographed, while the thighs were examined histologically. Results showed that although the low osmolar and non-ionic agents did produce inflammatory reactions and focal necrosis in the soft tissues, they were much better tolerated than were the conventional ionic agents. A non-ionic or low osmolar ionic contrast agent should be strongly considered when a possibility for extravasation exists. (orig.)

  15. Thermoluminescence dosemeter for personal dose equivalent assessment

    International Nuclear Information System (INIS)

    Silva, T.A. da; Rosa, L.A.R. da; Campos, L.L.

    1995-01-01

    The possibility was investigated of utilising a Brazilian thermoluminescence individual dosemeter, usually calibrated in terms of photon dose equivalent, for the assessment of the personal dose equivalent, H p (d), at depths of 0.07 and 10 mm. The dosemeter uses four CaSO 4 :Dy thermoluminescent detectors, between different filters, as the sensitive materials. It was calibrated in gamma and X radiation fields in the energy range from 17 to 1250 keV. Linear combinations of the responses of three detectors, in this energy range, allow the evaluation of H p (0.07) and H p (10), for radiation incidence angles varying from 0 to 60 degrees, with an accuracy better than 35%. The method is not applicable to mixed photon-beta fields. (author)

  16. Materialism.

    Science.gov (United States)

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website. Copyright © 2012 John Wiley & Sons, Ltd.

  17. Evaluation of reference genes for quantitative real-time PCR in oil palm elite planting materials propagated by tissue culture.

    Directory of Open Access Journals (Sweden)

    Pek-Lan Chan

    Full Text Available BACKGROUND: The somatic embryogenesis tissue culture process has been utilized to propagate high yielding oil palm. Due to the low callogenesis and embryogenesis rates, molecular studies were initiated to identify genes regulating the process, and their expression levels are usually quantified using reverse transcription quantitative real-time PCR (RT-qPCR. With the recent release of oil palm genome sequences, it is crucial to establish a proper strategy for gene analysis using RT-qPCR. Selection of the most suitable reference genes should be performed for accurate quantification of gene expression levels. RESULTS: In this study, eight candidate reference genes selected from cDNA microarray study and literature review were evaluated comprehensively across 26 tissue culture samples using RT-qPCR. These samples were collected from two tissue culture lines and media treatments, which consisted of leaf explants cultures, callus and embryoids from consecutive developmental stages. Three statistical algorithms (geNorm, NormFinder and BestKeeper confirmed that the expression stability of novel reference genes (pOP-EA01332, PD00380 and PD00569 outperformed classical housekeeping genes (GAPDH, NAD5, TUBULIN, UBIQUITIN and ACTIN. PD00380 and PD00569 were identified as the most stably expressed genes in total samples, MA2 and MA8 tissue culture lines. Their applicability to validate the expression profiles of a putative ethylene-responsive transcription factor 3-like gene demonstrated the importance of using the geometric mean of two genes for normalization. CONCLUSIONS: Systematic selection of the most stably expressed reference genes for RT-qPCR was established in oil palm tissue culture samples. PD00380 and PD00569 were selected for accurate and reliable normalization of gene expression data from RT-qPCR. These data will be valuable to the research associated with the tissue culture process. Also, the method described here will facilitate the selection

  18. Evaluation of Reference Genes for Quantitative Real-Time PCR in Oil Palm Elite Planting Materials Propagated by Tissue Culture

    Science.gov (United States)

    Chan, Pek-Lan; Rose, Ray J.; Abdul Murad, Abdul Munir; Zainal, Zamri; Leslie Low, Eng-Ti; Ooi, Leslie Cheng-Li; Ooi, Siew-Eng; Yahya, Suzaini; Singh, Rajinder

    2014-01-01

    Background The somatic embryogenesis tissue culture process has been utilized to propagate high yielding oil palm. Due to the low callogenesis and embryogenesis rates, molecular studies were initiated to identify genes regulating the process, and their expression levels are usually quantified using reverse transcription quantitative real-time PCR (RT-qPCR). With the recent release of oil palm genome sequences, it is crucial to establish a proper strategy for gene analysis using RT-qPCR. Selection of the most suitable reference genes should be performed for accurate quantification of gene expression levels. Results In this study, eight candidate reference genes selected from cDNA microarray study and literature review were evaluated comprehensively across 26 tissue culture samples using RT-qPCR. These samples were collected from two tissue culture lines and media treatments, which consisted of leaf explants cultures, callus and embryoids from consecutive developmental stages. Three statistical algorithms (geNorm, NormFinder and BestKeeper) confirmed that the expression stability of novel reference genes (pOP-EA01332, PD00380 and PD00569) outperformed classical housekeeping genes (GAPDH, NAD5, TUBULIN, UBIQUITIN and ACTIN). PD00380 and PD00569 were identified as the most stably expressed genes in total samples, MA2 and MA8 tissue culture lines. Their applicability to validate the expression profiles of a putative ethylene-responsive transcription factor 3-like gene demonstrated the importance of using the geometric mean of two genes for normalization. Conclusions Systematic selection of the most stably expressed reference genes for RT-qPCR was established in oil palm tissue culture samples. PD00380 and PD00569 were selected for accurate and reliable normalization of gene expression data from RT-qPCR. These data will be valuable to the research associated with the tissue culture process. Also, the method described here will facilitate the selection of appropriate

  19. Augmentation of the hard palate thin masticatory mucosa in the potential connective tissue donor sites using two collagen materials-Clinical and histological comparison.

    Science.gov (United States)

    Bednarz, Wojciech; Kobierzycki, Christopher; Dzięgiel, Piotr; Botzenhart, Ute; Gedrange, Tomasz; Ziętek, Marek

    2016-11-01

    Due to the similarity of keratinized gingival and palatal mucosa the latter can pose as a potential donor site for gingival recession coverage. However, its availability is restricted and a thin transplant bears the risk of being rejected. The aim of the present study was to compare the clinical and histological results of thin palatal mucosa augmentation, using lyophilized Biokol ® xenogenous collagen sponge and a suspension of xenogenous Gel 0 ® pure collagen with non-augmented tissue from the same patients. Ten patients simultaneously underwent bilateral augmentation procedures using Biokol ® and Gel 0 ® collagen material. The donor sites were augmented 8 weeks prior to the harvesting of the connective tissue graft (CTG) for the gingival recession coverage procedures. Prior to the implantation of the collagen material and during the course of harvesting the augmented CTG, tissue specimens were taken for histological examination. Prior to the commencement of the study and after it, the parameters of palatal gingival thickness at 4mm (PGT1), and at 8mm apical to the gingival margin (PGT2) around the teeth neighboring the operating fields were determined. In both groups the palatal mucosa had thickened significantly in both measuring sites. An intergroup comparison revealed greater thickening of the masticatory mucosa in the Biokol ® group at both measuring points. The histological image of the grafts, obtained from sites augmented using both test methods, revealed a typical pattern of mature fibrous connective tissue. No epithelial cells were found. Augmentation of thin masticatory mucosa using Biokol ® or Gel 0 ® collagen materials resulted in a significant thickening of the mucosa, which could be demonstrated to be greater in the first group. Copyright © 2016 Elsevier GmbH. All rights reserved.

  20. Numerical modelling of tissue-equivalent proportional counters

    International Nuclear Information System (INIS)

    Segur, P.; Colautti, P.

    1995-01-01

    In this paper a survey is given of the various numerical techniques employed to study the transport of ionising particles inside a TEPC. The first part is devoted to the description of the general concept of particle transport calculations. Thereafter, the different methods available to study transport phenomena and energy deposition in the sensitive volume and in counter walls are described. Finally, the basic ionisation mechanisms which may occur in a counter are described, and the non-equilibrium phenomena which play an important role mainly for counters that are to be used in measurements at the nanodosemeter level are studied. (author)

  1. Symmetries of dynamically equivalent theories

    Energy Technology Data Exchange (ETDEWEB)

    Gitman, D.M.; Tyutin, I.V. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Lebedev Physics Institute, Moscow (Russian Federation)

    2006-03-15

    A natural and very important development of constrained system theory is a detail study of the relation between the constraint structure in the Hamiltonian formulation with specific features of the theory in the Lagrangian formulation, especially the relation between the constraint structure with the symmetries of the Lagrangian action. An important preliminary step in this direction is a strict demonstration, and this is the aim of the present article, that the symmetry structures of the Hamiltonian action and of the Lagrangian action are the same. This proved, it is sufficient to consider the symmetry structure of the Hamiltonian action. The latter problem is, in some sense, simpler because the Hamiltonian action is a first-order action. At the same time, the study of the symmetry of the Hamiltonian action naturally involves Hamiltonian constraints as basic objects. One can see that the Lagrangian and Hamiltonian actions are dynamically equivalent. This is why, in the present article, we consider from the very beginning a more general problem: how the symmetry structures of dynamically equivalent actions are related. First, we present some necessary notions and relations concerning infinitesimal symmetries in general, as well as a strict definition of dynamically equivalent actions. Finally, we demonstrate that there exists an isomorphism between classes of equivalent symmetries of dynamically equivalent actions. (author)

  2. Matching of equivalent field regions

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen; Rengarajan, S.B.

    2005-01-01

    In aperture problems, integral equations for equivalent currents are often found by enforcing matching of equivalent fields. The enforcement is made in the aperture surface region adjoining the two volumes on each side of the aperture. In the case of an aperture in a planar perfectly conducting...... screen, having the same homogeneous medium on both sides and an impressed current on one aide, an alternative procedure is relevant. We make use of the fact that in the aperture the tangential component of the magnetic field due to the induced currents in the screen is zero. The use of such a procedure...... shows that equivalent currents can be found by a consideration of only one of the two volumes into which the aperture plane divides the space. Furthermore, from a consideration of an automatic matching at the aperture, additional information about tangential as well as normal field components...

  3. Safety of radiofrequency treatment over human skin previously injected with medium-term injectable soft-tissue augmentation materials: a controlled pilot trial.

    Science.gov (United States)

    Alam, Murad; Levy, Ross; Pajvani, Urvi; Pavjani, Urvi; Ramierez, James A; Guitart, Joan; Veen, Heather; Gladstone, Hayes B

    2006-03-01

    Several soft-tissue augmentation materials are now available for reduction of nasolabial fold creases and perioral rhytides. Nasolabial folds and perioral rhytides can also be improved by skin tightening delivered by non-ablative radiofrequency (RF) treatment. The purpose of this study was to assess the safety of RF treatment over skin areas recently injected with medium-term injectable soft-tissue augmentation materials. Five subjects were assigned to the experimental arm (augmentation materials plus RF) and one to the control arm (augmentation materials alone). Each subject received injections of 0.3 mL of hyaluronic acid derivative (Restylane) and calcium hydroxylapatite (Radiesse) 3 cm apart on the upper inner arm. Two weeks later, two non-overlapping passes of RF (Thermage ThermaCool TC) were delivered at 63.5 setting with medium-fast 1.5 cm2 tip over injected sites in all of the experimental subjects. Punch skin biopsies were obtained 3 days later from each of the two injection sites on each subject. Light microscopy and digital photomicrographs obtained at low, medium, and high power showed no difference between filler materials in experimental and control subjects. In both cases filler was evident at the deep dermal-subcutaneous junction. Nodule formation, foreign body extravasation, or hemorrhage/clot was not observed grossly or histologically. Subjects and physicians did not report any difference in signs and symptoms between the experimental and control arms. Slightly increased transitory pain was noted when RF was delivered over filler versus over normal skin. Applying RF treatment over the same area 2 weeks after deep dermal injection with hyaluronic acid derivatives or calcium hydroxylapatite does not appear to cause gross morphological changes in the filler material or surrounding skin. Further studies with different parameters are necessary to confirm these findings. 2006 Wiley-Liss, Inc.

  4. Teleparallel equivalent of Lovelock gravity

    Science.gov (United States)

    González, P. A.; Vásquez, Yerko

    2015-12-01

    There is a growing interest in modified gravity theories based on torsion, as these theories exhibit interesting cosmological implications. In this work inspired by the teleparallel formulation of general relativity, we present its extension to Lovelock gravity known as the most natural extension of general relativity in higher-dimensional space-times. First, we review the teleparallel equivalent of general relativity and Gauss-Bonnet gravity, and then we construct the teleparallel equivalent of Lovelock gravity. In order to achieve this goal, we use the vielbein and the connection without imposing the Weitzenböck connection. Then, we extract the teleparallel formulation of the theory by setting the curvature to null.

  5. Materials

    CSIR Research Space (South Africa)

    Van Wyk, Llewellyn V

    2009-02-01

    Full Text Available . It is generally included as part of a structurally insulated panel (SIP) where the foam is sandwiched between external skins of steel, wood or cement. Cement composites Cement bonded composites are an important class of building materials. These products... for their stone buildings, including the Egyptians, Aztecs and Inca’s. As stone is a very dense material it requires intensive heating to become warm. Rocks were generally stacked dry but mud, and later cement, can be used as a mortar to hold the rocks...

  6. Thermoplastic starch/ethylene vinyl alcohol/forsterite nanocomposite as a candidate material for bone tissue engineering

    International Nuclear Information System (INIS)

    Mahdieh, Zahra; Bagheri, Reza; Eslami, Masoud; Amiri, Mohammad; Shokrgozar, Mohammad Ali; Mehrjoo, Morteza

    2016-01-01

    Recently, biodegradable polymers such as starch based blends have been well renowned in the biomedical field. Studies have considered them suitable for bone scaffolds, bone cements, tissue engineering scaffolds, drug delivery systems and hydrogels. The aim of this study was to synthesize nanocomposite biomaterial consisting a blend of thermoplastic starch and ethylene vinyl alcohol as the polymer matrix, and nano-structured forsterite as the ceramic reinforcing phase for bone tissue engineering applications. Furthermore, vitamin E was applied as a thermal stabilizer during melt compounding. Extrusion and injection molding were incorporated for melt blending and shaping of samples, respectively. With blending thermoplastic starch and ethylene vinyl alcohol, some properties of thermoplastic starch such as degradation rate and water absorption were modified. In addition, using nanoforsterite as the ceramic reinforcing phase resulted in the improvement of mechanical and biological traits. The addition of nanoforsterite decreased the weight loss of the thermoplastic starch and ethylene vinyl alcohol blend in simulated body fluid. Moreover, this addition modified the pH in the MTT (methyl thiazolyl tetrazolium) assay and stimulated the cell proliferation. Cell adhesion assays indicated a favorable interaction between cells and the biomaterial. The proposed nanocomposite has appropriate biocompatibility, as well as mechanical properties in order to be used in bone tissue engineering. - Highlights: • A biodegradable nanocomposite is proposed for orthopedic applications. • Vitamin E is used as an antioxidant to prevent the thermomechanical degradations. • Nanoforsterite reduced the composite degradation rate in the simulated body fluid. • Nanoforsterite modified pH in MTT assay and stimulated cell proliferation.

  7. Thermoplastic starch/ethylene vinyl alcohol/forsterite nanocomposite as a candidate material for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Mahdieh, Zahra [Polymeric Materials Research Group (PMRG), Department of Materials Science and Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9466 (Iran, Islamic Republic of); Bagheri, Reza, E-mail: rezabagh@sharif.edu [Polymeric Materials Research Group (PMRG), Department of Materials Science and Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9466 (Iran, Islamic Republic of); Eslami, Masoud; Amiri, Mohammad [Polymeric Materials Research Group (PMRG), Department of Materials Science and Engineering, Sharif University of Technology, Tehran, P.O. Box 11155-9466 (Iran, Islamic Republic of); Shokrgozar, Mohammad Ali; Mehrjoo, Morteza [National Cell Bank of Iran, Pasteur Institute of Iran, Tehran (Iran, Islamic Republic of)

    2016-12-01

    Recently, biodegradable polymers such as starch based blends have been well renowned in the biomedical field. Studies have considered them suitable for bone scaffolds, bone cements, tissue engineering scaffolds, drug delivery systems and hydrogels. The aim of this study was to synthesize nanocomposite biomaterial consisting a blend of thermoplastic starch and ethylene vinyl alcohol as the polymer matrix, and nano-structured forsterite as the ceramic reinforcing phase for bone tissue engineering applications. Furthermore, vitamin E was applied as a thermal stabilizer during melt compounding. Extrusion and injection molding were incorporated for melt blending and shaping of samples, respectively. With blending thermoplastic starch and ethylene vinyl alcohol, some properties of thermoplastic starch such as degradation rate and water absorption were modified. In addition, using nanoforsterite as the ceramic reinforcing phase resulted in the improvement of mechanical and biological traits. The addition of nanoforsterite decreased the weight loss of the thermoplastic starch and ethylene vinyl alcohol blend in simulated body fluid. Moreover, this addition modified the pH in the MTT (methyl thiazolyl tetrazolium) assay and stimulated the cell proliferation. Cell adhesion assays indicated a favorable interaction between cells and the biomaterial. The proposed nanocomposite has appropriate biocompatibility, as well as mechanical properties in order to be used in bone tissue engineering. - Highlights: • A biodegradable nanocomposite is proposed for orthopedic applications. • Vitamin E is used as an antioxidant to prevent the thermomechanical degradations. • Nanoforsterite reduced the composite degradation rate in the simulated body fluid. • Nanoforsterite modified pH in MTT assay and stimulated cell proliferation.

  8. Comments on field equivalence principles

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen

    1987-01-01

    It is pointed Out that often-used arguments based on a short-circuit concept in presentations of field equivalence principles are not correct. An alternative presentation based on the uniqueness theorem is given. It does not contradict the results obtained by using the short-circuit concept...

  9. Intrinsic material property differences in bone tissue from patients suffering low-trauma osteoporotic fractures, compared to matched non-fracturing women.

    Science.gov (United States)

    Vennin, S; Desyatova, A; Turner, J A; Watson, P A; Lappe, J M; Recker, R R; Akhter, M P

    2017-04-01

    Osteoporotic (low-trauma) fractures are a significant public health problem. Over 50% of women over 50yrs. of age will suffer an osteoporotic fracture in their remaining lifetimes. While current therapies reduce skeletal fracture risk by maintaining or increasing bone density, additional information is needed that includes the intrinsic material strength properties of bone tissue to help develop better treatments, since measurements of bone density account for no more than ~50% of fracture risk. The hypothesis tested here is that postmenopausal women who have sustained osteoporotic fractures have reduced bone quality, as indicated with measures of intrinsic material properties compared to those who have not fractured. Transiliac biopsies (N=120) were collected from fracturing (N=60, Cases) and non-fracturing postmenopausal women (N=60, age- and BMD-matched Controls) to measure intrinsic material properties using the nano-indentation technique. Each biopsy specimen was embedded in epoxy resin and then ground, polished and used for the nano-indentation testing. After calibration, multiple indentations were made using quasi-static (hardness, modulus) and dynamic (storage and loss moduli) testing protocols. Multiple indentations allowed the median and variance to be computed for each type of measurement for each specimen. Cases were found to have significantly lower median values for cortical hardness and indentation modulus. In addition, cases showed significantly less within-specimen variability in cortical modulus, cortical hardness, cortical storage modulus and trabecular hardness, and more within-specimen variability in trabecular loss modulus. Multivariate modeling indicated the presence of significant independent mechanical effects of cortical loss modulus, along with variability of cortical storage modulus, cortical loss modulus, and trabecular hardness. These results suggest mechanical heterogeneity of bone tissue may contribute to fracture resistance

  10. Extended automated separation techniques in destructive neutron activation analysis; application to various biological materials, including human tissues and blood

    International Nuclear Information System (INIS)

    Tjioe, P.S.; Goeij, J.J.M. de; Houtman, J.P.W.

    1976-09-01

    Neutron activation analysis may be performed as a multi-element and low-level technique for many important trace elements in biological materials, provided that post-irradiation chemical separations are applied. This paper describes a chemical separation consisting of automated procedures for destruction, distillation, and anion-chromatography. The system developed enables the determination of 14 trace elements in biological materials, viz. antimony, arsenic, bromine, cadmium, chromium, cobalt, copper, gold, iron, mercury, molybdenum, nickel, selenium, and zinc. The aspects of sample preparation, neutron irradiation, gamma-spectrum evaluation, and blank-value contribution are also discussed

  11. Chitosan functionalized poly-ε-caprolactone electrospun fibers and 3D printed scaffolds as antibacterial materials for tissue engineering applications.

    Science.gov (United States)

    Tardajos, Myriam G; Cama, Giuseppe; Dash, Mamoni; Misseeuw, Lara; Gheysens, Tom; Gorzelanny, Christian; Coenye, Tom; Dubruel, Peter

    2018-07-01

    Tissue engineering (TE) approaches often employ polymer-based scaffolds to provide support with a view to the improved regeneration of damaged tissues. The aim of this research was to develop a surface modification method for introducing chitosan as an antibacterial agent in both electrospun membranes and 3D printed poly-ε-caprolactone (PCL) scaffolds. The scaffolds were functionalized by grafting methacrylic acid N-hydroxysuccinimide ester (NHSMA) onto the surface after Ar-plasma/air activation. Subsequently, the newly-introduced NHS groups were used to couple with chitosan of various molecular weights (Mw). High Mw chitosan exhibited a better coverage of the surface as indicated by the higher N% detected by X-ray photoelectron spectroscopy (XPS) and the observations with either scanning electron microscopy (SEM)(for fibers) or Coomassie blue staining (for 3D-printed scaffolds). A lactate dehydrogenase assay (LDH) using L929 fibroblasts demonstrated the cell-adhesion and cell-viability capacity of the modified samples. The antibacterial properties against S. aureus ATCC 6538 and S. epidermidis ET13 revealed a slower bacterial growth rate on the surface of the chitosan modified scaffolds, regardless the chitosan Mw. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Foundations of gravitation theory: the principle of equivalence

    International Nuclear Information System (INIS)

    Haugan, M.P.

    1978-01-01

    A new framework is presented within which to discuss the principle of equivalence and its experimental tests. The framework incorporates a special structure imposed on the equivalence principle by the principle of energy conservation. This structure includes relations among the conceptual components of the equivalence principle as well as quantitative relations among the outcomes of its experimental tests. One of the most striking new results obtained through use of this framework is a connection between the breakdown of local Lorentz invariance and the breakdown of the principle that all bodies fall with the same acceleration in a gravitational field. An extensive discussion of experimental tests of the equivalence principle and their significance is also presented. Within the above framework, theory-independent analyses of a broad range of equivalence principle tests are possible. Gravitational redshift experiments. Doppler-shift experiments, the Turner-Hill and Hughes-Drever experiments, and a number of solar-system tests of gravitation theories are analyzed. Application of the techniques of theoretical nuclear physics to the quantitative interpretation of equivalence principle tests using laboratory materials of different composition yields a number of important results. It is found that current Eotvos experiments significantly demonstrate the compatibility of the weak interactions with the equivalence principle. It is also shown that the Hughes-Drever experiment is the most precise test of local Lorentz invariance yet performed. The work leads to a strong, tightly knit empirical basis for the principle of equivalence, the central pillar of the foundations of gravitation theory

  13. EQUIVALENCE VERSUS NON-EQUIVALENCE IN ECONOMIC TRANSLATION

    Directory of Open Access Journals (Sweden)

    Cristina, Chifane

    2012-01-01

    Full Text Available This paper aims at highlighting the fact that “equivalence” represents a concept worth revisiting and detailing upon when tackling the translation process of economic texts both from English into Romanian and from Romanian into English. Far from being exhaustive, our analysis will focus upon the problems arising from the lack of equivalence at the word level. Consequently, relevant examples from the economic field will be provided to account for the following types of non-equivalence at word level: culturespecific concepts; the source language concept is not lexicalised in the target language; the source language word is semantically complex; differences in physical and interpersonal perspective; differences in expressive meaning; differences in form; differences in frequency and purpose of using specific forms and the use of loan words in the source text. Likewise, we shall illustrate a number of translation strategies necessary to deal with the afore-mentioned cases of non-equivalence: translation by a more general word (superordinate; translation by a more neutral/less expressive word; translation by cultural substitution; translation using a loan word or loan word plus explanation; translation by paraphrase using a related word; translation by paraphrase using unrelated words; translation by omission and translation by illustration.

  14. Exact equivalent straight waveguide model for bent and twisted waveguides

    DEFF Research Database (Denmark)

    Shyroki, Dzmitry

    2008-01-01

    Exact equivalent straight waveguide representation is given for a waveguide of arbitrary curvature and torsion. No assumptions regarding refractive index contrast, isotropy of materials, or particular morphology in the waveguide cross section are made. This enables rigorous full-vector modeling...... of in-plane curved or helically wound waveguides with use of available simulators for straight waveguides without the restrictions of the known approximate equivalent-index formulas....

  15. Equivalence groups of (2+1) dimensional diffusion equation

    OpenAIRE

    Özer, Saadet

    2017-01-01

    If a given set of differential equations contain somearbitrary functions, parameters, we have in fact a family of sets of equationsof the same structure. Almost all field equations of classical physichs havethis property, representing different materials with various paramaters.  Equivalence groups are defined as the groupof transformations which leave a given family of differential equationsinvariant. Therefore, equivalence group of family of differential equations isan important area within...

  16. Quantifying the Combined Effect of Radiation Therapy and Hyperthermia in Terms of Equivalent Dose Distributions

    International Nuclear Information System (INIS)

    Kok, H. Petra; Crezee, Johannes; Franken, Nicolaas A.P.; Stalpers, Lukas J.A.; Barendsen, Gerrit W.; Bel, Arjan

    2014-01-01

    Purpose: To develop a method to quantify the therapeutic effect of radiosensitization by hyperthermia; to this end, a numerical method was proposed to convert radiation therapy dose distributions with hyperthermia to equivalent dose distributions without hyperthermia. Methods and Materials: Clinical intensity modulated radiation therapy plans were created for 15 prostate cancer cases. To simulate a clinically relevant heterogeneous temperature distribution, hyperthermia treatment planning was performed for heating with the AMC-8 system. The temperature-dependent parameters α (Gy −1 ) and β (Gy −2 ) of the linear–quadratic model for prostate cancer were estimated from the literature. No thermal enhancement was assumed for normal tissue. The intensity modulated radiation therapy plans and temperature distributions were exported to our in-house-developed radiation therapy treatment planning system, APlan, and equivalent dose distributions without hyperthermia were calculated voxel by voxel using the linear–quadratic model. Results: The planned average tumor temperatures T90, T50, and T10 in the planning target volume were 40.5°C, 41.6°C, and 42.4°C, respectively. The planned minimum, mean, and maximum radiation therapy doses were 62.9 Gy, 76.0 Gy, and 81.0 Gy, respectively. Adding hyperthermia yielded an equivalent dose distribution with an extended 95% isodose level. The equivalent minimum, mean, and maximum doses reflecting the radiosensitization by hyperthermia were 70.3 Gy, 86.3 Gy, and 93.6 Gy, respectively, for a linear increase of α with temperature. This can be considered similar to a dose escalation with a substantial increase in tumor control probability for high-risk prostate carcinoma. Conclusion: A model to quantify the effect of combined radiation therapy and hyperthermia in terms of equivalent dose distributions was presented. This model is particularly instructive to estimate the potential effects of interaction from different treatment

  17. Measurements of mechanical anisotropy in brain tissue and implications for transversely isotropic material models of white matter

    OpenAIRE

    Feng, Yuan; Okamoto, Ruth J.; Namani, Ravi; Genin, Guy M.; Bayly, Philip V.

    2013-01-01

    White matter in the brain is structurally anisotropic, consisting largely of bundles of aligned, myelin-sheathed axonal fibers. White matter is believed to be mechanically anisotropic as well. Specifically, transverse isotropy is expected locally, with the plane of isotropy normal to the local mean fiber direction. Suitable material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy–Green strain tensor to account for the effects of rela...

  18. On the calibration of photon dosemeters in the equivalent dose units

    International Nuclear Information System (INIS)

    Bregadze, Yu.I.; Isaev, B.M.; Maslyaev, P.F.

    1980-01-01

    General aspects of transition from exposure dose of photo radiation to equivalent one are considered. By determination the equivalent dose is a function of point location in an irradiated object, that is why it is necessary to know equivalent dose distribution in the human body for uniform description of the risk degree. The international electrotechnical comission recommends to measure equivalent doses at 7 and 800 mg/cm 2 depths in a tissue-equivalent ball with 30 cm diameter, calling them skin equivalent dose and depth equivalent dose, respectively, and to compare them with the permissible 500 mZ and 50 mZ a year, respectively. Practical transition to using equivalent dose for evaluation of radiation danger of being in photon radiation field of low energy should include measures on regraduating already produced dose meters, graduating the dose meters under production and developing the system of their metrologic supply [ru

  19. Performance of fast-setting impression materials in the reproduction of subgingival tooth surfaces without soft tissue retraction.

    Science.gov (United States)

    Rudolph, Heike; Röhl, Andreas; Walter, Michael H; Luthardt, Ralph G; Quaas, Sebastian

    2014-01-01

    Fast-setting impression materials may be prone to inaccuracies due to accidental divergence from the recommended mixing protocol. This prospective randomized clinical trial aimed to assess three-dimensional (3D) deviations in the reproduction of subgingival tooth surfaces and to determine the effect of either following or purposely diverging from the recommended mixing procedure for a fast-setting addition-curing silicone (AS) and fast-setting polyether (PE). After three impressions each were taken from 96 participants, sawcut gypsum casts were fabricated with a standardized procedure and then optically digitized. Data were assessed with a computer-aided 3D analysis. For AS impressions, multivariate analysis of variance revealed a significant influence of the individual tooth and the degree to which the recommended mixing protocol was violated. For PE impressions, the ambient air temperature and individual tooth showed significant effects, while divergence from the recommended mixing protocol was not of significance. The fast-setting PE material was not affected by changes in the recommended mixing protocol. For the two fast-setting materials examined, no divergences from the recommended mixing protocol of less than 2 minutes led to failures in the reproduction of the subgingival tooth surfaces.

  20. The Source Equivalence Acceleration Method

    International Nuclear Information System (INIS)

    Everson, Matthew S.; Forget, Benoit

    2015-01-01

    Highlights: • We present a new acceleration method, the Source Equivalence Acceleration Method. • SEAM forms an equivalent coarse group problem for any spatial method. • Equivalence is also formed across different spatial methods and angular quadratures. • Testing is conducted using OpenMOC and performance is compared with CMFD. • Results show that SEAM is preferable for very expensive transport calculations. - Abstract: Fine-group whole-core reactor analysis remains one of the long sought goals of the reactor physics community. Such a detailed analysis is typically too computationally expensive to be realized on anything except the largest of supercomputers. Recondensation using the Discrete Generalized Multigroup (DGM) method, though, offers a relatively cheap alternative to solving the fine group transport problem. DGM, however, suffered from inconsistencies when applied to high-order spatial methods. While an exact spatial recondensation method was developed and provided full spatial consistency with the fine group problem, this approach substantially increased memory requirements for realistic problems. The method described in this paper, called the Source Equivalence Acceleration Method (SEAM), forms a coarse-group problem which preserves the fine-group problem even when using higher order spatial methods. SEAM allows recondensation to converge to the fine-group solution with minimal memory requirements and little additional overhead. This method also provides for consistency when using different spatial methods and angular quadratures between the coarse group and fine group problems. SEAM was implemented in OpenMOC, a 2D MOC code developed at MIT, and its performance tested against Coarse Mesh Finite Difference (CMFD) acceleration on the C5G7 benchmark problem and on a 361 group version of the problem. For extremely expensive transport calculations, SEAM was able to outperform CMFD, resulting in speed-ups of 20–45 relative to the normal power

  1. Equivalent statistics and data interpretation.

    Science.gov (United States)

    Francis, Gregory

    2017-08-01

    Recent reform efforts in psychological science have led to a plethora of choices for scientists to analyze their data. A scientist making an inference about their data must now decide whether to report a p value, summarize the data with a standardized effect size and its confidence interval, report a Bayes Factor, or use other model comparison methods. To make good choices among these options, it is necessary for researchers to understand the characteristics of the various statistics used by the different analysis frameworks. Toward that end, this paper makes two contributions. First, it shows that for the case of a two-sample t test with known sample sizes, many different summary statistics are mathematically equivalent in the sense that they are based on the very same information in the data set. When the sample sizes are known, the p value provides as much information about a data set as the confidence interval of Cohen's d or a JZS Bayes factor. Second, this equivalence means that different analysis methods differ only in their interpretation of the empirical data. At first glance, it might seem that mathematical equivalence of the statistics suggests that it does not matter much which statistic is reported, but the opposite is true because the appropriateness of a reported statistic is relative to the inference it promotes. Accordingly, scientists should choose an analysis method appropriate for their scientific investigation. A direct comparison of the different inferential frameworks provides some guidance for scientists to make good choices and improve scientific practice.

  2. Equivalent nozzle in thermomechanical problems

    International Nuclear Information System (INIS)

    Cesari, F.

    1977-01-01

    When analyzing nuclear vessels, it is most important to study the behavior of the nozzle cylinder-cylinder intersection. For the elastic field, this analysis in three dimensions is quite easy using the method of finite elements. The same analysis in the non-linear field becomes difficult for designs in 3-D. It is therefore necessary to resolve a nozzle in two dimensions equivalent to a 3-D nozzle. The purpose of the present work is to find an equivalent nozzle both with a mechanical and thermal load. This has been achieved by the analysis in three dimensions of a nozzle and a nozzle cylinder-sphere intersection, of a different radius. The equivalent nozzle will be a nozzle with a sphere radius in a given ratio to the radius of a cylinder; thus, the maximum equivalent stress is the same in both 2-D and 3-D. The nozzle examined derived from the intersection of a cylindrical vessel of radius R=191.4 mm and thickness T=6.7 mm with a cylindrical nozzle of radius r=24.675 mm and thickness t=1.350 mm, for which the experimental results for an internal pressure load are known. The structure was subdivided into 96 finite, three-dimensional and isoparametric elements with 60 degrees of freedom and 661 total nodes. Both the analysis with a mechanical load as well as the analysis with a thermal load were carried out on this structure according to the Bersafe system. The thermal load consisted of a transient typical of an accident occurring in a sodium-cooled fast reactor, with a peak of the temperature (540 0 C) for the sodium inside the vessel with an insulating argon temperature constant at 525 0 C. The maximum value of the equivalent tension was found in the internal area at the union towards the vessel side. The analysis of the nozzle in 2-D consists in schematizing the structure as a cylinder-sphere intersection, where the sphere has a given relation to the

  3. Multiphase poroelastic finite element models for soft tissue structures

    International Nuclear Information System (INIS)

    Simon, B.R.

    1992-01-01

    During the last two decades, biological structures with soft tissue components have been modeled using poroelastic or mixture-based constitutive laws, i.e., the material is viewed as a deformable (porous) solid matrix that is saturated by mobile tissue fluid. These structures exhibit a highly nonlinear, history-dependent material behavior; undergo finite strains; and may swell or shrink when tissue ionic concentrations are altered. Give the geometric and material complexity of soft tissue structures and that they are subjected to complicated initial and boundary conditions, finite element models (FEMs) have been very useful for quantitative structural analyses. This paper surveys recent applications of poroelastic and mixture-based theories and the associated FEMs for the study of the biomechanics of soft tissues, and indicates future directions for research in this area. Equivalent finite-strain poroelastic and mixture continuum biomechanical models are presented. Special attention is given to the identification of material properties using a porohyperelastic constitutive law ans a total Lagrangian view for the formulation. The associated FEMs are then formulated to include this porohyperelastic material response and finite strains. Extensions of the theory are suggested in order to include inherent viscoelasticity, transport phenomena, and swelling in soft tissue structures. A number of biomechanical research areas are identified, and possible applications of the porohyperelastic and mixture-based FEMs are suggested. 62 refs., 11 figs., 3 tabs

  4. 21 CFR 26.9 - Equivalence determination.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Equivalence determination. 26.9 Section 26.9 Food... Specific Sector Provisions for Pharmaceutical Good Manufacturing Practices § 26.9 Equivalence determination... document insufficient evidence of equivalence, lack of opportunity to assess equivalence or a determination...

  5. Information Leakage from Logically Equivalent Frames

    Science.gov (United States)

    Sher, Shlomi; McKenzie, Craig R. M.

    2006-01-01

    Framing effects are said to occur when equivalent frames lead to different choices. However, the equivalence in question has been incompletely conceptualized. In a new normative analysis of framing effects, we complete the conceptualization by introducing the notion of information equivalence. Information equivalence obtains when no…

  6. Wijsman Orlicz Asymptotically Ideal -Statistical Equivalent Sequences

    Directory of Open Access Journals (Sweden)

    Bipan Hazarika

    2013-01-01

    in Wijsman sense and present some definitions which are the natural combination of the definition of asymptotic equivalence, statistical equivalent, -statistical equivalent sequences in Wijsman sense. Finally, we introduce the notion of Cesaro Orlicz asymptotically -equivalent sequences in Wijsman sense and establish their relationship with other classes.

  7. Equivalence relations of AF-algebra extensions

    Indian Academy of Sciences (India)

    In this paper, we consider equivalence relations of *-algebra extensions and describe the relationship between the isomorphism equivalence and the unitary equivalence. We also show that a certain group homomorphism is the obstruction for these equivalence relations to be the same.

  8. Compositional analysis of Chinese water chestnut (Eleocharis dulcis) cell-wall material from parenchyma, epidermis, and subepidermal tissues.

    Science.gov (United States)

    Grassby, Terri; Jay, Andrew J; Merali, Zara; Parker, Mary L; Parr, Adrian J; Faulds, Craig B; Waldron, Keith W

    2013-10-09

    Chinese water chestnut (Eleocharis dulcis (Burman f.) Trin ex Henschel) is a corm consumed globally in Oriental-style cuisine. The corm consists of three main tissues, the epidermis, subepidermis, and parenchyma; the cell walls of which were analyzed for sugar, phenolic, and lignin content. Sugar content, measured by gas chromatography, was higher in the parenchyma cell walls (931 μg/mg) than in the subepidermis (775 μg/mg) or epidermis (685 μg/mg). The alkali-extractable phenolic content, measured by high-performance liquid chromatography, was greater in the epidermal (32.4 μg/mg) and subepidermal cell walls (21.7 μg/mg) than in the cell walls of the parenchyma (12.3 μg/mg). The proportion of diferulic acids was higher in the parenchyma. The Klason lignin content of epidermal and subepidermal cell walls was ~15%. Methylation analysis of Chinese water chestnut cell-wall polysaccharides identified xyloglucan as the predominant hemicellulose in the parenchyma for the first time, and also a significant pectin component, similar to other nongraminaceous monocots.

  9. New generation poly(ε-caprolactone)/gel-derived bioactive glass composites for bone tissue engineering: Part I. Material properties.

    Science.gov (United States)

    Dziadek, Michal; Menaszek, Elzbieta; Zagrajczuk, Barbara; Pawlik, Justyna; Cholewa-Kowalska, Katarzyna

    2015-11-01

    Poly(ε-caprolactone) (PCL) based composite films containing 12 and 21vol.% bioactive glass (SBG) microparticles were prepared by solvent casting method. Two gel-derived SBGs of SiO2-CaO-P2O5 system differing in SiO2 and CaO contents were applied (mol%): S2: 80SiO2, 16CaO, 4P2O5 and A2: 40SiO2, 54CaO, 6P2O5. The surfaces of the films in contact with Petri dish and exposed to the gas phase during casting were denoted as GS and AS, respectively. Both surfaces of films were characterised in terms of their morphology, micro- and nano-topography as well as wettability. Also mechanical properties (tensile strength, Young's modulus) and PCL matrix crystallinity (degree of crystallinity, crystal size) were evaluated. Degradation behaviour was examined by incubation of materials in UHQ-water at 37°C for 56weeks. The crystallinity, melting temperature and mass loss of incubated materials and pH changes of water were monitored. Furthermore, proliferation of MG-63 osteoblastic cells by direct contact and cytotoxic effect of obtained materials were investigated. Results showed that opposite surfaces of the same polymer and composite films differ in studied surface parameters. The addition of SBG particles into PCL matrix improves nano- and micro-roughness of both surfaces, enhances the hydrophilicity of GS surfaces (~67° for 21A2-PCL compared to ~78° for pure PCL) and also makes AS surface more hydrophobic (~94° for 21S2-PCL compared to ~86° for pure PCL). The nucleation density of PCL was increased with increasing content of SBG particles, which results in the large number of fine spherulites on composite AS surfaces observed using polarized optical (POM), scanning electron (SEM), and atomic force (AFM) microscopies. Higher content of SBG particles causes a notable increase of Young's modulus (from 0.38GPa for pure PCL, 0.90GPa for 12A2-PCL to 1.31GPa for 21A2-PCL), which also depends on SBG chemical composition. After 56-week degradation test, considerably higher

  10. An algorithm to biological tissues evaluation in pediatric examinations

    International Nuclear Information System (INIS)

    Souza, R.T.F.; Miranda, J.R.A.; Alvarez, M.; Velo, A.F.; Pina, D.R.

    2011-01-01

    A prerequisite for the construction of phantoms is the quantification of the average thickness of biological tissues and the equivalence of these simulators in simulator material thicknesses. This study aim to develop an algorithm to classify and quantify tissues, based on normal distribution of CT numbers of anatomical structures found in the mean free path of the X-rays beam, using the examination histogram to carry out this evaluation. We have considered an algorithm for the determination of the equivalent biological tissues thickness from histograms. This algorithm classifies different biological tissues from tomographic exams in DICOM format and calculates the average thickness of these tissues. The founded results had revealed coherent with literature, presenting discrepancies of up to 21,6%, relative to bone tissue, analyzed for anthropomorphic phantom (RANDO). These results allow using this methodology in livings tissues, for the construction of thorax homogeneous phantoms, of just born and suckling patients, who will be used later in the optimization process of pediatrics radiographic images. (author)

  11. Calculation of neutron fluence to dose equivalent conversion coefficients using GEANT4

    International Nuclear Information System (INIS)

    Ribeiro, Rosane M.; Santos, Denison de S.; Queiroz Filho, Pedro P. de; Mauricio, CLaudia L.P.; Silva, Livia K. da; Pessanha, Paula R.

    2014-01-01

    Fluence to dose equivalent conversion coefficients provide the basis for the calculation of area and personal monitors. Recently, the ICRP has started a revision of these coefficients, including new Monte Carlo codes for benchmarking. So far, little information is available about neutron transport below 10 MeV in tissue-equivalent (TE) material performed with Monte Carlo GEANT4 code. The objective of this work is to calculate neutron fluence to personal dose equivalent conversion coefficients, H p (10)/Φ, with GEANT4 code. The incidence of monoenergetic neutrons was simulated as an expanded and aligned field, with energies ranging between thermal neutrons to 10 MeV on the ICRU slab of dimension 30 x 30 x 15 cm 3 , composed of 76.2% of oxygen, 10.1% of hydrogen, 11.1% of carbon and 2.6% of nitrogen. For all incident energy, a cylindrical sensitive volume is placed at a depth of 10 mm, in the largest surface of the slab (30 x 30 cm 2 ). Physic process are included for neutrons, photons and charged particles, and calculations are made for neutrons and secondary particles which reach the sensitive volume. Results obtained are thus compared with values published in ICRP 74. Neutron fluence in the sensitive volume was calculated for benchmarking. The Monte Carlo GEANT4 code was found to be appropriate to calculate neutron doses at energies below 10 MeV correctly. (author)

  12. The radiobiology of boron neutron capture therapy: Are ''photon-equivalent'' doses really photon-equivalent?

    International Nuclear Information System (INIS)

    Coderre, J.A.; Diaz, A.Z.; Ma, R.

    2001-01-01

    Boron neutron capture therapy (BNCT) produces a mixture of radiation dose components. The high-linear energy transfer (LET) particles are more damaging in tissue than equal doses of low-LET radiation. Each of the high-LET components can multiplied by an experimentally determined factor to adjust for the increased biological effectiveness and the resulting sum expressed in photon-equivalent units (Gy-Eq). BNCT doses in photon-equivalent units are based on a number of assumptions. It may be possible to test the validity of these assumptions and the accuracy of the calculated BNCT doses by 1) comparing the effects of BNCT in other animal or biological models where the effects of photon radiation are known, or 2) if there are endpoints reached in the BNCT dose escalation clinical trials that can be related to the known response to photons of the tissue in question. The calculated Gy-Eq BNCT doses delivered to dogs and to humans with BPA and the epithermal neutron beam of the Brookhaven Medical Research Reactor were compared to expected responses to photon irradiation. The data indicate that Gy-Eq doses in brain may be underestimated. Doses to skin are consistent with the expected response to photons. Gy-Eq doses to tumor are significantly overestimated. A model system of cells in culture irradiated at various depths in a lucite phantom using the epithermal beam is under development. Preliminary data indicate that this approach can be used to detect differences in the relative biological effectiveness of the beam. The rat 9L gliosarcoma cell survival data was converted to photon-equivalent doses using the same factors assumed in the clinical studies. The results superimposed on the survival curve derived from irradiation with Cs-137 photons indicating the potential utility of this model system. (author)

  13. Ex Vivo Produced Oral Mucosa Equivalent by Using the Direct Explant Cell Culture Technique

    Directory of Open Access Journals (Sweden)

    Kamile Öztürk

    2012-09-01

    Full Text Available Objective: The aim of this study is the histological and immunohistochemical evaluation of ex vivo produced oral mucosal equivalents using keratinocytes cultured by direct explant technique.Material and Methods: Oral mucosa tissue samples were obtained from the keratinized gingival tissues of 14 healthy human subjects. Human oral mucosa keratinocytes from an oral mucosa biopsy specimen were dissociated by the explant technique. Once a sufficient population of keratinocytes was reached, they were seeded onto the type IV collagen coated “AlloDerm” and taken for histological and immunohistochemical examinations at 11 days postseeding of the keratinocytes on the cadaveric human dermal matrix.Results: Histopathologically and immunohistochemically, 12 out of 14 successful ex vivo produced oral mucosa equivalents (EVPOME that consisted of a stratified epidermis on a dermal matrix have been developed with keratinocytes cultured by the explant technique.Conclusion: The technical handling involved in the direct explant method at the beginning of the process has fewer steps than the enzymatic method and use of the direct explant technique protocol for culturing of human oral mucosa keratinocyte may be more adequate for EVPOME production.

  14. Calculation methods for determining dose equivalent

    International Nuclear Information System (INIS)

    Endres, G.W.R.; Tanner, J.E.; Scherpelz, R.I.; Hadlock, D.E.

    1987-11-01

    A series of calculations of neutron fluence as a function of energy in an anthropomorphic phantom was performed to develop a system for determining effective dose equivalent for external radiation sources. Critical organ dose equivalents are calculated and effective dose equivalents are determined using ICRP-26 [1] methods. Quality factors based on both present definitions and ICRP-40 definitions are used in the analysis. The results of these calculations are presented and discussed. The effective dose equivalent determined using ICRP-26 methods is significantly smaller than the dose equivalent determined by traditional methods. No existing personnel dosimeter or health physics instrument can determine effective dose equivalent. At the present time, the conversion of dosimeter response to dose equivalent is based on calculations for maximal or ''cap'' values using homogeneous spherical or cylindrical phantoms. The evaluated dose equivalent is, therefore, a poor approximation of the effective dose equivalent as defined by ICRP Publication 26. 3 refs., 2 figs., 1 tab

  15. Spectra from 2.5-15 μm of tissue phantom materials, optical clearing agents and ex vivo human skin: implications for depth profiling of human skin

    International Nuclear Information System (INIS)

    Viator, John A; Choi, Bernard; Peavy, George M; Kimel, Sol; Nelson, J Stuart

    2003-01-01

    Infrared measurements have been used to profile or image biological tissue, including human skin. Usually, analysis of such measurements has assumed that infrared absorption is due to water and collagen. Such an assumption may be reasonable for soft tissue, but introduction of exogenous agents into skin or the measurement of tissue phantoms has raised the question of their infrared absorption spectrum. We used Fourier transform infrared spectroscopy in attenuated total reflection mode to measure the infrared absorption spectra, in the range of 2-15 μm, of water, polyacrylamide, Intralipid, collagen gels, four hyperosmotic clearing agents (glycerol, 1,3-butylene glycol, trimethylolpropane, Topicare TM ), and ex vivo human stratum corneum and dermis. The absorption spectra of the phantom materials were similar to that of water, although additional structure was noted in the range of 6-10 μm. The absorption spectra of the clearing agents were more complex, with molecular absorption bands dominating between 6 and 12 μm. Dermis was similar to water, with collagen structure evident in the 6-10 μm range. Stratum corneum had a significantly lower absorption than dermis due to a lower content of water. These results suggest that the assumption of water-dominated absorption in the 2.5-6 μm range is valid. At longer wavelengths, clearing agent absorption spectra differ significantly from the water spectrum. This spectral information can be used in pulsed photothermal radiometry or utilized in the interpretation of reconstructions in which a constant μ ir is used. In such cases, overestimating μ ir will underestimate chromophore depth and vice versa, although the effect is dependent on actual chromophore depth. (note)

  16. Editorial: New operational dose equivalent quantities

    International Nuclear Information System (INIS)

    Harvey, J.R.

    1985-01-01

    The ICRU Report 39 entitled ''Determination of Dose Equivalents Resulting from External Radiation Sources'' is briefly discussed. Four new operational dose equivalent quantities have been recommended in ICRU 39. The 'ambient dose equivalent' and the 'directional dose equivalent' are applicable to environmental monitoring and the 'individual dose equivalent, penetrating' and the 'individual dose equivalent, superficial' are applicable to individual monitoring. The quantities should meet the needs of day-to-day operational practice, while being acceptable to those concerned with metrological precision, and at the same time be used to give effective control consistent with current perceptions of the risks associated with exposure to ionizing radiations. (U.K.)

  17. Foreword: Biomonitoring Equivalents special issue.

    Science.gov (United States)

    Meek, M E; Sonawane, B; Becker, R A

    2008-08-01

    The challenge of interpreting results of biomonitoring for environmental chemicals in humans is highlighted in this Foreword to the Biomonitoring Equivalents (BEs) special issue of Regulatory Toxicology and Pharmacology. There is a pressing need to develop risk-based tools in order to empower scientists and health professionals to interpret and communicate the significance of human biomonitoring data. The BE approach, which integrates dosimetry and risk assessment methods, represents an important advancement on the path toward achieving this objective. The articles in this issue, developed as a result of an expert panel meeting, present guidelines for derivation of BEs, guidelines for communication using BEs and several case studies illustrating application of the BE approach for specific substances.

  18. Radiological equivalent of chemical pollutants

    International Nuclear Information System (INIS)

    Medina, V.O.

    1982-01-01

    The development of the peaceful uses of nuclear energy has caused continued effort toward public safety through radiation health protection measures and nuclear management practices. However, concern has not been focused on the development specifically in the operation of chemical pestrochemical industries as well as other industrial processes brought about by technological advancements. This article presents the comparison of the risk of radiation and chemicals. The methods used for comparing the risks of late effects of radiation and chemicals are considered at three levels. (a) as a frame of reference to give an impression of resolving power of biological tests; (b) as methods to quantify risks; (c) as instruments for an epidemiological survey of human populations. There are marked dissimilarities between chemicals and radiation and efforts to interpret chemical activity may not be achieved. Applicability of the concept of rad equivalence has many restrictions and as pointed out this approach is not an established one. (RTD)

  19. Expanding the Interaction Equivalency Theorem

    Directory of Open Access Journals (Sweden)

    Brenda Cecilia Padilla Rodriguez

    2015-06-01

    Full Text Available Although interaction is recognised as a key element for learning, its incorporation in online courses can be challenging. The interaction equivalency theorem provides guidelines: Meaningful learning can be supported as long as one of three types of interactions (learner-content, learner-teacher and learner-learner is present at a high level. This study sought to apply this theorem to the corporate sector, and to expand it to include other indicators of course effectiveness: satisfaction, knowledge transfer, business results and return on expectations. A large Mexican organisation participated in this research, with 146 learners, 30 teachers and 3 academic assistants. Three versions of an online course were designed, each emphasising a different type of interaction. Data were collected through surveys, exams, observations, activity logs, think aloud protocols and sales records. All course versions yielded high levels of effectiveness, in terms of satisfaction, learning and return on expectations. Yet, course design did not dictate the types of interactions in which students engaged within the courses. Findings suggest that the interaction equivalency theorem can be reformulated as follows: In corporate settings, an online course can be effective in terms of satisfaction, learning, knowledge transfer, business results and return on expectations, as long as (a at least one of three types of interaction (learner-content, learner-teacher or learner-learner features prominently in the design of the course, and (b course delivery is consistent with the chosen type of interaction. Focusing on only one type of interaction carries a high risk of confusion, disengagement or missed learning opportunities, which can be managed by incorporating other forms of interactions.

  20. Equivalent damage of loads on pavements

    CSIR Research Space (South Africa)

    Prozzi, JA

    2009-05-26

    Full Text Available This report describes a new methodology for the determination of Equivalent Damage Factors (EDFs) of vehicles with multiple axle and wheel configurations on pavements. The basic premise of this new procedure is that "equivalent pavement response...

  1. Investigation of Equivalent Circuit for PEMFC Assessment

    International Nuclear Information System (INIS)

    Myong, Kwang Jae

    2011-01-01

    Chemical reactions occurring in a PEMFC are dominated by the physical conditions and interface properties, and the reactions are expressed in terms of impedance. The performance of a PEMFC can be simply diagnosed by examining the impedance because impedance characteristics can be expressed by an equivalent electrical circuit. In this study, the characteristics of a PEMFC are assessed using the AC impedance and various equivalent circuits such as a simple equivalent circuit, equivalent circuit with a CPE, equivalent circuit with two RCs, and equivalent circuit with two CPEs. It was found in this study that the characteristics of a PEMFC could be assessed using impedance and an equivalent circuit, and the accuracy was highest for an equivalent circuit with two CPEs

  2. 46 CFR 175.540 - Equivalents.

    Science.gov (United States)

    2010-10-01

    ... Safety Management (ISM) Code (IMO Resolution A.741(18)) for the purpose of determining that an equivalent... Organization (IMO) “Code of Safety for High Speed Craft” as an equivalent to compliance with applicable...

  3. Verification of an effective dose equivalent model for neutrons

    International Nuclear Information System (INIS)

    Tanner, J.E.; Piper, R.K.; Leonowich, J.A.; Faust, L.G.

    1992-01-01

    Since the effective dose equivalent, based on the weighted sum of organ dose equivalents, is not a directly measurable quantity, it must be estimated with the assistance of computer modelling techniques and a knowledge of the incident radiation field. Although extreme accuracy is not necessary for radiation protection purposes, a few well chosen measurements are required to confirm the theoretical models. Neutron doses and dose equivalents were measured in a RANDO phantom at specific locations using thermoluminescence dosemeters, etched track dosemeters, and a 1.27 cm (1/2 in) tissue-equivalent proportional counter. The phantom was exposed to a bare and a D 2 O-moderated 252 Cf neutron source at the Pacific Northwest Laboratory's Low Scatter Facility. The Monte Carlo code MCNP with the MIRD-V mathematical phantom was used to model the human body and to calculate the organ doses and dose equivalents. The experimental methods are described and the results of the measurements are compared with the calculations. (author)

  4. Verification of an effective dose equivalent model for neutrons

    International Nuclear Information System (INIS)

    Tanner, J.E.; Piper, R.K.; Leonowich, J.A.; Faust, L.G.

    1991-10-01

    Since the effective dose equivalent, based on the weighted sum of organ dose equivalents, is not a directly measurable quantity, it must be estimated with the assistance of computer modeling techniques and a knowledge of the radiation field. Although extreme accuracy is not necessary for radiation protection purposes, a few well-chosen measurements are required to confirm the theoretical models. Neutron measurements were performed in a RANDO phantom using thermoluminescent dosemeters, track etch dosemeters, and a 1/2-in. (1.27-cm) tissue equivalent proportional counter in order to estimate neutron doses and dose equivalents within the phantom at specific locations. The phantom was exposed to bare and D 2 O-moderated 252 Cf neutrons at the Pacific Northwest Laboratory's Low Scatter Facility. The Monte Carlo code MCNP with the MIRD-V mathematical phantom was used to model the human body and calculate organ doses and dose equivalents. The experimental methods are described and the results of the measurements are compared to the calculations. 8 refs., 3 figs., 3 tabs

  5. Committed dose equivalent in the practice of radiological protection

    International Nuclear Information System (INIS)

    Nenot, J.C.; Piechowski, J.

    1985-01-01

    In the case of internal exposure, the dose is not received at the moment of exposure, as happens with external exposure, since the incorporated radionuclide irradiates the various organs and tissues during the time it is present in the body. By definition, the committed dose equivalent corresponds to the received dose integrated over 50 years from the date of intake. In order to calculate it, one has to know the intake activity and the value of the committed dose equivalent per unit of intake activity. The uncertainties of the first parameter are such that the committed dose equivalent can only be regarded as an order of magnitude and not as a very accurate quantity. The use of it is justified, however, for, like the dose equivalent for external exposure, it expresses the risk of stochastic effects for the individual concerned since these effects, should they appear, would do so only after a latent period which is generally longer than the dose integration time. Moreover, the use of the committed dose equivalent offers certain advantages for dosimetric management, especially when it is simplified. A practical problem which may arise is that the annual dose limit is apparently exceeded by virtue of the fact that one is taking account, in the first year, of doses which will actually be received only in the following years. These problems are rare enough in practice to be dealt with individually in each case. (author)

  6. Preclinical study of SZ2080 material 3D microstructured scaffolds for cartilage tissue engineering made by femtosecond direct laser writing lithography

    International Nuclear Information System (INIS)

    Mačiulaitis, Justinas; Darinskas, Adas; Šimbelytė, Agnė; Mačiulaitis, Romaldas; Deveikytė, Milda; Rekštytė, Sima; Malinauskas, Mangirdas; Bratchikov, Maksim; Daunoras, Gintaras; Laurinavičienė, Aida; Laurinavičius, Arvydas; Gudas, Rimtautas

    2015-01-01

    Over the last decade DLW employing ultrafast pulsed lasers has become a well-established technique for the creation of custom-made free-form three-dimensional (3D) microscaffolds out of a variety of materials ranging from proteins to biocompatible glasses. Its potential applications for manufacturing a patient’s specific scaffold seem unlimited in terms of spatial resolution and geometry complexity. However, despite few exceptions in which live cells or primitive organisms were encapsulated into a polymer matrix, no demonstration of an in vivo study case of scaffolds generated with the use of such a method was performed. Here, we report a preclinical study of 3D artificial microstructured scaffolds out of hybrid organic-inorganic (HOI) material SZ2080 fabricated using the DLW technique. The created 2.1 × 2.1 × 0.21 mm 3 membrane constructs are tested both in vitro by growing isolated allogeneic rabbit chondrocytes (Cho) and in vivo by implanting them into rabbit organisms for one, three and six months. An ex vivo histological examination shows that certain pore geometry and the pre-growing of Cho prior to implantation significantly improves the performance of the created 3D scaffolds. The achieved biocompatibility is comparable to the commercially available collagen membranes. The successful outcome of this study supports the idea that hexagonal-pore-shaped HOI microstructured scaffolds in combination with Cho seeding may be successfully implemented for cartilage tissue engineering. (paper)

  7. Evaluation of the in vitro biocompatibility of polymeric materials for the regeneration of cutaneous tissue; Evaluacion de la biocompatibilidad in vitro de materiales polimericos para la regeneracion de tejido cutaneo

    Energy Technology Data Exchange (ETDEWEB)

    Escudero Castellanos, A.

    2016-07-01

    The problems associated with medical cases of functional tissue loss or organ failure are destructive and expensive, even more frequent than could be perceived, sometime if not properly treated, even deathly. Tissue engineering is an interdisciplinary field that emerged to address these clinical problems, it is based on researching and development of biomaterials that have evolved along with areas such as cell biology, molecular and materials science and engineering. Today, the technique is based on seeding cells onto prefabricated scaffold biomaterials, like the hydrogels, that are three-dimensional networks with hydrophilic properties. These materials are characterized as being porous and sticky, favoring the support for the proliferation of certain cells in order to lead the regeneration of injured tissue. As a prerequisite for the use of materials in tissue engineering is testing biocompatibility which is the ability of the bio material to allow contact with any tissue, existing a favorable host response, accepting it as their own and restoring previously lost function. The first step for evaluating biocompatibility is to perform the in vitro assays. These assays have been demonstrated more reproducibility and predictability than in vivo assays, therefore the in vitro assays are used to produce high quality scaffolds and testing on animals as less as possible. This test is essential to establish the benefits and limitations of biomaterials tested in order to improve the scaffolds. This work will focus on assessing the biocompatibility of three polymeric materials with potential use in tissue engineering by means of cytological compatibility tests and hemo compatibility tests. Furthermore, disinfection techniques and gamma sterilization were evaluated to produce sterile materials that can be used in tissue engineering. (Author)

  8. A Histologic Evaluation on Tissue Reaction to Three Implanted Materials (MTA, Root MTA and Portland Cement Type I in the Mandible of Cats

    Directory of Open Access Journals (Sweden)

    F. Sasani

    2004-09-01

    Full Text Available Statement of Problem: Nowadays Mineral Trioxide aggregate (MTA is widely used for root end fillings, pulp capping, perforation repair and other endodontic treatments.Investigations have shown similar physical and chemical properties for Portland cement and Root MTA with those described for MTA.Purpose: The aim of this in vitro study was to evaluate the tissue reaction to implanted MTA, Portland cement and Root MTA in the mandible of cats.Materials and Methods: Under asepsis condition and general anesthesia, a mucoperiosteal flap, following the application of local anesthesia, was elevated to expose mandibular symphysis. Two small holes in both sides of mandible were drilled. MTA, Portland cement and Root MTA were mixed according to the manufacturers, recommendation and placed in bony cavities. In positive control group, the test material was Zinc oxide powder plus tricresoformalin. In negative control group, the bony cavities were left untreated. After 3,6 and 12 weeks, the animals were sacrificed and the mandibular sections were prepared for histologic examination under light microscope. The presence and thickness of inflammation, presence of fibrosis capsule, the severity of fibrosis and bone formation were investigated. The data were submitted to Exact Fisher test, chi square test and Kruskal-Wallis test for statistical analysis.Results: No statistically significant differences were found in the degree of inflammation,presence of fibrotic capsule, severity of fibrosis and inflammation thickness between Root MTA, Portland cement and MTA (P>0.05. There was no statistical difference in boneformation between MTA and Portland cement (P>0.05. However, bone formation was not found in any of the Root MTA specimens and the observed tissue was exclusively of fibrosis type.Conclusion: The physical and histological results observed with MTA are similar to those of Root MTA and Portland cement. Additionally, all of these three materials are biocompatible

  9. Some spectral equivalences between Schroedinger operators

    International Nuclear Information System (INIS)

    Dunning, C; Hibberd, K E; Links, J

    2008-01-01

    Spectral equivalences of the quasi-exactly solvable sectors of two classes of Schroedinger operators are established, using Gaudin-type Bethe ansatz equations. In some instances the results can be extended leading to full isospectrality. In this manner we obtain equivalences between PT-symmetric problems and Hermitian problems. We also find equivalences between some classes of Hermitian operators

  10. The definition of the individual dose equivalent

    International Nuclear Information System (INIS)

    Ehrlich, Margarete

    1986-01-01

    A brief note examines the choice of the present definition of the individual dose equivalent, the new operational dosimetry quantity for external exposure. The consequences of the use of the individual dose equivalent and the danger facing the individual dose equivalent, as currently defined, are briefly discussed. (UK)

  11. Combinational pixel-by-pixel and object-level classifying, segmenting, and agglomerating in performing quantitative image analysis that distinguishes between healthy non-cancerous and cancerous cell nuclei and delineates nuclear, cytoplasm, and stromal material objects from stained biological tissue materials

    Science.gov (United States)

    Boucheron, Laura E

    2013-07-16

    Quantitative object and spatial arrangement-level analysis of tissue are detailed using expert (pathologist) input to guide the classification process. A two-step method is disclosed for imaging tissue, by classifying one or more biological materials, e.g. nuclei, cytoplasm, and stroma, in the tissue into one or more identified classes on a pixel-by-pixel basis, and segmenting the identified classes to agglomerate one or more sets of identified pixels into segmented regions. Typically, the one or more biological materials comprises nuclear material, cytoplasm material, and stromal material. The method further allows a user to markup the image subsequent to the classification to re-classify said materials. The markup is performed via a graphic user interface to edit designated regions in the image.

  12. Influence of hydroxyapatite granule size, porosity, and crystallinity on tissue reaction in vivo. Part A: synthesis, characterization of the materials, and SEM analysis.

    Science.gov (United States)

    Maté Sánchez de Val, José E; Calvo-Guirado, José L; Gómez-Moreno, Gerardo; Pérez-Albacete Martínez, Carlos; Mazón, Patricia; De Aza, Piedad N

    2016-11-01

    The aim of this study was the synthesis and analysis of the tissue reaction to three different Hydroxyapatite (HA)-based bone substitute materials differing only in granule size, porosity, and crystallinity through an animal experimental model at 60 days. Three different HA-based biomaterials were synthesized and characterized by X-ray diffraction, SEM, and EDS analysis, the resultant product was ground in three particle sizes: Group I (2000-4000 μm), Group II (1000-2000 μm), and Group III (600-1000 μm). Critical size defects were created in both tibias of 15 rabbits. Four defects per rabbit for a total of 60 defects were grafted with the synthesized materials as follows: Group I (15 defects), Group II (15 defects), Group III (15 defects), and empty (15 defects control). After animals sacrifice at 60 days samples were obtained and processed for SEM and EDS evaluation of Ca/P ratios, elemental mapping was performed to determine the chemical degradation process and changes to medullary composition in all the four study groups. The tendency for the density was to increase with the increasing annealing temperature; in this way it was possible to observe that the sample that shows highest crystallinity and crystal size corresponding to that of group I. The SEM morphological examination showed that group III implant showed numerous resorption regions, group II implant presented an average resorption rate of all the implants. The group I displayed smoother surface features, in comparison with the other two implants. The data from this study show that changing the size, porosity, and crystallinity of one HA-based bone substitute material can influence the integration of the biomaterials within the implantation site and the new bone formation. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Physical and dosimetrical characterization of 4He and 16O beam interacting with tissue-like and candidates-shielding materials

    Science.gov (United States)

    La Tessa, Chiara; Zeitlin, Cary; Rusek, Adam; Durante, Marco; Schuy, Christoph; Sivertz, Michael

    2012-07-01

    The permanence of human in space has increased in the last decades with the establishment of space stations orbiting permanently around the Earth; furthermore, future plans are likely to include extended human missions in deep space outside the geomagnetosphere and settlements on other planets. The extensive exposure to the radiation environment represents one of the major limitations to space exploration due to its relation with severe health risks. The unfeasibility to stop the external radiation entirely motivates the investigation of shields able to minimize the total absorbed and equivalent dose to which the astronauts are exposed. The process of nuclear fragmentation plays a key role in this topic being the major responsible for modifying the radiation field that enters the spacecraft. Theoretical predictions on the dose received in a given scenario rely heavily on the accuracy of fragmentation cross sections and their uncertainties can be a central factor in limiting mission feasibility and duration. The interaction of 160 MeV/u Helium and 360 MeV/u Oxygen beams with water has been investigated in this work. The total charge-changing cross section has been estimated from the measurement of the attenuation of the primary ions in the target. For different target thicknesses, the yield and energy spectrum of charged and unchanged particles has been measured at several angles with respect to the primary beam direction. At the same position, microdosimetric spectra have been collected to characterize the quality of the radiation field and estimate the absorbed dose. Furthermore, total and partial-change-changing cross sections in candidate shielding materials are presented and compared with the results for water.

  14. A computerized system based on an alternative pulse echo immersion technique for acoustic characterization of non-porous solid tissue mimicking materials

    Science.gov (United States)

    Nazihah Mat Daud, Anis; Jaafar, Rosly; Kadri Ayop, Shahrul; Supar Rohani, Md

    2018-04-01

    This paper discusses the development of a computerized acoustic characterization system of non-porous solid tissue mimicking materials. This system employs an alternative pulse echo immersion technique and consists of a pulser/receiver generator, a transducer used as both a transmitter and a receiver, a digital oscilloscope, and a personal computer with a custom-developed program installed. The program was developed on the LabVIEW 2012 platform and comprises two main components, a user interface and a block diagram. The user interface consists of three panels: a signal acquisition and selection panel, a display panel, and a calculation panel. The block diagram comprises four blocks: a signal acquisition block, a peak signal analysis block, an acoustic properties calculation and display block, and an additional block. Interestingly, the system can be operated in both online and offline modes. For the online mode, the measurements are performed by connecting the system with a Rigol DS2000 Series digital oscilloscope. In contrast, the measurements are carried out by processing the saved data on the computer for the offline mode. The accuracy and consistency of the developed system was validated by a KB-Aerotech Alpha Series transducer with 5 MHz center frequency and a Rigol DS2202 two-channel 200 MHz 2 GSa s-1 digital oscilloscope, based on the measurement of the acoustic properties of three poly(methyl methacrylate) samples immersed in a medium at a temperature of (24.0  ±  0.1) °C. The findings indicated that the accuracy and consistency of the developed system was exceptionally high, within a 1.04% margin of error compared to the reference values. As such, this computerized system can be efficiently used for the acoustic characterization of non-porous solid tissues, given its spontaneous display of results, user-friendly interface, and convenient hardware connection.

  15. Tissue bionics: examples in biomimetic tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Green, David W [Bone and Joint Research Group, Developmental Origins of Health and Disease, General Hospital, University of Southampton, SO16 6YD (United Kingdom)], E-mail: Hindoostuart@googlemail.com

    2008-09-01

    Many important lessons can be learnt from the study of biological form and the functional design of organisms as design criteria for the development of tissue engineering products. This merging of biomimetics and regenerative medicine is termed 'tissue bionics'. Clinically useful analogues can be generated by appropriating, modifying and mimicking structures from a diversity of natural biomatrices ranging from marine plankton shells to sea urchin spines. Methods in biomimetic materials chemistry can also be used to fabricate tissue engineering scaffolds with added functional utility that promise human tissues fit for the clinic.

  16. Tissue bionics: examples in biomimetic tissue engineering

    International Nuclear Information System (INIS)

    Green, David W

    2008-01-01

    Many important lessons can be learnt from the study of biological form and the functional design of organisms as design criteria for the development of tissue engineering products. This merging of biomimetics and regenerative medicine is termed 'tissue bionics'. Clinically useful analogues can be generated by appropriating, modifying and mimicking structures from a diversity of natural biomatrices ranging from marine plankton shells to sea urchin spines. Methods in biomimetic materials chemistry can also be used to fabricate tissue engineering scaffolds with added functional utility that promise human tissues fit for the clinic

  17. Transport equivalent diffusion constants for reflector region in PWRs

    International Nuclear Information System (INIS)

    Tahara, Yoshihisa; Sekimoto, Hiroshi

    2002-01-01

    The diffusion-theory-based nodal method is widely used in PWR core designs for reason of its high computing speed in three-dimensional calculations. The baffle/reflector (B/R) constants used in nodal calculations are usually calculated based on a one-dimensional transport calculation. However, to achieve high accuracy of assembly power prediction, two-dimensional model is needed. For this reason, the method for calculating transport equivalent diffusion constants of reflector material was developed so that the neutron currents on the material boundaries could be calculated exactly in diffusion calculations. Two-dimensional B/R constants were calculated using the transport equivalent diffusion constants in the two-dimensional diffusion calculation whose geometry reflected the actual material configuration in the reflector region. The two-dimensional B/R constants enabled us to predict assembly power within an error of 1.5% at hot full power conditions. (author)

  18. Water-equivalence of gel dosimeters for radiology medical imaging

    International Nuclear Information System (INIS)

    Valente, M; Vedelago, J.; Perez, P.; Chacon, D.; Mattea, F.; Velasquez, J.

    2017-10-01

    International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography and high-resolution micro computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined by Monte Carlo simulations. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 k Vp) were found to be less than 3% in average. (Author)

  19. Water-equivalence of gel dosimeters for radiology medical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Valente, M; Vedelago, J.; Perez, P. [Instituto de Fisica Enrique Gaviola - CONICET, Av. Medina Allende s/n, Ciudad Universitaria, X5000HUA, Cordoba (Argentina); Chacon, D.; Mattea, F. [Universidad Nacional de Cordoba, FAMAF, Laboratorio de Investigacion e Instrumentacion en Fisica Aplicada a la Medicina e Imagenes por Rayos X, Av. Medina Allende s/n, Ciudad Universitaria, X5000HUA Cordoba (Argentina); Velasquez, J., E-mail: valente@famaf.unc.edu.ar [ICOS Inmunomedica, Lago Puyehue 01745, Temuco (Chile)

    2017-10-15

    International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography and high-resolution micro computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined by Monte Carlo simulations. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 k Vp) were found to be less than 3% in average. (Author)

  20. Degradation and in vitro cell–material interaction studies on hydroxyapatite-coated biodegradable porous iron for hard tissue scaffolds

    Directory of Open Access Journals (Sweden)

    Nurizzati Mohd Daud

    2014-10-01

    Full Text Available This paper describes degradation and cell–material interaction studies on hydroxyapatite (HA-coated biodegradable porous iron proposed for hard tissue scaffolds. Porous iron scaffolds are expected to serve as an ideal platform for bone regeneration. To couple their inherent mechanical strength, pure HA and HA/poly(ε-caprolactone (HA/PCL were coated onto porous iron using dip coating technique. The HA/PCL mixture was prepared to provide a more stable and flexible coating than HA alone. Degradation of the samples was evaluated by weight loss and potentiodynamic polarisation. Human skin fibroblast (HSF and human mesenchymal stem cells (hMSC were put in contact with the samples and their interaction was observed. Results showed that coated samples degraded ∼10 times slower (0.002 mm/year for HA/PCL-Fe, 0.003 mm/year for HA-Fe than the uncoated ones (0.031 mm/year, indicating an inhibition effect of the coating on degradation. Both HSF and hMSC maintained high viability when in contact with the coated samples (100–110% control for hMSC during 2–5 days of incubation, indicating the effect of HA in enhancing cytocompatibility of the surface. This study provided early evidence of the potential translation of biodegradable porous iron scaffolds for clinical use in orthopedic surgery. However, further studies including in vitro and in vivo tests are necessary.

  1. Strain Rockbursts Simulated by Low-Strength Brittle Equivalent Materials

    Directory of Open Access Journals (Sweden)

    Lang Li

    2016-01-01

    Full Text Available This paper presents experimental study on rockbursts that occur in deep underground excavations. To begin with, the boundary conditions for excavation in deep underground engineering were analysed and elastic adaptive boundary is an effective way to minimize the boundary effect of geomechanical model test. Then, in order to simulate an elastic adaptive loading boundary, Belleville springs were used to establish this loading boundary. With the aforementioned experimental set-ups and fabrication of similarity models for test, the phenomena of strain mode rockbursts were satisfactorily reproduced in laboratory. The internal stress, strain, and convergences of the openings of the model were instrumented by subtly preembedded sensors and transducers. Test results showed that, with an initial state of high stress from both upper layers’ gravitational effects and in situ stress due to tectonic movements, the excavation brings a dramatic rise in the hoop stress and sharp drop in radial stress, which leads to the splitting failure of rock mass. Finally a rockburst occurred associated with the release of strain energy stored in highly stressed rock mass. In addition, the failure of the surrounding rock demonstrated an obvious hysteresis effect which supplies valuable guide and reference for tunnel support. Not only do these results provide a basis for further comprehensive experiments, but also the data can offer assisting aids for further theoretical study of rockbursts.

  2. Equivalence relations for the 9972-9975 SARP

    International Nuclear Information System (INIS)

    Niemer, K.A.; Frost, R.L.

    1994-10-01

    Equivalence relations required to determine mass limits for mixtures of nuclides for the Safety Analysis Report for Packaging (SARP) of the Savannah River Site 9972, 9973, 9974, and 9975 shipping casks were calculated. The systems analyzed included aqueous spheres, homogeneous metal spheres, and metal ball-and-shell configurations, all surrounded by an effectively infinite stainless steel or water reflector. Comparison of the equivalence calculations with the rule-of-fractions showed conservative agreement for aqueous solutions, both conservative and non-conservative agreement for the metal homogeneous sphere systems, and non-conservative agreement for the majority of metal ball-and-shell systems. Equivalence factors for the aqueous solutions and homogeneous metal spheres were calculated. The equivalence factors for the non-conservative metal homogeneous sphere systems were adjusted so that they were conservative. No equivalence factors were calculated for the ball-and-shell systems since the -SARP assumes that only homogeneous or uniformly distributed material will be shipped in the 9972-9975 shipping casks, and an unnecessarily conservative critical mass may result if the ball-and-shell configurations are included

  3. Application of A150-plastic equivalent gases in microdosimetric measurements

    International Nuclear Information System (INIS)

    DeLuca, P.M. Jr.; Higgins, P.D.; Pearson, D.W.; Schell, M.; Attix, F.H.

    1981-01-01

    Neutron dosimetry measurements with ionization chambers, for the most part, employ tissue equivalent plastic-walled cavities (Shonka A150) filled with either air or a methane-base tissue-like gas. The atomic composition of TE-gas and A150 plastic are not matched and are quite dissimilar from muscle. Awschalom and Attix (1980) have partially resolved the problem by formulating a novel A150-plastic equivalent gas. This establishes a homogeneous wall-gas cavity dosimeter for neutron measurements and confines the necessary corrections to the applications of kerma ratios. In this report, we present measurements of applications of two A150-plastic equivalent gases in a low pressure spherical proportional counter. Gas gains and alpha-particle resolutions were determined. For these A150-mixtures as well as a methane-based TE-gas and an Ar-CO 2 mixture, we report measurements of event size distributions from exposure to a beam of 14.8 MeV neutrons

  4. The Complexity of Identifying Large Equivalence Classes

    DEFF Research Database (Denmark)

    Skyum, Sven; Frandsen, Gudmund Skovbjerg; Miltersen, Peter Bro

    1999-01-01

    We prove that at least 3k−4/k(2k−3)(n/2) – O(k)equivalence tests and no more than 2/k (n/2) + O(n) equivalence tests are needed in the worst case to identify the equivalence classes with at least k members in set of n elements. The upper bound is an improvement by a factor 2 compared to known res...

  5. Equivalent Simplification Method of Micro-Grid

    OpenAIRE

    Cai Changchun; Cao Xiangqin

    2013-01-01

    The paper concentrates on the equivalent simplification method for the micro-grid system connection into distributed network. The equivalent simplification method proposed for interaction study between micro-grid and distributed network. Micro-grid network, composite load, gas turbine synchronous generation, wind generation are equivalent simplification and parallel connect into the point of common coupling. A micro-grid system is built and three phase and single phase grounded faults are per...

  6. Calculation methods for determining dose equivalent

    International Nuclear Information System (INIS)

    Endres, G.W.R.; Tanner, J.E.; Scherpelz, R.I.; Hadlock, D.E.

    1988-01-01

    A series of calculations of neutron fluence as a function of energy in an anthropomorphic phantom was performed to develop a system for determining effective dose equivalent for external radiation sources. critical organ dose equivalents are calculated and effective dose equivalents are determined using ICRP-26 methods. Quality factors based on both present definitions and ICRP-40 definitions are used in the analysis. The results of these calculations are presented and discussed

  7. Equivalences of real submanifolds in complex space.

    OpenAIRE

    ZAITSEV, DMITRI

    2001-01-01

    PUBLISHED We show that for any real-analytic submanifold M in CN there is a proper real-analytic subvariety V contained in M such that for any p ? M \\ V , any real-analytic submanifold M? in CN, and any p? ? M?, the germs of the submanifolds M and M? at p and p? respectively are formally equivalent if and only if they are biholomorphically equivalent. More general results for k-equivalences are also stated and proved.

  8. Relations of equivalence of conditioned radioactive waste

    International Nuclear Information System (INIS)

    Kumer, L.; Szeless, A.; Oszuszky, F.

    1982-01-01

    A compensation for the wastes remaining with the operator of a waste management center, to be given by the agent having caused the waste, may be assured by effecting a financial valuation (equivalence) of wastes. Technically and logically, this equivalence between wastes (or specifically between different waste categories) and financial valuation has been established as reasonable. In this paper, the possibility of establishing such equivalences are developed, and their suitability for waste management concepts is quantitatively expressed

  9. Behavioural equivalence for infinite systems - Partially decidable!

    DEFF Research Database (Denmark)

    Sunesen, Kim; Nielsen, Mogens

    1996-01-01

    languages with two generalizations based on traditional approaches capturing non-interleaving behaviour, pomsets representing global causal dependency, and locality representing spatial distribution of events. We first study equivalences on Basic Parallel Processes, BPP, a process calculus equivalent...... of processes between BPP and TCSP, not only are the two equivalences different, but one (locality) is decidable whereas the other (pomsets) is not. The decidability result for locality is proved by a reduction to the reachability problem for Petri nets....

  10. Equivalence in Bilingual Lexicography: Criticism and Suggestions*

    Directory of Open Access Journals (Sweden)

    Herbert Ernst Wiegand

    2011-10-01

    Full Text Available

    Abstract: A reminder of general problems in the formation of terminology, as illustrated by theGerman Äquivalence (Eng. equivalence and äquivalent (Eng. equivalent, is followed by a critical discussionof the concept of equivalence in contrastive lexicology. It is shown that especially the conceptof partial equivalence is contradictory in its different manifestations. Consequently attemptsare made to give a more precise indication of the concept of equivalence in the metalexicography,with regard to the domain of the nominal lexicon. The problems of especially the metalexicographicconcept of partial equivalence as well as that of divergence are fundamentally expounded.In conclusion the direction is indicated to find more appropriate metalexicographic versions of theconcept of equivalence.

    Keywords: EQUIVALENCE, LEXICOGRAPHIC EQUIVALENT, PARTIAL EQUIVALENCE,CONGRUENCE, DIVERGENCE, CONVERGENCE, POLYDIVERGENCE, SYNTAGM-EQUIVALENCE,ZERO EQUIVALENCE, CORRESPONDENCE

    Abstrakt: Äquivalenz in der zweisprachigen Lexikographie: Kritik und Vorschläge.Nachdem an allgemeine Probleme der Begriffsbildung am Beispiel von dt. Äquivalenzund dt. äquivalent erinnert wurde, wird zunächst auf Äquivalenzbegriffe in der kontrastiven Lexikologiekritisch eingegangen. Es wird gezeigt, dass insbesondere der Begriff der partiellen Äquivalenzin seinen verschiedenen Ausprägungen widersprüchlich ist. Sodann werden Präzisierungenzu den Äquivalenzbegriffen in der Metalexikographie versucht, die sich auf den Bereich der Nennlexikbeziehen. Insbesondere der metalexikographische Begriff der partiellen Äquivalenz sowie derder Divergenz werden grundsätzlich problematisiert. In welche Richtung man gehen kann, umangemessenere metalexikographische Fassungen des Äquivalenzbegriffs zu finden, wird abschließendangedeutet.

    Stichwörter: ÄQUIVALENZ, LEXIKOGRAPHISCHES ÄQUIVALENT, PARTIELLE ÄQUIVALENZ,KONGRUENZ, DIVERGENZ, KONVERGENZ, POLYDIVERGENZ

  11. Supplementary Material for: Global expression differences and tissue specific expression differences in rice evolution result in two contrasting types of differentially expressed genes

    KAUST Repository

    Horiuchi, Youko; Harushima, Yoshiaki; Fujisawa, Hironori; Mochizuki, Takako; Fujita, Masahiro; Ohyanagi, Hajime; Kurata, Nori

    2015-01-01

    Abstract Background Since the development of transcriptome analysis systems, many expression evolution studies characterized evolutionary forces acting on gene expression, without explicit discrimination between global expression differences and tissue specific expression differences. However, different types of gene expression alteration should have different effects on an organism, the evolutionary forces that act on them might be different, and different types of genes might show different types of differential expression between species. To confirm this, we studied differentially expressed (DE) genes among closely related groups that have extensive gene expression atlases, and clarified characteristics of different types of DE genes including the identification of regulating loci for differential expression using expression quantitative loci (eQTL) analysis data. Results We detected differentially expressed (DE) genes between rice subspecies in five homologous tissues that were verified using japonica and indica transcriptome atlases in public databases. Using the transcriptome atlases, we classified DE genes into two types, global DE genes and changed-tissues DE genes. Global type DE genes were not expressed in any tissues in the atlas of one subspecies, however changed-tissues type DE genes were expressed in both subspecies with different tissue specificity. For the five tissues in the two japonica-indica combinations, 4.6 ± 0.8 and 5.9 ± 1.5 % of highly expressed genes were global and changed-tissues DE genes, respectively. Changed-tissues DE genes varied in number between tissues, increasing linearly with the abundance of tissue specifically expressed genes in the tissue. Molecular evolution of global DE genes was rapid, unlike that of changed-tissues DE genes. Based on gene ontology, global and changed-tissues DE genes were different, having no common GO terms. Expression differences of most global DE genes were regulated by cis

  12. Development of an experimental method for the determination of the dose equivalent indices for low - and medium energy X- and gamma rays

    International Nuclear Information System (INIS)

    Silva Estrada, J.J. da.

    1980-01-01

    An experimental method was developed to measure Dose Equivalent Indices for low and medium energy X-rays. A sphere was constructed to simulate the human body in accordance with ICRU Report 19 but using plexiglass instead of tissue equivalent material of density 1 g.cm -3 . Experimentally it was demonstrated that for the purpose of applied radiation protection both materials are equivalent in spite of a 18% higher density of plexiglass. CaF 2 :Mn and LiF:Mg might be utilized to determine the absorbed dose distribution within the sphere. Measurements indicate that the effective energy can be determined with an accuracy better than 15% for the energy range under consideration. Depth dose curves measured with ionization chamber compared with those of LiF:Mg showed an agreement better than 12% and in the case of CaF 2 :Mn better than 11% for all irradiation conditions used. Conversion factors in units rad R -1 measured with TLD and compared with those obtained from the literature based upon Monte Carlo calculation showed an agreement better than 23% for CaF 2 :Mn and 19% for LiF:Mg. It is concluded from these experiments that the system plexiglass sphere-TLD dosimeters might be used to measure Dose Equivalent Indices for low and medium energy photons. (Author) [pt

  13. Degradable polymers for tissue engineering

    NARCIS (Netherlands)

    van Dijkhuizen-Radersma, Riemke; Moroni, Lorenzo; van Apeldoorn, Aart A.; Zhang, Zheng; Grijpma, Dirk W.; van Blitterswijk, Clemens A.

    2008-01-01

    This chapter elaborates the degradable polymers for tissue engineering and their required scaffold material in tissue engineering. It recognizes the examples of degradable polymers broadly used in tissue engineering. Tissue engineering is the persuasion of the body to heal itself through the

  14. The Medial Stitch in Transosseous-Equivalent Rotator Cuff Repair: Vertical or Horizontal Mattress?

    Science.gov (United States)

    Montanez, Anthony; Makarewich, Christopher A; Burks, Robert T; Henninger, Heath B

    2016-09-01

    Despite advances in surgical technique, rotator cuff repair retears continue to occur at rates of 10%, 22%, and 57% for small, medium, and large tears, respectively. A common mode of failure in transosseous-equivalent rotator cuff repairs is tissue pullout of the medial mattress stitch. While the medial mattress stitch has been studied extensively, no studies have evaluated a vertical mattress pattern placed near the musculotendinous junction in comparison with a horizontal mattress pattern. Vertical mattress stitches will have higher load to failure and lower gapping compared with horizontal mattress stitches in a transosseous-equivalent rotator cuff repair. Controlled laboratory study. Double-row transosseous-equivalent rotator cuff repairs were performed in 9 pairs of human male cadaveric shoulders (mean age ± SD, 58 ± 10 years). One shoulder in each pair received a medial-row suture pattern using a vertical mattress stitch, and the contralateral shoulder received a horizontal mattress. Specimens were mounted in a materials testing machine and tested in uniaxial tensile deformation for cyclic loading (500 cycles at 1 Hz to 1.0 MPa of effective stress), followed by failure testing carried out at a rate of 1 mm/s. Construct gapping and applied loads were monitored continuously throughout the testing. Vertical mattress sutures were placed in 5 right and 4 left shoulders. Peak cyclic gapping did not differ between vertical (mean ± SD, 2.8 ± 1.1 mm) and horizontal mattress specimens (3.0 ± 1.2 mm) (P = .684). Vertical mattress sutures failed at higher loads compared with horizontal mattress sutures (568.9 ± 140.3 vs 451.1 ± 174.3 N; P = .025); however, there was no significant difference in failure displacement (8.0 ± 1.6 vs 6.0 ± 2.1 mm; P = .092). Failure stiffness did not differ between the suture patterns (P = .204). In transosseous-equivalent rotator cuff repairs near the musculotendinous junction, a vertical mattress suture used as the medial stitch

  15. Testing the equivalence principle on a trampoline

    Science.gov (United States)

    Reasenberg, Robert D.; Phillips, James D.

    2001-07-01

    We are developing a Galilean test of the equivalence principle in which two pairs of test mass assemblies (TMA) are in free fall in a comoving vacuum chamber for about 0.9 s. The TMA are tossed upward, and the process repeats at 1.2 s intervals. Each TMA carries a solid quartz retroreflector and a payload mass of about one-third of the total TMA mass. The relative vertical motion of the TMA of each pair is monitored by a laser gauge working in an optical cavity formed by the retroreflectors. Single-toss precision of the relative acceleration of a single pair of TMA is 3.5×10-12 g. The project goal of Δg/g = 10-13 can be reached in a single night's run, but repetition with altered configurations will be required to ensure the correction of systematic error to the nominal accuracy level. Because the measurements can be made quickly, we plan to study several pairs of materials.

  16. Composition variability and equivalence of Shonka TE plastic

    International Nuclear Information System (INIS)

    Spokas, J.J.

    1973-01-01

    A number of conducting plastic mixtures had been developed by Francis R. Shonka, and collaborators, in the Physical Sciences Laboratory of Illinois Benedictine College (formerly St. Procopius College). Several of these mixtures have been used widely in radiation research. In particular, a tissue-equivalent (muscle) formulation designated A-150 has been used extensively in the dosimetry, research and measurements of gamma, neutron and pion beams. Certain confusion has arisen concerning the composition of A-150. The definition of A-150 is reviewed and what is known of the composition is summarized. The equivalence of A-150 and ICRU ''muscle'' with respect to photons is discussed as a function of photon energy using the latest data on extra-nuclear photon cross sections. (U.S.)

  17. Validity of the Aluminum Equivalent Approximation in Space Radiation Shielding

    Science.gov (United States)

    Badavi, Francis F.; Adams, Daniel O.; Wilson, John W.

    2009-01-01

    The origin of the aluminum equivalent shield approximation in space radiation analysis can be traced back to its roots in the early years of the NASA space programs (Mercury, Gemini and Apollo) wherein the primary radiobiological concern was the intense sources of ionizing radiation causing short term effects which was thought to jeopardize the safety of the crew and hence the mission. Herein, it is shown that the aluminum equivalent shield approximation, although reasonably well suited for that time period and to the application for which it was developed, is of questionable usefulness to the radiobiological concerns of routine space operations of the 21 st century which will include long stays onboard the International Space Station (ISS) and perhaps the moon. This is especially true for a risk based protection system, as appears imminent for deep space exploration where the long-term effects of Galactic Cosmic Ray (GCR) exposure is of primary concern. The present analysis demonstrates that sufficiently large errors in the interior particle environment of a spacecraft result from the use of the aluminum equivalent approximation, and such approximations should be avoided in future astronaut risk estimates. In this study, the aluminum equivalent approximation is evaluated as a means for estimating the particle environment within a spacecraft structure induced by the GCR radiation field. For comparison, the two extremes of the GCR environment, the 1977 solar minimum and the 2001 solar maximum, are considered. These environments are coupled to the Langley Research Center (LaRC) deterministic ionized particle transport code High charge (Z) and Energy TRaNsport (HZETRN), which propagates the GCR spectra for elements with charges (Z) in the range I aluminum equivalent approximation for a good polymeric shield material such as genetic polyethylene (PE). The shield thickness is represented by a 25 g/cm spherical shell. Although one could imagine the progression to greater

  18. Conversion of ionization measurements to radiation absorbed dose in non-water density material

    International Nuclear Information System (INIS)

    El-Khatib, E.; Connors, S.

    1992-01-01

    In bone-equivalent materials two different calculations of absorbed dose are possible: the absorbed dose to soft tissue plastic (polystyrene) within bone-equivalent material and the dose to the bone-equivalent material itself. Both can be calculated from ionization measurements in phantoms. These two calculations result in significantly different doses in a heterogeneous phantom composed of polystyrene and aluminium (a bone substitute). The dose to a thin slab of polystyrene in aluminium is much higher than the dose to the aluminium itself at the same depth in the aluminium. Monte Carlo calculations confirm that the calculation of dose to polystyrene in aluminium can be accurately carried out using existing dosimetry protocols. However, the conversion of ionization measurements to absorbed dose to high atomic number materials cannot be accurately carried out with existing protocols and appropriate conversion factors need to be determined. (author)

  19. Orientifold Planar Equivalence: The Chiral Condensate

    DEFF Research Database (Denmark)

    Armoni, Adi; Lucini, Biagio; Patella, Agostino

    2008-01-01

    The recently introduced orientifold planar equivalence is a promising tool for solving non-perturbative problems in QCD. One of the predictions of orientifold planar equivalence is that the chiral condensates of a theory with $N_f$ flavours of Dirac fermions in the symmetric (or antisymmetric...

  20. 7 CFR 1005.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1005.54 Section 1005.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1005.54 Equivalent price. See § 1000.54. Uniform Prices ...

  1. 7 CFR 1126.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1126.54 Section 1126.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1126.54 Equivalent price. See § 1000.54. Producer Price Differential ...

  2. 7 CFR 1001.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1001.54 Section 1001.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1001.54 Equivalent price. See § 1000.54. Producer Price Differential ...

  3. 7 CFR 1032.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1032.54 Section 1032.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1032.54 Equivalent price. See § 1000.54. Producer Price Differential ...

  4. 7 CFR 1124.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1124.54 Section 1124.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Regulating Handling Class Prices § 1124.54 Equivalent price. See § 1000.54. Producer Price Differential ...

  5. 7 CFR 1030.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1030.54 Section 1030.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1030.54 Equivalent price. See § 1000.54. ...

  6. 7 CFR 1033.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1033.54 Section 1033.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1033.54 Equivalent price. See § 1000.54. Producer Price Differential ...

  7. 7 CFR 1131.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1131.54 Section 1131.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1131.54 Equivalent price. See § 1000.54. Uniform Prices ...

  8. 7 CFR 1006.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1006.54 Section 1006.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1006.54 Equivalent price. See § 1000.54. Uniform Prices ...

  9. 7 CFR 1007.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1007.54 Section 1007.54 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... Handling Class Prices § 1007.54 Equivalent price. See § 1000.54. Uniform Prices ...

  10. 7 CFR 1000.54 - Equivalent price.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 9 2010-01-01 2009-01-01 true Equivalent price. 1000.54 Section 1000.54 Agriculture... Prices § 1000.54 Equivalent price. If for any reason a price or pricing constituent required for computing the prices described in § 1000.50 is not available, the market administrator shall use a price or...

  11. Finding small equivalent decision trees is hard

    NARCIS (Netherlands)

    Zantema, H.; Bodlaender, H.L.

    2000-01-01

    Two decision trees are called decision equivalent if they represent the same function, i.e., they yield the same result for every possible input. We prove that given a decision tree and a number, to decide if there is a decision equivalent decision tree of size at most that number is NPcomplete. As

  12. What is Metaphysical Equivalence? | Miller | Philosophical Papers

    African Journals Online (AJOL)

    Theories are metaphysically equivalent just if there is no fact of the matter that could render one theory true and the other false. In this paper I argue that if we are judiciously to resolve disputes about whether theories are equivalent or not, we need to develop testable criteria that will give us epistemic access to the obtaining ...

  13. EQUIVALENT MODELS IN COVARIANCE STRUCTURE-ANALYSIS

    NARCIS (Netherlands)

    LUIJBEN, TCW

    1991-01-01

    Defining equivalent models as those that reproduce the same set of covariance matrices, necessary and sufficient conditions are stated for the local equivalence of two expanded identified models M1 and M2 when fitting the more restricted model M0. Assuming several regularity conditions, the rank

  14. Effect of polyethelene oxide on the thermal degradation of cellulose biofilm – Low cost material for soft tissue repair in dentistry

    Science.gov (United States)

    Tyler, Rakim; Schiraldi, David; Roperto, Renato; Faddoul, Fady; Teich, Sorin

    2017-01-01

    Background Bio cellulose is a byproduct of sweet tea fermentation known as kombusha. During the biosynthesis by bacteria cellulose chains are polymerized by enzyme from activated glucose. The single chains are then extruded through the bacterial cell wall. Interestingly, a potential of the Kombucha’s byproduct bio cellulose (BC) as biomaterial had come into focus only in the past few decades. The unique physical and mechanical properties such as high purity, an ultrafine and highly crystalline network structure, a superior mechanical strength, flexibility, pronounced permeability to gases and liquids, and an excellent compatibility with living tissue that reinforced by biodegradability, biocompatibility, large swelling ratios. Material and Methods The bio-cellulose film specimens were provided by the R.P Dressel dental materials laboratory, Department of Comprehensive Care, School of Dental Medicine, Case Western Reserve University, Cleveland, US. The films were harvested, washed with water and dried at room temperature overnight. 1wt% of PEG-2000 and 10wt% of NaOH were added into ultrapure water to prepare PEG/NaOH solution. Then bio-cellulose film was added to the mixture and swell for 3 h at room temperature. All bio-cellulose film specimens were all used in the TA Instruments Q500 Thermogravmetric Analyzer to investigate weight percent lost and degradation. The TGA was under ambient air conditions at a heating rate of 10ºC/min. Results and Conclusions PEG control exhibited one transition with the peak at 380ºC. Cellulose and cellulose/ PEG films showed 3 major transitions. Interestingly, the cellulose/PEG film showed slightly elevated temperatures when compared to the corresponding transitions for cellulose control. The thermal gravimetric analysis (TGA) degradation curves were analyzed. Cellulose control film exhibited two zero order transitions, that indicate the independence of the rate of degradation from the amount on the initial substance. The

  15. Equivalence in Ventilation and Indoor Air Quality

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, Max; Walker, Iain; Logue, Jennifer

    2011-08-01

    We ventilate buildings to provide acceptable indoor air quality (IAQ). Ventilation standards (such as American Society of Heating, Refrigerating, and Air-Conditioning Enginners [ASHRAE] Standard 62) specify minimum ventilation rates without taking into account the impact of those rates on IAQ. Innovative ventilation management is often a desirable element of reducing energy consumption or improving IAQ or comfort. Variable ventilation is one innovative strategy. To use variable ventilatio