Sample records for sustained mechanical loading

  1. Computational modeling of the mechanical modulation of the growth plate by sustained loading

    Directory of Open Access Journals (Sweden)

    Narváez-Tovar Carlos A


    Full Text Available Abstract This paper presents a computational model that describes the growth of the bone as a function of the proliferation and hypertrophy of chondrocytes in the growth plate. We have included the effects of the mechanical loads on the sizes of the proliferative and hypertrophic areas, the number of proliferative chondrocytes and the final size of the hypertrophic chondrocytes. The validation of the model was performed with experimental data published on other investigations about proximal tibia of rats, subjected to sustained axial stresses of 0.1 MPa, 0.0 MPa, -0.1 MPa and −0.2 MPa. Growth was simulated during 23 days, obtaining numerical errors between 2.77% and 3.73% with respect to experimental growth rates. The results obtained show that the model adequately simulates the behavior of the growth plate and the effect of mechanical loads over its cellular activity.

  2. Mechanism isolates load weighing cell during lifting of load (United States)

    Haigler, J. S.


    Load weighing cell used in conjuction with a hoist is isolated during lifting and manipulation of the load. A simple mechanism, attached to a crane hook, provides a screw adjustment for engaging the load cell during weighing of the load and isolating it from lift forces during hoisting of the load.

  3. Shear Capacity of Concrete Beams under Sustained Loading

    NARCIS (Netherlands)

    Sarkhosh, R.; Walraven, J.C.; Den Uijl, J.A.; Braam, C.R.


    Long-term tests on large-scale concrete beams without shear reinforcement, which are tested for more than two years under sustained loading close to the ultimate shear capacity (load ratio ranging from 87% to 95%) under climate controlled condition, show that sustained loading has no significant

  4. The chemistry induced by mechanical load

    CERN Document Server

    Frank, Irmgard


    Results in the field of mechanochemistry are summarized. For example under mechanical load often a solvolysis is observed instead of a simple homolytic bond rupture. Also a mechanically induced redox reaction was reported experimentally and could be modelled theoretically. With CPMD simulations it is possible to understand multi-step mechanisms in full detail.

  5. Mechanical behavior of cyclically loaded PZT

    Energy Technology Data Exchange (ETDEWEB)

    White, G.S.; Hill, M.D.; Freiman, S.W. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Hwang, C.S. [Seoul National Univ. (Korea, Republic of)


    Uses of intelligent materials which involve the application of force or the generation of displacements will require the incorporation of some form of actuator material into the overall structure. Typically, these types of applications will result in the generation of cyclic loads on the actuator; depending upon the specific application, the frequency of the loading could be low, e.g., for positioning components, or relatively high, e.g., for damping out vibrations in machining tools. Nevertheless, the cyclic nature of the loading raises the specter of damage and, ultimately, failure arising from cyclic loading processes which would not be predicted by traditional mechanical properties test methods. It has been found that PZT loaded cyclically sometimes fails at loads below its nominal strength, as measured by traditional, monotonically increasing load tests. Damage mechanisms which come into play as a result of the cyclic loading conditions have been postulated as the reasons for this behavior. Recent work investigating the cyclic loading of a PZT-8 material at resonance frequency determined that microcracks were generated in the high stress region of the material. Recent results demonstrate that macrocrack extension appears to be accompanied by domain reorientation whereas microcracks can propagate around PZT grains without affecting the domains, (2) morphology and distribution of microcracks generated under different loading conditions can change dramatically that the qualitative mechanical response of PZT-8 to cyclic loading appears to be insensitive to grain morphology. The results presented imply that stresses generated at the tips of macrocracks are much larger than those at microcracks, that temperature strongly affects the rate of microcrack generation, and that wide distributions in grain size and the presence of large voids do not necessarily result in increased microcrack generation over that seen in 2 {micro}m grain size, small pore material.

  6. Sustainable Stream Waste Load Allocation with Considering Equity (United States)

    Liao, W.; Tung, C.


    The stream assimilative capacity is the carrying capacity of a river for the maximum waste load without exceeding the water quality standard. However, only optimizing maximal waste loads may lead to inequity. Equity is an important issue in waste load allocation problems. This research formulates a multi-objective model that considers minimizing inequity and maximizing total waste loads by using water quality models, as well as combining Gini coefficient and Data Envelopment Analysis (DEA) to assess the relationship between the equity levels and the maximum waste load. It is also discussed that the impacts of changes in the land use among up- stream and down-stream on assimilative capacity and equity, which can provide useful information for the policy making of sustainable watershed management.

  7. Mechanical Predictors of Discomfort during Load Carriage.

    Directory of Open Access Journals (Sweden)

    Patrick D Wettenschwiler

    Full Text Available Discomfort during load carriage is a major issue for activities using backpacks (e.g. infantry maneuvers, children carrying school supplies, or outdoor sports. It is currently unclear which mechanical parameters are responsible for subjectively perceived discomfort. The aim of this study was to identify objectively measured mechanical predictors of discomfort during load carriage. We compared twelve different configurations of a typical load carriage system, a commercially available backpack with a hip belt. The pressure distribution under the hip belt and the shoulder strap, as well as the tensile force in the strap and the relative motion of the backpack were measured. Multiple linear regression analyses were conducted to investigate possible predictors of discomfort. The results demonstrate that static peak pressure, or alternatively, static strap force is a significant (p<0.001 predictor of discomfort during load carriage in the shoulder and hip region, accounting for 85% or more of the variation in discomfort. As an additional finding, we discovered that the regression coefficients of these predictors are significantly smaller for the hip than for the shoulder region. As static peak pressure is measured directly on the body, it is less dependent on the type of load carriage system than static strap force. Therefore, static peak pressure is well suited as a generally applicable, objective mechanical parameter for the optimization of load carriage system design. Alternatively, when limited to load carriage systems of the type backpack with hip belt, static strap force is the most valuable predictor of discomfort. The regionally differing regression coefficients of both predictors imply that the hip region is significantly more tolerant than the shoulder region. In order to minimize discomfort, users should be encouraged to shift load from the shoulders to the hip region wherever possible, at the same time likely decreasing the risk of low

  8. Fibrin Networks Support Recurring Mechanical Loads by Adapting their Structure across Multiple Scales

    NARCIS (Netherlands)

    Kurniawan, N.A.; Vos, B.E.; Biebricher, A.S.; Wuite, G.J.L.; Peterman, E.J.G.; Koenderink, G.H.


    Tissues and cells sustain recurring mechanical loads that span a wide range of loading amplitudes and timescales as a consequence of exposure to blood flow, muscle activity, and external impact. Both tissues and cells derive their mechanical strength from fibrous protein scaffolds, which typically

  9. Urban Runoff and Nutrients Loading Control from Sustainable BMPs (Invited) (United States)

    Xiao, Q.


    construction of runoff retention basins and treatment facilities to meet TMDL (Total Maximum Daily Load) regulations are not cost-effective or practical. An alternative approach is to control runoff and nutrients on-site through installation of decentralized BMPs that detain and infiltrate runoff before it reaches storm drains. Recent developed green-infrastructure which integrating engineered soil and trees to reduce runoff and nutrients loading is a self-sustained best management practice (BMP). This BMP has been testing and used in urban runoff control. In Davis, CA this type of BMPs were installed in a parking lot and a residential property to evaluate the system’s effectiveness on reducing storm runoff and pollutant loading from the parking lot and irrigated landscape. Storm runoff and pollutant loading were measured and monitored during February 2007 thru May 2009 from the parking lot. The BMP reduced surface runoff and nutrients by 88.8% and 95.3%, respectively. In the residential irrigated landscape, the dry-weather runoff was monitored during 2007 irrigation season, the BMP captured almost all dry weather runoff. The performance of these BMPs demonstrated their potential use for reducing runoff and nutrients loading. Control urban runoff from these 23% landscape (i.e., parking lot and irrigated turf grass) could largely alter the runoff and nutrients transport and their dynamic in our water system.

  10. Mechanisms to absorb load in amputee running. (United States)

    Strike, Siobhan C; Wickett, Oliver; Schoeman, Marlene; Diss, Ceri E


    We aimed to determine if a shock absorbing pylon (SAP) influenced the ground reaction force characteristics and the shock absorbing mechanisms compared to a rigid pylon (Rigid) during the loading phase in running. To determine if the SAP influences the mechanisms of loading compared to the Rigid condition. A convenience sample of transtibial amputees participated in a laboratory-based study. The prosthetic set-up was randomly altered fd\\sdsd. Five recreationally active male transtibial amputees age: 18-50 years; mean mass: 86.7 ± 17.5 kg; height: 1.77 ± 0.07 m) volunteered from a population-based sample. They completed a within-participant-designed study assessing a SAP and a Rigid condition during running. Kinematic and kinetic data were collected during two sessions following a one-week customization period. Loading rate, peak vertical and horizontal ground reaction forces and the time to each measure along with knee and hip angular displacement, absorbing powers and work done between the SAP and Rigid conditions were not systematically affected by the prosthetic condition. The effect of the SAP was minimal and inconsistent in the loading phase, with only some amputees presenting higher and others with lower values for the tested variables.

  11. Study on Clean Development Mechanism, Quantitative and Sustainable Mechanism

    Directory of Open Access Journals (Sweden)

    Donghai Yuan


    Full Text Available Aiming at the system and market problem of clean development mechanism (CDM, this study is carried out to establish the feasibility of certified emission reduction (CER quantitative evaluation method and reserve mechanism in host country at the United Nations Framework Convention on Climate Change (UNFCCC level. After the introduction of CER quantitative and sustainable mechanism, the amount of CER that can enter the market was cut to a quarter, which reduces about 75% of the expected CER supply. Market CER from the technology types of higher CER market share and lower support for sustainable development appears to have different degrees of reduction. As for the technology types of lower CER market share and higher support for sustainable development, the amount of market CER is maintained in line with prevailing scenario, and market CER supply becomes more balanced.

  12. Sustained load performance of adhesive anchor systems in concrete (United States)

    Davis, Todd Marshall

    Stemming from a tragic failure of an adhesive anchor system, this research project investigated the sustained load performance of adhesive anchors in concrete under different installation and in-service conditions. The literature review investigated the current state of art of adhesive anchors. Extensive discussion was devoted to the behavior of adhesive anchors in concrete as well as the many factors that can affect their short-term and sustained load strength. Existing standards and specifications for the testing, design, construction, and inspection of adhesive anchors were covered. Based on the results of the literature review and the experience of the research group, a triage was conducted on many parameters identified as possibly affecting the sustained load performance of adhesive anchors and the highest priority parameters were investigated in this project. A stress versus time-to-failure approach was used to evaluate sensitivity of three ICC-ES AC 308 approved adhesive anchor systems. Of the various parameters investigated, only elevated in-service temperature and manufacturer's cure time was shown to exhibit adverse effects on sustained loads more than that predicted by short-term tests of fully cured adhesive over a reasonable structure lifetime of 75 years. In a related study, various tests were conducted on the adhesive alone (time-temperature superposition, time-stress superposition, and dogbone tensile tests). The results of that study were used to investigate the existence of a correlation with long-term anchor pullout testing in concrete. No consistent correlations were detected for the adhesives in the study. Tests were also conducted on the effect of early-age concrete on adhesive anchor bond strength. On the basis of confined test bond-strength alone, adhesive A (vinyl ester) did not show any significant increase after 14 days (102% of 28 day strength at 14 days), and adhesive B and C (epoxies) did not show any significant increase after 7 days

  13. Dairy cattle sustainability using the emergy methodology: Environmental loading ratio

    Directory of Open Access Journals (Sweden)

    Edmar Eduardo Bassan Mendes


    Full Text Available The dairy cattle activity in São Paulo State has been depressed in recent years, evidenced by the reduction of 35.47% of dairy herd between 1996 and 2008 (LUPA and 29.73% in milk production between the census of the IBGE (1995 and 2006. Activity remains in the Agricultural Production Units (UPA that have adopted more intensive systems of milk production, using animals of high genetic potential, management-intensive rotational grazing or agricultural inputs, and with the objective of profit maximization. In face of environmental pressures, the problem is to know the degree of sustainability of milk production. The objective in this work was to analyze the production of milk from a farm in the municipality of Guzolândia, São Paulo State, during the period 2005/2011, using the emergy methodology to assess the sustainability of system, calculated by Environmental Loading Ratio (ELR. The UPA Alto da Araúna is dedicated to dairy cattle adopting the system of milk production semi-intensive type B; it produces on average 650 liters of milk per day with 45 lactating cows, using 30 ha of pasture with supplemental feed and silage. It has sandy soil, classified as latossol red, yellow, ortho phase, with gently rolling slopes. The UPA is administered with business structure, aiming to profit maximization and minimization of environmental impacts, seeking to maintain economically viable activity and preserving the environment. Currently, administrative decisions have the support of operational control that collects and records information necessary to generate animal and agricultural indexes that evaluate the performance of the UPA, in addition to managerial accounting records that generate cash flow information used to evaluate the economic efficiency of the UPA. The Environmental Loading Ratio (ELR=N+F/R is obtained by the ratio of natural non-renewable resources (N plus economic resources (F by total renewable emergy (R. It is an indicator of the

  14. Effect of Loads and Other Key Factors on Oil-Transformer Ageing: Sustainability Benefits and Challenges

    Directory of Open Access Journals (Sweden)

    Radu Godina


    Full Text Available Transformers are one of the more expensive pieces of equipment found in a distribution network. The transformer’s role has not changed over the last decades. With simple construction and at the same time mechanically robust, they offer long term service that on average can reach half a century. Today, with the ongoing trend to supply a growing number of non-linear loads along with the notion of distributed generation (DG, a new challenge has arisen in terms of transformer sustainability, with one of the possible consequences being accelerated ageing. In this paper we carefully review the existing studies in the literature of the effect of loads and other key factors on oil-transformer ageing. The state-of-the-art is reviewed, each factor is analysed in detail, and in the end a smart transformer protection method is sought in order to monitor and protect it from upcoming challenges.

  15. Fluoride inhibits the response of bone cells to mechanical loading

    NARCIS (Netherlands)

    Willems, H.M.E.; van den Heuvel, E.G.H.M.; Castelein, S.; Buisman, J.K.; Bronckers, A.L.J.J.; Bakker, A.D.; Klein-Nulend, J.


    The response of bone cells to mechanical loading is mediated by the cytoskeleton. Since the bone anabolic agent fluoride disrupts the cytoskeleton, we investigated whether fluoride affects the response of bone cells to mechanical loading, and whether this is cytoskeleton mediated. The

  16. Improving sustained drug delivery from ophthalmic lens materials through the control of temperature and time of loading. (United States)

    Topete, Ana; Oliveira, Andreia S; Fernandes, A; Nunes, T G; Serro, A P; Saramago, B


    Although the possibility of using drug-loaded ophthalmic lens to promote sustained drug release has been thoroughly pursued, there are still problems to be solved associated to the different alternatives. In this work, we went back to the traditional method of drug loading by soaking in the drug solution and tried to optimize the release profiles by changing the temperature and the time of loading. Two materials commercially available under the names of CI26Y and Definitive 50 were chosen. CI26Y is used for intraocular lenses (IOLs) and Definitive 50 for soft contact lenses (SCLs). Three drugs were tested: an antibiotic, moxifloxacin, and two anti-inflammatories, diclofenac and ketorolac. Sustained drug release from CI26Y disks for, at least 15 days, was obtained for moxifloxacin and diclofenac increasing the loading temperature up to 60 °C or extending the loading time till two months. The sustained release of ketorolac was limited to about 8 days. In contrast, drug release from Definitive 50 disks could not be improved by changing the loading conditions. An attempt to interpret the impact of the loading conditions on the drug release behavior was done using solid-state NMR and differential scanning calorimetry. These studies suggested the establishment of reversible, endothermic interactions between CI26Y and the drugs, moxifloxacin and diclofenac. The loading temperature had a slight effect on the mechanical and optical properties of drug loaded CI26Y samples, which still kept adequate properties to be used as IOL materials. The in vivo efficacy of CI26Y samples, drug loaded at 60 °C for two weeks, was predicted using a simplified mathematical model to estimate the drug concentration in the aqueous humor. The estimated concentrations were found to comply with the therapeutic needs, at least, for moxifloxacin and diclofenac. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. Design and development of sustained-release glyburide-loaded ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 2. Design and development of sustained-release ... Keywords. Silica nanoparticles; glyburide; sustained release; sol–gel method. ... Silica nanoparticles were synthesized by the sol–gel method using tetra-ethyl ortho-silane as a precursor. Glyburide was ...

  18. Pilot Study of a Plug Load Management System: Preparing for Sustainability Base (United States)

    National Aeronautics and Space Administration — NASA Ames Research Center’s Sustainability Base is a new 50,000 sq. ft. high-performance office building targeting a LEED Platinum rating. Plug loads are expected to...

  19. Failure mechanisms of load-sharing complex systems (United States)

    Siddique, Shahnewaz; Volovoi, Vitali


    We investigate the failure mechanisms of load-sharing complex systems. The system is composed of multiple nodes or components whose failures are determined based on the interaction of their respective strengths and loads (or capacity and demand, respectively) as well as the ability of a component to share its load with its neighbors when needed. We focus on two distinct mechanisms to model the interaction between components' strengths and loads. The failure mechanisms of these two models demonstrate temporal scaling phenomena, phase transitions, and multiple distinct failure modes excited by extremal dynamics. For critical ranges of parameters the models demonstrate power-law and exponential failure patterns. We identify the similarities and differences between the two mechanisms and the implications of our results for the failure mechanisms of complex systems in the real world.

  20. Design of a biaxial mechanical loading bioreactor for tissue engineering. (United States)

    Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K


    We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0


    Directory of Open Access Journals (Sweden)

    A. I. Safonov


    Full Text Available The paper analyzes factors that determine dynamic loads of mechanical transmission of trolleybus traction driving gear. The paper proposes a methodology for determination of calculative moments of loading transmission elements. Results of the research are analyzed and recommendations on  dynamic reduction of trolleybus transmission are given in the paper. 

  2. Features wear nodes mechanization wing aircraft operating under dynamic loads

    Directory of Open Access Journals (Sweden)

    А.М. Хімко


    Full Text Available  The conducted researches of titanic alloy ВТ-22 at dynamic loading with cycled sliding and dynamic loading in conditions of rolling with slipping. It is established that roller jamming in the carriage increases wear of rod of mechanization of a wing to twenty times. The optimum covering for strengthening wearied sites and restoration of working surfaces of wing’s mechanization rod is defined.

  3. Design and development of sustained-release glyburide-loaded ...

    Indian Academy of Sciences (India)

    methoxysilane (APTMS) was added and the whole mixture was stirred further for 8 h. Then the mix- ture was centrifuged at 10,000 rpm for 20 min and air dried. The final dried formulation was used for further analysis such as drug loading and DR. 3.

  4. Design and analysis of a novel mechanical loading machine for dynamic in vivo axial loading. (United States)

    Macione, James; Nesbitt, Sterling; Pandit, Vaibhav; Kotha, Shiva


    This paper describes the construction of a loading machine for performing in vivo, dynamic mechanical loading of the rodent forearm. The loading machine utilizes a unique type of electromagnetic actuator with no mechanically resistive components (servotube), allowing highly accurate loads to be created. A regression analysis of the force created by the actuator with respect to the input voltage demonstrates high linear correlation (R(2) = 1). When the linear correlation is used to create dynamic loading waveforms in the frequency (0.5-10 Hz) and load (1-50 N) range used for in vivo loading, less than 1% normalized root mean square error (NRMSE) is computed. Larger NRMSE is found at increased frequencies, with 5%-8% occurring at 40 Hz, and reasons are discussed. Amplifiers (strain gauge, linear voltage displacement transducer (LVDT), and load cell) are constructed, calibrated, and integrated, to allow well-resolved dynamic measurements to be recorded at each program cycle. Each of the amplifiers uses an active filter with cutoff frequency at the maximum in vivo loading frequencies (50 Hz) so that electronic noise generated by the servo drive and actuator are reduced. The LVDT and load cell amplifiers allow evaluation of stress-strain relationships to determine if in vivo bone damage is occurring. The strain gauge amplifier allows dynamic force to strain calibrations to occur for animals of different sex, age, and strain. Unique features are integrated into the loading system, including a weightless mode, which allows the limbs of anesthetized animals to be quickly positioned and removed. Although the device is constructed for in vivo axial bone loading, it can be used within constraints, as a general measurement instrument in a laboratory setting.

  5. Reduced phrenic motoneuron recruitment during sustained inspiratory threshold loading compared to single-breath loading: a twitch interpolation study

    Directory of Open Access Journals (Sweden)

    Mathieu Raux


    Full Text Available In humans, inspiratory constraints engage cortical networks involving the supplementary motor area. Functional magnetic resonance imaging (fMRI shows that the spread and intensity of the corresponding respiratory-related cortical activation dramatically decrease when a discrete load becomes sustained. This has been interpreted as reflecting motor cortical reorganisation and automatisation, but could proceed from sensory and/or affective habituation. To corroborate the existence of motor reorganisation between single-breath and sustained inspiratory loading (namely changes in motor neurones recruitment, we conducted a diaphragm twitch interpolation study based on the hypothesis that motor reorganisation should result in changes in the twitch interpolation slope. Fourteen healthy subjects (age: 21 – 40 years were studied. Bilateral phrenic stimulation was delivered at rest, upon prepared and targeted voluntary inspiratory efforts (vol, upon unprepared inspiratory efforts against a single-breath inspiratory threshold load (single-breath, and upon sustained inspiratory efforts against the same type of load (continuous. The slope of the relationship between diaphragm twitch transdiaphragmatic pressure and the underlying transdiaphragmatic pressure was –1.1 ± 0.2 during vol, –1.5 ± 0.7 during single-breath, and -0.6 ± 0.4 during continuous (all slopes expressed in percent of baseline.percent of baseline-1 all comparisons significant at the 5% level. The contribution of the diaphragm to inspiration, as assessed by the gastric pressure to transdiaphragmatic pressure ratio, was 31 ± 17 % during vol, 22 ± 16 % during single-breath (p=0.13, and 19 ± 9 % during continuous (p = 0.0015 vs. vol. This study shows that the relationship between the amplitude of the transdiaphragmatic pressure produced by a diaphragm twitch and its counterpart produced by the underlying diaphragm contraction is not unequivocal. If twitch interpolation is interpreted as

  6. Evaluation of Muscle Mechanical Capacities through the Two-load Method: Optimization of the Load Selection. (United States)

    Pérez-Castilla, Alejandro; Jaric, Slobodan; Feriche, Belén; Padial, Paulino; García-Ramos, Amador


    Recent research has revealed that the force-velocity relationship obtained from the 'two-load method' (i.e., functional movements tested against just 2 external loads) could be a feasible method for the selective assessment of muscle force, velocity, and power-producing capacities. The study investigated the reliability and concurrent validity of the outcomes of the two-load method observed from (1) farther vs. closer data points (20-70%1RM, 30-60%1RM, and 40-50%1RM), and (2) force-biased (50-70%1RM) vs. velocity-biased (20-40%1RM) data points. Twenty-two men were tested on a ballistic bench press throw performed against 6 incremental loads ranging from 20% to 70% of the bench press one-repetition maximum (1RM). The two-load methods were constructed based on pairs of individually selected external loads and compared with the outcome of the force-velocity regression method applied to all 6 loads. The reliability and validity of the force-velocity relationship parameters decreased with the proximity of the data points (40-50%1RM loads (i.e., lighter and heavier loads, respectively) revealed a similar, but relatively moderate reliability and validity. Overall, the farthest pair of loads (i.e., 20%1RM and 70%1RM) revealed the highest reliability (CV = 5.5%, ICC = 0.89) and validity (r = 0.98) among all the two-load methods evaluated. These results demonstrate that the 20-70%1RM two-load method could be a feasible approach for testing individual muscle mechanical capacities, while the observed outcomes could be the most reliable and valid when obtained from the farthest pairs of applied loads.

  7. Stress analysis in a functionally graded disc under mechanical loads ...

    Indian Academy of Sciences (India)

    Stress analysis in a functionally graded disc under mechanical loads and a steady state temperature distribution. HASAN ÇALLIO ˘GLU. Department of Mechanical Engineering, Pamukkale University, 20070,. Denizli, Turkey e-mail: MS received 25 November 2009; revised 12 August 2010; accepted.

  8. Mechanical properties of concrete to cyclic uniaxial tensile loading ...

    Indian Academy of Sciences (India)

    The mechanical properties of concrete under cyclic tensile loading using square waveform, sine waveform and ramp waveform are studied. ... College of Civil and Transportation Engineering, Hobai University, Nanjing 210098, China; College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing ...

  9. Monitoring steel corrosion in reinforced concrete beams with variable crack widths under sustained load

    NARCIS (Netherlands)

    Blagojevic, A.; Koleva, D.A.; Walraven, J.C.


    This work reports on the investigation of steel corrosion behavior in 1000 mm in length reinforced concrete beams under sustained load, aiming to define a feasible experimental protocol for corrosion monitoring. The beams were subjected to wetting (5% NaCl for corroding cases and tap water for

  10. Key Sustainable Tourism Mechanisms for Poverty Reduction and ...

    African Journals Online (AJOL)

    Increasing populations, together with the impact of climate change, are resulting in greater competition for land and a necessity for sustainable land use. Tourism can provide a flow of benefits from conservation to rural communities to reduce poverty and promote biodiversity conservation. Three key mechanisms of ...

  11. WP/072 Is the Clean Development Mechanism Promoting Sustainable Development?

    DEFF Research Database (Denmark)

    Huang, Yongfu; He, Jingjing; Tarp, Finn

    One of the dual objectives of the Clean Development Mechanism (CDM) of the Kyoto Protocol is to promote sustainable development in the host countries. With different CDM indicators for 58 CDM host countries over 2005-10, this paper empirically assesses whether CDM project development fulfils...

  12. Devolution: A mechanism for scaling adoption of sustainable land ...

    African Journals Online (AJOL)

    Sustainable Land Management (SLM) technologies are known to improve food production and productivity in areas prone to high soil degradation, arising from water and soil nutrient losses. In eastern Africa, mechanisms for mitigation of this land degradation have been developed, but their uptake has been minimal.

  13. Sustained release donepezil loaded PLGA microspheres for injection: Preparation, in vitro and in vivo study

    Directory of Open Access Journals (Sweden)

    Wenjia Guo


    Full Text Available The purpose of this study was to develop a PLGA microspheres-based donepezil (DP formulation which was expected to sustain release of DP for one week with high encapsulation efficiency (EE. DP derived from donepezil hydrochloride was encapsulated in PLGA microspheres by the O/W emulsion-solvent evaporation method. The optimized formulation which avoided the crushing of microspheres during the preparation process was characterized in terms of particle size, morphology, drug loading and EE, physical state of DP in the matrix and in vitro and in vivo release behavior. DP microspheres were prepared successfully with average diameter of 30 µm, drug loading of 15.92 ± 0.31% and EE up to 78.79 ± 2.56%. Scanning electron microscope image showed it has integrated spherical shape with no drug crystal and porous on its surface. Differential scanning calorimetry and X-ray diffraction results suggested DP was in amorphous state or molecularly dispersed in microspheres. The Tg of PLGA was increased with the addition of DP. The release profile in vitro was characterized with slow but continuous release that lasted for about one week and fitted well with first-order model, which suggested the diffusion governing release mechanism. After single-dose administration of DP microspheres via subcutaneous injection in rats, the plasma concentration of DP reached peak concentration at 0.50 d, and then declined gradually, but was still detectable at 15 d. A good correlation between in vitro and in vivo data was obtained. The results suggest the potential use of DP microspheres for treatment of Alzheimer's disease over long periods.

  14. Microcracking in composite laminates under thermal and mechanical loading. Thesis (United States)

    Maddocks, Jason R.


    Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a

  15. Sustainable HIV treatment in Africa through viral-load-informed differentiated care

    DEFF Research Database (Denmark)

    Phillips, Andrew; Shroufi, Amir; Vojnov, Lara


    every 6 months, but patients are rarely switched to second-line therapies. To ensure sustainability of treatment programmes, a transition to more cost-effective delivery of antiretroviral therapy is needed. In contrast to the CD4 count, measurement of the level of HIV RNA in plasma (the viral load...... to a second-line regimen. The most feasible approach to measuring viral load in many countries is to collect dried blood spot samples for testing in regional laboratories; however, there have been concerns over the sensitivity and specificity of this approach to define treatment failure and the delay...... in returning results to the clinic. We use modelling to synthesize evidence and evaluate the cost-effectiveness of viral-load-informed differentiated care, accounting for limitations of dried blood sample testing. We find that viral-load-informed differentiated care using dried blood sample testing is cost...

  16. Loading rate effect on mechanical properties of cervical spine ligaments. (United States)

    Trajkovski, Ana; Omerovic, Senad; Krasna, Simon; Prebil, Ivan


    Mechanical properties of cervical spine ligaments are of great importance for an accurate finite element model when analyzing the injury mechanism. However, there is still little experimental data in literature regarding fresh human cervical spine ligaments under physiological conditions. The focus of the present study is placed on three cervical spine ligaments that stabilize the spine and protect the spinal cord: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. The ligaments were tested within 24-48 hours after death, under two different loading rates. An increase trend in failure load, failure stress, stiffness and modulus was observed, but proved not to be significant for all ligament types. The loading rate had the highest impact on failure forces for all three ligaments (a 39.1% average increase was found). The observed increase trend, compared to the existing increase trends reported in literature, indicates the importance of carefully applying the existing experimental data, especially when creating scaling factors. A better understanding of the loading rate effect on ligaments properties would enable better case-specific human modelling.

  17. Node reserve mechanism (over dynamic load-balancing)

    Energy Technology Data Exchange (ETDEWEB)

    Muniz, Francisco Junqueira; Azevedo, Carlos Vicente Goulart de; Dalle, Hugo Moura, E-mail:, E-mail:, E-mail: [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)


    Multiple-Instruction Multi-Data (MIMD) distributed-memory processing systems (such as an IBM like set of PCs, connected by a communication device) are since long time commercially available and in use. But many Research Institutions still use them as a mono-user facility: they are much more cost effective if used as a (multi-user) shared resource. However, the use of MIMD machines as a shared resource is often limited due to lack of an efficient, easy-to-use and on hand dynamic load-balancing technique. This work describes the arrangements that were made to establish the interface between a mechanism of processing power availability (resource determined from a shared computer facility) and simultaneous users, demand for resources. The key point is to allow the application designer to ask for (at once) as many nodes as he needs (a multi-reserve mechanism). The system runs over Linux/X86 computing nodes (a cluster). In order to show the interface functionality, the startup module of a MCNP package was modified in such a way that the multi-reserve node mechanism together with a multi-user dynamic load-balancing approach could be used. Nodes set demand is an intrinsic feature of MCNP package. Such modified MCNP package was successfully run over a dynamic load-balancing system. (author)

  18. Impact of mechanical ventilation and fluid load on pulmonary glycosaminoglycans. (United States)

    Moriondo, Andrea; Marcozzi, Cristiana; Bianchin, Francesca; Reguzzoni, Marcella; Severgnini, Paolo; Protasoni, Marina; Raspanti, Mario; Passi, Alberto; Pelosi, Paolo; Negrini, Daniela


    The combined effect of mechanical ventilation and fluid load on pulmonary glycasaminoglycans (GAGs) was studied in anaesthetized rats ((BW 290±21.8 (SE)g) mechanically ventilated for 4h: (a) at low (∼7.5mlkg(-1)) or high (∼23mlkg(-1)) tidal volume (V(T)) and zero alveolar pressure; (b) at low or high V(T) at 5cmH(2)O positive end-expiratory pressure (PEEP); (c) with or without 7mlkg(-1)h(-1) intravenous infusion of Phosphate Buffer Solution (PBS). Compared to spontaneous breathing, GAGs extractability decreased by 52.1±1.5% and 42.2±7.3% in not-infused lungs mechanically ventilated at low V(T) or at high V(T) and PEEP, respectively. In contrast, in infused lungs, GAGs extractability increased by 56.1±4.0% in spontaneous ventilation and PEEP and up to 81.1% in all mechanically ventilated lungs, except at low V(T) without PEEP. In the absence of an inflammatory process, these results suggest that PEEP was protective at low but not at high V(T) when alveolar structures experience exceedingly high stresses. When combined to mechanical ventilation, fluid load might exacerbate edema development and lung injury. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Regional lung tissue changes with mechanical ventilation and fluid load. (United States)

    Marcozzi, Cristiana; Moriondo, Andrea; Solari, Eleonora; Reguzzoni, Marcella; Severgnini, Paolo; Protasoni, Marina; Passi, Alberto; Pelosi, Paolo; Negrini, Daniela


    To investigate the regional gravity-dependent impact of mechanical ventilation and fluid overload on lung extracellular matrix (ECM) in healthy lungs. The glycosaminoglycans (GAGs) composition of the ventral and dorsal lung parenchyma was determined in anesthetized supine healthy rats mechanically ventilated for 4 hours in air: (a) at low (∼7.5 mL/kg) or high (∼ 23 mL /kg) tidal volume (V(T)) and 0 cmH2O positive end-expiratory pressure (PEEP); (b) at low or high V(T) at 5 cmH2O PEEP and (c) with or without 7 mL /(kg·h) intravenous saline infusion. Mechanical ventilation degraded lung ECM, with alveolar septa thinning and structural GAGs disorganization. Low V(T) ventilation was associated with significant tissue structure changes in both ventral and dorsal lung regions, while high VT mainly affected the dependent ones. PEEP decreased ECM injury mainly in the ventral lung regions, although it did not prevent matrix fragmentation and washout at high V(T). Intravascular fluid load increased lung damage prevalently in the ventral lung regions. Mechanical ventilation and fluid load may cause additive injuries in healthy lungs, mainly in ventral regions.

  20. Tunable tunneling electroresistance in ferroelectric tunnel junctions by mechanical loads. (United States)

    Luo, Xin; Wang, Biao; Zheng, Yue


    Combining nonequilibrium Green function's approach with density functional theory, effects of the applied mechanical loads on polarization, electrostatic potential, and tunneling conductance of a ferroelectric tunneling junction (FTJ) have been investigated. Using the first principle calculations, we show that compressive strains can induce and enhance the polarization in ferroelectric tunnel barriers, and practically achieve ferroelectricity in two unit cell thickness under a -2.2% compressive strain. More importantly, mechanical strains can significantly change the effective electrostatic potential in FTJ and thus control its tunneling conductance, which is defined as giant piezoelectric resistance (GPR) effect. Our calculations indicate that GPR effect is particularly significant near the paraelectric/ferroelectric phase transition, and increases exponentially with the barrier thickness. Furthermore, it is also found that defects of oxygen vacancies and nitrogen doping have little impact on GPR ratio of strained FTJ. Because of its high-sensitivity to external mechanical loads, FTJ with GPR effect should be adequate for applications in agile mechanical sensors, transducers, and other multifunctional devices.

  1. Comparison of Buildings\\' Thermal Loads against Building Orientations for Sustainable Housing in Pakistan

    Directory of Open Access Journals (Sweden)

    Arif Khan


    Full Text Available As the sustainable settlements have been included as a vital end product of all planning exercises, the architectural layouts should be well integrated with the sun path charts and the orientations of windows. Appropriate orientations can offer thermally indoor conditions besides physical and psychological comfort in any settlement at lesser energy demand. This investigation uses a vast number of computer simulations to visualize and make better decisions about heating and cooling requirements of a building and facades as a function of window orientation in composite climatic condition of Lahore. This study in particular evaluates the solar load in residential buildings responsive to the objective of sustainable new housing leading to thoughtful integration of architecture. The orientation of the buildings could then be essentially integrated to the current architectural and urban design practices in order to optimize the relationship between the given site ant the orientations for sustainable developments.

  2. Cellular and molecular mechanisms for the bone response to mechanical loading (United States)

    Bloomfield, S. A.


    To define the cellular and molecular mechanisms for the osteogenic response of bone to increased loading, several key steps must be defined: sensing of the mechanical signal by cells in bone, transduction of the mechanical signal to a biochemical one, and transmission of that biochemical signal to effector cells. Osteocytes are likely to serve as sensors of loading, probably via interstitial fluid flow produced during loading. Evidence is presented for the role of integrins, the cell's actin cytoskeleton, G proteins, and various intracellular signaling pathways in transducing that mechanical signal to a biochemical one. Nitric oxide, prostaglandins, and insulin-like growth factors all play important roles in these pathways. There is growing evidence for modulation of these mechanotransduction steps by endocrine factors, particularly parathyroid hormone and estrogen. The efficiency of this process is also impaired in the aged animal, yet what remains undefined is at what step mechanotransduction is affected.

  3. Single-source mechanical loading system produces biaxial stresses in cylinders (United States)

    Flower, J. F.; Stafford, R. L.


    Single-source mechanical loading system proportions axial-to-hoop tension loads applied to cylindrical specimens. The system consists of hydraulic, pneumatic, and lever arrangements which produce biaxial loading ratios.

  4. Mechanical properties and failure mechanisms of graphene under a central load. (United States)

    Wang, Shuaiwei; Yang, Baocheng; Zhang, Shouren; Yuan, Jinyun; Si, Yubing; Chen, Houyang


    By employing molecular dynamics simulations, the evolution of deformation of a monolayer graphene sheet under a central transverse loading are investigated. Dependence of mechanical responses on the symmetry (shape) of the loading domain, on the size of the graphene sheet, and on temperature, is determined. It is found that the symmetry of the loading domain plays a central role in fracture strength and strain. By increasing the size of the graphene sheet or increasing temperature, the tensile strength and fracture strain decrease. The results have demonstrated that the breaking force and breaking displacement are sensitive to both temperature and the symmetry of the loading domain. In addition, we find that the intrinsic strength of graphene under a central load is much smaller than that of graphene under a uniaxial load. By examining the deformation processes, two failure mechanisms are identified namely, brittle bond breaking and plastic relaxation. In the second mechanism, the Stone-Wales transformation occurs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Proteoglycan expression is influenced by mechanical load in TMJ discs. (United States)

    Nakao, Y; Konno-Nagasaka, M; Toriya, N; Arakawa, T; Kashio, H; Takuma, T; Mizoguchi, I


    The expression and assembly of the extracellular matrix are profoundly associated with adaptive and pathological responses of the temporomandibular joint (TMJ). To better understand the adaptive responses of the TMJ disc to mechanical loading, we examined the expression of 2 modular proteoglycans and 10 small leucine-rich proteoglycans (SLRPs) at the mRNA and protein levels and determined the contents of proteoglycan-related glycosaminoglycans (GAGs) in rat TMJ discs in response to altered mechanical loading caused by an incisal bite plane. One hundred thirty 7-week-old male Wistar rats were assigned to control and bite plane groups. TMJ disc thickness and the intensity of toluidine blue staining of metachromasia increased in the posterior band after 2 weeks of wearing the bite plane. GAG content increased significantly in the bite plane group after 2 weeks. Quantitative real-time RT-PCR (reverse transcription polymerase chain reaction) analysis indicated that biglycan and chondroadherin mRNA levels increased after 2 weeks and that the level of decorin mRNA increased at 4 weeks. Versican mRNA levels increased after 3 weeks, particularly for the V0 and V1 versican isoforms, which carry more GAG attachment sites than do the V2 and V3 isoforms. Western analysis demonstrated a corresponding increase in the levels of versican, biglycan, and decorin core proteins at 4 weeks in the bite plane group. These results indicate that mechanical loading differentially influences proteoglycan mRNA expression and protein accumulation in the TMJ disc. The change in proteoglycan mRNA and protein levels may lead to the modulation of matrix-matrix and cell-matrix interactions and has important biological significance for adaptation to complicated biomechanical requirements and for tissue maintenance in the TMJ disc. © International & American Associations for Dental Research 2014.

  6. Modulation of mechanical and muscular load by footwear during catering. (United States)

    Kersting, U G; Janshen, L; Böhm, H; Morey-Klapsing, G M; Brüggemann, G-P


    The BGN (Berufsgenossenschaft Nahrungsmithl und Gaststätten) reports 70% of job induced days off work to be connected with traumas of the ankle joint or overloading of the leg, knee and lower back, with an increased incidence in service areas outdoors (R. Grieshaber, personal communication). Workspace environments usually contain narrow passages, slopes or stairs and sudden changes between different surfaces. The aim of this study was to investigate the biomechanical load on the lower extremity and the low back during catering service when wearing different types of footwear. Thus, the potential for altering mechanical stress experienced during catering by variations in footwear was explored. Sixteen experienced waiters followed a course typical for a combined indoor-outdoor service area. Three different types of footwear were investigated using pressure distribution measurements, rearfoot goniometry and electromyography. A discriminant analysis revealed that the factors subject, shoe and surface affect rear foot movement or pressure distribution in different ways. A MANOVA demonstrated significant differences in loading parameters between footwear types. In general, these differences increased in magnitude in critical situations, such as climbing stairs or crossing slippery surfaces. The results of this study demonstrate that manipulations to footwear offer a great potential for modulating loads experienced during catering. Based on the results, the effects of constructional features are discussed. The method proposed can be applied to evaluate shoe modifications under realistic workplace conditions.

  7. Mechanisms of load dependency of myocardial ischemia reperfusion injury (United States)

    Mozaffari, Mahmood S; Liu, Jun Yao; Abebe, Worku; Baban, Babak


    Coronary artery disease and associated ischemic heart disease are prevalent disorders worldwide. Further, systemic hypertension is common and markedly increases the risk for heart disease. A common denominator of systemic hypertension of various etiologies is increased myocardial load/mechanical stress. Thus, it is likely that high pressure/mechanical stress attenuates the contribution of cardioprotective but accentuates the contribution of cardiotoxic pathways thereby exacerbating the outcome of an ischemia reperfusion insult to the heart. Critical events which contribute to cardiomyocyte injury in the ischemic-reperfused heart include cellular calcium overload and generation of reactive oxygen/nitrogen species which, in turn, promote the opening of the mitochondrial permeability transition pore, an important event in cell death. Increasing evidence also indicates that the myocardium is capable of mounting a robust inflammatory response which contributes importantly to tissue injury. On the other hand, cardioprotective maneuvers of ischemic preconditioning and postconditioning have led to identification of complex web of signaling pathways (e.g., reperfusion injury salvage kinase) which ultimately converge on the mitochondria to exert cytoprotection. The present review is intended to briefly describe mechanisms of cardiac ischemia reperfusion injury followed by a discussion of our work focused on how pressure/mechanical stress modulates endogenous cardiotoxic and cardioprotective mechanisms to ultimately exacerbate ischemia reperfusion injury. PMID:24224132

  8. Quasi-nano wear mechanism under repeated impact contact loading

    Institute of Scientific and Technical Information of China (English)


    A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact loading.Its characteristic is that the wear rate of QNWM is only 1/10-1/3 that of delamination mechanism at the same energy density.The diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-120 nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

  9. Coaxial Electrospray of Ranibizumab-Loaded Microparticles for Sustained Release of Anti-VEGF Therapies.

    Directory of Open Access Journals (Sweden)

    Leilei Zhang

    Full Text Available Age-related macular degeneration (AMD is the leading cause of vision loss and blindness in people over age 65 in industrialized nations. Intravitreous injection of anti-VEGF (vascular endothelial growth factor therapies, such as ranibizumab (trade name: Lucentis, provides an effective treatment option for neovascular AMD. We have developed an improved coaxial electrospray (CES process to encapsulate ranibizumab in poly(lactic-co-glycolic acid (PLGA microparticles (MPs for intravitreous injection and sustained drug release. This microencapsulation process is advantageous for maintaining the stability of the coaxial cone-jet configurations and producing drug-loaded MPs with as high as 70% encapsulation rate and minimal loss of bioactivitiy. The utility of this emerging process in intravitreous drug delivery has been demonstrated in both benchtop and in vivo experiments. The benchtop test simulates ocular drug release using PLGA MPs encapsulating a model drug. The in vivo experiment evaluates the inflammation and retinal cell death after intravitreal injection of the MPs in a chick model. The experimental results show that the drug-load MPs are able to facilitate sustained drug release for longer than one month. No significant long term microglia reaction or cell death is observed after intravitreal injection of 200 μg MPs. The present study demonstrates the technical feasibility of using the improved CES process to encapsulate water-soluble drugs at a high concentration for sustained release of anti-VEGF therapy.

  10. Sustainable HIV Treatment in Africa through Viral Load-Informed Differentiated Care (United States)

    Phillips, Andrew; Shroufi, Amir; Vojnov, Lara; Cohn, Jennifer; Roberts, Teri; Ellman, Tom; Bonner, Kimberly; Rousseau, Christine; Garnett, Geoff; Cambiano, Valentina; Nakagawa, Fumiyo; Ford, Deborah; Bansi-Matharu, Loveleen; Miners, Alec; Lundgren, Jens; Eaton, Jeff; Parkes-Ratanshi, Rosalind; Katz, Zachary; Maman, David; Ford, Nathan; Vitoria, Marco; Doherty, Meg; Dowdy, David; Nichols, Brooke; Murtagh, Maurine; Wareham, Meghan; Palamountain, Kara; Musanhu, Christine Chiedza; Stevens, Wendy; Katzenstein, David; Ciaranello, Andrea; Barnabas, Ruanne; Braithwaite, Scott; Bendavid, Eran; Nathoo, Kusum J; van de Vijver, David; Wilson, David; Holmes, Charles; Bershteyn, Anna; Walker, Simon; Raizes, Elliot; Jani, Ilesh; Nelson, Lisa; Peeling, Rosanna; Terris-Prestholt, Fern; Murungu, Joseph; Mutasa-Apollo, Tsitsi; Hallett, Timothy; Revill, Paul


    There are inefficiencies in current approaches to monitoring patients on antiretroviral therapy (ART) in sub-Saharan Africa. Patients typically attend clinics every 1–3 months for clinical assessment, with clinic costs being comparable with costs of drugs themselves, CD4 counts are measured every 6 months, yet patients are rarely switched to second-line therapies. To ensure sustainability of treatment programmes a transition to more cost-effective ART deliver is needed. In contrast to the CD4 count, measurement of the level of HIV RNA in plasma (“viral load”) provides a direct measure of current treatment effect. Viral load informed differentiated care is a means of tailoring care whereby those with suppressed viral load have less frequent clinical visits and attention is paid to those with unsuppressed viral load to promote adherence and timely switching to a second-line regimen. The most feasible approach in many countries to measure viral load is by collecting dried blood spot (DBS) samples for testing in regional laboratories, although there have been concerns over the sensitivity/specificity of DBS to define treatment failure and the delay in receiving results. We use modelling to synthesize available evidence and evaluate the cost-effectiveness of viral load-informed differentiated care, account for limitations of DBS. We find that viral load-informed differentiated care using DBS is expected to be cost-effective and is recommended as the strategy for patient monitoring, although further empirical evidence as the approach is rolled out would be of value. We also explore the potential benefits of future availability of point-of-care (POC) viral load tests. PMID:26633768

  11. Continuous melt granulation to develop high drug loaded sustained release tablet of Metformin HCl

    Directory of Open Access Journals (Sweden)

    Pradnya Vaingankar


    The developed matrix tablet (75% drug loading resulted in 670 mg of weight for 500 mg dose strength and showed sustained drug release over 10 h. When compared, with conventional granulation techniques, it was observed that, under identical compression force, the tablet prepared by MG exhibited superior compactibility along with tablet hardness and optimal drug release profile. FTIR suggested nonexistence of chemical interaction between the drug and the other excipients while XRD and DSC analysis revealed the crystalline state of the drug. Furthermore, the results obtained from Raman spectroscopy proved the uniform distribution of the Metformin HCl and polymer in the final dosage form. This technology leads to the manufacture of sustained release matrix formulation with reduced tablet size of a high dose, highly water soluble drug otherwise difficult to process using standard batch-granulation.

  12. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.


    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  13. Sustained-release study on Exenatide loaded into mesoporous silica nanoparticles: in vitro characterization and in vivo evaluation. (United States)

    Chen, Cuiwei; Zheng, Hongyue; Xu, Junjun; Shi, Xiaowei; Li, Fanzhu; Wang, Xuanshen


    Exenatide (EXT), the first glucagon-like peptide-1 receptor agonist, has been approved as an adjunctive therapy for patients with type 2 diabetes. Due to EXT's short half-life, EXT must be administrated by continuous subcutaneous (s.c.) injection twice daily. In previous studies, many studies on EXT loaded into polymer materials carriers for sustained release had been reported. However, these carriers have some defects, such as hydrophobicity, low surface energy, low mechanical strength, and poor chemical stability. Therefore, this study aims to develop a novel drug delivery system, which is EXT loaded into well-ordered hexagonal mesoporous silica structures (EXT-SBA-15), to control the sustainability of EXT. SBA-15 was prepared by hydrothermal method with uniform size. Morphology of SBA-15 was employed by transmission electron microscopy. The pore size of SBA-15 was characterized by N2 adsorption-desorption isotherms. The in vitro drug release behavior and pharmacokinetics of EXT-SBA-15 were investigated. Furthermore, the blood glucose levels of diabetic mice were monitored after subcutaneous injection of EXT-Sol and EXT-SBA-15 to evaluate further the stable hypoglycemic effect of EXT-SBA-15. EXT-SBA-15 showed a higher drug loading efficiency (15.2 ± 2.0%) and sustained-release features in vitro. In addition, pharmacokinetic studies revealed that the EXT-SBA-15 treatment group extended the half-life t 1/2(β) to 14.53 ± 0.70 h compared with that of the EXT solution (EXT-Sol) treatment group (0.60 ± 0.08 h) in vivo. Results of the pharmacodynamics study show that the EXT-SBA-15 treatment group had inhibited blood glucose levels below 20 mmol/L for 25 days, and the lowest blood glucose level was 13 mmol/L on the 10th day. This study demonstrates that the EXT-SBA-15 delivery system can control the sustainability of EXT and contribute to improve EXT clinical use.

  14. Upregulation of matrix synthesis in chondrocyte-seeded agarose following sustained bi-axial cyclic loading

    Directory of Open Access Journals (Sweden)

    Belinda Pingguan-Murphy


    Full Text Available OBJECTIVES: The promotion of extracellular matrix synthesis by chondrocytes is a requisite part of an effective cartilage tissue engineering strategy. The aim of this in vitro study was to determine the effect of bi-axial cyclic mechanical loading on cell proliferation and the synthesis of glycosaminoglycans by chondrocytes in threedimensional cultures. METHOD: A strain comprising 10% direct compression and 1% compressive shear was applied to bovine chondrocytes seeded in an agarose gel during two 12-hour conditioning periods separated by a 12-hour resting period. RESULTS: The bi-axial-loaded chondrocytes demonstrated a significant increase in glycosaminoglycan synthesis compared with samples exposed to uni-axial or no loading over the same period (p<0.05. The use of a free-swelling recovery period prior to the loading regime resulted in additional glycosaminoglycan production and a significant increase in DNA content (p<0.05, indicating cell proliferation. CONCLUSIONS: These results demonstrate that the use of a bi-axial loading regime results in increased matrix production compared with uni-axial loading.

  15. Enhanced acute anti-inflammatory effects of CORM-2-loaded nanoparticles via sustained carbon monoxide delivery. (United States)

    Qureshi, Omer Salman; Zeb, Alam; Akram, Muhammad; Kim, Myung-Sic; Kang, Jong-Ho; Kim, Hoo-Seong; Majid, Arshad; Han, Inbo; Chang, Sun-Young; Bae, Ok-Nam; Kim, Jin-Ki


    The aim of this study was to enhance the anti-inflammatory effects of carbon monoxide (CO) via sustained release of CO from carbon monoxide-releasing molecule-2-loaded lipid nanoparticles (CORM-2-NPs). CORM-2-NPs were prepared by hot high pressure homogenization method using trilaurin as a solid lipid core and Tween 20/Span 20/Myrj S40 as surfactant mixture. The physicochemical properties of CORM-2-NPs were characterized and CO release from CORM-2-NPs was assessed by myoglobin assay. In vitro anti-inflammatory effects were evaluated by nitric oxide assay in lipopolysaccharide-stimulated RAW 264.7 macrophages. In vivo anti-inflammatory activity was investigated by measuring paw volumes and histological examination in carrageenan-induced rat paw edema. Spherical CORM-2-NPs were around 100nm with narrow particle size distribution. The sustained CO release from CORM-2-NPs was observed and the half-life of CO release increased up to 10 times compared with CORM-2 solution. CORM-2-NPs showed enhanced in vitro anti-inflammatory effects by inhibition of nitric oxide production. Edema volume in rat paw was significantly reduced after treatment with CORM-2-NPs. Taken together, CORM-2-NPs have a great potential for CO therapeutics against inflammation via sustained release of CO. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. A Reformed CDM - including new mechanisms for sustainable development

    Energy Technology Data Exchange (ETDEWEB)

    Holm Olsen, K.; Fenhann, J.


    The annual CD4CDM Perspectives Series features a topic of pivotal importance to the global carbon market. The series seeks to communicate the diverse insights and visions of leading actors in the carbon market to better inform the decisions of professionals and policymakers in developing countries. The second theme of the series focuses on how the CDM can be reformed in a post-2012 climate regime, including new mechanism for sustainable development. Seventeen contributors from the private sector, Designated National Authorities, the Executive Board, research, and development agencies present their perspective on meeting challenges such as the unequal regional distribution of CDM projects, concerns about environmental integrity and technology transfer, complex governance procedures, and questions about the CDM's contribution to sustainable development. The new ideas and solutions to these challenges proposed by the authors in this edition of Perspectives have been solicited to help professionals and policy makers make the best decisions in the lead-up to COP 15 in Copenhagen and beyond. (au)

  17. Behavior of duplex stainless steel casting defects under mechanical loadings

    Energy Technology Data Exchange (ETDEWEB)

    Jayet-Gendrot, S. [Electricite de France, 77 - Moret-sur-Loing (France). Dept. of Materials Study; Gilles, P.; Migne, C. [Societe Franco-Americaine de Constructions Atomiques (FRAMATOME), 92 - Paris-La-Defense (France)


    Several components in the primary circuit of pressurized water reactors are made of cast duplex stainless steels. This material contains small casting defects, mainly shrinkage cavities, due to the manufacturing process. In safety analyses, the structural integrity of the components is studied. In order to assess the real severity of the casting defects under mechanical loadings, an experimental program was carried out. It consisted of testing, under both cyclic and monotonic solicitations, three-point bend specimens containing either a natural defect (in the form of a localized cluster of cavities) or a machined notch having the dimensions of the cluster`s envelope. The tests are analyzed in order to develop a method that takes into account the behavior of castings defects in a more realistic fashion than by an envelope crack. Various approaches are investigated, including the search of equivalent defects or of criteria based on continuum mechanics concepts, and compared with literature data. This study shows the conservatism of current safety analyses in modelling casting defects by envelope semi-elliptical cracks and contributes to the development of alternative approaches. (author) 18 refs.

  18. Preparation and Evaluation of Dexamethasone-Loaded Electrospun Nanofiber Sheets as a Sustained Drug Delivery System

    Directory of Open Access Journals (Sweden)

    Jin Woo Lee


    Full Text Available Recently, electrospinning technology has been widely used as a processing method to make nanofiber sheets (NS for biomedical applications because of its unique features, such as ease of fabrication and high surface area. To develop a sustained dexamethasone (Dex delivery system, in this work, poly(ε-caprolactone-co-l-lactide (PCLA copolymer with controllable biodegradability was synthesized and further utilized to prepare electrospun Dex-loaded NS using water-insoluble Dex (Dex(b or water-soluble Dex (Dex(s. The Dex-NS obtained by electrospinning exhibited randomly oriented and interconnected fibrillar structures. The in vitro and in vivo degradation of Dex-NS was confirmed over a period of a few weeks by gel permeation chromatography (GPC and nuclear magnetic resonance (NMR. The evaluation of in vitro and in vivo Dex(b and Dex(s release from Dex-NS showed an initial burst of Dex(b at day 1 and, thereafter, almost the same amount of release as Dex(b for up to 28 days. In contrast, Dex(s-NS exhibited a small initial burst of Dex(s and a first-order releasing profile from Dex-NS. In conclusion, Dex-NS exhibited sustained in vitro and in vivo Dex(s release for a prolonged period, as well as controlled biodegradation of the NS over a defined treatment period.

  19. Effect of humidity on domain switching behaviors of BaTiO 3 single crystal under sustained load (United States)

    Jiang, B.; Bai, Y.; Chu, W. Y.; Shi, S. Q.; Qiao, L. J.; Su, Y. J.


    Domain switching behaviors of BaTiO 3 single crystal in humidity conditions were studied by polarized light microscopy (PLM) and atomic force microscopy (AFM). The results showed that the low humidity has no effect on both a- b domain configuration and a- c domain configuration under sustained load. However, the high humidity can promote a domain switching to c domain under sustained load. The difference of energy reduction induced by H 2O molecules between c domains and a( b) domains leads to this phenomenon.

  20. Biodegradation and cytotoxicity of ciprofloxacin-loaded hydroxyapatite-polycaprolactone nanocomposite film for sustainable bone implants. (United States)

    Nithya, Rajendran; Meenakshi Sundaram, Nachiappan


    In recent years there has been a steep increase in the number of orthopedic patients for many reasons. One major reason is osteomyelitis, caused by pyrogenic bacteria, with progressive infection of the bone or bone marrow and surrounding tissues. So antibiotics must be introduced during bone implantation to avoid prolonged infection. The objective of the study reported here was to prepare a composite film of nanocrystalline hydroxyapatite (HAp) and polycaprolactone (PCL) polymer loaded with ciprofloxacin, a frequently used antibiotic agent for bone infections. Nanocrystalline HAp was synthesized by precipitation method using the precursor obtained from eggshell. The nanocomposite film (HAp-PCL-ciprofloxacin) was prepared by solvent evaporation. Drug-release and biodegradation studies were undertaken by immersing the composite film in phosphate-buffered saline solution, while a cytotoxicity test was performed using the fibroblast cell line NIH-3T3 and osteoblast cell line MG-63. The pure PCL film had quite a low dissolution rate after an initial sharp weight loss, whereas the ciprofloxacin-loaded HAp-PCL nanocomposite film had a large weight loss due to its fast drug release. The composite film had higher water absorption than the pure PCL, and increasing the concentration of the HAp increased the water absorption. The in vitro cell-line study showed a good biocompatibility and bioactivity of the developed nanocomposite film. The prepared film will act as a sustainable bone implant in addition to controlled drug delivery.

  1. Structural concerns in dynamic drop loads on transfer lock mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Pfeiffer, P.A.; Moran, T.J.; Kulak, R.F. [Argonne National Lab., IL (United States). Reactor Engineering Div.


    Drop loads are usually low probability events that can generate substantial loading to the impacted structures. When the impacted structure contains slender elements, the concern about dynamic buckling must be addressed. The problem of interest here is a structure is also under significant preload, which must be taken into account in the transient analysis. For complex structures, numerical simulations are the only viable option for assessing the transient response to short duration impactive loads. this paper addresses several analysis issues of preloaded structures with slender members subjected to drop loads. A three-dimensional beam element is validated for use in dynamic buckling analysis. the numerical algorithm used to solve the transient response of preloaded structures is discussed. The methodology is applied to an inter-compartment lock that is under significant preloads, and subjected to a drop load.

  2. Failure mechanisms of aluminium foams under compressive loads

    Directory of Open Access Journals (Sweden)

    Sáenz, E.


    Full Text Available The purpose of this paper is the investigation of the major failure mechanisms of aluminium foams, which were obtained by powder metallurgy route, under compressive loads. The study was focused on two commonly aluminium alloys AlMg1Si or A 6061 and AlSi12. Due to the fact that the failure mechanisms strongly depend on the density and the macrostructural properties of the material, the mechanical properties always have to be correlated to the structural properties. Therefore, macrostructural investigations were used as a basis to establish the correlation between structural and mechanical properties. This was done with a commercially available image analysis system. The average cell size, the cell size distribution and the cell density (number of cells/area were obtained. In order to evaluate the influence of foaming direction on the cell morphology, some cross sections parallel to the foaming direction were prepared. For the characterization of the mechanical compression properties the compressive or upper yield strength (UYS, the densification strain (eD, the energy absorption (Ea and the efficiency (Eff were obtained. Furthermore, the failure behavior of the samples was in-situ observed with a digital video camera and continuously recorded during the test.

    El objetivo de este estudio es investigar los principales mecanismos de fallo de espumas de aluminio sometidas a cargas de compresión. Las espumas metálicas fueron obtenidas mediante el proceso pulvimetalúrgico, utilizándose como materia prima dos aleaciones comerciales AlMg1Si o A 6061 y AlSi12. Debido a que los mecanismos de fallo en este tipo de materiales depende fuertemente de la densidad y las características macroestructurales del material, en este estudio se busca correlacionar las propiedades mecánicas con estas características. La macroestructura se caracterizó mediante análisis de imagen. El tamaño de celda promedio, la distribución de tamaño y la densidad de

  3. Integrity of the osteocyte bone cell network in osteoporotic fracture: Implications for mechanical load adaptation (United States)

    Kuliwaba, J. S.; Truong, L.; Codrington, J. D.; Fazzalari, N. L.


    The human skeleton has the ability to modify its material composition and structure to accommodate loads through adaptive modelling and remodelling. The osteocyte cell network is now considered to be central to the regulation of skeletal homeostasis; however, very little is known of the integrity of the osteocyte cell network in osteoporotic fragility fracture. This study was designed to characterise osteocyte morphology, the extent of osteocyte cell apoptosis and expression of sclerostin protein (a negative regulator of bone formation) in trabecular bone from the intertrochanteric region of the proximal femur, for postmenopausal women with fragility hip fracture compared to age-matched women who had not sustained fragility fracture. Osteocyte morphology (osteocyte, empty lacunar, and total lacunar densities) and the degree of osteocyte apoptosis (percent caspase-3 positive osteocyte lacunae) were similar between the fracture patients and non-fracture women. The fragility hip fracture patients had a lower proportion of sclerostin-positive osteocyte lacunae in comparison to sclerostin-negative osteocyte lacunae, in contrast to similar percent sclerostin-positive/sclerostin-negative lacunae for non-fracture women. The unexpected finding of decreased sclerostin expression in trabecular bone osteocytes from fracture cases may be indicative of elevated bone turnover and under-mineralisation, characteristic of postmenopausal osteoporosis. Further, altered osteocytic expression of sclerostin may be involved in the mechano-responsiveness of bone. Optimal function of the osteocyte cell network is likely to be a critical determinant of bone strength, acting via mechanical load adaptation, and thus contributing to osteoporotic fracture risk.

  4. Mapping the Indicators. An Analysis of Sustainable Development Requirements of Selected Market Mechanisms and Multilateral Institutions

    DEFF Research Database (Denmark)

    Arens, Christof; Mersmann, Florian; Beuermann, Christiane

    in achieving sustainable development based on their national development priorities and strategies. However, complying with the second objective turned out to be problematic. Registered projects appeared that had no proven sustainable development benefits, or even perceived negative impacts. Consequently....... A robust assessment of the impact of sustainable development in CDM projects is important to ensure the social and ecological integrity of the mechanism and compliance with the objectives of sustainable development as stated in the Kyoto Protocol. Research and best practice experience into how sustainable...... development issues are integrated into mitigation actions through the CDM Sustainable Development Tool and other respective standards can help inform the development of Nationally Appropriate Mitigation Actions and future mechanisms on sustainable development assessment methods. As sustainable development...

  5. Thermo-mechanical loading response of hardened and tempered iron-carbon based alloys

    NARCIS (Netherlands)

    Morra, P.V.


    The mechanisms causing long term changes of materials at mild operating conditions, i.e. relatively low temperatures and loads, has not received as much attention as that for high temperature operating conditions because small strains are involved. Nevertheless the thermo-mechanical loading response

  6. Load application for the contact mechanics analysis and wear prediction of total knee replacement. (United States)

    Zhang, Jing; Chen, Zhenxian; Wang, Ling; Li, Dichen; Jin, Zhongmin


    Tibiofemoral contact forces in total knee replacement have been measured at the medial and lateral sites respectively using an instrumented prosthesis, and predicted from musculoskeletal multibody dynamics models with a reasonable accuracy. However, it is uncommon that the medial and lateral forces are applied separately to replace a total axial load according to the ISO standard in the majority of current finite element analyses. In this study, we quantified the different effects of applying the medial and lateral loads separately versus the traditional total axial load application on contact mechanics and wear prediction of a patient-specific knee prosthesis. The load application position played an important role under the medial-lateral load application. The loading set which produced the closest load distribution to the multibody dynamics model was used to predict the contact mechanics and wear for the prosthesis and compared with the total axial load application. The medial-lateral load distribution using the present method was found to be closer to the multibody dynamics prediction than the traditional total axial load application, and the maximum contact pressure and contact area were consistent with the corresponding load variation. The predicted total volumetric wear rate and area were similar between the two load applications. However, the split of the predicted wear volumes on the medial and the lateral sides was different. The lateral volumetric wear rate was 31.46% smaller than the medial from the traditional load application prediction, while from the medial-lateral load application, the lateral side was only 11.8% smaller than the medial. The medial-lateral load application could provide a new and more accurate method of load application for patient-specific preclinical contact mechanics and wear prediction of knee implants.

  7. The interface of mechanical loading and biological variables as they pertain to the development of tendinosis. (United States)

    Thornton, G M; Hart, D A


    Different tendons are designed to withstand different mechanical loads in their individual environments. Variable physiologic loading ranges and correspondingly different injury thresholds lead to tendon heterogeneity. Also, tendon heterogeneity is evident when examining how different tendons regulate their response to changes in mechanical loading (over- and under-loading). The response of tendons to changes in mechanical loading plays an important role in the induction and progression of tendinosis which is tendon degeneration without inflammation. Tendon overuse injury is likely related to abnormal mechanical loading that deviates from normal mechanical loading in magnitude, frequency, duration and/or direction. Mechanical loading that results in tendon overuse injury can initiate a repair process but, after failed initial repair, non-resolving chronic attempted repair appears to lead to a "smoldering" fibrogenesis. Contributions of regulatory components, including minor components in the "nerve-mast cell-myofibroblast axis", are key features in the development and progression of tendinosis. Hormonal and genetic factors may also influence risk for tendinosis. Further understanding of how tendinosis induction is related to mechanical use/overuse, how tendinosis progression is related to abnormal regulation of attempted repair, and how induction and/or progression are modulated by other risk factors may lead to interventions that mitigate risk and enhance functional repair.

  8. Sustained attention ability in schizophrenia: Investigation of conflict monitoring mechanisms. (United States)

    Hoonakker, Marc; Doignon-Camus, Nadège; Marques-Carneiro, José Eduardo; Bonnefond, Anne


    The main goal of the current study was to assess, with a time-on-task approach, sustained attention ability in schizophrenia, and to investigate conflict monitoring underlying this ability. Behavioral and event-related potentials data (N2 and P3a amplitudes) were recorded in a long-lasting sustained attention Go/NoGo task (sustained attention to response task, SART), over a period of 30min, in 29 patients with schizophrenia and 29 pair-matched healthy subjects. Our results revealed spared sustained attention ability in patients throughout the task. Impairment of conflict detection (N2) in patients was particularly significant at the end of the task. Furthermore, both schizophrenia and healthy subjects exhibited a decline in conflict detection from the beginning to the middle of the task. Whereas controls' conflict detection recovered in the last part of the task, patients' did not, suggesting a deficit in recovery processes reflecting a lack of additional resources sustained attention Go/NoGo task. Conflict resolution (P3a) was preserved throughout the task in both groups. Conflict monitoring processes are increasingly impaired in schizophrenia during a long-lasting sustained attention Go/NoGo task. This impairment at the end of the task may rely on deficit in recovery processes, rather than a deficit in conflict detection per se in schizophrenia. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  9. Mechanical load induces sarcoplasmic wounding and FGF release in differentiated human skeletal muscle cultures (United States)

    Clarke, M. S.; Feeback, D. L.


    The transduction mechanism (or mechanisms) responsible for converting a mechanical load into a skeletal muscle growth response are unclear. In this study we have used a mechanically active tissue culture model of differentiated human skeletal muscle cells to investigate the relationship between mechanical load, sarcolemma wounding, fibroblast growth factor release, and skeletal muscle cell growth. Using the Flexcell Strain Unit we demonstrate that as mechanical load increases, so too does the amount of sarcolemma wounding. A similar relationship was also observed between the level of mechanical load inflicted on the cells and the amount of bFGF (FGF2) released into the surrounding medium. In addition, we demonstrate that the muscle cell growth response induced by chronic mechanical loading in culture can be inhibited by the presence of an antibody capable of neutralizing the biological activity of FGF. This study provides direct evidence that mechanically induced, sarcolemma wound-mediated FGF release is an important autocrine mechanism for transducing the stimulus of mechanical load into a skeletal muscle growth response.

  10. Chlorogenic acid loaded chitosan nanoparticles with sustained release property, retained antioxidant activity and enhanced bioavailability

    Directory of Open Access Journals (Sweden)

    Ilaiyaraja Nallamuthu


    Full Text Available In this study, chlorogenic acid (CGA, a phenolic compound widely distributed in fruits and vegetables, was encapsulated into chitosan nanoparticles by ionic gelation method. The particles exhibited the size and zeta potential of 210 nm and 33 mV respectively. A regular, spherical shaped distribution of nanoparticles was observed through scanning electron microscopy (SEM and the success of entrapment was confirmed by FTIR analysis. The encapsulation efficiency of CGA was at about 59% with the loading efficiency of 5.2%. In vitro ABTS assay indicated that the radical scavenging activity of CAG was retained in the nanostructure and further, the release kinetics study revealed the burst release of 69% CGA from nanoparticles at the end of 100th hours. Pharmacokinetic analysis in rats showed a lower level of Cmax, longer Tmax, longer MRT, larger AUC0–t and AUC0–∞ for the CGA nanoparticles compared to free CGA. Collectively, these results suggest that the synthesised nanoparticle with sustained release property can therefore ease the fortification of food-matrices targeted for health benefits through effective delivery of CGA in body.

  11. Response mechanisms of concrete under impulsive tensile loading

    NARCIS (Netherlands)

    Weerheijm, J.; Forquin, P.


    The response of concrete up to complete failure in tension is represented in the load deformation relation. The characteristic parameters are the ultimate strength, stiffness in the ascending branch and the fracture energy. All these parameters depend on concrete composition and environmental

  12. The effect of mechanical loads on the degradation of aliphatic biodegradable polyesters. (United States)

    Li, Ying; Chu, Zhaowei; Li, Xiaoming; Ding, Xili; Guo, Meng; Zhao, Haoran; Yao, Jie; Wang, Lizhen; Cai, Qiang; Fan, Yubo


    Aliphatic biodegradable polyesters have been the most widely used synthetic polymers for developing biodegradable devices as alternatives for the currently used permanent medical devices. The performances during biodegradation process play crucial roles for final realization of their functions. Because physiological and biochemical environment in vivo significantly affects biodegradation process, large numbers of studies on effects of mechanical loads on the degradation of aliphatic biodegradable polyesters have been launched during last decades. In this review article, we discussed the mechanism of biodegradation and several different mechanical loads that have been reported to affect the biodegradation process. Other physiological and biochemical factors related to mechanical loads were also discussed. The mechanical load could change the conformational strain energy and morphology to weaken the stability of the polymer. Besides, the load and pattern could accelerate the loss of intrinsic mechanical properties of polymers. This indicated that investigations into effects of mechanical loads on the degradation should be indispensable. More combination condition of mechanical loads and multiple factors should be considered in order to keep the degradation rate controllable and evaluate the degradation process in vivo accurately. Only then can the degradable devise achieve the desired effects and further expand the special applications of aliphatic biodegradable polyesters.

  13. Structural Stability of a Stiffened Aluminum Fuselage Panel Subjected to Combined Mechanical and Internal Pressure Loads (United States)

    Rouse, Marshall; Young, Richard D.; Gehrki, Ralph R.


    Results from an experimental and analytical study of a curved stiffened aluminum panel subjected to combined mechanical and internal pressure loads are presented. The panel loading conditions were simulated using a D-box test fixture. Analytical buckling load results calculated from a finite element analysis are presented and compared to experimental results. Buckling results presented indicate that the buckling load of the fuselage panel is significantly influenced by internal pressure loading. The experimental results suggest that the stress distribution is uniform in the panel prior to buckling. Nonlinear finite element analysis results correlates well with experimental results up to buckling.

  14. The 2-oxoglutarate carrier promotes liver cancer by sustaining mitochondrial GSH despite cholesterol loading

    Directory of Open Access Journals (Sweden)

    Anna Baulies


    Full Text Available Cancer cells exhibit mitochondrial cholesterol (mt-cholesterol accumulation, which contributes to cell death resistance by antagonizing mitochondrial outer membrane (MOM permeabilization. Hepatocellular mt-cholesterol loading, however, promotes steatohepatitis, an advanced stage of chronic liver disease that precedes hepatocellular carcinoma (HCC, by depleting mitochondrial GSH (mGSH due to a cholesterol-mediated impairment in mGSH transport. Whether and how HCC cells overcome the restriction of mGSH transport imposed by mt-cholesterol loading to support mGSH uptake remains unknown. Although the transport of mGSH is not fully understood, SLC25A10 (dicarboxylate carrier, DIC and SLC25A11 (2-oxoglutarate carrier, OGC have been involved in mGSH transport, and therefore we examined their expression and role in HCC. Unexpectedly, HCC cells and liver explants from patients with HCC exhibit divergent expression of these mitochondrial carriers, with selective OGC upregulation, which contributes to mGSH maintenance. OGC but not DIC downregulation by siRNA depleted mGSH levels and sensitized HCC cells to hypoxia-induced ROS generation and cell death as well as impaired cell growth in three-dimensional multicellular HCC spheroids, effects that were reversible upon mGSH replenishment by GSH ethyl ester, a membrane permeable GSH precursor. We also show that OGC regulates mitochondrial respiration and glycolysis. Moreover, OGC silencing promoted hypoxia-induced cardiolipin peroxidation, which reversed the inhibition of cholesterol on the permeabilization of MOM-like liposomes induced by Bax or Bak. Genetic OGC knockdown reduced the ability of tumor-initiating stem-like cells to induce liver cancer. These findings underscore the selective overexpression of OGC as an adaptive mechanism of HCC to provide adequate mGSH levels in the face of mt-cholesterol loading and suggest that OGC may be a novel therapeutic target for HCC treatment. Keywords: Cholesterol

  15. A model for chemically-induced mechanical loading on MEMS

    DEFF Research Database (Denmark)

    Amiot, Fabien


    , and displacements). As these phenomena usually arise from species adsorption, adsorbate modification or surface reconstruction, they are surface-related by nature and thus require some dedicated mechanical modeling. The accompanying mechanical modeling proposed herein is intended to represent the chemical part......The development of full displacement field measurements as an alternative to the optical lever technique to measure the mechanical response for microelectro-mechanical systems components in their environment calls for a modeling of chemically-induced mechanical fields (stress, strain...

  16. Mechanical Behaviour of Bolted Joints Under Impact Rates of Loading (United States)


    schematic of equipment for Hopkinson bar data acquisition and high speed capture calibration Figure AC1 1/2- Wheatstone bridge circuit Figure AC2 1/2... Wheatstone bridge Hopkinson incident bar schematic, where numbers in triangles represent pin connection in Ectron 513-2A enclosure Figure AC3 Full... Wheatstone bridge circuit Figure AC4 Full Wheatstone bridge Hopkinson transmission bar and load cell schematic, where numbers in triangles represent

  17. The creation of racks and nanopores creation in various allotropes of boron due to the mechanical loads (United States)

    Sadeghzadeh, S.


    Two-dimensional (2D) materials have recently attracted a great attraction. This paper provides a detailed discussion on the rupture mechanisms of different allotropes of boron. As a new 2D material by using a reactive molecular dynamics model, probable types of rupture for borophene sheets were studied, among which two dominant mechanisms were observed: creation of the cracks and formation of nanopores. The results obtained are compared to those for graphene and h-BN nano sheets, although the rupture mechanism was completely different from the graphene and h-BN sheets. The simulations suggested that borophene might remain more stable against external mechanical loads than graphene and BN sheets. Cracking leads to larger strain along the loading direction, whereas the creation of local pores spends the imposed energy for breaking the internal bonds and so flowing the external energy into the various bonds increases the number of pores. For the armchair-types, cracking is a dominant mechanism while for the zigzag-type the common mechanism is the creation of nanopores. These interesting results may help to design a new class of semiconductors that remain stable even when are sustaining uncontrollable external stresses.

  18. Anterior cruciate ligament injuries in soccer: Loading mechanisms, risk factors, and prevention programs

    Directory of Open Access Journals (Sweden)

    Boyi Dai


    Full Text Available Anterior cruciate ligament (ACL injuries are common in soccer. Understanding ACL loading mechanisms and risk factors for ACL injury is critical for designing effective prevention programs. The purpose of this review is to summarize the relevant literature on ACL loading mechanisms, ACL injury risk factors, and current ACL injury prevention programs for soccer players. Literature has shown that tibial anterior translation due to shear force at the proximal end of tibia is the primary ACL loading mechanism. No evidence has been found showing that knee valgus moment is the primary ACL loading mechanism. ACL loading mechanisms are largely ignored in previous studies on risk factors for ACL injury. Identified risk factors have little connections to ACL loading mechanisms. The results of studies on ACL injury prevention programs for soccer players are inconsistent. Current ACL injury prevention programs for soccer players are clinically ineffective due to low compliance. Future studies are urgently needed to identify risk factors for ACL injury in soccer that are connected to ACL loading mechanisms and have cause-and-effect relationships with injury rate, and to develop new prevention programs to improve compliance.

  19. Flexibility mechanisms and sustainable development: Lessons from five AIJ projects

    NARCIS (Netherlands)

    Gupta, J.; van Beukering, P.J.H.; van Asselt, H.D.; Brander, L.M.; Hess, S.M.; van der Leeuw, K.


    Do 'Activities Implemented Jointly' (AIJ) projects contribute to sustainable development in the host countries? Which factors have contributed to the success or failure of the projects? Five AIJ projects were examined, accounting for 90% of the total AIJ expenditure of the Dutch government. The

  20. Role of Loading Device on Single-Molecule Mechanical Manipulation of Free Energy Landscape

    CERN Document Server

    Yoon, Gwonchan; Eom, Kilho


    Single-molecule mechanical manipulation has enabled the quantitative understanding of the kinetics of bond ruptures as well as protein unfolding mechanism. Single-molecule experiments with theoretical models have allowed one to gain insight into free energy landscape for chemical bond and/or protein folding. For mechanically induced bond rupture, the bond-rupture kinetics may be governed by loading device. However, the role of loading device on the kinetics of mechanical rupture has been rarely received much attention until recently. In this work, we have theoretically and/or computationally studied the effect of loading-device stiffness on the kinetics of mechanical unfolding. Specifically, we have considered a one-dimensional model for a bond rupture whose kinetics is depicted by Kramers' theory. It is elucidated that the kinetics of bond rupture is determined by force constant of loading device. The Brownian dynamics simulation of a bond rupture is considered in order to validate our theory. It is illustra...

  1. Mechanical properties of two-way different configurations of prestressed concrete members subjected to axial loading

    Directory of Open Access Journals (Sweden)

    Chaobi Zhang


    Full Text Available In order to analyze the mechanical properties of two-way different configurations of prestressed concrete members subjected to axial loading, a finite element model based on the nuclear power plant containments is demonstrated. This model takes into account the influences of different principal stress directions, the uniaxial or biaxial loading, and biaxial loading ratio. The displacement-controlled load is applied to obtain the stress–strain response. The simulated results indicate that the differences of principal stress axes have great effects on the stress–strain response under uniaxial loading. When the specimens are subjected to biaxial loading, the change trend of stress with the increase of loading ratio is obviously different along different layout directions. In addition, correlation experiments and finite element analyses were conducted to verify the validity and reliability of the analysis in this study.

  2. The Effects of Load Carriage and Muscle Fatigue on Lower-Extremity Joint Mechanics (United States)

    Wang, He; Frame, Jeff; Ozimek, Elicia; Leib, Daniel; Dugan, Eric L.


    Military personnel are commonly afflicted by lower-extremity overuse injuries. Load carriage and muscular fatigue are major stressors during military basic training. Purpose: To examine effects of load carriage and muscular fatigue on lower-extremity joint mechanics during walking. Method: Eighteen men performed the following tasks: unloaded…

  3. Kinematics and Load Formulation of Engine Crank Mechanism


    Nigus, Hailemariam


    International audience; This paper presents the kinematics formulation of an internal combustion engine crank mechanism. The kinematics formulation of the crank mechanism is done using vector loop method and cosine rule are applied to describe the position of the piston. Following the velocity of piston and connecting rod is performed by differentiating the position in terms of the crank angle and connecting rod angle respectively. The acceleration equation with brief form is derived from the...

  4. Skeletal adaptation to external loads optimizes mechanical properties: fact or fiction (United States)

    Turner, R. T.


    The skeleton adapts to a changing mechanical environment but the widely held concept that bone cells are programmed to respond to local mechanical loads to produce an optimal mechanical structure is not consistent with the high frequency of bone fractures. Instead, the author suggests that other important functions of bone compete with mechanical adaptation to determine structure. As a consequence of competing demands, bone architecture never achieves an optimal mechanical structure. c2001 Lippincott Williams & Wilkins, Inc.

  5. Bioactive Glass Nanoparticles as a New Delivery System for Sustained 5-Fluorouracil Release: Characterization and Evaluation of Drug Release Mechanism

    Directory of Open Access Journals (Sweden)

    Abeer M. El-Kady


    Full Text Available Bioactive glass nanoparticles were synthesized and tested for the first time as a new delivery system for sustained 5-fluorouracil (5-FU release. They were characterized by TEM, DTA, TGA, and FT-IR. The porosity % and specific surface area of glass nanoparticles were 85.59% and 378.36 m2/g, respectively. The in vitro bioactivity evaluation confirmed that bioactive glass disks prepared from these nanoparticles could induce hydroxyapatite layer over their surfaces in simulated body fluid. The in vitro drug release experiment indicated that glass nanoparticles could serve as long-term local delivery vehicles for sustained 5-FU release. The release profile of 5-FU showed an initial fast release stage followed by a second stage of slower release. The initial burst release of 5-FU in the first day was about 23% (28.92 mg·L−1 of the total amount of loaded 5-FU, while the final cumulative percentage of the 5-FU released after 32 days was about 45.6% (57.31 mg·L−1 of the total amount of loaded 5-FU. The application of different mathematical models indicated that 5-FU was released by diffusion controlled mechanism and suggested that its release rate was dependent on glass particles dissolution, changes of surface area as well as diameter of glass particles, and concentration of loaded drug.

  6. Impact of Cyclic Loading on Chloride Diffusivity and Mechanical Performance of RC Beams under Seawater Corrosion

    Directory of Open Access Journals (Sweden)

    Sen Pang


    Full Text Available An experimental study was conducted to investigate the impact of cyclic loading on the mechanical performance and chloride diffusivity of RC beams exposed to seawater wet-dry cycles. To induce initial damage to RC beam specimen, cyclic loading controlled by max load and cycles was applied. Then beam specimens underwent 240 wet-dry cycles of seawater. Results show that the chloride content increased as max load and cycle increased. The chloride content at steel surface increased approximatively linearly as average crack width increased. Moreover, the max load had more influence on chloride content at steel surface than cycle. The difference of average chloride diffusion coefficient between tension and compression concrete was little at uncracked position. Average chloride diffusion coefficient increased as crack width increased when crack width was less than 0.11 mm whereas the increasing tendency was weak when crack width exceeded 0.11 mm. The residual yield load and ultimate load of RC beams decreased as max load and cycle increased. Based on univariate analysis of variance, the max load had more adverse effect on yield load and ultimate load than cycle.

  7. Mechanisms of peer tutoring on optimizing cognitive load during knowledge sharing in learning networks

    NARCIS (Netherlands)

    Hsiao, Amy; Brouns, Francis; Sloep, Peter


    Hsiao, Y. P., Brouns, F., & Sloep, P. B. (2010, 15 April). Mechanisms of peer tutoring on optimizing cognitive load during knowledge sharing in learning networks. Presentation at NELLL Colloqium, Heerlen, The Netherlands: Open University of the Netherlands.

  8. Mechanization and new technologies for the control and the sustainability of agricultural and forestry systems

    Directory of Open Access Journals (Sweden)

    The Editors


    Full Text Available Abstract Book of the Congress:Mechanization and new technologies for the control and the sustainability of agricultural and forestry systems Alghero, Italy, 29th May - 1st June 2016

  9. Mechanical behaviour of adhesive joint under tensile and shear loading

    NARCIS (Netherlands)

    Jiang, X.; Kolstein, M.H.; Bijlaard, F.S.K.


    Due to various advantages of Fibre-Reinforced Polymer (FRP) decks, the FRP to steel composite bridge system is being increasingly used in new bridge structures as well as rehabilitation projects for old bridges. This paper focuses on the mechanical behaviours and failure modes of the

  10. Hydrogen Embrittlement - Loading Rate Effects in Fracture Mechanics Testing

    NARCIS (Netherlands)

    Koers, R.W.J.; Krom, A.H.M.; Bakker, A.


    The fitness for purpose methodology is more and more used in the oil and gas industry to evaluate the significance of pre-existing flaws and material deficiencies with regard to the suitability of continued operation of equipment. In this methodology, traditional fracture mechanics is integrated

  11. Combined loading effects on the fracture mechanics behavior of line pipes

    Energy Technology Data Exchange (ETDEWEB)

    Bravo, R.E.; Cravero, S.; Ernst, H.A. [Tenaris Group, Campana (Argentina). SIDERCA R and D Center


    For certain applications, pipelines may be submitted to biaxial loading situations. In these cases, it is not clear the influence of the biaxial loading on the fracture mechanics behavior of cracked pipelines. For further understanding of biaxial loading effects, this work presents a numerical simulation of ductile tearing in a circumferentially surface cracked pipe under biaxial loading using the computational cell methodology. The model was adjusted with experimental results obtained in laboratory using single edge cracked under tension (SENT) specimens. These specimens appear as the better alternative to conventional fracture specimens to characterize fracture toughness of cracked pipes. The negligible effect of biaxial loadings on resistance curves was demonstrated. To guarantee the similarities of stress and strains fields between SENT specimens and cracked pipes subjected to biaxial loading, a constraint study using the J-Q methodology and the h parameter was used. The constraint study gives information about the characteristics of the crack-tip conditions. (author)

  12. Mechanical Properties of a Metal Powder-Loaded Polyurethane Foam

    Energy Technology Data Exchange (ETDEWEB)

    C. L. Neuschwanger; L. L. Whinnery; S. H. Goods


    Quasi-static compression tests have been performed on polyurethane foam specimens. The modulus of the foam exhibited a power-law dependence with respect to density of the form: E* {proportional_to} {rho}*{sup n}, where n = 1.7. The modulus data is well described by a simple geometric model (attributed to the work of Gibson and Ashby) for closed-cell foam in which the stiffness of the foam is governed by the flexure of the cell struts and cell walls. The compressive strength of the foam is also found to follow a power-law behavior with respect to foam density. In this instance, Euler buckling is used to rationalize the density dependence. The modulus of the polyurethane foam was modified by addition of a gas atomized, spherical aluminum powder. Additions of 30 and 50 weight percent of the powder significantly increased the foam modulus. However, there were only slight increases in modulus with 5 and 10 weight percent additions of the metal powder. Strength was also slightly increased at high loading fractions of powder. This increase in modulus and strength could be predicted by combining the above geometric model with a well-known model describing the effect on modulus of a rigid dispersoid in a compliant matrix.

  13. Reliability of Mechanical Structures with Considering Seismic Loading

    Directory of Open Access Journals (Sweden)

    Drahomír RYCHECKÝ


    Full Text Available The paper deals with summarization of methods used in seismic response evaluation of mechanical structures. The seismic evaluation of structures is inseparable condition in the design of hazardous facilities such as nuclear power plants. Based on demanded results, different methods can be used. For instance, when the anchorage of the structure is determinative, the equivalent static method (ESM can be advantageously used. To evaluate complex seismic response of a large mechanical structure the ESM is un-sufficient and e.g. for steady-state response of the structure the response spectrum method (RSM can be employed [3]. The RSM combines the response based on known mode shapes. Applying direct time-history (accelerogram is also possibility but time consuming. The paper contains definition of seismic safety factor for determining safety reserve of structures. All methods are applied on a sample example. Obtained results of each method are compared and discussed.

  14. Self-assembly of amphiphilic Janus dendrimers into mechanically robust supramolecular hydrogels for sustained drug release. (United States)

    Nummelin, Sami; Liljeström, Ville; Saarikoski, Eve; Ropponen, Jarmo; Nykänen, Antti; Linko, Veikko; Seppälä, Jukka; Hirvonen, Jouni; Ikkala, Olli; Bimbo, Luis M; Kostiainen, Mauri A


    Compounds that can gelate aqueous solutions offer an intriguing toolbox to create functional hydrogel materials for biomedical applications. Amphiphilic Janus dendrimers with low molecular weights can readily form self-assembled fibers at very low mass proportion (0.2 wt %) to create supramolecular hydrogels (G'≫G'') with outstanding mechanical properties and storage modulus of G'>1000 Pa. The G' value and gel melting temperature can be tuned by modulating the position or number of hydrophobic alkyl chains in the dendrimer structure; thus enabling exquisite control over the mesoscale material properties in these molecular assemblies. The gels are formed within seconds by simple injection of ethanol-solvated dendrimers into an aqueous solution. Cryogenic TEM, small-angle X-ray scattering, and SEM were used to confirm the fibrous structure morphology of the gels. Furthermore, the gels can be efficiently loaded with different bioactive cargo, such as active enzymes, peptides, or small-molecule drugs, to be used for sustained release in drug delivery. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Mechanical and transport properties of IBAD/EDDC-SmBCO coated conductor tapes during fatigue loading (United States)

    Shin, Hyung-Seop; Dedicatoria, Marlon J.


    In electrical devices like superconducting motor, generator and SMES, HTS coated conductor (CC) tapes will be subjected to alternating stress or strain during manufacturing and operation. The repeated loading will affect the mechanical integrity and eventually the electrical transport property of CC tapes. Therefore in such applications, electro-mechanical property of CC tapes should be evaluated. In this study, the endurance of an IBAD/EDDC-SmBCO CC tape under high-cycle fatigue loading has been evaluated. Applied maximum stress and fatigue life ( S-N) relation was obtained at 77 K. The mechanical properties and the critical current, I c, of the sample under fatigue loading were investigated at 77 K. Considering the practical operating environment, the effect of the stress ratio R, on the degradation behavior of I c under fatigue loading was also examined.

  16. Effects of mechanical repetitive load on bone quality around implants in rat maxillae.

    Directory of Open Access Journals (Sweden)

    Yusuke Uto

    Full Text Available Greater understanding and acceptance of the new concept "bone quality", which was proposed by the National Institutes of Health and is based on bone cells and collagen fibers, are required. The novel protein Semaphorin3A (Sema3A is associated with osteoprotection by regulating bone cells. The aims of this study were to investigate the effects of mechanical loads on Sema3A production and bone quality based on bone cells and collagen fibers around implants in rat maxillae. Grade IV-titanium threaded implants were placed at 4 weeks post-extraction in maxillary first molars. Implants received mechanical loads (10 N, 3 Hz for 1800 cycles, 2 days/week for 5 weeks from 3 weeks post-implant placement to minimize the effects of wound healing processes by implant placement. Bone structures, bone mineral density (BMD, Sema3A production and bone quality based on bone cells and collagen fibers were analyzed using microcomputed tomography, histomorphometry, immunohistomorphometry, polarized light microscopy and birefringence measurement system inside of the first and second thread (designated as thread A and B, respectively, as mechanical stresses are concentrated and differently distributed on the first two threads from the implant neck. Mechanical load significantly increased BMD, but not bone volume around implants. Inside thread B, but not thread A, mechanical load significantly accelerated Sema3A production with increased number of osteoblasts and osteocytes, and enhanced production of both type I and III collagen. Moreover, mechanical load also significantly induced preferential alignment of collagen fibers in the lower flank of thread B. These data demonstrate that mechanical load has different effects on Sema3A production and bone quality based on bone cells and collagen fibers between the inside threads of A and B. Mechanical load-induced Sema3A production may be differentially regulated by the type of bone structure or distinct stress distribution

  17. Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load. (United States)

    Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M


    Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

  18. Bimatoprost-loaded ocular inserts as sustained release drug delivery systems for glaucoma treatment: in vitro and in vivo evaluation.

    Directory of Open Access Journals (Sweden)

    Juçara Ribeiro Franca

    Full Text Available The purpose of the present study was to develop and assess a novel sustained-release drug delivery system of Bimatoprost (BIM. Chitosan polymeric inserts were prepared using the solvent casting method and characterized by swelling studies, infrared spectroscopy, differential scanning calorimetry, drug content, scanning electron microscopy and in vitro drug release. Biodistribution of 99mTc-BIM eye drops and 99mTc-BIM-loaded inserts, after ocular administration in Wistar rats, was accessed by ex vivo radiation counting. The inserts were evaluated for their therapeutic efficacy in glaucomatous Wistar rats. Glaucoma was induced by weekly intracameral injection of hyaluronic acid. BIM-loaded inserts (equivalent to 9.0 µg BIM were administered once into conjunctival sac, after ocular hypertension confirmation. BIM eye drop was topically instilled in a second group of glaucomatous rats for 15 days days, while placebo inserts were administered once in a third group. An untreated glaucomatous group was used as control. Intraocular pressure (IOP was monitored for four consecutive weeks after treatment began. At the end of the experiment, retinal ganglion cells and optic nerve head cupping were evaluated in the histological eye sections. Characterization results revealed that the drug physically interacted, but did not chemically react with the polymeric matrix. Inserts sustainedly released BIM in vitro during 8 hours. Biodistribution studies showed that the amount of 99mTc-BIM that remained in the eye was significantly lower after eye drop instillation than after chitosan insert implantation. BIM-loaded inserts lowered IOP for 4 weeks, after one application, while IOP values remained significantly high for the placebo and untreated groups. Eye drops were only effective during the daily treatment period. IOP results were reflected in RGC counting and optic nerve head cupping damage. BIM-loaded inserts provided sustained release of BIM and seem to be a

  19. Mechanical Loading Attenuates Radiation-Induced Bone Loss in Bone Marrow Transplanted Mice (United States)

    Govey, Peter M.; Zhang, Yue; Donahue, Henry J.


    Exposure of bone to ionizing radiation, as occurs during radiotherapy for some localized malignancies and blood or bone marrow cancers, as well as during space travel, incites dose-dependent bone morbidity and increased fracture risk. Rapid trabecular and endosteal bone loss reflects acutely increased osteoclastic resorption as well as decreased bone formation due to depletion of osteoprogenitors. Because of this dysregulation of bone turnover, bone’s capacity to respond to a mechanical loading stimulus in the aftermath of irradiation is unknown. We employed a mouse model of total body irradiation and bone marrow transplantation simulating treatment of hematologic cancers, hypothesizing that compression loading would attenuate bone loss. Furthermore, we hypothesized that loading would upregulate donor cell presence in loaded tibias due to increased engraftment and proliferation. We lethally irradiated 16 female C57Bl/6J mice at age 16 wks with 10.75 Gy, then IV-injected 20 million GFP(+) total bone marrow cells. That same day, we initiated 3 wks compression loading (1200 cycles 5x/wk, 10 N) in the right tibia of 10 of these mice while 6 mice were irradiated, non-mechanically-loaded controls. As anticipated, before-and-after microCT scans demonstrated loss of trabecular bone (-48.2% Tb.BV/TV) and cortical thickness (-8.3%) at 3 wks following irradiation. However, loaded bones lost 31% less Tb.BV/TV and 8% less cortical thickness (both pbones also had significant increases in trabecular thickness and tissue mineral densities from baseline. Mechanical loading did not affect donor cell engraftment. Importantly, these results demonstrate that both cortical and trabecular bone exposed to high-dose therapeutic radiation remain capable of an anabolic response to mechanical loading. These findings inform our management of bone health in cases of radiation exposure. PMID:27936104

  20. Load redistribution mechanism in damage tolerant and redundant truss structure

    DEFF Research Database (Denmark)

    Marhadi, Kun Saptohartyadi; Venkataraman, Satchi; Wong, Scott A.


    Structural optimization for damage tolerance under various unforeseen damage scenarios is computationally challenging. It couples non-linear progressive failure analysis with sampling based stochastic analysis of random damages. This work shows that analysis of damage tolerance depends on specifi......Structural optimization for damage tolerance under various unforeseen damage scenarios is computationally challenging. It couples non-linear progressive failure analysis with sampling based stochastic analysis of random damages. This work shows that analysis of damage tolerance depends...... on specification of damages, and optimizing a structure under one damage specification can be sensitive to other damages not considered. This work demonstrates the importance of understanding the underlying mechanics that provide damage tolerance in order to develop computationally efficient methods...

  1. Wire bond degradation under thermo- and pure mechanical loading

    DEFF Research Database (Denmark)

    Pedersen, Kristian Bonderup; Nielsen, Dennis Achton; Czerny, Bernhard


    This paper presents a fundamental study on degradation of heavy Al bond wires typically used in high power modules. Customized samples are designed to only consist of Al bond wires on standard Si diodes. These samples are subjected to pure mechanical and passive thermal cycling to investigate...... the bond degradation behavior on a simple system as well as compare these two test methods. Although an appreciable difference in fracture behavior is observed between these two methods, both provide correlation between the number of cycles and degree of degradation, especially in the case of the passive...... thermal test. To enable investigation of degradation rate a large number of bond interfaces is analyzed and they are found to follow conventional accepted fracture laws like Paris-Erdogan. With additional work this could enable the possibility of obtaining empirical parameters to be used in actual physics...

  2. Combined Effects of Sustained Loads and Wet-Dry Cycles on Durability of Glass Fiber Reinforced Polymer Composites

    Directory of Open Access Journals (Sweden)

    Mengting Li


    Full Text Available This paper deals with durability of glass fiber reinforced polymer (GFRP composites under the combined effects of sustained tensile loads and wet-dry (WD cycles. Two different solutions (distilled water and saltwater were used to imitate the freshwater and marine environments, respectively. Tensile properties of the unconditioned and conditioned specimens were measured to study the durability of GFRP composites under these 2 effects. The response indicated that both tensile strength and elastic modulus increased initially upon WD cycles, which was attributed to both the postcuring of resin and the sustained tensile stress allowing for fastec cure. Further exposure to WD cycles in distilled water or saltwater led to a steady decrease in tensile strength and modulus. WD cycles of saltwater and distilled water have similar effects on the degradation of the tensile properties for unstressed specimens. However, the elastic modulus and elongation at rupture of stressed specimens under WD cycles of saltwater decreased more than those specimens under WD cycles of distilled water. Moreover, increase of sustained loads led to a decrease in tensile strength. Based on Arrhenius method, a prediction model which accounted for the effects of postcure processes was developed. The predicted results of tensile strength and elastic modulus agree well with those obtained from the experiments.

  3. Vortex Domain Structure in Ferroelectric Nanoplatelets and Control of its Transformation by Mechanical Load (United States)

    Chen, W. J.; Zheng, Yue; Wang, Biao


    Vortex domain patterns in low-dimensional ferroelectrics and multiferroics have been extensively studied with the aim of developing nanoscale functional devices. However, control of the vortex domain structure has not been investigated systematically. Taking into account effects of inhomogeneous electromechanical fields, ambient temperature, surface and size, we demonstrate significant influence of mechanical load on the vortex domain structure in ferroelectric nanoplatelets. Our analysis shows that the size and number of dipole vortices can be controlled by mechanical load, and yields rich temperature-stress (T-S) phase diagrams. Simulations also reveal that transformations between “vortex states” induced by the mechanical load are possible, which is totally different from the conventional way controlled on the vortex domain by the electric field. These results are relevant to application of vortex domain structures in ferroelectric nanodevices, and suggest a novel route to applications including memories, mechanical sensors and transducers. PMID:23150769

  4. Effects of mechanical loading on human mesenchymal stem cells for cartilage tissue engineering. (United States)

    Choi, Jane Ru; Yong, Kar Wey; Choi, Jean Yu


    Today, articular cartilage damage is a major health problem, affecting people of all ages. The existing conventional articular cartilage repair techniques, such as autologous chondrocyte implantation (ACI), microfracture, and mosaicplasty, have many shortcomings which negatively affect their clinical outcomes. Therefore, it is essential to develop an alternative and efficient articular repair technique that can address those shortcomings. Cartilage tissue engineering, which aims to create a tissue-engineered cartilage derived from human mesenchymal stem cells (MSCs), shows great promise for improving articular cartilage defect therapy. However, the use of tissue-engineered cartilage for the clinical therapy of articular cartilage defect still remains challenging. Despite the importance of mechanical loading to create a functional cartilage has been well demonstrated, the specific type of mechanical loading and its optimal loading regime is still under investigation. This review summarizes the most recent advances in the effects of mechanical loading on human MSCs. First, the existing conventional articular repair techniques and their shortcomings are highlighted. The important parameters for the evaluation of the tissue-engineered cartilage, including chondrogenic and hypertrophic differentiation of human MSCs are briefly discussed. The influence of mechanical loading on human MSCs is subsequently reviewed and the possible mechanotransduction signaling is highlighted. The development of non-hypertrophic chondrogenesis in response to the changing mechanical microenvironment will aid in the establishment of a tissue-engineered cartilage for efficient articular cartilage repair. © 2017 Wiley Periodicals, Inc.


    Directory of Open Access Journals (Sweden)

    KIRALY Andrei


    Full Text Available Not a long time ago in “Eastern Economies”, especially in the mechanical design domain, words like costing or sustainability were practical neglected. Their importance is raising nowadays more and more and the author explains how it introduced them in mechanical engineers curriculum at the computer aided design discipline, because good habits must be implemented from young ages.

  6. Mechanism behind self-sustained oscillations in direct current glow discharges and in dusty plasmas

    CERN Document Server

    Cho, Sung Nae


    An alternative explanation to the mechanism behind self-sustained oscillations of ions in direct current (DC) glow discharges is provided. Such description is distinguished from the one provided by fluid models, where oscillations are attributed to positive feedback mechanism associated with photoionization of particles and photoemission of electrons from the cathode. Here, oscillations arise as consequence of interaction between an ion and surface charges induced by it at the bounding electrodes. Such mechanism provides an elegant explanation to why self-sustained oscillations occur only in the negative resistance region of the voltage-current characteristic curve in DC glow discharges. It is found that oscillation frequencies increase with ion's surface charge density, but at the rate which is significantly slower than it does with electric field. The presented mechanism also describes the self-sustained oscillations of ions in dusty plasmas, demonstrating that oscillations in dusty plasmas and DC glow disc...

  7. Butyrate-Loaded Chitosan/Hyaluronan Nanoparticles: A Suitable Tool for Sustained Inhibition of ROS Release by Activated Neutrophils

    DEFF Research Database (Denmark)

    Sacco, Pasquale; Decleva, Eva; Tentor, Fabio


    of neutrophil ROS production by free butyrate declines over time, that of butyrate-loaded chitosan/hyaluronan nanoparticles (B-NPs) is sustained. Additional valuable features of these nanoparticles are inherent ROS scavenger activity, resistance to cell internalization, and mucoadhesiveness. B-NPs appear...... that butyrate inhibits neutrophil ROS release in a dose and time-dependent fashion. Given the short half-life of butyrate, chitosan/hyaluronan nanoparticles are next designed and developed as controlled release carriers able to provide cells with a long-lasting supply of this SCFA. Notably, while the inhibition...

  8. Formulation of novel sustained release rifampicin-loaded solid lipid microparticles based on structured lipid matrices from Moringa oleifera. (United States)

    Onyishi, Ikechukwu V; Chime, Salome A; Ogudiegwu, Echezona O


    To formulate sustained release rifampicin-loaded solid lipid microparticles (SLMs) using structured lipid matrices based on Moringa oil (MO) and Phospholipon 90G (P90G). Rifampicin-loaded and unloaded SLMs were formulated by melt homogenization and characterized in terms of particle morphology and size, percentage drug content (PDC), pH stability, stability in simulated gastric fluid (SGF, pH 1.2), minimum inhibitory concentration (MIC) and in vitro release. In vivo release was studied in Wistar rats. Rifampicin-loaded SLMs had particle size range of 32.50 ± 2.10 to 34.0 ± 8.40 μm, highest PDC of 87.6% and showed stable pH. SLMs had good sustained release properties with about 77.1% release at 12 h in phosphate buffer (pH 6.8) and 80.3% drug release at 12 h in simulated intestinal fluid (SIF, pH 7.4). SLMs exhibited 48.51% degradation of rifampicin in SGF at 3 h, while rifampicin pure sample had 95.5% degradation. Formulations exhibited MIC range of 0.781 to 1.562, 31.25 to 62.5 and 6.25 to 12.5 μg/ml against Salmonella typhi, Escherichia coli, and Bacillus subtilis respectively and had higher in vivo absorption than the reference rifampicin (p < 0.05). Rifampicin-loaded SLMs could be used once daily for the treatment tuberculosis.

  9. Biological responses of three-dimensional cultured fibroblasts by sustained compressive loading include apoptosis and survival activity.

    Directory of Open Access Journals (Sweden)

    Toshiki Kanazawa

    Full Text Available Pressure ulcers are characterized by chronicity, which results in delayed wound healing due to pressure. Early intervention for preventing delayed healing due to pressure requires a prediction method. However, no study has reported the prediction of delayed healing due to pressure. Therefore, this study focused on biological response-based molecular markers for the establishment of an assessment technology to predict delayed healing due to pressure. We tested the hypothesis that sustained compressive loading applied to three dimensional cultured fibroblasts leads to upregulation of heat shock proteins (HSPs, CD44, hyaluronan synthase 2 (HAS2, and cyclooxygenase 2 (COX2 along with apoptosis via disruption of adhesion. First, sustained compressive loading was applied to fibroblast-seeded collagen sponges. Following this, collagen sponge samples and culture supernatants were collected for apoptosis and proliferation assays, gene expression analysis, immunocytochemistry, and quantification of secreted substances induced by upregulation of mRNA and protein level. Compared to the control, the compressed samples demonstrated that apoptosis was induced in a time- and load- dependent manner; vinculin and stress fiber were scarce; HSP90α, CD44, HAS2, and COX2 expression was upregulated; and the concentrations of HSP90α, hyaluronan (HA, and prostaglandin E2 (PGE2 were increased. In addition, the gene expression of antiapoptotic Bcl2 was significantly increased in the compressed samples compared to the control. These results suggest that compressive loading induces not only apoptosis but also survival activity. These observations support that HSP90α, HA, and, PGE2 could be potential molecular markers for prediction of delayed wound healing due to pressure.

  10. Compressive damage mechanism of GFRP composites under off-axis loading: Experimental and numerical investigations

    DEFF Research Database (Denmark)

    Zhou, H.W.; Li, H.Y.; Gui, L.L.


    Experimental and computational studies of the microscale mechanisms of damage formation and evolution in unidirectional glass fiber reinforced polymer composites (GFRP) under axial and off-axis compressive loading are carried out. A series of compressive testing of the composites with different....... With increasing the angle between the fiber and applied loading, failure of glass fibers is mainly controlled by shear cracking. For the computational analysis of the damage mechanisms, 3D multifiber unit cell models of GFRP composites and X-FEM approach to the fracture modeling were used. The computational...... angles between the loading vector and fiber direction were carried out under scanning electron microscopy (SEM) in situ observation. The damage mechanisms as well as stress strain curves were obtained in the experiments. It was shown that the compressive strength of composites drastically reduces when...

  11. Analytical Compliance Modeling of Serial Flexure-Based Compliant Mechanism Under Arbitrary Applied Load (United States)

    Wang, Li-Ping; Jiang, Yao; Li, Tie-Min


    Analytical compliance model is vital to the flexure- based compliant mechanism in its mechanical design and motion control. The matrix is a common and effective approach in the compliance modeling while it is not well developed for the closed-loop serial and parallel compliant mechanisms and is not applicable to the situation when the external loads are applied on the flexure members. Concise and explicit analytical compliance models of the serial flexure-based compliant mechanisms under arbitrary loads are derived by using the matrix method. An equivalent method is proposed to deal with the situation when the external loads are applied on the flexure members. The external loads are transformed to concentrated forces applied on the rigid links, which satisfy the equations of static equilibrium and also guarantee that the deformations at the displacement output point remain unchanged. Then the matrix method can be still adopted for the compliance analysis of the compliant mechanism. Finally, several specific examples and an experimental test are given to verify the effectiveness of the compliance models and the force equivalent method. The research enriches the matrix method and provides concise analytical compliance models for the serial compliant mechanism.

  12. Effect of surface loading on the hydro-mechanical response of a tunnel in saturated ground

    Directory of Open Access Journals (Sweden)

    Simon Heru Prassetyo


    Full Text Available The design of underground spaces in urban areas must account not only for the current overburden load but also for future surface loads, such as from construction of high-rise buildings above underground structures. In saturated ground, the surface load will generate an additional mechanical response through stress changes and ground displacement, as well as a hydraulic response through pore pressure changes. These hydro-mechanical (H-M changes can severely influence tunnel stability. This paper examines the effect of surface loading on the H-M response of a typical horseshoe-shaped tunnel in saturated ground. Two tunnel models were created in the computer code Fast Lagrangian Analysis of Continua (FLAC. One model represented weak and low permeability ground (stiff clay, and the other represented strong and high permeability ground (weathered granite. Each of the models was run under two liner permeabilities: permeable and impermeable. Two main cases were compared. In Case 1, the surface load was applied 10 years after tunnel construction. In Case 2, the surface load was applied after the steady state pore pressure condition was achieved. The simulation results show that tunnels with impermeable liners experienced the most severe influence from the surface loading, with high pore pressures, large inward displacement around the tunnels, and high bending moments in the liner. In addition, the severity of the response increased toward steady state. This induced H-M response was worse for tunnels in clay than for those in granite. Furthermore, the long-term liner stabilities in Case 1 and Case 2 were similar, indicating that the influence of the length of time between when the tunnel was completed and when the surface load was applied was negligible. These findings suggest that under surface loading, in addition to the ground strength, tunnel stability in saturated ground is largely influenced by liner permeability and the long-term H-M response of

  13. Principles of loads and failure mechanisms applications in maintenance, reliability and design

    CERN Document Server

    Tinga, T


    Failure of components or systems must be prevented by both designers and operators of systems, but knowledge of the underlying mechanisms is often lacking. Since the relation between the expected usage of a system and its failure behavior is unknown, unexpected failures often occur, with possibly serious financial and safety consequences. Principles of Loads and Failure Mechanisms.  Applications in Maintenance, Reliability and Design provides a complete overview of all relevant failure mechanisms, ranging from mechanical failures like fatigue and creep to corrosion and electric failures. Both qualitative and quantitative descriptions of the mechanisms and their governing loads enable a solid assessment of a system’s reliability in a given or assumed operational context. Moreover, a unique range of applications of this knowledge in the fields of maintenance, reliability and design are presented. The benefits of understanding the physics of failure are demonstrated for subjects like condition monitoring, pre...

  14. Mechanical Properties of Granular Materials and Their Impact on Load Distribution in Silo: A Review

    Directory of Open Access Journals (Sweden)

    Horabik J.


    Full Text Available Mechanical properties of granular materials and their impact on load distribution in storage silo were discussed with special focus on materials of biological origin. Granular materials classification was briefly outlined. The evolution of constitutive models of granular materials developed in the frame of mechanics of continuum was addressed. Analytical methods, Finite Element Methods (FEM, and Discrete Element Methods (DEM of estimation of silo pressure were discussed. Special attention was paid to the following issues: dynamic pressure switch in the first moment of silo discharge, asymmetry of loads due to eccentric discharge, and impact of uncontrolled increase of moisture content of grain on silo pressures.

  15. Failure mechanisms and behavior of ceramic matrix composites under transverse loading

    Energy Technology Data Exchange (ETDEWEB)

    Daniel, I.M. [Northwestern Univ., Evanston, IL (United States); Anastasopoulos, G.J. [European Center of Advanced Technologies, Athens (Greece)


    Transverse tensile loading of brittle matrix composites is the most severe type of loading because of the low tensile strength of the matrix material and the high stress concentration at the fiber matrix interface. Failure initiation in the form of short cracks usually takes place in the interphase region. The location and orientation of these cracks depend on the relative elastic and ultimate properties of the constituents, i.e., fiber, matrix and interphase, and on the fiber packing and volume ratio. Failure mechanisms under transverse tensile loading were observed under the microscope in real time. The first microcracks originated at the fiber-matrix interface and were nearly normal to it. When the fibers are closely packed, usually in a near hexagonal array, radial cracks initiate at approximately 45{degrees} from the loading axis. When fibers are further apart and are surrounded by a relatively large volume of matrix, radial cracks occur at approximately 90{degrees} from the loading axis. As the load increases isolated interface cracks develop and they eventually coalesce with the radial microcracks to form a catastrophic macrocrack. The effects of the various failure mechanisms on the stiffness and the overall stress-strain behavior were studied. The type and location of failure initiation was used in conjunction with an elastic analysis of a three-phase material and a maximum stress criterion for the matrix to determine the effective stiffness of the interphase.

  16. Resilience Despite Damage: Structure and Mechanics of Multicycle Loading in the Mussel Plaque (United States)

    Wilhelm, Menaka; Filippidi, Emmanouela; Waite, J. Herbert; Valentine, Megan

    The proteinaceous byssal plaque-thread structures created by marine mussels exhibit extraordinary load-bearing capability. Knoweldge of nanoscopic protein interactions that support interfacial adhesion in the plaque has improved in recent years, but supramolecular mechanisms of energy dissipation that confer toughness are less understood. We have used multicycle loading in the plaque-thread structure, complemented with scanning electron microscopy of strained plaques, to probe force response and strain-induced structural changes. We find that multicycle loading decreases small-strain stiffness, but does not compromise the critical strength or maximum extension, as compared to plaques that are monotonically loaded to failure. The strain-dependent plastic damage does not appear to be reversible or repairable on hours-long timescales, but this work suggests that a redundancy of load-bearing mechanisms contributes to plaque toughness in repeated loadings. Improved understanding of energy dissipation on lengthscales ranging from microns to millimeters provides new insight into the mussel system, and offers potential strategies for the design of soft, tough and resilient synthetic structures. This work was supported by the MRSEC Program of the National Science Foundation under Award No. DMR 1121053.

  17. Lidocaine/ketorolac-loaded biodegradable nanofibrous anti-adhesive membranes that offer sustained pain relief for surgical wounds. (United States)

    Kao, Ching-Wei; Lee, Demei; Wu, Min-Hsuan; Chen, Jan-Kan; He, Hong-Lin; Liu, Shih-Jung


    The aim of this study was to develop and evaluate the effectiveness of biodegradable nanofibrous lidocaine/ketorolac-loaded anti-adhesion membranes to sustainably release analgesics on abdominal surgical wounds. The analgesic-eluting membranes with two polymer-to-drug ratios (6:1 and 4:1) were produced via an electrospinning technique. A high-performance liquid chromatography (HPLC) assay was employed to characterize the in vivo and in vitro release behaviors of the pharmaceuticals from the membranes. It was found that all biodegradable anti-adhesion nanofibers released effective concentrations of lidocaine and ketorolac for over 20 days post surgery. In addition, a transverse laparotomy was setup in a rat model for an in vivo assessment of activity of postoperative recovery. No tissue adhesion was observed at 2 weeks post surgery, demonstrating the potential anti-adhesion capability of the drug-eluting nanofibrous membrane. The postoperative activities were recorded for two groups of rats as follows: rats that did not have any membrane implanted (group A) and rats that had the analgesic-eluting membrane implanted (group B). Rats in group B exhibited faster recovery times than those in group A with regard to postoperative activities, confirming the pain relief effectiveness of the lidocaine- and ketorolac-loaded nanofibrous membranes. The experimental results suggested that the anti-adhesion nanofibrous membranes with sustainable elution of lidocaine and ketorolac are adequately effective and durable for the purposes of postoperative pain relief in rats.

  18. Ad-hoc Network of Smart Sensors for Mechanical Load Measurement

    Directory of Open Access Journals (Sweden)

    Manuel A. Vieira


    Full Text Available Strain gauges load cells are transducers devices capable of converting changes in applied mechanical load into an electrical analog signal. Those devices have a large spectrum of applications ranging from domestic to industrial or even medical appliances just to name a few. In this work, they are used in the electronic instrumentation of a force platform that will be used to carry out the analysis and characterization of human biomechanical walking. In this platform, four load cells are installed, each one capable of measuring forces along two different axis. A total of eight strain-gauges per load cell are employed. Hence, analog signal transmission, besides requiring a large number of connection wires, is prone to interference and noise. Moreover, with this solution, scalability requires severe changes in the connection topology. In order to circumvent those problems, an alternative in-situ signal conditioning and digital data transmission system was devised. This approach, as far as investigated, presents an innovative solution to signal conditioning and data transmission for load-cells. In particular, the presented solution allows the creation of an ad-hoc network of load cells, using the I²C protocol with a master interface that allows the users to interact and change the parameters of each load cell. This instrumentation structure has been successfully tested and the obtained results are documented in this article.

  19. Effect of conditioner load on the polishing pad surface during chemical mechanical planarization process

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Cheol Min; Qin, Hong Yi; Hong, Seok Jun; Jeon, Sang Hyuk; Kulkarni, Atul; Kim, Tae Sun [Sungkyunkwan University, Suwon (Korea, Republic of)


    During the Chemical mechanical planarization (CMP), the pad conditioning process can affect the pad surface characteristics. Among many CMP process parameters, the improper applied load on the conditioner arm may have adverse effects on the polyurethane pad. In this work, we evaluated the pad surface properties under the various conditioner arm applied during pad conditioning process. The conditioning pads were evaluated for surface topography, surface roughness parameters such as Rt and Rvk and Material removal rate (MRR) and within-wafer non-uniformity after wafer polishing. We observed that, the pad asperities were collapsed in the direction of conditioner rotation and blocks the pad pores applied conditioner load. The Rvk value and MRR were founded to be in relation with 4 > 1 > 7 kgF conditioner load. Hence, this study shows that, 4 kgF applied load by conditioner is most suitable for the pad conditioning during CMP.

  20. Mechanical material behaviour in highly dynamic load conditions. Mechanisches Werkstoffverhalten unter hochdynamischen Belastungsbedingugen

    Energy Technology Data Exchange (ETDEWEB)

    Behler, F.J. (Fraunhofer-Inst., IFAM, Bremen (Germany))


    The numerical simulation of complex component stresses and structure deformations make it possible to estimate or describe the component behaviour during the design phase in many cases. The quality of the simulation calculation is determined by the possibility of access to suitably well-designed material databanks. Characterisation of the material in nearly realistic load conditions forms the basis of every databank of this kind. Numerical simulation, characterisation of the material and component behaviour supplement one another in the description and interpretation of deformation processes in partly extreme external load conditions. The load conditions have a direct effect on the mechanical material behaviour. The effect of the speed of stressing on the deformation and strength behaviour was shown from two examples from differed groups of materials (deep drawn sheet St 14 and CFK). It is true for both examined materials that they reach higher strengths under high dynamic loads, without any sacrifice of the deformation ability. (orig.).

  1. Effect of Cyclic Thermo-Mechanical Loads on Fatigue Reliability in Polymer Matrix Composites (United States)

    Shah, A. R.; Murthy, P. L. N.; Chamis, C. C.


    A methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects caused by long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multi-factor interaction relationship developed at NASA Lewis Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability- based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/- 45/90)(sub s) graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.

  2. Load regulates bone formation and Sclerostin expression through a TGFβ-dependent mechanism.

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    Jacqueline Nguyen

    Full Text Available Bone continually adapts to meet changing physical and biological demands. Osteoblasts, osteoclasts, and osteocytes cooperate to integrate these physical and biochemical cues to maintain bone homeostasis. Although TGFβ acts on all three of these cell types to maintain bone homeostasis, the extent to which it participates in the adaptation of bone to mechanical load is unknown. Here, we investigated the role of the TGFβ pathway in load-induced bone formation and the regulation of Sclerostin, a mechanosensitive antagonist of bone anabolism. We found that mechanical load rapidly represses the net activity of the TGFβ pathway in osteocytes, resulting in reduced phosphorylation and activity of key downstream effectors, Smad2 and Smad3. Loss of TGFβ sensitivity compromises the anabolic response of bone to mechanical load, demonstrating that the mechanosensitive regulation of TGFβ signaling is essential for load-induced bone formation. Furthermore, sensitivity to TGFβ is required for the mechanosensitive regulation of Sclerostin, which is induced by TGFβ in a Smad3-dependent manner. Together, our results show that physical cues maintain bone homeostasis through the TGFβ pathway to regulate Sclerostin expression and the deposition of new bone.

  3. Cracks path growth in turbine blades with TBC under thermo – mechanical cyclic loadings

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    T. Sadowski


    Full Text Available Blades of combustion turbines are extremely loaded turbojet elements, which transmit operative energy onto a rotor. Experiences of many years indicate, that cracks initiation and propagation in the blades during the operation time can cause destruction not only of the engine, but sometimes an airplane. In high temperature one of the most often occuring interactions in the turbine engine are time variable force fields, caused by non-stationary flowing of an exhaust gas and aerodynamical interaction of the engine elements. The extremal thermo-mechanical loadings initiate gradual degradation process of the blades as a result of fatigue and material creep. More often Thermal Barrier Coatings (TBCs are applied on the turbine blade surface to provide protection not only against the high temperature but also against aggressive environment. The paper presents the advantages of applying of the TBC layers for increase of the cracks resistance to gradual degradation of the turbine blades. The level of save values of thermo-mechanical loading was estimated. Analysis of critical values of loading leading to crack initiation, further growth and the final blade fragmentation was performed. The most efforted places of the turbine blades were selected and crack paths due to thermo-mechanical cyclic loading were determined.

  4. Mechanical effect of static loading on endodontically treated teeth restored with fiber-reinforced posts. (United States)

    Chieruzzi, Manila; Rallini, Marco; Pagano, Stefano; Eramo, Stefano; D'Errico, Potito; Torre, Luigi; Kenny, José M


    The aim of this study was to investigate the mechanical behavior of a dental system built up with fiber-reinforced composite (FRC) endodontic posts with different types of fibers and two cements (the first one used with a primer, the second one without it). Six FRC posts were used. Each system was characterized in terms of structural efficiency under external applied loads similar to masticatory forces. An oblique force was applied and stiffness and maximum load data were obtained. The same test was used for the dentine. The systems were analyzed by scanning electron microscope (SEM) to investigate the surface of the post and inner surface of root canal after failure. The mechanical tests showed that load values in dental systems depend on the post material and used cement. The highest load (281 ± 59 N) was observed for the conical glass fiber posts in the cement without primer. There was a 50 and 85% increase in the maximum load for two of the conical posts with glass fibers and a 229% increase for the carbon fiber posts in the cement without primer as compared with the cement with primer. Moreover, almost all the studied systems showed fracture resistances higher than the typical masticatory loads. The microscopic analysis underlined the good adhesion of the second cement at the interfaces between dentine and post. The mechanical tests confirmed that the strength of the dental systems subjected to masticatory loads was strictly related to the bond at the interface post/cement and cement/dentine. Copyright © 2013 Wiley Periodicals, Inc.

  5. Inner-Learning Mechanism Based Control Scheme for Manipulator with Multitasking and Changing Load

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    Fangzheng Xue


    Full Text Available With the rapid development of robot technology and its application, manipulators may face complex tasks and dynamic environments in the coming future, which leads to two challenges of control: multitasking and changing load. In this paper, a novel multicontroller strategy is presented to meet such challenges. The presented controller is composed of three parts: subcontrollers, inner-learning mechanism, and switching rules. Each subcontroller is designed with self-learning skills to fit the changing load under a special task. When a new task comes, switching rule reselects the most suitable subcontroller as the working controller to handle current task instead of the older one. Inner-learning mechanism makes the subcontrollers learn from the working controller when load changes so that the switching action causes smaller tracking error than the traditional switch controller. The results of the simulation experiments on two-degree manipulator show the proposed method effect.

  6. Mechanics of load-drag-unload contact cleaning of gecko-inspired fibrillar adhesives. (United States)

    Abusomwan, Uyiosa A; Sitti, Metin


    Contact self-cleaning of gecko-inspired synthetic adhesives with mushroom-shaped tips has been demonstrated recently using load-drag-unload cleaning procedures similar to that of the natural animal. However, the underlying mechanics of contact cleaning has yet to be fully understood. In this work, we present a detailed experiment of contact self-cleaning that shows that rolling is the dominant mechanism of cleaning for spherical microparticle contaminants, during the load-drag-unload procedure. We also study the effect of dragging rate and normal load on the particle rolling friction. A model of spherical particle rolling on an elastomer fibrillar adhesive interface is developed and agrees well with the experimental results. This study takes us closer to determining design parameters for achieving self-cleaning fibrillar adhesives.

  7. Validation of an instrumented dummy to assess mechanical aspects of discomfort during load carriage.

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    Patrick D Wettenschwiler

    Full Text Available Due to the increasing load in backpacks and other load carriage systems over the last decades, load carriage system designs have to be adapted accordingly to minimize discomfort and to reduce the risk of injury. As subject studies are labor-intensive and include further challenges such as intra-subject and inter-subject variability, we aimed to validate an instrumented dummy as an objective laboratory tool to assess the mechanical aspects of discomfort. The validation of the instrumented dummy was conducted by comparison with a recent subject study. The mechanical parameters that characterize the static and dynamic interaction between backpack and body during different backpack settings were compared. The second aim was to investigate whether high predictive power (coefficient of determination R2>0.5 in assessing the discomfort of load carriage systems could be reached using the instrumented dummy. Measurements were conducted under static conditions, simulating upright standing, and dynamic conditions, simulating level walking. Twelve different configurations of a typical load carriage system, a commercially available backpack with a hip belt, were assessed. The mechanical parameters were measured in the shoulder and the hip region of the dummy and consisted of average pressure, peak pressure, strap force and relative motion between the system and the body. The twelve configurations consisted of three different weights (15kg, 20kg, and 25kg, combined with four different hip belt tensions (30N, 60N, 90N, and 120N. Through the significant (p<0.05 correlation of the mechanical parameters measured on the dummy with the corresponding values of the subject study, the dummy was validated for all static measurements and for dynamic measurements in the hip region to accurately simulate the interaction between the human body and the load carriage system. Multiple linear regressions with the mechanical parameters measured on the dummy as independent

  8. The contribution of experimental in vivo models to understanding the mechanisms of adaptation to mechanical loading in bone

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    Lee B Meakin


    Full Text Available Changing loading regimens by natural means such as exercise, with or without interference such as osteotomy, has provided useful information on the structure:function relationship in bone tissue. However, the greatest precision in defining those aspects of the overall strain environment that influence modeling and remodeling behavior has been achieved by relating quantified changes in bone architecture to quantified changes in bones’ strain environment produced by direct, controlled artificial bone loading.Jiri Heřt introduced the technique of artificial loading of bones in vivo with external devices in the 1960s using an electromechanical device to load rabbit tibiae through transfixing stainless steel pins. Quantifying natural bone strains during locomotion by attaching electrical resistance strain gauges to bone surfaces was introduced by Lanyon, also in the 1960s. These studies in a variety of bones in a number of species demonstrated remarkable uniformity in the peak strains and maximum strain rates experienced.Experiments combining strain gauge instrumentation with artificial loading in sheep, pigs, roosters, turkeys, rats and mice has yielded significant insight into the control of strain-related adaptive (remodeling. This diversity of approach has been largely superseded by non-invasive transcutaneous loading in rats and mice which is now the model of choice for many studies. Together such studies have demonstrated that; over the physiological strain range, bone’s mechanically-adaptive processes are responsive to dynamic but not static strains; the size and nature of the adaptive response controlling bone mass is linearly related to the peak loads encountered; the strain-related response is preferentially sensitive to high strain rates and unresponsive to static ones; is most responsive to unusual strain distributions; is maximized by remarkably few strain cycles and that these are most effective when interrupted by short periods of

  9. Failure mechanisms of closed-cell aluminum foam under monotonic and cyclic loading

    NARCIS (Netherlands)

    Amsterdam, E.; De Hosson, J. Th. M.; Onck, P. R.


    This paper concentrates on the differences in failure mechanisms of Alporas closed-cell aluminum foam under either monotonic or cyclic loading. The emphasis lies on aspects of crack nucleation and crack propagation in relation to the microstructure. The cell wall material consists of Al dendrites

  10. Temporal effects of mechanical loading on deformation-induced damage in skeletal muscle tissue

    NARCIS (Netherlands)

    Loerakker, S.; Stekelenburg, A.; Strijkers, G. J.; Rijpkema, J. J. M.; Baaijens, F. P. T.; Bader, D. L.; Nicolay, K.; Oomens, C. W. J.


    Mechanical loading of soft tissues covering bony prominences can cause skeletal muscle damage, ultimately resulting in a severe pressure ulcer termed deep tissue injury. Recently, by means of an experimental-numerical approach, it was shown that local tissue deformations cause tissue damage once a

  11. The influence of ergonomic devices on mechanical load during patient handling activities in nursing homes

    NARCIS (Netherlands)

    H.J.J. Knibbe; Drs. H.S. Miedema; A. Burdorf; E. Koppelaar


    OBJECTIVES: Mechanical load during patient handling activities is an important risk factor for low back pain among nursing personnel. The aims of this study were to describe required and actual use of ergonomic devices during patient handling activities and to assess the influence of these ergonomic

  12. Residual stress in a M3:2 PM high speed steel; effect of mechanical loading

    DEFF Research Database (Denmark)

    Højerslev, Christian; Odén, Magnus; Carstensen, Jesper V.


    X-ray lattice strains were investigated in an AISI M3:2 PM high-speed steel in the as heat treated condition and after exposure to alternating mechanical load. The volume changes during heat treatment were monitored with dilatometry. Hardened and tempered AISI M3:2 steel consists of tempered lath...

  13. Microtrauma stimulates rat Achilles tendon healing via an early gene expression pattern similar to mechanical loading

    DEFF Research Database (Denmark)

    Hammerman, Malin; Aspenberg, Per; Eliasson, Pernilla


    rats received Botox into the calf muscle to reduce loading, and the Achilles tendon was transected. Ten rats were randomized to needling days 2-5. Mechanical testing on day 8 showed increased strength by 45% in the needling group. Next, another 24 rats were similarly unloaded, and 16 randomized...

  14. Assessing Cognitive Load Theory to Improve Student Learning for Mechanical Engineers (United States)

    Impelluso, Thomas J.


    A computer programming class for students of mechanical engineering was redesigned and assessed: Cognitive Load Theory was used to redesign the content; online technologies were used to redesign the delivery. Student learning improved and the dropout rate was reduced. This article reports on both attitudinal and objective assessment: comparing…

  15. Acute neuromuscular response during eccentric overload protocol by using a mechanical device to increase the load

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    Marcel B Lanza


    Full Text Available DOI:   The aim of this study was to propose a mechanical device that could increase the mechanical load during the entire eccentric (ECC action on a knee flexor machine and to compare the muscular activity when the device was used during a testing protocol. Fifteen physically active women were recruited, and they performed two protocols: control and eccentric overload. Control protocol was performed with concentric (CON and ECC actions with similar load (60% of one repetition maximum whilst eccentric overload protocol consisted of ECC actions with 40% more load than CON actions. Muscular activation was measured using surface electromyography of the biceps femoris (BF and the gastrocnemius medialis (GM muscles. ECC actions presented a higher muscular activation during eccentric overload protocol than control protocol for BF (p = 0.032, but not for the GM (p = 0.439. The mechanical device increased the mechanical load during the ECC muscle action and consequently increased the amplitude of the neural drive to the BF muscle; however, it did not increase the amplitude of the neural drive to the GM muscle.

  16. Expression of muscle anabolic and metabolic factors in mechanically loaded MLO-Y4 osteocytes. (United States)

    Juffer, Petra; Jaspers, Richard T; Lips, Paul; Bakker, Astrid D; Klein-Nulend, Jenneke


    Lack of physical activity results in muscle atrophy and bone loss, which can be counteracted by mechanical loading. Similar molecular signaling pathways are involved in the adaptation of muscle and bone mass to mechanical loading. Whether anabolic and metabolic factors regulating muscle mass, i.e., insulin-like growth factor-I isoforms (IGF-I Ea), mechano growth factor (MGF), myostatin, vascular endothelial growth factor (VEGF), or hepatocyte growth factor (HGF), are also produced by osteocytes in bone in response to mechanical loading is largely unknown. Therefore, we investigated whether mechanical loading by pulsating fluid flow (PFF) modulates the mRNA and/or protein levels of muscle anabolic and metabolic factors in MLO-Y4 osteocytes. Unloaded MLO-Y4 osteocytes expressed mRNA of VEGF, HGF, IGF-I Ea, and MGF, but not myostatin. PFF increased mRNA levels of IGF-I Ea (2.1-fold) and MGF (2.0-fold) at a peak shear stress rate of 44Pa/s, but not at 22Pa/s. PFF at 22 Pa/s increased VEGF mRNA levels (1.8- to 2.5-fold) and VEGF protein release (2.0- to 2.9-fold). Inhibition of nitric oxide production decreased (2.0-fold) PFF-induced VEGF protein release. PFF at 22 Pa/s decreased HGF mRNA levels (1.5-fold) but increased HGF protein release (2.3-fold). PFF-induced HGF protein release was nitric oxide dependent. Our data show that mechanically loaded MLO-Y4 osteocytes differentially express anabolic and metabolic factors involved in the adaptive response of muscle to mechanical loading (i.e., IGF-I Ea, MGF, VEGF, and HGF). Similarly to muscle fibers, mechanical loading enhanced expression levels of these growth factors in MLO-Y4 osteocytes. Although in MLO-Y4 osteocytes expression levels of IGF-I Ea and MGF of myostatin were very low or absent, it is known that the activity of osteoblasts and osteoclasts is strongly affected by them. The abundant expression levels of these factors in muscle cells, in combination with low expression in MLO-Y4 osteocytes, provide a

  17. Control mechanisms in the third-generation planning. Case study: Control to realize sustainable cities (United States)

    Wicaksono, A. D.


    Since the last few years, Indonesia has experienced important events that bring significant changes to the social, political and economic life. The changes directly or indirectly impact the field of planning. With the challenging condition which grows fast and is more complex ahead, and the greater demands on the role of planning, it is required that planning should have higher quality. This paper seeks to answer some questions as follows: (i) How are changes in paradigm and also the development of planning model for the current transition era?, (ii) What is the best way to improve the quality of planning control on the last generation planning model to realize sustainable city?. Analysis steps that will be used to achieve the paper objectives are: (i) Review of planning and sustainable cities theory, (ii) Pattern recognition, (iii) Identifying control mechanisms and sustainable urban forms, (iv) conceptualization. Based on discussion about sustainable cities and control mechanism, some conclusions can be generated as follows: (i) The third generation planning model is based on the theory of expanded system, emphasizing on the constraint of capacity and the ability of planners within the context of larger environment, (ii) There are various theoretical studies that recommend prescriptive model or solution for sustainable urban form and structure. The concepts of Sustainable Cities can be grouped in Neotraditional Development, Urban Containment, Compact City and The Eco-City. The four models above have criteria, namely (i) high density; (ii) a high level of diversity; (iii) mixed land use; (iv) compactness; (5) sustainable transport; (6) passive solar design; (7) Greening Ecological Design. The three main activities in control mechanisms are: Monitoring and Recommendation; a comparative review of the facts (conditions that exist or are developing) with the purpose (expected conditions, set out in urban planning) and recommendations; Evaluation, a review on the

  18. Mechanical loading prevents the stimulating effect of IL-1{beta} on osteocyte-modulated osteoclastogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, Rishikesh N.; Bakker, Astrid D.; Everts, Vincent [Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, Research Institute MOVE, Amsterdam (Netherlands); Klein-Nulend, Jenneke, E-mail: [Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, Research Institute MOVE, Amsterdam (Netherlands)


    Highlights: Black-Right-Pointing-Pointer Osteocyte incubation with IL-1{beta} stimulated osteocyte-modulated osteoclastogenesis. Black-Right-Pointing-Pointer Conditioned medium from IL-1{beta}-treated osteocytes increased osteoclastogenesis. Black-Right-Pointing-Pointer IL-1{beta} upregulated RANKL and downregulated OPG gene expression by osteocytes. Black-Right-Pointing-Pointer CYR61 is upregulated in mechanically stimulated osteocytes. Black-Right-Pointing-Pointer Mechanical loading of osteocytes may abolish IL-1{beta}-induced osteoclastogenesis. -- Abstract: Inflammatory diseases such as rheumatoid arthritis are often accompanied by higher plasma and synovial fluid levels of interleukin-1{beta} (IL-1{beta}), and by increased bone resorption. Since osteocytes are known to regulate bone resorption in response to changes in mechanical stimuli, we investigated whether IL-1{beta} affects osteocyte-modulated osteoclastogenesis in the presence or absence of mechanical loading of osteocytes. MLO-Y4 osteocytes were pre-incubated with IL-1{beta} (0.1-1 ng/ml) for 24 h. Cells were either or not subjected to mechanical loading by 1 h pulsating fluid flow (PFF; 0.7 {+-} 0.3 Pa, 5 Hz) in the presence of IL-1{beta} (0.1-1 ng/ml). Conditioned medium was collected after 1 h PFF or static cultures. Subsequently mouse bone marrow cells were seeded on top of the IL-1{beta}-treated osteocytes to determine osteoclastogenesis. Conditioned medium from mechanically loaded or static IL-1{beta}-treated osteocytes was added to co-cultures of untreated osteocytes and mouse bone marrow cells. Gene expression of cysteine-rich protein 61 (CYR61/CCN1), receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) by osteocytes was determined immediately after PFF. Incubation of osteocytes with IL-1{beta}, as well as conditioned medium from static IL-1{beta}-treated osteocytes increased the formation of osteoclasts. However, conditioned medium from mechanically loaded IL

  19. Green Concrete from Sustainable Recycled Coarse Aggregates: Mechanical and Durability Properties


    Neeraj Jain; Mridul Garg; A. K. Minocha


    Present investigations deal with the development of green concrete (M 30 grade) using recycled coarse aggregates for sustainable development. Characterization of recycled coarse aggregates showed that physical and mechanical properties are of inferior quality and improvement in properties was observed after washing due to removal of old weak mortar adhered on its surface. The influence of natural coarse aggregates replacement (50 and 100%) with recycled coarse aggregate on various mechanical ...

  20. McKenzie treatment versus mulligan sustained natural apophyseal glides for chronic mechanical low back pain


    Waqqar, Saira; Shakil-ur-Rehman, Syed; Ahmad, Shakeel


    Background and Objective: Chronic mechanical low back pain is common among different age groups and genders. Different manual therapy techniques combined with exercise therapy and electrotherapy modalities play an important role in its management. Our objective was to compare the effects of McKenzie extension exercisesprogram (EEP) versus Mulligan Sustained Natural Apophyseal Glides (SNAGs) for chronic mechanical low back pain (CMLBP). Methods: This randomized control trial (RCT) was conducte...

  1. Development of lovastatin-loaded poly(lactic acid microspheres for sustained oral delivery: in vitro and ex vivo evaluation

    Directory of Open Access Journals (Sweden)

    Guan QG


    Full Text Available Qigang Guan,1 Wei Chen,2 Xianming Hu2 1Department of Cardiology, The First Affiliated Hospital of China Medical University, Shenyang, People’s Republic of China; 2Department of Pharmaceutical, Shenyang Institute of Pharmaceutical Industry, Shenyang, People’s Republic of China Background: A novel lovastatin (LVT-loaded poly(lactic acid microsphere suitable for oral administration was developed in this study, and in vitro and in vivo characteristics were evaluated. Methods: The designed microspheres were obtained by an improved emulsion-solvent evaporation method. The morphological examination, particle size, encapsulation ratio, drug loading, and in vitro release were characterized. Pharmacokinetics studies were used to show that microspheres possess more advantages than the conventional formulations. Results: By using the emulsion-solvent evaporation method, it was simple to prepare microspheres and easy to scale up production. The morphology of formed microspheres showed a spherical shape with a smooth surface, without any particle aggregation. Mean size of the microspheres was 2.65±0.69 µm; the encapsulation efficiency was 92.5%±3.6%, and drug loading was 16.7%±2.1%. In vitro release indicated that the LVT microspheres had a well-sustained release efficacy, and ex vivo studies showed that after LVT was loaded to microspheres, the area under the plasma concentration-time curve from zero to the last measurable plasma concentration point and the extrapolation to time infinity increased significantly, which represented 2.63-fold and 2.49-fold increases, respectively, compared to suspensions. The rate of ex vivo clearance was significantly reduced. Conclusion: This research proved that poly(lactic acid microspheres can significantly prolong the drug circulation time in vivo and can also significantly increase the relative bioavailability of the drug. Keywords: lovastatin, microspheres, PLA, in vitro release, pharmacokinetics 

  2. Dielectric elastomer generator with equi-biaxial mechanical loading for energy harvesting (United States)

    Huang, Jiangshui; Shian, Samuel; Suo, Zhigang; Clarke, David R.


    Dielectric elastomer generators (DEGs) are attractive candidates for harvesting electrical energy from mechanical work since they comprise relatively few moving parts and large elastomer sheets can be mass produced. Successfully demonstrations of the DEG prototypes have been reported from a diverse of energy sources, including ocean waves, wind, flowing water and human movement. The energy densities achieved, however, are still small compared with theoretical predictions. We show that significant improvements in energy density (550 J/kg with an efficiency of 22.1%), can be achieved using an equi-biaxial mechanical loading configuration, one that produces uniform deformation and maximizes the capacitance changes. Analysis of the energy dissipations indicates that mechanical losses, which are caused by the viscous losses both within the acrylic elastomer and within the thread materials used for the load transfer assembly, limits the energy conversion efficiency of the DEG. Addressing these losses is suggested to increase the energy conversion efficiency of the DEG.

  3. Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

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    Jie Chen


    Full Text Available Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in coke drums in the form of bulging and cracking. There were some studies on the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully developed to allow performing thermal-mechanical fatigue (TMF test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

  4. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, N.; Silverman, T. J.; Wohlgemuth, J.; Kurtz, S.; Inoue, M.; Sakurai, K.; Shinoda, T.; Zenkoh, H.; Hirota, K.; Miyashita, M.; Tadanori, T.; Suzuki, S.


    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours o testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  5. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Bosco, Nick; Silverman, Timothy J.; Wohlgemuth, John; Kurtz, Sarah; Inoue, Masanao; Sakurai, Keiichiro; Shioda, Tsuyoshi; Zenkoh, Hirofumi; Hirota, Kusato; Miyashita, Masanori; Tadanori, Tanahashi; Suzuki, Soh; Chen, Yifeng; Verlinden, Pierre J.


    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours of testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  6. An Innovative Design of a Microtab Deployment Mechanism for Active Aerodynamic Load Control

    Directory of Open Access Journals (Sweden)

    Kuo-Chang Tsai


    Full Text Available This study presents an innovative design of a microtab system for aerodynamic load control on horizontal-axis wind-turbine rotors. Microtabs are small devices located near the trailing edge of the rotor blades and enable a rapid increase or decrease of the lift force through deployment of the tabs on the pressure or suction side of the airfoil, respectively. The new system has been designed to replace an earlier linearly-actuated microtab mechanism whose performance was limited by space restrictions and stiction. The newly-designed microtab system is based on a four-bar linkage that overcomes the two drawbacks. Its improved kinematics allows for the tab height to increase from 1.0% to 1.7% of the airfoil chord when fully deployed, thereby making it more effective in terms of aerodynamic load control. Furthermore, the modified four-bar link mechanism provides a more robust and reliable mechanical structure.

  7. Improving Log Loading Efficiency for Improved Sustainable Transport within the Irish Forest and Biomass Sectors

    Directory of Open Access Journals (Sweden)

    Amanda Sosa


    Full Text Available In Ireland, timber and biomass haulage faces the challenge of transporting enough material within strict legal dimensions and gross vehicle weights restrictions for trucks and trailers. The objective of this study was to develop a method to control payload weight by knowing the moisture content of the wood. Weights, volumes, and moisture content were gathered from 100 truckloads of Sitka spruce pulpwood. Truck volume and weight utilization patterns were analyzed based on stacked volume, truck volume, and weights recorded from the weighbridge. Solid/bulk volume conversion factors for the truckloads were estimated indicating the truck’s solid volume capacity to be filled. Trucks were grouped into five conditions based on their configuration—volume capacity and legal maximum payload. A loaded volume fraction was estimated to assess the optimal volume capacity and stanchion height at which the trucks should be loaded. Results showed that 100% of the trucks presented volume underutilization, with a maximum of 27.5 m3 (only 39.85% volume capacity. In contrast, 67% of trucks were overweight while the remaining 33% were under the legal maximum weight. The average solid/bulk volume conversion factor was 0.66 ± 0.013 at 95% confidence level. Depending on the conditions, trucks can be filled to 100% of their volume capacity with wood at an MC from 29% to 55%. The minimum truck volume capacity utilization was 45%. This methodology can be used by truck hauliers, enabling them to determine in-forest the optimum volume and weight of wood to be transported by knowing the moisture content (MC, the wood specie, and using the height of the stanchions of the trailer as reference when loading the truck.

  8. The Role of Adaptation in Body Load-Regulating Mechanisms During Locomotion (United States)

    Ruttley, Tara; Holt, Christopher; Mulavara, Ajitkumar; Bloomberg, Jacob


    Body loading is a fundamental parameter that modulates motor output during locomotion, and is especially important for controlling the generation of stepping patterns, dynamic balance, and termination of locomotion. Load receptors that regulate and control posture and stance in locomotion include the Golgi tendon organs and muscle spindles at the hip, knee, and ankle joints, and the Ruffini endings and the Pacinian corpuscles in the soles of the feet. Increased body weight support (BWS) during locomotion results in an immediate reorganization of locomotor control, such as a reduction in stance and double support duration and decreased hip, ankle, and knee angles during the gait cycle. Previous studies on the effect during exposure to increased BWS while walking showed a reduction in lower limb joint angles and gait cycle timing that represents a reorganization of locomotor control. Until now, no studies have investigated how locomotor control responds after a period of exposure to adaptive modification in the body load sensing system. The goal of this research was to determine the adaptive properties of body load-regulating mechanisms in locomotor control during locomotion. We hypothesized that body load-regulating mechanisms contribute to locomotor control, and adaptive changes in these load-regulating mechanisms require reorganization to maintain forward locomotion. Head-torso coordination, lower limb movement patterns, and gait cycle timing were evaluated before and after a 30-minute adaptation session during which subjects walked on a treadmill at 5.4 km/hr with 40% body weight support (BWS). Before and after the adaptation period, head-torso and lower limb 3D kinematic data were obtained while performing a goal directed task during locomotion with 0% BWS using a video-based motion analysis system, and gait cycle timing parameters were collected by foot switches positioned under the heel and toe of the subjects shoes. Subjects showed adaptive modification in

  9. CISM course on mechanical behaviour of soils under environmentally induced cyclic loads

    CERN Document Server

    Wood, David; Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads


    The book gives a comprehensive description of the mechanical response of soils (granular and cohesive materials) under cyclic loading. It provides the geotechnical engineer with the theoretical and analytical tools necessary for the evaluation of settlements developng with time under cyclic, einvironmentally idncued loads (such as wave motion, wind actions, water table level variation) and their consequences for the serviceability and durability of structures such as the shallow or deep foundations used in offshore engineering, caisson beakwaters, ballast and airport pavements and also to interpret monitoring data, obtained from both natural and artificial slopes and earth embankments, for the purposes of risk assessment and mitigation.

  10. Sustaining mechanism of small-scale turbulent eddies in a precessing sphere (United States)

    Horimoto, Yasufumi; Goto, Susumu


    It has been known for a long time that fully developed turbulence is sustained in a precessing container. The aim of the present study is to reveal the sustaining mechanism of turbulence in a precessing sphere by means of laboratory experiments. We conduct experiments using a Newtonian fluid (water) and viscoelastic fluids (dilute solutions of surfactant, cetyltrimethyl ammonium chloride, and polymers, polyethylene oxide) to understand the sustaining mechanism of turbulence of Newtonian fluids by examining turbulence modifications due to the surfactant and polymer additives. When the Reynolds number based on the spin angular velocity and radius of the sphere is fixed, the most developed turbulence is sustained with the Poincaré number (the precession rate) being about 0.1. The key ingredient of the developed turbulence is a pair of large-scale vortex tubes which robustly exists in the flow. Assuming that these vortex tubes sustain small-scale turbulent eddies through an energy cascading process, we can explain all our experimental observations. Concerning the turbulence modification by the additives, the time-scale criteria by Lumley [J. Polymer Sci.: Macromol. Rev. 7, 263 (1973), 10.1002/pol.1973.230070104] and the refined theory by Tabor and de Gennes [Europhys. Lett. 2, 519 (1986), 10.1209/0295-5075/2/7/005] explain the experimental result that the pair of large-scale vortex tubes survives even when small-scale turbulent eddies are drastically suppressed by the surfactant additive.

  11. Memory-induced mechanism for self-sustaining activity in networks (United States)

    Allahverdyan, A. E.; Steeg, G. Ver; Galstyan, A.


    We study a mechanism of activity sustaining on networks inspired by a well-known model of neuronal dynamics. Our primary focus is the emergence of self-sustaining collective activity patterns, where no single node can stay active by itself, but the activity provided initially is sustained within the collective of interacting agents. In contrast to existing models of self-sustaining activity that are caused by (long) loops present in the network, here we focus on treelike structures and examine activation mechanisms that are due to temporal memory of the nodes. This approach is motivated by applications in social media, where long network loops are rare or absent. Our results suggest that under a weak behavioral noise, the nodes robustly split into several clusters, with partial synchronization of nodes within each cluster. We also study the randomly weighted version of the models where the nodes are allowed to change their connection strength (this can model attention redistribution) and show that it does facilitate the self-sustained activity.

  12. Stiffness-Controlled Thermoresponsive Hydrogels for Cell Harvesting with Sustained Mechanical Memory. (United States)

    Fan, Xingliang; Zhu, Lu; Wang, Ke; Wang, Bingjie; Wu, Yaozu; Xie, Wei; Huang, Chengyu; Chan, Barbara Pui; Du, Yanan


    Most mechanobiological investigations focused on in situ mechanical regulation of cells on stiffness-controlled substrates with few downstream applications, as it is still challenging to harvest and expand mechanically primed cells by enzymatic digestion (e.g., trypsin) without interrupting cellular mechanical memory between passages. This study develops thermoresponsive hydrogels with controllable stiffness to generate mechanically primed cells with intact mechanical memory for augmented wound healing. No significant cellular property alteration of the fibroblasts primed on thermoresponsive hydrogels with varied stiffness has been observed through thermoresponsive harvesting. When reseeding the harvested cells for further evaluation, softer hydrogels are proven to better sustain the mechanical priming effects compared to rigid tissue culture plate, which indicates that both the stiffness-controlled substrate and thermoresponsive harvesting are required to sustain cellular mechanical memory between passages. Moreover, epigenetics analysis reveals that thermoresponsive harvesting could reduce the rearrangement and loss of chromatin proteins compared to that of trypsinization. In vivo wound healing using mechanically primed fibroblasts shows featured epithelium and sebaceous glands, which indicates augmented skin recovery compared with trypsinized fibroblasts. Thus, the thermoresponsive hydrogel-based cell harvesting system offers a powerful tool to investigate mechanobiology between cell passages and produces abundant cells with tailored mechanical priming properties for cell-based applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Effect of the mechanical properties and mode loading on the mechanical behaviour of weldment: a numerical analysis

    Directory of Open Access Journals (Sweden)

    Meddah Hadj Miloud


    Full Text Available Welding is used to realize permanent assembly in mechanical structures to assure the continuity of the parts to be assembled contrary to the other assembly techniques which have physical or chemical discontinuities. Generally, crack evolution depends on several intrinsic and extrinsic parameters of material. The aim of this work is to analyse the severity of crack defects on the mechanical behaviour of Welded joints. The cracks are considered located in the weld metal. The J-integral method was used to analyse the fracture behaviour of these structures by the two-dimensional finite element method using Cast3M code. The effect of the mechanical properties, the mismatching and the crack size on the J-integral values was highlighted. A good correlation between the FEM simulations and the literature analysis results was observed. We note that the loading mode affects directly the J-integral value and consequently on the mechanical behaviour of the weldment.


    Directory of Open Access Journals (Sweden)

    I. S. Gusev


    Full Text Available Studies have proven that, at present one of the priority research areas as part of the Development Strategy of the Food Processing Industry of the Russian Federation until 2020 is to develop effective mechanisms for sustainable socio-economic development of industrial enterprises. This article investigated the logic of strategic planning within the framework of sustainable economic growth, analyzed the structure of strategic planning, study the subject of strategic planning in the management of sustainable development of enterprises, justified the basic principles of strategic planning for the effective management of sustainable development of industrial enterprises, as well as the complex of organizational tactical activities of operational management strategy for sustainable development of the enterprise. The observation revealed that currently there was a high need for the framework of the branch, departmental and state programs implemented in industrial management of scientific and methodological approaches of strategic planning. Studies have shown that these approaches in its conceptual entity should be based on the growth potential of the sustainable development of meat processing plants in space and time in order to achieve high competitive advantages. Conducted a systematic analysis of industry conditions proved that the problem of sustainable operation and development of meat processing enterprises as a problem of management and control is relatively new, unexplored and highly relevant. On the contrary, it is the basis of modern management strategy and management is a concept and methodology of the so-called adaptive enterprise development under the action of various external and internal factors, risks that may threaten its economic stability and sustainability.

  15. Control of Bone Anabolism in Response to Mechanical Loading and PTH by Distinct Mechanisms Downstream of the PTH Receptor. (United States)

    Delgado-Calle, Jesus; Tu, Xiaolin; Pacheco-Costa, Rafael; McAndrews, Kevin; Edwards, Rachel; Pellegrini, Gretel G; Kuhlenschmidt, Kali; Olivos, Naomie; Robling, Alexander; Peacock, Munro; Plotkin, Lilian I; Bellido, Teresita


    Osteocytes integrate the responses of bone to mechanical and hormonal stimuli by poorly understood mechanisms. We report here that mice with conditional deletion of the parathyroid hormone (PTH) receptor 1 (Pth1r) in dentin matrix protein 1 (DMP1)-8kb-expressing cells (cKO) exhibit a modest decrease in bone resorption leading to a mild increase in cancellous bone without changes in cortical bone. However, bone resorption in response to endogenous chronic elevation of PTH in growing or adult cKO mice induced by a low calcium diet remained intact, because the increased bone remodeling and bone loss was indistinguishable from that exhibited by control littermates. In contrast, the bone gain and increased bone formation in cancellous and cortical bone induced by daily injections of PTH and the periosteal bone apposition induced by axial ulna loading were markedly reduced in cKO mice compared to controls. Remarkably, however, wild-type (WT) control littermates and transgenic mice overexpressing SOST injected daily with PTH exhibit similar activation of Wnt/β-catenin signaling, increased bone formation, and cancellous and cortical bone gain. Taken together, these findings demonstrate that Pth1r in DMP1-8kb-expressing cells is required to maintain basal levels of bone resorption but is dispensable for the catabolic action of chronic PTH elevation; and it is essential for the anabolic actions of daily PTH injections and mechanical loading. However, downregulation of Sost/sclerostin, previously shown to be required for bone anabolism induced by mechanical loading, is not required for PTH-induced bone gain, showing that other mechanisms downstream of the Pth1r in DMP1-8kb-expressing cells are responsible for the hormonal effect. © 2016 American Society for Bone and Mineral Research. © 2016 American Society for Bone and Mineral Research.

  16. The clean development mechanism's contribution to sustainable development: A review of the literature

    DEFF Research Database (Denmark)

    Olsen, Karen Holm


    The challenges of how to respond to climate change and ensure sustainable development are currently high on the political agenda among the world's leading nations. The Clean Development Mechanism (CDM) is part of the global carbon market developing rapidly as part of the Kyoto response towards...... the mitigation of global warming. One of the aims of the CDM is to achieve sustainable development in developing countries, but uncertainty prevails as to whether the CDM is doing what it promises to do. Close to 200 studies on the CDM have been carried out since its birth in 1997 including peer...

  17. From mechanical loading to collagen synthesis, structural changes and function in human tendon

    DEFF Research Database (Denmark)

    Kjær, Michael; Langberg, Henning; Heinemeier, Katja


    a similar response whether the tendon was stimulated by concentric, isometric or eccentric muscle contraction, suggesting that strain rather that stress/torque determines the collagen-synthesis stimulating response seen with exercise. The adaptation time to chronic loading is longer in tendon tissue...... of TGF-beta, PGE2, IGF-I plus its binding proteins and interleukin-6 takes place after exercise. The increase in IGF-I expression in tendon includes the isoform that has so far been thought only to exist in skeletal muscle (mechano growth factor). The increase in IGF-I and procollagen expression showed...... compared with contractile elements of skeletal muscle or the heart, and only with very prolonged loading are significant changes in gross dimensions of the tendon observed, suggesting that habitual loading is associated with a robust change in the size and mechanical properties of human tendons...

  18. Characteristics of physical loads endured by military officers of mechanized troops during field maneuvres

    Directory of Open Access Journals (Sweden)

    I.L. Shlyamar


    Full Text Available Purpose: observation over influence of physical loads on military officers in process of acquiring and mastering of military applied skills during field maneuvers. Material: in experiment 120 military officers of 20-25 years old age with equal physical fitness participated. Results: it was determined that in period of field maneuvers the greatest load was endured by military officers in attack exercises and on the march. The least physical loads were in period of organization and fulfillment of combat shooting. It was also established that main part of motor actions was fulfilled in aerobic mode. Military officers’ functioning in field maneuvers was accompanied by heart beats rate of 120-150 b.p.m. and 60-90 b.p.m. during long time. Conclusions: We offered to practice physical training of mechanized units’ military officers in modes, close to field ones.

  19. Computational modeling of dynamic mechanical properties of pure polycrystalline magnesium under high loading strain rates

    Directory of Open Access Journals (Sweden)

    Li Qizhen


    Full Text Available Computational simulations were performed to investigate the dynamic mechanical behavior of pure polycrystalline magnesium under different high loading strain rates with the values of 800, 1000, 2000, and 3600 s−1. The Johnson-Cook model was utilized in the simulations based on finite element modeling. The results showed that the simulations provided well-matched predictions of the material behavior such as the strain rate-time history, the stress-strain curve, and the temperature increase. Under high loading strain rates, the tested material experienced linear strain hardening at the early stage of plastic deformation, increased strain hardening at the intermediate plastic deformation region, and decreased strain hardening at the region before fracture. The strain hardening rates for the studied high loading strain rate cases do not vary much with the change of strain rates.

  20. Effect of kenaf short fiber loading on mechanical properties of biocomposites (United States)

    Andilolo, J.; Nikmatin, S.; Nugroho, N.; Alatas, H.; Wismogroho, A. S.


    The research of biocomposite product with kenaf (Hibiscus cannabinus) short fiber as a filler and Acrylonitrile Butadiene Styrene (ABS) as the matrix had been done to understand the mechanical properties of this material. Kenaf short fiber was obtained from mechanical sieving after doing the mechanical milling. TAPPI method has been done to determine the chemical properties. In order to form a granular biocomposite a single screw extruder was performed with a variation of particle loading 10 and 15%. The original of acrylonitrile butadiene styrene (ABS) has been used as matrix. The fabrication of speciment had been done by molding injection process. Mechanical properties test was done by ASTM standarization. The results showed the density of the fibers of 1.008 g/cm3 with a fiber length of 897.07 µm and a diameter of 66.38 µm. Tensile strength of kenaf short fiber loading 10 and 15% was 23.522 ± 8.36 MPa and 20.739 ± 6.79 MPa, respectively. The tensile properties showed a decreasing trend as the fiber loading was increased. The values of impact strength were 68.657 ± 4.89 kJ m-2 and 82.090 ± 5.56 kJ m-2, respectively and the hardness values were 96.60 ± 6.03 HR and 105.20 ± 13.17 HR, respectively. Kenaf fiber can be a good reinforcement candidate for high performance polymer bio-composites.

  1. Fluid load support and contact mechanics of hemiarthroplasty in the natural hip joint. (United States)

    Pawaskar, Sainath Shrikant; Ingham, Eileen; Fisher, John; Jin, Zhongmin


    The articular cartilage covering the ends of the bones of diarthrodial synovial joints is thought to have evolved so that the loads are transferred under different and complex conditions, with a very high degree of efficiency and without compromising the structural integrity of the tissue for the life of an individual. These loading conditions stem from different activities such as walking, and standing. The integrity of cartilage may however become compromised due to congenital disease, arthritis or trauma. Hemiarthroplasty is a potentially conservative treatment when only the femoral cartilage is affected as in case of femoral neck fractures. In hemiarthroplasty, a metallic femoral prosthesis is used to articulate against the natural acetabular cartilage. It has also been hypothesized that biphasic lubrication is the predominant mechanism protecting the cartilage through a very high fluid load support which lowers friction. This may be altered due to hemiarthroplasty and have a direct effect on the frictional shear stresses and potentially cartilage degradation and wear. This study modelled nine activities of daily living and investigated the contact mechanics of a hip joint with a hemiarthroplasty, focussing particularly on the role of the fluid phase. It was shown that in most of the activities studied the peak contact stresses and peak fluid pressures were in the superior dome or lateral roof of the acetabulum. Total fluid load support was very high (~90%) in most of the activities which would shield the solid phase from being subjected to very high contact stresses. This was dependent not only on the load magnitude but also the direction and hence on the location of the contact area with respect to the cartilage coverage. Lower fluid load support was found when the contact area was nearer the edges where the fluid drained easily. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

  2. Alterations in Leg Extensor Muscle-Tendon Unit Biomechanical Properties With Ageing and Mechanical Loading

    Directory of Open Access Journals (Sweden)

    Christopher McCrum


    Full Text Available Tendons transfer forces produced by muscle to the skeletal system and can therefore have a large influence on movement effectiveness and safety. Tendons are mechanosensitive, meaning that they adapt their material, morphological and hence their mechanical properties in response to mechanical loading. Therefore, unloading due to immobilization or inactivity could lead to changes in tendon mechanical properties. Additionally, ageing may influence tendon biomechanical properties directly, as a result of biological changes in the tendon, and indirectly, due to reduced muscle strength and physical activity. This review aimed to examine age-related differences in human leg extensor (triceps surae and quadriceps femoris muscle-tendon unit biomechanical properties. Additionally, this review aimed to assess if, and to what extent mechanical loading interventions could counteract these changes in older adults. There appear to be consistent reductions in human triceps surae and quadriceps femoris muscle strength, accompanied by similar reductions in tendon stiffness and elastic modulus with ageing, whereas the effect on tendon cross sectional area is unclear. Therefore, the observed age-related changes in tendon stiffness are predominantly due to changes in tendon material rather than size with age. However, human tendons appear to retain their mechanosensitivity with age, as intervention studies report alterations in tendon biomechanical properties in older adults of similar magnitudes to younger adults over 12–14 weeks of training. Interventions should implement tendon strains corresponding to high mechanical loads (i.e., 80–90% MVC with repetitive loading for up to 3–4 months to successfully counteract age-related changes in leg extensor muscle-tendon unit biomechanical properties.

  3. A new method to investigate how mechanical loading of osteocytes controls osteoblasts

    Directory of Open Access Journals (Sweden)

    Marisol eVazquez


    Full Text Available Mechanical loading, a potent stimulator of bone formation, is governed by osteocyte regulation of osteoblasts. We developed a 3D in vitro co-culture system to investigate the effect of loading on osteocyte-osteoblast interactions. MLO-Y4 cells were embedded in type I collagen gels and MC3T3-E1(14 or MG63 cells layered on top. Ethidium homodimer staining of 3D co-cultures showed 100 % osteoblasts and 86 % osteocytes were viable after 7 days. Microscopy revealed osteoblasts and osteocytes maintain their respective ovoid/pyriform and dendritic morphologies in 3D co-cultures. Reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR of messenger ribonucleic acid (mRNA extracted separately from osteoblasts and osteocytes, showed that Podoplanin (E11, osteocalcin (OCN and runt-related transcription factor 2 (Runx2 mRNAs were expressed in both cell types. Type I collagen (Col1a1 mRNA expression was higher in osteoblasts (P<0.001, whereas alkaline phosphatase (ALP mRNA was higher in osteocytes (P=0.001. Immunohistochemistry revealed osteoblasts and osteocytes express E11, type I pro-collagen and connexin 43 (CX43 proteins. In preliminary experiments to assess osteogenic responses, co-cultures were treated with human recombinant bone morphogenetic protein 2 (BMP-2 or mechanical loading using a custom built loading device. BMP-2 treatment significantly increased osteoblast Col1a1 mRNA synthesis (P=0.031 in MLO-Y4/MG63 co-cultures after 5 days treatment. A 16-well silicone plate, loaded (5 min, 10 Hz, 2.5 N to induce 4000-4500 με cyclic tension within gels increased prostaglandin E2 (PGE2 release 0.5 hr post-load in MLO-Y4 cells pre-cultured in 3D collagen gels for 48 hr, 72 hr, or 7 days. Mechanical loading of 3D co-cultures increased type I pro-collagen release 1 and 5 days later. These methods reveal a new osteocyte-osteoblast co-culture model that may be useful for investigating mechanically-induced osteocyte control of osteoblast bone

  4. Effect of Mechanical Load Cycling on Microtensile Bond Strength of Self-Etch Systems to Dentin

    Directory of Open Access Journals (Sweden)

    Sh. Kasraei


    Full Text Available Objective: Optimal dentin bonding is not always obtained in clinical practice due to func-tional forces. These forces may provide stresses throughout the tooth and restorative sys-tem, which in turn may affect the adhesive bond. This experimental study evaluated the effect of load cycling on bond strength of self-etch systems.Materials and Methods: One third of the coronal portions of 48 intact human extractedupper premolars were removed. The teeth were equally divided into six groups. In groups Unloaded-Clear tri-S Bond (ULCB and Loaded-Clear tri-S Bond (LCB, prepared dentin surfaces of each tooth were treated with Clearfil tri-S Bond (Kurary medical inc, Oka-yama, Japan, in groups Unloaded-I Bond (ULIB and Loaded-I Bond (LIB with I bond (Heraeus Kulzer, GmbH,&Co KG, Germany, and in groups Unloaded-Xeno III (ULX and Loaded-Xeno III (LX with Xeno III dentin adhesives (Dentsply Detrey GmbH, Kon-stanz, Germany. Then, the teeth were restored with Filtek Supreme resin composite. After thermal cycling of the samples, Groups LCB, LIB and LX were submitted to mechanical loading (100,000 cycles, 60 N. Microtensile bond strength (MTBS test was performed for all of groups. Two-way ANOVA and Tukey HSD tests served for statistical analysis.Results: Results showed that groups ULCB and ULIB had significantly more bond strength than group ULX (P<0.05. For all the tree adhesive systems, the MTBS values in teeth subjected to load cycling was significantly lower than unloaded teeth (P<0.001.Conclusion: Load cycling seems to decrease MTBSs of one-step adhesive systems to den-tin.

  5. Pharmaceutical suspension containing both immediate/sustained-release amoxicillin-loaded gelatin nanoparticles: preparation and in vitro characterization (United States)

    Harsha, Sree


    Pharmaceutical suspension containing oral dosage forms delivering both immediate-release and sustained-release amoxicillin was developed as a new dosage form to eradicate Helicobacter pylori. Amoxicillin-loaded gelatin nanoparticles are able to bind with the mucosal membrane after delivery to the stomach and could escalate the effectiveness of a drug, providing dual release. The objective of this study was to develop amoxicillin nanoparticles using innovative new technology – the Büchi Nano Spray Dryer B-90 – and investigate such features as drug content, particle morphology, yield, in vitro release, flow properties, and stability. The nanoparticles had an average particle size of 571 nm. The drug content and percentage yield was 89.2% ± 0.5% and 93.3% ± 0.6%, respectively. Angle of repose of nanoparticle suspension was 26.3° and bulk density was 0.59 g/cm3. In vitro drug release of formulations was best fitted by first-order and Peppas models with R2 of 0.9841 and 0.9837 respectively; release profile was 15.9%, while; for the original drug, amoxicillin, under the same conditions, 90% was released in the first 30 minutes. The nanoparticles used in this study enabled sustained release of amoxicillin over an extended period of time, up to 12 hours, and were stable for 12 months under accelerated storage conditions of 25°C ± 2°C and 60% ± 5% relative humidity. PMID:24101859

  6. Sustainable organic loading rate and energy recovery potential of mesophilic anaerobic membrane bioreactor for municipal wastewater treatment

    KAUST Repository

    Wei, Chunhai


    The overall performance of a mesophilic anaerobic membrane bioreactor (AnMBR) for synthetic municipal wastewater treatment was investigated under a range of organic loading rate (OLR). A very steady and high chemical oxygen demand (COD) removal (around 98%) was achieved over a broad range of volumetric OLR of 0.8-10gCOD/L/d. The sustainable volumetric and sludge OLR satisfying a permeate COD below 50mg/L for general reuse was 6gCOD/L/d and 0.63gCOD/gMLVSS (mixed liquor volatile suspended solids)/d, respectively. At a high sludge OLR of over 0.6gCOD/gMLVSS/d, the AnMBR achieved high methane production of over 300ml/gCOD (even approaching the theoretical value of 382ml/gCOD). A low biomass production of 0.015-0.026gMLVSS/gCOD and a sustainable flux of 6L/m2/h were observed. The integration of a heat pump and forward osmosis into the mesophilic AnMBR process would be a promising way for net energy recovery from typical municipal wastewater in a temperate area. © 2014 Elsevier Ltd.

  7. Antimicrobial, Mechanical and Thermal Studies of Silver Particle-Loaded Polyurethane

    Directory of Open Access Journals (Sweden)

    Deepen Paul


    Full Text Available Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli and Staphylococcus aureus (S. aureus. Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU and variously characterized by field emission scanning electron microscopy (FESEM, fourier transform infra-red (FTIR spectroscopy, X-ray diffraction (XRD and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w AgNO3, 1% and 10% (w/w Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young’s modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA indicated greater thermal stability.

  8. Mechanical behavior of ultrafine-grained materials under combined static and dynamic loadings

    Directory of Open Access Journals (Sweden)

    Guo Y.Z.


    Full Text Available Ultrafine-grained (UFG materials have extensive prospects for engineering application due to their excellent mechanical properties. However, the grain size decrease reduces their strain hardening ability and makes UFG materials more susceptible to deformation instability such as shear localization. In most cases, critical shear strain is taken as the criterion for formation of shear localization under impact loading or adiabatic shear band (ASB. Recently, some researchers found that the formation of ASB was determined only by the dynamic loading process and had nothing to do with its static loading history. They proposed for coarse-grained metals a dynamic stored energy-based criterion for ASB and verified it by some experiments. In this study, we will focus on the shear localization behavior of UFG metals such as UFG titanium and magnesium alloy AZ31. Quasi-static loading and dynamic loading will be applied on the same specimen alternately. The shear localization behavior will be analyzed and the criterion of its formation will be evaluated.

  9. The Effect of Kettlebell Swing Load and Cadence on Physiological, Perceptual and Mechanical Variables

    Directory of Open Access Journals (Sweden)

    Michael J. Duncan


    Full Text Available This study compared the physiological, perceptual and mechanical responses to kettlebell swings at different loads and swing speeds. Following familiarization 16 strength trained participants (10 males, six females, mean age ± SD = 23 ± 2.9 performed four trials: 2 min kettlebell swings with an 8 kg kettlebell at a fast cadence; 2 min kettlebell swings with an 8 kg kettlebell at a slow cadence; 4 min kettlebell swings with a 4 kg kettlebell at a fast cadence; 4 min kettlebell swings with a 4 kg kettlebell at a slow cadence. Repeated measured analysis of variance indicated no significant differences in peak blood lactate or peak net vertical force across loads and cadences (P > 0.05. Significant main effect for time for heart rate indicated that heart rate was higher at the end of each bout than at mid-point (P = 0.001. A significant Load X cadence interaction for rating of perceived exertion (RPE (P = 0.030 revealed that RPE values were significantly higher in the 8 kg slow cadence condition compared to the 4 kg slow (P = 0.002 and 4 kg fast (P = 0.016 conditions. In summary, this study indicates that the physiological and mechanical responses to kettlebell swings at 4 kg and 8 kg loads and at fast and slow cadence were similar, whereas the perceptual response is greater when swinging an 8 kg kettlebell at slow cadence.

  10. Mechanically tuned nanocomposite coating on titanium metal with integrated properties of biofilm inhibition, cell proliferation, and sustained drug delivery. (United States)

    Mishra, Sandeep K; Teotia, Arun K; Kumar, Ashok; Kannan, Sanjeevi


    The clinical success of coated implants in executing biological functions inclusive of sustainable drug release and long term antibacterial activity without antibiotics is critical. To this aim, a nanohybrid of silver nanoparticles (AgNPs) cored in polyvinyl alcohol nanocapsules (Ag-PVA NCs) embedded in chitosan (CS) matrix loaded with anti-inflammatory drug naproxen was prepared. The synthesized nanohybrids that were subjected to coatings on (3-aminopropyl)triethoxysilane (APTES) treated titanium (Ti) metal exhibited dual role of excellent inhibition on biofilm formation and sustained drug release. These dual characteristics are achieved mainly based on intrinsic antibacterial property of AgNPs and differential entrapment of drug in PVA polymeric shell of AgNPs and CS matrix. The coatings also demonstrated enhanced mechanical properties with increasing inorganic filler and stress shielding on Ti metal. The biocompatibility tests involving adhesion, proliferation and differentiation of osteoblast cells demonstrated the efficacy of Ag-PVA NCs embedded in CS matrix as a suitable coating material for orthopedic applications. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Interactive evolution concept for analyzing a rock salt cavern under cyclic thermo-mechanical loading (United States)

    König, Diethard; Mahmoudi, Elham; Khaledi, Kavan; von Blumenthal, Achim; Schanz, Tom


    The excess electricity produced by renewable energy sources available during off-peak periods of consumption can be used e.g. to produce and compress hydrogen or to compress air. Afterwards the pressurized gas is stored in the rock salt cavities. During this process, thermo-mechanical cyclic loading is applied to the rock salt surrounding the cavern. Compared to the operation of conventional storage caverns in rock salt the frequencies of filling and discharging cycles and therefore the thermo-mechanical loading cycles are much higher, e.g. daily or weekly compared to seasonally or yearly. The stress strain behavior of rock salt as well as the deformation behavior and the stability of caverns in rock salt under such loading conditions are unknown. To overcome this, existing experimental studies have to be supplemented by exploring the behavior of rock salt under combined thermo-mechanical cyclic loading. Existing constitutive relations have to be extended to cover degradation of rock salt under thermo-mechanical cyclic loading. At least the complex system of a cavern in rock salt under these loading conditions has to be analyzed by numerical modeling taking into account the uncertainties due to limited access in large depth to investigate material composition and properties. An interactive evolution concept is presented to link the different components of such a study - experimental modeling, constitutive modeling and numerical modeling. A triaxial experimental setup is designed to characterize the cyclic thermo-mechanical behavior of rock salt. The imposed boundary conditions in the experimental setup are assumed to be similar to the stress state obtained from a full-scale numerical simulation. The computational model relies primarily on the governing constitutive model for predicting the behavior of rock salt cavity. Hence, a sophisticated elasto-viscoplastic creep constitutive model is developed to take into account the dilatancy and damage progress, as well as

  12. Can the Clean Development Mechanism attain both cost-effectiveness and sustainable development objectives?

    Energy Technology Data Exchange (ETDEWEB)

    Kolshus, Hans H; Vevatne, Jonas; Torvanger, Asbjoern; Aunan, Kristin


    The Clean Development Mechanism (CDM), as defined in the Kyoto Protocol, has two objectives: to promote sustainable development in host developing countries, and to improve global cost-effectiveness by assisting developed countries in meeting their Kyoto targets. The aim of this paper is to explore the background of the CDM and discuss to what extent its current design allows it to achieve its dual objective. The first part of the paper is a literature review that includes descriptions of the flexibility mechanisms under the Kyoto Protocol; the CDM's market potential, and the issues of cost-effectiveness and sustainable development. In the second part of the paper, we discuss to what extent there is a conflict between cost-effectiveness and sustain ability, and whether the two objectives of the CDM can be achieved simultaneously. We develop a set of indicators to evaluate non-carbon benefits of CDM projects on the environment, development, and. equity, and show how these indicators can be used in practice by looking at case studies of CDM project candidates in the energy sector from Brazil and China. We demonstrate that for some CDM projects there is a trade-off between cost-effectiveness, in terms of a low quota price, and a high score on sustain ability indicators. We have reason to believe that the size of the CDM market in some studies is over-estimated since transaction costs and the challenge of promoting sustainable development are not fully accounted for. Also, we find that the proposed set of indicators can be a necessary tool to assure that sustain ability impacts of CDM projects are taken into consideration. (author)

  13. Mechanical dynamic load of the LHC arc cryo-magnets during the installation

    CERN Document Server

    Artoos, K; Huet, G; Nicquevert, B


    About 1700 LHC main superconducting dipoles and quadrupoles will have to be transported and handled between the assembly, the magnet measurements and the storage that precedes the final installation in the LHC tunnel. To ensure the required mechanic and geometric integrity of the cryo-magnets, transport specifications and allowed acceleration loads were defined after detailed dynamic analysis. A large number of cryo-magnets are now arriving at CERN on a regular basis. The logistics for the handling and transport are monitored with tri-axial acceleration monitoring devices that are installed on each cryo-magnet. Measurements are made to commission new equipment like overhead cranes, tunnel transport and handling devices to guarantee that the defined acceleration limits are respected. The results from the acceleration monitoring that are stored in the same quality assurance system as the cryo-magnets allowed to give a first idea of the level of the mechanical dynamic load on each magnet throughout the logistics...

  14. Real-time measurement of solute transport within the lacunar-canalicular system of mechanically loaded bone: direct evidence for load-induced fluid flow. (United States)

    Price, Christopher; Zhou, Xiaozhou; Li, Wen; Wang, Liyun


    Since proposed by Piekarski and Munro in 1977, load-induced fluid flow through the bone lacunar-canalicular system (LCS) has been accepted as critical for bone metabolism, mechanotransduction, and adaptation. However, direct unequivocal observation and quantification of load-induced fluid and solute convection through the LCS have been lacking due to technical difficulties. Using a novel experimental approach based on fluorescence recovery after photobleaching (FRAP) and synchronized mechanical loading and imaging, we successfully quantified the diffusive and convective transport of a small fluorescent tracer (sodium fluorescein, 376 Da) in the bone LCS of adult male C57BL/6J mice. We demonstrated that cyclic end-compression of the mouse tibia with a moderate loading magnitude (-3 N peak load or 400 µε surface strain at 0.5 Hz) and a 4-second rest/imaging window inserted between adjacent load cycles significantly enhanced (+31%) the transport of sodium fluorescein through the LCS compared with diffusion alone. Using an anatomically based three-compartment transport model, the peak canalicular fluid velocity in the loaded bone was predicted (60 µm/s), and the resulting peak shear stress at the osteocyte process membrane was estimated (∼5 Pa). This study convincingly demonstrated the presence of load-induced convection in mechanically loaded bone. The combined experimental and mathematical approach presented herein represents an important advance in quantifying the microfluidic environment experienced by osteocytes in situ and provides a foundation for further studying the mechanisms by which mechanical stimulation modulates osteocytic cellular responses, which will inform basic bone biology, clinical understanding of osteoporosis and bone loss, and the rational engineering of their treatments. Copyright © 2011 American Society for Bone and Mineral Research.

  15. An Innovative Design of a Microtab Deployment Mechanism for Active Aerodynamic Load Control


    Kuo-Chang Tsai; Cheng-Tang Pan; Aubryn M. Cooperman; Johnson, Scott J.; C. P. van Dam


    This study presents an innovative design of a microtab system for aerodynamic load control on horizontal-axis wind-turbine rotors. Microtabs are small devices located near the trailing edge of the rotor blades and enable a rapid increase or decrease of the lift force through deployment of the tabs on the pressure or suction side of the airfoil, respectively. The new system has been designed to replace an earlier linearly-actuated microtab mechanism whose performance was limited by space restr...

  16. Fatigue properties and fracture mechanism of load carrying type fillet joints with one-sided welding


    Takamasa Abe; Hiroyuki Akebono; Masahiko Kato; Atsushi Sugeta


    The structures of the hydraulic excavator and the crane have numerous one-sided welded joints. However, attachments with box like structures are difficult to weld at both sides. Therefore, high accurate evaluation method is needed. In this study, the fatigue properties and the fracture mechanism of the load carrying type fillet joints with one-sided welding were investigated experimentally to evaluate its fatigue damage with high accuracy based on the experimental results. As the ...

  17. The mechanisms of renal functional reserves during the day after the load of ammonium chloride

    Directory of Open Access Journals (Sweden)

    Наталия Ивановна Бурлака


    Full Text Available For the study of renal function and mechanisms of inclusion of renal functional reserve the research was done on rats with different levels of isolation acids and ammonia. To activate the excretion of acid and ammonia rats were injected a 1.0 M solution of ammonium chloride at a dose of 20 mg/kg of body weight into the stomach 1 hour before water loading

  18. Coaxial Electrospray of Curcumin-Loaded Microparticles for Sustained Drug Release.

    Directory of Open Access Journals (Sweden)

    Shuai Yuan

    Full Text Available Curcumin exhibits superior anti-inflammatory, antiseptic and analgesic activities without significant side effects. However, clinical dissemination of this natural medicine is limited by its low solubility and poor bio-availability. To overcome this limitation, we propose to encapsulate curcumin in poly(lactic-co-glycolic acid (PLGA microparticles (MPs by an improved coaxial electrospray (CES process. This process is able to generate a stable cone-jet mode in a wide range of operation parameters in order to produce curcumin-loaded PLGA MPs with a clear core-shell structure and a designated size of several micrometers. In order to optimize the process outcome, the effects of primary operation parameters such as the applied electric voltages and the liquid flow rates are studied systemically. In vitro drug release experiments are also carried out for the CES-produced MPs in comparison with those by a single axial electrospray process. Our experimental results show that the CES process can be effectively controlled to encapsulate drugs of low aqueous solubility for high encapsulation efficiency and optimal drug release profiles.

  19. Aging and loading rate effects on the mechanical behavior of equine bone (United States)

    Kulin, Robb M.; Jiang, Fengchun; Vecchio, Kenneth S.


    Whether due to a sporting accident, high-speed impact, fall, or other catastrophic event, the majority of clinical bone fractures occur under dynamic loading conditions. However, although extensive research has been performed on the quasi-static fracture and mechanical behavior of bone to date, few high-quality studies on the fracture behavior of bone at high strain rates have been performed. Therefore, many questions remain regarding the material behavior, including not only the loading-rate-dependent response of bone, but also how this response varies with age. In this study, tests were performed on equine femoral bone taken post-mortem from donors 6 months to 28 years of age. Quasi-static and dynamic tests were performed to determine the fracture toughness and compressive mechanical behavior as a function of age at varying loading rates. Fracture paths were then analyzed using scanning confocal and scanning-electron microscopy techniques to assess the role of various microstructural features on toughening mechanisms.

  20. MEMS measurements of single cell stiffness decay due to cyclic mechanical loading. (United States)

    Barazani, Bruno; Warnat, Stephan; MacIntosh, Andrew J; Hubbard, Ted


    The goal of this study was to measure the mechanical stiffness of individual cells and to observe changes due to the application of repeated cell mechanical loads. 28 single baker's yeast cells (Saccharomyces cerevisiae) were fatigue tested and had their stiffness measured during repetitive loading cycles performed by a MEMS squeezer in aqueous media. Electrothermal micro-actuators compressed individual cells against a reference back spring; cell and spring motions were measured using a FFT image analysis technique with ~10 nm resolution. Cell stiffness was calculated based on measurements of cell elongation vs. applied force which resulted in stiffness values in the 2-10 N/m range. The effect of increased force was studied for cells mechanically cycled 37 times. Cell stiffness decreased as the force and the cycle number increased. After 37 loading cycles (~4 min), forces of 0.24, 0.29, 0.31, and 0.33 μN caused stiffness drops of 5%, 13%, 31% and 41% respectively. Cells force was then set to 0.29 μN and cells were tested over longer runs of 118 and 268 cycles. After 118 cycles (~12 min) cells experienced an average stiffness drop of 68%. After 268 cycles (~25 min) cells had a stiffness drop of 77%, and appeared to reach a stiffness plateau of 20-25% of the initial stiffness after approximately 200 cycles.

  1. Mechanical loading regulates organization of the actin cytoskeleton and column formation in postnatal growth plate. (United States)

    Killion, Christy H; Mitchell, Elizabeth H; Duke, Corey G; Serra, Rosa


    Longitudinal growth of bones occurs at the growth plates where chondrocytes align into columns that allow directional growth. Little is known about the mechanisms controlling the ability of chondrocytes to form columns. We hypothesize that mechanical load and the resulting force on chondrocytes are necessary during active growth for proper growth plate development and limb length. To test this hypothesis, we created a mouse model in which a portion of the sciatic nerve from one hind limb was transected at postnatal day 8 to cause paralysis to that limb. At 6 and 12 wk postsurgery, the hind limb had significantly less bone mineral density than contralateral controls, confirming reduced load. At 8 and 14 wk postsurgery, tibiae were significantly shorter than controls. The paralyzed growth plate showed disruptions to column organization, with fewer and shorter columns. Polarized light microscopy indicated alterations in collagen fiber organization in the growth plate. Furthermore, organization of the actin cytoskeleton in growth plate chondrocytes was disrupted. We conclude that mechanical load and force on chondrocytes within the growth plate regulate postnatal development of the long bones. © 2017 Killion, Mitchell, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (

  2. Role of sublayers in mechanical response of pulsed electron beam irradiated surface layers to contact load (United States)

    Konovalenko, Igor S.


    Here we develop the movable cellular automaton method based a numerical model of surface layers in a NiCr-TiC metal ceramic composite modified by pulsed electron beam irradiation in inert gas plasmas. The model explicitly takes into account the presence of several sublayers differing in structure and mechanical properties. The contribution of each sublayer to the mechanical response of the modified surface to contact loading is studied. It is shown that the maximum strength and fracture toughness are achieved in surface layers containing thin and stiff external sublayers and a more ductile thick internal sublayer.

  3. Mechanisms involved in regulation of osteoclastic differentiation by mechanical stress-loaded osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Kaneuji, Takeshi [Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Ariyoshi, Wataru; Okinaga, Toshinori; Toshinaga, Akihiro [Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Takahashi, Tetsu [Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Oral Bioresearch Center, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Nishihara, Tatsuji, E-mail: [Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Oral Bioresearch Center, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan)


    Highlights: {yields} Effect of compressive force on osteoblasts were examined. {yields} Compressive force induced OPG expression and suppressed osteoclastogenesis. {yields} This enhancement of OPG is dependent on Wnt/Ca2+ signal pathway. -- Abstract: Mechanical stress is known to be important for regulation of bone turnover, though the detailed mechanisms are not fully understood. In the present study, we examined the effect of mechanical stress on osteoblasts using a novel compression model. Mouse osteoblastic MC3T3-E1 cells were embedded in three-dimensional (3D) gels and cultured with continuous compressive force (0-10.0 g/cm{sup 2}) for 48 h, and the conditioned medium were collected. RAW264.7 cells were then incubated with the conditioned medium for various times in the presence of receptor activator of nuclear factor-{kappa}B ligand (RANKL). Conditioned medium was found to inhibit the differentiation of RAW264.7 cells into osteoclasts induced by RANKL via down-regulation of the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6), phosphorylation of I{kappa}B{alpha}, and nuclear translocation of p50 and p65. Interestingly, the conditioned medium also had a high level of binding activity to RANKL and blocked the binding of RANK to RANKL. Furthermore, the binding activity of conditioned medium to RANKL was reduced when the 3D gel was supplemented with KN-93, an inhibitor of non-canonical Wnt/Ca{sup 2+} pathway. In addition, expression level of osteoprotegerin (OPG) mRNA was increased in time- and force-dependent manners, and remarkably suppressed by KN-93. These results indicate that osteoblastic cells subjected to mechanical stress produce OPG, which binds to RANKL. Furthermore, this binding activity strongly inhibited osteoclastogenesis through suppression of TRAF6 and the nuclear factor-kappa B (NF-{kappa}B) signaling pathway, suggesting that enhancement of OPG expression induced by mechanical stress is dependent on non-canonical Wnt

  4. Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

    Directory of Open Access Journals (Sweden)

    Luc Leroy Ngueyep. Mambou


    Full Text Available The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton's second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the mechanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 °C to 500 °C, the internal stress and internal strain are weak; whereas above 500 °C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

  5. Promoting sustainable development or legitimising free trade? Civil society mechanisms in EU trade agreements


    Orbie, Jan; Martens, Deborah; Oehri, Myriam; Van Den Putte, Lore


    This study critically reflects on the involvement of civil society actors in the sustainable development chapters of recent EU trade agreements. It discusses how civil society mechanisms may legitimise the underlying neoliberal orientation of the agreements through co-optation of critical actors. Starting from a critical perspective and drawing on evidence from innovative survey data, qualitative interviews and participatory observations, it concludes that, despite overall criticism, there is...

  6. Locomotor loading mechanics in the hindlimbs of tegu lizards (Tupinambis merianae): comparative and evolutionary implications. (United States)

    Sheffield, K Megan; Butcher, Michael T; Shugart, S Katherine; Gander, Jennifer C; Blob, Richard W


    Skeletal elements are usually able to withstand several times their usual load before they yield, and this ratio is known as the bone's safety factor. Limited studies on amphibians and non-avian reptiles have shown that they have much higher limb bone safety factors than birds and mammals. It has been hypothesized that this difference is related to the difference in posture between upright birds and mammals and sprawling ectotherms; however, limb bone loading data from a wider range of sprawling species are needed in order to determine whether the higher safety factors seen in amphibians and non-avian reptiles are ancestral or derived conditions. Tegus (family Teiidae) are an ideal lineage with which to expand sampling of limb bone loading mechanics for sprawling taxa, particularly for lizards, because they are from a different clade than previously sampled iguanas and exhibit different foraging and locomotor habits (actively foraging carnivore versus burst-activity herbivore). We evaluated the mechanics of locomotor loading for the femur of the Argentine black and white tegu (Tupinambus merianae) using three-dimensional measurements of the ground reaction force and hindlimb kinematics, in vivo bone strains and femoral mechanical properties. Peak bending stresses experienced by the femur were low (tensile: 10.4 ± 1.1 MPa; compressive: -17.4 ± 0.9 MPa) and comparable to those in other reptiles, with moderate shear stresses and strains also present. Analyses of peak femoral stresses and strains led to estimated safety factor ranges of 8.8-18.6 in bending and 7.8-17.5 in torsion, both substantially higher than typical for birds and mammals but similar to other sprawling tetrapods. These results broaden the range of reptilian and amphibian taxa in which high femoral safety factors have been evaluated and further indicate a trend for the independent evolution of lower limb bone safety factors in endothermic taxa.

  7. Experimental study of low amplitude, long-duration mechanical loading of reactive materials

    Energy Technology Data Exchange (ETDEWEB)

    Urtiew, P A; Forbes, J W


    Studies of the low amplitude, long-duration mechanical loading of reactive materials rely very heavily on the experimental data in general and in particular on the data obtained from gauges placed within the experimental test sample to measure accurately the local changes of parameters of the investigated material. For a complete description of these changes taking place in a dynamically loaded material one would like to know both the spatial and the temporal resolution of pressure, temperature, volume, wave and mass velocity. However, temperature and volume are not easily attainable. Therefore, most of the in-situ work is limited to measurements of pressure and both wave and mass velocities. Various types of these gauges will be discussed and their records will be illustrated. Some of these gauges have limitations but are better suited for particular applications than others. These aspects will also be discussed. Main limitation of most in-situ gauges is that they are built for one-dimensional application. However, some work is being done to develop two-dimensional gauges. This work will also be briefly discussed. While these experiments are necessary to validate theoretical models of the phenomenon, they can also provide sufficient amount of data to yield complete information on material characteristics such as its equation of state (EOS), its phase change under certain loads and its sensitivity to shock loading. Processing of these data to get important information on the behavior of both reactive and non-reactive materials will also be demonstrated.

  8. The Effect of Cyclic Loading on the Mechanical Performance of Surgical Mesh

    Directory of Open Access Journals (Sweden)

    Ho Y.C.


    Full Text Available Polymeric meshes in the form of knitted nets are commonly used in the surgical repair of pelvic organ prolapses. Although a number of these prosthetic meshes are commercially available, there is little published data on their mechanical performance, in particular on the change in stiffness under the repeated loading experienced in vivo. In this in vitro study, cyclic tensile loading was applied to rectangular strips of four different commercially available meshes. The applied force and resultant displacement was monitored throughout the tests in order to evaluate the change in stiffness. In addition, each mesh was randomly marked using indelible ink in order to permit the use of threedimensional digital image correlation to evaluate local displacements during the tests. However, the scale and form of the deformation experienced by some of the meshes made correlation difficult so that confirmation of the values of stiffness were only obtained for two meshes. The results demonstrate that all the meshes experience an increase in stiffness during cyclic loading, that in most cases cyclic creep occurs and in some cases large-scale, irreversible reorganisation of the mesh structure occurs after as few as 200 cycles at loads of the order of 10N.

  9. A test to assess the mechanical power sustainable during everyday activities in older people. (United States)

    Capodaglio, Edda Maria; Saibene, Franco


    to define with a simple test the power sustainable by older people during everyday occupations. nine healthy subjects (65-71 years) performed two series of 5-6 trials on bicycle and arm ergometers at constant power. Throughout the exercise they reported their evaluation of the effort, referred either to perceived whole body exertion or to the working muscles, using Borg's category-ratio, CR10, scale. The exercise was interrupted when CR7 was attained. From a linear regression of the individual data of the work done from the start of each trial to the transition from CR4 to CR5, corresponding to 'somewhat heavy' and 'heavy', and the corresponding duration it was possible to calculate the slope of the work/time relationship. This was considered as the value of power sustainable for leg or arm muscles. on average the sustainable power for the work done on the bicycle ergometer represented 55% of the maximal mechanical power. During the control trial on the bicycle ergometer at a power corresponding to their sustainable power the subjects were able to exercise for 30 min without symptoms of fatigue or discomfort, with an average CR of 3. The average heart rate was 114 bpm and the blood lactate concentration at the end of the exercise was always lower than 4 mmol/l. Sustainable power calculated for the arm muscles was about one quarter that of the leg muscles, but all subjects reported the evaluation of the effort as more difficult. the determination of power sustainable for the leg muscles with this simple test appears reliable and accurate.

  10. Effect of epoxidised soybean oil loading as plasticiser on physical, mechanical and thermal properties of polyvinylchloride (United States)

    Rahmah, M.; Nurazzi, N. Mohd; Farah Nordyana, A. R.; Syed Anas, S. M.


    The aim of this paper is to study the effect of epoxidised soybean oil (ESO) as an alternative plasticizer on physical, mechanical and thermal properties of plasticised polyvinyl chloride (PPVC). Samples were prepared using 10, 20, 30 and 40% by weight percent of ESO. The samples were characterized for density, water absorption, tensile, hardness and thermal properties. The addition of ESO as plasticizer in PVC had caused significant effect on the physical and mechanical properties of PPVC. Increasing of ESO loading had resulted in decreased density, tensile strength, tensile modulus but increased in elongation at break and shore hardness. From water absorption study, it was observed that the all the samples reached the plateau absorption at days 8 to 10 with absorption percentages of between 1.8 to 2%. In general the crystallinity of PPVC maintained between 10 to 13% with increase in ESO loading while the melting point ( Tm) is slightly decreased about 3 to 6°C. In this study, ESO which acts as plasticiser were found to result in lower glass transition temperature (Tg). The enhancements of super cooling with higher ESO loading were found to increase the crystallization temperature, promoting crystallisation and act as nucleating agent.

  11. Stress State Analysis and Failure Mechanisms of Masonry Columns Reinforced with FRP under Concentric Compressive Load

    Directory of Open Access Journals (Sweden)

    Jiří Witzany


    Full Text Available The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cracks accompanied by an increase in horizontal masonry strain. During the appearance of micro and hairline cracks (10−3 to 10−1 mm, the effect of non-pre-stressed wrapping composite is very small. The favorable effect of passive wrapping is only intensively manifested after the appearance of cracks (10−1 mm and bigger at higher loading levels. In the case of “optimum” reinforcement of a masonry column, the experimental research showed an increase in vertical displacements δy (up to 247%, horizontal displacements δx (up to 742% and ultimate load-bearing capacity (up to 136% compared to the values reached in unreinforced masonry columns. In the case of masonry structures in which no intensive “bed joint filler–masonry unit” interaction occurs, e.g., in regular coursed masonry with little differences in the mechanical characteristics of masonry units and the binder, the reinforcing effect of the fabric applies only partially.

  12. Study on Mechanical Characteristics of Fully Grouted Rock Bolts for Underground Caverns under Seismic Loads

    Directory of Open Access Journals (Sweden)

    Guoqing Liu


    Full Text Available This study establishes an analytical model for the interaction between the bolt and surrounding rock based on the bearing mechanism of fully grouted rock bolts. The corresponding controlled differential equation for load transfer is deduced. The stress distributions of the anchorage body are obtained by solving the equations. A dynamic algorithm for the bolt considering shear damage on the anchoring interface is proposed based on the dynamic finite element method. The rationality of the algorithm is verified by a pull-out test and excavation simulation of a rounded tunnel. Then, a case study on the mechanical characteristics of the bolts in underground caverns under seismic loads is conducted. The results indicate that the seismic load may lead to stress originating from the bolts and damage on the anchoring interface. The key positions of the antiseismic support can be determined using the numerical simulation. The calculated results can serve as a reference for the antiseismic optimal design of bolts in underground caverns.

  13. A New Mechanical Loading Configuration for Maximizing The Performance of Dielectric Elastomer Generators (United States)

    Shian, Samuel; Huang, Jiangshui; Suo, Zhigang; Clarke, David


    Electrical energy can be generated from mechanical deformations using dielectric elastomers but currently achieved energy densities and conversion efficiencies are still small. In this presentation, we demonstrate that significant improvements, an energy density over 500 mJ/g and up to 10% in efficiency, can be produced using VHB elastomers by altering the mechanical loading geometry. A major limitation is viscous losses in the VHB elastomer indicating that higher efficiencies with other elastomers will be attainable. The basic concept of mechanical energy harvesting with a dielectric elastomer sheet is a straightforward electromechanical cycle leading to a voltage step-up: a sheet is stretched, electrical charge at low voltage is placed on either side using compliant electrodes, the stretch is released causing the sheet's initial thickness and area to be recovered increasing the charge potential which can then be harvested. Integral to maximizing the energy conversion is the amount of mechanical energy that can be stored elastically and the amount of capacitance change in the elastomer sheet during stretching. We show that these factors can be maximized by equi-biaxial loading. Details of our dielectric elastomer generator will be described as well as the procedures we use for quantifying its performance.

  14. Mechanical loading regulates human MSC differentiation in a multi-layer hydrogel for osteochondral tissue engineering. (United States)

    Steinmetz, Neven J; Aisenbrey, Elizabeth A; Westbrook, Kristofer K; Qi, H Jerry; Bryant, Stephanie J


    A bioinspired multi-layer hydrogel was developed for the encapsulation of human mesenchymal stem cells (hMSCs) as a platform for osteochondral tissue engineering. The spatial presentation of biochemical cues, via incorporation of extracellular matrix analogs, and mechanical cues, via both hydrogel crosslink density and externally applied mechanical loads, were characterized in each layer. A simple sequential photopolymerization method was employed to form stable poly(ethylene glycol)-based hydrogels with a soft cartilage-like layer of chondroitin sulfate and low RGD concentrations, a stiff bone-like layer with high RGD concentrations, and an intermediate interfacial layer. Under a compressive load, the variation in hydrogel stiffness within each layer produced high strains in the soft cartilage-like layer, low strains in the stiff bone-like layer, and moderate strains in the interfacial layer. When hMSC-laden hydrogels were cultured statically in osteochondral differentiation media, the local biochemical and matrix stiffness cues were not sufficient to spatially guide hMSC differentiation after 21 days. However dynamic mechanical stimulation led to differentially high expression of collagens with collagen II in the cartilage-like layer, collagen X in the interfacial layer and collagen I in the bone-like layer and mineral deposits localized to the bone layer. Overall, these findings point to external mechanical stimulation as a potent regulator of hMSC differentiation toward osteochondral cellular phenotypes. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Role of age and injury mechanism on cervical spine injury tolerance from head contact loading. (United States)

    Yoganandan, Narayan; Chirvi, Sajal; Voo, Liming; Pintar, Frank A; Banerjee, Anjishnu


    The objective of this study was to determine the influence of age and injury mechanism on cervical spine tolerance to injury from head contact loading using survival analysis. This study analyzed data from previously conducted experiments using post mortem human subjects (PMHS). Group A tests used the upright intact head-cervical column experimental model. The inferior end of the specimen was fixed, the head was balanced by a mechanical system, and natural lordosis was removed. Specimens were placed on a testing device via a load cell. The piston applied loading at the vertex region. Spinal injuries were identified using medical images. Group B tests used the inverted head-cervical column experimental model. In one study, head-T1 specimens were fixed distally, and C7-T1 joints were oriented anteriorly, preserving lordosis. Torso mass of 16 kg was added to the specimen. In another inverted head-cervical column study, occiput-T2 columns were obtained, an artificial head was attached, T1-T2 was fixed, C4-C5 disc was maintained horizontal in the lordosis posture, and C7-T1 was unconstrained. The specimens were attached to the drop test carriage carrying a torso mass of 15 kg. A load cell at the inferior end measured neck loads in both studies. Axial neck force and age were used as the primary response variable and covariate to derive injury probability curves using survival analysis. Group A tests showed that age is a significant (P < .05) and negative covariate; that is, increasing age resulted in decreasing force for the same risk. Injuries were mainly vertebral body fractures and concentrated at one level, mid-to-lower cervical spine, and were attributed to compression-related mechanisms. However, age was not a significant covariate for the combined data from group B tests. Both group B tests produced many soft tissue injuries, at all levels, from C1 to T1. The injury mechanism was attributed to mainly extension. Multiple and noncontiguous injuries occurred

  16. Sustainable Development Mechanism of Food Culture’s Translocal Production Based on Authenticity

    Directory of Open Access Journals (Sweden)

    Guojun Zeng


    Full Text Available Food culture is a kind of non-material culture with authenticity. To achieve sustainable development of translocal heritage and food culture, we must protect its authenticity. By selecting the cases of the Dongbeiren Flavor Dumpling Restaurant and the Daozanjia Northeast Dumpling Restaurant and using the in-depth interview method, this study discusses how northeastern Cuisine in Guangzhou balances the inheritance and innovation of authenticity, how producers and customers negotiate, and how to realize sustainable development. The main conclusions are: first, there are two different paths of translocal food culture production, which are “authentic food culture production” and “differentiated food culture production”. Second, what translocal enterprises produce is not objective authenticity, but constructive authenticity, or even existential authenticity. Third, compared with differentiated food culture production, authentic food culture production is helpful for the sustainable development of local food culture production. It protects the locality while transmitting and developing the local culture. Fourth, translocal food culture production is a process in which the producers and consumers continue to interact to maintain a state of equilibrium, which informs the sustainable development mechanism with a high degree of authenticity.

  17. Application of Combined Sustained and Cyclic Loading Test Results to Alloy 617 Elevated Temperature Design Criteria

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yanli [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jetter, Robert I [Global Egineering and Technology, LLC, Coral Gables, FL (United States); Sham, Sam [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)


    Alloy 617 is a reference structural material for very high temperature components of advanced-gas cooled reactors with outlet temperatures in the range of 900-950°C . In order for designers to be able to use Alloy 617 for these high temperature components, Alloy 617 has to be approved for use in Section III (the nuclear section) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. A plan has been developed to submit a draft code for Alloy 617 to ASME Section III by 2015. However, the current rules in Subsection NH for the evaluation of strain limits and creep-fatigue damage using simplified methods based on elastic analysis have been deemed inappropriate for Alloy 617 at temperatures above 1200°F (650°C). The rationale for this exclusion is that at higher temperatures it is not feasible to decouple plasticity and creep deformation, which is the basis for the current simplified rules. This temperature, 1200 °F, is well below the temperature range of interest for this material in High Temperature Gas Cooled Reactor (HTGR) applications. The only current alternative is, thus, a full inelastic analysis which requires sophisticated material models which have been formulated but not yet verified. To address this issue, proposed code rules have been developed which are based on the use of elastic-perfectly plastic (EPP) analysis methods and which are expected to be applicable to very high temperatures.

  18. Mechanical response of a fibre reinforced earthen material under static and impact loadings (United States)

    Aymerich, Francesco; Fenu, Luigi; Francesconi, Luca; Meloni, Paola


    This study examines the improvements provided by the insertion of hemp fibres with different weight fractions and lengths in an earthen material. The structural response of the materials was investigated by means of static and impact bending tests carried out on notched samples. The main focus of the analyses was in the characterization of the structural properties of the materials in terms of fracture resistance, post-cracking performance and energy absorption capability. The results of the study show that hemp fibres improve significantly the mechanical and fracture properties of the earthen material under both static and dynamic bending. It was also found that the structural properties of unreinforced and reinforced earthen materials are highly sensitive to the stress-rate, with higher strength and fracture resistance under impact loading than under static loading.

  19. Grid Faults Impact on the Mechanical Loads of Active Stall Wind Turbine

    DEFF Research Database (Denmark)

    Iov, Florin; Cutululis, Nicolaos A.; Hansen, Anca D.


    Emphasis in this paper is on the fault ride-through operation impact on the wind turbines structural loads. Grid faults are typically simulated in power system simulation tools using simplified drive train mechanical model, approach which doesn't allow a thorough investigation of structural loads....... This paper presents a two-steps simulation procedure, where two complimentary tools are combined, i.e. power system simulation tool and advanced aeroelastic simulation code. The goal is to investigate the whole integrated wind turbine design and to provide insight both into the structural as well...... as the electrical design of the wind turbine response during grid faults. The two-step simulation procedure is assessed by means of a simulation example. The effect of a grid fault on the structural part of a typical fixed speed wind turbine, equipped with an induction generator, is assessed....

  20. The effects of stoichiometry on the mechanical properties of icosahedral boron carbide under loading. (United States)

    Taylor, DeCarlos E; McCauley, James W; Wright, T W


    The effects of stoichiometry on the atomic structure and the related mechanical properties of boron carbide (B(4)C) have been studied using density functional theory and quantum molecular dynamics simulations. Computational cells of boron carbide containing up to 960 atoms and spanning compositions ranging from 6.7% to 26.7% carbon were used to determine the effects of stoichiometry on the atomic structure, elastic properties, and stress-strain response as a function of hydrostatic, uniaxial, and shear loading paths. It was found that different stoichiometries, as well as variable atomic arrangements within a fixed stoichiometry, can have a significant impact on the yield stress of boron carbide when compressed uniaxially (by as much as 70% in some cases); the significantly reduced strength of boron carbide under shear loading is also demonstrated.


    Directory of Open Access Journals (Sweden)

    Rıza Bayoğlu


    Full Text Available Intramedullary nailing is a widely accepted technique utilized in the treatment of femoral fractures. Design of such devices should be accomplished based on physiological constraints, and loading of the femur, simulating in vivo conditions to prevent bone refracture and implant failure after surgical operation. It has been shown in literature that, walking is the most frequent dynamic activity of a patient, which necessitates testing implants mainly under walking loading conditions. In the present study, the response of the implanted femur having femoral mid-fracture as well as the intact femur were investigated at the instance of maximum hip contact force of the gait cycle in a finite element environment. Displacement and strain distribution on both bone- implant construct and intact bone were presented. The results may lead to an accurate estimation of the implants mechanical behavior in design stage, and be used in fatigue based analyses.

  2. Effects of mechanical loading on the magnetic and dynamic properties of engineering materials (United States)

    Scherthan, L.; Auerbach, H.; Deldar, S.; Jenni, K.; Wolny, J. A.; Herlitschke, M.; Wille, H.-C.; Mutter, A.; Meiser, J.; Umstätter, P.; Urbassek, H. M.; Beck, T.; Smaga, M.; Schünemann, V.


    The influence of strain on the magnetic and dynamic properties of ARMCO iron has been characterized by Mössbauer spectroscopy and by Nuclear Inelastic Scattering of synchrotron radiation. The Mössbauer spectra, taken in backscattering geometry, reveal that the magnetic texture in these materials is depending on the type of mechanical loading, monotonic or cyclic, respectively. The applicability of Nuclear Inelastic Scattering for the investigation of the dynamic properties of these macroscopic bulk-engineering materials is shown. The so obtained phonon density of states of a monotonically loaded specimen shows slight differences in its shape and spectral features in comparison to the initial state. An influence of dislocations is also reflected in theoretically calculated phonon density of states based on classical molecular dynamics simulations.

  3. Cortical bone development under the growth plate is regulated by mechanical load transfer (United States)

    Tanck, E; Hannink, G; Ruimerman, R; Buma, P; Burger, E H; Huiskes, R


    Longitudinal growth of long bones takes place at the growth plates. The growth plate produces new bone trabeculae, which are later resorbed or merged into the cortical shell. This process implies transition of trabecular metaphyseal sections into diaphyseal sections. We hypothesize that the development of cortical bone is governed by mechanical stimuli. We also hypothesize that trabecular and cortical bone share the same regulatory mechanisms for adaptation to mechanical loads. To test these hypotheses, we monitored the development of the tibial cortex in growing pigs, using micro-computer tomography and histology. We then tested the concept that regulatory mechanisms for trabecular bone adaptation can also explain cortical bone development using our mechanical stimulation theory, which could explain trabecular bone (re)modelling. The main results showed that, from the growth plate towards the diaphysis, the pores of the trabecular structure were gradually filled in with bone, which resulted in increased density and cortical bone. The computer model largely predicted this morphological development. We conclude that merging of metaphyseal trabeculae into cortex is likely to be governed by mechanical stimuli. Furthermore, cortex development of growing long bones can be explained as a form of trabecular bone adaptation, without the need for different regulatory mechanisms for cortical and trabecular bone. PMID:16420380

  4. Mechanical impact of incisor loading on the primate midfacial skeleton and its relevance to human evolution. (United States)

    Wang, Qian; Wright, Barth W; Smith, Amanda; Chalk, Janine; Byron, Craig D


    The midfacial skeleton in the human lineage demonstrates a wide spectrum of variation that may be the consequence of different environmental and mechanical selective pressures. However, different facial configurations may develop under comparable selective regimes. For example, the Neanderthal high and projected face and the Inuit broad and flat face are hypothesized to be the consequence of (1) life in a cold climate, and (2) excessive paramasticatory stresses focused on the anterior dentition. In this study, the second of these two hypotheses is tested using finite element analyses of a monkey skull. Results indicate that incisor loading induces heavy stress in the anterior midface of macaques. Additional analyses using incremental increases in the anteroinferior tilt of the skull to simulate different magnitudes of facial projection revealed that comparable muscular force generates less stress in a less-projected face. However, the findings of our final analyses, which attempted to combine biting with the incisors and pulling with the hands, differed from the analyses that mimicked only incisor loading (without any sort of anterior pulling component). These findings suggest that shortening the face may be the most effective way to compensate for anterior dental loading but not necessarily offset the forces incurred when using the anterior dentition as a vice for various paramasticatory behaviors. Although Neanderthals may have frequently loaded their anterior dentition, countervailing selection pressures, such as the inclusion of tough foods in the diet that demanded molar grinding, may have selected for a longer face with a lower load- to lever-arm ratio. (c) 2010 Wiley-Liss, Inc.

  5. Second harmonic generation analysis of early Achilles tendinosis in response to in vivo mechanical loading (United States)


    Background Tenocytes have been implicated in the development of tendinosis, a chronic condition commonly seen in musculoskeletal overuse syndromes. However, the relation between abnormal tenocyte morphology and early changes in the fibrillar collagen matrix has not been closely examined in vivo. Second harmonic generation (SHG) microscopy is a recently developed technique which allows examination of fibrillar collagen structures with a high degree of specificity and resolution. The goal of this study was to examine the potential utility of SHG and multiphoton excitation fluorescence (MPEF) microscopy in understanding the relation between tenocytes and their surrounding collagenous matrix in early tendon overuse lesions. Methods Histological preparations of tendon were prepared from adult male Sprague-Dawley rats subjected to an Achilles tendon loading protocol for 12 weeks (Rat-A-PED), or from sedentary age-matched cage controls. Second harmonic generation and multiphoton excitation fluorescence were performed simultaneously on these tissue sections in at least three different areas. Results SHG microscopy revealed an association between abnormal tenocyte morphology and morphological changes in the fibrillar collagen matrix of mechanically loaded Achilles tendons. Collagen density and organization was significantly reduced in focal micro-regions of mechanically loaded tendons. These pathological changes occurred specifically in association with altered tenocyte morphology. Normal tendons displayed a regular distribution of fibre bundles, and the average size of these bundles as determined by Gaussian analysis was 0.47 μm ± 0.02. In comparison, fibre bundle measures from tendon regions in the vicinity of abnormal tenocytes could not be quantified due to a reduction in their regularity of distribution and orientation. Conclusions SHG microscopy allowed high resolution detection of focal tendon abnormalities affecting the fibrillar collagen matrix. With ongoing

  6. Second harmonic generation analysis of early Achilles tendinosis in response to in vivo mechanical loading

    Directory of Open Access Journals (Sweden)

    Fong Gloria


    Full Text Available Abstract Background Tenocytes have been implicated in the development of tendinosis, a chronic condition commonly seen in musculoskeletal overuse syndromes. However, the relation between abnormal tenocyte morphology and early changes in the fibrillar collagen matrix has not been closely examined in vivo. Second harmonic generation (SHG microscopy is a recently developed technique which allows examination of fibrillar collagen structures with a high degree of specificity and resolution. The goal of this study was to examine the potential utility of SHG and multiphoton excitation fluorescence (MPEF microscopy in understanding the relation between tenocytes and their surrounding collagenous matrix in early tendon overuse lesions. Methods Histological preparations of tendon were prepared from adult male Sprague-Dawley rats subjected to an Achilles tendon loading protocol for 12 weeks (Rat-A-PED, or from sedentary age-matched cage controls. Second harmonic generation and multiphoton excitation fluorescence were performed simultaneously on these tissue sections in at least three different areas. Results SHG microscopy revealed an association between abnormal tenocyte morphology and morphological changes in the fibrillar collagen matrix of mechanically loaded Achilles tendons. Collagen density and organization was significantly reduced in focal micro-regions of mechanically loaded tendons. These pathological changes occurred specifically in association with altered tenocyte morphology. Normal tendons displayed a regular distribution of fibre bundles, and the average size of these bundles as determined by Gaussian analysis was 0.47 μm ± 0.02. In comparison, fibre bundle measures from tendon regions in the vicinity of abnormal tenocytes could not be quantified due to a reduction in their regularity of distribution and orientation. Conclusions SHG microscopy allowed high resolution detection of focal tendon abnormalities affecting the fibrillar collagen

  7. A Low Protein Diet Alters Bone Material Level Properties and the Response to In Vitro Repeated Mechanical Loading

    Directory of Open Access Journals (Sweden)

    Victor Dubois-Ferrière


    Full Text Available Low protein intake is associated with an alteration of bone microstructure and material level properties. However, it remains unknown whether these alterations of bone tissue could influence the response to repeated mechanical loading. The authors investigated the in vitro effect of repeated loading on bone strength in humeri collected from 20 6-month-old female rats pair-fed with a control (15% casein or an isocaloric low protein (2.5% casein diet for 10 weeks. Bone specimens were cyclically loaded in three-point bending under load control for 2000 cycles. Humeri were then monotonically loaded to failure. The load-displacement curve of the in vitro cyclically loaded humerus was compared to the contralateral noncyclically loaded humerus and the influence of both protein diets. Material level properties were also evaluated through a nanoindentation test. Cyclic loading decreased postyield load and plastic deflection in rats fed a low protein diet, but not in those on a regular diet. Bone material level properties were altered in rats fed a low protein diet. This suggests that bone biomechanical alterations consequent to cyclic loading are more likely to occur in rats fed a low protein diet than in control animals subjected to the same in vitro cyclic loading regimen.

  8. Improved Mechanical Properties and Sustained Release Behavior of Cationic Cellulose Nanocrystals Reinforeced Cationic Cellulose Injectable Hydrogels. (United States)

    You, Jun; Cao, Jinfeng; Zhao, Yanteng; Zhang, Lina; Zhou, Jinping; Chen, Yun


    Polysaccharide-based injectable hydrogels have several advantages in the context of biomedical use. However, the main obstruction associated with the utilization of these hydrogels in clinical application is their poor mechanical properties. Herein, we describe in situ gelling of nanocomposite hydrogels based on quaternized cellulose (QC) and rigid rod-like cationic cellulose nanocrystals (CCNCs), which can overcome this challenge. In all cases, gelation immediately occurred with an increase of temperature, and the CCNCs were evenly distributed throughout the hydrogels. The nanocomposite hydrogels exhibited increasing orders-of-magnitude in the mechanical strength, high extension in degradation and the sustained release time, because of the strong interaction between CCNCs and QC chains mediated by the cross-linking agent (β-glycerophosphate, β-GP). The results of the in vitro toxicity and in vivo biocompatibility tests revealed that the hydrogels did not show obvious cytotoxicity and inflammatory reaction to cells and tissue. Moreover, DOX-encapsulated hydrogels were injected beside the tumors of mice bearing liver cancer xenografts to assess the potential utility as localized and sustained drug delivery depot systems for anticancer therapy. The results suggested that the QC/CCNC/β-GP nanocomposite hydrogels had great potential for application in subcutaneous and sustained delivery of anticancer drug to increase therapeutic efficacy and improve patient compliance.

  9. Improving environmental sustainability of concrete products: Investigation on MWC thermal and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Becchio, Cristina; Corgnati, Stefano Paolo; Kindinis, Andrea [Department of Energetics (DENER), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Pagliolico, Simonetta [Department of Materials Science and Engineering Chemistry (DISMIC), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)


    This research focuses on the possibility of constituting a more sustainable lightweight concrete, Mineralized Wood Concrete (MWC), substituting natural aggregates with wastes from woodworking activities. Exploiting this type of aggregates, a triple purpose has been achieved: preservation of natural raw materials, reuse of wastes and energy saving. Furthermore, the use of wood aggregates is a way to try to develop a sustainable concrete characterized by high thermal inertia, high thermal resistance and low weight. In this paper, effects of the addition of wood aggregates on mechanical and thermal properties of concrete are studied. Mechanical performances have been investigated with compressive strength tests, while a one-dimensional heat flow model has been used to predict the thermal conductivity of MWC. The use of MWC can be associated with the idea of a different typology of relatively heavy building envelope: this union could competitively answer to the demand of well-insulated building envelope and concurrently characterized by high thermal mass. From this union, a series of other values can be derived: low weight, environmentally friendly, easily industrialized and easy on-site casting. Consequently, applications of wood concrete in building constructions may be an interesting solution in order to improve sustainability and building energy efficiency. (author)

  10. Fracture Mechanics Analyses of Subsurface Defects in Reinforced Carbon-Carbon Joggles Subjected to Thermo-Mechanical Loads (United States)

    Knight, Norman F., Jr.; Raju, Ivatury S.; Song, Kyongchan


    Coating spallation events have been observed along the slip-side joggle region of the Space Shuttle Orbiter wing-leading-edge panels. One potential contributor to the spallation event is a pressure build up within subsurface voids or defects due to volatiles or water vapor entrapped during fabrication, refurbishment, or normal operational use. The influence of entrapped pressure on the thermo-mechanical fracture-mechanics response of reinforced carbon-carbon with subsurface defects is studied. Plane-strain simulations with embedded subsurface defects are performed to characterize the fracture mechanics response for a given defect length when subjected to combined elevated-temperature and subsurface-defect pressure loadings to simulate the unvented defect condition. Various subsurface defect locations of a fixed-length substrate defect are examined for elevated temperature conditions. Fracture mechanics results suggest that entrapped pressure combined with local elevated temperatures have the potential to cause subsurface defect growth and possibly contribute to further material separation or even spallation. For this anomaly to occur, several unusual circumstances would be required making such an outcome unlikely but plausible.

  11. The seating mechanics of head-neck modular tapers in vitro: Load-displacement measurements, moisture, and rate effects. (United States)

    Ouellette, Eric S; Shenoy, Aarti A; Gilbert, Jeremy L


    The mechanically-assisted crevice corrosion performance of head-neck modular tapers is a significant concern in orthopedic biomaterials. Fretting crevice corrosion processes in modular tapers are thought to be influenced by a wide array of factors including seating mechanics of the junction, hence there is a need for in vitro test methods that can assess their performance. This study presented a test method to directly measure the load-displacement seating mechanics of modular tapers and used this method to compare the seating mechanics for different tapers, moisture, seating loads and seating rates. Seating mechanics were explored whereby the instantaneous load-displacement behavior of the head seating onto the neck is captured and used to define the mechanics of seating. Two distinct taper design/material combinations were assembled wet or dry using axially applied loads (500, 1000, 2000 and 4000 N) at two loading rates of 100 and 104  N/s (n = 5 for each condition) using a servohydraulic test frame. The results showed that pull-off strength scaled with seating load and ranged between 43-68% of seating load depending on sample and wetness. Tapers seated wet had higher pull-off strengths (2200 N +/- 300 N) than those seated dry (1800 N +/- 200 N, P mechanics (load-displacement plots) varied due to sample type and due to wetness with differences in seating energy, seating stiffness and seating displacement. These results show the detailed mechanics of seating during assembly and provide significant insight into the complex interplay of factors associated with even "ideal" seating (axial, quasistatic) loading. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  12. Exploring mechanisms for mobilising industrial sustainability models across different industrial locations

    DEFF Research Database (Denmark)

    Jacobsen, Ole Morten Noel Brings


    Industrial symbiosis is a model of sustainability which suggests that agglomerations of industries can achieve considerable environmental benefits by engaging in inter-organisational waste recycling, energy cascading and water recovery. This article considers how such a complex inter......-organisational model for environmental management can be mobilised across different industrial localities. It is suggested that companies engaged in industrial symbiosis activities at one production locality may be more inclined to engage in symbiotic activities when entering a new production locality. The industrial...... symbiosis model may in this way be mobilised across industrial localities as part of the global corporate search for marked access and cost reductions. This suggestion is supported by an illustrative case study shedding some light on the mechanisms for mobilising sustainability models across localities....

  13. A mechanism for sustained groundwater pressure changes induced by distant earthquakes (United States)

    Brodsky, E.E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.


    Large sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 ?? 10-2 MPa pressure changes and triggered seismicity.

  14. Using the Enhanced Daily Load Stimulus Model to Quantify the Mechanical Load and Bone Mineral Density Changes Experienced by Crew Members on the International Space Station (United States)

    Genc, K. O.; Gopalakrishnan, R.; Kuklis, M. M.; Maender, C. C.; Rice, A. J.; Cavanagh, P. R.


    Despite the use of exercise countermeasures during long-duration space missions, bone mineral density (BMD) and predicted bone strength of astronauts continue to show decreases in the lower extremities and spine. This site-specific bone adaptation is most likely caused by the effects of microgravity on the mechanical loading environment of the crew member. There is, therefore, a need to quantify the mechanical loading experienced on Earth and on-orbit to define the effect of a given "dose" of loading on bone homeostasis. Gene et al. recently proposed an enhanced DLS (EDLS) model that, when used with entire days of in-shoe forces, takes into account recently developed theories on the importance of factors such as saturation, recovery, and standing and their effects on the osteogenic response of bone to daily physical activity. This algorithm can also quantify the tinting and type of activity (sit/unload, stand, walk, run or other loaded activity) performed throughout the day. The purpose of the current study was to use in-shoe force measurements from entire typical work days on Earth and on-orbit in order to quantify the type and amount of loading experienced by crew members. The specific aim was to use these measurements as inputs into the EDLS model to determine activity timing/type and the mechanical "dose" imparted on the musculoskeletal system of crew members and relate this dose to changes in bone homeostasis.

  15. The Effect of Kettlebell Swing Load and Cadence on Physiological, Perceptual and Mechanical Variables


    Michael J. Duncan; Rosanna Gibbard; Leanne M. Raymond; Peter Mundy


    This study compared the physiological, perceptual and mechanical responses to kettlebell swings at different loads and swing speeds. Following familiarization 16 strength trained participants (10 males, six females, mean age ± SD = 23 ± 2.9) performed four trials: 2 min kettlebell swings with an 8 kg kettlebell at a fast cadence; 2 min kettlebell swings with an 8 kg kettlebell at a slow cadence; 4 min kettlebell swings with a 4 kg kettlebell at a fast cadence; 4 min kettlebell swings with a 4...

  16. Properties and Semicrystalline Structure Evolution of Polypropylene/Montmorillonite Nanocomposites under Mechanical Load

    DEFF Research Database (Denmark)

    Stribeck, Norbert; Zeinolebadi, Ahmad; Ganjaee Sari, Morteza


    Small-angle X-ray scattering (SAXS) monitors tensile and load-cycling tests of metallocene isotactic polypropylene (PP), a blend of PP and montmorillonite (MMT), and two block copolymer compatibilized PP/MMT nanocomposites. Mechanical properties of the materials are similar, but the semicrystalline...... materials fatigue. Lifetimes describe the reinforcing and weakening effects. Addition of 3% MMT halves the fortifying effect of the PP nanostructure. A net gain of reinforcement (11%) is observed with the highly compatibilized composite in which the strength of the semicrystalline PP is reduced to 25...

  17. Mechanically Reconfigurable Microstrip Lines Loaded with Stepped Impedance Resonators and Potential Applications

    Directory of Open Access Journals (Sweden)

    J. Naqui


    Full Text Available This paper is focused on exploring the possibilities and potential applications of microstrip transmission lines loaded with stepped impedance resonators (SIRs etched on top of the signal strip, in a separated substrate. It is shown that if the symmetry plane of the line (a magnetic wall is perfectly aligned with the electric wall of the SIR at the fundamental resonance, the line is transparent. However, if symmetry is somehow ruptured, a notch in the transmission coefficient appears. The notch frequency and depth can thus be mechanically controlled, and this property can be of interest for the implementation of sensors and barcodes, as it is discussed.

  18. Effect of Starch Loading on the Thermo-Mechanical and Morphological Properties of Polyurethane Composites (United States)

    Gaaz, Tayser Sumer; Sulong, Abu Bakar; Ansari, M. N. M.; Kadhum, Abdul Amir H.; Nassir, Mohamed H.


    The advancements in material science and technology have made polyurethane (PU) one of the most important renewable polymers. Enhancing the physio-chemical and mechanical properties of PU has become the theme of this and many other studies. One of these enhancements was carried out by adding starch to PU to form new renewable materials called polyurethane-starch composites (PUS). In this study, PUS composites are prepared by adding starch at 0.5, 1.0, 1.5, and 2.0 wt.% to a PU matrix. The mechanical, thermal, and morphological properties of PU and PUS composites were investigated. Scanning electron microscope (SEM) images of PU and PUS fractured surfaces show cracks and agglomeration in PUS at 1.5 wt.% starch. The thermo-mechanical properties of the PUS composites were improved as starch content increased to 1.5 wt.% and declined by more starch loading. Despite this reduction, the mechanical properties were still better than that of neat PU. The mechanical strength increased as starch content increased to 1.5 wt.%. The tensile, flexural, and impact strengths of the PUS composites were found to be 9.62 MPa, 126.04 MPa, and 12.87 × 10−3 J/mm2, respectively, at 1.5 wt.% starch. Thermal studies showed that the thermal stability and crystallization temperature of the PUS composites increased compared to that of PU. The loss modulus curves showed that neat PU crystallizes at 124 °C and at 127 °C for PUS-0.5 wt.% and rises with increasing loading from 0.5 to 2 wt.%. PMID:28773134

  19. Effect of Starch Loading on the Thermo-Mechanical and Morphological Properties of Polyurethane Composites. (United States)

    Gaaz, Tayser Sumer; Sulong, Abu Bakar; Ansari, M N M; Kadhum, Abdul Amir H; Al-Amiery, Ahmed A; Nassir, Mohamed H


    The advancements in material science and technology have made polyurethane (PU) one of the most important renewable polymers. Enhancing the physio-chemical and mechanical properties of PU has become the theme of this and many other studies. One of these enhancements was carried out by adding starch to PU to form new renewable materials called polyurethane-starch composites (PUS). In this study, PUS composites are prepared by adding starch at 0.5, 1.0, 1.5, and 2.0 wt.% to a PU matrix. The mechanical, thermal, and morphological properties of PU and PUS composites were investigated. Scanning electron microscope (SEM) images of PU and PUS fractured surfaces show cracks and agglomeration in PUS at 1.5 wt.% starch. The thermo-mechanical properties of the PUS composites were improved as starch content increased to 1.5 wt.% and declined by more starch loading. Despite this reduction, the mechanical properties were still better than that of neat PU. The mechanical strength increased as starch content increased to 1.5 wt.%. The tensile, flexural, and impact strengths of the PUS composites were found to be 9.62 MPa, 126.04 MPa, and 12.87 × 10-3 J/mm², respectively, at 1.5 wt.% starch. Thermal studies showed that the thermal stability and crystallization temperature of the PUS composites increased compared to that of PU. The loss modulus curves showed that neat PU crystallizes at 124 °C and at 127 °C for PUS-0.5 wt.% and rises with increasing loading from 0.5 to 2 wt.%.

  20. On the relative significance of lithospheric weakening mechanisms for sustained plate tectonics (United States)

    Araceli Sanchez-Maes, Sophia


    Plate tectonics requires the bending of strong plates at subduction zones, which is difficult to achieve without a secondary weakening mechanism. Two classes of weakening mechanisms have been proposed for the generation of ongoing plate tectonics, distinguished by whether or not they require water. Here we show that the energy budget of global subduction zones offers a simple yet decisive test on their relative significance. Theoretical studies of mantle convection suggest bending dissipation to occupy only 10-20 % of total dissipation in the mantle, and our results indicate that the hydrous mechanism in the shallow part of plates is essential to satisfy the requirement. Thus, surface oceans are required for the long-term operation of plate tectonics on terrestrial worlds. Establishing this necessary and observable condition for sustained plate tectonics carries important implications for planetary habitability at large.

  1. Sustainability of Recycled ABS and PA6 by Banana Fiber Reinforcement: Thermal, Mechanical and Morphological Properties (United States)

    Singh, Rupinder; Kumar, Ranvijay; Ranjan, Nishant


    In the present study efforts have been made to prepare functional prototypes with improved thermal, mechanical and morphological properties from polymeric waste for sustainability. The primary recycled acrylonitrile butadiene styrene (ABS) and polyamide 6 (PA6) has been selected as matrix material with bio-degradable and bio-compatible banana fibers (BF) as reinforcement. The blend (in form of feed stock filament wire) of ABS/PA6 and BF was prepared in house by conventional twin screw extrusion (TSE) process. Finally feed stock filament of ABS/PA6 reinforced with BF was put to run on open source fused deposition modelling based three dimensional printer (without any change in hardware/software of the system) for printing of functional prototypes with improved thermal/mechanical/morphological properties. The results are supported by photomicrographs, thermographs and mechanical testing.

  2. Design and validation of a bi-axial loading bioreactor for mechanical stimulation of engineered cartilage. (United States)

    Yusoff, Norwahida; Abu Osman, Noor Azuan; Pingguan-Murphy, Belinda


    A mechanical-conditioning bioreactor has been developed to provide bi-axial loading to three-dimensional (3D) tissue constructs within a highly controlled environment. The computer-controlled bioreactor is capable of applying axial compressive and shear deformations, individually or simultaneously at various regimes of strain and frequency. The reliability and reproducibility of the system were verified through validation of the spatial and temporal accuracy of platen movement, which was maintained over the operating length of the system. In the presence of actual specimens, the system was verified to be able to deliver precise bi-axial load to the specimens, in which the deformation of every specimen was observed to be relatively homogeneous. The primary use of the bioreactor is in the culture of chondrocytes seeded within an agarose hydrogel while subjected to physiological compressive and shear deformation. The system has been designed specifically to permit the repeatable quantification and characterisation of the biosynthetic activity of cells in response to a wide range of short and long term multi-dimensional loading regimes. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  3. Regulation of high mobility group box protein 1 expression following mechanical loading by orthodontic forces in vitro and in vivo

    National Research Council Canada - National Science Library

    Wolf, Michael; Lossdörfer, Stefan; Küpper, Katharina; Jäger, Andreas


    ...) cells challenged by mechanical loading similar to force levels being applied in orthodontic treatment in vitro and to transfer these findings to an in vivo microenvironment in an animal model of tooth movement in rats...

  4. Influence of boehmite nanoparticle loading on the mechanical, thermal, and rheological properties of biodegradable polylactide/ poly(e-caprolactone) blends

    CSIR Research Space (South Africa)

    Agwuncha, SC


    Full Text Available -1 Macromolecular Materials and Engineering Vol. 300(1), 31-47 Influence of Boehmite Nanoparticle Loading on the Mechanical, Thermal, and Rheological Properties of Biodegradable Polylactide/Poly(e-caprolactone) Blendsa Stephen C. Agwuncha, Suprakas Sinha...

  5. Mechanization of Conservation Agriculture for Smallholders: Issues and Options for Sustainable Intensification

    Directory of Open Access Journals (Sweden)

    Brian Sims


    Full Text Available Conservation agriculture (CA is an increasingly adopted production system to meet the goals of sustainable crop production intensification in feeding a growing world population whilst conserving natural resources. Mechanization (especially power units, seeders, rippers and sprayers is a key input for CA and smallholder farmers often have difficulties in making the necessary investments. Donors may be able to provide mechanization inputs in the short term, but this is not a sustainable solution as a machinery input supply chain needs to be built up to continue availability after external interventions cease. Local manufacture should be supported, as was the case in Brazil, but this is a slow development process, especially in sub-Saharan Africa. A more immediate solution is to equip and train CA service provision entrepreneurs. With the right equipment, selected for the needs of their local clientele, and the right technical and business management training, such entrepreneurs can make a livelihood by supplying high quality CA and other mechanization services on a fully costed basis. Elements of the required training, based on extensive field experience, are provided. To catalyse the growth of CA providers’ business, the market can be stimulated for an initial period by issuing e-vouchers for services and inputs.

  6. Mechanically corrected EMG for the continuous estimation of erector spinae muscle loading during repetitive lifting. (United States)

    Potvin, J R; Norman, R W; McGill, S M


    Few studies have been carried out on the changes in biomechanical loading on low-back tissues during prolonged lifting. The purpose of this paper was to develop a model for continuously estimating erector spinae muscle loads during repetitive lifting and lowering tasks. The model was based on spine kinematics and bilateral lumbar and thoracic erector spinae electromyogram (EMG) signals and was developed with the data from eight male subjects. Each subject performed a series of isometric contractions to develop extensor moments about the low back. Maximum voluntary contractions (MVCs) were used to normalize all recorded EMG and moment time-histories. Ramp contractions were used to determine the non-linear relationship between extensor moments and EMG amplitudes. In addition, the most appropriate low-pass filter cut-off frequencies were calculated for matching the rectified EMG signals with the moment patterns. The mean low-pass cut-off frequency was 2.7 (0.4) Hz. The accuracy of the non-linear EMG-based estimates of isometric extensor moment were tested with data from a series of six rapid contractions by each subject. The mean error over the duration of these contractions was 9.2 (2.6)% MVC. During prolonged lifting sessions of 20 min and of 2 h, a model was used to calculate changes in muscle length based on monitored spine kinematics. EMG signals were first processed according to the parameters determined from the isometric contractions and then further processed to account for the effects of instantaneous muscle length and velocity. Simple EMG estimates were found to underestimate peak loading by 9.1 (4.0) and 25.7 (11.6)% MVC for eccentric and concentric phases of lifting respectively, when compared to load estimates based on the mechanically corrected EMG. To date, the model has been used to analyze over 5300 lifts.

  7. Outperforming hummingbirds' load-lifting capability with a lightweight hummingbird-like flapping-wing mechanism. (United States)

    Leys, Frederik; Reynaerts, Dominiek; Vandepitte, Dirk


    The stroke-cam flapping mechanism presented in this paper closely mimics the wing motion of a hovering Rufous hummingbird. It is the only lightweight hummingbird-sized flapping mechanism which generates a harmonic wing stroke with both a high flapping frequency and a large stroke amplitude. Experiments on a lightweight prototype of this stroke-cam mechanism on a 50 mm-long wing demonstrate that a harmonic stroke motion is generated with a peak-to-peak stroke amplitude of 175° at a flapping frequency of 40 Hz. It generated a mass lifting capability of 5.1 g, which is largely sufficient to lift the prototype's mass of 3.39 g and larger than the mass-lifting capability of a Rufous hummingbird. The motor mass of a hummingbird-like robot which drives the stroke-cam mechanism is considerably larger (about five times) than the muscle mass of a hummingbird with comparable load-lifting capability. This paper presents a flapping wing nano aerial vehicle which is designed to possess the same lift- and thrust-generating principles of the Rufous hummingbird. The application is indoor flight. We give an overview of the wing kinematics and some specifications which should be met to develop an artificial wing, and also describe the applications of these in the mechanism which has been developed in this work. © 2016. Published by The Company of Biologists Ltd.

  8. Outperforming hummingbirds’ load-lifting capability with a lightweight hummingbird-like flapping-wing mechanism

    Directory of Open Access Journals (Sweden)

    Frederik Leys


    Full Text Available The stroke-cam flapping mechanism presented in this paper closely mimics the wing motion of a hovering Rufous hummingbird. It is the only lightweight hummingbird-sized flapping mechanism which generates a harmonic wing stroke with both a high flapping frequency and a large stroke amplitude. Experiments on a lightweight prototype of this stroke-cam mechanism on a 50 mm-long wing demonstrate that a harmonic stroke motion is generated with a peak-to-peak stroke amplitude of 175° at a flapping frequency of 40 Hz. It generated a mass lifting capability of 5.1 g, which is largely sufficient to lift the prototype's mass of 3.39 g and larger than the mass-lifting capability of a Rufous hummingbird. The motor mass of a hummingbird-like robot which drives the stroke-cam mechanism is considerably larger (about five times than the muscle mass of a hummingbird with comparable load-lifting capability. This paper presents a flapping wing nano aerial vehicle which is designed to possess the same lift- and thrust-generating principles of the Rufous hummingbird. The application is indoor flight. We give an overview of the wing kinematics and some specifications which should be met to develop an artificial wing, and also describe the applications of these in the mechanism which has been developed in this work.


    Directory of Open Access Journals (Sweden)

    A. D. Bobryshev


    Full Text Available Experience available for practical implementation of anti-crisis company (particularly industrial enterprise management methods under conditions of proceeding destruction of scientifi c and technical potential of the country proves their ineff ectiveness, so other theoretical and practical solutions capable of changing the situation are to be searched. In this respect, creation of an organizational mechanism for a company to function sustainably through minimization of the infl uence of crisis phenomena consequences on activities of the company seems to have good prospects.

  10. Failure mechanism and coupled static-dynamic loading theory in deep hard rock mining: A review

    Directory of Open Access Journals (Sweden)

    Xibing Li


    Full Text Available Rock failure phenomena, such as rockburst, slabbing (or spalling and zonal disintegration, related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining. Currently, the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward. In this study, new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced. Two types of coupled loading modes, i.e. “critical static stress + slight disturbance” and “elastic static stress + impact disturbance”, are proposed, and associated test devices are developed. Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory, and the rockburst mechanism and related criteria are demonstrated. The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold, and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion. Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density. In addition, we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass, which can efficiently and accurately locate the rock failure in hard rock mines. Also, a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.

  11. Effect of thermo-mechanical loading on marginal quality and wear of primary molar crowns. (United States)

    Krämer, N; Rudolph, H; Garcia-Godoy, F; Frankenberger, R


    To evaluate the effect of thermo-mechanical loading (TML) on marginal quality and wear of different crown types for primary molars. Eighty extracted human primary molars were used. After preparation, five groups received different crowns (n=16): preformed metal crowns (3M ESPE) and NuSmile crowns (Orthodontic Technologies Inc.) were inserted as preformed metal crowns; as semi-preformed crowns Protemp crowns (3M ESPE) were luted; and as individually manufactured resin composite crowns Filtek Z250 (3M ESPE) and Heliomolar (Ivoclar Vivadent) were used. Specimens were subjected to 2,500 thermal cycles between 5-55(o)C and chewing simulation for 100,000 cycles at 50N at a frequency of 0.5 Hz. Before and after thermo-mechanical loading, impressions of the teeth were taken and replicas were made. The replicas received marginal quality evaluation under a SEM at x200 magnification. Occlusal wear was measured as vertical height loss using a 3-D laser scanning microscope. After TML, all crowns were intact. The adhesively bonded crowns showed significantly better marginal quality to dentine/cementum compared with GIC luted crowns (pcrowns showed a good fit and nearly transition-free margins also after TML. Preformed metal crowns showed the significantly lowest wear rates compared to the resin composites (pcrown types under investigation showed a good performance concerning the evaluated parameters marginal quality and wear.

  12. Mix design and mechanical performance of geopolymer binder for sustainable construction and building material (United States)

    Saeli, Manfredi; Novais, Rui M.; Seabra, Maria Paula; Labrincha, João A.


    Sustainability in construction is a major concern worldwide, due to the huge volume of materials and energy consumed by this sector. Associated supplementing industries (e.g. Portland cement production) constitute a significant source of CO2 emissions and global warming. Valorisation and reuse of industrial wastes and by-products make geopolymers a solid and sustainable via to be followed as a valid alternative to Portland cement. In this work the mix design of a green fly ash-based geopolymer is evaluated as an environmentally friendly construction material. In the pursuit of sustainability, wastes from a regional kraft pulp industry are exploited for the material processing. Furthermore, a simple, reproducible, and low-cost manufacture is used. The mix design is hence optimised in order to improve the desirable mechanical performance of the material intended for structural applications in construction. Tests indicate that geopolymers may efficiently substitute the ordinary Portland cement as a mortar/concrete binder. Furthermore, valorisation and reuse of wastes in geopolymers is a suboptimal way of gaining financial surplus for the involved industrial players, while contributes for the implementation of a desirable circular economy.

  13. Mathematical modeling of sustainable synaptogenesis by repetitive stimuli suggests signaling mechanisms in vivo.

    Directory of Open Access Journals (Sweden)

    Hiromu Takizawa

    Full Text Available The mechanisms of long-term synaptic maintenance are a key component to understanding the mechanism of long-term memory. From biological experiments, a hypothesis arose that repetitive stimuli with appropriate intervals are essential to maintain new synapses for periods of longer than a few days. We successfully reproduce the time-course of relative numbers of synapses with our mathematical model in the same conditions as biological experiments, which used Adenosine-3', 5'-cyclic monophosphorothioate, Sp-isomer (Sp-cAMPS as external stimuli. We also reproduce synaptic maintenance responsiveness to intervals of Sp-cAMPS treatment accompanied by PKA activation. The model suggests a possible mechanism of sustainable synaptogenesis which consists of two steps. First, the signal transduction from an external stimulus triggers the synthesis of a new signaling protein. Second, the new signaling protein is required for the next signal transduction with the same stimuli. As a result, the network component is modified from the first network, and a different signal is transferred which triggers the synthesis of another new signaling molecule. We refer to this hypothetical mechanism as network succession. We build our model on the basis of two hypotheses: (1 a multi-step network succession induces downregulation of SSH and COFILIN gene expression, which triggers the production of stable F-actin; (2 the formation of a complex of stable F-actin with Drebrin at PSD is the critical mechanism to achieve long-term synaptic maintenance. Our simulation shows that a three-step network succession is sufficient to reproduce sustainable synapses for a period longer than 14 days. When we change the network structure to a single step network, the model fails to follow the exact condition of repetitive signals to reproduce a sufficient number of synapses. Another advantage of the three-step network succession is that this system indicates a greater tolerance of parameter

  14. Silver nanoparticles-loaded activated carbon fibers using chitosan as binding agent: Preparation, mechanism, and their antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Chengli, E-mail: [College of Mechanical and Electrical Engineering, Jiaxing University, Jiaxing 314001 (China); Hu, Dongmei [College of Mechanical Science and Engineering, Jilin University, Changchun 130022 (China); Cao, Qianqian [College of Mechanical and Electrical Engineering, Jiaxing University, Jiaxing 314001 (China); Yan, Wei [Department of Environmental Science and Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Xing, Bo [College of Mechanical and Electrical Engineering, Jiaxing University, Jiaxing 314001 (China)


    Highlights: • Chitosan was firstly introduced as binding agent for AgNPs loading on ACF surface. • Molecular dynamics simulation was used to explore the AgNPs loading mechanism. • Loading mechanism was proposed based on the experimental and simulation results. • Antibacterial AgNPs-loaded ACF showed use potential for water disinfection. - Abstract: The effective and strong adherence of silver nanoparticles (AgNPs) to the substrate surface is pivotal to the practical application of those AgNPs-modified materials. In this work, AgNPs were synthesized through a green and facile hydrothermal method. Chitosan was introduced as the binding agent for the effective loading of AgNPs on activated carbon fibers (ACF) surface to fabricate the antibacterial material. Apart from conventional instrumental characterizations, i. e., scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), zeta potential and Brunauer-Emmett-Teller (BET) surface area measurement, molecular dynamics simulation method was also applied to explore the loading mechanism of AgNPs on the ACF surface. The AgNPs-loaded ACF material showed outstanding antibacterial activity for S. aureus and E. coli. The combination of experimental and theoretical calculation results proved chitosan to be a promising binding agent for the fabrication of AgNPs-loaded ACF material with excellent antibacterial activity.

  15. Poly(ε-caprolactone)/triclosan loaded polylactic acid nanoparticles composite: A long-term antibacterial bionanocomposite with sustained release. (United States)

    Kaffashi, Babak; Davoodi, Saeed; Oliaei, Erfan


    In this study, the antibacterial bionanocomposites of poly(ε-caprolactone) (PCL) with different concentrations of triclosan (TC) loaded polylactic acid (PLA) nanoparticles (30wt% triclosan) (LATC30) were fabricated via a melt mixing process in order to lower the burst release of PCL and to extend the antibacterial activity during its performance. Due to the PLA's higher glass transition temperature (Tg) and less flexibility compared with PCL; the PLA nanoparticles efficiently trapped the TC particles, reduced the burst release of TC from the bionanocomposites; and extended the antibacterial property of the samples up to two years. The melt mixing temperature was adjusted to a temperature lower than the melting point of LATC30 nanoparticles; therefore, these nanoparticles were dispersed in the PCL matrix without any chemical reaction and/or drug extraction. The sustained release behavior of TC from PCL remained unchanged since no significant changes occurred in the samples' crystallinity compared with that in the neat PCL. The elastic moduli of samples were enhanced once LATC30 is included. This is necessary since the elastic modulus is decreased with water absorption. The rheological behaviors of samples showed appropriate properties for melt electro-spinning. A stable process was established as the relaxation time of the bionanocomposites was increased. The hydrophilic properties of samples were increased with increasing LATC30. The proliferation rate of the fibroblast (L929) cells was enhanced as the content of nanoparticles was increased. A system similar to this could be implemented to prepare long-term antibacterial and drug delivery systems based on PCL and various low molecular weight drugs. The prepared bionanocomposites are considered as candidates for the soft connective tissue engineering and long-term drug delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. [Low back load reduction using mechanical lift during transfer of patients]. (United States)

    Tomioka, Kimiko; Sakae, Kenichiro; Yasuda, Junko


    In Japanese care-work sites, care-workers (CWs) have lacked basic health risk awareness for transferring patients. Knowledge of lifting equipment and skills for transfer of patients have not been disseminated and many CWs have suffered from work-related musculoskeletal disorders, especially low back pain (LBP). In order to find better ways of patient transfer which reduce and prevent LBP, we conducted a study of low back loads and operation time during the transfer of a simulated patient, who was totally dependent from bed to wheelchair, using a mechanical lift (Lift) and manual handling (handling). Moreover we examined the levels of skill which CWs had acquired in transfer by Lift and the effects of acquired skill on low back loads and operation time. We explored low back load using surface electromyography (EMG) of the lumbar paraspinals between L3 and L4 and the trunk inclination angle (TIA) measurement method. The subjects were 5 caregivers who performed the task of transferring a simulated patient from lying on the bed to sitting in a wheelchair using the Lift and by handling. Handling transfer was assisted by two-persons at the head and foot. A 'simulated' patient (a 70 kg healthy male; instructed to keep whole body relaxed) was used in all transfer tasks. When subjects used the Lift, we made an ergonomics checklist for reduction of low back load of caregivers. Subjects performed the task 4 times and were evaluated with the checklist. The level of acquired skill was significantly improved by the guidance of the checklist. TIA was observed to be significantly lower in Lift than in handling, but with EMG no significant differences were seen between Lift and handling. The effects of acquired skill on low back loads showed that TIA was statistically reduced at high skill as compared to low skill. However, there were no significant differences between both skills in Lift and handling by EMG. Operation time of Lift showed significant shortening of operation time

  17. Soil memory as a potential mechanism for encouraging sustainable plant health and productivity. (United States)

    Lapsansky, Erin R; Milroy, Arwen M; Andales, Marie J; Vivanco, Jorge M


    The unspecified components of plant-microbe and plant-microbiome associations in the rhizosphere are complex, but recent research is simplifying our understanding of these relationships. We propose that the strong association between hosts, symbionts, and pathogens could be simplified by the concept of soil memory, which explains how a plant could promote their fecundity and protect their offspring through tightly associated relationships with the soil. Although there are many questions surrounding the mechanisms of this phenomenon, recent research has exposed evidence of its existence. Along with evidence from observations and mechanisms related to soil memory, we report means to utilize our understanding as sustainable protection for agricultural crops and propose future research questions. Copyright © 2016. Published by Elsevier Ltd.

  18. Sustainable Agricultural Mechanization for Smallholders: What Is It and How Can We Implement It?

    Directory of Open Access Journals (Sweden)

    Brian Sims


    Full Text Available Smallholder farmers are the main producers of the world’s food and they will have to increase production by up to 100 percent by 2050 to feed the growing population. This must be achieved while preserving natural resources and that is why sustainable agricultural mechanization (SAM will be fundamental to the process. SAM is climate-smart and environmentally benign and essentially means no-till conservation agriculture, which requires specific mechanization inputs. Principally, these are seeders and planters capable of penetrating soil surface vegetative cover to deposit seed and fertilizer at the required depth and spacing; and equipment for management of cover crops and weeds. Mechanization is required not only for crop production, but also for processing and along the entire value chain. Mechanization inputs are usually expensive and so specialist service provision will be the indicated way forward. This will need collaboration from both the private and public sectors and will involve public-private partnerships to be developed in one form or another. Given the poor track record of public sector mechanization provision, the delivery of SAM should be firmly in the hands of the private sector that should be committed to SAM principles or otherwise be incentivized to the concept through smart subsidies. Improved information flows via smallholder farmer-friendly innovation platforms; and continuing development and testing of SAM technologies via regional centres of excellence will both be required—especially for sub-Saharan Africa.

  19. The location- and depth-dependent mechanical response of the human cornea under shear loading. (United States)

    Sloan, Stephen R; Khalifa, Yousuf M; Buckley, Mark R


    To characterize the depth-dependent shear modulus of the central and peripheral human cornea along the superior-inferior and nasal-temporal directions with a high spatial resolution. Cylindrical explants from the central and peripheral corneas of 10 human donors were subjected to a 5% shear strain along the superior-inferior and nasal-temporal directions using a microscope-mounted mechanical testing device. Depth-dependent shear strain and shear modulus were computed through force measurements and displacement tracking. The shear modulus G of the human cornea varied continuously with depth, with a maximum occurring roughly 25% of the way from the anterior surface to the posterior surface. G also varied with direction in the superior region and (at some depths) was significantly higher for superior-inferior shear loading. In the anterior half of the cornea, the shear modulus along the nasal-temporal direction (GNT) did not vary with location; however, the superior region had significantly higher GNT in posterior cornea. In contrast, the shear modulus along the superior-inferior direction (GSI) was independent of location at all depths. This study demonstrates that the peak shear modulus of the human cornea occurs at a substantial distance within the corneal stroma. Depth-dependent differences between central and peripheral cornea possibly reflect the location-dependent mechanical environment of the cornea. Moreover, the cornea is not a transverse isotropic material, and must be characterized by more than a single shear modulus due to its dependence on loading direction. The material properties measured in this study are critical for developing accurate mechanical models to predict the vision-threatening morphological changes that can occur in the cornea. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  20. Mechanical Behavior of Liquid Route Processed SiCf/Ti Composites Under Longitudinal and Transverse Loadings (United States)

    Valle, Roger; Daux, Jean-Claude


    Due to the high melting point and strong chemical reactivity of titanium alloys, titanium matrix composites (TMCs) are usually processed through solid-state routes such as the foil-fiber-foil technique. An alternative method consists in the deposition of the matrix on the fibers. However, techniques such as physical vapor deposition lead to a very low deposition rate, contrary to liquid route processing using a levitating liquid alloy sphere held in a cold crucible. In order to investigate the effects of the resulting thermal shock on carbon-coated SiC fibers, and select an appropriate fiber, fibers are subjected to a pure thermal shock using a laser bench facility. These fibers are then tensile tested to failure in order to evaluate the resulting fiber strength degradation and, thus, the maximum acceptable temperature. Mechanical characterization of the liquid route processed TMC is then investigated through longitudinal and transverse tensile and creep tests at temperatures representative of aeronautical applications. The specimens, unbroken after long-duration creep tests, are then subjected to tensile loading to failure: conditions representative of service, i.e., short-time overspeeding of a gas turbine. Finally, interpretation of the mechanical tests through micrographical and microfractographical examinations is focused on the identification of the deformation and failure mechanisms specific to the liquid route processed composite, e.g., nucleation, under either longitudinal or transverse loadings, of internal cracks in the α-phase of the titanium-based matrix, explained through a physical model involving a high shear stress and normal stress combination, leading to cleavage.

  1. A comprehensive investigation into the effect of temperature variation on the mechanical properties of sustainable concrete

    Directory of Open Access Journals (Sweden)

    El Mir Abdulkader


    Full Text Available Minimizing the production energy and resources consumption are the key principle for engineering sustainability. In the case of concrete structures, this concept can be achieved by the use of materials in the most efficient way considering in the mix design the optimal mechanical and durability properties. The substitution of ordinary Portland cement for other supplementary cementitious materials is assessing the possibility of enhancing the sustainability and decreasing the environmental impact of concrete. Mass concrete is rich in cementitious materials which results in high temperature within the concrete, hence several hazards such as cracking or temperature differences between the interior and the surface of concrete could be prevented. An experimental study evaluated on several one cubic meter sized concrete elements in which during the primary phase of hydration, the temperature variation is recorded in several location offsets with respect to time. Thermal variations results are analyzed in accordance with the cement type, CO2 emission production of cement, compressive strength, water tightness, drying shrinkage and rapid chloride migration coefficient. The results indicate that slag cement CEM III/B 32.5, that incorporates highest amount of slag, ensured improved mechanical, thermal and durability properties in comparison with ordinary Portland cement CEM I 32.5.

  2. Polymer excipients enable sustained drug release in low pH from mechanically strong inorganic geopolymers. (United States)

    Jämstorp, Erik; Yarra, Tejaswi; Cai, Bing; Engqvist, Håkan; Bredenberg, Susanne; Strømme, Maria


    Improving acid resistance, while maintaining the excellent mechanical stability is crucial in the development of a sustained and safe oral geopolymer dosage form for highly potent opioids. In the present work, commercially available Methacrylic acid-ethyl acrylate copolymer, Polyethylene-glycol (PEG) and Alginate polymer excipients were included in dissolved or powder form in geopolymer pellets to improve the release properties of Zolpidem, herein acting as a model drug for the highly potent opioid Fentanyl. Scanning electron microscopy, compression strength tests and drug release experiments, in gastric pH 1 and intestinal pH 6.8 conditions, were performed. The polymer excipients, with an exception for PEG, reduced the drug release rate in pH 1 due to their ability to keep the pellets in shape, in combination with the introduction of an insoluble excipient, and thereby maintain a barrier towards drug diffusion and release. Neither geopolymer compression strength nor the release in pH 6.8 was considerably impaired by the incorporation of the polymer excipients. The geopolymer/polymer composites combine high mechanical strength and good release properties under both gastric and intestinal pH conditions, and are therefore promising oral dosage forms for sustained release of highly potent opioids.

  3. Analysis on the Load Carrying Mechanism Integrated as Heterogeneous Co-operative Manipulator in a Walking Wheelchair (United States)

    Rajay Vedaraj, I. S.; Jain, Ritika; Rao, B. V. A.


    used for climbing stairs with three leg design and anlaysis were also done on the mechanism integrated to the system. Kinematics of the legs are analysed separately and the legs are designed to carry a maximum of 175kgs, which is sustained by the center leg and shared by the dual wing legs equally during the walking phase. In the proposed design, screwjack mechanism is used as the central leg to share the load and thus the analysis on the load sharing capability of the whole system is analysed and concluded in terms of failure modes.

  4. Loading mechanics of the femur in tiger salamanders (Ambystoma tigrinum) during terrestrial locomotion. (United States)

    Sheffield, K Megan; Blob, Richard W


    Salamanders are often used as representatives of the basal tetrapod body plan in functional studies, but little is known about the loads experienced by their limb bones during locomotion. Although salamanders' slow walking speeds might lead to low locomotor forces and limb bone stresses similar to those of non-avian reptiles, their highly sprawled posture combined with relatively small limb bones could produce elevated limb bone stresses closer to those of avian and mammalian species. This study evaluates the loads on the femur of the tiger salamander (Ambystoma tigrinum) during terrestrial locomotion using three-dimensional measurements of the ground reaction force (GRF) and hindlimb kinematics, as well as anatomical measurements of the femur and hindlimb muscles. At peak stress (29.8 ± 2.0% stance), the net GRF magnitude averaged 0.42 body weights and was directed nearly vertically for the middle 20-40% of the contact interval, essentially perpendicular to the femur. Although torsional shear stresses were significant (4.1 ± 0.3 MPa), bending stresses experienced by the femur were low compared with other vertebrate lineages (tensile: 14.9 ± 0.8 MPa; compressive: -18.9 ± 1.0 MPa), and mechanical property tests indicated yield strengths that were fairly standard for tetrapods (157.1 ± 3.7 MPa). Femoral bending safety factors (10.5) were considerably higher than values typical for birds and mammals, and closer to the elevated values calculated for reptilian species. These results suggest that high limb bone safety factors may have an ancient evolutionary history, though the underlying cause of high safety factors (e.g. low limb bone loads, high bone strength or a combination of the two) may vary among lineages.

  5. Mechanical Differences between Barbell and Body Optimum Power Loads in the Jump Squat Exercise

    Directory of Open Access Journals (Sweden)

    Loturco Irineu


    Full Text Available This study compared the values of bar-peak force (PFBar and power (PPBar, body-peak force (PFBody and power (PPBody and bar-mean propulsive power (MPPBar in different jump-squat (JS conditions: unloaded condition (UC; bar-loaded condition (BLC and optimum bar-MPP condition (OBC. Twenty-five soccer players performed the JS using a bar with negligible mass (UC, using the Smith-machine bar (BLC and using the load capable of maximizing the bar-MPP (OBC. The PFBody was significantly higher in the UC (2847.9 ± 489.1 N than in the OBC (2655.4 ± 444.3 N. The UC presented greater PPBody (3775.9 ± 631.5 W than the BLC (3359.7 ± 664.3 W and OBC (3357.8 ± 625.3 W. The OBC presented higher values of PFBar, PPBar and MPPBar (676.2 ± 109.4 W than the BLC (MPPBar = 425.8 ± 53.7 W (all p < 0.05. In the OBC (compared to the UC, the body peak-power presented a reduction of ≈ 11%, while generating bar-power output from ≈ 59 to 73% higher than the BLC. While the fact that the body-peak power is maximized in the UC denotes a mechanical phenomenon, the bar-optimum load represents an intensity at which both components of the power equation (force and velocity are optimized. This has important implications for sports training.

  6. Improved tolerance to sequential glucose loading (Staub-Traugott effect): size and mechanisms

    DEFF Research Database (Denmark)

    Bonuccelli, Sandra; Muscelli, Elza; Gastaldelli, Amalia


    Improved glucose tolerance to sequential glucose loading (Staub-Traugott effect) is an important determinant of day-to-day glycemic exposure. Its mechanisms have not been clearly established. We recruited 17 healthy volunteers to receive two sequential oral glucose tolerance tests (OGTTs), at time...... 0 min and 180 min (Study I). The protocol was repeated on a separate day (Study II) except that plasma glucose was clamped at 8.3 mmol/l between 60 and 180 min. beta-Cell function was analyzed by mathematical modeling of C-peptide concentrations. In a subgroup, glucose kinetics were measured...... by a triple-tracer technique (infusion of [6,6-(2)H(2)]glucose and labeling of the 2 glucose loads with [1-(2)H]glucose and [U-(13)C]glucose). In both Studies I and II, the plasma glucose response to the second OGTT equaled 84 +/- 2% (P = 0.003) of the response to the first OGTT. Absolute insulin secretion...

  7. Dynamic Analysis of Cable-Stayed Bridges Affected by Accidental Failure Mechanisms under Moving Loads

    Directory of Open Access Journals (Sweden)

    Fabrizio Greco


    Full Text Available The dynamic behavior of cable-stayed bridges subjected to moving loads and affected by an accidental failure in the cable suspension system is investigated. The main aim of the paper is to quantify, numerically, the dynamic amplification factors of typical kinematic and stress design variables, by means of a parametric study developed in terms of the structural characteristics of the bridge components. The bridge formulation is developed by using a geometric nonlinear formulation, in which the effects of local vibrations of the stays and of large displacements in the girder and the pylons are taken into account. Explicit time dependent damage laws, reproducing the failure mechanism in the cable system, are considered to investigate the influence of the failure mode characteristics on the dynamic bridge behavior. The analysis focuses attention on the influence of the inertial characteristics of the moving loads, by accounting coupling effects arising from the interaction between girder and moving system. Sensitivity analyses of typical design bridge variables are proposed. In particular, the effects produced by the moving system characteristics, the tower typologies, and the failure mode characteristics involved in the cable system are investigated by means of comparisons between damaged and undamaged bridge configurations.

  8. Fracture Mechanisms of Zirconium Diboride Ultra-High Temperature Ceramics under Pulse Loading (United States)

    Skripnyak, Vladimir V.; Bragov, Anatolii M.; Skripnyak, Vladimir A.; Lomunov, Andrei K.; Skripnyak, Evgeniya G.; Vaganova, Irina K.


    Mechanisms of failure in ultra-high temperature ceramics (UHTC) based on zirconium diboride under pulse loading were studied experimentally by the method of SHPB and theoretically using the multiscale simulation method. The obtained experimental and numerical data are evidence of the quasi-brittle fracture character of nanostructured zirconium diboride ceramics under compression and tension at high strain rates and the room temperatures. Damage of nanostructured porous zirconium diboride -based UHTC can be formed under stress pulse amplitude below the Hugoniot elastic limit. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of microcracks. A decrease of the shear strength can be caused by nano-voids clusters in vicinity of triple junctions between ceramic matrix grains and ultrafine-grained ceramics. This research was supported by grants from ``The Tomsk State University Academic D.I. Mendeleev Fund Program'' and also N. I. Lobachevski State University of Nizhny Novgorod (Grant of post graduate mobility).

  9. Mechanisms of Active Aerodynamic Load Reduction on a Rotorcraft Fuselage With Rotor Effects (United States)

    Schaeffler, Norman W.; Allan, Brian G.; Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.; Mace, W. Derry; Wong, Oliver D.; Tanner, Philip E.


    The reduction of the aerodynamic load that acts on a generic rotorcraft fuselage by the application of active flow control was investigated in a wind tunnel test conducted on an approximately 1/3-scale powered rotorcraft model simulating forward flight. The aerodynamic mechanisms that make these reductions, in both the drag and the download, possible were examined in detail through the use of the measured surface pressure distribution on the fuselage, velocity field measurements made in the wake directly behind the ramp of the fuselage and computational simulations. The fuselage tested was the ROBIN-mod7, which was equipped with a series of eight slots located on the ramp section through which flow control excitation was introduced. These slots were arranged in a U-shaped pattern located slightly downstream of the baseline separation line and parallel to it. The flow control excitation took the form of either synthetic jets, also known as zero-net-mass-flux blowing, and steady blowing. The same set of slots were used for both types of excitation. The differences between the two excitation types and between flow control excitation from different combinations of slots were examined. The flow control is shown to alter the size of the wake and its trajectory relative to the ramp and the tailboom and it is these changes to the wake that result in a reduction in the aerodynamic load.

  10. Effects of Neuropeptides and Mechanical Loading on Bone Cell Resorption in Vitro

    Directory of Open Access Journals (Sweden)

    Yeong-Min Yoo


    Full Text Available Neuropeptides such as vasoactive intestinal peptide (VIP and calcitonin gene-related peptide (CGRP are present in nerve fibers of bone tissues and have been suggested to potentially regulate bone remodeling. Oscillatory fluid flow (OFF-induced shear stress is a potent signal in mechanotransduction that is capable of regulating both anabolic and catabolic bone remodeling. However, the interaction between neuropeptides and mechanical induction in bone remodeling is poorly understood. In this study, we attempted to quantify the effects of combined neuropeptides and mechanical stimuli on mRNA and protein expression related to bone resorption. Neuropeptides (VIP or CGRP and/or OFF-induced shear stress were applied to MC3T3-E1 pre-osteoblastic cells and changes in receptor activator of nuclear factor kappa B (NF-κB ligand (RANKL and osteoprotegerin (OPG mRNA and protein levels were quantified. Neuropeptides and OFF-induced shear stress similarly decreased RANKL and increased OPG levels compared to control. Changes were not further enhanced with combined neuropeptides and OFF-induced shear stress. These results suggest that neuropeptides CGRP and VIP have an important role in suppressing bone resorptive activities through RANKL/OPG pathway, similar to mechanical loading.

  11. Mechanical behavior of confined self-compacting reinforced concrete circular columns under concentric axial loading

    Directory of Open Access Journals (Sweden)

    Fouad Khairallah


    Full Text Available While there is abundant research information on ordinary confined concrete, there are little data on the behavior of Self-Compacting Concrete (SCC under such condition. Due to higher shrinkage and lower coarse aggregate content of SCC compared to that of Normal Concrete (NC, its composite performance under confined conditions needs more investigation. This paper has been devoted to investigate and compare the mechanical behavior of confined concrete circular columns cast with SCC and NC under concentric axial loading. The parameters affecting are including concrete compressive strength and confinement configuration. Twenty column specimens were casted and confined using four confinement techniques, CFRP wrap, FRP tube, GFRP wrap, and spiral steel hoops. The performance of the tested column specimens is evaluated based on mode of failure, load–displacement curve, stress–strain characteristics, ultimate strength, ductility, and degree of confinement.

  12. Simulation of Mechanical Behavior and Damage of a Large Composite Wind Turbine Blade under Critical Loads (United States)

    Tarfaoui, M.; Nachtane, M.; Khadimallah, H.; Saifaoui, D.


    Issues such as energy generation/transmission and greenhouse gas emissions are the two energy problems we face today. In this context, renewable energy sources are a necessary part of the solution essentially winds power, which is one of the most profitable sources of competition with new fossil energy facilities. This paper present the simulation of mechanical behavior and damage of a 48 m composite wind turbine blade under critical wind loads. The finite element analysis was performed by using ABAQUS code to predict the most critical damage behavior and to apprehend and obtain knowledge of the complex structural behavior of wind turbine blades. The approach developed based on the nonlinear FE analysis using mean values for the material properties and the failure criteria of Tsai-Hill to predict failure modes in large structures and to identify the sensitive zones.

  13. Effect of a rapid repair mechanism for nitrification capacity in the load impact wastewater treatment (United States)

    Hong, Wei; Zhang, Bing; Sun, Changdong; Tan, Xin; Liu, Bo; Zou, Xiaofeng


    The nitrification capacity in the wastewater treatment is very important, and is particularly vulnerable to impacts. In this study, a rapid repair mechanism for nitrification was built and the result showing that, with the addition of exogenous nitrifying bacteria and organic nutrient, the nitrification capacity in the pilot scale equipment was restored in 20h, the concentration of NH3-N in discharge conforms to the one-class A permitted criterion (GB 18918-2002) and remain stable for long time, while the nitrification capacity in control group would not be fixed by itself in 196h. The repaired experimental group has the advantage of strong shock resistance and stable operation, and under the second high impact load, the concentration of NH3-N in effluent remain stable.

  14. Mechanical analysis of a rodent segmental bone defect model: the effects of internal fixation and implant stiffness on load transfer. (United States)

    Yavari, S Amin; van der Stok, J; Ahmadi, S M; Wauthle, R; Schrooten, J; Weinans, H; Zadpoor, A A


    Segmental bone defect animal models are often used for evaluating the bone regeneration performance of bone substituting biomaterials. Since bone regeneration is dependent on mechanical loading, it is important to determine mechanical load transfer after stabilization of the defect and to study the effects of biomaterial stiffness on the transmitted load. In this study, we assess the mechanical load transmitted over a 6mm femur defect that is stabilized with an internal PEEK fixation plate. Subsequently, three types of selective laser melted porous titanium implants with different stiffness values were used to graft the defect (five specimens per group). In one additional group, the defect was left empty. Micro strain gauges were used to measure strain values at four different locations of the fixation plate during external loading on the femoral head. The load sharing between the fixation plate and titanium implant was highly variable with standard deviations of measured strain values between 31 and 93% of the mean values. As a consequence, no significant differences were measured between the forces transmitted through the titanium implants with different elastic moduli. Only some non-significant trends were observed in the mean strain values that, consistent with the results of a previous finite element study, implied the force transmitted through the implant increases with the implant stiffness. The applied internal fixation method does not standardize mechanical loading over the defect to enable detecting small differences in bone regeneration performances of bone substituting biomaterials. In conclusion, the fixation method requires further optimization to reduce the effects of the operative procedure and make the mechanical loading more consistent and improve the overall sensitivity of this rat femur defect model. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Electromagnetic and mechanical characteristion of ITER CS-MC conductors affected by transverse cyclic loading, part 2: Interstrand contact resistance

    NARCIS (Netherlands)

    Nijhuis, Arend; Noordman, Niels H.W.; ten Kate, Herman H.J.; Mitchell, Neil; Bruzzone, Pierluigi


    A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER multistrand Nb3Sn cable-in-conduit conductor samples under transverse, mechanical loading. This simulates the transverse magnetic force that occurs when the conductors are used in a coil. The

  16. A Model for Sustainable Building Energy Efficiency Retrofit (BEER) Using Energy Performance Contracting (EPC) Mechanism for Hotel Buildings in China (United States)

    Xu, Pengpeng

    Hotel building is one of the high-energy-consuming building types, and retrofitting hotel buildings is an untapped solution to help cut carbon emissions contributing towards sustainable development. Energy Performance Contracting (EPC) has been promulgated as a market mechanism for the delivery of energy efficiency projects. EPC mechanism has been introduced into China relatively recently, and it has not been implemented successfully in building energy efficiency retrofit projects. The aim of this research is to develop a model for achieving the sustainability of Building Energy Efficiency Retrofit (BEER) in hotel buildings under the Energy Performance Contracting (EPC) mechanism. The objectives include: • To identify a set of Key Performance Indicators (KPIs) for measuring the sustainability of BEER in hotel buildings; • To identify Critical Success Factors (CSFs) under EPC mechanism that have a strong correlation with sustainable BEER project; • To develop a model explaining the relationships between the CSFs and the sustainability performance of BEER in hotel building. Literature reviews revealed the essence of sustainable BEER and EPC, which help to develop a conceptual framework for analyzing sustainable BEER under EPC mechanism in hotel buildings. 11 potential KPIs for sustainable BEER and 28 success factors of EPC were selected based on the developed framework. A questionnaire survey was conducted to ascertain the importance of selected performance indicators and success factors. Fuzzy set theory was adopted in identifying the KPIs. Six KPIs were identified from the 11 selected performance indicators. Through a questionnaire survey, out of the 28 success factors, 21 Critical Success Factors (CSFs) were also indentified. Using the factor analysis technique, the 21 identified CSFs in this study were grouped into six clusters to help explain project success of sustainable BEER. Finally, AHP/ANP approach was used in this research to develop a model to

  17. Elastic-Plastic Nonlinear Response of a Space Shuttle External Tank Stringer. Part 2; Thermal and Mechanical Loadings (United States)

    Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.


    Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.

  18. New fly ash TiO{sub 2} composite for the sustainable treatment of wastewater with complex pollutants load

    Energy Technology Data Exchange (ETDEWEB)

    Visa, Maria, E-mail:; Isac, Luminita; Duta, Anca


    Graphical abstract: - Highlights: • A novel substrate FADAht is obtained by hydrothermal synthesis. • The composite type structure has specific surface ten times higher than fly ash. • Simultaneous removal of three pollutants reaches efficiencies above 90%. • Kinetic investigations show fast adsorption of the dye on the new composite. - Abstract: The goal of this paper was to develop a new composite obtained in mild hydrothermal conditions starting from fly ash (a waste raising significant environmental problems), and TiO{sub 2}. The composite was characterized through XRD, SEM/EDX, AFM, and BET surface measurements. The composite was further used for the advanced treatment of wastewaters with multiple-pollutants load. The photocatalytic efficiency of the powder composite was tested on synthetic solutions containing a heavy metal cation (copper), a dye (methyl orange), and a surfactant (sodium dodecylbenzenesulfonate), under UV and simulated solar radiation. Comparative experiments were done in systems with and without H{sub 2}O{sub 2} showing a significant increase in efficiency for methyl orange removal from mono-, bi-, and tri-pollutants solutions. The process parameters were optimized and the adsorption mechanisms are discussed, outlining that adsorption is the limiting step. Experiments also outlined that homogeneous photocatalysis (using H{sub 2}O{sub 2}) is less efficient then the heterogeneous process using the novel composite, both under UV and simulated solar radiation.

  19. New fly ash TiO2 composite for the sustainable treatment of wastewater with complex pollutants load (United States)

    Visa, Maria; Isac, Luminita; Duta, Anca


    The goal of this paper was to develop a new composite obtained in mild hydrothermal conditions starting from fly ash (a waste raising significant environmental problems), and TiO2. The composite was characterized through XRD, SEM/EDX, AFM, and BET surface measurements. The composite was further used for the advanced treatment of wastewaters with multiple-pollutants load. The photocatalytic efficiency of the powder composite was tested on synthetic solutions containing a heavy metal cation (copper), a dye (methyl orange), and a surfactant (sodium dodecylbenzenesulfonate), under UV and simulated solar radiation. Comparative experiments were done in systems with and without H2O2 showing a significant increase in efficiency for methyl orange removal from mono-, bi-, and tri-pollutants solutions. The process parameters were optimized and the adsorption mechanisms are discussed, outlining that adsorption is the limiting step. Experiments also outlined that homogeneous photocatalysis (using H2O2) is less efficient then the heterogeneous process using the novel composite, both under UV and simulated solar radiation.

  20. Mechanical properties and in vivo healing evaluation of a novel Centella asiatica-loaded hydrocolloid wound dressing. (United States)

    Jin, Sung Giu; Kim, Kyung Soo; Yousaf, Abid Mehmood; Kim, Dong Wuk; Jang, Sun Woo; Son, Mi-Won; Kim, Young Hun; Yong, Chul Soon; Kim, Jong Oh; Choi, Han-Gon


    To develop a novel sodium alginate based Centella asiatica (CA)-loaded hydrocolloid wound dressing (HCD) providing excellent mechanical properties and improved wound healing, numerous CA-loaded HCDs were prepared with various ingredients using the hot melting method. The effect of sodium alginate, styrene-isoprene-styrene copolymer (SIS) and petroleum hydrocarbon resin (PHR) on the mechanical properties of CA-loaded HCDs was investigated. The effect of disintegrants on swelling and drug release was assessed. Moreover, the in vivo wound healing potentials of the selected CA-loaded HCD in various wound models such as abrasion, excision and infection were evaluated in comparison with the commercial product. Polyisobutylene and SIS hardly affected the mechanical properties, but PHR improved the tensile strength and elongation at break. Disintegrants such as croscarmellose sodium, sodium starch glycolate and crospovidone improved the swelling ratio of the CA-loaded HCD. Furthermore, the CA-loaded HCD without croscarmellose sodium poorly released the drug, but that with 2% croscarmellose sodium showed about 27% drug release in 24h. In particular, the CA-loaded HCD composed of CA/polyisobutylene/SIS/PHR/liquid paraffin/sodium alginate/croscarmellose sodium at the weight ratio of 1/8/25/25/12/27/2 furnished excellent mechanical properties and drug release. As compared with the commercial product, it offered improved healing effects in excision, infection and abrasion type wounds in rats. Thus, this novel CA-loaded HCD could be a potential candidate for the treatment of various wounds. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Structural and Mechanical Characterization of Sustainable Composites Based on Recycled and Stabilized Fly Ash

    Directory of Open Access Journals (Sweden)

    Stefano Besco


    Full Text Available This paper reports the results on the use of an innovative inert, based on stabilized fly ash from municipal solid waste incineration as a filler for polypropylene. The starting material, which contains large quantities of leachable Pb and Zn, was stabilized by means of an innovative process using rice husk ash as a waste silica source, together with other fly ashes, such as coal fly ash and flue gas desulfurization residues. The use of all waste materials to obtain a new filler makes the proposed technology extremely sustainable and competitive. The new composites, obtained by using the stabilized material as a filler for polypropylene, were characterized and their mechanical properties were also investigated. A comparison with a traditional polypropylene and calcium carbonate based compound was also done. This research activity was realized in the frame of the COSMOS-RICE project, financed by the EU Commission.

  2. Effect of mechanical loading on the removal torque of different types of tapered connection abutments for dental implants. (United States)

    Pintinha, Marilene; Camarini, Edevaldo Tadeu; Sábio, Sergio; Pereira, Jefferson Ricardo


    The mechanical behavior of internal taper implant abutment designs needs to be evaluated. The purpose of this study was to evaluate the effect of simulated mechanical loading on the removal torque of 1-piece and 2-piece abutments connected to internal taper oral implants. Forty-eight internally notched taper implants were divided into 2 groups of 24. Group OP received solid (1-piece) abutments; group TP received esthetic (2-piece) abutments. Each group was further subdivided into subgroups C (control) without mechanical loading and T (test) with mechanical loading. In groups OPC and TPC, the abutments were placed and removed and the removal torque values (RTVs) registered. In groups OPT and TPT, abutments were placed, mechanically loaded (500 000 cycles), removed, and the RTVs registered. Groups TPC and TPT were further tested for the traction force necessary to dislodge the abutment from the implant. For data analysis, the Student t test (for RTVs) and the Mann-Whitney U test (for TFVs) (α=.05) were performed. All abutments tested presented torque loss with RTVs lower than the placement torque. A statistically significant difference (P=.002) was found between groups OPC (81.6% of placement torque) and OPT mean RTVs results (85.0% of placement torque), while no statistical differences (P=.362) were found between groups TPC (63.7% of placement torque) and TPT (59.1% of placement torque). The traction force values necessary to dislodge the abutment from the implant, however, were significantly higher (Pwelding did not occur in any of the abutment specimens tested. Even after the mechanical loading, esthetic abutments presented similar RTVs. The traction force necessary to remove esthetic abutments from inside the implants presented a 2-fold increase after mechanical loading. Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  3. Experimental Investigation on the Fatigue Mechanical Properties of Intermittently Jointed Rock Models Under Cyclic Uniaxial Compression with Different Loading Parameters (United States)

    Liu, Yi; Dai, Feng; Dong, Lu; Xu, Nuwen; Feng, Peng


    Intermittently jointed rocks, widely existing in many mining and civil engineering structures, are quite susceptible to cyclic loading. Understanding the fatigue mechanism of jointed rocks is vital to the rational design and the long-term stability analysis of rock structures. In this study, the fatigue mechanical properties of synthetic jointed rock models under different cyclic conditions are systematically investigated in the laboratory, including four loading frequencies, four maximum stresses, and four amplitudes. Our experimental results reveal the influence of the three cyclic loading parameters on the mechanical properties of jointed rock models, regarding the fatigue deformation characteristics, the fatigue energy and damage evolution, and the fatigue failure and progressive failure behavior. Under lower loading frequency or higher maximum stress and amplitude, the jointed specimen is characterized by higher fatigue deformation moduli and higher dissipated hysteresis energy, resulting in higher cumulative damage and lower fatigue life. However, the fatigue failure modes of jointed specimens are independent of cyclic loading parameters; all tested jointed specimens exhibit a prominent tensile splitting failure mode. Three different crack coalescence patterns are classified between two adjacent joints. Furthermore, different from the progressive failure under static monotonic loading, the jointed rock specimens under cyclic compression fail more abruptly without evident preceding signs. The tensile cracks on the front surface of jointed specimens always initiate from the joint tips and then propagate at a certain angle with the joints toward the direction of maximum compression.

  4. Investigation of drug loading and in vitro release mechanisms of insulin-lauryl sulfate complex loaded PLGA nanoparticles. (United States)

    Shi, K; Cui, F; Yamamoto, H; Kawashima, Y


    Insulin, a water soluble peptide hormone, was hydrophobically ion-paired with sodium lauryl sulfate (SDS) at the stoichiometric molar ratio of 6:1. The obtained insulin-SDS complex precipitation was subsequently formulated in biodegradable poly (D,L-lactic-co-glycolic acid) (PLGA) nanoparticles by a modified spontaneous emulsion solvent diffusion method. Compared with a conventional method for free insulin encapsulation, direct dissolution of SDS-paired insulin in the non-aqueous organic phase led to an increase in drug recovery from 42.5% to 89.6%. The more hydrophobic complex contributes to the improved affinity of insulin to the polymer matrix, resulting in a higher drug content in the nanoparticles. The drug loading was investigated by determining initial burst release at the first 30 min. The results showed that 64.8% of recovered drug were preferentially surface bound on complex loaded nanoparticles. The in vitro drug release was characterized by an initial burst and subsequent delayed release in dissolution media of deionized water and phosphate buffer saline (PBS). Compared with that in PBS, nanoparticles in deionized water medium presented very low initial burst release (15% vs. 65%) and incomplete cumulative release (25% vs. 90%) of the drug. In addition, dialysis experiments were performed to clarify the form of the released insulin in the dissolution media. The results suggested that the ion-pair complex was sensitive to ionic strength, insulin was released from the particular matrix as complex form and subsequently suffered dissociation from SDS in buffer saline. Moreover, the in vivo bioactivity of the SDS-paired insulin and nanoparticulate formulations were evaluated in mice by estimation of their blood sugar levels. The results showed that the bioactivity of insulin was unaltered after the ion-pairing process.

  5. Crack Propagation Calculations for Optical Fibers under Static Bending and Tensile Loads Using Continuum Damage Mechanics (United States)

    Chen, Yunxia; Cui, Yuxuan; Gong, Wenjun


    Static fatigue behavior is the main failure mode of optical fibers applied in sensors. In this paper, a computational framework based on continuum damage mechanics (CDM) is presented to calculate the crack propagation process and failure time of optical fibers subjected to static bending and tensile loads. For this purpose, the static fatigue crack propagation in the glass core of the optical fiber is studied. Combining a finite element method (FEM), we use the continuum damage mechanics for the glass core to calculate the crack propagation path and corresponding failure time. In addition, three factors including bending radius, tensile force and optical fiber diameter are investigated to find their impacts on the crack propagation process and failure time of the optical fiber under concerned situations. Finally, experiments are conducted and the results verify the correctness of the simulation calculation. It is believed that the proposed method could give a straightforward description of the crack propagation path in the inner glass core. Additionally, the predicted crack propagation time of the optical fiber with different factors can provide effective suggestions for improving the long-term usage of optical fibers. PMID:29140284

  6. Mechanical damage in a lithium-ion pouch cell under indentation loads (United States)

    Luo, Hailing; Xia, Yong; Zhou, Qing


    The short circuit of lithium-ion batteries induced by mechanical abuse is a great concern in electric vehicle design. It remains a challenge to fully understand the nature of the mechanical damage process with the aim of improving battery crash safety. The present paper investigates the evolution of the damage process for a lithium-ion pouch cell under indentation by loading the cell to various force levels. A significant inflection point on the force-indentation curve is observed before the force peak. Post-mortem examinations indicate that the characteristic change in the local slope of the curve is related to the change occurring at the local interfaces, including three phenomena - formation of tight adhesion on the anode-separator interfaces, delamination in the separators and decoating of graphite particles from the anodes. Analysis of the fracture sequence at the onset of short circuit clearly shows that the number of short-circuited electrode pairs is equal to the number of anode layers adhered with delaminated separator material before fracture occurs. The experimental study in the present paper implies that the inflection point on the force-indentation curve may be an indicator of damage initiation inside pouch cells under indentation.

  7. Influence of loading rate on the mechanical performance of metallic glass

    NARCIS (Netherlands)

    Huráková, Mária; Csach, Kornel; Juríková, Alena; Miškuf, Jozef; Demčák, Štefan; Ocelík, Václav; De Hosson, Jeff Th M.


    Amorphous metallic glass Cu47Ti35Zr11Ni6Si1 was investigated by load-control nanoindentation experiments using the cube corner indenter tip over a wide range of loading rates. The indentation hardness was calculated using different methods either from the loading curves or indent area. Pop-in events

  8. Experimental Study On Lateral Load Capacity of Bamboo RC Beam Column Joints Strengthened By Bamboo Mechanical Anchors

    Directory of Open Access Journals (Sweden)

    Sri Umniati B.


    Full Text Available In this paper, the prospective of bamboos which available abundantly especially in Indonesia as rebars and mechanical anchors are studied. And also the endurance of the bamboos mechanical anchors to withstand cyclic loading were observed. Nine classes of bamboos bar were evaluated: consist of 3 different anchors (0, 4 and 8 anchors and 3 different compressive strength (19.19 MPa, 29.61 MPa and 37.96 MPa means 3 × 3 parameters. The results show that the lateral load capacity increased significantly with the present of bamboo anchors specimens: 26.04 % for 4 anchors specimens (C2 and 25 % for the 8 anchors specimens (C3 compared to zero anchor specimens (C1. On the other hand, the compressive strength of concrete have no significant effects to the lateral load capacity. Overall it can be concluded that, bamboo can be used as mechanical anchorage to strengthen beam column joint.

  9. Numerical modeling of mechanical behavior of multilayered composite plates with defects under static loading (United States)

    Korepanov, V. V.; Serovaev, G. S.


    Evaluation of the mechanical state of a structure or its components in the process of operation based on detection of internal damages (damage detection) becomes especially important in such rapidly developing spheres of production as machine building, aerospace industry, etc. One of the most important features of these industries is the application of new types of materials among which polymer based composite materials occupy a significant position. Hence, they must have sufficient operational rigidity and strength. However, defects of various kinds may arise during the manufacture. Delamination is the most common defect in structures made from composite materials and represents a phenomenon that involves the complex fracture of layers and interlayer compounds. Among the reasons of delamination occurrence are: disposition of anti-adhesive lubricants, films; insufficient content of binder, high content of volatile elements; violation of the molding regime; poor quality of anti-adhesive coating on the surface of the tooling. One of the effective methods for analyzing the influence of defects is numerical simulation. With the help of numerical methods, it is possible to track the evolution of various parameters when the defect size and quantity change. In the paper, a multilayered plate of an equally resistant carbon fiber reinforced plastic was considered, with a thickness of each layer equal to 0.2 mm. Various static loading cases are studied: uniaxial tension, three and four-point bending. For each type of loading, a numerical calculation of the stress-strain state was performed for healthy and delaminated plates, with different number and size of the defects. Contact interaction between adjacent surfaces in the zone of delamination was taken into account.

  10. Effect of tooth brush abrasion and thermo-mechanical loading on direct and indirect veneer restorations. (United States)

    Rosentritt, Martin; Sawaljanow, Alexander; Behr, Michael; Kolbeck, Carola; Preis, Verena


    This study investigated toothbrush abrasion and in vitro aging on ceramic (indirect technique) and composite veneers (direct technique). Identical composite and individual human incisors were restored with industrially preformed composite veneers, indirectly produced ceramic veneers, and direct composite restorations. Surface roughness was determined before and after tooth brushing. A 5-year period of oral service was simulated by thermal cycling and mechanical loading (TCML). After TCML, all specimens were examined with microscopy and scanning electron microscopy. Specimens without failures during TCML were loaded until failure. analysis of variance; Bonferroni's post hoc analysis, Kaplan-Meier-Log Rank test (α = 0.05). Tooth brushing yielded a non-significant increase (p = 0.560) in roughness in all materials (industrial veneer, 0.12+/-0.07 μm, direct restoration, 0.18+/-0.14 μm, ceramic, 0.35+/-0.16 μm). No significant differences in roughness could be determined between the materials, neither before nor after testing (p teeth, direct and preformed composite veneers on composite teeth showed no failures or damages. Two ceramic veneers showed cracking in the labial area. After TCML of human teeth, transmission microscopy indicated a facial crack in a ceramic veneer and chipping in the cervical area of a preformed veneer. Two direct composite veneers lost retention. No significantly different survival rates were found between the three veneer groups. Fracture force on human teeth varied between 527.8+/-132.4 N (ceramic), 478.3+/-165.4 N (preformed composite), and 605.0+/-263.5 N (direct composite). All materials revealed comparable wear resistance. Indirect ceramic, direct restorative composite, and preformed composite veneers showed comparable failure rates and satisfying longevity. The results indicate similar longevity of the chosen materials for veneer restorations.

  11. Effects of habitual loading on patellar tendon mechanical and morphological properties in basketball and volleyball players. (United States)

    Zhang, Z J; Ng, G Y F; Fu, S N


    Tendon mechanical properties are linked to sports performance and tendon-related injuries, such as tendinopathy. Whether habitual loading, such as participation in regular jumping activities, would induce adaptation on tendon mechanical properties remains unclear. Forty healthy subjects (10 sedentary, 15 volleyball players, and 15 basketball players) aged between 18 and 35 years were recruited. Supersonic shearwave imaging was used to measure the shear elastic modulus and thickness and cross-sectional area (CSA) of the proximal patellar tendons of both knees at 30° of flexion. Significant group differences in tendon shear elastic modulus were found among the three groups. In the dominant leg, reduction in tendon shear elastic modulus by 18.9 % (p = 0.018) and 48.7 % (p = 0.000) were observed in the basketball and volleyball players, respectively, when compared with sedentary subjects. In the non-dominant leg, reduction in tendon shear elastic modulus were 27.3 % (p = 0.034) and 47.1 % (p = 0.02) in the basketball and volleyball players, respectively. The athlete groups were found to have larger CSA but with similar tendon thickness than sedentary group. The CSA were larger by 24-29 % and by 22-24 % in the basketball players and volleyball players, for the dominant and non-dominant legs, respectively (all p < 0.05). Age and body mass are related to tendon stiffness and CSA, particularly in the sedentary subjects. The proximal patellar tendon can undergo substantial adaptation on tendon mechanical and morphological properties when exposed in jumping sports. Intrinsic factors such as age and body mass could influence tendon properties.

  12. The DARTNet Institute: Seeking a Sustainable Support Mechanism for Electronic Data Enabled Research Networks. (United States)

    Pace, Wilson D; Fox, Chester H; White, Turner; Graham, Deborah; Schilling, Lisa M; West, David R


    Clinical data research networks require large investments in infrastructure support to maintain their abilities to extract, transform, and load data from varied data sources, expand electronic data sources and develop learning communities. This paper outlines a sustainable business model of ongoing infrastructure support for clinical data research activities. The DARTNet Institute is a not-for-profit 501(c)(3) organization that serves as a support entity for multiple practice-based research networks. Several clinical data research networks working closely with a professional society began collaborating to support shared goals in 2008. This loose affiliation called itself the "DARTNet Collaborative." In 2011, the DARTNet Institute incorporated as an independent, not-for-profit entity. The business structure allows DARTNet to advocate for all partners without operating its own practice-based research network, serve as a legal voice for activities that overlap multiple partners, share personnel resources through service contracts between partners, and purchase low-cost (nonprofit rate) software. DARTNet's business model relies upon four diverse sources of revenue: (1) DARTNet licenses and provides access to a propriety software system that extracts, transforms, and loads data from all major electronic health records (EHRs) utilized in the United States, and which also provides clinical decision support for research studies; (2) DARTNet operates a recognized, national professional-society-quality improvement registry that enables organizations to fulfill Meaningful Use 2 criteria; (3) DARTNet provides access to data for research activities that are funded by direct research dollars, provided at prices that generate excess revenue; and (4) DARTNet provides access to large primary care datasets for observational studies and pregrant analyses such as for sample size development. The ability of the system to support pragmatic trials will be described. The DARTNet model

  13. Green Concrete from Sustainable Recycled Coarse Aggregates: Mechanical and Durability Properties

    Directory of Open Access Journals (Sweden)

    Neeraj Jain


    Full Text Available Present investigations deal with the development of green concrete (M 30 grade using recycled coarse aggregates for sustainable development. Characterization of recycled coarse aggregates showed that physical and mechanical properties are of inferior quality and improvement in properties was observed after washing due to removal of old weak mortar adhered on its surface. The influence of natural coarse aggregates replacement (50 and 100% with recycled coarse aggregate on various mechanical and durability properties of hardened concrete were discussed and compared with controls at different w/c ratio. Improvements in all the engineering properties of hardened concrete were observed using washed recycled coarse aggregates. The compressive strength of 28-day hardened concrete containing 100% washed recycled aggregate was slightly lower (7% than concrete prepared with natural aggregates. Water absorption, carbonation, and rapid chloride penetration test were conducted to assess the durability of the concrete. Concrete was found moderately permeable for chloride ions penetration and no carbonation was observed in all the concrete mixes studied.

  14. Mechanical and biological consequences of repetitive loading: crack initiation and fatigue failure in the red macroalga Mazzaella. (United States)

    Mach, Katharine J


    On rocky shores, wave-swept macroalgae experience dramatic and repeated wave-induced hydrodynamic forces. However, previous studies of macroalgal mechanics have shown that individual waves are not forceful enough to account for observed rates of breakage. Instead, fatigue may contribute to algal breakage, with damage accumulating over time in conditions of repeated loading. Here I examine the entire process of fatigue, from crack initiation to eventual specimen fracture, in the common red alga Mazzaella. Propensity for fatigue failure in laboratory tests varied with life history phase and species: at a given repeated loading stress, male gametophytes endured more loading cycles before breakage than tetrasporophytes, which in turn lasted longer than female gametophytes; likewise, M. splendens withstood more loading cycles at a given repeated loading stress than M. flaccida. Fatigue failure begins with formation of cracks, the timing and location of which were assessed. Cracks formed, on average, after approximately 80-90% of cycles required for failure had passed, although crack timing varied with life history phase. Also, crack formation frequently occurred in association with endophytes and female gametophyte reproductive structures, suggesting a cost of endophyte infection and a tradeoff between reproduction and mechanical survival. Comparison between laboratory and field loading conditions provides robust confirmation that fatigue breaks fronds in natural M. flaccida populations. Large, female gametophyte fronds are predicted to be most susceptible to fatigue failure in the field, whereas small, male gametophyte fronds are least likely to break.

  15. Prediction of contact mechanics in metal-on-metal Total Hip Replacement for parametrically comprehensive designs and loads. (United States)

    Donaldson, Finn E; Nyman, Edward; Coburn, James C


    Manufacturers and investigators of Total Hip Replacement (THR) bearings require tools to predict the contact mechanics resulting from diverse design and loading parameters. This study provides contact mechanics solutions for metal-on-metal (MoM) bearings that encompass the current design space and could aid pre-clinical design optimization and evaluation. Stochastic finite element (FE) simulation was used to calculate the head-on-cup contact mechanics for five thousand combinations of design and loading parameters. FE results were used to train a Random Forest (RF) surrogate model to rapidly predict the contact patch dimensions, contact area, pressures and plastic deformations for arbitrary designs and loading. In addition to widely observed polar and edge contact, FE results included ring-polar, asymmetric-polar, and transitional categories which have previously received limited attention. Combinations of design and load parameters associated with each contact category were identified. Polar contact pressures were predicted in the range of 0-200 MPa with no permanent deformation. Edge loading (with subluxation) was associated with pressures greater than 500 MPa and induced permanent deformation in 83% of cases. Transitional-edge contact (with little subluxation) was associated with intermediate pressures and permanent deformation in most cases, indicating that, even with ideal anatomical alignment, bearings may face extreme wear challenges. Surrogate models were able to accurately predict contact mechanics 18,000 times faster than FE analyses. The developed surrogate models enable rapid prediction of MoM bearing contact mechanics across the most comprehensive range of loading and designs to date, and may be useful to those performing bearing design optimization or evaluation. Published by Elsevier Ltd.

  16. Methoxetamine produces rapid and sustained antidepressant effects probably via glutamatergic and serotonergic mechanisms. (United States)

    Botanas, Chrislean Jun; Bryan de la Peña, June; Custodio, Raly James; Joy Dela Peña, Irene; Kim, Mikyung; Woo, Taeseon; Kim, Hee Jin; Kim, Hye In; Chang Cho, Min; Lee, Yong Sup; Cheong, Jae Hoon


    Depression afflicts around 16% of the world's population, making it one of the leading causes of disease burden worldwide. Despite a number of antidepressants available today, the delayed onset time and low remission rate of these treatments are still a major challenge. The N-methyl-D-aspartate (NMDA) receptor antagonist ketamine has shown to produce rapid and sustained antidepressant effects and has paved the way for a new generation of glutamate-based antidepressants. Methoxetamine (MXE) is a ketamine analogue that acts as an NMDA receptor antagonist and a serotonin reuptake inhibitor. However, no studies have evaluated the antidepressant effects of MXE. Here, we assessed whether MXE produces antidepressant effects and explored possible mechanisms underlying its effects. Mice were treated with MXE (2.5, 5, or 10 mg/kg) and their behavior was evaluated 30 min and 24 h later in an array of behavioral experiments used for screening antidepressant drugs. A separate group of mice were treated with NBQX, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, or ketanserin, a 5HT2 receptor antagonist, before MXE (5 mg/kg) administration in the forced swimming test (FST). We also investigated the effect of MXE on glutamatergic- and serotonergic-related genes in the mouse hippocampus using quantitative real-time PCR. MXE produced antidepressant effects 30 min after treatment that persisted for 24 h. Both NBQX and ketanserin blocked the antidepressant effects of MXE in the FST. MXE also altered hippocampal glutamatergic- and serotonergic gene expressions. These results suggest that MXE has rapid and sustained antidepressant effects, possibly mediated by the glutamatergic and serotonergic system. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Mechanical performance of hydrogel contact lenses with a range of power under parallel plate compression and central load. (United States)

    Robitaille, Michael; Shi, Jiayi; McBride, Shannon; Wan, Kai-Tak


    When a contact lens is compressed between two parallel plates (PPC) or under a central load (CLC), the constitutive relation depends not only on the mechanical properties such as elastic modulus, E, of the hydrogel materials, but also the lens power, d, or thickness variation, h(ϕ0), along the meridional direction ϕ0. Hyperopic lenses (d>0) are thicker at the apex along the optical axis and thin out gradually along the meridian, while myopic lenses (d<0) are thinnest at the apex. Mechanical deformation is quantified by the inter-relationship between applied force, F, vertical displacement of the external load, w0, contact or dimple radius, a, and the deformed profile, w(r). Force responses show that lenses with positive d are apparently stiffer in the initial loading but become more compliant as load increases. Conversely, lenses with negative d are more deformable initially and becomes gradually more resistant to loading. This is consistent with the theoretical shell model using the same E. The mechanical behavior has significant impacts in defining the degree of comfort of contact lenses as well as the lens adhesion to the corneal epithelium. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Shear transfer across a single crack in reinforced concrete under sustained loading. Part III : Analysis of experiments

    NARCIS (Netherlands)

    Frénay, J.W.


    The results of experimental investigations on internally reinforced "pushoff" test specimens, each formed with one central crack and subjected to a constant external shear loading, were analysed. The crack width and the parallel displacement were measured periodically. The experimental variables

  19. Mesoporous silica nanoparticles loading doxorubicin reverse multidrug resistance: performance and mechanism (United States)

    Shen, Jianan; He, Qianjun; Gao, Yu; Shi, Jianlin; Li, Yaping


    Multidrug resistance (MDR) is one of the major obstacles for successful chemotherapy in cancer. One of the effective approaches to overcome MDR is to use nanoparticle-mediated drug delivery to increase drug accumulation in drug resistant cancer cells. In this work, we first report that the performance and mechanism of an inorganic engineered delivery system based on mesoporous silica nanoparticles (MSNs) loading doxorubicin (DMNs) to overcome the MDR of MCF-7/ADR (a DOX-resistant and P-glycoprotein (P-gp) over-expression cancer cell line). The experimental results showed that DMNs could enhance the cellular uptake of doxorubicin (DOX) and increase the cell proliferation suppression effect of DOX against MCF-7/ADR cells. The IC50 of DMNs against MCF-7/ADR cells was 8-fold lower than that of free DOX. However, an improved effect of DOX in DMNs against MCF-7 cells (a DOX-sensitive cancer cell line) was not found. The increased cellular uptake and nuclear accumulation of DOX delivered by DMNs in MCF-7/ADR cells was confirmed by confocal laser scanning microscopy, and could result from the down-regulation of P-gp and bypassing the efflux action by MSNs themselves. The cellular uptake mechanism of DMNs indicated that the macropinocytosis was one of the pathways for the uptake of DMNs by MCF-7/ADR cells. The in vivo biodistribution showed that DMNs induced a higher accumulation of DOX in drug resistant tumors than free DOX. These results suggested that MSNs could be an effective delivery system to overcome multidrug resistance.

  20. Fatigue properties and fracture mechanism of load carrying type fillet joints with one-sided welding

    Directory of Open Access Journals (Sweden)

    Takamasa Abe


    Full Text Available The structures of the hydraulic excavator and the crane have numerous one-sided welded joints. However, attachments with box like structures are difficult to weld at both sides. Therefore, high accurate evaluation method is needed. In this study, the fatigue properties and the fracture mechanism of the load carrying type fillet joints with one-sided welding were investigated experimentally to evaluate its fatigue damage with high accuracy based on the experimental results. As the results, fatigue cracks in the test piece initiated from the tip of the unwelded portion and propagated into the welding materials. Multiple welding defects were observed in the unwelded portion, but did not appear to be crack origins. Although these welding defects affected the direction of crack propagation they exerted minimal influence. The three-dimensional observations revealed that fatigue cracks initiate at an early stage of the fatigue development. We infer that the fatigue lifetime is chiefly governed by the crack propagation lifetime. Cracks were initiated at multiple sites in the test piece. As the number of cycles increased, these cracks propagated and combined. So considering the combination of cracks from multiple crack origins is important for a precise evaluation of fatigue damage.

  1. Fatigue properties and fracture mechanism of load carrying type fillet joints with one-sided welding

    Directory of Open Access Journals (Sweden)

    Takamasa Abe


    Full Text Available The structures of the hydraulic excavator and the crane have numerous one-sided welded joints. However, attachments with box like structures are difficult to weld at both sides. Therefore, high accurate evaluation method is needed. In this study, the fatigue properties and the fracture mechanism of the load carrying type fillet joints with one-sided welding were investigated experimentally to evaluate its fatigue damage with high accuracy based on the experimental results. As the results, fatigue cracks in the test piece initiated from the tip of the unwelded portion and propagated into the welding materials. Multiple welding defects were observed in the unwelded portion, but did not appear to be crack origins. Although these welding defects affected the direction of crack propagation they exerted minimal influence. The three-dimensional observations revealed that fatigue cracks initiate at an early stage of the fatigue development. We infer that the fatigue lifetime is chiefly governed by the crack propagation lifetime. Cracks were initiated at multiple sites in the test piece. As the number of cycles increased, these cracks propagated and combined. So considering the combination of cracks from multiple crack origins is important for a precise evaluation of fatigue damage.

  2. Application of CCG Sensors to a High-Temperature Structure Subjected to Thermo-Mechanical Load (United States)

    Xie, Weihua; Meng, Songhe; Jin, Hua; Du, Chong; Wang, Libin; Peng, Tao; Scarpa, Fabrizio; Xu, Chenghai


    This paper presents a simple methodology to perform a high temperature coupled thermo-mechanical test using ultra-high temperature ceramic material specimens (UHTCs), which are equipped with chemical composition gratings sensors (CCGs). The methodology also considers the presence of coupled loading within the response provided by the CCG sensors. The theoretical strain of the UHTCs specimens calculated with this technique shows a maximum relative error of 2.15% between the analytical and experimental data. To further verify the validity of the results from the tests, a Finite Element (FE) model has been developed to simulate the temperature, stress and strain fields within the UHTC structure equipped with the CCG. The results show that the compressive stress exceeds the material strength at the bonding area, and this originates a failure by fracture of the supporting structure in the hot environment. The results related to the strain fields show that the relative error with the experimental data decrease with an increase of temperature. The relative error is less than 15% when the temperature is higher than 200 °C, and only 6.71% at 695 °C. PMID:27754356

  3. Application of CCG Sensors to a High-Temperature Structure Subjected to Thermo-Mechanical Load

    Directory of Open Access Journals (Sweden)

    Weihua Xie


    Full Text Available This paper presents a simple methodology to perform a high temperature coupled thermo-mechanical test using ultra-high temperature ceramic material specimens (UHTCs, which are equipped with chemical composition gratings sensors (CCGs. The methodology also considers the presence of coupled loading within the response provided by the CCG sensors. The theoretical strain of the UHTCs specimens calculated with this technique shows a maximum relative error of 2.15% between the analytical and experimental data. To further verify the validity of the results from the tests, a Finite Element (FE model has been developed to simulate the temperature, stress and strain fields within the UHTC structure equipped with the CCG. The results show that the compressive stress exceeds the material strength at the bonding area, and this originates a failure by fracture of the supporting structure in the hot environment. The results related to the strain fields show that the relative error with the experimental data decrease with an increase of temperature. The relative error is less than 15% when the temperature is higher than 200 °C, and only 6.71% at 695 °C.

  4. Strain Response of the Anterior Cruciate Ligament to Uniplanar and Multiplanar Loads During Simulated Landings: Implications for Injury Mechanism. (United States)

    Kiapour, Ata M; Demetropoulos, Constantine K; Kiapour, Ali; Quatman, Carmen E; Wordeman, Samuel C; Goel, Vijay K; Hewett, Timothy E


    Despite basic characterization of the loading factors that strain the anterior cruciate ligament (ACL), the interrelationship(s) and additive nature of these loads that occur during noncontact ACL injuries remain incompletely characterized. In the presence of an impulsive axial compression, simulating vertical ground-reaction force during landing (1) both knee abduction and internal tibial rotation moments would result in increased peak ACL strain, and (2) a combined multiplanar loading condition, including both knee abduction and internal tibial rotation moments, would increase the peak ACL strain to levels greater than those under uniplanar loading modes alone. Controlled laboratory study. A cadaveric model of landing was used to simulate dynamic landings during a jump in 17 cadaveric lower extremities (age, 45 ± 7 years; 9 female and 8 male). Peak ACL strain was measured in situ and characterized under impulsive axial compression and simulated muscle forces (baseline) followed by addition of anterior tibial shear, knee abduction, and internal tibial rotation loads in both uni- and multiplanar modes, simulating a broad range of landing conditions. The associations between knee rotational kinematics and peak ACL strain levels were further investigated to determine the potential noncontact injury mechanism. Externally applied loads, under both uni- and multiplanar conditions, resulted in consistent increases in peak ACL strain compared with the baseline during simulated landings (by up to 3.5-fold; P ≤ .032). Combined multiplanar loading resulted in the greatest increases in peak ACL strain (P anterior tibial shear force, knee abduction, and internal tibial rotation moments significantly increases ACL strain, which could result in ACL failure. These findings support multiplanar knee valgus collapse as one the primary mechanisms of noncontact ACL injuries during landing. Intervention programs that address multiple planes of loading may decrease the risk of ACL

  5. Effect of graphite loading on the electrical and mechanical properties of Poly (Ethylene Oxide)/Poly (Vinyl Chloride) polymer films (United States)

    Hajar, M. D. S.; Supri, A. G.; Hanif, M. P. M.; Yazid, M. I. M.


    In this study, films consisting of a blend of poly (ethylene oxide)/poly (vinyl chloride) (PEO/PVC) and a conductive filler, graphite were prepared and characterized for their mechanical and electrical properties. Solid polymer blend films based on PEO/PVC (50/50 wt%/wt%) with different graphite loading were prepared by using solution casting technique. Electrical conductivity results discovered the conductivity increased with increasing of filler loading. However, increasing amount of graphite loading led to a decreased in tensile strength and young’s modulus of PEO/PVC/Graphite polymer films. The dispersion of graphite and mechanism of conductive path in the polymer films were also investigated by scanning electron microscopy (SEM). The morphology of the PEO/PVC/Graphite polymer films shows that agglomeration occurred to complete the connection of conductive path, thus improving the conductivity behavior of the polymer films.

  6. Spinal mechanical load as a risk factor for low back pain: a systematic review of prospective cohort studies

    NARCIS (Netherlands)

    Bakker, Eric W. P.; Verhagen, Arianne P.; van Trijffel, Emiel; Lucas, Cees; Koes, Bart W.


    Systematic review. To review and critically evaluate the past literature for spinal mechanical load as risk factor for low back pain (LBP). LBP is a costly health problem worldwide, and treatments are often unsuccessful. Therefore, prevention might be more beneficial in the management of LBP. With

  7. Bonding effectiveness of composite-dentin interfaces after mechanical loading with a new device (Rub&Roll)

    NARCIS (Netherlands)

    Montagner, A.F.; Opdam, N.J.M.; Ruben, J.L.; Cenci, M.S.; Huysmans, M.C.D.N.J.M.


    This study evaluated the effect of mechanical loading with a new device on the microtensile bond strength (microTBS) of adhesive systems to dentin. Forty molars were divided according to adhesive systems: self-etch (ClearfilTM SE Bond -CSE) and etch-and-rinse (Adper ScotchbondTM 1XT -ASB); and to

  8. Opto-mechanical modelling and experimental approach to the measurement of aerospace materials using shearography and thermal loading

    NARCIS (Netherlands)

    Krutul, E.C.; Groves, R.M.


    This paper is concerned with the modelling of the complete opto-mechanical measurement system, including shearography instrument, loading technique and the response of the object under test and the comparison of the simulation results with experimental results. To show the applicability of this

  9. Mechanical analysis of wood-fiber cement sheets under constant and repeated loading (United States)

    Teixeira, Divino Eterno

    Inorganic-bonded panels have been successfully utilized for many years around the world. Cellulose materials are extensively used for cement-bonded particleboard (CBP) and for fiber-reinforced cement (FRC) composites worldwide. Particularly in Europe, this family of composites is used, among other applications, for building construction. Use of wood-fiber cement (WFC) composites in North America has been steadily increasing over the last 10 years. Problems encountered with resin-bonded wood products used in exterior environments have resulted in litigation and search for viable products. WFC sheets are currently filling this need and gaining market share by virtue of their own superior properties. This study was designed to provide basic information currently lacking in literature and important to the wise application of WFC sheets. Experimental autoclaved WFC flat sheets made with kraft Douglas fir fiber and with recycled old corrugated containers (OCC) fiber were manufactured and the results compared with an available commercial product. This experimental program was subdivided into three manuscripts. The first manuscript evaluates whether the actual mechanical properties of WFC sheets can be predicted using nondestructive parameters of the material by applying stress wave time techniques. The second manuscript deals with characterization of the WFC sheets. Physical and mechanical properties were evaluated and results discussed with the use of a scanning electronic microscopic (SEM) analysis. Manuscript three examines the viscoelastic behavior of the material at constant and repeated loading conditions. The nondestructive evaluation (NDE) of the material showed good correlation between dynamic and static modulus of elasticity (MOE). A multivariate linear regression analysis provided the strongest correlation (R = 0.828) for static MOE as a function of wave speed, density, and dynamic MOE. Results from Manuscript 2 revealed that WFC sheets manufactured with

  10. Influence of the Pulse Duration in the Anthropomorphic Test Device (ATD) Lower-Leg Loading Mechanics (United States)


    6 Fig. 7 Velocity histories on the floor plate in FEAs for 10-m/s loading .................................... 6 Fig. 8 Test ...setup for the lower leg loading test with the whole-body ATD and floor mat ........ 7 Fig. 9 Sheets of the butyl rubber as the floor mat on the CSBES... floor plate ............................. 7 Fig. 10 Arrangements of sensors in the test setup

  11. Extending fiber resources : fiber loading recycled fiber and mechanical pulps for lightweight, high opacity paper (United States)

    Marguerite Sykes; John Klungness; Freya Tan; Mathew Stroika; Said Abubakr


    Production of a lightweight, high opacity printing paper is a common goal of papermakers using virgin or recycled fibers. Fiber loading is an innovative, commercially viable process that can substantially upgrade and extend most types of wood fibers. Fiber loading, a process carried out at high consistency and high alkalinity, precipitates calcium carbonate (PCC) in...

  12. Primary gene response to mechanical loading in healing rat Achilles tendons

    DEFF Research Database (Denmark)

    Eliasson, Pernilla; Andersson, Therese; Hammerman, Malin


    Loading can stimulate tendon healing. In healing rat Achilles tendons, we have found more than 150 genes upregulated or downregulated 3 h after one loading episode. We hypothesized that these changes were preceded by a smaller number of regulatory genes and thus performed a microarray 15 min afte...

  13. Mechanical integrity and sustainability of pre-stressed concrete bridge girders repaired by epoxy injection – phase 1. (United States)


    At present, there is a need to assess the mechanical integrity and sustainability of pre-stressed concrete beams during the entire life cycle of the built infrastructure. According to the NCHRP (Tadros et al., 2010), further research to develop fi...

  14. Development and Validation of Mechanical Engineering Trade Skills Assessment Instrument for Sustainable Job Security in Yobe State (United States)

    Adamu, Gishua Garba; Dawha, Josphine Musa; Kamar, Tiamiyu Salihu


    Mechanical Engineering Trade Skills Assessment Instrument (METSAI) is aimed at determining the extent to which students have acquired practical skills before graduation that will enable them get employment for sustainable job security in Yobe state. The study employed instrumentation research design. The populations of the study were 23 mechanical…

  15. Neurite, a finite difference large scale parallel program for the simulation of electrical signal propagation in neurites under mechanical loading.

    Directory of Open Access Journals (Sweden)

    Julián A García-Grajales

    Full Text Available With the growing body of research on traumatic brain injury and spinal cord injury, computational neuroscience has recently focused its modeling efforts on neuronal functional deficits following mechanical loading. However, in most of these efforts, cell damage is generally only characterized by purely mechanistic criteria, functions of quantities such as stress, strain or their corresponding rates. The modeling of functional deficits in neurites as a consequence of macroscopic mechanical insults has been rarely explored. In particular, a quantitative mechanically based model of electrophysiological impairment in neuronal cells, Neurite, has only very recently been proposed. In this paper, we present the implementation details of this model: a finite difference parallel program for simulating electrical signal propagation along neurites under mechanical loading. Following the application of a macroscopic strain at a given strain rate produced by a mechanical insult, Neurite is able to simulate the resulting neuronal electrical signal propagation, and thus the corresponding functional deficits. The simulation of the coupled mechanical and electrophysiological behaviors requires computational expensive calculations that increase in complexity as the network of the simulated cells grows. The solvers implemented in Neurite--explicit and implicit--were therefore parallelized using graphics processing units in order to reduce the burden of the simulation costs of large scale scenarios. Cable Theory and Hodgkin-Huxley models were implemented to account for the electrophysiological passive and active regions of a neurite, respectively, whereas a coupled mechanical model accounting for the neurite mechanical behavior within its surrounding medium was adopted as a link between electrophysiology and mechanics. This paper provides the details of the parallel implementation of Neurite, along with three different application examples: a long myelinated axon

  16. An Independent Review and Accountability Mechanism for the Sustainable Development Goals (United States)


    Abstract The Framework Convention on Global Health (FCGH), a proposed global treaty to be rooted in the right to health and aimed at health equity, could establish a nuanced, layered, and multi-faceted regime of compliance with, and accountability to, the right to health. In so doing, it would significantly strengthen accountability for the health-related Sustainable Development Goals (SDGs), which it would encompass. Legally binding, the FCGH could facilitate accountability through the courts and catalyze comprehensive domestic accountability regimes, requiring national strategies that include transparency, community and national mechanisms for accountability and participation and an enabling environment for social empowerment. A “Right to Health Capacity Fund” could ensure resources to implement these strategies. Inclusive national processes could establish targets, benchmarks, and indicators consistent with FCGH guidance, with regular reporting to a treaty body, which could also hear individual cases. State reports could be required to include plans to overcome implementation gaps, subjecting poorly complying states to penalties and targeted capacity building measures. Regional special rapporteurs could facilitate compliance through regular country visits, while also responding to serious violations. And reaching beyond government compliance, from capacity building to the courts and contractual obligations, the FCGH could establish nationally enforceable right to health obligations on the private sector. PMID:27781005

  17. Lung stress, strain, and energy load: engineering concepts to understand the mechanism of ventilator-induced lung injury (VILI). (United States)

    Nieman, Gary F; Satalin, Joshua; Andrews, Penny; Habashi, Nader M; Gatto, Louis A


    It was recently shown that acute respiratory distress syndrome (ARDS) mortality has not been reduced in over 15 years and remains ~40 %, even with protective low tidal volume (LVt) ventilation. Thus, there is a critical need to develop novel ventilation strategies that will protect the lung and reduce ARDS mortality. Protti et al. have begun to analyze the impact of mechanical ventilation on lung tissue using engineering methods in normal pigs ventilated for 54 h. They used these methods to assess the impact of a mechanical breath on dynamic and static global lung strain and energy load. Strain is the change in lung volume in response to an applied stress (i.e., Tidal Volume-Vt). This study has yielded a number of exciting new concepts including the following: (1) Individual mechanical breath parameters (e.g., Vt or Plateau Pressure) are not directly correlated with VILI but rather any combination of parameters that subject the lung to excessive dynamic strain and energy/power load will cause VILI; (2) all strain is not equal; dynamic strain resulting in a dynamic energy load (i.e., kinetic energy) is more damaging to lung tissue than static strain and energy load (i.e., potential energy); and (3) a critical consideration is not just the size of the Vt but the size of the lung that is being ventilated by this Vt. This key concept merits attention since our current protective ventilation strategies are fixated on the priority of keeping the Vt low. If the lung is fully inflated, a large Vt is not necessarily injurious. In conclusion, using engineering concepts to analyze the impact of the mechanical breath on the lung is a novel new approach to investigate VILI mechanisms and to help design the optimally protective breath. Data generated using these methods have challenged some of the current dogma surrounding the mechanisms of VILI and of the components in the mechanical breath necessary for lung protection.

  18. Cyanobacterial carbon concentrating mechanisms facilitate sustained CO2 depletion in eutrophic lakes

    Directory of Open Access Journals (Sweden)

    A. M. Morales-Williams


    Full Text Available Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO2 depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO3− across their cell membrane when CO2 concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs. To investigate whether CCMs can maintain phytoplankton bloom biomass under CO2 depletion, we measured the δ13C signatures of dissolved inorganic carbon (δ13CDIC and phytoplankton particulate organic carbon (δ13Cphyto in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass–balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO2 stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton δ13C signatures as well as a significant nonlinear negative relationship between water column ρCO2 and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO2 or HCO3− during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO2 drops below atmospheric equilibrium. Our results indicate that active HCO3− uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO2 is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.

  19. Cyanobacterial carbon concentrating mechanisms facilitate sustained CO2 depletion in eutrophic lakes (United States)

    Morales-Williams, Ana M.; Wanamaker, Alan D., Jr.; Downing, John A.


    Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO2 depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO3-) across their cell membrane when CO2 concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO2 depletion, we measured the δ13C signatures of dissolved inorganic carbon (δ13CDIC) and phytoplankton particulate organic carbon (δ13Cphyto) in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass-balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO2 stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton δ13C signatures as well as a significant nonlinear negative relationship between water column ρCO2 and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO2 or HCO3- during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO2 drops below atmospheric equilibrium. Our results indicate that active HCO3- uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO2 is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.

  20. Sustainability in Agricultural Mechanization: Assessment of a Combined Photovoltaic and Electric Multipurpose System for Farmers

    Directory of Open Access Journals (Sweden)

    Toufic El Asmar


    Full Text Available This study is dedicated to the assessment of the possibility of replacing fossil fuels with renewable energy as a source of power in modern agriculture. We examined the use of a completely sustainable agricultural mechanization system based on a renewable energy system and a battery powered, multi-purpose agricultural vehicle. This assessment is based on the RAMseS project, financed by the European Commission under the 6th Framework Program, which has led to the actual manufacturing of the system, at present being tested in Lebanon. In the present study, we assess the environmental and economic performance of the RAMseS system. We evaluate the external costs by means of a specific model that takes into account the life-cycle cost (LCC, economical indexes, and life-cycle emissions for the vehicle during its life span. The results are compared with those of a standard vehicle based on the internal combustion engine (ICEV. The results show that the RAMseS system can avoid the emission of about 23 ton of CO2equ per year. The life cycle cost (LCC assessment using MATLAB software shows that the LCC for the RAMseS vehicle and the ICEV are the same for a fuel unit price (pf of 1.45 €/L. Finally, we show that almost 52 % of the RAMseS LCC is due to the batteries of the electric vehicle. A 50% decrease in batteries unit cost would cause the LCC of two system to be the same at a fuel cost of 0.8 €/L. The final result is that the RAMseS system remains—at present— marginally more expensive than an equivalent system based on conventional fuels and internal combustion engines. Nevertheless, with the gradual depletion of fossil fuels, all electric agricultural mechanized system provide an alternative solution that is dependent only on renewable energy and recyclable resources.

  1. A methodology to incorporate life cycle analysis and the triple bottom line mechanism for sustainable management of industrial enterprises (United States)

    Wang, Ling; Lin, Li


    Since 1970"s, the environmental protection movement has challenged industries to increase their investment in Environmentally Conscious Manufacturing (ECM) techniques and management tools. Social considerations for global citizens and their descendants also motivated the examination on the complex issues of sustainable development beyond the immediate economic impact. Consequently, industrial enterprises have started to understand sustainable development in considering the Triple Bottom Line (TBL): economic prosperity, environmental quality and social justice. For the management, however, a lack of systematic ECM methodologies hinders their effort in planning, evaluating, reporting and auditing of sustainability. To address this critical need, this research develops a framework of a sustainable management system by incorporating a Life Cycle Analysis (LCA) of industrial operations with the TBL mechanism. A TBL metric system with seven sets of indices for the TBL elements and their complex relations is identified for the comprehensive evaluation of a company"s sustainability performance. Utilities of the TBL indices are estimated to represent the views of various stakeholders, including the company, investors, employees and the society at large. Costs of these indices are also captured to reflect the company"s effort in meeting the utilities. An optimization model is formulated to maximize the economic, environmental and social benefits by the company"s effort in developing sustainable strategies. To promote environmental and social consciousness, the methodology can significantly facilitate management decisions by its capabilities of including "non-business" values and external costs that the company has not contemplated before.

  2. Utilizing mechanical loads and flexoelectricity to induce and control complicated evolution of domain patterns in ferroelectric nanofilms (United States)

    Chen, Weijin; Zheng, Yue; Feng, Xue; Wang, Biao


    We have conducted a systematical investigation to reveal the stability and evolution path of various ferroelectric domain patterns in nanofilms subjected to mechanical loads and related flexoelectric field. Within a rigorous framework of flexoelectricity, a phase-field approach has been established for simulating the domain structure of ferroelectric nanofilms. The electromechanical fields of the nanofilms are numerically solved by a fast Fourier transform technique (FFT) based on the combination of Khachaturyan's microscopic elastic theory and Stroh's formalism of anisotropic elasticity. Using this approach, we simulate eight types of domain patterns that can be stabilized in the nanofilms. It is further demonstrated that these domain patterns can be significantly affected by the mechanical loads and related flexoelectric field and exhibit fruitful evolution paths. To adapt the applied mechanical strain and strain gradient, the domain pattern may remain stable, evolve into another polydomain pattern, or become a monodomain state (an effect of domain erasing). The domain fraction, detailed domain morphology, average stresses in the nanofilms, average polarization and temporal evolution characteristics of the domain patterns under various mechanical loads and sources of flexoelectric field have been analyzed. This investigation should provide instructive information for the practical application of ferroelectric nanofilms under complex and changeable mechanical conditions.

  3. Effects of Loading Frequency and Film Thickness on the Mechanical Behavior of Nanoscale TiN Film (United States)

    Liu, Jin-na; Xu, Bin-shi; Wang, Hai-dou; Cui, Xiu-fang; Jin, Guo; Xing, Zhi-guo


    The mechanical properties of a nanoscale-thickness film material determine its reliability and service life. To achieve quantitative detection of film material mechanical performance based on nanoscale mechanical testing methods and to explore the influence of loading frequency of the cycle load on the fatigue test, a TiN film was prepared on monocrystalline silicon by magnetron sputtering. The microstructure of the nanoscale-thickness film material was characterized by using scanning electron microscopy and high-resolution transmission electron microscopy. The residual stress distribution of the thin film was obtained by using an electronic film stress tester. The hardness values and the fatigue behavior were measured by using a nanomechanical tester. Combined with finite element simulation, the paper analyzed the influence of the film thickness and loading frequency on the deformation, as well as the equivalent stress and strain. The results showed that the TiN film was a typical face-centered cubic structure with a large amount of amorphous. The residual compressive stress decreased gradually with increasing thin film thickness, and the influence of the substrate on the elastic modulus and hardness was also reduced. A greater load frequency would accelerate the dynamic fatigue damage that occurs in TiN films.

  4. Organic Nanovesicular Cargoes for Sustained Drug Delivery: Synthesis, Vesicle Formation, Controlling “Pearling” States, and Terfenadine Loading/Release Studies

    Directory of Open Access Journals (Sweden)

    Ajay Kumar Botcha


    Full Text Available “Sustained drug delivery systems” which are designed to accomplish long-lasting therapeutic effect are one of the challenging topics in the area of nanomedicine. We developed an innovative strategy to prepare nontoxic and polymer stabilized organic nanovesicles (diameter: 200 nm from a novel bolaamphiphile, where two hydrogen bonding acetyl cytosine molecules connected to 4,4′′-positions of the 2,6-bispyrazolylpyridine through two flexible octyne chains. The nanovesicles behave like biological membrane by spontaneously self-assembling into “pearl-like” chains and subsequently forming long nanotubes (diameter: 150 nm, which further develop into various types of network-junctions through self-organization. For drug loading and delivery applications, the nanovesicles were externally protected with biocompatible poly(ethyleneglycol-2000 to prevent them from fusion and ensuing tube formation. Nontoxic nature of the nanovesicles was demonstrated by zebrafish teratogenicity assay. Biocompatible nanovesicles were loaded with “terfenadine” drug and successfully utilized to transport and release drug in sustained manner (up to 72 h in zebrafish larvae, which is recognized as an emerging in vivo model system.

  5. Dynamic mechanical loading enhances functional properties of tissue-engineered cartilage using mature canine chondrocytes. (United States)

    Bian, Liming; Fong, Jason V; Lima, Eric G; Stoker, Aaron M; Ateshian, Gerard A; Cook, James L; Hung, Clark T


    The concept of cartilage functional tissue engineering (FTE) has promoted the use of physiologic loading bioreactor systems to cultivate engineered tissues with load-bearing properties. Prior studies have demonstrated that culturing agarose constructs seeded with primary bovine chondrocytes from immature joints, and subjected to dynamic deformation, produced equilibrium compressive properties and proteoglycan content matching the native tissue. In the process of translating these results to an adult canine animal model, it was found that protocols previously successful with immature bovine primary chondrocytes did not produce the same successful outcome when using adult canine primary chondrocytes. The objective of this study was to assess the efficacy of a modified FTE protocol using adult canine chondrocytes seeded in agarose hydrogel and subjected to dynamic loading. Two modes of dynamic loading were applied to constructs using custom bioreactors: unconfined axial compressive deformational loading (DL; 1 Hz, 10% deformation) or sliding contact loading (Slide; 0.5 Hz, 10% deformation). Loading for 3 h daily was initiated on day 0, 14, or 28 (DL0, DL14, DL28, and Slide14). Constructs with applied loading (both DL and Slide) exhibited significant increases in Young's modulus compared with free-swelling control as early as day 28 in culture (p engineered constructs compare favorably with (and exceed in some cases) those of native canine knee (patella groove and condyle) cartilage. Our findings successfully demonstrate an FTE strategy incorporating clinically relevant, adult chondrocytes and gel scaffold for engineering cartilage replacement tissue. These results, using continuous growth factor supplementation, are in contrast to our previously reported studies with immature chondrocytes where the sequential application of dynamic loading after transient transforming growth factor-beta3 application was found to be a superior culture protocol. Sliding, which simulates

  6. Hierarchy of factors exerting an impact on nutrient load of the Baltic Sea and sustainable management of its drainage basin. (United States)

    Kiedrzyńska, Edyta; Jóźwik, Adam; Kiedrzyński, Marcin; Zalewski, Maciej


    The aim of the paper was to evaluate 23 catchment factors that determine total phosphorus and total nitrogen load to the Baltic Sea. Standard correlation analysis and clustering were used. Both phosphorus and nitrogen loads were found to be positively related to the number of pigs and the human population associated with wastewater treatment plants (WWTPs) per km(2), while the number of cattle and agricultural area were found to influence nitrogen rather than phosphorus load, and the area of forests is negatively related to loads of both nutrients. Clustering indicates an overall north-south pattern in the spatial co-occurrence of socio-ecological factors, with some exceptions discussed in the paper. Positive steps in the Baltic Sea region have already been taken, but much remains to be done. The development of coherent response policies to reduce eutrophication in the Baltic Sea should be based on a comprehensive knowledge base, an appropriate information strategy and learning alliance platform in each drainage river catchments. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Electromagnetic and mechanical characteristaion of ITER CS-MC conductors affected by transverse cyclic loading, part 3: mechanical properties

    NARCIS (Netherlands)

    Nijhuis, Arend; Noordman, Niels H.W.; Chevtchenko, O.A.; ten Kate, Herman H.J.; Mitchell, Neil


    The magnetic field and current of a coil wound with a cable-in-conduit conductor causes a transverse force pushing the cable to one side of the conduit. This load causes elastic and plastic deformation with friction as well as heating due to friction. A special cryogenic press has been built to

  8. McKenzie treatment versus mulligan sustained natural apophyseal glides for chronic mechanical low back pain (United States)

    Waqqar, Saira; Shakil-ur-Rehman, Syed; Ahmad, Shakeel


    Background and Objective: Chronic mechanical low back pain is common among different age groups and genders. Different manual therapy techniques combined with exercise therapy and electrotherapy modalities play an important role in its management. Our objective was to compare the effects of McKenzie extension exercisesprogram (EEP) versus Mulligan Sustained Natural Apophyseal Glides (SNAGs) for chronic mechanical low back pain (CMLBP). Methods: This randomized control trial (RCT) was conducted at Riphah Physical Rehabilitation Centre, Pakistan Railways General Hospital Rawalpindi, from 1st July to 31st December 2014. The inclusion criteria was patients of both gender and age range 30-70 years with minimum 4 weeks history of CMLBP. A total of 37 patients were screened out as per inclusion criteria and randomly placed into two groups. Twenty patients in group A were treated with Mulligan SNAGs and 17 patients in group B with McKenzie EEP for four weeks at two session per week and single session per day. Visual Analogue Scale (VAS), Oswestry Disability Scale (ODI) and lumber Range of Motion (ROM) were used as an assessment tools and were measured at baseline and at the completion 4 weeks intervention. The data was analyzed with SPSS to draw the statistical and clinical significance of both interventions. Results: At the completion of 4 weeks intervention the pre and post statistical analysis revealed that clinically the McKenzie EEP improved pain (mean 9.12 to 1.46) and disability (73.82 to 6.24) slightly more than Mulligan SNAGs (pain: from 8.85 to 2.55, disability 73.75 to 7.05), while the Mulligan SNAGs improved lumbar ROM more effectively than McKenzie EEP in all directions including flexion, extension, side bending and rotation. Statistically there was no significant difference between the effects of two interventions in managing pain and disability, and improving Lumber ROM. Conclusion: McKenzie EEP is clinically slightly more effective in the management of pain

  9. McKenzie treatment versus mulligan sustained natural apophyseal glides for chronic mechanical low back pain. (United States)

    Waqqar, Saira; Shakil-Ur-Rehman, Syed; Ahmad, Shakeel


    Chronic mechanical low back pain is common among different age groups and genders. Different manual therapy techniques combined with exercise therapy and electrotherapy modalities play an important role in its management. Our objective was to compare the effects of McKenzie extension exercisesprogram (EEP) versus Mulligan Sustained Natural Apophyseal Glides (SNAGs) for chronic mechanical low back pain (CMLBP). This randomized control trial (RCT) was conducted at Riphah Physical Rehabilitation Centre, Pakistan Railways General Hospital Rawalpindi, from 1(st) July to 31(st) December 2014. The inclusion criteria was patients of both gender and age range 30-70 years with minimum 4 weeks history of CMLBP. A total of 37 patients were screened out as per inclusion criteria and randomly placed into two groups. Twenty patients in group A were treated with Mulligan SNAGs and 17 patients in group B with McKenzie EEP for four weeks at two session per week and single session per day. Visual Analogue Scale (VAS), Oswestry Disability Scale (ODI) and lumber Range of Motion (ROM) were used as an assessment tools and were measured at baseline and at the completion 4 weeks intervention. The data was analyzed with SPSS to draw the statistical and clinical significance of both interventions. At the completion of 4 weeks intervention the pre and post statistical analysis revealed that clinically the McKenzie EEP improved pain (mean 9.12 to 1.46) and disability (73.82 to 6.24) slightly more than Mulligan SNAGs (pain: from 8.85 to 2.55, disability 73.75 to 7.05), while the Mulligan SNAGs improved lumbar ROM more effectively than McKenzie EEP in all directions including flexion, extension, side bending and rotation. Statistically there was no significant difference between the effects of two interventions in managing pain and disability, and improving Lumber ROM. McKenzie EEP is clinically slightly more effective in the management of pain and disability as compared with Mulligan SNAGs

  10. Opto-mechanical modelling and experimental approach to the measurement of aerospace materials using shearography and thermal loading (United States)

    Corso Krutul, Eduardo; Groves, Roger M.


    This paper is concerned with the modelling of the complete opto-mechanical measurement system, including shearography instrument, loading technique and the response of the object under test and the comparison of the simulation results with experimental results. To show the applicability of this technique, the response of an aluminium flat plate sample under thermal load was analysed. First a finite element model of the plate was generated, using an experimentally measured temperature profile. The strain and displacement values obtained from the finite element model were used to simulate the phase-map in the optical part of the model. The simulated phase maps were then compared qualitatively with experimental phase maps measured using shearography. This approach is suitable to understand the response of components under load and to predict anomalies such as defects, thereby making the analysis of measured phase maps easier and less empirical.

  11. Kenaf/PP and EFB/PP: Effect of fibre loading on the mechanical properties of polypropylene composites (United States)

    Anuar, N. I. S.; Zakaria, S.; Harun, J.; Wang, C.


    Kenaf and empty fruit bunch (EFB) fibre which are the important natural fibres in Malaysia were studied as nonwoven polymer composites. The effect of fibre loading on kenaf polypropylene and EFB polypropylene nonwoven composite was studied at different mixture ratio. Kenaf polypropylene nonwoven composite (KPNC) and EFB polypropylene nonwoven composite (EPNC) were prepared by carding and needle-punching techniques, followed by a compression moulding at 6 mm thickness. This study was conducted to identify the optimum fibre loading of nonwoven polypropylene composite and their effect on the mechanical strength. The study was designed at 40%, 50%, 60% and 70% of fibre content in nonwoven mat and composite. The tensile strength, flexural strength and compression strength were tested to evaluate the composite mechanical properties. It was found that the mechanical properties for both kenaf and EFB nonwoven composites were influenced by the fibre content. KPNC showed higher mechanical strength than EPNC. The highest flexural strength was obtained at 60% KPNC and the lowest value was showed by 40% EPNC. The tensile and flexural strength for both KPNC and EPNC decreased after the fibre loading of 60%.

  12. Mechanisms of sustaining a radio-frequency atmospheric pressure planar discharge (United States)

    Wang, Lei; Dinescu, Gheorghe; Deng, Xiaolong; Ionita, Eusebiu-Rosini; Leys, Christophe; Nikiforov, Anton Yu


    The time behavior of an atmospheric pressure planar discharge sustained in He gas was investigated experimentally and through two dimensional (2D) discharge simulation. The 30 mm long uniform α-mode discharge was observed at radio frequency (RF) input power below 35 W. The gas temperature of 375 ± 50 K in the discharge core was estimated by emission spectroscopy of OH(A-X) emission. A sheath region of about 100-150 μm width near both electrodes was observed during the whole RF cycle. However, there were differences in emission dynamics among various species detected in the discharge. OH(A) emission does not follow the RF voltage temporal variation. Strong He emission was always detected near the cathode, which was consistent with the 2D discharge simulation results. He-excited species production was found mainly due to the electron impact process. The simulation showed that both the electron and ion density vary from 1.88 × 1017 m-3 to 1.92 × 1017 m-3, and the electron temperature was about 1.85 eV in the plasma bulk. The ion temperature stayed close to the rotational temperature of OH radicals, and only increased near the sheath region to 0.65 eV. It was found that the mechanism of the sheath formation in atmospheric pressure discharge strongly correlates with the dynamics of the electron density and electron temperature variation in the gap, and the process is similar to low pressure RF capacitively coupled discharges. The high uniformity of the discharge and the upscale possibility to any desirable size are considered beneficial for industrial applications of the source, which is key for processes of thin coating deposition and polymer modification.

  13. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions.

    Directory of Open Access Journals (Sweden)

    Petra S Williams

    Full Text Available In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks. On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS, paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min than the position-matching task (26.9 ± 15.11 min; p0.05. Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10 and an index of upstream excitation of the motor cortex remained constant (p>0.40. Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.

  14. Cortical and Spinal Mechanisms of Task Failure of Sustained Submaximal Fatiguing Contractions (United States)

    Williams, Petra S.; Hoffman, Richard L.; Clark, Brian C.


    In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2–3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5±7.9 min) than the position-matching task (26.9±15.11 min; pmuscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure. PMID:24667484

  15. Sustainable mechanical biological treatment of solid waste in urbanized areas with low recycling rates. (United States)

    Trulli, Ettore; Ferronato, Navarro; Torretta, Vincenzo; Piscitelli, Massimiliano; Masi, Salvatore; Mancini, Ignazio


    Landfill is still the main technological facility used to treat and dispose municipal solid waste (MSW) worldwide. In developing countries, final dumping is applied without environmental monitoring and soil protection since solid waste is mostly sent to open dump sites while, in Europe, landfilling is considered as the last option since reverse logistic approaches or energy recovery are generally encouraged. However, many regions within the European Union continue to dispose of MSW to landfill, since modern facilities have not been introduced owing to unreliable regulations or financial sustainability. In this paper, final disposal activities and pre-treatment operations in an area in southern Italy are discussed, where final disposal is still the main option for treating MSW and the recycling rate is still low. Mechanical biological treatment (MBT) facilities are examined in order to evaluate the organic stabilization practices applied for MSW and the efficiencies in refuse derived fuel production, organic waste stabilization and mass reduction. Implementing MBT before landfilling the environmental impact and waste mass are reduced, up to 30%, since organic fractions are stabilized resulting an oxygen uptake rate less than 1600 mgO2 h-1 kg-1VS, and inorganic materials are exploited. Based on experimental data, this work examines MBT application in contexts where recycling and recovery activities have not been fully developed. The evidence of this study led to state that the introduction of MBT facilities is recommended for developing regions with high putrescible waste production in order to decrease environmental pollution and enhance human healthy. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Hydroxy double salts loaded with bioactive ions: Synthesis, intercalation mechanisms, and functional performance

    Energy Technology Data Exchange (ETDEWEB)

    Kaassis, Abdessamad Y.A. [UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX (United Kingdom); Xu, Si-Min; Guan, Shanyue; Evans, David G. [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Wei, Min, E-mail: [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Williams, Gareth R., E-mail: [UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX (United Kingdom)


    The intercalation of the anions of diclofenac (Dic), naproxen (Nap), and valproic acid (Val) into three hydroxy double salts (HDSs) has been explored in this work. Experiments were performed with [Co{sub 1.2}Zn{sub 3.8}(OH){sub 8}](NO{sub 3}){sub 2}·2H{sub 2}O (CoZn-NO{sub 3}), [Ni{sub 2}Zn{sub 3}(OH){sub 8}](NO{sub 3}){sub 2}·2H{sub 2}O (NiZn-NO{sub 3}) and [Zn{sub 5}(OH){sub 8}](NO{sub 3}){sub 2}·2H{sub 2}O (Zn-NO{sub 3}). It proved possible to intercalate diclofenac and naproxen into all three HDSs. In contrast, Val could be intercalated into CoZn-NO{sub 3} but when it was reacted with Zn-NO{sub 3} the HDS structure was destroyed, and the product comprised ZnO. Successful intercalation was verified by X-ray diffraction, IR spectroscopy, and elemental microanalysis. Molecular dynamics simulations showed the Dic and Nap ions to arrange themselves in an “X” shape in the interlayer space, forming a bilayer. Val was found to adopt a position with its aliphatic groups parallel to the HDS layer, again in a bilayer. In situ time resolved X-ray diffraction experiments revealed that intercalation of Dic and Nap into CoZn-NO{sub 3} and Zn-NO{sub 3} is mechanistically complex, with a number of intermediate phases observed. In contrast, the intercalation of all three guests into NiZn-NO{sub 3} and of Val into CoZn-NO{sub 3} are simple one step reactions proceeding directly from the starting material to the product. The HDS-drug composites were found to have sustained release profiles. - Graphical abstract: Seven new drug intercalates of hydroxy double salts (HDSs) have been prepared and characterised. The intercalation mechanisms have been explored, and the drug release properties of the HDS/drug composites quantified. Display Omitted.

  17. Development of a novel sodium fusidate-loaded triple polymer hydrogel wound dressing: Mechanical properties and effects on wound repair. (United States)

    Jin, Sung Giu; Kim, Kyeong Soo; Kim, Dong Wuk; Kim, Dong Shik; Seo, Youn Gee; Go, Toe Gyung; Youn, Yu Seok; Kim, Jong Oh; Yong, Chul Soon; Choi, Han-Gon


    To develop a novel sodium fusidate-loaded triple polymer hydrogel dressing (TPHD), numerious polyvinyl alcohol-based (PVA) hydrogel dressings were prepared with various hydrophilic polymers using the freeze-thaw method, and their hydrogel dressing properties were assessed. Among the hydrophilic polymers tested, sodium alginate (SA) improved the swelling capacity the most, and polyvinyl pyrrolidone (PVP) provided the greatest improvement in bioadhesive stength and mechanical properties. Thus, PVA based-TPHDs were prepared using different ratios of PVP:SA. The effect of selected PVP:SA ratios on the swelling capacity, bioadhesive strength, mechanical properties, and drug release, permeation and deposition characteristics of sodium fusidate-loaded PVA-based TPHDs were assessed. As the ratio of PVP:SA increased in PVA-loaded TPHD, the swelling capacity, mechanical properties, drug release, permeation and deposition were improved. The TPHD containing PVA, PVP, SA and sodium fusidate at the weight ratio of 10/6/1/1 showed excellent hydrogel dressing properties, release, permeation and deposition of drug. Within 24h, 71.8 ± 1.3% of drug was released. It permeated 625.1 ± 81.2 μg/cm(2) through the skin and deposited of 313.8 ± 24.1 μg/cm(2) within 24h. The results of in vivo pharmacodynamic studies showed that sodium fusidate-loaded TPHD was more effective in improving the repair process than was a commercial product. Thus, this sodium fusidate-loaded TPHD could be a novel tool in wound care. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Exploring canopy structure and function as a potential mechanism of sustain carbon sequestration in aging forests (United States)

    Fotis, A. T.; Curtis, P.; Ricart, R.


    The notion that old-growth forests reach carbon neutrality has recently been challenged, but the mechanisms responsible for continued productivity have remained elusive. Increases in canopy structural complexity, defined by high horizontal and vertical variability in leaf distribution (rugosity), has been proposed as a mechanism for sustained high rates of above ground net primary production (ANPPw) in forests up to ~170 years by enhancing light use efficiency (LUE) and nitrogen use efficiency (NUE). However, a detailed understanding of how rugosity affects resource distribution within and among trees leading to greater LUE and NUE is not known. We propose that leaves in high rugosity plots receive greater photosynthetic photon flux density (PPFD) than leaves in low rugosity plots, causing shifts from shade- to sun- adapted leaves into deeper portions of the canopy, which is thought to increase the photosynthetic capacity of individuals and lead to higher carbon assimilation in forests. The goal of this research was to: 1) quantify different canopy structural characteristics using a portable canopy LiDAR (PCL) and; 2) assess how these structural characteristics affect resource distribution and subsequent changes in leaf morphological, physiological and biochemical traits in three broadleaf species (e.g., Acer rubrum, Quercus rubra and Fagus grandifolia) and one conifer species (e.g., Pinus strobus) at different levels in the canopy in plots with similar leaf are index (LAI) but highly contrasting rugosity levels. We found that gap fraction had a strong positive correlation with rugosity. High rugosity plots had a bimodal distribution of LAI that was concentrated at the top and bottom of the canopy with an open midstory (between 10-50% of total canopy height) whereas low rugosity plots had a more even distribution of leaves. Leaf mass per area (LMA) of all broadleaved species had a strong positive correlation with cumulative gap fraction (P. strobus had a relatively

  19. Mechanical properties, skin permeation and in vivo evaluations of dexibuprofen-loaded emulsion gel for topical delivery. (United States)

    Jin, Sung Giu; Yousaf, Abid Mehmood; Son, Mi Woon; Jang, Sun Woo; Kim, Dong Wuk; Kim, Jong Oh; Yong, Chul Soon; Kim, Jeong Hoon; Choi, Han-Gon


    The aim of this research was to evaluate the gel properties, skin permeation and in vivo drug efficacy of a novel dexibuprofen-loaded emulsion gel for topical delivery. In this study, the dexibuprofen-loaded emulsion gel and ibuprofen-loaded emulsion gel were prepared with isopropanol, Tween 80, propylene glycol, isopropyl myristate and carbopol. Their mechanical properties such as hardness and adhesiveness were assessed. Moreover, their skin permeation, anti-inflammatory and anti-nociceptive efficacy were evaluated using Franz diffusion cell with the hairless mouse skin, the carrageenan-induced paw oedema test and paw pressure test in rat's hind paws compared with the commercial hydrogel, respectively. The dexibuprofen emulsion gel and ibuprofen emulsion gel provided significantly higher hardness and adhesiveness than the commercial hydrogel. The dexibuprofen emulsion gel enhanced skin permeability by about twofold and 3.5-fold without lag time compared to the ibuprofen emulsion gel and the commercial hydrogel, respectively, suggesting its faster skin permeation. Moreover, the anti-inflammatory efficacy and alleviation in carrageenan-induced inflammation was in the order of dexibuprofen emulsion gel > commercial hydrogel > ibuprofen emulsion gel. The dexibuprofen emulsion gel furnished significantly higher nociceptive thresholds than the ibuprofen emulsion gel and the commercial hydrogel, leading to the most improved anti-nociceptive efficacy. Thus, this dexibuprofen-loaded emulsion gel with good mechanical property, rapid skin permeation and excellent anti-inflammatory and anti-nociceptive efficacy would be a strong candidate for the topical delivery of anti-inflammatory dexibuprofen.

  20. Quercetagetin-Loaded Zein-Propylene Glycol Alginate Ternary Composite Particles Induced by Calcium Ions: Structure Characterization and Formation Mechanism. (United States)

    Sun, Cuixia; Wei, Yang; Li, Ruirui; Dai, Lei; Gao, Yanxiang


    The complexation of zein and propylene glycol alginate (PGA) was confirmed to improve the entrapment efficiency and loading capacity of quercetagetin (Q) in our previous study. The present work focused on the influence and induction mechanism of calcium ions on structures of Q-loaded zein-PGA ternary composite particles. The incorporation of Ca 2+ resulted in the formation of aggregates with a large dimension between zein particles, led to obvious conformational, secondary, and tertiary structural changes of zein, and caused the disappearance of crystalline structure of zein. PGA exhibited a fine filamentous network structure and became much thicker and stronger in the presence of Ca 2+ . The presence of Q promoted the affinity and binding capacity of Ca 2+ to zein and PGA. An interwoven network structure with enhanced firmness and density was observed in Q-loaded zein-PGA composite particles, leading to improved thermal stability. Three potential mechanisms were proposed to explain the structural characteristics induced by Ca 2+ , including particle-particle collision for zein particles, chain-chain association for PGA molecules, and simultaneous cross-linking coupled with aggregating for Q-loaded zein-PGA composite particles.

  1. The functional role of the ischiopubic membrane for the mechanical loading of the pubis in the domestic fowl (Gallus gallus) (United States)

    Fechner, Regina; Stratmann, Matthias; Gößling, Rainer; Sverdlova, Nina


    Soft tissues other than muscles are supposed to be of mechanical importance, yet they are rarely integrated into finite element models. Here, we investigate the functional role of the ischiopubic membrane for the loading of the pubis of the domestic fowl using 2D finite element analysis. For this purpose, a specimen of the domestic fowl was dissected and soft tissues attaching to the pubis were studied in great detail. Muscles were removed and measurements taken. For the 2D finite element model, the outline was taken from the dissected specimen. Two 2D finite element models were generated: one without and one with ischiopubic membrane. The same muscular loading based on own measurements and electromyographic data was applied to both models. The model without ischiopubic membrane shows anteroventral bending deformation of the scapus pubis, resulting in high compressive and tensile principal stresses at the level of ultimate bone stress values. The model with ischiopubic membrane shows low compressive principal stresses in the pubis consistent with the levels of steady state remodelling of bone. Based on these results, the ischiopubic membrane of the domestic fowl potentially establishes a physiological loading of the pubis and therefore might be of great mechanical significance for the loading of the bone. PMID:23171269

  2. The deformation and acoustic emission of aluminum-magnesium alloy under non-isothermal thermo-mechanical loading

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, S. V.; Plotnikov, V. A., E-mail:; Lysikov, M. V. [Altai State University, Barnaul, 656049 (Russian Federation); Kolubaev, E. A., E-mail: [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)


    The following study investigates the deformation behavior and acoustic emission in aluminum-magnesium alloy under conditions of non-isothermal thermo-mechanical loading. The accumulation of deformation in the alloy, in conditions of change from room temperature to 500°C, occurs in two temperature intervals (I, II), characterized by different rates of deformation. The rate of deformation accumulation is correlated with acoustic emission. With load increasing in cycles from 40 to 200 MPa, the value of the boundary temperature (T{sub b}) between intervals I and II changes non-monotonically. In cycles with load up to 90 MPa, the T{sub b} value increases, while an increase up to 200 MPa makes T{sub b} shift toward lower temperatures. This suggests that the shift of boundaries in the region of low temperatures and the appearance of high-amplitude pulses of acoustic emission characterize the decrease of the magnitude of thermal fluctuations with increasing mechanical load, leading to the rupture of interatomic bonds in an elementary deformation act.

  3. A model for the excitation of osteocytes by mechanical loading-induced bone fluid shear stresses. (United States)

    Weinbaum, S; Cowin, S C; Zeng, Y


    A new experimentally testable hypothesis is advanced for the mechanosensory transduction mechanism by which communicating osteocytes sense the very small in vivo strains in the calcified matrix components of bone. We propose that the osteocytes, although not responsive to substantial fluid pressures, can be stimulated by relatively small fluid shear stresses acting on the membranes of their osteocytic processes. Biot's porous media theory is used to relate the combined axial and bending loads applied to a whole bone to the flow past the osteocytic processes in their canaliculi. In this theory, the bone pores of interest are the proteoglycan filled fluid annuli that surround the osteocytic processes in the canaliculi. We show that previously predicted fluid pore pressure relaxation times were a hundred-fold too short for the lacunar-canalicular porosity because they neglected the fluid drag associated with proteoglycan matrix on the surface membrane of the osteocyte and its cell processes. The recent theory developed in Tsay and Weinbaum [J. Fluid Mech. 226, 125-148 (1991)] for flow through cross-linked fiber filled channels is used to model the flow through this proteoglycan matrix. The predicted pore relaxation time, 1-2 s, closely corresponds to the times measured by Salzstein and Pollack [J. Biomechanics 20, 271-280 (1987)]. Furthermore, using this model, the magnitude of the predicted fluid induced shear stresses, 8-30 dyn cm-2, is shown to be similar to the fluid shear stresses measured in osteoblasts and other cells in which an intracellular Ca2+ shear stress response had been observed. This model is also used, in conjunction with anatomical data and the pore fluid pressure relaxation time data, to show that the spacing between the fibers is approximately 7 nm. The result is consistent with the notion that the canalicular pore space is filled with glycosaminoglycans that are ordered by albumin according to the model of Michel [J. Physiol. 404, 1-29 (1988

  4. Influence of Rapid Freeze-Thaw Cycling on the Mechanical Properties of Sustainable Strain-Hardening Cement Composite (2SHCC

    Directory of Open Access Journals (Sweden)

    Seok-Joon Jang


    Full Text Available This paper provides experimental results to investigate the mechanical properties of sustainable strain-hardening cement composite (2SHCC for infrastructures after freeze-thaw actions. To improve the sustainability of SHCC materials in this study, high energy-consumptive components—silica sand, cement, and polyvinyl alcohol (PVA fibers—in the conventional SHCC materials are partially replaced with recycled materials such as recycled sand, fly ash, and polyethylene terephthalate (PET fibers, respectively. To investigate the mechanical properties of green SHCC that contains recycled materials, the cement, PVA fiber and silica sand were replaced with 10% fly ash, 25% PET fiber, and 10% recycled aggregate based on preliminary experimental results for the development of 2SHCC material, respectively. The dynamic modulus of elasticity and weight for 2SHCC material were measured at every 30 cycles of freeze-thaw. The effects of freeze-thaw cycles on the mechanical properties of sustainable SHCC are evaluated by conducting compressive tests, four-point flexural tests, direct tensile tests and prism splitting tests after 90, 180, and 300 cycles of rapid freeze-thaw. Freeze-thaw testing was conducted according to ASTM C 666 Procedure A. Test results show that after 300 cycles of freezing and thawing actions, the dynamic modulus of elasticity and mass loss of damaged 2SHCC were similar to those of virgin 2SHCC, while the freeze-thaw cycles influence mechanical properties of the 2SHCC material except for compressive behavior.

  5. Mechanical Loads Test Report for the U.S. Department of Energy 1.5-Megawatt Wind Turbine

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Rick [Santos Wind Engineering Technologies, Inc., Portland, ME (United States); van Dam, Jeroen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)


    The objective of the test was to obtain a baseline characterization of the mechanical loads of the DOE 1.5 wind turbine located at NREL. The test was conducted in accordance with the International Electrotechnical Commission (IEC) Technical Specification, IEC 61400-13 Wind Turbine Generator Systems – Part 13: Measurement of mechanical loads; First Edition 2001-06 [1]. The National Wind Technology Center (NWTC) at NREL conducted this test in accordance with its quality system procedures so that the final test report meets the full requirements of its accreditation by the American Association for Laboratory Accreditation (A2LA). NREL’s quality system requires that all applicable requirements specified by A2LA and International Standards Organization/IEC 17025 be met or to note any exceptions in the test report.

  6. Mechanical property evaluation of apricot fruits under quasi-static and dynamic loading

    Directory of Open Access Journals (Sweden)

    E Ahmadi


    Full Text Available Introduction: Some forces and impacts that occur during transporting and handling can reduce the apricot quality. Bruise damage is a major cause of fruit quality loss. Bruises occur under dynamic and static loading when stress induced in the fruit exceeds the failure stress of the fruit tissue. Needless to say that physical and mechanical properties of fruits in the design and optimization of systems related to production, processing and packaging of the products are important. Harvesting, transport, packaging and transportation of fruits and vegetables, result in their bruising which can cause loss of marketability of the fruit by consumers. The term of ‘absorbed energy’ could be used to express the quantity of damage done on the fruit and the high the absorbed energy, the higher the damage on the fruit. The object of this research was due to the importance of apricot fruit and lack of information about the mechanical behavior. Materials and Methods: In this study, apricot fruit variety “Ziaolmolki” was examined to determine some physical and mechanical properties. In order avoid any damage, the fruits were carefully harvested from trees and gathered in plastic boxes in a row, to prevent damage to the apricots. For determination of mechanical properties and levels of impact energy used test axial machine and pendulum device, respectively. Dependent variables (acoustics stiffness, radius of curvature, color characteristic a* and b*, Brix percentage, penetration force, penetration work and penetration deformation and independent variables (impact energy in three levels, temperature and color in 2 levels each were selected and analyzed by block designs with factorial structure. In the experimental design, the fruits were stored in two temperature levels, 3oC and 25oC. Two areas of any fruit (red and yellow areas were subjected to 3 impact energy levels. For each of the 8 levels, 8 fruit samples were selected. Overall, 96 fruits {8 (number

  7. Capturing the Energy Absorbing Mechanisms of Composite Structures under Crash Loading (United States)

    Wade, Bonnie

    As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crashworthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crashworthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of

  8. Rapid increases in training load affects markers of skeletal muscle damage and mechanical performance

    DEFF Research Database (Denmark)

    Kamandulis, Sigitas; Snieckus, Audrius; Venckunas, Tomas


    a program involving a rapid stepwise increase in the number of jumps, drop height, and squat depth, and the addition of weight. Concentric, isometric maximal voluntary contraction (MVC), and stimulated knee extension torque were measured before and 10 min after each session. Muscle soreness and plasma...... creatine kinase activity were assessed after each session. Steep increments in stretch-shortening exercise load in sessions 4 and 7 amplified the postexercise decrease in stimulated muscle torque and slightly increased muscle soreness but had a minimal effect on the recovery of MVC and stimulated torque......The aim of the present study was to monitor the changes in indirect markers of muscle damage during 3 weeks (nine training sessions) of stretch-shortening (drop jump) exercise with constant load alternated with steep increases in load. Physically active men (n = 9, mean age 19.1 years) performed...

  9. Analysis of shell-type structures subjected to time-dependent mechanical and thermal loading (United States)

    Simitses, G. J.


    The objective is to develop a general mathematical model and solution methodologies for analyzing structural response of thin, metallic shell-type structures under large transient, cyclic, or static thermomechanical loads. Among the system responses, which are associated with these load conditions, are thermal buckling, creep buckling, and racheting. Thus, geometric as well as material-type nonlinearities (of high order) can be anticipated and must be considered in the development of the mathematical model. Furthermore, this must also be accommodated in the solution procedures.

  10. A novel bioreactor system for biaxial mechanical loading enhances the properties of tissue-engineered human cartilage. (United States)

    Meinert, Christoph; Schrobback, Karsten; Hutmacher, Dietmar W; Klein, Travis J


    The ex vivo engineering of autologous cartilage tissues has the potential to revolutionize the clinical management of joint disorders. Yet, high manufacturing costs and variable outcomes associated with tissue-engineered implants are still limiting their application. To improve clinical outcomes and facilitate a wider use of engineered tissues, automated bioreactor systems capable of enhancing and monitoring neotissues are required. Here, we developed an innovative system capable of applying precise uni- or biaxial mechanical stimulation to developing cartilage neotissues in a tightly controlled and automated fashion. The bioreactor allows for simple control over the loading parameters with a user-friendly graphical interface and is equipped with a load cell for monitoring tissue maturation. Applying our bioreactor, we demonstrate that human articular chondrocytes encapsulated in hydrogels composed of gelatin methacryloyl (GelMA) and hyaluronic acid methacrylate (HAMA) respond to uni- and biaxial mechanical stimulation by upregulation of hyaline cartilage-specific marker genes. We further demonstrate that intermittent biaxial mechanostimulation enhances accumulation of hyaline cartilage-specific extracellular matrix. Our study underlines the stimulatory effects of mechanical loading on the biosynthetic activity of human chondrocytes in engineered constructs and the need for easy-to-use, automated bioreactor systems in cartilage tissue engineering.

  11. Suzuki-Miyaura cross-coupling coupling reactions with low catalyst loading: A green and sustainable protocol in pure water

    KAUST Repository

    Fihri, Aziz


    The Suzuki-Miyaura coupling reaction represents one of the most important synthetic transformations developed in the 20th century. However, the use of toxic organic solvents remains a scientific challenge and an aspect of economical and ecological relevance, and benign water as a reaction medium was found to be highly effective to overcome some of these issues. In the present manuscript, we described Suzuki-Miyaura coupling reactions in neat water, without using any phase transfer reagent. Notably, this protocol also works with ultra-low loading of catalyst with high turnover numbers and also able to couple challenging substrates like aryl chlorides. © 2011 The Royal Society of Chemistry.

  12. Dependence of Some Mechanical Properties of Elastic Bands on the Length and Load Time (United States)

    Triana, C. A.; Fajardo, F.


    We present a study of the maximum stress supported by elastics bands of nitrile as a function of the natural length and the load time. The maximum tension of rupture and the corresponding variation in length were found by measuring the elongation of an elastic band when a mass is suspended from its free end until it reaches the breaking point. The…

  13. Damage of rat liver tissue caused by repeated and sustained +Gz exposure and the mechanism thereof

    Directory of Open Access Journals (Sweden)

    Wen-bing LI


    Full Text Available Objective  To explore the mechanisms of positive acceleration (+Gz on the damage of rat liver tissue and the effect of +Gz on the expression of JNK/c-Jun in liver cells. Methods  Twenty four male Wistar rats were randomly divided into 4 groups (n=6: control, +2Gz, +6Gz and +10Gz group. With prone position, the rats in control group were fixed to the turning arm of centrifuge with head towards the axis for 5 minutes. The fixation method in +2Gz, +6Gz and +10Gz group was the same as in the control group. The increase rate of acceleration was 1G/s with a peak-time of 3 minutes, and each +Gz exposure repeated 5 times with an interval of 30 minutes. HE staining was used to observe the morphological changes of liver tissue, fluorescence real-time quantitative PCR to detect the expression of hepatic c-Jun mRNA, and Western blotting to detect the hepatic protein expression of p-c-Jun, c-Jun, p-JNK and JNK. Plasma aspartate aminotransferase (AST and alanine aminotransferase (ALT were determined. Results  The levels of serum ALT and AST increased significantly in +6Gz and, especially, the +10Gz group than in control group and +2Gz group (P<0.05. The same situation also existed in the increase of c-Jun mRNA expression (P<0.05. Hepatic c-jun and p-c-Jun (c-Jun activated form protein expression increased with the increase of G value. Compared with control group, no change was found in JNK protein expression in the other three groups, but the expression of p-JNK (activated form of JNK increased in +6Gz and +10Gz groups (P<0.05. HE staining showed the disorganized liver cells with irregular shapes, the unclear cell gap and the vacuolar changes in +6Gz and +10Gz groups. Conclusions  Repeated and sustained +Gz may cause enhanced expression of c-Jun/ p-c-Jun and p-JNK in hepatic cells. JNK/c-Jun signaling pathway may play an important role in the process of hepatic stress injury. DOI: 10.11855/j.issn.0577-7402.2014.03.15

  14. Study of the damaging mechanisms of a copper / carbon - carbon composite under thermomechanical loading; Etude des mecanismes d'endommagement d'un assemblage cuivre / composite carbone - carbone sous chargement thermomecanique

    Energy Technology Data Exchange (ETDEWEB)

    Moncel, L


    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterization. (author)

  15. Study of the damaging mechanisms of a carbon - carbon composite bonded to copper under thermomechanical loading; Etude des mecanismes d'endommagement d'un assemblage cuivre / composite carbone - carbone sous chargement thermomecanique

    Energy Technology Data Exchange (ETDEWEB)

    Moncel, L


    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM 2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterisation. (author)

  16. Interferon Alpha Induces Sustained Changes in NK Cell Responsiveness to Hepatitis B Viral Load Suppression In Vivo.

    Directory of Open Access Journals (Sweden)

    Upkar S Gill


    Full Text Available NK cells are important antiviral effectors, highly enriched in the liver, with the potential to regulate immunopathogenesis in persistent viral infections. Here we examined whether changes in the NK pool are induced when patients with eAg-positive CHB are 'primed' with PegIFNα and importantly, whether these changes are sustained or further modulated long-term after switching to nucleos(tides (sequential NUC therapy, an approach currently tested in the clinic. Longitudinal sampling of a prospectively recruited cohort of patients with eAg+CHB showed that the cumulative expansion of CD56bright NK cells driven by 48-weeks of PegIFNα was maintained at higher than baseline levels throughout the subsequent 9 months of sequential NUCs. Unexpectedly, PegIFNα-expanded NK cells showed further augmentation in their expression of the activating NK cell receptors NKp30 and NKp46 during sequential NUCs. The expansion in proliferating, functional NK cells was more pronounced following sequential NUCs than in comparison cohorts of patients treated with de novo NUCs or PegIFNα only. Reduction in circulating HBsAg concentrations, a key goal in the path towards functional cure of CHB, was only achieved in those patients with enhancement of NK cell IFNγ and cytotoxicity but decrease in their expression of the death ligand TRAIL. In summary, we conclude that PegIFNα priming can expand a population of functional NK cells with an altered responsiveness to subsequent antiviral suppression by NUCs. Patients on sequential NUCs with a distinct NK cell profile show a decline in HBsAg, providing mechanistic insights for the further optimisation of treatment strategies to achieve sustained responses in CHB.

  17. Study of the Mechanical Environment of Chondrocytes in Articular Cartilage Defects Repaired Area under Cyclic Compressive Loading

    Directory of Open Access Journals (Sweden)

    Hai-Ying Liu


    Full Text Available COMSOL finite element software was used to establish a solid-liquid coupling biphasic model of articular cartilage and a microscopic model of chondrocytes, using modeling to take into account the shape and number of chondrocytes in cartilage lacuna in each layer. The effects of cyclic loading at different frequencies on the micromechanical environment of chondrocytes in different regions of the cartilage were studied. The results showed that low frequency loading can cause stress concentration of superficial chondrocytes. Moreover, along with increased frequency, the maximum value of stress response curve of chondrocytes decreased, while the minimum value increased. When the frequency was greater than 0.2 Hz, the extreme value stress of response curve tended to be constant. Cyclic loading had a large influence on the distribution of liquid pressure in chondrocytes in the middle and deep layers. The concentration of fluid pressure changed alternately from intracellular to peripheral in the middle layer. Both the range of liquid pressure in the upper chondrocytes and the maximum value of liquid pressure in the lower chondrocytes in the same lacunae varied greatly in the deep layer. At the same loading frequency, the elastic modulus of artificial cartilage had little effect on the mechanical environment of chondrocytes.

  18. Physiological and molecular mechanisms mediating xylem Na(+) loading in barley in the context of salinity stress tolerance. (United States)

    Zhu, Min; Zhou, Meixue; Shabala, Lana; Shabala, Sergey


    Time-dependent kinetics of xylem Na(+) loading was investigated using a large number of barley genotypes contrasting in their salinity tolerance. Salt-sensitive varieties were less efficient in controlling xylem Na(+) loading and showed a gradual increase in the xylem Na(+) content over the time. To understand underlying ionic and molecular mechanisms, net fluxes of Ca(2+) , K(+) and Na(+) were measured from the xylem parenchyma tissue in response to H2 O2 and ABA; both of them associated with salinity stress signalling. Our results indicate that NADPH oxidase-mediated apoplastic H2 O2 production acts upstream of the xylem Na(+) loading and is causally related to ROS-inducible Ca(2+) uptake systems in the root stelar tissue. It was also found that ABA regulates (directly or indirectly) the process of Na(+) retrieval from the xylem and the significant reduction of Na(+) and K(+) fluxes induced by bumetanide are indicative of a major role of chloride cation co-transporter (CCC) on xylem ion loading. Transcript levels of HvHKT1;5_like and HvSOS1_like genes in the root stele were observed to decrease after salt stress, while there was an increase in HvSKOR_like gene, indicating that these ion transporters are involved in primary Na(+) /K(+) movement into/out of xylem. © 2016 John Wiley & Sons Ltd.

  19. Silver nanoparticles-loaded activated carbon fibers using chitosan as binding agent: Preparation, mechanism, and their antibacterial activity (United States)

    Tang, Chengli; Hu, Dongmei; Cao, Qianqian; Yan, Wei; Xing, Bo


    The effective and strong adherence of silver nanoparticles (AgNPs) to the substrate surface is pivotal to the practical application of those AgNPs-modified materials. In this work, AgNPs were synthesized through a green and facile hydrothermal method. Chitosan was introduced as the binding agent for the effective loading of AgNPs on activated carbon fibers (ACF) surface to fabricate the antibacterial material. Apart from conventional instrumental characterizations, i. e., scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), zeta potential and Brunauer-Emmett-Teller (BET) surface area measurement, molecular dynamics simulation method was also applied to explore the loading mechanism of AgNPs on the ACF surface. The AgNPs-loaded ACF material showed outstanding antibacterial activity for S. aureus and E. coli. The combination of experimental and theoretical calculation results proved chitosan to be a promising binding agent for the fabrication of AgNPs-loaded ACF material with excellent antibacterial activity.

  20. Reversible Operation of Solid Oxide Cells for Sustainable Fuel Production and Solar/Wind Load-Balancing

    DEFF Research Database (Denmark)

    Graves, Christopher R.; Villarreal, D.; Mýrdal, Jón Steinar Garðarsson


    electricity from fuels – either previously stored fuels or from anexternal supply e.g. natural gas or biogas. This reversibility combined with fuel-flexibility isunique among energy storage technologies like closed-system batteries and singledirectionelectrolyzers. However, few studies have been conducted......RSOC stack produces syngas via co-electrolysis of CO2 and H2O. Part of the syngas isconverted to methanol downstream in the system to meet the demand of transportationvehicles, and the rest is stored for electrical load balancing by conversion back toelectricity in fuel cell mode when electricity demand......The solid oxide electrochemical cell (SOC) is a promising candidate for large-scale energystorage. In electrolysis mode it stores renewable electricity as chemical energy in the formof fuels like hydrogen and hydrocarbons, and the same cell can be operated in the reversedirection to produce...

  1. Short-Term Multiple Forecasting of Electric Energy Loads for Sustainable Demand Planning in Smart Grids for Smart Homes

    Directory of Open Access Journals (Sweden)

    Adeshina Y. Alani


    Full Text Available Energy consumption in the form of fuel or electricity is ubiquitous globally. Among energy types, electricity is crucial to human life in terms of cooking, warming and cooling of shelters, powering of electronic devices as well as commercial and industrial operations. Users of electronic devices sometimes consume fluctuating amounts of electricity generated from smart-grid infrastructure owned by the government or private investors. However, frequent imbalance is noticed between the demand and supply of electricity, hence effective planning is required to facilitate its distribution among consumers. Such effective planning is stimulated by the need to predict future consumption within a short period. Although several interesting classical techniques have been used for such predictions, they still require improvement for the purpose of reducing significant predictive errors when used for short-term load forecasting. This research develops a near-zero cooperative probabilistic scenario analysis and decision tree (PSA-DT model to address the lacuna of enormous predictive error faced by the state-of-the-art models. The PSA-DT is based on a probabilistic technique in view of the uncertain nature of electricity consumption, complemented by a DT to reinforce the collaboration of the two techniques. Based on detailed experimental analytics on residential, commercial and industrial data loads, the PSA-DT model outperforms the state-of-the-art models in terms of accuracy to a near-zero error rate. This implies that its deployment for electricity demand planning will be of great benefit to various smart-grid operators and homes.

  2. Formulation development and evaluation of the anti-malaria properties of sustained release artesunate-loaded solid lipid microparticles based on phytolipids. (United States)

    Chinaeke, E E; Chime, S A; Onyishi, V I; Attama, A A; Okore, V C


    CONTEXTS: Artemisinins and its derivatives are considered the basis in the treatment of Plasmodium falciparum malaria due to their high potency and rapid action. However, they have short half life, low solubility, and poor oral bioavailability, hence the need to formulate sustained release lipid particulate dosage form of these drugs. To formulate and evaluate artesunate-loaded solid lipid microparticles (SLMs) based on structured lipid matrices consisting of soybean oil and dika wax. The lipid matrices were characterized by differential scanning calorimetry (DSC), small-angle X-ray diffraction (SAXD), and wide-angle X-ray diffraction (WAXD). The SLMs were prepared by hot melt-homogenization. Time-dependent particle size analysis, time-dependent pH stability studies, encapsulation efficiency (EE%), and in vitro drug release were carried out on the SLMs. In vivo anti-malarial studies were performed using a modified Peter's 4-day suppressive protocol using Plasmodium berghei infected mice. Thermograms of the lipid matrices showed modifications in the microstructure of dika wax as a result of inclusion of soybean oil. SAXD and WAXD diffractograms showed that the lipid matrices were found to be non-lamellar. Particle size of SLM increased with time, while the pH was almost constant. The SLMs had maximum EE% of 80.6% and sustained the release of artesunate more than the reference tablet. In vivo pharmacodynamic studies showed that the SLMs had significant (p daily in the treatment of malaria.

  3. Mechanical Behavior of Polyester and Fiber Glass as a Composite Material used in a Vehicle under Dynamic Loading

    Directory of Open Access Journals (Sweden)

    Ahmed Naif Al-Khazraji* Ali Yasser Hassa * Emad Abdul Hussein Abdul Sahib


    Full Text Available The automobile industry has shown increased interest in the replacement of steel spring with fiberglass composite leaf spring due to high strength compared to weight. The aim of this paper is to study two kinds of fiberglass, regular direction (0-90 and random direction immersed in polyester resin. They were tested under static load, as tensile test for their mechanical properties, and under dynamic load in fully reversible bending tests as fatigue test, to estimate S-N curves, and impact test for their mechanical properties. Results from the tensile tests showed that the tensile strength of the regular type is greater than random type. The fatigue test results showed that the number of cycles to failure in regular type of composite material is greater than that of the random type and the endurance limit is also greater than in random, the increase percentage in endurance limit is 7.5%. Results due to impact test showed that there were on increasing in fracture energy for the random type the increase ratio is 13.9%. The Important characteristics of composites that make them excellent for leaf spring instead of steel are higher strength-to-weight ratio, superior fatigue strength. Application of composite structures reduces the weight of leaf spring without any reduction on the load carrying capacity and stiffness in automobile suspension system.

  4. Mechanics of blast loading on the head models in the study of traumatic brain injury using experimental and computational approaches. (United States)

    Ganpule, S; Alai, A; Plougonven, E; Chandra, N


    Blast waves generated by improvised explosive devices can cause mild, moderate to severe traumatic brain injury in soldiers and civilians. To understand the interactions of blast waves on the head and brain and to identify the mechanisms of injury, compression-driven air shock tubes are extensively used in laboratory settings to simulate the field conditions. The overall goal of this effort is to understand the mechanics of blast wave-head interactions as the blast wave traverses the head/brain continuum. Toward this goal, surrogate head model is subjected to well-controlled blast wave profile in the shock tube environment, and the results are analyzed using combined experimental and numerical approaches. The validated numerical models are then used to investigate the spatiotemporal distribution of stresses and pressure in the human skull and brain. By detailing the results from a series of careful experiments and numerical simulations, this paper demonstrates that: (1) Geometry of the head governs the flow dynamics around the head which in turn determines the net mechanical load on the head. (2) Biomechanical loading of the brain is governed by direct wave transmission, structural deformations, and wave reflections from tissue-material interfaces. (3) Deformation and stress analysis of the skull and brain show that skull flexure and tissue cavitation are possible mechanisms of blast-induced traumatic brain injury.


    Directory of Open Access Journals (Sweden)

    Ali BAYRAM


    Full Text Available In this study, steel sheet materials were used in order to obtain dual-phase steel. Specimens for this purpose have been annealed in ferrite + astatine regions at the temperatures of 740, 760, 800 and 820 °C. The specimens were annealed at the different temperatures with corresponding times 20, 40 and 60 minutes and quenched into water. As a result of this dual-phase steels at different ferrite + martensite ratio were produced. Sheet specimens were tested at the range of loading rates of 10, 50 and 259 mm/min. Strength properties of dual-phase steels were investigated depending on annealing temperature, ratio of martensite and loading rate.

  6. Settlement mechanism of piled-raft foundation due to cyclic train loads and its countermeasure (United States)

    Gu, Linlin; Ye, Guanlin; Wang, Zhen; Ling, Xianzhang; Zhang, Feng


    In this paper, numerical simulation with soil-water coupling finite element-finite difference (FE-FD) analysis is conducted to investigate the settlement and the excess pore water pressure (EPWP) of a piled-raft foundation due to cyclic high-speed (speed: 300km/h) train loading. To demonstrate the performance of this numerical simulation, the settlement and EPWP in the ground under the train loading within one month was calculated and confirmed by monitoring data, which shows that the change of the settlement and EPWP can be simulated well on the whole. In order to ensure the safety of train operation, countermeasure by the fracturing grouting is proposed. Two cases are analyzed, namely, grouting in No-4 softest layer and No-9 pile bearing layer respectively. It is found that fracturing grouting in the pile bearing layer (No-9 layer) has better effect on reducing the settlement.

  7. Fracture Mechanics Analysis of Reinforced DCB Sandwich Debond Specimen Loaded by Moments

    DEFF Research Database (Denmark)

    Saseendran, Vishnu; Berggreen, Christian; Carlsson, Leif A.


    Analytical expressions for the energy release rate and mode-mixity phase angle are derived for a sandwich composite double-cantilever beam fracture specimen with the face sheets reinforced by stiff plates. The sandwich beam is considered symmetric, with identical top and bottom facesheets. Only...... a pure moment loading is considered. The J-integral coupled with laminate beam theory is employed to derive closed-form expression for the energy releaserate in terms of the applied moments, geometry, and material properties .A scalar quantityωis obtained to express the mode-mixity phase angle....... It is shown that ω is independent of the applied loading conditions. The value of ω is found to be moderately influenced by reinforcement thicknesses....

  8. Identification of genes regulated during mechanical load-induced cardiac hypertrophy (United States)

    Johnatty, S. E.; Dyck, J. R.; Michael, L. H.; Olson, E. N.; Abdellatif, M.; Schneider, M. (Principal Investigator)


    Cardiac hypertrophy is associated with both adaptive and adverse changes in gene expression. To identify genes regulated by pressure overload, we performed suppressive subtractive hybridization between cDNA from the hearts of aortic-banded (7-day) and sham-operated mice. In parallel, we performed a subtraction between an adult and a neonatal heart, for the purpose of comparing different forms of cardiac hypertrophy. Sequencing more than 100 clones led to the identification of an array of functionally known (70%) and unknown genes (30%) that are upregulated during cardiac growth. At least nine of those genes were preferentially expressed in both the neonatal and pressure over-load hearts alike. Using Northern blot analysis to investigate whether some of the identified genes were upregulated in the load-independent calcineurin-induced cardiac hypertrophy mouse model, revealed its incomplete similarity with the former models of cardiac growth. Copyright 2000 Academic Press.

  9. Structural Mechanisms of Hexameric Helicase Loading, Assembly, and Unwinding [version 1; referees: 3 approved

    Directory of Open Access Journals (Sweden)

    Michael A. Trakselis


    Full Text Available Hexameric helicases control both the initiation and the elongation phase of DNA replication. The toroidal structure of these enzymes provides an inherent challenge in the opening and loading onto DNA at origins, as well as the conformational changes required to exclude one strand from the central channel and activate DNA unwinding. Recently, high-resolution structures have not only revealed the architecture of various hexameric helicases but also detailed the interactions of DNA within the central channel, as well as conformational changes that occur during loading. This structural information coupled with advanced biochemical reconstitutions and biophysical methods have transformed our understanding of the dynamics of both the helicase structure and the DNA interactions required for efficient unwinding at the replisome.

  10. Diagnostic indicators for shipboard mechanical systems using non-intrusive load monitoring


    McKay, Thomas Duncan


    CIVINS (Civilian Institutions) Thesis document Approved for public release, distribution unlimited This thesis examines the use of Non-intrusive Load Monitoring (NILM) in auxiliary shipboard systems, such as a low pressure air system, to determine the state of equipment in larger connected systems, such as the main propulsion engines. Using data collected on previously installed NILM's at the Naval Surface Warfare Center, Philadelphia DDG-51 Land Based Engineering Site (LBES), major eve...

  11. Simulation of Structures Exhibiting Instability Under Thermal-Mechanical Transient Loading (United States)


    arches represented in the space of ),( lmiduD : (a) No imperfection, (b) 001.0and,005.0,03.0 642 === eee . BY14-020SP: Simulation of Structures...sine arches represented in the space of ),( lp : (a) No imperfection, (b) 001.0and,005.0,03.0 642 === eee . Critical Loads In this part, the

  12. Effect of Protective Devices on Brain Trauma Mechanics Under Idealized Shock Wave Loading (United States)


    outside may be due to the jet wind effect. As the RED head is loaded due to the traversing shockwave, it springs back due to the energy stored in the...05001-001 Submitted to: Dr. Larry Russell, Ph.D. Army Research Office Marina Carboni/Michael Maffeo NATICK ARO/NATICK Final Report on... energy in the anterior of the head. Gathering the peak minimum and maximum values from the first 5ms, the shock tube data better approximates the free

  13. Excess nitrate loads to coastal waters reduces nitrate removal efficiency: mechanism and implications for coastal eutrophication. (United States)

    Lunau, Mirko; Voss, Maren; Erickson, Matthew; Dziallas, Claudia; Casciotti, Karen; Ducklow, Hugh


    Terrestrial ecosystems are becoming increasingly nitrogen-saturated due to anthropogenic activities, such as agricultural loading with artificial fertilizer. Thus, more and more reactive nitrogen is entering streams and rivers, primarily as nitrate, where it is eventually transported towards the coastal zone. The assimilation of nitrate by coastal phytoplankton and its conversion into organic matter is an important feature of the aquatic nitrogen cycle. Dissolved reactive nitrogen is converted into a particulate form, which eventually undergoes nitrogen removal via microbial denitrification. High and unbalanced nitrate loads to the coastal zone may alter planktonic nitrate assimilation efficiency, due to the narrow stochiometric requirements for nutrients typically shown by these organisms. This implies a cascade of changes for the cycling of other elements, such as carbon, with unknown consequences at the ecosystem level. Here, we report that the nitrate removal efficiency (NRE) of a natural phytoplankton community decreased under high, unbalanced nitrate loads, due to the enhanced recycling of organic nitrogen and subsequent production and microbial transformation of excess ammonium. NRE was inversely correlated with the amount of nitrate present, and mechanistically controlled by dissolved organic nitrogen (DON), and organic carbon (Corg) availability. These findings have important implications for the management of nutrient runoff to coastal zones. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  14. The Best of Two Worlds. Article 6 mechanisms shall contribute to Sustainable Development Goals (SDGs)

    DEFF Research Database (Denmark)

    Olsen, Karen Holm; Soezer, Alexandra


    The Paris Agreement and the UN Sustainable Development Goals (SDGs) were two milestone achievements in 2015. The Intended Nationally Determined Contributions (INDCs) put forward by Parties before the Climate Conference in Paris will have to be fully embedded in the 2030 agenda to achieve truly...

  15. Evaluation of the physical work load and biomechanical of workers at manual and semi-mechanized mowing

    Directory of Open Access Journals (Sweden)

    Felipe Martins de Oliveir


    Full Text Available The objective of this research was to evaluate of the physical work load and biomechanical of workers at manual and semi-mechanized mowing activities for the planting the forests. The physical work load was evaluated in a survery of the workers cardiac frequency in different stages of the work using a Polar Oy monitor. To the biomechanic evaluation the workers were filmed in the execution of the work, defined the typical postures adopted and the date analyzed in program 3DSSPP (3D Static Strength Prediction Program developed for University of Michigan, USA. The results showed that the activity of manual mowing required greater physical effort, with cardiac frequency above the maximum limit recommended of 40% and the activity was classified as heavy. In this method of working the various joints of the workers showed injurie risks. The hip joint articulation was the most affected, with capable percentage varying between 88 and 92%.

  16. [Preparation and characterization of irinotecan hydrochloride loaded PEO-PPO-PEO micelles and its mechanism of decreasing drug intestinal toxicity]. (United States)

    Zhang, Xin-Xin; Guo, Shi-Yan; Li, Fei-Fei; Gan, Yong


    In this work, we developed PEO-PPO-PEO micelles loaded with irinotecan hydrochloride (CPT-11) using breast cancer resistance protein (BCRP) inhibitory material PEO20-PPO70-PEO20, and studied its mechanism of decreasing CPT-11 induced delayed diarrhea and intestinal toxicity. BCRP-overexpressing MDCKII (MDCKII/BCRP) cells were used to evaluate the effect of PEO20-PPO70-PEO20 and PEO-PPO-PEO micelles on transmembrane transport of CPT-11 in vitro. The biliary excretion, delayed diarrhea and intestinal damage of CPT-11 loaded PEO-PPO-PEO micelles of rats were investigated. The results showed that the obtained micelles could decrease the biliary excretion of CPT-11, ameliorate delayed diarrhea and intestinal toxicity of rats through inhibiting BCRP-mediated CPT-11 efflux. PEO-PPO-PEO micelles were promising carriers to reduce intestinal toxicity of CPTs.

  17. Economic perspective of hybrid wind-diesel technology for commercial loads of Dhahran Saudi Arabia: A step towards sustainable future

    Directory of Open Access Journals (Sweden)

    Shaahid S.M.


    Full Text Available The governments world-wide are deliberating to promote renewable energy sources such as wind to mitigate increasing demand of energy and to overcome effects of pollution due to to use of fossil fuels. Integration of wind turbine generators (WTG with the diesel plants is pursued widely to reduce dependence on fossil-fuels and to reduce carbon emissions. Literature indicates that commercial/residential buildings in the Kingdom of Saudi Arabia (K.S.A consume an estimated 10 - 40% of the total electric energy generated. The aim of this study is to analyze wind-speed data of Dhahran (East-Coast, K.S.A. to assess the economic feasibility of utilizing hybrid wind-diesel power systems to meet the load requirements of a typical commercial building (with annual electrical energy demand of 620,000 kWh. The monthly average wind speeds range from 3.3 to 5.6 m/s. The hybrid systems simulated consist of different combinations of 100 kW commercial WTG supplemented with diesel generators. NREL’s (HOMER Energy’s HOMER software has been employed to perform the techno-economic analysis. The simulation results indicate that for a hybrid system comprising of 100 kW wind capacity together with 175 kW diesel system, the wind penetration (at 37 m hub-height, with 0% annual capacity shortage is 25%. The cost of generating energy (COE, $/kWh from this hybrid wind-diesel system has been found to be 0.121 $/kWh (assuming diesel fuel price of 0.1$/liter. The study exhibits that for a given hybrid configuration, the number of operational hours of diesel gensets decreases with increase in wind farm capacity. Emphasis has also been placed on wind penetration, un-met load, energy production and COE, excess electricity generation, percentage fuel savings and reduction in carbon emissions (relative to diesel-only situation of different hybrid systems, cost break-down of wind-diesel systems, COE of different hybrid systems, etc.

  18. Recombinant sclerostin antagonises effects of ex vivo mechanical loading in trabecular bone and increases osteocyte lacunar size. (United States)

    Kogawa, Masakazu; Khalid, Kamarul A; Wijenayaka, Asiri R; Ormsby, Renee T; Evdokiou, Andreas; Anderson, Paul H; Findlay, David M; Atkins, Gerald J


    Sclerostin (SCL) has emerged as an important regulator of bone mass. We have shown that SCL can act by targeting late osteoblasts/osteocytes to inhibit bone mineralisation and to upregulate osteocyte expression of catabolic factors, resulting in osteocytic osteolysis. Here we sought to examine the effect of exogenous sclerostin on osteocytes in trabecular bone mechanically loaded ex vivo. Bovine trabecular bone cores, with bone marrow removed, were inserted into individual chambers and subjected to daily episodes of dynamic loading. Cores were perfused with either osteogenic media alone or media containing human recombinant sclerostin (rhSCL) (50 ng/ml). Loaded control bone increased in apparent stiffness over time compared to unloaded bone, and this was abrogated in the presence of rhSCL. Loaded bone showed an increase in calcein uptake as a surrogate of mineral accretion, compared to unloaded bone, in which this was substantially inhibited by rhSCL treatment. Sclerostin treatment induced a significant increase in the ionised calcium concentration in the perfusate and the release of β-CTX at several time points, an increased mean osteocyte lacunar size, indicative of osteocytic osteolysis and the expression of catabolism-related genes. Human primary osteocyte-like cultures treated with rhSCL also released β-CTX from their matrix. These results suggest that osteocytes contribute directly to bone mineral accretion, and to the mechanical properties of bone. Moreover, it appears that sclerostin, acting on osteocytes, can negate this effect by modulating the dimensions of the lacunocanalicular porosity and the composition of the peri-osteocyte matrix. Copyright © 2017, American Journal of Physiology-Cell Physiology.

  19. Gallium-Loaded Dissolvable Microfilm Constructs that Provide Sustained Release of Ga(3+) for Management of Biofilms. (United States)

    Herron, Maggie; Schurr, Michael J; Murphy, Christopher J; McAnulty, Jonathan F; Czuprynski, Charles J; Abbott, Nicholas L


    The persistence of bacterial biofilms in chronic wounds delays wound healing. Although Ga(3+) can inhibit or kill biofilms, precipitation as Ga(OH)3 has prevented its use as a topical wound treatment. The design of a microfilm construct comprising a polyelectrolyte film that releases noncytotoxic concentrations of Ga(3+) over 20 d and a dissolvable micrometer-thick film of polyvinylalcohol that enables facile transfer onto biomedically important surfaces is reported. By using infrared spectroscopy, it is shown that the density of free carboxylate/carboxylic acid and amine groups within the polyelectrolyte film regulates the capacity of the construct to be loaded with Ga(3+) and that the density of covalent cross-links introduced into the polyelectrolyte film (amide-bonds) controls the release rate of Ga(3+) . Following transfer onto the wound-contact surface of a biologic wound dressing, an optimized construct is demonstrated to release ≈0.7 μg cm(-2) d(-1) of Ga(3+) over 3 weeks, thus continuously replacing Ga(3+) lost to precipitation. The optimized construct inhibits formation of P. aeruginosa (two strains; ATCC 27853 and PA01) biofilms for up to 4 d and causes pre-existing biofilms to disperse. Overall, this study provides designs of polymeric constructs that permit facile modification of the wound-contacting surfaces of dressings and biomaterials to manage biofilms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel (United States)

    Leuning, N.; Steentjes, S.; Schulte, M.; Bleck, W.; Hameyer, K.


    The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment.

  1. CDM (Clean development mechanism) like instrument for sustainable development?; MDL (mecanismo de desenvolvimento limpo) como instrumento para o desenvolvimento sustentavel?

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Kamyla Borges da; Walter, Arnaldo Cesar Silva; Varella, Fabiana Karla de Oliveira; Streb, Cleci Schalemberger [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Fac. de Engenharia Mecanica. Curso de Pos-Graduaco em Planejamento de Sistemas Energeticos], e-mail:


    The intensification of the greenhouse effect, caused mainly by the anthropogenic activities, such as the intensive use of fossil fuels, reveals itself as a challenge to governments and international organizations. The institution of an international legal framework, resulted from the implementation of the United Nations Framework Convention on Climate Change and the Kyoto Protocol, is allowing the development of some mitigation instruments, such as the clean development mechanism (CDM). The article's purpose is to assess the social and economic aspects that are leading to the climate change process and to analyze the instruments foreseen in the international legal system to face this global concern, in special, the CDM as a tool to achieve sustainable development practices. In this way, the authors aims to demonstrate the connection and interdependence between those instruments and the sustainable development. (author)

  2. Thermal-vacuum facility with in-situ mechanical loading. [for testing space construction materials (United States)

    Tennyson, R. C.; Hansen, J. S.; Holzer, R. P.; Uffen, B.; Mabson, G.


    The paper describes a thermal-vacuum space simulator used to assess property changes of fiber-reinforced polymer composite systems. The facility can achieve a vacuum of approximately .0000001 torr with temperatures ranging from -200 to +300 F. Some preliminary experimental results are presented for materials subjected to thermal loading up to 200 F. The tests conducted include the evaluation of matrix modulus and strength, coefficients of thermal expansion, and fracture toughness. Though the experimental program is at an early stage, the data appear to indicate that these parameters are influenced by hard vacuum.

  3. Sustained anxiety increases amygdala–dorsomedial prefrontal coupling: a mechanism for maintaining an anxious state in healthy adults (United States)

    Vytal, Katherine E.; Overstreet, Cassie; Charney, Danielle R.; Robinson, Oliver J.; Grillon, Christian


    Background Neuroimaging research has traditionally explored fear and anxiety in response to discrete threat cues (e.g., during fear conditioning). However, anxiety is a sustained aversive state that can persist in the absence of discrete threats. Little is known about mechanisms that maintain anxiety states over a prolonged period. Here, we used a robust translational paradigm (threat of shock) to induce sustained anxiety. Recent translational work has implicated an amygdala–prefrontal cortex (PFC) circuit in the maintenance of anxiety in rodents. To explore the functional homologues of this circuitry in humans, we used a novel paradigm to examine the impact of sustained anticipatory anxiety on amygdala–PFC intrinsic connectivity. Methods Task-independent fMRI data were collected in healthy participants during long-duration periods of shock anticipation and safety. We examined intrinsic functional connectivity. Results Our study involved 20 healthy participants. During sustained anxiety, amygdala activity was positively coupled with dorsomedial PFC (DMPFC) activity. High trait anxiety was associated with increased amygdala–DMPFC coupling. In addition, induced anxiety was associated with positive coupling between regions involved in defensive responding, and decreased coupling between regions involved in emotional control and the default mode network. Limitations Inferences regarding anxious pathology should be made with caution because this study was conducted in healthy participants. Conclusion Findings suggest that anticipatory anxiety increases intrinsic amygdala–DMPFC coupling and that the DMPFC may serve as a functional homologue for the rodent prefrontal regions by sustaining anxiety. Future research may use this defensive neural context to identify bio-markers of risk for anxious pathology and target these circuits for therapeutic intervention. PMID:24886788

  4. Evaluating chemical-, mechanical-, and bio-pulping processes and their sustainability characterization using life cycle assessment (United States)

    Tapas K. Das; Carl Houtman


    Pulp and paper manufacturing constitutes one of the largest industry segments in the United States in term of water and energy usage and total discharges to the environment. More than many other industries, however, this industry plays an important role in sustainable development because its chief raw material— wood fiber—is renewable. This industry provides an example...

  5. Electricity Pricing Mechanism in a Sustainable Environment: A Review and a System Dynamics Modeling Approach


    Tziogas, C; Georgiadis, P; Tsolakis, N; Yakinthos, C


    Electricity is an undisputed factor supporting human development, while further supporting social wellbeing and fostering economic growth of modern societies. Therefore, the electricity market provides a vivid policy-making arena for the EU regulators, where on-going structural reforms are promoted with the aim to encapsulate and accommodate sustainability aspects. Notably, the EU Member States have adopted the strategic roadmap “Europe 2020” toward reducing greenhouse gas emissions and energ...

  6. In vitro validation of a novel mechanical model for testing the anchorage capacity of pedicle screws using physiological load application. (United States)

    Liebsch, Christian; Zimmermann, Julia; Graf, Nicolas; Schilling, Christoph; Wilke, Hans-Joachim; Kienle, Annette


    Biomechanical in vitro tests analysing screw loosening often include high standard deviations caused by high variabilities in bone mineral density and pedicle geometry, whereas standardized mechanical models made of PU foam often do not integrate anatomical or physiological boundary conditions. The purpose of this study was to develop a most realistic mechanical model for the standardized and reproducible testing of pedicle screws regarding the resistance against screw loosening and the holding force as well as to validate this model by in vitro experiments. The novel mechanical testing model represents all anatomical structures of a human vertebra and is consisting of PU foam to simulate cancellous bone, as well as a novel pedicle model made of short carbon fibre filled epoxy. Six monoaxial cannulated pedicle screws (Ø6.5 × 45mm) were tested using the mechanical testing model as well as human vertebra specimens by applying complex physiological cyclic loading (shear, tension, and bending; 5Hz testing frequency; sinusoidal pulsating forces) in a dynamic materials testing machine with stepwise increasing load after each 50.000 cycles (100.0N shear force + 20.0N per step, 51.0N tension force + 10.2N per step, 4.2Nm bending moment + 0.8Nm per step) until screw loosening was detected. The pedicle screw head was fixed on a firmly clamped rod while the load was applied in the vertebral body. For the in vitro experiments, six human lumbar vertebrae (L1-3, BMD 75.4 ± 4.0mg/cc HA, pedicle width 9.8 ± 0.6mm) were tested after implanting pedicle screws under X-ray control. Relative motions of pedicle screw, specimen fixture, and rod fixture were detected using an optical motion tracking system. Translational motions of the mechanical testing model experiments in the point of load introduction (0.9-2.2mm at 240N shear force) were reproducible within the variation range of the in vitro experiments (0.6-3.5mm at 240N shear force). Screw loosening occurred continuously in

  7. Kinetic model for mechanical twinning and its application for intensive loading of metals

    Directory of Open Access Journals (Sweden)

    Mayer Alexander


    Full Text Available In this report, we present our twinning model intended for simulation of the dynamic deformation of metals with low values of the stacking fault energy, as well as the results of application of the model to numerical simulation of intensive loading of metals. Generation of a twin is described as an appearance of a stacking fault with size more than some critical value, while growth of a twin is considered as a cooperative movement of partial dislocation along the stacking fault. The twin nucleation rate is expressed through the energy released due to annihilation of dislocations. Movement of partial dislocations in the course of twin growth passes under the action of elastic stress field and phonon drag. The surface energy of the growing twin continuously increases which leads to the appearance of an additional force. Application of this model allows us to investigate plastic response of metals at various dynamic loading conditions and initial defect structures. Influence of twinning at Taylor rod compaction experiments is analyzed including formation of the shape of the lateral surface.

  8. Validation of two accelerometers to determine mechanical loading of physical activities in children. (United States)

    Meyer, Ursina; Ernst, Dominique; Schott, Silvia; Riera, Claudia; Hattendorf, Jan; Romkes, Jacqueline; Granacher, Urs; Göpfert, Beat; Kriemler, Susi


    The purpose of this study was to assess the validity of accelerometers using force plates (i.e., ground reaction force (GRF)) during the performance of different tasks of daily physical activity in children. Thirteen children (10.1 (range 5.4-15.7) years, 3 girls) wore two accelerometers (ActiGraph GT3X+ (ACT), GENEA (GEN)) at the hip that provide raw acceleration signals at 100 Hz. Participants completed different tasks (walking, jogging, running, landings from boxes of different height, rope skipping, dancing) on a force plate. GRF was collected for one step per trial (10 trials) for ambulatory movements and for all landings (10 trials), rope skips and dance procedures. Accelerometer outputs as peak loading (g) per activity were averaged. ANOVA, correlation analyses and Bland-Altman plots were computed to determine validity of accelerometers using GRF. There was a main effect of task with increasing acceleration values in tasks with increasing locomotion speed and landing height (P impact loading of bone in children, although they systematically overestimate GRF.

  9. Mechanical Differences between Barbell and Body Optimum Power Loads in the Jump Squat Exercise. (United States)

    Loturco, Irineu; Pereira, Lucas A; Zanetti, Vinicius; Kitamura, Katia; Abad, César C Cal; Kobal, Ronaldo; Nakamura, Fabio Y


    This study compared the values of bar-peak force (PF Bar ) and power (PP Bar ), body-peak force (PF Body ) and power (PPBody) and bar-mean propulsive power (MPP Bar ) in different jump-squat (JS) conditions: unloaded condition (UC); bar-loaded condition (BLC) and optimum bar-MPP condition (OBC). Twenty-five soccer players performed the JS using a bar with negligible mass (UC), using the Smith-machine bar (BLC) and using the load capable of maximizing the bar-MPP (OBC). The PF Body was significantly higher in the UC (2847.9 ± 489.1 N) than in the OBC (2655.4 ± 444.3 N). The UC presented greater PPBody (3775.9 ± 631.5 W) than the BLC (3359.7 ± 664.3 W) and OBC (3357.8 ± 625.3 W). The OBC presented higher values of PF Bar , PP Bar and MPP Bar (676.2 ± 109.4 W) than the BLC (MPP Bar = 425.8 ± 53.7 W) (all p intensity at which both components of the power equation (force and velocity) are optimized. This has important implications for sports training.

  10. A general mixed mode fracture mechanics test specimen: The DCB-specimen loaded with uneven bending moments

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Jørgensen, K.; Jacobsen, T.K.


    glass-fibre laminates was studied. The mixed mode fracture resistance increased with increasing crack length due to fibre bridging, eventually reaching asteady-state level (R-curve behaviour). The steady-state fracture toughness level increased with increasing tangential crack opening displacement.......A mixed mode specimen is proposed for fracture mechanics characterisation of adhesive joints, laminates and multilayers. The specimen is a double cantilever beam specimen loaded with uneven bending moments at the two free beams. By varying the ratiobetween the two applied moments, the full mode...

  11. Maintenance of working capacity of movement mechanism of load trolley with linear traction electric drive of bridge type crane. (United States)

    Goncharov, K. A.; Denisov, I. A.


    The article considers the influence of the air gap size between the linear motor elements on the stability of the traction drive of the movement mechanism of the trolley of the bridge type crane. The main factors affecting the air gap size and the causes of their occurrence are described. The technique of calculating the magnitude of air gap variation is described in relation to the general deformation of the crane metal structure. Recommendations on the need for installation of additional equipment for load trolleys of various designs are given. The optimal values of the length of the trolley base are proposed. Observance of these values ensures normal operation of the traction drive.

  12. Controllable synthesis and characterisation of palladium (II) anticancer complex-loaded colloidal gelatin nanoparticles as a novel sustained-release delivery system in cancer therapy. (United States)

    Alasvand, Neda; Saeidifar, Maryam; Saboury, Ali Akbar; Mozafari, Masoud


    Over the past few years, there have been several attempts to deliver anticancer drugs into the body. It has been shown that compared to other available carriers, colloidal gelatin nanoparticles (CGNPs) have distinct properties due to their exceptional physico-chemical and biological characteristics. In this study, a novel water-soluble palladium (II) anticancer complex was first synthesised, and then loaded into CGNPs. The CGNPs were synthesised through a two-step desolvation method with an average particle size of 378 nm. After confirming the stability of the drug in the nanoparticles, the drug-loaded CGNPs were tested for in vitro cytotoxicity against human breast cancer cells. The results showed that the average drug encapsulating efficiency and drug loading of CGNPs were 64 and 10 ± 2.1% (w/w), respectively. There was a slight shift to higher values of cumulative release, when the samples were tested in lower pH values. In addition, the in vitro cytotoxicity test indicated that the number of growing cells significantly decreased after 48 h in the presence of different concentrations of drug. The results also demonstrated that the released drug could bind to DNA by a static mechanism at low concentrations (0.57 µM) on the basis of hydrophobic and hydrogen binding interactions.

  13. Increased expression of matrix extracellular phosphoglycoprotein (MEPE in cortical bone of the rat tibia after mechanical loading: identification by oligonucleotide microarray.

    Directory of Open Access Journals (Sweden)

    Christianne M A Reijnders

    Full Text Available Skeletal integrity in humans and animals is maintained by daily mechanical loading. It has been widely accepted that osteocytes function as mechanosensors. Many biochemical signaling molecules are involved in the response of osteocytes to mechanical stimulation. The aim of this study was to identify genes involved in the translation of mechanical stimuli into bone formation. The four-point bending model was used to induce a single period of mechanical loading on the right tibia, while the contra lateral left tibia served as control. Six hours after loading, the effects of mechanical loading on gene-expression were determined with microarray analysis. Protein expression of differentially regulated genes was evaluated with immunohistochemistry. Nine genes were found to exhibit a significant differential gene expression in LOAD compared to control. MEPE, Garnl1, V2R2B, and QFG-TN1 olfactory receptor were up-regulated, and creatine kinase (muscle form, fibrinogen-B beta-polypeptide, monoamine oxidase A, troponin-C and kinesin light chain-C were down-regulated. Validation with real-time RT-PCR analysis confirmed the up-regulation of MEPE and the down-regulation of creatine kinase (muscle form and troponin-C in the loaded tibia. Immunohistochemistry showed that the increase of MEPE protein expression was already detectable six hours after mechanical loading. In conclusion, these genes probably play a role during translation of mechanical stimuli six hours after mechanical loading. The modulation of MEPE expression may indicate a connection between bone mineralization and bone formation after mechanical stimulation.

  14. Assembly and Mechanical Properties of the Cargo-Free and Cargo-Loaded Bacterial Nanocompartment Encapsulin

    NARCIS (Netherlands)

    Snijder, Joost|info:eu-repo/dai/nl/338018328; Kononova, Olga; Barbu, Ioana M|info:eu-repo/dai/nl/313937532; Uetrecht, Charlotte|info:eu-repo/dai/nl/304824623; Rurup, W Frederik; Koay, Melissa S T; Burnley, Rebecca J; Cornelissen, Jeroen J L M; Roos, Wouter H; Barsegov, Valeri; Wuite, Gijs J L; Heck, Albert J R|info:eu-repo/dai/nl/105189332


    Prokaryotes mostly lack membranous compartments that are typical of eukaryotic cells, but instead, they have various protein-based organelles. These include bacterial microcompartments like the carboxysome and the virus-like nanocompartment encapsulin. Encapsulins have an adaptable mechanism for

  15. Assembly and Mechanical Properties of the Cargo-Free and Cargo Loaded Bacterial Nanocompartment Encapsulin

    NARCIS (Netherlands)

    Snijder, J.; Kononova, O.; Barbu, I.M.; Uetrecht, C.; Rurup, W.F.; Koay, M.S.T.; Cornelissen, J.J.L.M.; Roos, W.H.; Barsegov, V.; Wuite, G.J.L.; Heck, A.J.R.


    Prokaryotes mostly lack membranous compartments that are typical of eukaryotic cells, but instead, they have various protein-based organelles. These include bacterial microcompartments like the carboxysome and the virus-like nanocompartment encapsulin. Encapsulins have an adaptable mechanism for

  16. Assembly and mechanical properties of the cargo-free and cargo-loaded bacterial nanocompartment encapsulin

    NARCIS (Netherlands)

    Snijder, Joost; Kononova, Olga; Barbu, Ioana M; Uetrecht, Charlotte; Rurup, W Frederik; Burnley, Rebecca J; Koay, Melissa S T; Cornelissen, Jeroen J L M; Roos, Wouter H; Barsegov, Valeri; Wuite, Gijs J L; Heck, Albert J R


    Prokaryotes mostly lack membranous compartments that are typical of eukaryotic cells, but instead they have various protein-based organelles. These include bacterial microcompartments like the carboxysome and the virus-like nanocompartment encapsulin. Encapsulins have an adaptable mechanism for

  17. Complete mechanical behavior analysis of FG Nano Beam under non-uniform loading using non-local theory (United States)

    Ghaffari, I.; Parhizkar Yaghoobi, M.; Ghannad, M.


    The purpose of this study is to offer a complete solution to analyze the mechanical behavior (bending, buckling and vibration) of Nano-beam under non-uniform loading. Furthermore, the effects of size (nonlocal parameters), non-homogeneity constants, and different boundary conditions are investigated by using this method. The exact solution presented here reduces costs incurred by experiments. In this research, the displacement field obeys the kinematics of the Euler–Bernoulli beam theory and non-local elasticity theory has been used. The governing equations and general boundary conditions are derived for a beam by using energy method. The presented solution enables us to analyze any kind of loading profile and boundary conditions with no limitations. Furthermore, this solution, unlike previous studies, is not a series-solution; hence, there is no limitation prior to existing with the series-solution, nor does it need to check convergence. Based on the developed analytical solution, the influence of size, non-homogeneity and non-uniform loads on bending, buckling and vibration behaviors is discussed. Also, the obtained result is highly accurate and in good agreement with previous research. In theoretical method, the allowable range for non-local parameters can be determined so as to make a major contribution to the reduction of the cost of experiments determining the value of non-local parameters.

  18. Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Leuning, N., E-mail: [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Steentjes, S. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Schulte, M.; Bleck, W. [Steel Institute, RWTH Aachen University, D-52072 Aachen (Germany); Hameyer, K. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany)


    The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment. - Highlights: • A detailed look at magnetic anisotropy of FeSi NGO electrical steel. • Study of magnetic behavior under elastic as well as plastic tensile stresses. • Correlation of magnetic behavior with microscopic deformation mechanisms. • Discussion of detrimental and beneficial effects of external stresses. • Loss separation at different polarizations and frequencies under increasing stress.

  19. Trunk and hip biomechanics influence anterior cruciate loading mechanisms in physically active participants. (United States)

    Frank, Barnett; Bell, David R; Norcross, Marc F; Blackburn, J Troy; Goerger, Benjamin M; Padua, Darin A


    Excessive trunk motion and deficits in neuromuscular control (NMC) of the lumbopelvic hip complex are risk factors for anterior cruciate ligament (ACL) injury. However, the relationship between trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads during a sidestep cutting task has not been examined. To determine if there is an association between multiplanar trunk motion, NMC of the lumbopelvic hip complex, and triplanar knee loads with ACL injury during a sidestep cutting task. Descriptive laboratory study. The hip and knee biomechanics and trunk motion of 30 participants (15 male, 15 female) were analyzed during a sidestep cutting task using an optoelectric camera system interfaced to a force plate. Trunk and lower extremity biomechanics were calculated from the kinematic and ground-reaction force data during the first 50% of the stance time during the cutting task. Pearson product moment correlation coefficients were calculated between trunk and lower extremity biomechanics. Multiple linear regression analyses were carried out to determine the amount of variance in triplanar knee loading explained by trunk motion and hip moments. A greater internal knee varus moment (mean, 0.11 ± 0.12 N·m/kg*m) was associated with less transverse-plane trunk rotation away from the stance limb (mean, 20.25° ± 4.42°; r = -0.46, P = .011) and a greater internal hip adduction moment (mean, 0.33 ± 0.25 N·m/kg*m; r = 0.83, P < .05). A greater internal knee external rotation moment (mean, 0.11 ± 0.08 N·m/kg*m) was associated with a greater forward trunk flexion (mean, 7.62° ± 5.28°; r = 0.42, P = .020) and a greater hip internal rotation moment (mean, 0.15 ± 0.16 N·m/kg*m; r = 0.59, P = .001). Trunk rotation and hip adduction moment explained 81% (P < .05) of the variance in knee varus moment. Trunk flexion and hip internal rotation moment explained 48% (P < .05) of the variance in knee external rotation moment. Limited trunk rotation displacement

  20. Mechanics of the knee. A study of joint and muscle load with clinical applications. (United States)

    Nisell, R


    The load moment of force about the knee joint during machine milking and when lifting a 12.8 kg box was quantified using a computerized static sagittal plane body model. Surface electromyography of quadriceps and hamstrings muscles was normalized and expressed as a percentage of an isometric maximum voluntary test contraction. Working with straight knees and the trunk flexed forwards induced extending knee load moments of maximum 55 Nm. Lifting the box with flexed knees gave flexing moments of 50 Nm at the beginning of the lift, irrespective of whether the burden was between or in front of the feet. During machine milking, a level difference between operator and cow of 0.70 m - 1.0 m significantly lowered the knee extending moments. To quantify the force magnitudes acting in the tibio-femoral and patello-femoral joints, a local biomechanical model of the knee was developed using a combination of cadaver knee dissections and lateral knee radiographs of healthy subjects. The moment arm of the knee extensor was significantly shorter for women than for men, which resulted in higher knee joint forces in women if the same moment was produced. A diagram for quantifying patellar forces was worked out. The force magnitudes given by the knee joint biomechanical model correlated well with experimentally forces measured by others. During the parallel squat in powerlifting, the maximum flexing knee load moment was estimated to 335-550 Nm when carrying a 382.5 kg burden and the in vivo force of a complete quadriceps tendon-muscle rupture to between 10,900 and 18,300 N. During isokinetic knee extension, the tibio-femoral compressive force reached peak magnitudes of 9 times body weight and the anteroposterior shear force was close to 1 body weight at knee angles straighter than 60 degrees, indicating that high forces stress the anterior cruciate ligament. A proximal resistance pad position decreased the shear force considerably, and this position is recommended in early

  1. Comparing maximum rate and sustainability of pacing by mechanical vs. electrical stimulation in the Langendorff-perfused rabbit heart. (United States)

    Quinn, T Alexander; Kohl, Peter


    Mechanical stimulation (MS) represents a readily available, non-invasive means of pacing the asystolic or bradycardic heart in patients, but benefits of MS at higher heart rates are unclear. Our aim was to assess the maximum rate and sustainability of excitation by MS vs. electrical stimulation (ES) in the isolated heart under normal physiological conditions. Trains of local MS or ES at rates exceeding intrinsic sinus rhythm (overdrive pacing; lowest pacing rates 2.5±0.5 Hz) were applied to the same mid-left ventricular free-wall site on the epicardium of Langendorff-perfused rabbit hearts. Stimulation rates were progressively increased, with a recovery period of normal sinus rhythm between each stimulation period. Trains of MS caused repeated focal ventricular excitation from the site of stimulation. The maximum rate at which MS achieved 1:1 capture was lower than during ES (4.2±0.2 vs. 5.9±0.2 Hz, respectively). At all overdrive pacing rates for which repetitive MS was possible, 1:1 capture was reversibly lost after a finite number of cycles, even though same-site capture by ES remained possible. The number of MS cycles until loss of capture decreased with rising stimulation rate. If interspersed with ES, the number of MS to failure of capture was lower than for MS only. In this study, we demonstrate that the maximum pacing rate at which MS can be sustained is lower than that for same-site ES in isolated heart, and that, in contrast to ES, the sustainability of successful 1:1 capture by MS is limited. The mechanism(s) of differences in MS vs. ES pacing ability, potentially important for emergency heart rhythm management, are currently unknown, thus warranting further investigation. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

  2. Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury. (United States)

    Cinelli, I; Destrade, M; Duffy, M; McHugh, P


    Axonal damage is one of the most common pathological features of traumatic brain injury, leading to abnormalities in signal propagation for nervous systems. We present a 3D fully coupled electro-mechanical model of a nerve bundle, made with the finite element software Abaqus 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation and independent alteration of the electrical properties for each 3-layer fibre within the bundle. Compression and tension are simulated to induce damage at the nerve membrane. Changes in strain, stress distribution and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatized nerve membrane. Results show greater changes in transmitting action potential in the myelinated fibre.

  3. Mechanical Properties of Transgenic Silkworm Silk Under High Strain Rate Tensile Loading (United States)

    Chu, J.-M.; Claus, B.; Chen, W.


    Studies have shown that transgenic silkworm silk may be capable of having similar properties of spider silk while being mass-producible. In this research, the tensile stress-strain response of transgenic silkworm silk fiber is systematically characterized using a quasi-static load frame and a tension Kolsky bar over a range of strain-rates between 10^{-3} and 700/s. The results show that transgenic silkworm silk tends to have higher overall ultimate stress and failure strain at high strain rate (700/s) compared to quasi-static strain rates, indicating rate sensitivity of the material. The failure strain at the high strain rate is higher than that of spider silk. However, the stress levels are significantly below that of spider silk, and far below that of high-performance fiber. Failure surfaces are examined via scanning electron microscopy and reveal that the failure modes are similar to those of spider silk.

  4. Mechanical Properties of Transgenic Silkworm Silk Under High Strain Rate Tensile Loading (United States)

    Chu, J.-M.; Claus, B.; Chen, W.


    Studies have shown that transgenic silkworm silk may be capable of having similar properties of spider silk while being mass-producible. In this research, the tensile stress-strain response of transgenic silkworm silk fiber is systematically characterized using a quasi-static load frame and a tension Kolsky bar over a range of strain-rates between 10^{-3} and 700/s. The results show that transgenic silkworm silk tends to have higher overall ultimate stress and failure strain at high strain rate (700/s) compared to quasi-static strain rates, indicating rate sensitivity of the material. The failure strain at the high strain rate is higher than that of spider silk. However, the stress levels are significantly below that of spider silk, and far below that of high-performance fiber. Failure surfaces are examined via scanning electron microscopy and reveal that the failure modes are similar to those of spider silk.

  5. The significance of dynamical architecture for adaptive responses to mechanical loads during rhythmic behavior. (United States)

    Shaw, Kendrick M; Lyttle, David N; Gill, Jeffrey P; Cullins, Miranda J; McManus, Jeffrey M; Lu, Hui; Thomas, Peter J; Chiel, Hillel J


    Many behaviors require reliably generating sequences of motor activity while adapting the activity to incoming sensory information. This process has often been conceptually explained as either fully dependent on sensory input (a chain reflex) or fully independent of sensory input (an idealized central pattern generator, or CPG), although the consensus of the field is that most neural pattern generators lie somewhere between these two extremes. Many mathematical models of neural pattern generators use limit cycles to generate the sequence of behaviors, but other models, such as a heteroclinic channel (an attracting chain of saddle points), have been suggested. To explore the range of intermediate behaviors between CPGs and chain reflexes, in this paper we describe a nominal model of swallowing in Aplysia californica. Depending upon the value of a single parameter, the model can transition from a generic limit cycle regime to a heteroclinic regime (where the trajectory slows as it passes near saddle points). We then study the behavior of the system in these two regimes and compare the behavior of the models with behavior recorded in the animal in vivo and in vitro. We show that while both pattern generators can generate similar behavior, the stable heteroclinic channel can better respond to changes in sensory input induced by load, and that the response matches the changes seen when a load is added in vivo. We then show that the underlying stable heteroclinic channel architecture exhibits dramatic slowing of activity when sensory and endogenous input is reduced, and show that similar slowing with removal of proprioception is seen in vitro. Finally, we show that the distributions of burst lengths seen in vivo are better matched by the distribution expected from a system operating in the heteroclinic regime than that expected from a generic limit cycle. These observations suggest that generic limit cycle models may fail to capture key aspects of Aplysia feeding

  6. Marginal quality and fracture strength of root-canal treated mandibular molars with overlay restorations after thermocycling and mechanical loading. (United States)

    Dere, Mustafa; Ozcan, Mutlu; Göhring, Till N


    To evaluate marginal quality, fracture modes, and loads-to-failure of different overlay restorations in rootcanal treated molars in a laboratory setup. Thirty-two mandibular first molars were randomly assigned to four groups (n = 8): UTR= untreated (control), RCT-COM= root canal treated (RCT)+ lab-made composite overlay, RCT-FRC= RCT+composite resin overlay with two layers of multidirectional woven glass fibers; RCT-CER: RCT+ceramic overlay. The teeth in all groups were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at 200X at the tooth-to-luting composite (IF1) and luting composite-to restoration (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Data were analyzed with ANOVA and Bonferroni correction. Marginal adaptation decreased from 93 ± 3.4 to 82 ± 6.5 % at IF1 after TCML (p > 0.001) but the decrease was not significant between the groups (p = 0.8130). At IF2, ceramic overlays showed about 10% lower marginal adaptation than composite overlays (p composite delamination from the glass-fiber weaver layer. As cusp-covering overlay restorations in root canal treated molars, composite resin overlays with and without fiber reinforcement performed similar to intact teeth with varying failure types. While intact teeth failed exclusively in reparable modes, all other restorations failed in a catastrophic manner, except half of the fiber reinforced composite group.

  7. A cross-sectional study of the effects of load carriage on running characteristics and tibial mechanical stress: implications for stress fracture injuries in women (United States)


    effects of load carriage on running characteristics and tibial mechanical stress : implications for stress -fracture injuries in women Chun Xu1, Amy Silder2...Ju Zhang3, Jaques Reifman1* and Ginu Unnikrishnan1Abstract Background: Load carriage is associated with musculoskeletal injuries, such as stress ...kinematics and kinetics of the body, as well as the tibial mechanical stress during running. We also compared the biomechanics of walking (studied

  8. Concept of Sustained Ordering and an ATP-related Mechanism of Life’s Origin

    Directory of Open Access Journals (Sweden)

    Erik M. Galimov


    Full Text Available This paper shows that the steadystate of a system of conjugated reactions, which are characterized by disproportionation of entropy and proceed in the domain of linear interactions, is an attractor of ordering. Such systems are primed to produce ordering, and life is a specific manifestation of the sustained ordering inherent to the chemistry of carbon. The adenosine triphospate (ATP molecule has properties which makes ATP hydrolysis to be most appropriate to form such a system in primitive world. Hence, ATP is suggested to play a key role in prebiological evolution. Principles of the origin and evolution of life following from the concept of ordering are stated.

  9. On the mechanical modeling of the extreme softening/stiffening response of axially loaded tensegrity prisms (United States)

    Fraternali, Fernando; Carpentieri, Gerardo; Amendola, Ada


    We study the geometrically nonlinear behavior of uniformly compressed tensegrity prisms through fully elastic and rigid-elastic models. The given models predict a variety of mechanical behaviors in the regime of large displacements, including an extreme stiffening-type response, already known in the literature, and a newly discovered, extreme softening behavior. The latter may lead to a snap buckling event producing an axial collapse of the structure. The switching from one mechanical regime to another depends on the aspect ratio of the structure, the magnitude of the applied prestress, and the material properties of the constituent elements. We discuss potential mechanical and acoustic applications of such behaviors, which are related to the design and manufacture of tensegrity lattices and innovative metamaterials.

  10. Novel use of surveillance data to detect HIV-infected persons with sustained high viral load and durable virologic suppression in New York City.

    Directory of Open Access Journals (Sweden)

    Arpi S Terzian

    Full Text Available BACKGROUND: Monitoring of the uptake and efficacy of ART in a population often relies on cross-sectional data, providing limited information that could be used to design specific targeted intervention programs. Using repeated measures of viral load (VL surveillance data, we aimed to estimate and characterize the proportion of persons living with HIV/AIDS (PLWHA in New York City (NYC with sustained high VL (SHVL and durably suppressed VL (DSVL. METHODS/PRINCIPAL FINDINGS: Retrospective cohort study of all persons reported to the NYC HIV Surveillance Registry who were alive and ≥12 years old by the end of 2005 and who had ≥2 VL tests in 2006 and 2007. SHVL and DSVL were defined as PLWHA with 2 consecutive VLs ≥100,000 copies/mL and PLWHA with all VLs ≤400 copies/mL, respectively. Logistic regression models using generalized estimating equations were used to model the association between SHVL and covariates. There were 56,836 PLWHA, of whom 7% had SHVL and 38% had DSVL. Compared to those without SHVL, persons with SHVL were more likely to be younger, black and have injection drug use (IDU risk. PLWHA with SHVL were more likely to die by 2007 and be younger by nearly ten years, on average. CONCLUSIONS/SIGNIFICANCE: Nearly 60% of PLWHA in 2005 had multiple VLs, of whom almost 40% had DSVL, suggesting successful ART uptake. A small proportion had SHVL, representing groups known to have suboptimal engagement in care. This group should be targeted for additional outreach to reduce morbidity and secondary transmission. Measures based on longitudinal analyses of surveillance data in conjunction with cross-sectional measures such as community viral load represent more precise and powerful tools for monitoring ART effectiveness and potential impact on disease transmission than cross-sectional measures alone.

  11. Sustained release of diclofenac from polymer-containing suppository and the mechanism involved. (United States)

    Azechi, Y; Ishikawa, K; Mizuno, N; Takahashi, K


    Sustained release of diclofenac sodium (DcNa) from suppositories composed of triglycerides and polymer was investigated by dissolution testing through an artificial membrane. DcNa was slowly released from a suppository containing carboxyvinyl polymer (CVP), and the extent of the release decreased with the amount of CVP added. Little effect was noted with the addition of other water-soluble polymers, such as hydroxyethylcellulose (HEC), xanthan gum, and polyvinylalcohol (PVA). When sodium benzoate was used instead of DcNa, a similar result was obtained with the addition of CVP. The result of release rate analysis together with the viscosity and pH in these cases showed that the reduction of solubility and diffusion due to sodium exchange between DcNa and CVP played an important role in the sustained release from the suppository. Also, in comparison with the results when CVP was not used, the plasma concentration profile of diclofenac after the administration of CVP suppository displayed a twofold longer half-life time.

  12. Viscoelastic behaviour of hydrogel-based composites for tissue engineering under mechanical load. (United States)

    Kocen, Rok; Gasik, Michael; Gantar, Ana; Novak, Saša


    Along with biocompatibility, bioinductivity and appropriate biodegradation, mechanical properties are also of crucial importance for tissue engineering scaffolds. Hydrogels, such as gellan gum (GG), are usually soft materials, which may benefit from the incorporation of inorganic particles, e.g. bioactive glass, not only due to the acquired bioactivity, but also due to improved mechanical properties. They exhibit complex viscoelastic properties, which can be evaluated in various ways. In this work, to reliably evaluate the effect of the bioactive glass (BAG) addition on viscoelastic properties of the composite hydrogel, we employed and compared the three most commonly used techniques, analyzing their advantages and limitations: monotonic uniaxial unconfined compression, small amplitude oscillatory shear (SAOS) rheology and dynamic mechanical analysis (DMA). Creep and small amplitude dynamic strain-controlled tests in DMA are suggested as the best ways for the characterization of mechanical properties of hydrogel composites, whereas the SAOS rheology is more useful for studying the hydrogel's processing kinetics, as it does not induce volumetric changes even at very high strains. Overall, the results confirmed a beneficial effect of BAG (nano)particles on the elastic modulus of the GG-BAG composite hydrogel. The Young's modulus of 6.6 ± 0.8 kPa for the GG hydrogel increased by two orders of magnitude after the addition of 2 wt.% BAG particles (500-800 kPa).

  13. The Effect of Aging and Mechanical Loading on the Metabolism of Articular Cartilage

    DEFF Research Database (Denmark)

    Jørgensen, Adam El Mongy; Kjaer, Michael; Heinemeier, Katja Maria


    collagen network damage and proteoglycan loss, leading to irreversible cartilage destruction because of lack of regenerative capacity. Catabolic pathways involve inflammation and the transcription factor nuclear factor-κB. Thus, age seems to be a predisposing factor for OA, with mechanical overload being...

  14. Magnetic and mechanical AC loss of the ITER CSI model coil conductor under transverse cyclic loading

    NARCIS (Netherlands)

    Nijhuis, Arend; Noordman, Niels H.W.; ten Kate, Herman H.J.; Mitchell, Neil; Bruzzone, Pierluigi


    The magnetic field in a coil results in a transverse force on the strands pushing the cable towards one side of the jacket. A special cryogenic press has been built to study in a unique way the mechanical and electrical properties of full-size ITER Cable-in-Conduit (CIC) samples under a transverse,

  15. Nickel release from orthodontic retention wires: the action of mechanical loading and pH

    NARCIS (Netherlands)

    Milheiro, A.; Kleverlaan, C.; Muris, J.; Feilzer, A.; Pallav, P.


    Nickel (Ni) is a potent sensitizer and may induce innate and adaptive immune responses. Ni is an important component of orthodontic appliances (8-50 wt%). Due to chemical and mechanical factors in the oral environment, Ni is released from these appliances. Retention wires are in situ for a long

  16. Francis full-load surge mechanism identified by unsteady 2-phase CFD

    Energy Technology Data Exchange (ETDEWEB)

    Doerfler, P K; Keller, M; Braun, O, E-mail: [R and D Department, Andritz Hydro Ltd., Zurich (Switzerland)


    Francis turbines may produce spontaneous pulsations of pressure and output power when operating at very high discharge. In such cases there is a cavitating central vortex in the draft tube with variable cavity volume V{sub c}. Until today, researchers agree that the main destabilizing agent is the so-called mass flow gain factor, defined as the derivative of cavity volume by the local discharge. Recent studies about 1D high-load stability analysis assumed that the mass-flow gain factor obtained from steady-state vortex data acts on the transient discharge downstream of the cavity. There are however good reasons to question this assumption. Most strikingly, the direct cause of the mass flow gain effect is the increase of swirl produced at the runner exit and hence upstream, not downstream of the cavity. To enhance the reliability of full-load stability predictions, the authors directly investigated the vortex dynamics. The development of the transient cavitating flow in the draft tube was simulated by means of unsteady 2-phase CFD. CFD work started with 1-phase calculations as presented by other authors. This was then extended to a more realistic 2-phase calculation. To contain the computing time within acceptable limits, given the very fine mesh and short time step required, the simulation domain was restricted to the draft tube and, at the same time, the problem was reduced to a basically 2-dimensional rotationally symmetric case. The response of the cavitating draft tube flow to a time-dependent inflow and time-dependent pressure at the draft tube exit was simulated. The results were input to a statistical identification procedure to check possible 1D transient models and find representative parameter values in the sense of a best fit between 1D model and CFD result. As we had suspected, the conventional vortex model with mass flow gain controlled by downstream discharge is not compatible with direct simulation and needs to be modified. The CFD results correspond

  17. Blast-induced neurotrauma: surrogate use, loading mechanisms, and cellular responses. (United States)

    Desmoulin, Geoffrey T; Dionne, Jean-Philippe


    With the onset of improved protective equipment against fragmentation, blast-induced neurotrauma has emerged as the "signature wound" of the current conflicts in the Middle East. Current research has focused on this phenomenon; however, the exact mechanism of injury and ways to mitigate the ensuing pathophysiology remain largely unknown. The data presented and literature reviewed formed the fundamentals of a successful grant from the U.S. Office of Naval Research to Wayne State University. This work is a culmination of specialized blast physics and energy-tissue coupling knowledge, recent pilot data using a 12-m shock tube and an instrumented Hybrid III crash test dummy, modeling results from Conventional Weapons effects software, and an exhaustive Medline and government database literature review. The work supports our hypothesis of the mechanism of injury (described in detail) but sheds light on current hypotheses and how we investigate them. We expose two areas of novel mitigation development. First, there is a need to determine a physiologic and mechanism-based injury tolerance level through a combination of animal testing and biofidelic surrogate development. Once the injury mechanism is defined experimentally and an accurate physiologic threshold for brain injury is established, innovative technologies to protect personnel at risk can be appropriately assessed. Second, activated pathophysiological pathways are thought to be responsible for secondary neurodegeneration. Advanced pharmacological designs will inhibit the key cell signaling pathways. Simultaneously, evaluation of pharmacological candidates will confirm or deny current hypotheses of primary mechanisms of secondary neurodegeneration. A physiologic- or biofidelic-based blast-induced tolerance curve may redefine current acceleration-based curves that are only valid to assess tertiary blast injury. Identification of additional pharmaceutical candidates will both confirm or deny current hypotheses on

  18. A comparative study on the mechanical properties of the healthy and varicose human saphenous vein under uniaxial loading. (United States)

    Karimi, Alireza; Navidbakhsh, Mahdi; Kudo, Susumu


    Saphenous Vein (SV) due to fatness, age, inactiveness, etc. can be afflicted with varicose. The main reason of the varicose vein is believed to be related to the leg muscle pump which is unable to return the blood to the heart in contradiction of the effect of gravity. As a result of the varicose vein, both the structure and mechanical properties of the vein wall would alter. However, so far there is a lack of knowledge on the mechanical properties of the varicose vein. In this study, a comparative study was carried out to measure the elastic and hyperelastic mechanical properties of the healthy and varicose SVs. Healthy and varicose SVs were removed at autopsy and surgery from seven individuals and then axial tensile load was applied to them up to the failure point. In order to investigate the mechanical behaviour of the vein, this study was benefitted from three different stress definitions, such as 2nd Piola-Kichhoff, engineering and true stresses and four different strain definitions, i.e. Almansi-Hamel, Green-St. Venant, engineering and true strains, to determine the linear mechanical properties of the SVs. A Digital Image Correlation (DIC) technique was used to measure the true strain of the vein walls during load bearing. The non-linear mechanical behaviour of the SVs was also computationally evaluated via the Mooney-Rivlin material model. The true/Cauchy stress-strain diagram exhibited the elastic modulus of the varicose SVs as 45.11% lower than that of the healthy ones. Furthermore, by variation of the stress a significant alteration on the maximum stress of the healthy SVs was observed, but then not for the varicose veins. Additionally, the highest stresses of 4.99 and 0.65 MPa were observed for the healthy and varicose SVs, respectively. These results indicate a weakness in the mechanical strength of the SV when it becomes varicose, owing to the degradation of the elastin and collagen content of the SV. The Mooney-Rivlin hyperelastic and the Finite

  19. [Pathogenic factors of regulatory mechanisms of organism adaptation to conditions with a high level of psychoemotional load]. (United States)

    Gorsha, Oksana V; Gorsha, Vasily I


    The urgency of the issue is determined by the value of the stress impact of environmental conditions on workers of the operator personnel contingent, because the deterioration of their health and well-being is a factor in dangerous situations. However, the search for early diagnostic markers forming diseases, with a view to their prevention, is still a challenge. The aim was to establish the most important (among studied) pathogenetic factors of status of regulatory mechanisms of adaptation of individuals with a high level of psychoemotional load that is conditional upon profession. The research is based on the results of the survey of transport operators (114 professional drivers of city passenger electrotransport) and 27 people who had high-level of mental and emotional load due to professional conditions. general clinical; psychological (evaluation of psycho-emotional stability, level of anger, S. Muddy viability test , WHO well-being scale; Beck depression self-rating scale). laboratory (leukogram; cytochemical (the total amount of catecholamines blood; biochemical (cortisol saliva); instrumental (сardiointervalography); determination of the cellular adaptive responses; mathematic. The common data set survey was analyzed by factor analysis- 33 survey criteria, that showed status of health and pathogenic (emotional, behavioral, autonomic, neurohumoral, immune, and cellular) factors of regulatory mechanisms of adaptation of operators to conditions of high psycho-emotional stress. The results established that the main pathogenetic mechanisms of adaptation in drivers of passenger electric transport is possible to consider by four main factors: the integrated mechanisms of autonomic regulation with a predominance of trophotropic effects of parasympathetic; mobilizing influence of the sympathetic nervous system in regulatory mechanisms of adaptation and the level of centralization of heart rate control; state of regulation of systemic hemodynamics, mental health and

  20. Residual stress redistribution in shot peened samples subject to mechanical loading

    Energy Technology Data Exchange (ETDEWEB)

    Buchanan, Dennis J., E-mail: [University of Dayton Research Institute, 300 College Park, Dayton, OH 45469-0020 (United States); John, Reji [Materials and Manufacturing Directorate, Air Force Research Laboratory (AFRL/RXCM), Wright-Patterson Air Force Base, OH 45433-7817 (United States)


    Shot peening is a well-established surface treatment process that imparts large compressive residual stresses onto the surface and at shallow depths to retard initiation and growth of fatigue cracks. The plastic deformation developed during the surface treatment sets up a constraint that retains compressive stresses on the surface balanced by tensile residual stresses in the interior. However, component service histories that produce subsequent plastic deformation may redistribute these residual stresses. In most engineering components, this additional plastic deformation is localized to stress concentration sites such as holes, notches, and fillets. In the case of gross plastic deformation where the entire cross section experiences material yielding the residual stress profile may redistribute, resulting in tensile stresses on the outside surface balanced by compression in the interior. This paper describes a series of experiments combined with models to explain the redistribution in residual stress depth profiles subject to applied stresses producing gross plastic strains in shot peened laboratory specimens. The initial room temperature residual stress and plastic strain profiles provide initial conditions for predictions. Model predictions correlate well with experimental results on shot peened dogbone specimens subject to single cycle and fatigue loading conditions at elevated temperature. Experiments on shot peened notched specimens do not exhibit the same stress redistribution even for larger applied stresses.

  1. Shock loads induced on metal structures by LHC proton beams: modelling of thermo-mechanical effects

    CERN Document Server

    Peroni, L; Dallocchio, A; Bertarelli, A


    In this work, the numerical simulations of the LHC high energy particle beam impact against a metal structure are performed using the commercial FEM code LS-DYNA. The evaluation of thermal loads on the hit material is performed using a statistical code, called FLUKA, based on the Monte-Carlo method, which returns an energy map on a particular geometry (taking into account all the particles in the cascade generated by the interaction between the proton beam and the target). The FLUKA results are then used as input for thermo-structural studies. The first step of this work is the validation of the numerical procedure on a simple geometry for two different materials (copper and tungsten) and constitutive material models. In particular, the high energy particle impact is examined on a facially irradiated cylindrical bar: the beam hits the component directly on the centre of the basis. Then the final step is the study of the impact on a real structure with an energy beam of 5 TeV (the next target in the energy val...

  2. Effect of Fiber Treatment and Fiber Loading on Mechanical Properties of Luffa-Resorcinol Composites

    Directory of Open Access Journals (Sweden)

    Chhatrapati Parida


    Full Text Available Tensile and compressive behaviour of resorcinol-formaldehyde (RF matrix and its composites reinforced with fibers of Luffa cylindrica (LC have been studied. LC fibers were subjected to chemical treatments such as alkali activation by NaOH followed by bleaching and acid hydrolysis in order to improve fiber-matrix adhesion. Both treated and untreated LC fibers are modified with calcium phosphate. The presence of hydroxy apatite, a polymorph of calcium phosphate and a major constituent of vertebrate bone and teeth, was confirmed from XRD peak of treated LC fiber. XRD analysis of the treated LC fiber has confirmed the crystalline nature of the chemically treated LC fiber by its crystallinity index. The effects of fiber loading of chemically treated and untreated LC fiber on ultimate stress, yield strength, breaking stress, and modulus of the composites were analyzed. The tensile and compressive modulus of the composites were increased with incorporation of both treated and untreated LC fibers into the RF matrix. The modulus of composites with treated LC fiber was enhanced compared to that of the untreated fiber composites. Furthermore the values of ultimate stress, yield stress, and breaking stress were increased with the incorporation of treated LC fiber in the composites.

  3. Fretting corrosion of CoCr alloy: Effect of load and displacement on the degradation mechanisms. (United States)

    Bryant, Michael; Neville, Anne


    Fretting corrosion of medical devices is of growing concern, yet, the interactions between tribological and electrochemical parameters are not fully understood. Fretting corrosion of CoCr alloy was simulated, and the components of damage were monitored as a function of displacement and contact pressure. Free corrosion potential (Ecorr), intermittent linear polarisation resistance and cathodic potentiostatic methods were used to characterise the system. Interferometry was used to estimate material loss post rubbing. The fretting regime influenced the total material lost and the dominant degradation mechanism. At high contact pressures and low displacements, pure corrosion was dominant with wear and its synergies becoming more important as the contact pressure and displacement decreased and increased, respectively. In some cases, an antagonistic effect from the corrosion-enhanced wear contributor was observed suggesting that film formation and removal may be present. The relationship between slip mechanism and the contributors to tribocorrosion degradation is presented.

  4. Thermal-Conductivity Characterization of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cells and Electrolyzers Under Mechanical Loading (United States)

    Hamour, M.; Garnier, J. P.; Grandidier, J. C.; Ouibrahim, A.; Martemianov, S.


    Accurate information on the temperature field and associated heat transfer rates is particularly important for proton exchange membrane fuel cells (PEMFC) and PEM electrolyzers. An important parameter in fuel cell and electrolyzer performance analysis is the effective thermal conductivity of the gas diffusion layer (GDL) which is a solid porous medium. Usually, this parameter is introduced in modeling and performance analysis without taking into account the dependence of the GDL thermal conductivity λ (in W · m-1 · K-1) on mechanical compression. Nevertheless, mechanical stresses arising in an operating system can change significantly the thermal conductivity and heat exchange. Metrology allowing the characterization of the GDL thermal conductivity as a function of the applied mechanical compression has been developed in this study using the transient hot-wire technique (THW). This method is the best for obtaining standard reference data in fluids, but it is rarely used for thermal-conductivity measurements in solids. The experiments provided with Quintech carbon cloth indicate a strong dependence (up to 300%) of the thermal conductivity λ on the applied mechanical load. The experiments have been provided in the pressure range 0 cloth layers have been provided. The conducted experiments indicate the independence of the measured thermal conductivity on the number of GDL layers and, thus, justify the robustness of the developed method and apparatus for this type of application.

  5. Numerical Modeling and Experimental Verification for High-Speed and Heavy-Load Planar Mechanism with Multiple Clearances

    Directory of Open Access Journals (Sweden)

    Fangang Meng


    Full Text Available Transmission mechanism is one of the most important parts of the Ultra-High Voltage (UHV circuit breaker. It has specific characteristics such as fast response, high speed, and heavy load in the processes of open and close actions. This paper studies the effects of multiple clearances on the working characteristics of transmission mechanism system, especially the motion of its journal center path during operation. It builds a nonlinear kinetic model of transmission mechanism considering the system energy losses due to the impact and friction between the journal and bearing inside clearance joints. Also, an experimental platform is built to measure the displacement and velocity of the moving contact. The results show that the existence of 15 clearance joints in our mechanism system can cause hysteresis effects on the velocity and acceleration of the moving contact, as well as its acceleration fluctuation. Meanwhile, the increase of friction coefficient will stabilize the dynamic characteristic. In addition, both the experimental and simulation results indicate that the motion of the journal center, which is unevenly distributed along the circle, is characterized by three phases: free flight motion, contact motion, and impact motion.

  6. Modeling and Analysis Tools for Linear and Nonlinear Mechanical Systems Subjected to Extreme Impulsive Loading (United States)


    and seismic motion analysis [3]. In many military and civil applications, nonlinear mechanical wave prop- agation occurs through structural...ture are prepared and performed by using MATLAB . The proposed force iden- tification method is also implemented and studied by using MATLAB and...methods is listed in Table. 3. A Dell desktop with a Intel Core Quad CPU is used for all simulations. The parallel computing toolbox in MATLAB is used to

  7. Methods of Assessing Human Tendon Metabolism and Tissue Properties in Response to Changes in Mechanical Loading

    DEFF Research Database (Denmark)

    Heinemeier, Katja M; Kjaer, Michael; Magnusson, S Peter


    In recent years a number of methodological developments have improved the opportunities to study human tendon. Microdialysis enables sampling of interstitial fluid in the peritendon tissue, while sampling of human tendon biopsies allows direct analysis of tendon tissue for gene- and protein......)), and tendon mechanical properties (ultrasonography combined with force measurement during movement). Finally, 3D cell cultures of human tendon cells provide the opportunity to investigate cell-matrix interactions in response to various interventions....

  8. Fracture Mechanics Analysis of Single and Double Rows of Fastener Holes Loaded in Bearing (United States)


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  9. Effect of Filler Loading on Mechanical and Tribological Properties of Wood Apple Shell Reinforced Epoxy Composite

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    Ojha Shakuntala


    Full Text Available During the last century, natural fibers and particulates are used as reinforcement in polymer composite that has been continuously growing in the composite industry. This polymer matrix composite has wide range of applications in hostile environment where they are exposed to external attacks such as solid particle erosion. Also, the mechanical properties of different polymer composites show the best alternate to replace the metal material. In the present investigation, an attempt has been made to improve the mechanical and tribological behaviour of polymer matrix composite using wood apple shell particles as a filler material in polymer matrix. Also the temperature variation of the dynamic-mechanical parameters of epoxy matrix composites incorporated with 5, 10, 15, and 20 wt% of wood apple shell particles was investigated by DMA test. It is clearly observed that the incorporation of wood apple shell particles tends to increase the tensile strength, flexural strength, erosive wear resistance, and viscoelastic stiffness of the polymer composite. To validate the results, SEM of the polymer matrix composite has been studied.

  10. Analysis of roof membranes damaged by mechanical and climatic loads – pilot research

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    Čurpek Jakub


    Full Text Available Realization of roof construction has many hidden risks, especially in buildings with diverse architecture. There is a problem about cooperation of individual works (vertical and horizontal constructions on roof in this type of architecture, during the process of realization. Purpose of this research is to reveal risks in form of the group of major source of defects by mechanical damages. The most often types of mechanical damages were chosen in this research, which then were applied on individual types of roof membranes. Response of this damage was found out during the test procedure of water pressure by special laboratory machines. Furthermore, samples of roof membranes were subjected to the Impact test, which was actually focused on damage by hailstone impact from the atmosphere. The final outcomes of the measurements show that the material composition of each roof membrane can influence their whole waterproofing after application of certain type of mechanical damage. In the Impact test, samples were suffered from impact of the hails. This test signified that the choice of base material of thermal insulation below the roof membrane plays an important role.

  11. Biaxial flexural strength and phase transformation of Ce-TZP/Al2O3 and Y-TZP core materials after thermocycling and mechanical loading. (United States)

    Bankoğlu Güngör, Merve; Yılmaz, Handan; Aydın, Cemal; Karakoca Nemli, Seçil; Turhan Bal, Bilge; Tıraş, Tülay


    The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (Pstrength of the tested materials.

  12. Pituitary Adenylate Cyclase Activating Polypeptide (PACAP Pathway Is Induced by Mechanical Load and Reduces the Activity of Hedgehog Signaling in Chondrogenic Micromass Cell Cultures

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    Tamás Juhász


    Full Text Available Pituitary adenylate cyclase activating polypeptide (PACAP is a neurohormone exerting protective function during various stress conditions either in mature or developing tissues. Previously we proved the presence of PACAP signaling elements in chicken limb bud-derived chondrogenic cells in micromass cell cultures. Since no data can be found if PACAP signaling is playing any role during mechanical stress in any tissues, we aimed to investigate its contribution in mechanotransduction during chondrogenesis. Expressions of the mRNAs of PACAP and its major receptor, PAC1 increased, while that of other receptors, VPAC1, VPAC2 decreased upon mechanical stimulus. Mechanical load enhanced the expression of collagen type X, a marker of hypertrophic differentiation of chondrocytes and PACAP addition attenuated this elevation. Moreover, exogenous PACAP also prevented the mechanical load evoked activation of hedgehog signaling: protein levels of Sonic and Indian Hedgehogs and Gli1 transcription factor were lowered while expressions of Gli2 and Gli3 were elevated by PACAP application during mechanical load. Our results suggest that mechanical load activates PACAP signaling and exogenous PACAP acts against the hypertrophy inducing effect of mechanical load.

  13. A constitutive model for mechanical response characterization of pumpkin peel and flesh tissues under tensile and compressive loadings. (United States)

    Shirmohammadi, Maryam; Yarlagadda, Prasad K D V; Gu, YuanTong


    Enhancing quality of food products and reducing volume of waste during mechanical operations of food industry requires a comprehensive knowledge of material response under loadings. While research has focused on mechanical response of food material, the volume of waste after harvesting and during processing stages is still considerably high in both developing and developed countries. This research aims to develop and evaluate a constitutive model of mechanical response of tough skinned vegetables under postharvest and processing operations. The model focuses on both tensile and compressive properties of pumpkin flesh and peel tissues where the behaviours of these tissues vary depending on various factors such as rheological response and cellular structure. Both elastic and plastic response of tissue were considered in the modelling process and finite elasticity combined with pseudo elasticity theory was applied to generate the model. The outcomes were then validated using the published results of experimental work on pumpkin flesh and peel under uniaxial tensile and compression. The constitutive coefficients for peel under tensile test was α = 25.66 and β = -18.48 Mpa and for flesh α = -5.29 and β = 5.27 Mpa. under compression the constitutive coefficients were α = 4.74 and β = -1.71 Mpa for peel and α = 0.76 and β = -1.86 Mpa for flesh samples. Constitutive curves predicted the values of force precisely and close to the experimental values. The curves were fit for whole stress versus strain curve as well as a section of curve up to bio yield point. The modelling outputs had presented good agreement with the empirical values and the constructive curves exhibited a very similar pattern to the experimental curves. The presented constitutive model can be applied next to other agricultural materials under loading in future.

  14. Cargo-shell and cargo-cargo couplings govern the mechanics of artificially loaded virus-derived cages (United States)

    Llauró, Aida; Luque, Daniel; Edwards, Ethan; Trus, Benes L.; Avera, John; Reguera, David; Douglas, Trevor; Pablo, Pedro J. De; Castón, José R.


    Nucleic acids are the natural cargo of viruses and key determinants that affect viral shell stability. In some cases the genome structurally reinforces the shell, whereas in others genome packaging causes internal pressure that can induce destabilization. Although it is possible to pack heterologous cargoes inside virus-derived shells, little is known about the physical determinants of these artificial nanocontainers' stability. Atomic force and three-dimensional cryo-electron microscopy provided mechanical and structural information about the physical mechanisms of viral cage stabilization beyond the mere presence/absence of cargos. We analyzed the effects of cargo-shell and cargo-cargo interactions on shell stability after encapsulating two types of proteinaceous payloads. While bound cargo to the inner capsid surface mechanically reinforced the capsid in a structural manner, unbound cargo diffusing freely within the shell cavity pressurized the cages up to ~30 atm due to steric effects. Strong cargo-cargo coupling reduces the resilience of these nanocompartments in ~20% when bound to the shell. Understanding the stability of artificially loaded nanocages will help to design more robust and durable molecular nanocontainers.Nucleic acids are the natural cargo of viruses and key determinants that affect viral shell stability. In some cases the genome structurally reinforces the shell, whereas in others genome packaging causes internal pressure that can induce destabilization. Although it is possible to pack heterologous cargoes inside virus-derived shells, little is known about the physical determinants of these artificial nanocontainers' stability. Atomic force and three-dimensional cryo-electron microscopy provided mechanical and structural information about the physical mechanisms of viral cage stabilization beyond the mere presence/absence of cargos. We analyzed the effects of cargo-shell and cargo-cargo interactions on shell stability after encapsulating two

  15. Some growth factors stimulate cultured adult rabbit ventricular myocyte hypertrophy in the absence of mechanical loading (United States)

    Decker, R. S.; Cook, M. G.; Behnke-Barclay, M.; Decker, M. L.


    Cultured adult rabbit cardiac myocytes treated with recombinant growth factors display enhanced rates of protein accumulation (ie, growth) in response to insulin and insulin-like growth factors (IGFs), but epidermal growth factor, acidic or basic fibroblast growth factor, and platelet-derived growth factor failed to increase contractile protein synthesis or growth of the heart cells. Insulin and IGF-1 increased growth rates by stimulating anabolic while simultaneously inhibiting catabolic pathways, whereas IGF-2 elevated growth modestly by apparently inhibiting lysosomal proteolysis. Neutralizing antibodies directed against either IGF-1 or IGF-2 or IGF binding protein 3 blocked protein accumulation. A monoclonal antibody directed against the IGF-1 receptor also inhibited changes in protein turnover provoked by recombinant human IGF-1 but not IGF-2. Of the other growth factors tested, only transforming growth factor-beta 1 increased the fractional rate of myosin heavy chain (MHC) synthesis, with beta-MHC synthesis being elevated and alpha-MHC synthesis being suppressed. However, the other growth factors were able to modestly stimulate the rate of DNA synthesis in this preparation. Bromodeoxyuridine labeling revealed that these growth factors increased DNA synthesis in myocytes and nonmyocytes alike, but the heart cells displayed neither karyokinesis or cytokinesis. In contrast, cocultures of cardiac myocytes and nonmyocytes and nonmyocyte-conditioned culture medium failed to enhance the rate of cardiac MHC synthesis or its accumulation, implying that quiescent heart cells do not respond to "conditioning" by cardiac nonmyocytes. These findings demonstrated that insulin and the IGFs promote passively loaded cultured adult rabbit heart cells to hypertrophy but suggest that other growth factors tested may be limited in this regard.

  16. On mechanism of non-heating sterilization using the underwater shock wave loading and gas formation

    Directory of Open Access Journals (Sweden)

    Ayumi Takemoto


    Full Text Available In the field where the thermal sterilization can’t be applied, the establishment of the sterilization technology with non-heating is strongly requested. The sterilization by pressurizing is one of the sterilization technology. Especially, the underwater shock wave causes scarcely heat in pressurizing because the pressurizing time is extremely short. That is, it is thought that the underwater shock wave enables non-heating sterilization that originates only in pressure. Hence, in this research, the underwater shock wave loading caused by explosive was used for non-heating sterilization. Saccharomyces cerevisiae, one of the budding yeast was used for experiments. S. cerevisiae starts fermentation by feeding the glucose, and causes CO2 within its body. There is the great density difference between cells of S. cerevisiae and the gas, hence, the acoustic impedance is different on the underwater shock wave transmission. Therefore, a strong reflected wave is caused on the boundary of the cell and the gas, and a remarkable expansion is caused. Fermented S. cerevisiae are sterilized by this phenomenon, and showed high sterilization rates. The sterilization rate by the underwater shock wave was low for not giving the glucose, that is, S. cerevisiae that had not fermented. The sterilization rate that had been done on three conditions was as follows in the order of higher. 1 Fermenting S. cerevisiae, high pressure. 2 Fermenting S. cerevisiae, low pressure. 3 Non-fermenting S. cerevisiae, high pressure. The detonation fuse was used in this experiment. There was an interesting phenomenon, that is, the sterilization rate was high at the side of detonation beginning, and it was decreased toward the direction. It is thought that this is related to a constant angle of the shock wave caused from the detonation fuse. A corresponding result to the phenomenon was gotten by the numerical analysis between the progress of the detonation and the change of pressure.

  17. Fracture mechanics analyses of ceramic/veneer interface under mixed-mode loading. (United States)

    Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui


    Few studies have focused on the interface fracture performance of zirconia/veneer bilayered structure, which plays an important role in dental all-ceramic restorations. The purpose of this study was to evaluate the fracture mechanics performance of zirconia/veneer interface in a wide range of mode-mixities (at phase angles ranging from 0° to 90°), and to examine the effect of mechanical properties of the materials and the interface on the fracture initiation and crack path of an interfacial crack. A modified sandwich test configuration with an oblique interfacial crack was proposed and calibrated to choose the appropriate geometry dimensions by means of finite element analysis. The specimens with different interface inclination angles were tested to failure under three-point bending configuration. Interface fracture parameters were obtained with finite element analyses. Based on the interfacial fracture mechanics, three fracture criteria for crack kinking were used to predict crack initiation and propagation. In addition, the effects of residual stresses due to coefficient of thermal expansion mismatch between zirconia and veneer on the crack behavior were evaluated. The crack initiation and propagation were well predicted by the three fracture criteria. For specimens at phase angle of 0, the cracks propagated in the interface; whereas for all the other specimens the cracks kinked into the veneer. Compressive residual stresses in the veneer can improve the toughness of the interface structure. The results suggest that, in zirconia/veneer bilayered structure the veneer is weaker than the interface, which can be used to explain the clinical phenomenon that veneer chipping rate is larger than interface delamination rate. Consequently, a veneer material with larger fracture toughness is needed to decrease the failure rate of all-ceramic restorations. And the coefficient of thermal expansion mismatch of the substrates can be larger to produce larger compressive

  18. Sustained Inflation at Birth Did Not Alter Lung Injury from Mechanical Ventilation in Surfactant-Treated Fetal Lambs (United States)

    Hillman, Noah H.; Kemp, Matthew W.; Miura, Yuichiro; Kallapur, Suhas G.; Jobe, Alan H.


    Background Sustained inflations (SI) are used with the initiation of ventilation at birth to rapidly recruit functional residual capacity and may decrease lung injury and the need for mechanical ventilation in preterm infants. However, a 20 second SI in surfactant-deficient preterm lambs caused an acute phase injury response without decreasing lung injury from subsequent mechanical ventilation. Hypothesis A 20 second SI at birth will decrease lung injury from mechanical ventilation in surfactant-treated preterm fetal lambs. Methods The head and chest of fetal sheep at 126±1 day GA were exteriorized, with tracheostomy and removal of fetal lung fluid prior to treatment with surfactant (300 mg in 15 ml saline). Fetal lambs were randomized to one of four 15 minute interventions: 1) PEEP 8 cmH2O; 2) 20 sec SI at 40 cmH2O, then PEEP 8 cmH2O; 3) mechanical ventilation with 7 ml/kg tidal volume; or 4) 20 sec SI then mechanical ventilation at 7 ml/kg. Fetal lambs remained on placental support for the intervention and for 30 min after the intervention. Results SI recruited a mean volume of 6.8±0.8 mL/kg. SI did not alter respiratory physiology during mechanical ventilation. Heat shock protein (HSP) 70, HSP60, and total protein in lung fluid similarly increased in both ventilation groups. Modest pro-inflammatory cytokine and acute phase responses, with or without SI, were similar with ventilation. SI alone did not increase markers of injury. Conclusion In surfactant treated fetal lambs, a 20 sec SI did not alter ventilation physiology or markers of lung injury from mechanical ventilation. PMID:25419969

  19. Delamination onset in polymeric composite laminates under thermal and mechanical loads (United States)

    Martin, Roderick H.


    A fracture mechanics damage methodology to predict edge delamination is described. The methodology accounts for residual thermal stresses, cyclic thermal stresses, and cyclic mechanical stresses. The modeling is based on the classical lamination theory and a sublaminate theory. The prediction methodology determines the strain energy release rate, G, at the edge of a laminate and compares it with the fatigue and fracture toughness of the composite. To verify the methodology, isothermal static tests at 23, 125, and 175 C and tension-tension fatigue tests at 23 and 175 C were conducted on laminates. The material system used was a carbon/bismaleimide, IM7/5260. Two quasi-isotropic layups were used. Also, 24 ply unidirectional double cantilever beam specimens were tested to determine the fatigue and fracture toughness of the composite at different temperatures. Raising the temperature had the effect of increasing the value of G at the edge for these layups and also to lower the fatigue and fracture toughness of the composite. The static stress to edge delamination was not affected by temperature but the number of cycles to edge delamination decreased.

  20. Metal resistance or tolerance? Acidophiles confront high metal loads via both abiotic and biotic mechanisms

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    Mark eDopson


    Full Text Available All metals are toxic at high concentrations and consequently their intracellular concentrations must be regulated. Acidophilic microorganisms have an optimum growth pH < 3 and proliferate in natural and anthropogenic low pH environments. Some acidophiles are involved in the catalysis of sulfide mineral dissolution, resulting in high concentrations of metals in solution. Acidophiles are often described as highly metal resistant via mechanisms such as multiple and/or more efficient active resistance systems than are present in neutrophiles. However, this is not the case for all acidophiles and we contend that their growth in high metal concentrations is partially due to an intrinsic tolerance as a consequence of the environment in which they live. In this perspective, we highlight metal tolerance via complexation of free metals by sulfate ions and passive tolerance to metal influx via an internal positive cytoplasmic transmembrane potential. These tolerance mechanisms have been largely ignored in past studies of acidophile growth in the presence of metals and should be taken into account.

  1. Effect of mechanical load cycling on the microleakage of three different glass ionomer restorations in class V cavities

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    Baharan Ranjbar Omidi


    Full Text Available Background and Aims: Microleakage is an important problem with direct restorations and familiarity with contributing factors is of utmost importance. The aim of this study was to evaluate the microleakage of three glass ionomer restorations in class V cavities.   Materials and Methods: In this in vitro study, class V cavity preparations were made on the buccal and lingual/ palatal surfaces of 30 human premolars (60 cavities. The specimens were divided into three group (n=10, 20 cavities. Restored as follows: group1: with Fuji IX (HVGI ionomer/G coat plus, group 2: Ionofil molar (HVGI/ G coat plus, and group 3: Fuji II LC (RMGI / G coat plus. All specimens were finished and polished immediately and were thermocycled (2000 cycles, 5-50°C . In each group; half of the teeth were load cycled (50000 cycles. Finally, the teeth were immersed in 0.15% basic fushine dye for 24 hours at room temperature and then sectioned and observed under stereomicroscope. Data were analyzed using Kruskal-Wallis, Man- Whitney test and a comparison between incisal and gingival microleakage was made using Wilcoxon analysis.   Results: It was shown that the mechanical load cycling and filling material did not cause a statistically significant increase in the incisal and gingival microleakage in any of groups (P>0.05.   Conclusion: It was concluded that the extent microleakage of Fuji II LC was similar to that of the highly viscous glass ionomers (Ionofil molar, Fuji IX and load cycling did not increase the microleakage.

  2. Mechanisms of basin-scale nitrogen load reductions under intensified irrigated agriculture.

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    Rebecka Törnqvist

    Full Text Available Irrigated agriculture can modify the cycling and transport of nitrogen (N, due to associated water diversions, water losses, and changes in transport flow-paths. We investigate dominant processes behind observed long-term changes in dissolved inorganic nitrogen (DIN concentrations and loads of the extensive (465,000 km2 semi-arid Amu Darya River basin (ADRB in Central Asia. We specifically considered a 40-year period (1960-2000 of large irrigation expansion, reduced river water flows, increased fertilizer application and net increase of N input into the soil-water system. Results showed that observed decreases in riverine DIN concentration near the Aral Sea outlet of ADRB primarily were due to increased recirculation of irrigation water, which extends the flow-path lengths and enhances N attenuation. The observed DIN concentrations matched a developed analytical relation between concentration attenuation and recirculation ratio, showing that a fourfold increase in basin-scale recirculation can increase DIN attenuation from 85 to 99%. Such effects have previously only been observed at small scales, in laboratory experiments and at individual agricultural plots. These results imply that increased recirculation can have contributed to observed increases in N attenuation in agriculturally dominated drainage basins in different parts of the world. Additionally, it can be important for basin scale attenuation of other pollutants, including phosphorous, metals and organic matter. A six-fold lower DIN export from ADRB during the period 1981-2000, compared to the period 1960-1980, was due to the combined result of drastic river flow reduction of almost 70%, and decreased DIN concentrations at the basin outlet. Several arid and semi-arid regions around the world are projected to undergo similar reductions in discharge as the ADRB due to climate change and agricultural intensification, and may therefore undergo comparable shifts in DIN export as shown here

  3. Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

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    Ngoc-Trung Nguyen


    Full Text Available Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally.

  4. Mechanical Behavior of a Series of Copolyester Blends near the Glass Transition: Monotonic and Load-Hold Behavior in Compression

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    Gurucharan Chandrasekaran


    Full Text Available Monotonic loading tests were conducted on five commercial blends of poly(ethylene terephthalate (PET and poly(1,4-cyclohexylenedimethylene terephthalate (PCT at temperatures of 90°C and 100°C and strain rates of 0.1/s, 0.05/s, and 0.005/s in uniaxial and plane strain compression. On comparing the mechanical behavior of the five materials, it was found that the behavior of the low-PCT content materials was different from the high-PCT content materials only at conditions that favored strain-induced crystallization, particularly in plane strain compression. Load-hold tests were also conducted on three of the blends with similar results to the monotonic tests. Material differences were only pronounced at certain conditions, and in these cases the low-PCT content materials showed increased strain hardening after the hold period while the high-PCT content material did not. Therefore, it was found that the addition of a hold period was not exclusively required to observe differences in the crystallizable materials over the noncrystallizing blends. The increased strain hardening likely associated with crystallization in PET was only observed when the following conditions were met: (i strain rates of 0.1/s and above, (ii temperatures of 90°C–100°C, (iii plane strain compression, and (iv after a certain level of deformation.

  5. Thermal-mechanical-chemical responses of polymer-bonded explosives using a mesoscopic reactive model under impact loading. (United States)

    Wang, XinJie; Wu, YanQing; Huang, FengLei


    A mesoscopic framework is developed to quantify the thermal-mechanical-chemical responses of polymer-bonded explosive (PBX) samples under impact loading. A mesoscopic reactive model is developed for the cyclotetramethylenetetranitramine (HMX) crystal, which incorporates nonlinear elasticity, crystal plasticity, and temperature-dependent chemical reaction. The proposed model was implemented in the finite element code ABAQUS by the user subroutine VUMAT. A series of three-dimensional mesoscale models were constructed and calculated under low-strength impact loading scenarios from 100m/s to 600m/s where only the first wave transit is studied. Crystal anisotropy and microstructural heterogeneity are responsible for the nonuniform stress field and fluctuations of the stress wave front. At a critical impact velocity (≥300m/s), a chemical reaction is triggered because the temperature contributed by the volumetric and plastic works is sufficiently high. Physical quantities, including stress, temperature, and extent of reaction, are homogenized from those across the microstructure at the mesoscale to compare with macroscale measurements, which will advance the continuum-level models. The framework presented in this study has important implications in understanding hot spot ignition processes and improving predictive capabilities in energetic materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Strength and Fracture Mechanisms of Nanostructured Metallic Materials Under Single Kinds of Loading (United States)

    Klevtsov, G. V.; Valiev, R. Z.; Klevtsova, N. A.; Zaripov, N. G.; Karavaeva, M. V.


    The effect of nanostructuring on the strength and fracture mechanism of materials possessing different crystal lattices is analyzed on the basis of available reports and experimental data of the authors. The structure, the hardness, the crack resistance, and the strength and ductility characteristics of steel 10 (bcc lattice), aluminum alloy AK4-1 (fcc lattice), austenitic steel AISI 321 (fcc lattice) are studied after equal channel angular pressing (ECAP) and those of Grade 4 titanium (hcp lattice) are studied after a ECAP-conform process (ECAP-C). It is shown that the ultrafine-grained (UFG) structure produced by the ECAP affects ambiguously the static crack resistance of the materials studied. The type of the crystal lattice influences substantially the temperature behavior of the impact toughness of the studied materials with UFG structure.

  7. Mechanical Design of a Hybrid Leg Exoskeleton to Augment Load-Carrying for Walking

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    Yunjie Miao


    Full Text Available An innovative lower extremity exoskeleton, SJTU-EX, is demonstrated in Shanghai JiaoTong University, which mainly aims to help soldiers and workers to support a payload in motion. This paper summarizes the mechanical design of SJTU-EX. Each pseudo-anthropomorphic leg of SJTU-EX has four active joints and two passive joints, and the joint ranges are optimized in consideration of both safety factors and the realization of typical motions. Springs are applied in the leg to eliminate the effect of gravity. The results of dynamic simulations are used to determine the actuated joints and the passive joints. Novel Hy-Mo actuators are introduced for SJTU-EX and the layout of the actuator for Diamond Side 2 is described in detail as a design example.

  8. Enhanced breakdown strength of polymer composites by low filler loading and its mechanisms (United States)

    Ding, Shanjun; Yu, Shuhui; Zhu, Xiaodong; Xie, Shenghui; Sun, Rong; Liao, Wei-Hsin; Wong, Ching-Ping


    Dielectric polymer materials with high energy density and low dielectric loss are highly desired for applications in advanced electronic devices and electric power systems. Here, we report on flexible dielectric composites using semiconductor nanoparticles as fillers and polyvinylidene fluoride (PVDF) as a matrix. The introduction of a small amount of ZnO filler results in significantly enhanced voltage breakdown strength and energy density in comparison with pure PVDF. Based on the multi-core model, combining the electric double layer theory and the interface contact theory, we investigate mechanisms and come out with that transportation of carriers under applied voltage is regulated by the charged interface, which delays the formation of the conduction path. Besides, the electric field imposed on the composites is alleviated by the internal micro-electric field.

  9. [Electrochemical properties of biocompatible material hardness modifications on titanium and steel under mechanical loads]. (United States)

    Braun, W; Walter, U; Holbein, R; Thull, R


    Friction corrosion may appear between different implant components or between implant and hard tissue. The sliding micro movements induce fretting wear corrosion and have been recently reported as a cause of joint prostheses failure. A surface coating is desirable, that retains the mechanical properties of the substrate, offers good biocompatibility and improves the fretting corrosion resistance. In this study it could be demonstrated that tantalum and niobium coatings fulfill the requirements. On titanium substrates the coating decreases the abrasion against PMMA, an orthopedic relevant material. Furthermore, in the case of medical steel substrates the biocompatibility and the corrosion properties are improved. The better abrasion-resistance is minimizing the release of allergological critical particles like nickel and chromium.

  10. Statistical Mechanics of Coherent Ising Machine — The Case of Ferromagnetic and Finite-Loading Hopfield Models — (United States)

    Aonishi, Toru; Mimura, Kazushi; Utsunomiya, Shoko; Okada, Masato; Yamamoto, Yoshihisa


    The coherent Ising machine (CIM) has attracted attention as one of the most effective Ising computing architectures for solving large scale optimization problems because of its scalability and high-speed computational ability. However, it is difficult to implement the Ising computation in the CIM because the theories and techniques of classical thermodynamic equilibrium Ising spin systems cannot be directly applied to the CIM. This means we have to adapt these theories and techniques to the CIM. Here we focus on a ferromagnetic model and a finite loading Hopfield model, which are canonical models sharing a common mathematical structure with almost all other Ising models. We derive macroscopic equations to capture nonequilibrium phase transitions in these models. The statistical mechanical methods developed here constitute a basis for constructing evaluation methods for other Ising computation models.

  11. Use of the Frank-Starling mechanism during exercise is linked to exercise-induced changes in arterial load (United States)

    Chantler, Paul D.; Melenovsky, Vojtech; Schulman, Steven P.; Gerstenblith, Gary; Becker, Lewis C.; Ferrucci, Luigi; Fleg, Jerome L.; Najjar, Samer S.


    Effective arterial elastance(EA) is a measure of the net arterial load imposed on the heart that integrates the effects of heart rate(HR), peripheral vascular resistance(PVR), and total arterial compliance(TAC) and is a modulator of cardiac performance. To what extent the change in EA during exercise impacts on cardiac performance and aerobic capacity is unknown. We examined EA and its relationship with cardiovascular performance in 352 healthy subjects. Subjects underwent rest and exercise gated scans to measure cardiac volumes and to derive EA[end-systolic pressure/stroke volume index(SV)], PVR[MAP/(SV*HR)], and TAC(SV/pulse pressure). EA varied with exercise intensity: the ΔEA between rest and peak exercise along with its determinants, differed among individuals and ranged from −44% to +149%, and was independent of age and sex. Individuals were separated into 3 groups based on their ΔEAI. Individuals with the largest increase in ΔEA(group 3;ΔEA≥0.98 mmHg.m2/ml) had the smallest reduction in PVR, the greatest reduction in TAC and a similar increase in HR vs. group 1(ΔEAgroup 3 had a reduction in end-diastolic volume, and a blunted increase in SV(80%), and cardiac output(27%), during exercise vs. group 1. Despite limitations in the Frank-Starling mechanism and cardiac function, peak aerobic capacity did not differ by group because arterial-venous oxygen difference was greater in group 3 vs. 1. Thus the change in arterial load during exercise has important effects on the Frank-Starling mechanism and cardiac performance but not on exercise capacity. These findings provide interesting insights into the dynamic cardiovascular alterations during exercise. PMID:22003052

  12. A Novel High Mechanical Property PLGA Composite Matrix Loaded with Nanodiamond-Phospholipid Compound for Bone Tissue Engineering. (United States)

    Zhang, Fan; Song, Qingxin; Huang, Xuan; Li, Fengning; Wang, Kun; Tang, Yixing; Hou, Canglong; Shen, Hongxing


    A potential bone tissue engineering material was produced from a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), loaded with nanodiamond phospholipid compound (NDPC) via physical mixing. On the basis of hydrophobic effects and physical absorption, we modified the original hydrophilic surface of the nanodiamond (NDs) with phospholipids to be amphipathic, forming a typical core-shell structure. The ND-phospholipid weight ratio was optimized to generate sample NDPC50 (i.e., ND-phospholipid weight ratio of 100:50), and NDPC50 was able to be dispersed in a PLGA matrix at up to 20 wt %. Compared to a pure PLGA matrix, the introduction of 10 wt % of NDPC (i.e., sample NDPC50-PF10) resulted in a significant improvement in the material's mechanical and surface properties, including a decrease in the water contact angle from 80 to 55°, an approximately 100% increase in the Young's modulus, and an approximate 550% increase in hardness, thus closely resembling that of human cortical bone. As a novel matrix supporting human osteoblast (hFOB1.19) growth, NDPC50-PFs with different amounts of NDPC50 demonstrated no negative effects on cell proliferation and osteogenic differentiation. Furthermore, we focused on the behaviors of NDPC-PFs implanted into mice for 8 weeks and found that NDPC-PFs induced acceptable immune response and can reduce the rapid biodegradation of PLGA matrix. Our results represent the first in vivo research on ND (or NDPC) as nanofillers in a polymer matrix for bone tissue engineering. The high mechanical properties, good in vitro and in vivo biocompatibility, and increased mineralization capability suggest that biodegradable PLGA composite matrices loaded with NDPC may potentially be useful for a variety of biomedical applications, especially bone tissue engineering.

  13. Light-sustained cooperative mechanisms observed at liquid junctions of chalcopyrite semiconductors (United States)

    Cattarin, S.; Tributsch, H.


    Electrochemical oscillations previously shown to occur during hydrogen peroxide reduction of natural samples of copper-containing sulfides (e.g. Cu 5FeS 4) have also been produced with synthetic chalcopyrites (CuMeX 2 with Me=Fe, In, X=S, Se). It is possible partly to control this cooperative phenomenon by photoexcitation of p-type CuInS 2 and p-type CuInSe 2, semiconductor electrodes. With illumination as a key factor in the control of cooperative phenomena it should be possible to explore non-linear photoelectrochemical mechanisms with possible applications to solar energy conversion. The cooperative phenomenon studied involves the interaction of electrons with copper (in oxidation states I, II and III) and oxygen and thus might be related to the cooperative mechanism causing high-temperature superconduction in copper oxide phases.

  14. Sensitivity-Based Modeling of Evaluating Surface Runoff and Sediment Load using Digital and Analog Mechanisms

    Directory of Open Access Journals (Sweden)

    Olotu Yahaya


    Full Text Available Analyses of runoff- sediment measurement and evaluation using automated and convectional runoff-meters was carried out at Meteorological and Hydrological Station of Auchi Polytechnic, Auchi using two runoff plots (ABCDa and EFGHm of area 2m 2 each, depth 0.26 m and driven into the soil to the depth of 0.13m. Runoff depths and intensities were measured from each of the positioned runoff plot. Automated runoff-meter has a measuring accuracy of ±0.001l/±0.025 mm and rainfall depth-intensity was measured using tipping-bucket rainguage during the period of 14-month of experimentation. Minimum and maximum rainfall depths of 1.2 and 190.3 mm correspond to measured runoff depths (MRo of 0.0 mm for both measurement approaches and 60.4 mm and 48.9 mm respectively. Automated runoffmeter provides precise, accurate and instantaneous result over the convectional measurement of surface runoff. Runoff measuring accuracy for automated runoff-meter from the plot (ABCDa produces R 2 = 0.99; while R 2 = 0.96 for manual evaluation in plot (EFGHm. WEPP and SWAT models were used to simulate the obtained hydrological variables from the applied measurement mechanisms. The outputs of sensitivity simulation analysis indicate that data from automated measuring systems gives a better modelling index and such could be used for running robust runoff-sediment predictive modelling technique under different reservoir sedimentation and water management scenarios.

  15. Eco-design of low energy mechanical milling through implementation of quality function deployment and design for sustainability (United States)

    Rashid, Muhammad Hanif Abd; Nor, Nik Hisyamudin Muhd; Selamat, Siti Norhana; Hassan, Mohd Fahrul; Rahim, Abd Khalil Abd; Ahmad, Mohd Fauzi; Ismail, Al Emran; Omar, Badrul; Mokhtar, Mohd Faiz; Turan, Faiz Mohd; Yokoyama, Seiji


    Malaysia as a developing country favor energy demand by years which created mainly from fossil fuel. Unfortunately, the action leads to significant increment in carbon dioxide (CO2) emission that causing the global warming. The most promising mitigation strategy is by deploying Carbon Capture and Storage (CCS) technology where mineral carbonation was identified as the safest method for permanent storage and does not require continuous monitoring. Accordingly, National Green Technology was launched in 2009 to support the growth of green technology development in Malaysia as a carbon mitigation strategy. Thus, this paper aims to propose the development of a conceptual eco-design for Low Energy Mechanical Milling (LEMM). The concept was proposed by using the Quality Function Deployment (QFD) tool with combination of sustainability determinants (DFS) namely economic, environmental and social which evaluated using Solidworks 2015 sustainability assessment. The results show the new product targets for LEMM in prior on energy consumption (MJ), selling price (MYR), material cost (MYR), carbon footprint (kg CO2) with weightage of 5.2, 4.2, 3.6 and 3.6 respectively. The implementation of DFS criteria into the QFD promote to reduce material used by 16%, 35% reduction of carbon footprint, 28% less energy consumption, 28% lower air acidification, 77% of water eutrophication declined and increased recyclability by 15%.

  16. The use of 3d scanner for testing changes in shape of human limbs under the influence of external mechanical load (United States)

    Kasperska, Kamila; Wieczorowski, Michał; Krolczyk, Jolanta B.


    Three-dimensional scanning is used in many fields: medicine, architecture, industry, reverse engineering. The aim of the article was to analyze the changes in the shape of the limbs under the influence of a mechanical external load using the method of three-dimensional scanner uses white light technology. The paper presents a system of human movement, passive part - skeleton and active part - the muscles, and principles of their interaction, which results in a change of the position of the body. Furthermore, by using the 3D scan, the differences in appearance of the arm and leg depending on the size of the external load in different positions have been presented. The paper shows that with increasing load, which muscles must prevent, increases the volume of certain parts of the legs, while another parts of them will be reduced. Results of the research using three-dimensional scanner allow determining what impact on changing the legs shape has an external mechanical load.

  17. Investigation of Deposit Formation Mechanisms for Engine In-cylinder Combustion and Exhaust Systems Using Quantitative Analysis and Sustainability Study (United States)

    Ye, Z.; Meng, Q.; Mohamadian, H. P.; Wang, J. T.; Chen, L.; Zhu, L.


    The formation of SI engine combustion deposits is a complex phenomenon which depends on various factors of fuel, oil, additives, and engine. The goal of this study is to examine the effects of operating conditions, gasoline, lubricating oil, and additives on deposit formation. Both an experimental investigation and theoretical analysis are conducted on a single cylinder engine. As a result, the impact of deposits on engine performance and exhaust emissions (HC, NO x ) has been indicated. Using samples from a cylinder head and exhaust pipe as well as switching gases via the dual-gas method (N2, O2), the deposit formation mechanism is thoroughly investigated via the thermogravity analysis approach, where the roles of organic, inorganic, and volatile components of fuel, additives, and oil on deposit formation are identified from thermogravity curves. Sustainable feedback control design is then proposed for potential emission control and performance optimization

  18. Mechanical Characterization and Finite Element Implementation of the SoftMaterials used in a Novel Anthropometric Test Device for SimulatingUnderbody Blast Loading (United States)


    Materials used in a Novel Anthropometric Test Device for Simulating Underbody Blast Loading by Wade A Baker, Costin D Untaroiu, Dawn M Crawford, and...used in a Novel Anthropometric Test Device for Simulating Underbody Blast Loading by Wade A Baker and Costin D Untaroiu Virginia Tech, Department...SUBTITLE Mechanical Characterization and Finite Element Implementation of the Soft Materials used in a Novel Anthropometric Test Device for



    S. N. Leonovich


    The paper presents calculations pertaining to survivability of NPS load-carrying elements with respect to crack-resistance. These calculations reflect their resistance ability to actions of mechanical, thermal, hydro-dynamic, electro-magnetic  loads in the case when there are defects in the elements (initially technological defects or operational ones). The most dangerous defects are micro- and macro-cracks that create maximum high concentration of stresses and deformations.


    Directory of Open Access Journals (Sweden)

    S. N. Leonovich


    Full Text Available The paper presents calculations pertaining to survivability of NPS load-carrying elements with respect to crack-resistance. These calculations reflect their resistance ability to actions of mechanical, thermal, hydro-dynamic, electro-magnetic  loads in the case when there are defects in the elements (initially technological defects or operational ones. The most dangerous defects are micro- and macro-cracks that create maximum high concentration of stresses and deformations.

  1. Multi-objective optimization of a functionally graded sandwich panel under mechanical loading in the presence of stress constraint (United States)

    Ashjari, Mohammad; Khoshravan, Mohammad Reza


    A method was presented for multi-objective optimization of material distribution of simply supported functionally graded (FG) sandwich panel, and sensitivity analyses of optimal designs were also conducted based on design variables and objective functions. The material composition was assumed to vary only in the thickness direction. Piecewise cubic interpolation of volume fractions was used to calculate volume fractions of constituent material phases at a point; these fractions were defined at a limited number of evenly spaced control points. The effective material properties of the panel were obtained by applying the linear rule of mixtures. The behavior of FG sandwich panel was predicted by Reddy's assumptions of third-order shear deformation theory. Exact solutions for deflections and stresses of simply supported sandwich panel were presented using the Navier-type solution technique. The volume fractions at control points, material, and thickness of the faces which were selected as decision variables were optimized by a multi-objective evolutionary algorithm known as the fast and elitist multi-objective genetic algorithm (NSGA-II). The mass and deflection of the model were considered the objective functions to be minimized with stress constraints. This model was optimized to verify the capability and efficiency of the proposed model under mechanical loading. The framework proposed for designing FG sandwich panel under pure mechanical conditions was furnished by the results.

  2. Expanded graphite loaded with lanthanum oxide used as a novel adsorbent for phosphate removal from water: performance and mechanism study. (United States)

    Zhang, Ling; Gao, Yan; Li, Mengxue; Liu, Jianyong


    A novel adsorbent of expanded graphite (EG) loaded with lanthanum oxide (EG-LaO) was prepared for phosphate removal from water and characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. The effects of impregnation time, La3+ concentration, activation time, and activation temperature on the phosphate removal performance of the adsorbent were studied for optimization of preparation conditions. Isothermal adsorption studies suggested that the Langmuir model fits the experimental data well. Adsorption kinetics investigation showed that the pseudo-second-order model fits the experimental data quite well, indicating that the adsorption process is mainly a process of chemical adsorption, and chloride ions compete to react with the active sites of the adsorbent but do not prevent phosphate from adsorbing onto EG-LaO. The adsorption mechanism studies were performed by a pH dependence study of the adsorption amount. The results demonstrated that the probable mechanisms of phosphate adsorption on EG-LaO were electrostatic and Lewis acid-base interactions in addition to ion exchange.

  3. Application of iron and zinc isotopes to track the sources and mechanisms of metal loading in a mountain watershed (United States)

    Borrok, D.M.; Wanty, R.B.; Ian, Ridley W.; Lamothe, P.J.; Kimball, B.A.; Verplanck, P.L.; Runkel, R.L.


    Here the hydrogeochemical constraints of a tracer dilution study are combined with Fe and Zn isotopic measurements to pinpoint metal loading sources and attenuation mechanisms in an alpine watershed impacted by acid mine drainage. In the tested mountain catchment, ??56Fe and ??66Zn isotopic signatures of filtered stream water samples varied by ???3.5??? and 0.4???, respectively. The inherent differences in the aqueous geochemistry of Fe and Zn provided complimentary isotopic information. For example, variations in ??56Fe were linked to redox and precipitation reactions occurring in the stream, while changes in ??66Zn were indicative of conservative mixing of different Zn sources. Fen environments contributed distinctively light dissolved Fe (+0.4???). Acidic drainage from mine wastes contributed heavier dissolved Fe (???+0.5???) and lighter Zn (???+0.2???) isotopes relative to the fen. Upwelling of Fe-rich groundwater near the mouth of the catchment was the major source of Fe (??56Fe ??? 0???) leaving the watershed in surface flow, while runoff from mining wastes was the major source of Zn. The results suggest that given a strong framework for interpretation, Fe and Zn isotopes are useful tools for identifying and tracking metal sources and attenuation mechanisms in mountain watersheds. ?? 2009 Elsevier Ltd.

  4. Improved clean development mechanism and joint implementation to promote holistic sustainable development - an integrated policy and methodology for international energy collaboration

    Energy Technology Data Exchange (ETDEWEB)

    Kua Harn Wei


    The current Clean Development Mechanism/Joint Implementation framework does not emphasize on wholistic sustainability of energy projects. The Golden Standard was a good example of how this framework can be fine-tuned. However, it does not explicitly incentivize the adoption of the sustainability standards it outlines. A 4-element integrated policy strategy is proposed. A Sustainability Assessment Matrix is constructed to evaluate project proposals' sustainability performance. The Probational Sustainability Performance Demand requires continual monitoring of this performance of approved projects throughout a designated probation period. The involved countries will be awarded Sustainability Credits (measured with the matrix) in installments according to their performance within this period. The Probational Emission Reduction Demand requires investing countries to meet moderated emission reduction targets in order for them to claim the certified emission reductions/ emission reduction credits and their share of Sustainability Credits. These credits are converted into Sustainability Assistance Funds, which can be channeled back to finance either the approved projects or independent renewable energy projects in the involved countries. The MIT Energy Cost Model is used to estimate the required amount and identify the forms of such assistance package. Finally, an integrated policymaking framework is suggested to execute and monitor these interconnected policy elements. (auth)

  5. Bone Growth, Mechanical Stimulus and IGF-I

    National Research Council Canada - National Science Library

    Gilsanz, Vicente


    .... The aim of this project is to establish whether bone acquisition in teenagers who have sustained a fracture and have low bone mass can be enhanced by changing environmental factors, such as mechanical loading...

  6. Hot Press as a Sustainable Direct Recycling Technique of Aluminium: Mechanical Properties and Surface Integrity (United States)

    Lajis, Mohd Amri; Ahmad, Azlan


    Meltless recycling technique has been utilized to overcome the lack of primary resources, focusing on reducing the usage of energy and materials. Hot press was proposed as a novel direct recycling technique which results in astoundingly low energy usage in contrast with conventional recycling. The aim of this study is to prove the technical feasibility of this approach by characterizing the recycled samples. For this purpose, AA6061 aluminium chips were recycled by utilizing hot press process under various operating temperature (Ts = 430, 480, and 530 °C) and holding times (ts = 60, 90, and 120 min). The maximum mechanical properties of recycled chip are Ultimate tensile strength (UTS) = 266.78 MPa, Elongation to failure (ETF) = 16.129%, while, for surface integrity of the chips, the calculated microhardness is 81.744 HV, exhibited at Ts = 530 °C and ts = 120 min. It is comparable to theoretical AA6061 T4-temper where maximum UTS and microhardness is increased up to 9.27% and 20.48%, respectively. As the desired mechanical properties of forgings can only be obtained by means of a final heat treatment, T5-temper, aging after forging process was employed. Heat treated recycled billet AA6061 (T5-temper) are considered comparable with as-received AA6061 T6, where the value of microhardness (98.649 HV) at 175 °C and 120 min of aging condition was revealed to be greater than 3.18%. Although it is quite early to put a base mainly on the observations in experimental settings, the potential for significant improvement offered by the direct recycling methods for production aluminium scrap can be clearly demonstrated. This overtures perspectives for industrial development of solid state recycling processes as environmentally benign alternatives of current melting based practices. PMID:28771207

  7. Human Dental Pulp-Derived Cells Produce Bone-Like Tissue and Exhibit Bone Cell-Like Responsiveness to Mechanical Loading

    DEFF Research Database (Denmark)

    Kraft, David Christian Evar; Melsen, Birte; Bindslev, Dorthe Arenholt


    Recent studies have shown that dental pulp cells possess stem cell like potential and thus may be potential candidates for tissue engineering purposes particularly in the oro-facial region. Successful tissue engineering ideally requires that newly formed bone adapts its mass, shape, and trabecular...... architecture to the prevailing mechanical load and should be able to conduct bone cell-specific functions, such as bone remodeling. In vitro investigation of the responsiveness of different cell types to mechanical loading is so far a relative new research field. The aim of this study was to establish...... and characterize cell lines from human 3rd molar dental pulp tissue to determine whether human dental pulp-derived cells (DPCs) are osteogenic and responsive to mechanical loading by pulsating fluid flow (PFF) in vitro. Methods: Human DPCs used for this study were characterized by measuring proliferation...

  8. The Effect of Altering the Mechanical Loading Environment on the Expression of Bone Regenerating Molecules in Cases of Distraction Osteogenesis

    Directory of Open Access Journals (Sweden)

    Mohammad M Alzahrani


    Full Text Available Distraction osteogenesis (DO is a surgical technique where gradual and controlled separation of two bony fragments following an osteotomy leads to the induction of new bone formation in the distracted gap. DO is used for limb lengthening, correction of bony deformities and the replacement of bone loss secondary to infection, trauma and tumors. Although DO gives satisfactory results in most cases, one major drawback of this technique is the prolonged period of time the external fixator has to be kept on until the newly formed bone consolidates thus leading to numerous complications. Numerous attempts at accelerating bone formation during DO have been reported. One specific approach is manipulation of the mechanical environment during DO by applying changes in the standard protocol of distraction. Attempts at changing this mechanical environment led to mixed results. Increasing the rate or applying acute distraction, led to poor bone formation in the distracted zone. On the other hand, the addition of compressive forces (such as weight bearing, alternating distraction with compression or by over-lengthening and then shortening has been reported to increase bone formation. It still remains unclear why these alterations may lead to changes in bone formation. While the cellular and molecular changes occurring during the standard DO protocol, specifically increased expression of transforming growth factor-β1, platelet derived growth factor, insulin-like growth factor, basic fibroblast growth factor, vascular endothelial growth factor, and bone morphogenic proteins have been extensively investigated, the literature is sparse on the changes occurring when this protocol is altered. It is the purpose of this article to review the pertinent literature on the changes in the expression of various proteins and molecules as a result of changes in the mechanical loading technique in DO and try to define potential future research directions.

  9. Admixtures in Cement-Matrix Composites for Mechanical Reinforcement, Sustainability, and Smart Features. (United States)

    Bastos, Guillermo; Patiño-Barbeito, Faustino; Patiño-Cambeiro, Faustino; Armesto, Julia


    For more than a century, several inclusions have been mixed with Portland cement-nowadays the most-consumed construction material worldwide-to improve both the strength and durability required for construction. The present paper describes the different families of inclusions that can be combined with cement matrix and reviews the achievements reported to date regarding mechanical performance, as well as two other innovative functionalities of growing importance: reducing the high carbon footprint of Portland cement, and obtaining new smart features. Nanomaterials stand out in the production of such advanced features, allowing the construction of smart or multi-functional structures by means of thermal- and strain-sensing, and photocatalytic properties. The first self-cleaning concretes (photocatalytic) have reached the markets. In this sense, it is expected that smart concretes will be commercialized to address specialized needs in construction and architecture. Conversely, other inclusions that enhance strength or reduce the environmental impact remain in the research stage, in spite of the promising results reported in these issues. Despite the fact that such functionalities are especially profitable in the case of massive cement consumption, the shift from the deeply established Portland cement to green cements still has to overcome economic, institutional, and technical barriers.

  10. Sustainable and smart keratin hydrogel with pH-sensitive swelling and enhanced mechanical properties. (United States)

    Peralta Ramos, María Luz; González, Joaquín Antonio; Fabian, Lucas; Pérez, Claudio Javier; Villanueva, María Emilia; Copello, Guillermo Javier


    Protein based hydrogels are a very interesting type of biomaterials with many probed strengths related to their source and chemical structure. Biocompatibility and biodegradability are accompanied by affordability when it comes to low cost sources. The main keratin source is agroindustrial waste, such as feathers, horns, hooves, hair and wool. Thus, the main cost of keratin hydrogels derives from their processing. Here is presented a new strategy for the obtaining of a keratin hydrogel with enhanced mechanical properties using low cost reagents. This keratin hydrogel is stiff enough to allow handling without special cares and also presenting a reversible pH-responsive behavior. The minimum swelling is observed at low pH due to a collapsed and disordered protein network with water tightly adsorbed to the hydrophilic sites. The swelling rises significantly above pH6 and the maximum swelling appears above pH8 where an expanded network allows water to enter to the pores. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Sustainable power generation in microbial fuel cells using bicarbonate buffer and proton transfer mechanisms. (United States)

    Fan, Yanzhen; Hu, Hongqiang; Liu, Hong


    Phosphate buffer solution has been commonly used in MFC studiesto maintain a suitable pH for electricity-generating bacteria and/or to increase the solution conductivity. However, addition of a high concentration of phosphate buffer in MFCs could be expensive, especially for wastewater treatment. In this study, the performances of MFCs with cloth electrode assemblies (CEA) were evaluated using bicarbonate buffer solutions. A maximum power density of 1550 W/m3 (2770 mW/ m2) was obtained at a current density of 0.99 mA/cm2 using a pH 9 bicarbonate buffer solution. Such a power density was 38.6% higher than that using a pH 7 phosphate buffer at the same concentration of 0.2 M. Based on the quantitative comparison of free proton transfer rates, diffusion rates of pH buffer species, and the current generated, a facilitated proton transfer mechanism was proposed for MFCs in the presence of the pH buffers. The excellent performance of MFCs using bicarbonate as pH buffer and proton carrier indicates that bicarbonate buffer could be served as a low-cost and effective pH buffer for practical applications, especially for wastewater treatment.

  12. Direct effect of infliximab on intestinal mucosa sustains mucosal healing: exploring new mechanisms of action. (United States)

    Petito, Valentina; Lopetuso, Loris Riccardo; Arena, Vincenzo; Stigliano, Egidio; Boninsegna, Alma; Bibbò, Stefano; Poscia, Andrea; Alfieri, Sergio; Rosa, Fausto; Amato, Arianna; Cammarota, Giovanni; Papa, Alfredo; Sgambato, Alessandro; Gasbarrini, Antonio; Scaldaferri, Franco


    Infliximab is effective in inflammatory bowel disease through several mechanisms, possibly acting at the mucosal level. To assess the role of infliximab on intestinal mucosa and whether it contributes to mucosal healing. Human colonic mucosal biopsies were incubated with or without infliximab. Cultured biopsies were evaluated for histological staining, CD68, CD3, E-cadherin and phospho-extracellular signal-regulated kinases (ERK) expression, and apoptosis. A scratch assay and MTT assay were performed with Caco2 cells in the presence of infliximab and/or tumour necrosis factor (TNF)-α or treated with supernatants obtained from human peripheral blood mononuclear cells or human intestinal fibroblasts treated with TNF-α and infliximab alone or in association. Infliximab-treated biopsies displayed a better histological appearance, reduced inflammation with an increase of E-cadherin, phospho-ERK and apoptosis. Supernatants showed lower TNF-α, IL-17, IL-6 and IL-8 concentration, with an increase in fibroblast-growth-factor. Motility at scratch assay and proliferation at MTT assay of Caco2 cells displayed differential modulation by TNF-α and infliximab, directly or through supernatants of human intestinal fibroblasts and human peripheral blood mononuclear cells exposed to them. Infliximab contributes to the mucosal healing process by acting directly at an intestinal mucosal level; infliximab indirectly affects epithelial cell migration and proliferation by acting on both fibroblasts and leukocytes. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

  13. Expression of insulin-like growth factor I, insulin-like growth factor binding proteins, and collagen mRNA in mechanically loaded plantaris tendon

    DEFF Research Database (Denmark)

    Olesen, Jens L; Heinemeier, Katja M; Haddad, Fadia


    . However, it is not known whether MGF is expressed and upregulated in mechanically loaded tendon. This study examined the effect of mechanical load on tendon collagen mRNA in relation to changes in the IGF-I systems mRNA expression. Data were collected at 2, 4, 8 and 16 days after surgical removal...... of synergistic muscle to the plantaris muscle of the rat, thus increasing the load to plantaris muscle and tendon. Nearly a doubling of the tendon mass was observed after 16 days of loading. A rapid rise in tendon procollagen III mRNA was seen after 2 days whereas the increase in procollagen I m......RNA was significant from day 8. MGF was expressed and upregulated in loaded tendon tissue with a faster response than IGF-I, which was increased from day 8. Finally, IGFBP-4 mRNA was increased with a time pattern similar to procollagen III, whereas IGFBP-5 decreased at day 8. In conclusion, loading of tendon tissue...

  14. The Capacity-Building Stewardship Model: assessment of an agricultural network as a mechanism for improving regional agroecosystem sustainability

    Directory of Open Access Journals (Sweden)

    Alison J. Duff


    Full Text Available Working lands have potential to meet agricultural production targets while serving as reservoirs of biological diversity and as sources of ecological services. Yet agricultural policy creates disincentives for this integration of conservation and production goals. While necessary, the development of a policy context that promotes agroecosystem sustainability will take time, and successful implementation will depend on a receptive agricultural audience. As the demands placed on working lands grow, there is a need for regional support networks that build agricultural producers' capacity for land stewardship. We used a social-ecological system framework to illustrate the Healthy Grown Potato Program as an agricultural network case study. Our Capacity-Building Stewardship Model reflects a 20-year experience working in collaboration with potato growers certified under an ecolabel in Wisconsin, USA. The model applies an evolving, modular farm stewardship standard to the entire farm - croplands and noncroplands. The model demonstrates an effective process for facilitating communication and shared learning among program participants, including agricultural producers, university extension specialists, nonprofit conservation partners, and industry representatives. The limitation of the model in practice has been securing funding to support expansion of the program and to ensure that the ecolabel standard is responsive to changes in the social-ecological system. Despite this constraint, the Capacity-Building Stewardship Model reveals an important mechanism for building regional commitment to conservation, with agricultural producers in a leadership role as architects, adopters, and advocates for stewardship behavior. Our experience provides important insight for the application of agri-environment schemes on private lands. The durability of a conservation ethic on working farms is likely to be enhanced when networks engage and support producers in an

  15. Evaluating Moisture Control of Variable-Capacity Heat Pumps in Mechanically Ventilated, Low-Load Homes in Climate Zone 2A

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Eric [University of Central Florida, Florida Solar Energy Center; Withers, Chuck [University of Central Florida, Florida Solar Energy Center; McIlvaine, Janet [University of Central Florida, Florida Solar Energy Center; Chasar, Dave [University of Central Florida, Florida Solar Energy Center; Beal, David [University of Central Florida, Florida Solar Energy Center


    The well-sealed, highly insulated building enclosures constructed by today's home building industry coupled with efficient lighting and appliances are achieving significantly reduced heating and cooling loads. These low-load homes can present a challenge when selecting appropriate space-conditioning equipment. Conventional, fixed-capacity heating and cooling equipment is often oversized for small homes, causing increased first costs and operating costs. Even if fixed-capacity equipment can be properly specified for peak loads, it remains oversized for use during much of the year. During these part-load cooling hours, oversized equipment meets the target dry-bulb temperatures very quickly, often without sufficient opportunity for moisture control. The problem becomes more acute for high-performance houses in humid climates when meeting ASHRAE Standard 62.2 recommendations for wholehouse mechanical ventilation.

  16. Increased extracellular collagen matrix in myocardial sleeves of pulmonary veins: an additional mechanism facilitating repetitive rapid activities in chronic pacing-induced sustained atrial fibrillation. (United States)

    Chiu, Yung-Tsung; Wu, Tsu-Juey; Wei, Hao-Ji; Cheng, Ching-Chang; Lin, Nai-Nu; Chen, Ying-Tsung; Ting, Chih-Tai


    Increased ECM in canine PVs. Cell uncoupling due to fibrosis or increased extracellular collagen matrix (ECM) affects the formation of ectopic focal activity. Whether or not the increase of ECM also exists in the pulmonary veins (PVs) with rapid atrial pacing is unknown. We sought to test the hypothesis that in chronic atrial pacing dogs with sustained atrial fibrillation (AF), the amount of ECM was increased in both atria and the PVs. We induced sustained AF in dogs by rapid atrial pacing. Computerized mapping techniques were used to map both atria and the PVs. We also used histological assessment to quantify the amount of ECM. After 118+/-24 days of rapid atrial pacing, sustained AF was induced in 7 dogs. Repetitive rapid activities (RRAs) either continuously or intermittently arose from the PVs during sustained AF. Histological study shows that there was no fibrosis in both atrial free walls and the PVs. However, the amount of ECM was increased in these regions. The mean ECM surface area fraction at each region in the dogs with sustained AF was all significantly higher compared to the corresponding region in normal dogs. Similarly, the heterogeneity of the ECM surface area fraction at each region in the dogs with sustained AF was also all significantly higher compared to normal dogs. In chronic atrial pacing-induced sustained AF, structural remodeling (i.e., inhomogeneous increase of ECM) also involves the PVs. Reduced coupling of the myocytes in the PV due to histological changes may provide an additional mechanism facilitating RRAs.

  17. First-line cART regimen impacts the course of CD8+ T-cell counts in HIV-infected patients that achieve sustained undetectable viral load. (United States)

    Poizot-Martin, Isabelle; Allavena, Clotilde; Delpierre, Cyrille; Duvivier, Claudine; Obry-Roguet, Véronique; Cano, Carla E; Guillouet de Salvador, Francine; Rey, David; Dellamonica, Pierre; Cheret, Antoine; Cuzin, Lise; Katlama, Christine; Cabié, André; Hoen, Bruno


    The aim of the study was to investigate the impact of first-line combined antiretroviral therapy (cART) regimen on the course of CD8 T-cell counts in human immunodeficiency virus (HIV)-infected patients.A retrospective observational study conducted on the French DAT'AIDS Cohort of HIV-infected patients.We selected 605 patients initiating a first-line cART between 2002 and 2009, and which achieved a sustained undetectable HIV plasma viral load (pVL) for at least 12 months without cART modification. The evolution of CD8 T-cell counts according to cART regimen was assessed.CD8 T-cell counts were assessed in 572 patients treated with 2NRTIs+1PI/r (n= 297), 2NRTIs+1NNRTI (n= 207) and 3NRTIs (n= 68). In multivariate analysis, after 12 months of follow-up, the 3NRTIs regimen was associated with a significantly smaller decrease of CD8 T-cell count compared with NNRTI-containing regimens (-10.2 cells/μL in 3NRTIs vs -105.1 cells/μL; P=0.02) but not compared with PI-containing regimens (10.2 vs -60.9 cells/μL; P=0.21). After 24 months, the 3NRTIs regimen was associated with a smaller decrease of CD8 T-cell count and % compared with PI/r- and NNRTI-containing regimens (0.2 in 3NRTIs vs -9.9 with PI/r-regimens, P=0.001, and vs -11.1 with NNRTI-regimens, p < 0.0001). A focus analysis on 11 patients treated with an INSTI-containing cART regimen during the study period showed after 12 months of follow-up, a median decrease of CD8 T-cell count of -155 [inter quartile range: -302; -22] cells/μL.Our data highlight the fact that cART regimens have differential effects on CD8 pool down regulation.

  18. Experimental study on thermal effect on infiltration mechanisms of glycerol into ZSM-5 zeolite under cyclic loadings (United States)

    Zhang, Yafei; Li, Na; Luo, Rui; Zhang, Yifeng; Zhou, Qulan; Chen, Xi


    Understanding the fundamental infiltration mechanisms under thermal response is of crucial importance to design and develop nanoporous energy systems. In this work, a glycerol/ZSM-5 zeolite-based pressure-driven energy absorption system was built, while the temperature-dependent intrusion of glycerol molecules into lyophobic nanopores of ZSM-5 zeolite and the underlying mechanisms were experimentally studied. By changing the system temperature, the correlations of infiltration pressure with the infiltration and defiltration percentages of the liquid phase under thermal response were explored. It turns out that lifting the system temperature will reduce the critical infiltration pressure barriers and change the system’s wettability. The equivalent surface tension and contact angle are calculated to elucidate the thermal dependence of the system’s wettability. Elevating system temperature can also help enlarge the entry area of the nanochannels and trigger more glycerol molecules to flow out of the nanochannels, which means an increase of the infiltration and defiltration percentages. Weakened hydrogen bonding interaction, temperature sensitivity of glycerol viscosity, and the inherent gas phase in the nanoporous channels may contribute to the infiltration and outflow process at a higher temperature level. Cyclic loadings were applied under each working condition to test the recoverability of the built system. Results showed that the system’s throughput shrank in the first three/four cycles and became stable afterwards. Lifting the system temperature could enhance both intrusion and extrusion processes, thus helping the system reach a faster throughput balance, which is beneficial in establishing a recoverable and reusable energy absorption/storage/conversion system.

  19. Development of Mechanical Loading Device for testing the zirconium cladding under the pellet-cladding interaction conditions

    Directory of Open Access Journals (Sweden)

    V. I. Solonin


    Full Text Available Currently, there is a tendency of transition to the long-term cycles of operation with fuel and to the new transitional modes. This fact requires extra experimental validation for design of fuel rods. New operating conditions are expanding operability requirements of claddings.To implement the experimental techniques the Mechanical Loading Device (MLD was developed, capable of providing the conditions of stress-strain state similar to the pellet-cladding interaction (PCI during operation of the reactor.Complex strain state of a fuel rod cladding is simulated by the impacting force on the plunger and then on the simulator of the fuel pellet. The simulator is made of interposer of zirconium and the inset made of ceramic - aluminum oxide. Mechanical properties of the aluminum oxide are similar to the material of the fuel pellet - uranium dioxide. Experiments conducted on the layout and the MLD as such have shown that a stress-strain state matches with that of under operating conditions of the fuel rod in the reactor.The developed device and test method allows us to simulate a wide range of reactor transient modes. Claddings can be used both in the delivered state, and with the further preparation, including the exposure in nuclear reactor. MLD design enables us to carry out experiments with the presence of an aggressive environment inside the cladding, simulating the presence of gaseous fission products in the fuel rod.For further the development of this research it is necessary to design the laboratory complex for MLD. Extra computational verification experiment is needed as well. In particular, stresses in the cladding achieved during the experiment ought to be calculated. Calculated stresses are required to make project justification on the performance capability of fuel rods.

  20. Colistin-entrapped liposomes driven by the electrostatic interaction: Mechanism of drug loading and in vivo characterization. (United States)

    Li, Yang; Tang, Chengcheng; Zhang, Enbo; Yang, Li


    The potential in vivo application of liposome for polycationic colistin has been hindered by the poor entrapment efficiency (EE) due to their phospholipid membrane permeability. The objective of this study is to investigate the loading mechanism and validity of applying electrostatic attraction for the colistin entrapment and delivery in liposomes. Anionic lipids with various structures were used for colistin entrapment, and the properties of resulting liposomes (i.e. zeta-potential, EE and release rate) were highly dependent on the structure of anionic lipids. Based on consideration of intermolecular interactions, the retention of electrostatically entrapped colistin is essentially determined by the balance of interfacial hydrophobic attraction and electrostatic repulsion. The liposomal colistin showed the reduced bacterial killing rate, but did not compromise the in vitro antibacterial activity. Specially, the PEGylated liposomal colistin of sodium cholesteryl sulfate (Chol-SO4(-)) showed the best drug retention, resulting in the significantly increased maximum-tolerated dose, prolonged blood circulation and decreased colistin distribution in kidney after intravenous administration in mice. These results highlight the potential utility of electrostatically entrapped liposome for polycationic colistin delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. In vivo passive mechanical properties of skeletal muscle improve with massage-like loading following eccentric exercise. (United States)

    Haas, Caroline; Best, Thomas M; Wang, Qian; Butterfield, Timothy A; Zhao, Yi


    A quasi-linear viscoelasticity (QLV) model was used to study passive time-dependent responses of skeletal muscle to repeated massage-like compressive loading (MLL) following damaging eccentric exercise. Six skeletally mature rabbits were surgically instrumented with bilateral peroneal nerve cuffs for stimulation of the hindlimb tibialis anterior (TA) muscles. Following the eccentric exercise, rabbits were randomly assigned to a four-day MLL protocol mimicking deep effleurage (0.5 Hz, 10 N for 15 min or for 30 min). The contralateral hindlimb served as the exercised, no-MLL control for both MLL conditions. Viscoelastic properties of the muscle pre-exercise, post-exercise on Day 1, and pre- and post-MLL Day 1 through Day 4 were determined with ramp-and-hold tests. The instantaneous elastic response (AG(0)) increased following exercise (p0.05). This is the first experimental evidence of the effect of both acute (daily) and cumulative changes in viscoelastic properties of intensely exercised muscle due to ex vivo MLL. It provides a starting point for correlating passive muscle properties with mechanical effects of manual therapies, and may shed light on design and optimization of massage protocols. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. The Effect of Flexible Pavement Mechanics on the Accuracy of Axle Load Sensors in Vehicle Weigh-in-Motion Systems. (United States)

    Burnos, Piotr; Rys, Dawid


    Weigh-in-Motion systems are tools to prevent road pavements from the adverse phenomena of vehicle overloading. However, the effectiveness of these systems can be significantly increased by improving weighing accuracy, which is now insufficient for direct enforcement of overloaded vehicles. Field tests show that the accuracy of Weigh-in-Motion axle load sensors installed in the flexible (asphalt) pavements depends on pavement temperature and vehicle speeds. Although this is a known phenomenon, it has not been explained yet. The aim of our study is to fill this gap in the knowledge. The explanation of this phenomena which is presented in the paper is based on pavement/sensors mechanics and the application of the multilayer elastic half-space theory. We show that differences in the distribution of vertical and horizontal stresses in the pavement structure are the cause of vehicle weight measurement errors. These studies are important in terms of Weigh-in-Motion systems for direct enforcement and will help to improve the weighing results accuracy.

  3. Effect of compaction load and sintering temperature on the mechanical properties of the Al-SiC nano-composite materials (United States)

    Iqbal, AKM Asif; Lim, Mei Jing; Nuruzzaman, Dewan Muhammad


    The development of metal matrix composites (MMCs) has set the stage for a new revolution in materials. In this research, Al matrix composites reinforced with SiC nanoparticles were fabricated by a powder metallurgy process and the effects of compaction load and sintering temperature on the mechanical properties of the Al-SiC nano-composite was investigated. The samples were prepared with two different compaction loads, 100 kN and 200 kN, and two different sintering temperatures, 550 °C and 600 °C. Subsequently, their mechanical testing was carried out. The density and hardness of the samples were investigated. The microstructure of the nano-composite was examined by optical microscope. The results showed that the higher compaction load and higher sintering temperature significantly increased the density and hardness of the nano-composite materials.

  4. Sustainable sanitary landfills for neglected small cities in developing countries: The semi-mechanized trench method from Villanueva, Honduras

    Energy Technology Data Exchange (ETDEWEB)

    Oakley, Stewart M., E-mail: [Department of Civil Engineering, Chico State University, California State University, Chico, CA 95929 (United States); Jimenez, Ramon, E-mail: [Public Works, Municipality of Villanueva, Cortes (Honduras)


    Highlights: Black-Right-Pointing-Pointer Open dumping is the most common form of waste disposal in neglected small cities. Black-Right-Pointing-Pointer Semi-mechanized landfills can be a sustainable option for small cities. Black-Right-Pointing-Pointer We present the theory of design and operation of semi-mechanized landfills. Black-Right-Pointing-Pointer Villanueva, Honduras has operated its semi-mechanized landfill for 15 years. Black-Right-Pointing-Pointer The cost of operation is US$4.60/ton with a land requirement of 0.2m{sup 2}/person-year. - Abstract: Open dumping is the most common practice for the disposal of urban solid wastes in the least developed regions of Africa, Asia and Latin America. Sanitary landfill design and operation has traditionally focused on large cities, but cities with fewer than 50,000 in population can comprise from 6% to 45% of a given country's total population. These thousands of small cities cannot afford to operate a sanitary landfill in the way it is proposed for large cities, where heavy equipment is used to spread and compact the waste in daily cells, and then to excavate, transport and apply daily cover, and leachate is managed with collection and treatment systems. This paper presents an alternative approach for small cities, known as the semi-mechanized trench method, which was developed in Villanueva, Honduras. In the semi-mechanized trench method a hydraulic excavator is used for 1-3 days to dig a trench that will last at least a month before it is filled with waste. Trucks can easily unload their wastes into the trench, and the wastes compact naturally due to semi-aerobic biodegradation, after which the trenches are refilled and covered. The exposed surface area is minimal since only the top surface of the wastes is exposed, the remainder being covered by the sides and bottom of the trench. The surplus material from trench excavation can be valorized for use as engineering fill onsite or off. The landfill in

  5. Soldier occupational load carriage: a narrative review of associated injuries. (United States)

    Orr, Robin Marc; Pope, Rodney; Johnston, Venerina; Coyle, Julia


    This narrative review examines injuries sustained by soldiers undertaking occupational load carriage tasks. Military soldiers are required to carry increasingly heavier occupational loads. These loads have been found to increase the physiological cost to the soldier and alter their gait mechanics. Aggregated research findings suggest that the lower limbs are the most frequent anatomical site of injury associated with load carriage. While foot blisters are common, other prevalent lower limb injuries include stress fractures, knee and foot pain, and neuropathies, like digitalgia and meralgia. Shoulder neuropathies (brachial plexus palsy) and lower back injuries are not uncommon. Soldier occupational load carriage has the potential to cause injuries that impact on force generation and force sustainment. Through understanding the nature of these injuries targeted interventions, like improved physical conditioning and support to specialised organisations, can be employed.

  6. Biomolecular Cell-Signaling Mechanisms and Dental Implants: A Review on the Regulatory Molecular Biologic Patterns Under Functional and Immediate Loading. (United States)

    Romanos, Georgios E


    Bone tissue adapts its structure and mass to the stresses of mechanical loading. The purpose of this review article was to summarize recent advances on cell signaling relating to the phenomenon of bone remodeling, focused on bone ossification and healing at the interface of dental implants and bone under loading conditions. When a dental implant is placed within an osteotomy, osteocytes, osteoblasts, and osteoclasts are all present. As functional loads are imposed, the remodeling processes adapt the peri-implant bony tissues to mechanical stimuli over time and reestablish a steady state. Based on the current literature, this article demonstrates fundamental information to these remodeling processes, such as the conversion of mechanical cues to electrical or biochemical signals. Multiple intracellular signals are involved in cellular mechanotransduction; the two Wnt signaling pathways (the canonical, β-catenin-dependent and the noncanonical, β-catenin-independent Wnt pathway) are particularly significant. Knowledge of how these molecular signaling pathways are translated into intracellular signals that regulate cell behavior may provide new therapeutic approaches to enhancing osteogenesis, especially around implants with immediate function or placed in areas of poor bone quality. New knowledge about the primary cilia as an organelle and bone cellular mechanosensor is critical for endochondral ossification and proper signal transduction. Other mechanisms, such as the expression of sclerostin as a negative regulator of bone formation (due to deactivation of the Wnt receptor) and downregulation of sclerostin under loading conditions, also present new understanding of the cellular and pericellular mechanics of bone. The complexity of the cell signaling pathways and the mechanisms involved in the mechanoregulation of the bone formation provide new technologies and perspectives for mechanically induced cellular response. Future novel therapeutic approaches based on the

  7. Bone response and mechanical strength of rabbit femoral defects filled with injectable CaP cements containing TGF-beta 1 loaded gelatin microparticles.

    NARCIS (Netherlands)

    Link, D.P.; Dolder, J. van den; Beucken, J.J.J.P van den; Wolke, J.G.C.; Mikos, A.G.; Jansen, J.A.


    This study focused at the potential of transforming growth factor beta 1 (TGF-beta 1) loaded gelatin microparticles to enhance the bone response and mechanical strength of rabbit femoral defects filled with injectable calcium phosphate (CaP)/gelatin microparticle composites. Therefore, TGF-beta1

  8. Load and depth sensing indentation as a tool to monitor a gradient in the mechanical properties across a polymer coating: A study of physical and chemical aging effects

    NARCIS (Netherlands)

    Boersma, A.; Soloukhin, V.A.; Brokken-Zijp, J.C.M.; With, G. de


    Load and depth sensing indentation has been used to characterize the elastic modulus and hardness of various polycarbonate films. This analytical technique is shown to be extremely suitable for the determination of gradients in these mechanical properties. Furthermore, it is demonstrated that such a

  9. A cross-sectional study of the effects of load carriage on running characteristics and tibial mechanical stress: implications for stress-fracture injuries in women. (United States)

    Xu, Chun; Silder, Amy; Zhang, Ju; Reifman, Jaques; Unnikrishnan, Ginu


    Load carriage is associated with musculoskeletal injuries, such as stress fractures, during military basic combat training. By investigating the influence of load carriage during exercises on the kinematics and kinetics of the body and on the biomechanical responses of bones, such as the tibia, we can quantify the role of load carriage on bone health. We conducted a cross-sectional study using an integrated musculoskeletal-finite-element model to analyze how the amount of load carriage in women affected the kinematics and kinetics of the body, as well as the tibial mechanical stress during running. We also compared the biomechanics of walking (studied previously) and running under various load-carriage conditions. We observed substantial changes in both hip kinematics and kinetics during running when subjects carried a load. Relative to those observed during running without load, the joint reaction forces at the hip increased by an average of 49.1% body weight when subjects carried a load that was 30% of their body weight (ankle, 4.8%; knee, 20.6%). These results indicate that the hip extensor muscles in women are the main power generators when running with load carriage. When comparing running with walking, finite element analysis revealed that the peak tibial stress during running (tension, 90.6 MPa; compression, 136.2 MPa) was more than three times as great as that during walking (tension, 24.1 MPa; compression, 40.3 MPa), whereas the cumulative stress within one stride did not differ substantially between running (15.2 MPa · s) and walking (13.6 MPa · s). Our findings highlight the critical role of hip extensor muscles and their potential injury in women when running with load carriage. More importantly, our results underscore the need to incorporate the cumulative effect of mechanical stress when evaluating injury risk under various exercise conditions. The results from our study help to elucidate the mechanisms of stress fracture in women.

  10. Valuation of tropical forest services and mechanisms to finance their conservation and sustainable use: A case study of Tapantí National Park, Costa Rica

    NARCIS (Netherlands)

    Bernard, F.; Groot, de R.S.; Campos, J.J.


    The Tapanti National Park in Costa Rica comprises a precious but vulnerable tropical rain forest area. The monetary values of ecosystem services that are provided by this park are estimated in order to assess the mechanisms to finance the park's conservation and sustainable use. The main ecosystem

  11. An Independent Review and Accountability Mechanism for the Sustainable Development Goals: The Possibilities of a Framework Convention on Global Health. (United States)

    Friedman, Eric A


    The Framework Convention on Global Health (FCGH), a proposed global treaty to be rooted in the right to health and aimed at health equity, could establish a nuanced, layered, and multi-faceted regime of compliance with, and accountability to, the right to health. In so doing, it would significantly strengthen accountability for the health-related Sustainable Development Goals (SDGs), which it would encompass. Legally binding, the FCGH could facilitate accountability through the courts and catalyze comprehensive domestic accountability regimes, requiring national strategies that include transparency, community and national mechanisms for accountability and participation and an enabling environment for social empowerment. A "Right to Health Capacity Fund" could ensure resources to implement these strategies. Inclusive national processes could establish targets, benchmarks, and indicators consistent with FCGH guidance, with regular reporting to a treaty body, which could also hear individual cases. State reports could be required to include plans to overcome implementation gaps, subjecting poorly complying states to penalties and targeted capacity building measures. Regional special rapporteurs could facilitate compliance through regular country visits, while also responding to serious violations. And reaching beyond government compliance, from capacity building to the courts and contractual obligations, the FCGH could establish nationally enforceable right to health obligations on the private sector.

  12. The Characterization of Mechanical Properties of a Rabbit Femur-Anterior Cruciate Ligament-Tibia Complex During Cyclic Loading (United States)

    Sekiguchi, Hidetaka; Han, Jungsoo; Ryu, Jaiyoung; Han, Changsoo

    The purpose of this study was to investigate the effect of cyclic loading, which produced the condition of ACLs during sports activities, on tensile properties of femur-ACL-tibia complexes (FATCs). Paired FATCs of 40 New Zealand white rabbits were tested on a materials testing machine. One specimen of each pair was designated as a control and loaded until failure. The contralateral specimen was loaded cyclically (1.4 Hz, 1 hr.) with 20%, 30%, 40%, or 50% of ultimate tensile strength (UTS) of the control and then loaded until failure. The UTS and mode of failure were recorded after each test. Five specimens ruptured during cyclic loading in the 50% group. In the 40% group, the mean value of UTS of cycled specimens was significantly lower than that of controls. There was no statistically significant difference in UTS values between control and cycled specimens in the 20% and 30% groups. Cycled specimens had a significantly higher incidence of substance failure than controls. Our results demonstrated that FATCs have the strength to withstand cyclic loading within normal sports activity levels. However, FACTs can be damaged by cyclic loading under strenuous sports activity levels. We speculate that cyclic loading makes the ACL substance weaker than the insertion site.

  13. Mechanical interaction of Engineered Cementitious Composite (ECC) reinforced with Fiber Reinforced Polymer (FRP) rebar in tensile loading

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe


    , particularly in post cracking phase of the concrete matrix. The experimental program carried out in this study examined composite behavior under monotonic and cyclic loading of the specimens in the elastic and inelastic deformation phases. The stiffness development of the composite during loading was evaluated...

  14. The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading (United States)

    Sivagurunathan, Rubentheran; Lau Tze Way, Saijod; Sivagurunathan, Linkesvaran; Yaakob, Mohd. Yuhazri


    The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.

  15. Thermal–mechanical stress analysis of pressurized water reactor pressure vessel with/without a preexisting crack under grid load following conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhasish, E-mail:; Soppet, William K.; Majumdar, Saurin; Natesan, Krishnamurti


    Highlights: • Use of intermittent renewable-energy source in power grid is becoming a trend. • Gird load-following can leads to variable power demand from Nuclear power plant. • Reactor components can be stressed differently under gird load-following mode. • Estimation of stress–strain state under grid load-following condition is essential. - Abstract: In this paper, we present thermal–mechanical stress analysis of a pressurized water reactor pressure vessel and its hot-leg and cold-leg nozzles. Results are presented from thermal and thermal–mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting crack in the reactor nozzle (axial crack in hot leg nozzle). From the model results it is found that the stress–strain states are significantly higher in case of presence of crack than without crack. The stress–strain state under grid load following condition are more realistic compared to the stress–strain state estimated assuming simplified transients.

  16. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism. (United States)

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng


    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

  17. Cyclic mechanical pressure-loading alters epithelial homeostasis in a three-dimensional in vitro oral mucosa model: clinical implications for denture-wearers. (United States)

    Shiomi, A; Izumi, K; Uenoyama, A; Saito, T; Saito, N; Ohnuki, H; Kato, H; Kanatani, M; Nomura, S; Egusa, H; Maeda, T


    Denture-wearing affects the quality and quantity of epithelial cells in the underlying healthy oral mucosa. The physiologic mechanisms, however, are poorly understood. This study aimed to compare histologic changes and cellular responses of an epithelial cell layer to cyclic mechanical pressure-loading mimicking denture-wearing using an organotypic culture system to develop a three-dimensional in vitro oral mucosa model (3DOMM). Primary human oral keratinocytes and fibroblasts were serially grown in a monolayer culture, and cell viability was measured under continuous cyclic mechanical pressure (50 kPa) for 7 days (cycles of 60 min on, 20 s off to degas and inject air). Upon initiation of an air-liquid interface culture for epithelial stratification, the cyclic pressure, set to the mode above mentioned, was applied to the 3DOMMs for 7 days. Paraffin-embedded 3DOMMs were examined histologically and immunohistochemically. In the monolayer culture, the pressure did not affect the viability of oral keratinocytes or fibroblasts. Few histologic changes were observed in the epithelial layer of the control and pressure-loaded 3DOMMs. Immunohistochemical examination, however, revealed a significant decrease in Ki-67 labelling and an increase in filaggrin and involucrin expression in the suprabasal layer of the pressure-loaded 3DOMMs. Pressure-loading attenuated integrin β1 expression and increased matrix metalloproteinase-9 activity. Incomplete deposition of laminin and type IV collagen beneath the basal cells was observed only in the pressure-loaded 3DOMM. Cyclic pressure-loading appeared to disrupt multiple functions of the basal cells in the 3DOMM, resulting in a predisposition towards terminal differentiation. Thus, denture-wearing could compromise oral epithelial homeostasis. © 2014 John Wiley & Sons Ltd.

  18. Optimal energy options under Clean Development Mechanism: Renewable energy projects for sustainable development and carbon emission reduction (United States)

    Gilau, Asmerom M.

    This dissertation addresses two distinct objectives; designing cost-effective renewable energy powered projects including seawater reverse osmosis (SWRO), aquaculture, and ice-making plant, and analyzing the cost-effectiveness of these projects in achieving low abatement costs and promoting sustainable developments under the Clean Development Mechanism. The results of SWRO analysis show that a wind powered system is the least expensive and a PV powered system the most expensive, with finished water costs of about 0.50 /m3 and 1.00 /m3, respectively. By international standards, these costs are competitive. The results of renewable energy powered commercial tilapia production indicate that a wind-diesel system has high potential for intensive tilapia production as well as carbon dioxide emission reductions. The study also investigates aeration failures in renewable energy powered tilapia production systems. With respect to the ice-making plant, unlike previous studies which consider nighttime operation only, we have found that a nighttime PV powered ice-making system is more expensive (1/kWh) than daytime ice-making system (0.70/kWh). Our optimal energy options analysis at project scale which includes SWRO, ice-making plant and household energy consumption for about 100 households shows that compared to diesel only energy option, PV-D, W-D, and PV-W-D hybrids are very cost-effective energy options. Moreover, energy options with high levels of renewable energy including 100% renewables have the lowest net present cost and they are already cost-effective without CDM. On the other hand, while the removal of about 87% carbon dioxide emissions could be achieved at negative cost, initial investment could increase by a factor of 40, which is one of the primary barriers hindering wider renewable energy applications in developing countries. Thus in order to increase developing countries' participation in the carbon market, CDM policy should shift from a purely market oriented

  19. Sustainable Cities

    DEFF Research Database (Denmark)

    Georg, Susse; Garza de Linde, Gabriela Lucía

    Judging from the number of communities and cities striving or claiming to be sustainable and how often eco-development is invoked as the means for urban regeneration, it appears that sustainable and eco-development have become “the leading paradigm within urban development” (Whitehead 2003......), urban design competitions are understudied mechanisms for bringing about field level changes. Drawing on actor network theory, this paper examines how urban design competitions may bring about changes within the professional field through the use of intermediaries such as a sustainable planning....../assessment tool. The context for our study is urban regeneration in one Danish city, which had been suffering from industrial decline and which is currently investing in establishing a “sustainable city”. Based on this case study we explore how the insights and inspiration evoked in working with the tool...

  20. The novel composite mechanism of ammonium molybdophosphate loaded on silica matrix and its ion exchange breakthrough curves for cesium

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Hao [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Li, Yuxiang, E-mail: [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); National Defense Key Discipline Laboratory for Nuclear Wastes and Environmental Safety, Southwest University of Science and Technology, Mianyang 621010 (China); Wu, Lang [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Ma, Xue [School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China)


    Highlights: • The granular composites were fabricated by the sequential annealing mechanism. • The method controls the porous characteristics and stable structure of materials. • The breakthrough curve of Cs{sup +} follows the Thomas model with a high removal rate. • It is a probable for SM-AMP20 to recycle Cs{sup +} using an eluent of 2–3 mol/L NH{sub 4}NO{sub 3}. - Abstract: Long-lived {sup 137}Cs (over 30 years), a byproduct of the spent fuel fission processes, comprises the majority of high-level and prolific heat-generating waste in downstream processing. This study reports a novel sequential annealing mechanism with cross-linked network of polyvinyl alcohol, fabricating the composite of ammonium molybdophosphate loaded on silica matrix (SM-AMP20, 20 wt% AMP) as an excellent granular ion exchanger for removal Cs{sup +}. When the matrix is remarkably sequential annealed, well-dispersed SM-AMP20 particles are formed by firmly anchoring themselves on controlling the porous characteristics and stable structure. The material crystallizes in the complex cubic space group Pn-3m with cell parameters of crystalline AMP formation. The breakthrough curve of Cs{sup +} by SM-AMP20 follows the Thomas model with a high removal rate of 88.23% (∼10 mg/L of Cs{sup +}) and breakthrough time as high as 26 h (flow rate Q ≈ 2.5 mL/min and bed height Z ≈ 11 cm) at neutral pH. We also report on sorbents that could efficiently remove Cs{sup +} ions from complex solutions containing different competitive cations (Na{sup +}, Al{sup 3+}, Fe{sup 3+}, and Ni{sup 2+}, respectively) in large excess. Furthermore, this study shows that there is a probability for SM-AMP20 to recycle cesium using an eluent of 2–3 mol/L NH{sub 4}NO{sub 3} solution.

  1. Modification of a commercial nanoindentation system for measurement of hysteresis cycles under mechanical load in polycrystalline ferroelectric films

    Directory of Open Access Journals (Sweden)

    Rivero, Doris


    Full Text Available A commercial hardness-tester by nanoindentation was modified to use metallic indenter tips for the measurement of hysteresis cycles of ferroelectric films under mechanical load and with high lateral resolution. A novel semi-automatic charge integrating module was developed to this aim. LabVIEW 8.6 graphical programming environment was used to control the data acquisition system (DAS, the sinusoidal high voltage generator (± 300V and the charge integrating module in the measurement of the loops. The software also provides data correction due to non-ferroelectric-switching contributions to obtain reliable remanent polarization (Pr and coercive field (Ec values. It also displays the loops both in polarization-fiel(P-E and current density-field (J-E modes. The experimental set-up was validated with measurements on dense PZT films (10μm on platinised Si substrates. Coherent cycles are obtained using the novel semi-automatic charge integrator , the classical Sawyer and Tower circuit and using an electrometer. Under low indentation load causing quasi-elastic strain, the loops do not show any artifact.

    Se ha modificado un nanoindentador comercial para el uso de puntas metálicas para la medida de ciclos de histéresis en láminas ferroeléctricas bajo carga mecánica y con alta resolución lateral. A este fin, se ha desarrollado un circuito integrador de carga semi-automático. Se ha utilizado el entorno de programación gráfica LabVIEW 8.6 para el control del sistema de adquisición de datos (SAD, un generador de alto voltaje sinusoidal (± 300V y el circuito integrador en la medida del ciclo. El software desarrollado también realiza la corrección de los ciclos por sustracción de las contribuciones no debidas a la inversión de la polarización ferroeléctrica en la obtención de valores fiables de polarización remanente (Pr y campo coercitivo (Ec. La representación del ciclo puede hacerse como

  2. A Flexible Domain-Domain Hinge Promotes an Induced-fit Dominant Mechanism for the Loading of Guide-DNA into Argonaute Protein in Thermus thermophilus

    KAUST Repository

    Zhu, Lizhe


    Argonaute proteins (Ago) are core components of the RNA Induced Silencing Complex (RISC) that load and utilize small guide nucleic acids to silence mRNAs or cleave foreign DNAs. Despite the essential role of Ago in gene regulation and defense against virus, the molecular mechanism of guide-strand loading into Ago remains unclear. We explore such a mechanism in the bacterium Thermus thermophilus Ago (TtAgo), via a computational approach combining molecular dynamics, bias-exchange metadynamics, and protein-DNA docking. We show that apo TtAgo adopts multiple closed states that are unable to accommodate guide-DNA. Conformations able to accommodate the guide are beyond the reach of thermal fluctuations from the closed states. These results suggest an induced-fit dominant mechanism for guide-strand loading in TtAgo, drastically different from the two-step mechanism for human Ago 2 (hAgo2) identified in our previous study. Such a difference between TtAgo and hAgo2 is found to mainly originate from the distinct rigidity of their L1-PAZ hinge. Further comparison among known Ago structures from various species indicates that the L1-PAZ hinge may be flexible in general for prokaryotic Agos but rigid for eukaryotic Agos. © 2016 American Chemical Society.

  3. A Precision-Positioning Method for a High-Acceleration Low-Load Mechanism Based on Optimal Spatial and Temporal Distribution of Inertial Energy

    Directory of Open Access Journals (Sweden)

    Xin Chen


    Full Text Available High-speed and precision positioning are fundamental requirements for high-acceleration low-load mechanisms in integrated circuit (IC packaging equipment. In this paper, we derive the transient nonlinear dynamicresponse equations of high-acceleration mechanisms, which reveal that stiffness, frequency, damping, and driving frequency are the primary factors. Therefore, we propose a new structural optimization and velocity-planning method for the precision positioning of a high-acceleration mechanism based on optimal spatial and temporal distribution of inertial energy. For structural optimization, we first reviewed the commonly flexible multibody dynamic optimization using equivalent static loads method (ESLM, and then we selected the modified ESLM for optimal spatial distribution of inertial energy; hence, not only the stiffness but also the inertia and frequency of the real modal shapes are considered. For velocity planning, we developed a new velocity-planning method based on nonlinear dynamic-response optimization with varying motion conditions. Our method was verified on a high-acceleration die bonder. The amplitude of residual vibration could be decreased by more than 20% via structural optimization and the positioning time could be reduced by more than 40% via asymmetric variable velocity planning. This method provides an effective theoretical support for the precision positioning of high-acceleration low-load mechanisms.

  4. Stair climbing results in more challenging patellofemoral contact mechanics and kinematics than walking at early knee flexion under physiological-like quadriceps loading. (United States)

    Goudakos, Ioannis G; König, Christian; Schöttle, Philip B; Taylor, William R; Singh, Navrag B; Roberts, Ian; Streitparth, Florian; Duda, Georg N; Heller, Markus O


    The mechanical environment during stair climbing has been associated with patellofemoral pain, but the contribution of loading to this condition is not clearly understood. It was hypothesized that the loading conditions during stair climbing induce higher patellofemoral pressures, a more lateral force distribution on the trochlea and a more lateral shift and tilt of the patella compared to walking at early knee flexion. Optical markers for kinematic measurements were attached to eight cadaveric knees, which were loaded with muscle forces at instances of walking and stair climbing cycles at 12 degrees and 30 degrees knee flexion. Contact