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Sample records for dppc small unilamellar

  1. Shape fluctuations of large unilamellar lipid vesicles observed by laser light scattering: influence of the small-scale structure.

    Science.gov (United States)

    Brocca, Paola; Cantù, Laura; Corti, Mario; Del Favero, Elena; Motta, Simona

    2004-03-16

    In the present paper, we apply the dynamic laser light scattering technique to investigate the dependence of the characteristic times of thermally induced shape fluctuation of large unilamellar vesicles (LUVs) on bilayer composition. After addressing single-component LUVs made of two common phospholipids, dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC), we investigate the changes in vesicle shape fluctuation times due to the presence of cholesterol and gangliosides (GM1), added in small amounts. The experimental results show that the addition of a second component, even in small amount, to DMPC vesicles induces a change in membrane fluctuation times. Moreover, in the case of ganglioside addition, also the disposition of GM1 within the bilayer is of importance. Quite unexpectedly, the symmetric or asymmetric disposition of GM1 has opposite effects on bilayer dynamics, the first resulting in a "hardening" and the second in a "softening" of the membrane. Those results support that the small-scale structure of the bilayer is important in determining the overall dynamics of the vesicle. They also suggest that the physiological disposition of GM1 in the outer leaflet of real cells has a significative result in mechanical terms, positively affecting the dynamics of the membrane.

  2. Structure Factor of Dimyristoylphosphatidylcholine Unilamellar Vesicles Small-Angle X-Ray Scattering Study

    CERN Document Server

    Kiselev, M A; Kisselev, A M; Lesieur, P; Aksenov, V L

    2003-01-01

    Small-angle X-ray scattering (SAXS) experiments have been performed on dimyristoylphosphatidylcholine (DMPC) unilamellar vesicles in 40 % aqueous sucrose solution. Model of separated form factors was applied for the evaluation of SAXS curves from large unilamellar vesicles. For the first time vesicle structure factor, polydispersity, average radius and membrane thickness were calculated simultaneously from the SAXS curves at T=306{\\circ}C for DMPC concentrations in the range from 15 to 75 mM (1-5 % w/w). Structure factor correction to the scattering curve was shown to be negligibly small for the lipid concentration of 15 mM (1 % w/w). It was proved to be necessary to introduce structure factor correction to the scattering curves for lipid concentrations {\\ge}30 mM (2 % w/w).

  3. Small-Angle Neutron Scattering and Spontaneous Formation of Unilamellar Vesicles: Potential Vehicles for Drug Delivery

    Science.gov (United States)

    Katsaras, John

    2004-03-01

    Unilamellar vesicles (ULVs) are single-bilayer shells with radii commonly between 10 and 100 nm, and are widely used as model membranes, drug delivery systems, microreactors and substrates for a variety of enzymes and proteins. A common method of making ULVs is the extrusion of multilamellar vesicles (MLVs) through synthetic membranes of known pore size. These extruded ULVs are invariably unstable and in due time, revert back to MLVs. Over the years there have been reports of the spontaneous formation of stable ULVs in surfactant, lipid, and lipid/detergent mixtures. These ULVs have sometimes been shown to be monodisperse and their radii were found, almost without exception, to vary with concentration. We have carried-out small-angle neutron scattering (SANS) experiments on a biomimetic system composed of the phospholipids dimyristoyl and dihexanoyl phosphorylcholine (DMPC and DHPC, respectively). Doping DMPC/DHPC multilamellar vesicles with either the negatively charged lipid dimyristoyl phosphorylglycerol (DMPG, net charge -1) or the divalent cation, calcium (Ca2+) leads to the spontaneous formation of monodisperse unilamellar vesicles whose radii are concentration independent, in contrast to previous experimental observations.

  4. Sterols associated with small unilamellar vesicles (SUVs): intrinsic mobility role for 1H NMR detection.

    Science.gov (United States)

    Mouret, Liza; Da Costa, Grégory; Bondon, Arnaud

    2014-07-01

    Small unilamellar vesicles (SUVs) of phospholipids are often used as a membrane model system for studying the interaction of molecules. When using NMR under the standard liquid-state conditions, SUV phospholipid proton spectra can be recorded, exhibiting sharp signals. This is not only because of the fast vesicular tumbling but also because of the combination of this tumbling with the individual motion of the lipids inside the bilayer. This appears evident because addition of cholesterol is responsible of broader resonances because of the slowing down of the lipid motion. On the other hand, no (1)H signal is detected for cholesterol in the bilayer. This lack of detection of the inserted molecules explains why generally SUVs are not considered as a good model for NMR studies under the standard liquid-state conditions. Here, we use two other sterols in order to demonstrate that an increase of the molecular mobility inside the bilayer could allow the detection of their proton resonances. For desmosterol and lanosterol, which show higher mobility inside the bilayer, with increasing lateral diffusion rates, (1)H sterol signals are detected in contrast to cholesterol. For the fast diffusing lanosterol, no significant improvement in detection is observed using deuterated lipids, demonstrating that homonuclear dipolar coupling is fully averaged out. Furthermore, in the case of low mobility such as for cholesterol, the use of a fast magic angle spinning probe is shown to be efficient to recover the full proton spectrum. Copyright © 2014 John Wiley & Sons, Ltd.

  5. Partitioning of organophosphorus pesticides into phosphatidylcholine small unilamellar vesicles studied by second-derivative spectrophotometry.

    Science.gov (United States)

    Takegami, Shigehiko; Kitamura, Keisuke; Ohsugi, Mayuko; Ito, Aya; Kitade, Tatsuya

    2015-06-15

    In order to quantitatively examine the lipophilicity of the widely used organophosphorus pesticides (OPs) chlorfenvinphos (CFVP), chlorpyrifos-methyl (CPFM), diazinon (DZN), fenitrothion (FNT), fenthion (FT), isofenphos (IFP), profenofos (PFF) and pyraclofos (PCF), their partition coefficient (Kp) values between phosphatidylcholine (PC) small unilamellar vesicles (SUVs) and water (liposome-water system) were determined by second-derivative spectrophotometry. The second-derivative spectra of these OPs in the presence of PC SUV showed a bathochromic shift according to the increase in PC concentration and distinct derivative isosbestic points, demonstrating the complete elimination of the residual background signal effects that were observed in the absorption spectra. The Kp values were calculated from the second-derivative intensity change induced by addition of PC SUV and obtained with a good precision of R.S.D. below 10%. The Kp values were in the order of CPFM>FT>PFF>PCF>IFP>CFVP>FNT⩾DZN and did not show a linear correlation relationship with the reported partition coefficients obtained using an n-octanol-water system (R(2)=0.530). Also, the results quantitatively clarified the effect of chemical-group substitution in OPs on their lipophilicity. Since the partition coefficient for the liposome-water system is more effective for modeling the quantitative structure-activity relationship than that for the n-octanol-water system, the obtained results are toxicologically important for estimating the accumulation of these OPs in human cell membranes.

  6. Small unilamellar liposomes as a membrane model for cell inactivation by cold atmospheric plasma treatment

    Science.gov (United States)

    Maheux, S.; Frache, G.; Thomann, J. S.; Clément, F.; Penny, C.; Belmonte, T.; Duday, D.

    2016-09-01

    Cold atmospheric plasma is thought to be a promising tool for numerous biomedical applications due to its ability to generate a large diversity of reactive species in a controlled way. In some cases, it can also generate pulsed electric fields at the zone of treatment, which can induce processes such as electroporation in cell membranes. However, the interaction of these reactive species and the pulse electric field with cells in a physiological medium is very complex, and we still need a better understanding in order to be useful for future applications. A way to reach this goal is to work with model cell membranes such as liposomes, with the simplest physiological liquid and in a controlled atmosphere in order to limit the number of parallel reactions and processes. In this paper, where this approach has been chosen, 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) small unilamellar vesicles (SUV) have been synthesized in a phosphate buffered aqueous solution, and this solution has been treated by a nanosecond pulsed plasma jet under a pure nitrogen atmosphere. It is only the composition of the plasma gas that has been changed in order to generate different cocktails of reactive species. After the quantification of the main plasma reactive species in the phosphate buffered saline (PBS) solution, structural, surface charge state, and chemical modifications generated on the plasma treated liposomes, due to the interaction with the plasma reactive species, have been carefully characterized. These results allow us to further understand the effect of plasma reactive species on model cell membranes in physiological liquids. The permeation through the liposomal membrane and the reaction of plasma reactive species with molecules encapsulated inside the liposomes have also been evaluated. New processes of degradation are finally presented and discussed, which come from the specific conditions of plasma treatment under the pure nitrogen atmosphere.

  7. DMSO-Induced Dehydration of DPPC Membranes Studied by X-ray Diffraction, Small-Angle Neutron Scattering, and Calorimetry

    CERN Document Server

    Kiselev, M A; Kisselev, A M; Grabielle-Madelmond, C; Ollivon, M

    1999-01-01

    The influence of dimethyl sulfoxide (DMSO) on membrane thickness, multilamellar repeat distance, and phase transitions of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) was investigated by X-ray diffraction and small-angle neutron scattering (SANS). The differential scanning calorimetry (DSC) study of water freezing and ice melting was performed in the ternary DPPC /DMSO /water and binary DMSO /water systems. The methods applied demonstrated the differences in membrane structure in three sub-regions of the DMSO mole fraction (X_dmso): from 0.0 to 0.3 for the first, from 0.3 to 0.8 for the second, and from 0.9 to 1.0 for the third sub-region. The thickness of the intermembrane solvent at T =20C decreases from 14.4 +/- 1.8 A at X_dmso =0.0 to 7.8 +/- 1.8 A at X_dmso =0.1. The data were used to determine the number of free water molecules in the intermembrane space in the presence of DMSO. The results for 0.0 < X_dmso < 0.3 were explained in the framework of DMSO-induced dehydration of the interme...

  8. Investigation of the structure of unilamellar dimyristoylphosphatidylcholine vesicles in aqueous sucrose solutions by small-angle neutron and X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, M. A., E-mail: elena@jinr.ru; Zemlyanaya, E. V.; Zhabitskaya, E. I.; Aksenov, V. L. [Joint Institute for Nuclear Research (Russian Federation)

    2015-01-15

    The structure of a polydispersed population of unilamellar dimyristoylphosphatidylcholine (DMPC) vesicles in sucrose solutions has been investigated by small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). Calculations within the model of separated form factors (SFF) show that the structure of the vesicle system depends strongly on the sucrose concentration.

  9. Measurement of the glucose permeation rate across phospholipid bilayers using small unilamellar vesicles. Effect of membrane composition and temperature.

    Science.gov (United States)

    Bresseleers, G J; Goderis, H L; Tobback, P P

    1984-05-30

    Small unilamellar vesicles were used to measure the permeability of saturated phosphatidylcholine bilayers to glucose. The presented method circumvents most of the common restriction of classical permeability experiments. Increasing the fatty acid chain length of the lipids reduced the permeation rate significantly. Raising the temperature above that of the lipid phase transition drastically increased membrane permeability. Arrhenius plots demonstrated the activation energy to be independent of membrane composition and the phase-state of the lipids. The permeation process is discussed in terms of a constant energy to disrupt all hydrogen bonds between permeant and aqueous solvent prior to penetrating the membrane. The magnitude of the permeability coefficient is partly determined by a unfavourable change in entropy of activation on crossing the water/lipid interface. All results indicate that the penetration of the dehydrated permeant into the hydrophobic barrier is the rate-limiting step in the permeation of glucose.

  10. Growth Kinetics of Lipid-Based Nanodiscs to Unilamellar Vesicles: A Time-Resolved Small Angle Neutron Scattering (SANS) Study

    Energy Technology Data Exchange (ETDEWEB)

    Mahabir, Suanne [University of Western Ontario, The; Small, Darcy [University of Western Ontario, The; Li, Ming [University of Connecticut, Storrs; Wan, Wankei [University of Western Ontario, The; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Littrell, Ken [ORNL; Katsaras, John [ORNL; Nieh, Mu-Ping [University of Connecticut, Storrs

    2013-01-01

    Mixtures of dimyristoyl-phosphatidylcholine (DMPC), dimyristoyl-phosphatidylglycerol (DMPG) and dihexanoylphosphatidylcholine (DHPC) in aqueous solutions spontaneously form monodisperse, bilayered nanodiscs (also known as bicelles ) at or below the melting transition temperature of DMPC (TM ~23 C). In dilute systems above the main transition temperature TM of DMPC, bicelles coalesce (increasing their diameter) and eventually self-fold into unilamellar vesicles (ULVs). Time resolved small angle neutron scattering was used to study the growth kinetics of nanodiscs below and equal to TM over a period of hours as a function of temperature at two lipid concentrations in presence or absence of NaCl salt. Bicelles seem to undergo a sudden initial growth phase with increased temperature, which is then followed by a slower reaction-limited growth phase that depends on ionic strength, lipid concentration and temperature. The bicelle interaction energy was derived from the colloidal theory of Derjaguin and Landau, and Verwey and Overbeek (DLVO). While the calculated total energy between discs is attractive and proportional to their growth rate, a more detailed mechanism is proposed to describe the mechanism of disc coalescence. After annealing at low temperature (low-T), samples were heated to 50 C in order to promote the formation of ULVs. Although the low-T annealing of samples has only a marginal effect on the mean size of end-state ULVs, it does affect their polydispersity, which increases with increased T, presumably driven by the entropy of the system.

  11. Effect of sodium deoxycholate and sodium cholate on DPPC vesicles: A fluorescence anisotropy study with diphenylhexatriene

    Indian Academy of Sciences (India)

    Usharani Subuddhi; Ashok K Mishra

    2007-03-01

    Effects of two bile salts, namely sodium deoxycholate (NaDC) and sodium cholate (NaC), on DPPC small unilamellar vesicles have been investigated using the steady-state fluorescence anisotropy () of diphenylhexatriene (DPH) as a tool. It was found that the variation of is sensitive enough to monitor different stages of interaction of bile salts with DPPC vesicles. NaDC induced significant changes in the membrane well below its CMC (6 mM). Even at 4 mM, which is still lower than the CMC, the phospholipids were completely solubilised by the NaDC micelles. The effect of NaC on DPPC vesicles, however, was much less significant, especially in the sub-micellar concentration regime. Being more hydrophilic NaC does not interact with the membrane efficiently. Complete solubilisation of phospholipids took place only when the concentration of NaC was above its CMC (16 mM). The experiments also showed that the bile salt-induced changes of vesicle structure were strongly dependent on the concentration of the bile salt and not on the molar ratio of lipid and bile salt.

  12. Partitioning of anti-inflammatory steroid drugs into phosphatidylcholine and phosphatidylcholine-cholesterol small unilamellar vesicles as studied by second-derivative spectrophotometry.

    Science.gov (United States)

    Takegami, Shigehiko; Kitamura, Keisuke; Funakoshi, Takako; Kitade, Tatsuya

    2008-05-01

    The partition coefficients (Kps) of six anti-inflammatory steroid drugs, dexamethasone (DMS), betamethasone (BMS), triamcinolone acetonide (TCLA), fluocinolone acetonide (FCLA), betamethasone 17,21-dipropionate (BMSDP), and clobetasole propionate (CBSP), for phosphatidylcholine (PC), and PC-cholesterol small unilamellar vesicles (SUVs) were determined by a second-derivative spectrophotometric method. The Kp values were obtained with a relative standard deviation of below 10% and the following order was observed: BMS< or =DMS

  13. Growth kinetics of lipid-based nanodiscs to unilamellar vesicles-a time-resolved small angle neutron scattering (SANS) study.

    Science.gov (United States)

    Mahabir, Suanne; Small, Darcy; Li, Ming; Wan, Wankei; Kučerka, Norbert; Littrell, Kenneth; Katsaras, John; Nieh, Mu-Ping

    2013-03-01

    Mixtures of dimyristoyl-phosphatidylcholine (DMPC), dimyristoyl-phosphatidylglycerol (DMPG) and dihexanoyl-phosphatidylcholine (DHPC) in aqueous solutions spontaneously form monodisperse, bilayered nanodiscs (also known as "bicelles") at or below the melting transition temperature of DMPC (T(M) ~23°C). In dilute systems above the main transition temperature T(M) of DMPC, bicelles coalesce (increasing their diameter) and eventually self-fold into unilamellar vesicles (ULVs). Time-resolved small angle neutron scattering was used to study the growth kinetics of nanodiscs below and equal to T(M) over a period of hours as a function of temperature at two lipid concentrations in presence or absence of NaCl salt. Bicelles seem to undergo a sudden initial growth phase with increased temperature, which is then followed by a slower reaction-limited growth phase that depends on ionic strength, lipid concentration and temperature. The bicelle interaction energy was derived from the colloidal theory of Derjaguin and Landau, and Verwey and Overbeek (DLVO). While the calculated total energy between discs is attractive and proportional to their growth rate, a more detailed mechanism is proposed to describe the mechanism of disc coalescence. After annealing at low temperature (low-T), samples were heated to 50°C in order to promote the formation of ULVs. Although the low-T annealing of samples has only a marginal effect on the mean size of end-state ULVs, it does affect their polydispersity, which increases with increased T, presumably driven by the entropy of the system.

  14. Effect of Melatonin and Cholesterol on the Structure of DOPC and DPPC Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Drolle, E [University of Waterloo, Canada; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Hoopes, M I [University of Waterloo, Canada; Choi, Y [University of Waterloo, Canada; Katsaras, John [ORNL; Karttunen, M [University of Waterloo, Canada; Leonenko, Z [University of Waterloo, Canada

    2013-01-01

    The cell membrane plays an important role in the molecular mechanism of amyloid toxicity associated with Alzheimer's disease. The membrane's chemical composition and the incorporation of small molecules, such as melatonin and cholesterol, can alter its structure and physical properties, thereby affecting its interaction with amyloid peptides. Both melatonin and cholesterol have been recently linked to amyloid toxicity. Melatonin has been shown to have a protective role against amyloid toxicity. However, the underlying molecular mechanism of this protection is still not well understood, and cholesterol's role remains controversial. We used small-angle neutron diffraction (SAND) from oriented lipid multi-layers, small-angle neutron scattering (SANS) from unilamellar vesicles experiments andMolecular Dynamics (MD) simulations to elucidate non-specific interactions of melatonin and cholesterol with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) model membranes. We conclude that melatonin decreases the thickness of both model membranes by disordering the lipid hydrocarbon chains, thus increasing membrane fluidity. This result is in stark contrast to the much accepted ordering effect induced by cholesterol, which causes membranes to thicken.

  15. Mixed DPPC/DPPG monolayers at very high film compression.

    Science.gov (United States)

    Saad, Sameh M I; Policova, Zdenka; Acosta, Edgar J; Hair, Michael L; Neumann, A Wilhelm

    2009-09-15

    A drop shape technique using a constrained sessile drop constellation (ADSA-CSD) has been introduced as a superior technique for studying spread films specially at high collapse pressures [Saad et al. Langmuir 2008, 24, 10843-10850]. It has been shown that ADSA-CSD has certain advantages including the need only for small quantities of liquid and insoluble surfactants, the ability to measure very low surface tension values, easier deposition procedure, and leak-proof design. Here, this technique was applied to investigate mixed DPPC/DPPG monolayers to characterize the role of such molecules in maintaining stable film properties and surface activity of lung surfactant preparations. Results of compression isotherms were obtained for different DPPC/DPPG mixture ratios: 90/10, 80/20, 70/30, 60/40, and 50/50 in addition to pure DPPC and pure DPPG at room temperature of 24 degrees C. The ultimate collapse pressure of DPPC/DPPG mixtures was found to be 70.5 mJ/m2 (similar to pure DPPC) for the cases of low DPPG content (up to 20%). Increasing the DPPG content in the mixture (up to 40%) caused a slight decrease in the ultimate collapse pressure. However, further increase of DPPG in the mixture (50% or more) caused a sharp decrease in the ultimate collapse pressure to a value of 59.9 mJ/m2 (similar to pure DPPG). The change in film elasticity was also tracked for the range of mixture ratios studied. The physical reasons for such changes and the interaction between DPPC and DPPG molecules are discussed. The results also show a change in the film hysteresis upon successive compression and expansion cycles for different mixture ratios.

  16. Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

    Science.gov (United States)

    Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

    2006-03-01

    The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

  17. Hierarchical unilamellar vesicles of controlled compositional heterogeneity.

    Directory of Open Access Journals (Sweden)

    Maik Hadorn

    Full Text Available Eukaryotic life contains hierarchical vesicular architectures (i.e. organelles that are crucial for material production and trafficking, information storage and access, as well as energy production. In order to perform specific tasks, these compartments differ among each other in their membrane composition and their internal cargo and also differ from the cell membrane and the cytosol. Man-made structures that reproduce this nested architecture not only offer a deeper understanding of the functionalities and evolution of organelle-bearing eukaryotic life but also allow the engineering of novel biomimetic technologies. Here, we show the newly developed vesicle-in-water-in-oil emulsion transfer preparation technique to result in giant unilamellar vesicles internally compartmentalized by unilamellar vesicles of different membrane composition and internal cargo, i.e. hierarchical unilamellar vesicles of controlled compositional heterogeneity. The compartmentalized giant unilamellar vesicles were subsequently isolated by a separation step exploiting the heterogeneity of the membrane composition and the encapsulated cargo. Due to the controlled, efficient, and technically straightforward character of the new preparation technique, this study allows the hierarchical fabrication of compartmentalized giant unilamellar vesicles of controlled compositional heterogeneity and will ease the development of eukaryotic cell mimics that resemble their natural templates as well as the fabrication of novel multi-agent drug delivery systems for combination therapies and complex artificial microreactors.

  18. Effects of cholesterol on phospholipid membranes: inhibition of the interdigitated gel phase of F-DPPC and F-DPPC/DPPC.

    Science.gov (United States)

    Smith, Eric A; Wang, Weidong; Dea, Phoebe K

    2012-02-01

    Unlike the parent phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the monofluorinated analog, 1-palmitoyl-2-(16-fluoropalmitoyl)sn-glycero-3-phosphocholine (F-DPPC), spontaneously forms an interdigitated gel phase (L(β)I) below the main transition temperature (T(m)). We have examined the effects of introducing cholesterol to F-DPPC and 1:1 F-DPPC/DPPC membranes using a combination of DSC, optical density, fluorescence intensity and polarization, (31)P NMR, and X-ray diffraction techniques. Cholesterol increases the fluidity of the gel phase, broadens the main transition, and decreases the main transition enthalpy. However, these results also reveal that there is an unusually large degree of phase coexistence between the L(β)I and non-interdigitated gel phases when cholesterol is added. Cholesterol encourages this phase segregation by partitioning into the thicker non-interdigitated domains. At higher cholesterol concentrations, the majority or all of the L(β)I phase of F-DPPC and 1:1 F-DPPC/DPPC is eliminated and is replaced by a non-interdigitated liquid-ordered (l(o)) phase with properties similar to DPPC/cholesterol. Consequently, cholesterol mitigates the influence the CF moiety has on the thermodynamic phase behavior of F-DPPC. Our findings demonstrate that there are multiple characteristics of cholesterol-rich membranes that disfavor interdigitation.

  19. Lipid domains in giant unilamellar vesicles and their correspondence with equilibrium thermodynamic phases: A quantitative fluorescence microscopy imaging approach

    DEFF Research Database (Denmark)

    Fidorra, Matthias; Garcia, Alejandra; Ipsen, John Hjort

    2009-01-01

    and reconstruction of 3D domain morphology using active surface models. This method permits the reconstruction of the spherical surface of GUVs and determination of the area fractions of coexisting lipid domains at the level of single vesicles. Obtaining area fractions enables the scrutiny of the lever rule along...... lipid phase diagram's tie lines and to test whether or not the coexistence of lipid domains in GUVs correspond to equilibrium thermodynamic phases. The analysis was applied to DLPC/DPPC GUVs displaying coexistence of lipid domains. Our results confirm the lever rule, demonstrating that the observed......We report a novel analytical procedure to measure the surface areas of coexisting lipid domains in giant unilamellar vesicles (GUVs) based on image processing of 3D fluorescence microscopy data. The procedure involves the segmentation of lipid domains from fluorescent image stacks...

  20. Phase coexistence in films composed of DLPC and DPPC: a comparison between different model membrane systems.

    Science.gov (United States)

    Mangiarotti, Agustín; Caruso, Benjamín; Wilke, Natalia

    2014-07-01

    For the biophysical study of membranes, a variety of model systems have been used to measure the different parameters and to extract general principles concerning processes that may occur in cellular membranes. However, there are very few reports in which the results obtained with the different models have been compared. In this investigation, we quantitatively compared the phase coexistence in Langmuir monolayers, freestanding bilayers and supported films composed of a lipid mixture of DLPC and DPPC. Two-phase segregation was observed in most of the systems for a wide range of lipid proportions using fluorescence microscopy. The lipid composition of the coexisting phases was determined and the distribution coefficient of the fluorescent probe in each phase was quantified, in order to explore their thermodynamic properties. The comparison between systems was carried out at 30mN/m, since it is accepted that at this or higher lateral pressures, the mean molecular area in bilayers is equivalent to that observed in monolayers. Our study showed that while Langmuir monolayers and giant unilamellar vesicles had a similar phase behavior, supported films showed a different composition of the phases with the distribution coefficient of the fluorescent probe being close to unity. Our results suggest that, in supported membranes, the presence of the rigid substrate may have led to a stiffening of the liquid-expanded phase due to a loss in the degrees of freedom of the lipids as a consequence of the proximity of the solid material.

  1. Penetration and growth of DPPC/DHPC bicelles inside the stratum corneum of the skin.

    Science.gov (United States)

    Barbosa-Barros, L; de la Maza, A; Estelrich, J; Linares, A M; Feliz, M; Walther, P; Pons, R; López, O

    2008-06-03

    The effect of dipalmitoyl phosphatidylcholine (DPPC)/dihexanoyl phosphatidylcholine (DHPC) bicelles on the microstructure of pig stratum corneum (SC) in vitro was evaluated. The physicochemical characterization of these nanoaggregates revealed small disks with diameters around 15 nm and a thickness of 5.4 nm. Upon dilution, the bicelles grow and transform into vesicles. Cryogenic scanning electron microscopy (cryo-SEM) images of the SC pieces treated with this system showed vesicles of about 200 nm and lamellar-like structures in the intercellular lipid areas. These vesicles probably resulted from the growth and molecular rearrangement of the DPPC/DHPC bicelles after penetrating the SC. The presence of lamellar-like structures is ascribed to the interaction of the lipids from bicelles with the SC lipids. The bicellar system used is suitable to penetrate the skin SC and to reinforce the intercellular lipid areas, constituting a promising tool for skin applications.

  2. Refined contour analysis of giant unilamellar vesicles

    Science.gov (United States)

    Pécréaux, J.; Döbereiner, H.-G.; Prost, J.; Joanny, J.-F.; Bassereau, P.

    2004-03-01

    The fluctuation spectrum of giant unilamellar vesicles is measured using a high-resolution contour detection technique. An analysis at higher q vectors than previously achievable is now possible due to technical improvements of the experimental setup and of the detection algorithm. The global fluctuation spectrum is directly fitted to deduce the membrane tension and the bending modulus of lipid membranes. Moreover, we show that the planar analysis of fluctuations is valid for spherical objects, even at low wave vectors. Corrections due to the integration time of the video camera and to the section of a 3D object by the observation plane are introduced. A precise calculation of the error bars has been done in order to provide reliable error estimate. Eventually, using this technique, we have measured bending moduli for EPC, SOPC and \\chem{SOPC:CHOL} membranes confirming previously published values. An interesting application of this technique can be the measurement of the fluctuation spectra for non-equilibrium membranes, such as “active membranes”.

  3. [Study on the Effects of Ginsenoside Rb1 on DPPC Bilayers by Using Thermo-Raman Spectrum and DSC].

    Science.gov (United States)

    Hui, Ge; Liu, Wei; Zhang, Jing-zhou; Zhou, Tie-li; Wang, Si-ming; Zhao, Yu; Zhao, Bing

    2015-08-01

    concentration of ginsenoside Rb1, the pre-transition temperature of DPPC bilayers dropped immediately with small amount of the Rb1 drug when the containtion was only 5 mol% and the whole system has been destructed at the same time, the main phase transition peak showed as a new little shoulder seam, however, both pre- and main transition peak disappeared completely until the drug concentration increased to 20 mol%, the phase transition temperature of DPPC has been reduced significantly, and the fluidity of bilayers has been increased. Both experiments indicated that the strong effects of ginsenoside Rb1 on DPPC.

  4. Interaction of dipalmitoyl phosphatidylcholine (DPPC) liposomes and insulin

    Science.gov (United States)

    Mady, Mohsen M.; Elshemey, Wael M.

    2011-06-01

    Insulin, a peptide that has been used for decades in the treatment of diabetes, has well-defined properties and delivery requirements. Liposomes, which are lipid bilayer vesicles, have gained increasing attention as drug carriers which reduce the toxicity and increase the pharmacological activity of various drugs. The molecular interaction between (uncharged lipid) dipalmitoyl phosphatidylcholine (DPPC) liposomes and insulin has been characterized by using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. The characteristic protein absorption band peaks, Amide I (at about 1660 cm-1) and Amide II band (at about 1546 cm-1) are potentially reduced in the liposome insulin complex. Wide-angle x-ray scattering measurements showed that the association of insulin with DPPC lipid of liposomes still maintains the characteristic DPPC diffraction peaks with almost no change in relative intensities or change in peak positions. The absence of any shift in protein peak positions after insulin being associated with DPPC liposomes indicates that insulin is successfully forming complex with DPPC liposomes with possibly no pronounced alterations in the structure of insulin molecule.

  5. Resveratrol induces chain interdigitation in DPPC cell membrane model systems.

    Science.gov (United States)

    Longo, Elena; Ciuchi, Federica; Guzzi, Rita; Rizzuti, Bruno; Bartucci, Rosa

    2016-12-01

    Resveratrol is a natural polyphenol found in various plants with potential therapeutic activity as anti-oxidant, anti-inflammatory, cardioprotective and anti-tumoral. Lipid membranes are among cellular components that are targets of its action. In this work ESR of chain labeled lipids, calorimetry, X-ray diffraction and molecular docking are used to study the interaction of resveratrol with membrane model systems of dipalmitoylphosphatidylcholine (DPPC) as a function of resveratrol concentration (0-30 mol% of the lipid) and temperature (10-50°C). Resveratrol incorporated in DPPC bilayers induces considerable motional restriction at the lipid tail termini, removing the gradient of increasing mobility along the chain found in DPPC bilayers in the gel phase. In contrast, it leaves unperturbed the DPPC chain flexibility profile in the liquid-crystalline phase. At low concentration, resveratrol progressively reduces the pre-transition temperature and eliminates the pre-transition for content ≥5mol%. A reduced cooperativity and a downshift of the main transition temperature are observed, especially at high content. The typical diffraction pattern of DPPC multibilayers in the Lβ' phase is converted to a lamellar pattern with reduced d-spacing of untilted lipid chain in a hexagonal packing at 30 mol% of resveratrol. Molecular docking indicates that the energetically favoured anchoring site is the polar headgroup region, where resveratrol acts as a spacer. The overall results are consistent with the formation in DPPC of an interdigitated Lβi gel phase induced by 30 mol% resveratrol. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Comparison of DPPC and DPPG environments in pulmonary surfactant models.

    Science.gov (United States)

    Morrow, Michael R; Temple, Sara; Stewart, June; Keough, Kevin M W

    2007-07-01

    Deuterium nuclear magnetic resonance was used to monitor lipid acyl-chain orientational order in suspensions of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) containing Ca(2+) and the lung surfactant proteins SP-A and SP-B separately and together. To distinguish between protein-lipid interactions involving the PC and PG lipid headgroups and to examine whether such interactions might influence spatial distribution of lipids within the bilayer, acyl chains on either the DPPC or the DPPG component of the mixture were deuterated. The lipid components of the resulting mixtures were thus either DPPC-d(62)/DPPG (7:3) or DPPC/DPPG-d(62) (7:3), respectively. SP-A had little effect on DPPC-d(62) chain order but did narrow the temperature range over which DPPG-d(62) ordered at the liquid-crystal-to-gel transition. No segregation of lipid components was seen for temperatures above or below the transition. Near the transition, though, there was evidence that SP-A promoted preferential depletion of DPPG from liquid crystalline domains in the temperature range over which gel and liquid crystal domains coexist. SP-B lowered average chain order of both lipids both above and below the main transition. The perturbations of chain order by SP-A and SP-B together were smaller than by SP-B alone. This reduction in perturbation of the lipids by the additional presence of SP-A likely indicated a strong interaction between SP-A and SP-B. The competitive lipid-lipid, lipid-protein, and protein-protein interactions suggested by these observations presumably facilitate the reorganization of surfactant material inherent in the transformation from lamellar bodies to a functional surfactant layer.

  7. The aminosterol antibiotic squalamine permeabilizes large unilamellar phospholipid vesicles.

    Science.gov (United States)

    Selinsky, B S; Zhou, Z; Fojtik, K G; Jones, S R; Dollahon, N R; Shinnar, A E

    1998-03-13

    The ability of the shark antimicrobial aminosterol squalamine to induce the leakage of polar fluorescent dyes from large unilamellar phospholipid vesicles (LUVs) has been measured. Micromolar squalamine causes leakage of carboxyfluorescein (CF) from vesicles prepared from the anionic phospholipids phosphatidylglycerol (PG), phosphatidylserine (PS), and cardiolipin. Binding analyses based on the leakage data show that squalamine has its highest affinity to phosphatidylglycerol membranes, followed by phosphatidylserine and cardiolipin membranes. Squalamine will also induce the leakage of CF from phosphatidylcholine (PC) LUVs at low phospholipid concentrations. At high phospholipid concentrations, the leakage of CF from PC LUVs deviates from a simple dose-response relationship, and it appears that some of the squalamine can no longer cause leakage. Fluorescent dye leakage generated by squalamine is graded, suggesting the formation of a discrete membrane pore rather than a generalized disruption of vesicular membranes. By using fluorescently labeled dextrans of different molecular weight, material with molecular weight squalamine, but material with molecular weight >/=10,000 is retained. Negative stain electron microscopy of squalamine-treated LUVs shows that squalamine decreases the average vesicular size in a concentration-dependent manner. Squalamine decreases the size of vesicles containing anionic phospholipid at a lower squalamine/lipid molar ratio than pure PC LUVs. In a centrifugation assay, squalamine solubilizes phospholipid, but only at significantly higher squalamine/phospholipid ratios than required for either dye leakage or vesicle size reduction. Squalamine solubilizes PC at lower squalamine/phospholipid ratios than PG. We suggest that squalamine complexes with phospholipid to form a discrete structure within the bilayers of LUVs, resulting in the transient leakage of small encapsulated molecules. At higher squalamine/phospholipid ratios, these

  8. Lipid lateral organization on giant unilamellar vesicles containing lipopolysaccharides

    DEFF Research Database (Denmark)

    Kubiak, Jakub; Brewer, Jonathan R.; Hansen, Søren

    2011-01-01

    We developed a new (to our knowledge) protocol to generate giant unilamellar vesicles (GUVs) composed of mixtures of single lipopolysaccharide (LPS) species and Escherichia coli polar lipid extracts. Four different LPSs that differed in the size of the polar headgroup (i.e., LPS smooth > LPS...

  9. Lipid domains in giant unilamellar vesicles and their correspondence with equilibrium thermodynamic phases: a quantitative fluorescence microscopy imaging approach.

    Science.gov (United States)

    Fidorra, M; Garcia, A; Ipsen, J H; Härtel, S; Bagatolli, L A

    2009-10-01

    We report a novel analytical procedure to measure the surface areas of coexisting lipid domains in giant unilamellar vesicles (GUVs) based on image processing of 3D fluorescence microscopy data. The procedure involves the segmentation of lipid domains from fluorescent image stacks and reconstruction of 3D domain morphology using active surface models. This method permits the reconstruction of the spherical surface of GUVs and determination of the area fractions of coexisting lipid domains at the level of single vesicles. Obtaining area fractions enables the scrutiny of the lever rule along lipid phase diagram's tie lines and to test whether or not the coexistence of lipid domains in GUVs correspond to equilibrium thermodynamic phases. The analysis was applied to DLPC/DPPC GUVs displaying coexistence of lipid domains. Our results confirm the lever rule, demonstrating that the observed membrane domains correspond to equilibrium thermodynamic phases (i.e., solid ordered and liquid disordered phases). In addition, the fact that the lever rule is validated from 11 to 14 randomly selected GUVs per molar fraction indicates homogeneity in the lipid composition among the explored GUV populations. In conclusion, our study shows that GUVs are reliable model systems to perform equilibrium thermodynamic studies of membranes.

  10. Phosphate mineral formation on the supported dipalmitoylphosphatidylcholine (DPPC) layers.

    Science.gov (United States)

    Szcześ, Aleksandra

    2014-07-01

    Dipalmitoylphosphatidylcholine (DPPC) mono- and bilayers supported on mica surface were soaked for two weeks in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. Two solutions were investigated: with and without Tris. The experiment was conducted at 20°C and at a physiological temperature equal to 37°C. Raman spectroscopy was used for the characterization of the precipitated phosphate minerals. These studies may provide information about the physiological mineralization of cell membranes that are mainly composed of phospholipids. Findings from these experiments suggest that the DPPC bilayers enhance the formation of less soluble phosphate forms especially at a temperature of 37°C. In the solution without Tris temperature increase gives more mineral deposits. It is probably the hydrogen interactions between phosphate groups of the phospholipid and hydroxyl groups from Tris that lower exposure of the phosphate group to interact with calcium ions.

  11. Interfacial shear rheology of DPPC under physiologically relevant conditions.

    Science.gov (United States)

    Hermans, Eline; Vermant, Jan

    2014-01-07

    Lipids, and phosphatidylcholines in particular, are major components in cell membranes and in human lung surfactant. Their ability to encapsulate or form stable layers suggests a significant role of the interfacial rheological properties. In the present work we focus on the surface rheological properties of dipalmitoylphosphatidylcholine (DPPC). Literature results are confusing and even contradictory; viscosity values have been reported differ by several orders of magnitude. Moreover, even both purely viscous and gel-like behaviours have been described. Assessing the literature critically, a limited experimental window has been explored correctly, which however does not yet include conditions relevant for the physiological state of DPPC in vivo. A complete temperature and surface pressure analysis of the interfacial shear rheology of DPPC is performed, showing that the monolayer behaves as a viscoelastic liquid with a domain structure. At low frequencies and for a thermally structured monolayer, the interaction of the molecules within the domains can be probed. The low frequency limit of the complex viscosity is measured over a wide range of temperatures and surface pressures. The effects of temperature and surface pressure on the low frequency viscosity can be analysed in terms of the effects of free molecular area. However, at higher frequencies or following a preshear at high shear rates, elasticity becomes important; most probably elasticity due to defects at the edge of the domains in the layer is probed. Preshearing refines the structure and induces more defects. As a result, disagreeing interfacial rheology results in various publications might be due to different pre-treatments of the interface. The obtained dataset and scaling laws enable us to describe the surface viscosity, and its dependence under physiological conditions of DPPC. The implications on functioning of lung surfactants and lung surfactant replacements will be discussed.

  12. Effect of chitosan coating on the characteristics of DPPC liposomes

    Directory of Open Access Journals (Sweden)

    Mohsen M. Mady

    2010-07-01

    Full Text Available Because it is both biocompatible and biodegradable, chitosan has been used to provide a protective capsule in new drug formulations. The present work reports on investigations into some of the physicochemical properties of chitosan-coated liposomes, including drug release rate, transmission electron microscopy (TEM, zeta potential and turbidity measurement. It was found that chitosan increases liposome stability during drug release. The coating of DPPC liposomes with a chitosan layer was confirmed by electron microscopy and the zeta potential of liposomes. The coating of liposomes by chitosan resulted in a marginal increase in the size of the liposomes, adding a layer of (92 ± 27.1 nm. The liposomal zeta potential was found to be increasingly positive as chitosan concentration increased from 0.1% to 0.3% (w/v, before stabilising at a relatively constant value. Turbidity studies revealed that the coating of DPPC liposomes with chitosan did not significantly modify the main phase transition temperature of DPPC at examined chitosan concentrations. The appropriate combination of liposomal and chitosan characteristics may produce liposomes with specific, prolonged and controlled release.

  13. Formation of Kinetically Trapped Nanoscopic Unilamellar Vesicles from Metastable Nanodiscs

    Energy Technology Data Exchange (ETDEWEB)

    Nieh, Mu-Ping [University of Connecticut, Storrs; Dolinar, Paul [University of Ottawa, Canada; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Kline, Steven R. [National Institute of Standards and Technology (NIST), Gaithersburg, MD; Debeer-Schmitt, Lisa M [ORNL; Littrell, Ken [ORNL; Katsaras, John [ORNL

    2011-01-01

    Zwitterionic long-chain lipids (e.g., dimyristoyl phosphatidylcholine, DMPC) spontaneously form onion-like, thermodynamically stable structures in aqueous solutions (commonly known as multilamellar vesicles, or MLVs). It has also been reported that the addition of zwitterionic short-chain (i.e., dihexanoyl phosphatidylcholine, DHPC) and charged long-chain (i.e., dimyristoyl phosphatidylglycerol, DMPG) lipids to zwitterionic long-chain lipid solutions results in the formation of unilamellar vesicles (ULVs). Here, we report a kinetic study on lipid mixtures composed of DMPC, DHPC, and DMPG. Two membrane charge densities (i.e., [DMPG]/[DMPC] = 0.01 and 0.001) and two solution salinities (i.e., [NaCl] = 0 and 0.2 M) are investigated. Upon dilution of the high-concentration samples at 50 C, thermodynamically stable MLVs are formed, in the case of both weakly charged and high salinity solution mixtures, implying that the electrostatic interactions between bilayers are insufficient to cause MLVs to unbind. Importantly, in the case of these samples small angle neutron scattering (SANS) data show that, initially, nanodiscs (also known as bicelles) or bilayered ribbons form at low temperatures (i.e., 10 C), but transform into uniform size, nanoscopic ULVs after incubation at 10 C for 20 h, indicating that the nanodisc is a metastable structure. The instability of nanodiscs may be attributed to low membrane rigidity due to a reduced charge density and high salinity. Moreover, the uniform-sized ULVs persist even after being heated to 50 C, where thermodynamically stable MLVs are observed. This result clearly demonstrates that these ULVs are kinetically trapped, and that the mechanical properties (e.g., bending rigidity) of 10 C nanodiscs favor the formation of nanoscopic ULVs over that of MLVs. From a practical point of view, this method of forming uniform-sized ULVs may lend itself to their mass production, thus making them economically feasible for medical applications that

  14. Structural transition in aqueous lipid/bile salt [DPPC/NaDC] supramolecular aggregates: SANS and DLS study

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, M.A. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Janich, M.; Hildebrand, A. [Martin-Luther-University, Halle (Saale) (Germany); Strunz, P. [Berlin Neutron Scattering Center, HZB, Berlin (Germany); Neubert, R.H.H. [Martin-Luther-University, Halle (Saale) (Germany); Lombardo, D., E-mail: lombardo@me.cnr.it [CNR–IPCF, Istituto per i Processi Chimico Fisici – (Sez. Messina), I-98158, Messina (Italy)

    2013-10-16

    Highlights: • Self-assembly in model DPPC lipids and NaDC bile salt by SANS and DLS experiments. • Bile salt creates structural interference against cohesive tendency of DPPC bilayers. • NaDC steric interactions cause transition toward different supramolecular structures. - Abstract: Small angle neutron scattering (SANS) and dynamic light scattering (DLS) were used to study different aggregation states in sodium deoxycholate (NaDC)-phosphatidylcholine systems at T = 60 °C. Size and shape of the aggregates investigated as a function of the NaDC bile salt concentration (at the constant DPPC concentration of 6 mM) indicate a strong dependence of the size and morphology of the generated aggregates on the relative amount of NaDC bile salt. More specifically large occupied area of the bile salt induces a steric interaction which promotes the transition toward a variety of supramolecular structures ranging from ellipsoidal vesicles, ribbon-like structures, up to final spherical mixed micelles at the large amount of bile salt of 10 mM NaDC. The findings of the obtained results give important insight for understanding the formation of different topologies in aqueous lipid–bile salt mixtures as well as stimulate new routes for liposome reconstitution–solubilisation processes suitable for technological applications.

  15. Hydrodynamic filtration in microfluidic channels as size-selection process for giant unilamellar vesicles.

    Science.gov (United States)

    Woo, Youngjun; Heo, Youhee; Shin, Kwanwoo; Yi, Gi-Ra

    2013-04-01

    We have developed hydrodynamic filtration method in microfluidic device for the efficient size-selection of polydisperse lipid vesicles for giant unilamellar vesicles (GUVs), in which vesicles were formed by electroformation method. Combining pinched flow channel design before hydrodynamic filtration, GUVs were flowed and guided to filtration channels, in which small lipid vesicles were further filtered and GUV were remained in main flow channels. For increasing the selectivity of GUV in outlets, length of slit section, or relative flow rate were controlled and drain channels were introduced for avoiding back flow. At higher flow rate in a pinched flow, the fraction of recovered GUVs (>10 microm) were increased, in which most of small vesicles were filtered.

  16. Phase equilibria in DOPC/DPPC-d62/cholesterol mixtures.

    Science.gov (United States)

    Davis, James H; Clair, Jesse James; Juhasz, Janos

    2009-01-01

    There is broad interest in the question of fluid-fluid phase coexistence in membranes, in particular, whether evidence for liquid-disordered (l(d))-liquid-ordered (l(o)) two-phase regions or membrane "rafts" can be found in natural membranes. In model membrane systems, such phase behavior is observed, and we have used deuterium nuclear magnetic resonance spectroscopy to map the phase boundaries of ternary mixtures containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), chain-perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC-d(62)), and cholesterol. For both this ternary model system and the binary DPPC-d(62)/cholesterol system, we present clear evidence for l(d)-l(o) two-phase coexistence. We have selected sample compositions to focus on this region of fluid-fluid phase coexistence and to determine its temperature and composition ranges. The deuterium nuclear magnetic resonance spectra for compositions near the l(d)-l(o) phase boundary at high cholesterol concentrations show evidence of exchange broadening or critical fluctuations in composition, similar to that reported by Vist and Davis. There appears to be a line of critical compositions ranging from 48 degrees C for a DOPC/DPPC-d(62)/cholesterol composition of 0:75:25, to approximately -8 degrees C for the composition 57:14:29. At temperatures below this two-phase region, there is a region of three-phase coexistence (l(d)-l(o)-gel). These results are collected and presented in terms of a partial ternary phase diagram that is consistent with previously reported results of Vist and Davis.

  17. Interaction of S-methyl methanethiosulfonate with DPPC bilayer

    Science.gov (United States)

    Defonsi Lestard, María E.; Díaz, Sonia B.; Tuttolomondo, María E.; Sánchez Cortez, Santiago; Puiatti, Marcelo; Pierini, Adriana B.; Ben Altabef, Aida

    2012-11-01

    The present study is a first step towards the investigation of S-methyl methanethiosulfonate (MMTS) interaction with membrane model systems like liposomes. In this paper, the interaction of MMTS with dipalmitoylphosphatidylcholine (DPPC) bilayers was studied by FTIR and SERS spectroscopy. Lysolipid effect on vesicle stability was studied. The results show that MMTS interacts to different extents with the phosphate and carbonyl groups of membranes in the gel and the liquid crystalline states. To gain a deeper insight into MMTS properties that may be potentially helpful in the design of new drugs with therapeutic effects, we performed theoretical studies that may be the basis for the design of their mode of action.

  18. Membrane Protrusion Coarsening and Nanotubulation within Giant Unilamellar Vesicles

    KAUST Repository

    Węgrzyn, Ilona

    2011-11-16

    Hydrophobic side groups on a stimuli-responsive polymer, encapsulated within a single giant unilamellar vesicle, enable membrane attachment during compartment formation at elevated temperatures. We thermally modulated the vesicle through implementation of an IR laser via an optical fiber, enabling localized directed heating. Polymer-membrane interactions were monitored using confocal imaging techniques as subsequent membrane protrusions occurred and lipid nanotubes formed in response to the polymer hydrogel contraction. These nanotubes, bridging the vesicle membrane to the contracting hydrogel, were retained on the surface of the polymer compartment, where they were transformed into smaller vesicles in a process reminiscent of cellular endocytosis. This development of a synthetic vesicle system containing a stimuli-responsive polymer could lead to a new platform for studying inter/intramembrane transport through lipid nanotubes. © 2011 American Chemical Society.

  19. The effect of temperature on supported dipalmitoylphosphatidylcholine (DPPC) bilayers: structure and lubrication performance.

    Science.gov (United States)

    Wang, Min; Zander, Thomas; Liu, Xiaoyan; Liu, Chao; Raj, Akanksha; Wieland, D C Florian; Garamus, Vasil M; Willumeit-Römer, Regine; Claesson, Per Martin; Dėdinaitė, Andra

    2015-05-01

    Phospholipids fulfill an important role in joint lubrication. They, together with hyaluronan and glycoproteins, are the biolubricants that sustain low friction between cartilage surfaces bathed in synovial fluid. In this work we have investigated how the friction force and load bearing capacity of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers on silica surfaces are affected by temperature, covering the temperature range 25-52°C. Friction forces have been determined utilizing the AFM colloidal probe technique, which showed that DPPC bilayers are able to provide low friction forces over the whole temperature interval. However, the load bearing capacity is improved at higher temperatures. We interpret this finding as being a consequence of lower rigidity and higher self-healing capacity of the DPPC bilayer in the liquid disordered state compared to the gel state. The corresponding structure of solid supported DPPC bilayers at the silica-liquid interface has been followed using X-ray reflectivity measurements, which suggests that the DPPC bilayer is in the gel phase at 25°C and 39°C and in the liquid disordered state at 55°C. Well-defined bilayer structures were observed for both phases. The deposited DPPC bilayers were also imaged using AFM PeakForce Tapping mode, and these measurements indicated a less homogeneous layer at temperatures below 37°C.

  20. Molecular dynamics simulations and free energy profile of Paracetamol in DPPC and DMPC lipid bilayers

    Indian Academy of Sciences (India)

    Yousef Nademi; Sepideh Amjad Iranagh; Abbas Yousefpour; Seyedeh Zahra Mousavi; Hamid Modarress

    2014-05-01

    Molecular dynamics (MD) simulations and biased MD simulation were carried out for the neutral form of Paracetamol inserted in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) lipid bilayers. For comparison, fully hydrated DMPC and DPPC lipid bilayers were also simulated separately without Paracetamol. The simulation time for each system was 50 ns. At two concentrations of Paracetamol, various properties of the lipid bilayer such as area per lipid, order parameter, diffusion coefficient, radial distribution function, electrostatic potential, mass density and hydrogen bonds have been calculated. Also, the convergence in time of the free energy profile of the Paracetamol along a DPPC bilayer normal was calculated by umbrella sampling method. From the obtained results, it can be concluded that neutral form of Paracetamol shows a generally similar behaviour in DPPC and DMPC lipid bilayers. It was shown that the addition of Paracetamol causes a decrease in tail order parameter of both DPPC and DMPC lipid bilayers and the tail of Paracetamol adopts an inward orientation in the lipid bilayers. Also from the free energy profile, the high penetration barrier in the bilayer centre was determined.

  1. Asymmetric distribution of cone-shaped lipids in a highly curved bilayer revealed by a small angle neutron scattering technique

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Y; Imai, M [Department of Physics, Ochanomizu University, Bunkyo, Tokyo 112-8610 (Japan); Urakami, N [Department of Physics and Information Sciences, Yamaguchi University, Yamaguchi 753-8512 (Japan); Taniguchi, T, E-mail: imai@phys.ocha.ac.jp [Department of Chemical Engineering, Kyoto University, Kyoto 606-8510 (Japan)

    2011-07-20

    We have investigated the lipid sorting in a binary small unilamellar vesicle (SUV) composed of cone-shaped (1,2-dihexanoyl-sn-glycero-3-phosphocholine: DHPC) and cylinder-shaped (1,2-dipalmitoyl-sn-glycero-3-phosphocholine: DPPC) lipids. In order to reveal the lipid sorting we adopted a contrast matching technique of small angle neutron scattering (SANS), which extracts the distribution of deuterated lipids in the bilayer quantitatively without steric modification of lipids as in fluorescence probe techniques. First the SANS profile of protonated SUVs at a film contrast condition showed that SUVs have a spherical shape with an inner radius of 190 A and a bilayer thickness of 40 A. The SANS profile of deuterated SUVs at a contrast matching condition showed a characteristic scattering profile, indicating an asymmetric distribution of cone-shaped lipids in the bilayer. The characteristic profile was described well by a spherical bilayer model. The fitting revealed that most DHPC molecules are localized in the outer leaflet. Thus the shape of the lipid is strongly coupled with the membrane curvature. We compared the obtained asymmetric distribution of the cone-shaped lipids in the bilayer with the theoretical prediction based on the curvature energy model.

  2. Asymmetric distribution of cone-shaped lipids in a highly curved bilayer revealed by a small angle neutron scattering technique

    Science.gov (United States)

    Sakuma, Y.; Urakami, N.; Taniguchi, T.; Imai, M.

    2011-07-01

    We have investigated the lipid sorting in a binary small unilamellar vesicle (SUV) composed of cone-shaped (1,2-dihexanoyl-sn-glycero-3-phosphocholine: DHPC) and cylinder-shaped (1,2-dipalmitoyl-sn-glycero-3-phosphocholine: DPPC) lipids. In order to reveal the lipid sorting we adopted a contrast matching technique of small angle neutron scattering (SANS), which extracts the distribution of deuterated lipids in the bilayer quantitatively without steric modification of lipids as in fluorescence probe techniques. First the SANS profile of protonated SUVs at a film contrast condition showed that SUVs have a spherical shape with an inner radius of 190 Å and a bilayer thickness of 40 Å. The SANS profile of deuterated SUVs at a contrast matching condition showed a characteristic scattering profile, indicating an asymmetric distribution of cone-shaped lipids in the bilayer. The characteristic profile was described well by a spherical bilayer model. The fitting revealed that most DHPC molecules are localized in the outer leaflet. Thus the shape of the lipid is strongly coupled with the membrane curvature. We compared the obtained asymmetric distribution of the cone-shaped lipids in the bilayer with the theoretical prediction based on the curvature energy model.

  3. Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes

    Directory of Open Access Journals (Sweden)

    Jennifer Tang

    2015-09-01

    Full Text Available NIt was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains’ electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.

  4. Effect of gamma irradiation on hyaluronic acid and dipalmitoylphosphatidylcholine (DPPC) interaction

    Science.gov (United States)

    Ahmad, Ainee Fatimah; Mohd, Hur Munawar Kabir; bin Ayob, Muhammad Taqiyuddin Mawardi; Rosli, Nur Ratasha Alia Md; Mohamed, Faizal; Radiman, Shahidan; Rahman, Irman Abdul

    2014-09-01

    DPPC lipids are the major component constituting the biological membrane, and their importances in various physiological functions are well documented. Hyaluronic acid (HA) in the synovial joint fluid functions as a lubricant, shock absorber and a nutrient carrier. Gamma irradiation has also been found to be effective in depolymerizing and cleaving molecular chains related to free radicals, thus extends with changes in chemical composition as well as its physiological functions. This research are conducted to investigate the hyaluronic acid (HA) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) interaction in form of vesicles and its effect to gamma radiation. The size of DPPC vesicles formed via gentle hydration method is between 100 to 200 nm in diameter. HA (0.1, 0.5 and 1.0 mg/ml) was added into the vesicles and characterized by using TEM to determine vesicle size distributions, fusion and rupture of DPPC structure. The results demonstrated that the size of the vesicles approximately between 200 to 300 nm which caused by vesicles fusion with HA and formed even larger vesicles. After being irradiated by 0 to 200 Gy, the size of vesicles decreased as HA was degraded. To elucidate the mechanism of these effects, FTIR spectra were carried out and have shown that at absorption bands at 1700-1750 cm-1 due to formation of carboxylic acid and leads to alteration of HA structure.

  5. Effect of gamma irradiation on hyaluronic acid and dipalmitoylphosphatidylcholine (DPPC) interaction

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Ainee Fatimah; Mohd, Hur Munawar Kabir; Taqiyuddin Mawardi bin Ayob, Muhammad; Rosli, Nur Ratasha Alia Md; Mohamed, Faizal; Radiman, Shahidan; Rahman, Irman Abdul [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2014-09-03

    DPPC lipids are the major component constituting the biological membrane, and their importances in various physiological functions are well documented. Hyaluronic acid (HA) in the synovial joint fluid functions as a lubricant, shock absorber and a nutrient carrier. Gamma irradiation has also been found to be effective in depolymerizing and cleaving molecular chains related to free radicals, thus extends with changes in chemical composition as well as its physiological functions. This research are conducted to investigate the hyaluronic acid (HA) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) interaction in form of vesicles and its effect to gamma radiation. The size of DPPC vesicles formed via gentle hydration method is between 100 to 200 nm in diameter. HA (0.1, 0.5 and 1.0 mg/ml) was added into the vesicles and characterized by using TEM to determine vesicle size distributions, fusion and rupture of DPPC structure. The results demonstrated that the size of the vesicles approximately between 200 to 300 nm which caused by vesicles fusion with HA and formed even larger vesicles. After being irradiated by 0 to 200 Gy, the size of vesicles decreased as HA was degraded. To elucidate the mechanism of these effects, FTIR spectra were carried out and have shown that at absorption bands at 1700–1750 cm{sup −1} due to formation of carboxylic acid and leads to alteration of HA structure.

  6. Surface properties and morphology of mixed POSS-DPPC monolayers at the air/water interface.

    Science.gov (United States)

    Rojewska, Monika; Skrzypiec, Marta; Prochaska, Krystyna

    2017-02-01

    From the point of view of the possible medical applications of POSS (polyhedral oligomeric silsesquioxanes), it is crucial to analyse interactions occurring between POSS and model biological membrane at molecular level. Knowledge of the interaction between POSS and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) allows prediction of the impact of POSS contained in biomaterials or cosmetics on a living organism. In the study presented, the surface properties and morphology of Langmuir monolayers formed by mixtures of POSS and the phospholipid (DPPC) at the air/water surface are examined. We selected two POSS derivatives, with completely different chemical structure of substituents attached to the corner of the silicon open cage, which allowed the analysis of the impact of the character of organic moieties (strongly hydrophobic or clearly hydrophilic) on the order of POSS molecules and their tendency to form self-aggregates at the air/water surface. POSS derivatives significantly changed the profile of the π-A isotherms obtained for DPPC but in different ways. On the basis of the regular solution theory, the miscibility and stability of the two components in the monolayer were analysed in terms of compression modulus (Cs(-1)), excess Gibbs free energy (ΔGexc), activity coefficients (γ) and interaction parameter (ξ). The results obtained indicate the existence of two different interaction mechanisms between DPPC and POSS which depend on the chemical character of moieties present in POSS molecules.

  7. Microstructural Phase Changes of DPPC-Ergosterol Supported Membranes Stressed by Ethanol

    Science.gov (United States)

    Vanegas, Juan; Block, David; Faller, Roland; Longo, Marjorie

    2010-03-01

    Microstructure of DPPC-Ergosterol supported lipid bilayers (SLBs) stressed by ethanol is examined at the nanoscopic level using atomic force microscopy (AFM). Alcohols such as ethanol are known to cause changes in the phase behavior of phospholipids as well as inducing the formation of an interdigitated phase of reduced thickness, where the hydrophobic tails of the top and bottom lipids intercalate causing an increase in the area per lipid as well as the solvent exposed surface of the headgroups. SLBs composed of 75-100 mole % 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) and 0-25 mole % ergosterol were deposited on mica through the vesicle deposition method. In order to observe the ethanol-induced phase changes that can be observed in free bilayers, the vesicles must be prepared in buffer solution containing ethanol. The presence of salt is required to reduce the effect of the strong interaction between the bilayers and the support, which in the absence of ethanol and salt induces the formation of a tilted phase similar to the interdigitated phase in DPPC bilayers deposited above the melting temperature. As previously observer by other groups, ethanol-induced changes in SLBs often require heating above the transition temperature after addition of ethanol, or sample preparation in the presence of the alcohol. The later method was used as it produces more consistent results and the observations agree well with the previously reported phase diagram of DPPC-Ergosterol with ethanol.

  8. DPPC-cholesterol phase diagram using coarse-grained Molecular Dynamics simulations.

    Science.gov (United States)

    Wang, Yin; Gkeka, Paraskevi; Fuchs, Julian E; Liedl, Klaus R; Cournia, Zoe

    2016-11-01

    Cholesterol-phospholipid bilayers continue to be the current state of the art in membrane models and serve as representative systems for studying the effect of cholesterol on the cell membrane. As the mixing of different lipid species requires long spatio-temporal scales, coarse-grained models have gained increasing popularity in modeling such membrane systems. In this paper, a systematic study of the MARTINI coarse-grained model for the DPPC-cholesterol binary system has been performed. We construct the phase diagram of DPPC lipid bilayers in the presence of different cholesterol concentrations and at different temperatures using coarse-grained Molecular Dynamics (MD) simulations with the MARTINI force field. The phase diagram based on the condensation effect is directly comparable to available experimental data and demonstrates qualitative agreement over all cholesterol concentrations. Self-assembled bilayers quantitatively reproduce experimental observables, such as lateral diffusion of lipids, electron density, area per lipid and lipid order parameters. The phase diagram of the DPPC-cholesterol binary system also reveals the profound effect of cholesterol on the physical properties of phospholipid bilayers such lipid order, diffusion, and fluidity. Cholesterol induces the liquid-ordered phase, which increases the fluidity of the phospholipid hydrocarbon chains above the gel to liquid-crystalline phase transition temperature and decreases it below the phase transition. The present study suggests that the MARTINI force field can be successfully used to obtain molecular level insights into cholesterol-DPPC model membranes. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Cholesterol effect on water permeability through DPPC and PSM lipid bilayers: a molecular dynamics study.

    Science.gov (United States)

    Saito, Hiroaki; Shinoda, Wataru

    2011-12-29

    Water permeability of two different lipid bilayers of dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) in the absence and presence of cholesterol (0-50 mol %) have been studied by molecular dynamics simulations to elucidate the molecular mechanism of the reduction in water leakage across the membranes by the addition of cholesterol. An enhanced free energy barrier was observed in these membranes with increased cholesterol concentration, and this was explained by the reduced cavity density around the cholesterol in the hydrophobic membrane core. There was an increase of trans conformers in the hydrophobic lipid chains adjacent to the cholesterol, which reduced the cavity density. The enhanced free energy barrier was found to be the main reason to reduce the water permeability with increased cholesterol concentration. At low cholesterol concentrations the PSM bilayer exhibited a higher free energy barrier than the DPPC bilayer for water permeation, while at greater than 30 mol % of cholesterol the difference became minor. This tendency for the PSM and DPPC bilayers to resemble each other at higher cholesterol concentrations was similar to commonly observed trends in several structural properties, such as order parameters, cross-sectional area per molecule, and cavity density profiles in the hydrophobic regions of bilayer membranes. These results demonstrate that DPPC and PSM bilayers with high cholesterol contents possess similar physical properties, which suggests that the solubility of cholesterol in these lipid bilayers has importance for an understanding of multicomponent lipid membranes with cholesterol.

  10. Formation of ring calcium oxalate patterns induced by domains in DPPC Langmuir-Blodgett films

    Institute of Scientific and Technical Information of China (English)

    Yi Ming Liu; Sui Ping Deng; Hui Zheng; Jian Ming Ouyang

    2007-01-01

    The ring patterns of calcium oxalate crystals were induced by domains in Langmuir-Blodgett (LB) films of dipalmitoylpho-sphatidylcholine (DPPC). The result was explained by the defects at the ring boundaries of liquid condensed (LC) and liquid expanded (LE) phases of LB film. These boundaries could provide less free energy and much more nucleating sites for COM crystals.

  11. Quantification of leakage from large unilamellar lipid vesicles by fluorescence correlation spectroscopy

    DEFF Research Database (Denmark)

    Kristensen, Kasper; Henriksen, Jonas Rosager; Andresen, Thomas Lars

    2014-01-01

    that mastoparan X forms transient transmembrane pores in POPC/POPG (3:1) vesicles, resulting in size-dependent leakage of molecules from the vesicles. We conclude the paper by discussing some of the advantages and limitations of FCS as compared to other existing methods to measure leakage from large unilamellar...

  12. Giant Unilamellar Vesicle Electroformation: From Lipid Mixtures to Native Membranes Under Physiological Conditions

    DEFF Research Database (Denmark)

    Meleard, Philippe; Bagatolli, Luis; Pott, Tanja

    2009-01-01

    Giant unilamellar vesicles (GUVs) are well-known model systems, especially because they are easily observable using optical microscopy. In this chapter, we revisit in detail the versatile GUV electroformation protocol. We demonstrate how GUV electroformation can be adapted to various membrane...

  13. ATR-IR spectroscopic study of the structural changes in the hydrophobic region of ICPAN/DPPC bilayers

    Science.gov (United States)

    Cieślik-Boczula, Katarzyna; Czarnik-Matusewicz, Bogusława; Perevozkina, Margarita; Filarowski, Aleksander; Boens, Noël; De Borggraeve, Wim M.; Koll, Aleksander

    2008-04-01

    Structural changes in the hydrophobic region in the self-aggregates of the long hydrocarbon chain ICPAN ((( N, N-dimethyl- N-octyl-2-ammonioethyl)-3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate bromide)) homologues and their interaction with a DPPC (dipalmitoylophosphatidylcholine) bilayer were the subject of detailed investigation using ATR infrared spectroscopy. On the base of analysis of the bands assigned to CH 2 stretching, scissoring, and rocking and CH wagging vibrations it was revealed that the hydrophobic parts ICPANs adopt a gauche-rich disordering structure. Moreover, it was shown that the micellar- or lamellar-like character of these structures depends on the hydrocarbon chain length. Results obtained from the ICPAN/DPPC mixtures indicate an increase in the conformational disorder in hydrophobic part compare to pure DPPC film. This effect depends on the length of the aliphatic chain of ICPAN homologues and on the relative concentrations of DPPC and ICPAN.

  14. Moving-window 2D correlation spectroscopy in studies of fluphenazine-DPPC dehydrated film as a function of temperature

    Science.gov (United States)

    Szwed, Joanna; Cieślik-Boczula, Katarzyna; Czarnik-Matusewicz, Bogusława; Jaszczyszyn, Agata; Gąsiorowski, Kazimierz; Świątek, Piotr; Malinka, Wiesław

    2010-06-01

    The effect of incorporating fluphenazine (FPh) into the dipalmitoylphosphatidylcholine (DPPC) multibilayers was studied by means of two-dimensional correlation spectroscopy (2DCOS) applied to attenuated total reflection (ATR) infrared spectra. DPPC is used as a model membrane that mimics the organization of lipids in biological membranes and their interaction with FPh. ATR-IR spectra for both DPPC dry film alone and the film doped with FPh were recorded as a function of temperature to provide information about the interaction between FPh molecules and DPPC lipid. The chain-melting phase-transition temperature changes are strictly correlated with the conformational order of the lipid hydrocarbon chains. To gain deeper insight into the accompanying spectral changes, we employed moving-window 2D correlation spectroscopy. Subdividing all the measurements from 10 to 90 °C into 20° subsets enables a detailed identification of spectral features induced by embedding FPh into DPPC multilayers. Moving-window analysis of the power spectra for the ν asym,symCH 2, δ sCH 2, and δ rCH 2 vibrations provides evidence that FPh is embedded in the region between the bilayers, penetrating their hydrophilic part, which destabilizes the interchain interaction. Above 60 °C the FPh-DPPC system reaches the liquid crystalline phase with the well-established location of FPh. A further temperature increase to 90 °C has little effect on the intrachain conformational order and the packing character of the FPh-DPPC system in the liquid crystalline phase. In addition, FPh hinders the formation of large domains. Comparison of the moving-window analysis done by using slice spectra for DPPC and FPh-doped DPPC dry film for ν asym,symCH 2, νC dbnd O, and νPO2- shows that the interaction between the DPPC and FPh molecules is accompanied by very distinct spectral changes located in a both lower and narrower temperature range than those observed in pure DPPC film.

  15. Effects of oxyethylated glycerol cryoprotectants on phase transitions of DPPC model membranes

    Directory of Open Access Journals (Sweden)

    Kasian N. A.

    2015-04-01

    Full Text Available Aim. To determine the effect of the oxyethylated glycerol cryoprotectants (OEGn with polymerization degrees n = 5, 25, 30 on the phase states and phase transitions of dipalmitoylphosphatidylcholine (DPPC-based model membranes. Methods. Differential scanning calorimetry. Results. Model lipid membranes on water/OEGn and water/glycerol subphases with varying cryoprotectant concentrations from 0 to ~ 100 % w/w were studied. A significant raise in the pre-transition and main phase transition temperatures with increasing OEGn concentration was noted whereas the membrane melting peak persist to 100 % w/w OEGn. A sharp increase in the melting enthalpy was observed for OEGn = 5. Conclusions. The solvating ability of the subphase in DPPC membranes decreases in the order water > glycerol > OEGn = 5 > OEGn = 25 > OEGn = 30, which correlates with the relative number of groups effectively contributing to the solvation process.

  16. Hydrophobic thickness, lipid surface area and polar region hydration in monounsaturated diacylphosphatidylcholine bilayers: SANS study of effects of cholesterol and beta-sitosterol in unilamellar vesicles.

    Science.gov (United States)

    Gallová, J; Uhríková, D; Kucerka, N; Teixeira, J; Balgavý, P

    2008-11-01

    The influence of a mammalian sterol cholesterol and a plant sterol beta-sitosterol on the structural parameters and hydration of bilayers in unilamellar vesicles made of monounsaturated diacylphosphatidylcholines (diCn:1PC, n=14-22 is the even number of acyl chain carbons) was studied at 30 degrees C using small-angle neutron scattering (SANS). Recently published advanced model of lipid bilayer as a three-strip structure was used with a triangular shape of polar head group probability distribution (Kucerka et al., Models to analyze small-angle neutron scattering from unilamellar lipid vesicles, Physical Review E 69 (2004) Art. No. 051903). It was found that 33 mol% of both sterols increased the thickness of diCn:1PC bilayers with n=18-22 similarly. beta-sitosterol increased the thickness of diC14:1PC and diC16:1PC bilayers a little more than cholesterol. Both sterols increased the surface area per unit cell by cca 12 A(2) and the number of water molecules located in the head group region by cca 4 molecules, irrespective to the acyl chain length of diCn:1PC. The structural difference in the side chain between cholesterol and beta-sitosterol plays a negligible role in influencing the structural parameters of bilayers studied.

  17. Critical behaviour in DOPC/DPPC/cholesterol mixtures: static (2)H NMR line shapes near the critical point.

    Science.gov (United States)

    Davis, James H; Schmidt, Miranda L

    2014-05-06

    Static (2)H NMR spectroscopy is used to study the critical behavior of mixtures of 1,2-dioleoyl-phosphatidylcholine/1,2-dipalmitoyl-phosphatidylcholine (DPPC)/cholesterol in molar proportion 37.5:37.5:25 using either chain perdeuterated DPPC-d62 or chain methyl deuterated DPPC-d6. The temperature dependence of the first moment of the (2)H spectrum of the sample made with DPPC-d62 and of the quadrupolar splittings of the chain-methyl-labeled DPPC-d6 sample are directly related to the temperature dependence of the critical order parameter η, which scales as [Formula: see text] near the critical temperature. Analysis of the data reveals that for the chain perdeuterated sample, the value of Tc is 301.51 ± 0.1 K, and that of the critical exponent, βc = 0.391 ± 0.02. The line shape analysis of the methyl labeled (d6) sample gives Tc = 303.74 ± 0.07 K and βc = 0.338 ± 0.009. These values obtained for βc are in good agreement with the predictions of a three-dimensional Ising model. The difference in critical temperature between the two samples having nominally the same molar composition arises because of the lowering of the phase transition temperature that occurs due to the perdeuteration of the DPPC.

  18. Interactions of Borneol with DPPC Phospholipid Membranes: A Molecular Dynamics Simulation Study

    Directory of Open Access Journals (Sweden)

    Qianqian Yin

    2014-11-01

    Full Text Available Borneol, known as a “guide” drug in traditional Chinese medicine, is widely used as a natural penetration enhancer in modern clinical applications. Despite a large number of experimental studies on borneol’s penetration enhancing effect, the molecular basis of its action on bio-membranes is still unclear. We carried out a series of coarse-grained molecular dynamics simulations with the borneol concentration ranging from 3.31% to 54.59% (v/v, lipid-free basis to study the interactions of borneol with aDPPC(1,2-dipalmitoylsn-glycero-3-phosphatidylcholine bilayer membrane, and the temperature effects were also considered. At concentrations below 21.89%, borneol’s presence only caused DPPC bilayer thinning and an increase in fluidity; A rise in temperature could promote the diffusing progress of borneol. When the concentration was 21.89% or above, inverted micelle-like structures were formed within the bilayer interior, which led to increased bilayer thickness, and an optimum temperature was found for the interaction of borneol with the DPPC bilayer membrane. These findings revealed that the choice of optimal concentration and temperature is critical for a given application in which borneol is used as a penetration enhancer. Our results not only clarify some molecular basis for borneol’s penetration enhancing effects, but also provide some guidance for the development and applications of new preparations containing borneol.

  19. A GALA lipopeptide mediates pH- and membrane charge dependent fusion with stable giant unilamellar vesicles

    DEFF Research Database (Denmark)

    Etzerodt, Thomas P.; Trier, Sofie; Henriksen, Jonas R.

    2012-01-01

    ,2-diamino propanoic acid (Dap) moiety, yielding the lipopeptide dimyristoyl-Dap-GALA (DMDGALA). We have investigated DMDGALA as a component in large unilamellar vesicles (LUVs) and demonstrate pH-triggered fusion of peptide containing LUVs with stable target giant unilamellar vesicles (GUVs), which were...... used as simple mimics of cell membranes. The number of fusion events was large at pH 5.0, which is a physiologically relevant pH-range for a drug delivery system....

  20. Optical stretching of giant unilamellar vesicles with an integrated dual-beam optical trap.

    Science.gov (United States)

    Solmaz, Mehmet E; Biswas, Roshni; Sankhagowit, Shalene; Thompson, James R; Mejia, Camilo A; Malmstadt, Noah; Povinelli, Michelle L

    2012-10-01

    We have integrated a dual-beam optical trap into a microfluidic platform and used it to study membrane mechanics in giant unilamellar vesicles (GUVs). We demonstrate the trapping and stretching of GUVs and characterize the membrane response to a step stress. We then measure area strain as a function of applied stress to extract the bending modulus of the lipid bilayer in the low-tension regime.

  1. The molecular organization of prenylated flavonoid xanthohumol in DPPC multibilayers: X-ray diffraction and FTIR spectroscopic studies.

    Science.gov (United States)

    Arczewska, Marta; Kamiński, Daniel M; Górecka, Ewa; Pociecha, Damian; Rój, Edward; Sławińska-Brych, Adrianna; Gagoś, Mariusz

    2013-02-01

    Xanthohumol (XN) is the major prenylated flavonoid found in hop resin. It has attracted considerable attention in recent years due to its wide spectrum of biological activities and the beneficial effect on human health. Since lipid membrane is first target for biologically active compounds, we decided to investigate the influence of XN on the dipalmitoylphosphatidylcholine (DPPC) multibilayers. Interactions of XN with DPPC were investigated as a function of temperature and its concentration by using X-ray diffraction and the ATR-FTIR spectroscopy techniques. The aim of understanding the mechanisms of molecular interactions between XN and DPPC was to indicate the localization of the XN with respect to the membrane and the type of interaction with phospholipids. The results revealed that XN changes the physical properties of the DPPC multibilayers in the form of dry film. A new complex formation between XN and DPPC is reported. The detailed analysis of refraction effect indicates the changes in electron density ratio between hydrophobic and hydrophilic zones of lipid at phase transition. This is in compliance with reported changes in FTIR spectra where at pretransition XN moves from interface region between polar heads to the neighborhood of phosphate groups.

  2. Radiation-induced peroxidation of small unilamellar vesicles of phosphatidylcholine generated by sonication

    Energy Technology Data Exchange (ETDEWEB)

    Vitrac, H. [Univ. Paris, CNRS, Lab. de Chimie Physique, Paris CEDEX (France)]. E-mail: Heidi.Vitrac@univ-paris5.fr; Courregelongue, M. [CNRS, Groupe de Recherche en Physique et Biophysique, Paris (France); Couturier, M. [Hopital Kremlin Bicetre, Lab. de Biochimie et INSERM (France); Collin, F. [Univ. Paris, CNRS, Lab. de Chimie Physique, Paris CEDEX (France); Therond, P. [Hopital Kremlin Bicetre, Lab. de Biochimie et INSERM (France); Remita, S. [Univ. Paris, CNRS, Lab. de Chimie Physique, Paris CEDEX (France); Peretti, P.; Jore, D.; Gardes-Albert, M. [Univ. Paris, CNRS, Lab. de Chimie Physique, Paris CEDEX (France)

    2004-02-01

    The present study was aimed at determining the peroxidation of model membranes constituted of liposomes of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) submitted to hydroxyl free radicals (generated by {gamma}-radiolysis) attack. Liposomes of PLPC were prepared using the sonication technique, and dynamic light-scattering (DLS) measurements allowed characterization of the liposomal dispersions. Irradiation damages in sonication-generated liposomes were assessed by monitoring several oxidation products, such as conjugated dienes (by means of UV-visible spectrophotometry) and hydroperoxides (using reverse phase high-performance liquid chromatography (HPLC) associated with chemiluminescence detection). It has been shown that three different families of hydroperoxides are formed: the first one (at low radiation doses) results from HO{center_dot} attack on the linoleyl chain of PLPC, giving phosphatidylcholine hydroperoxides possessing a conjugated dienic structure; the two others (at high radiation doses) are obtained by the secondary HO{center_dot} attack on the primary hydroperoxide family. The quantification of these products associated with the comparison of their radiation-dose-dependent formation has provided valuable information concerning the mechanisms of their formation. Analysis by HPLC - mass spectrometry has confirmed the presence of hydroperoxides and underlined various other products, like chain-shortened fragments and oxygenated derivatives of polyunsaturated sn-2 fatty acyl chain residues. Structural assignment proposals of some oxidation products have been proposed. (author)

  3. Quantitative Studies of Antimicrobial Peptide Pore Formation in Large Unilamellar Vesicles by Fluorescence Correlation Spectroscopy (FCS)

    DEFF Research Database (Denmark)

    Kristensen, Kasper; Henriksen, Jonas Rosager; Andresen, Thomas Lars

    2013-01-01

    leakage of fluorescent probes of different sizes through transmembrane pores formed by each of the three representative antimicrobial peptides: melittin, magainin 2, and mastoparan X. The experimental results demonstrate that leakage assays based on fluorescence correlation spectroscopy offer new...... and detailed insight into the size and cooperative nature of transmembrane pores formed by antimicrobial peptides that is not available from the conventional quenching-based leakage assays....... highly warranted. Fluorescence correlation spectroscopy is a biophysical technique that can be used to quantify leakage of fluorescent probes of different sizes from large unilamellar vesicle, thereby potentially becoming such a new tool. However, the usage of fluorescence correlation spectroscopy...

  4. The additional phase transition of DPPC monolayers at high surface pressure confirmed by GIXD study

    DEFF Research Database (Denmark)

    Shen, Chen; Serna, Jorge B. de la; Struth, Bernd

    Pulmonary surfactant forms the alveolar monolayer at the air/aqueous interface within the lung. During the breathing process, the surface pressure periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. The monolayer consists...... of ~90% of lipid with 10% integrated proteins. Among its lipid compounds, di- palmitoyl-phosphatidylcholine (DPPC) dominates (~45wt%). No other lipid but DPPC was so far reported to be compressible to very high surface pressure (~70mN/m) before its monolayer collapsed. Its liquid......-expanded/liquid-condensed (LE/LC) phase transition at ~10mN/m is well known. Here we present results from Langmuir isotherm measurements that evidence a so far not documented second phase transition at elevated surface pressure Π (~50mN/m). The varying lateral structures of the monolayer at 8mN/m, 20mN/m, 30mN/m, 40mN/m, 50m...

  5. Preparation of giant unilamellar CdTe quantum dot vesicles and their metabolic pathway in vivo

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Glutathione (GSH) capped CdTe quantum dots (QDs) with photoluminescence quantum yields of 61% and the maximum emitting at 601.2 nm were prepared in water phase.Giant unilamellar CdTe quantum dot vesicles (GUVs-CdTe),with diameters larger than 1.5 μm,were obtained using lower-pressure evaporation techniques with soybean lecithin.Compared with other QD liposomes,the entrapment efficiency of GUVs-CdTe for QDs has been significantly improved to 86.3%.After GUVs-CdTe were injected into mice through the tail vein,the fluorescence microscopy of tissue sections showed that GUVs-CdTe could not pass through the blood-brain barrier and air-blood barrier,which were removed mostly by the reticuloendothelial system and were widely distributed in the spleen and the liver.This behavior is the same as the character of the metabolic pathway of giant unilamellar vesicles by intravenous injections in mice.

  6. Direct Synthesis of Unilamellar MgAl-LDH Nanosheets and Stacking in Aqueous Solution.

    Science.gov (United States)

    Liang, Dujuan; Yue, Wenbo; Sun, Genban; Zheng, Dong; Ooi, Kenta; Yang, Xiaojing

    2015-11-17

    Two-dimensional (2D) materials, such as graphene, inorganic oxides, and hydroxides, are one of the most extensively studied classes of materials due to their unilamellar crystallites or nanosheet structures. In this study, instead of using the universal exfoliation method of the bulky crystal precursor, 2D crystals/nanosheets of MgAl-layered double hydroxides (LDHs) were synthesized in formamide. We propose that the obtained crystals are unilamellar according to the XRD, TEM, and AFM observations. The HRTEM and fast Fourier transform images confirm that the crystal structures are the same as those of the exfoliated MgAl-LDH nanosheets. The directly synthesized sheets can stack into a 3D crystal structure, which is the same as that of typical LDHs except for the disordered orientation of the a-/b- crystal axis of each sheet. This result provides not only a novel approach to the preparation of 2D crystals but also insight into the formation mechanism of LDHs.

  7. Study of Raft Domains in Model Membrane of DPPC/PE/Cholesterol

    Science.gov (United States)

    Lor, Chai; Hirst, Linda

    2010-10-01

    Raft domains in bilayer membrane are thought to play an important role in many cell functions such as cell signaling or trans-membrane protein activation. Here we use a model membrane consisting of DPPC/PE/cholesterol to examine the structure of membrane rafts and phase interactions. In particular we are interested in lipids containing the highly polyunsaturated fatty acid DHA. We use both atomic force microscopy (AFM) and fluorescence microscopy to obtain information on the structural properties of raft regions and track cholesterol. As expected, we find phase separation of raft regions between saturated and unsaturated lipids. Moreover, we find that the roughness of the domains change with varying cholesterol concentration possibly due to overpacking. This model study provides further understanding of the role of cholesterol in bilayer membrane leading towards a better knowledge of cell membranes.

  8. Miscibility of dl-α-tocopherol β-glucoside in DPPC monolayer at air/water and air/solid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Neunert, G. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Makowiecki, J.; Piosik, E.; Hertmanowski, R. [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland); Polewski, K. [Department of Physics and Biophysics, Poznan University of Life Sciences, 60-637 Poznan (Poland); Martynski, T., E-mail: tomasz.martynski@put.poznan.pl [Faculty of Technical Physics, Poznan University of Technology, 60-965 Poznan (Poland)

    2016-10-01

    The role of newly synthesized tocopherol glycosidic derivative in modifying molecular organization and phase transitions of phospholipid monolayer at the air/water interface has been investigated. Two-component Langmuir films of dl-α-tocopheryl β-D-glucopyranoside (BG) mixed with dipalmitoyl phosphatidylcholine (DPPC) in the whole range of mole fractions were formed at the water surface. An analysis of surface pressure versus mean molecular area (π-A) isotherms and Brewster angle microscope images showed that the presence of BG molecules changes the structure and packing of the DPPC monolayer in a BG concentration dependent manner. BG molecules incorporated into DPPC monolayer inhibit its liquid expanded to liquid condensed phase transition proportionally to the BG concentration. The monolayers were also transferred onto solid substrates and visualized using an atomic force microscope. The results obtained indicate almost complete miscibility of BG and DPPC in the monolayers at surface pressures present in the biological cell membrane (30-35·10{sup -3} N·m{sup -1}) for a BG mole fraction as high as 0.3. This makes the monolayer less packed and more disordered, leading to an increased permeability. The results support our previous molecular dynamics simulation data. - Highlights: • Langmuir films of α-tocopherol derivative with DPPC was studied thermodynamically. • Mixed DPPC/BG films were transferred onto mica substrates for topography imaging by using AFM. • Miscibility of BG/DPPC films at surface pressures present in membranes was observed up to MF = 0.3.

  9. Protein-protein and protein-lipid interactions in domain-assembly : Lessons from giant unilamellar vesicles

    NARCIS (Netherlands)

    Kahya, Nicoletta

    2010-01-01

    Giant Unilamellar Vesicles (GUVs) provide a key model membrane system to study lipid-lipid and lipid-protein interactions, which are relevant to vital cellular processes, by (single-molecule) optical microscopy. Here, we review the work on reconstitution techniques for membrane proteins and other pr

  10. iGUVs: Preparing Giant Unilamellar Vesicles with a Smartphone and Lipids Easily Extracted from Chicken Eggs

    Science.gov (United States)

    Almendro Vedia, Víctor G.; Natale, Paolo; Chen, Su; Monroy, Francisco; Rosilio, Veronique; López-Montero, Ivan

    2017-01-01

    Since the first report of electroformed micrometer-sized liposomes in the 1980s, giant unilamellar vesicles (GUVs) have generated a lot of interest in the biophysical and biochemical communities. However, their penetration rate in high school or at the undergraduate level is still limited because of the requirement of specialized materials for…

  11. INTERACTION OF CLATHRIN WITH LARGE UNILAMELLAR PHOSPHOLIPID-VESICLES AT NEUTRAL PH - LIPID DEPENDENCE AND PROTEIN PENETRATION

    NARCIS (Netherlands)

    SEPPEN, J; RAMALHOSANTOS, J; DECARVALHO, AP; TERBEEST, M; KOK, JW; DELIMA, MCP; HOEKSTRA, D

    1992-01-01

    The interaction of clathrin with large unilamellar vesicles of various lipid compositions has been examined at neutral pH. Clathrin induces leakage of contents of vesicles that contain the acidic phospholipid phosphatidylserine. Leakage is greatly enhanced by the presence of a relatively minor

  12. Quantitative optical microscopy and micromanipulation studies on the lipid bilayer membranes of giant unilamellar vesicles

    DEFF Research Database (Denmark)

    Bagatolli, Luis; Needham, David

    2014-01-01

    some of their most important contributions to our understanding of lipid bilayer membranes; and (iii) outline studies that would utilize both techniques simultaneously on the same vesicle thus bringing the ability to characterize structure and strain responses together with the direct application......This manuscript discusses basic methodological aspects of optical microscopy and micromanipulation methods to study membranes and reviews methods to generate giant unilamellar vesicles (GUVs). In particular, we focus on the use of fluorescence microscopy and micropipette manipulation techniques...... to study composition-structure-property materials relationships of free-standing lipid bilayer membranes. Because their size (~5 to 100 m diameter) that is well above the resolution limit of regular light microscopes, GUVs are suitable membrane models for optical microscopy and micromanipulation...

  13. Two-Dimensional Supramolecular Polymers Embodying Large Unilamellar Vesicles in Water.

    Science.gov (United States)

    Chen, Shigui; Polen, Shane M; Wang, Lu; Yamasaki, Makoto; Hadad, Christopher M; Badjić, Jovica D

    2016-09-07

    We hereby describe a strategy for obtaining novel topological nanostructures consisting of dual-cavity basket 1, forming a curved monolayer of large unilamellar vesicles in water (CAC < 0.25 μM), and bivalent guests 4/5 populating the cavities of such bolaamphiphilic hosts. On the basis of the results of (1)H NMR spectroscopy, electron microscopy, and dynamic light scattering measurements, we postulated that divalent guest molecules 4/5 cover the curved vesicular surface in a lateral fashion to satisfy the complexation [2 + 2] valency and thereby give stable two-dimensional supramolecular polymers [1⊂4]n and [1⊂5]n. The results of experimental studies are also supported with coarse-grained molecular dynamics simulations and molecular mechanics. Our discovery about the assembly of novel vesicular structures could be of interest for stabilization/functionalization of liposomal surfaces as well as detection of polyvalent molecules and removal of targeted substances from aqueous environments.

  14. Magnetically Triggered Release From Giant Unilamellar Vesicles: Visualization By Means Of Confocal Microscopy

    KAUST Repository

    Nappini, Silvia

    2011-04-07

    Magnetically triggered release from magnetic giant unilamellar vesicles (GUVs) loaded with Alexa fluorescent dye was studied by means of confocal laser scanning microscopy (CLSM) under a low-frequency alternating magnetic field (LF-AMF). Core/shell cobalt ferrite nanoparticles coated with rhodamine B isothiocyanate (MP@SiO 2(RITC)) were prepared and adsorbed on the GUV membrane. The MP@SiO 2(RITC) location and distribution on giant lipid vesicles were determined by 3D-CLSM projections, and their effect on the release properties and GUV permeability under a LF-AMF was investigated by CLSM time-resolved experiments. We show that the mechanism of release of the fluorescent dye during the LF-AMF exposure is induced by magnetic nanoparticle energy and mechanical vibration, which promote the perturbation of the GUV membrane without its collapse. © 2011 American Chemical Society.

  15. The influence of amphotericin B on the molecular organization and structural properties of DPPC lipid membranes modified by sterols

    Science.gov (United States)

    Kamiński, Daniel M.; Pociecha, Damian; Górecka, Ewa; Gagoś, Mariusz

    2015-02-01

    In this work, we studied the influence of the polyene antibiotic amphotericin B (AmB) on dipalmitoylphosphatidylcholine (DPPC) multibilayers modified by cholesterol and ergosterol investigated by means of X-ray diffraction. The periodic structures related to AmB-DPPC-sterol complexes in multibilayers are completely created in temperatures above the main lipid phase transition. The differences between all observed multilayer structures are related to the thickness. Multibilayers composed of lipid and sterols have similar thickness of 51 Å. Addition of amphotericin B leads to creation of new periodic structures. Multibilayers composed of lipid-ergosterol-AmB have thickness of 44 Å which does not change with temperature. Multibilayers composed of lipid-cholesterol-AmB at 20 °C are 43 Å and gets thicker at 50 °C. Most probably this is caused by weaker van der Vaals cholesterol-amphotericin B interactions.

  16. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).

    Science.gov (United States)

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen

    2016-01-21

    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  17. Improvement in physicochemical parameters of DPPC liposomes and increase in skin permeation of aciclovir and minoxidil by the addition of cationic polymers.

    Science.gov (United States)

    Hasanovic, Amra; Hollick, Caroline; Fischinger, Kerstin; Valenta, Claudia

    2010-06-01

    1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes were prepared by high-pressure homogeniser and coated with two cationic polymers, chitosan (CS) and for the first time Eudragit EPO (EU), respectively. Compared to the control liposomes, the polymeric liposomes showed greater physicochemical stability in terms of mean particle size and zeta potential at room temperature. In the present study, aciclovir and minoxidil have been used as hydrophilic and hydrophobic candidates. In the presence of the drugs, the polymeric liposomes still showed constant particle size and zeta potential. Influences of polymers and model drugs on thermotropic phase transition of DPPC liposomes were studied by micro-differential scanning calorimetry (microDSC). The influences on configuration of DPPC liposomes were investigated by Fourier transform infrared spectroscopy (FTIR). According to DSC results, cationic polymers had a stabilising effect, whereas aciclovir and minoxidil changed the physical properties of the DPPC bilayers by influencing the main phase transition temperature and erasing the pre-transition. The investigation of CO stretching bands of DPPC at 1736 cm(-1) in FTIR spectra showed that aciclovir has strong hydrogen bonding with CO groups of DPPC, whereas carbonyl groups were free in minoxidil presence. Moreover, the coating of liposomes with CS or EU led to higher skin diffusion for both drugs. This could be explained as an effect of positively charged liposomes to interact stronger with skin negatively charged surface and their possible interactions with structures below the stratum corneum. Copyright 2010 Elsevier B.V. All rights reserved.

  18. Synthesis and Crystal Structure of [CpRu(η5-C5H5)(dppc)Cl][PF6

    Institute of Scientific and Technical Information of China (English)

    WU Xiang-Hua; YU Guang-Ao; MENG Xiang-Gao; CHEN Yan; REN Yong; LIU Sheng-Hua

    2006-01-01

    The title complex [Ru(η5-C5H5)(dppc)Cl][PF6] has been synthesized by the reaction of [Ru(η5-C5H5)(PPh3)2Cl] with [dppc][PF6] (1,1'-bis(diphenylphosphino)cobaltocenium hexaflurophospate) in CH2Cl2, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21/n with a = 15.754(8), b =13.704(7), c=19.120(10) (A),β=106.148(9)°, V=3965(4) (A)3, Z=4, C40H35Cl3CoF6P3Ru, Mr=988.94, Dc=1.657 g/cm3, F(000) = 1984 and μ(MoKα) = 1.181 mm-1. The final R = 0.0425 and wR = 0.1001 for 7002 independent reflections. The title complex shows a mononuclear Ru(Ⅱ)capped by an η5-Cp ring, a chelating η2-dppc and a terminal chloride to assume a three-legged piano-stool configuration.

  19. Two-component Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H9OH).

    Science.gov (United States)

    Nakahara, Hiromichi; Hirano, Chikayo; Shibata, Osamu

    2013-01-01

    The interaction of (perfluorooctyl)nonanol (F8H9OH) with dipalmitoylphosphatidylcholine (DPPC) was systematically studied in two-component monolayers at air-water interface. The thermodynamic property and phase morphology of the monolayers were investigated by isotherm measurements and several microscopic methods such as Brewster angle microscopy, fluorescence microscopy, and atomic force microscopy (AFM). The AFM topographies for Langmuir-Blodgett films of F8H9OH exhibit the formation of monodispersed surface micelles. In the two-component system, the incorporation of F8H9OH induces condensation (or solidification) of DPPC monolayers. The excess Gibbs free energy and interaction parameter (or energy) of the two components were calculated from the isotherm data. Both the phase transition pressure for the coexistence of ordered and disordered phases and collapse pressure of monolayers vary with the mole fraction of F8H9OH, indicating binary miscibility between F8H9OH and DPPC within a monolayer state. The miscibility is also confirmed visually by in situ and ex situ microscopy at micro- and nanometer scales.

  20. Phase equilibria in DOPC/DPPC: Conversion from gel to subgel in two component mixtures.

    Science.gov (United States)

    Schmidt, Miranda L; Ziani, Latifa; Boudreau, Michelle; Davis, James H

    2009-11-07

    Biological membranes contain a mixture of phospholipids with varying degrees of hydrocarbon chain unsaturation. Mixtures of long chain saturated and unsaturated lipids with cholesterol have attracted a lot of attention because of the formation of two coexisting fluid bilayer phases in such systems over a broad range of temperature and composition. Interpretation of the phase behavior of such ternary mixtures must be based on a thorough understanding of the phase behavior of the binary mixtures formed with the same components. This article describes the phase behavior of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 1,2-di-d(31)-palmitoyl-sn-glycero-3-phosphocholine (DPPC) between -20 and 50 degrees C. Particular attention has been paid to the phase coexistence below about 16 degrees C where the subgel phase appears. The changes in the shape of the spectrum (and its spectral moments) during the slow transformation process leads to the conclusion that below 16 degrees C the gel phase is metastable and the gel component of the two-phase mixture slowly transforms to the subgel phase with a slightly different composition. This results in a line of three-phase coexistence near 16 degrees C. Analysis of the transformation of the metastable gel domains into the subgel phase using the nucleation and growth model shows that the subgel domain growth is a two dimensional process.

  1. Interaction of Phenylalanine with DPPC Model Membranes: More Than a Hydrophobic Interaction.

    Science.gov (United States)

    Rosa, A S; Cutro, A C; Frías, M A; Disalvo, E A

    2015-12-31

    The negative free energy previously reported is explained by the stabilization of a PC-Phe (phosphocholine-phenylalanine) complex in the presence of water shown by the decrease in the symmetric stretching frequency of the phosphate group of the lipid (PO2(-)). An entropic contribution due to the disruption of the water network around the phenyl and in the membrane defect may be invoked. The dipole potential decrease is explained by the orientation of the carboxylate opposing to the CO of the lipids with oxygen moiety toward the low hydrated hydrocarbon core. The symmetric bending frequency of NH3(+) group of Phe, decreases in 5.2 cm(-1) in relation to water congruent with zeta potential shift to positive values. The Phe to DPPC dissociation constant is Kd = 2.23 ± 0.09 mM, from which the free energy change is about -4.54 kcal/mol at 25 °C. This may be due to hydrophobic contributions and two hydrogen bonds.

  2. Osmotic Gradients Induce Bio-reminiscent Morphological Transformations in Giant Unilamellar Vesicles

    Directory of Open Access Journals (Sweden)

    Kamila eOglecka

    2012-05-01

    Full Text Available We report observations of large-scale, in-plane and out-of-plane membrane deformations in giant uni- and multilamellar vesicles composed of binary and ternary lipid mixtures in the presence of net transvesicular osmotic gradients. The lipid mixtures we examined consisted of binary mixtures of DOPC and DPPC lipids and ternary mixtures comprising POPC, sphingomyelin, and cholesterol over a range of compositions – both of which produce co-existing phases for selected ranges of compositions at room temperature under thermodynamic equilibrium. In the presence of net osmotic gradient, we find that the in-plane phase separation potential of these mixtures is non-trivially altered and a variety of out-of-plane morphological remodeling occurs. The repertoire of membrane deformations we observe display striking resemblance to their biological counterparts in live cells encompassing vesiculation, membrane fission and fusion, tubulation and pearling, as well as expulsion of entrapped vesicles from multicompartmental GUV architectures through large, self-healing transient pores. These observations suggest that the forces introduced by simple osmotic gradients across membrane boundaries could act as a trigger for shape-dependent membrane and vesicle trafficking activities. We speculate that such coupling of osmotic gradients with membrane properties might have provided lipid-mediated mechanisms during the early evolution of membrane compartmentalization in the absence of osmoregulatory protein machinery.

  3. Optimization of the Electroformation of Giant Unilamellar Vesicles (GUVs) with Unsaturated Phospholipids.

    Science.gov (United States)

    Breton, Marie; Amirkavei, Mooud; Mir, Lluis M

    2015-10-01

    Giant unilamellar vesicles (GUV) are widely used cell membrane models. GUVs have a cell-like diameter and contain the same phospholipids that constitute cell membranes. The most frequently used protocol to obtain these vesicles is termed electroformation, since key steps of this protocol consist in the application of an electric field to a phospholipid deposit. The potential oxidation of unsaturated phospholipids due to the application of an electric field has not yet been considered even though the presence of oxidized lipids in the membrane of GUVs could impact their permeability and their mechanical properties. Thanks to mass spectrometry analyses, we demonstrated that the electroformation technique can cause the oxidation of polyunsaturated phospholipids constituting the vesicles. Then, using flow cytometry, we showed that the amplitude and the duration of the electric field impact the number and the size of the vesicles. According to our results, the oxidation level of the phospholipids increases with their level of unsaturation as well as with the amplitude and the duration of the electric field. However, when the level of lipid oxidation exceeds 25 %, the diameter of the vesicles is decreased and when the level of lipid oxidation reaches 40 %, the vesicles burst or reorganize and their rate of production is reduced. In conclusion, the classical electroformation method should always be optimized, as a function of the phospholipid used, especially for producing giant liposomes of polyunsaturated phospholipids to be used as a cell membrane model.

  4. Direct visualization of solid ordered domains induced by polyene antibiotics in giant unilamellar vesicles.

    Science.gov (United States)

    Chulkov, Evgeny G; Efimova, Svetlana S; Schagina, Ludmila V; Ostroumova, Olga S

    2014-10-01

    Polyene antibiotics isolated from Streptomyces are frequently used in treatment of mycoses. Confocal fluorescence microscopy has been employed to investigate the influence of polyene macrolide antibiotics nystatin, amphotericin B, and filipin on the phase separation in giant unilamellar vesicles. It has been demonstrated that nystatin produced the solid ordered domains in vesicles made from DOPC/Chol, DOPC/Chol/SM, and POPC while DOPC vesicles remained homogenous in the presence of polyene antibiotics. The ability of various polyenes to produce the solid ordered phase in POPC membranes has been compared. It has been shown that amphotericin B produced phase separation at lower concentration as compared with nystatin and filipin. Filipin was less effective in promotion of gel domains. The observed efficiency of polyene antibiotics to induce phase separation in lipid bilayers correlates with their biological activity. Present findings probably indicate the limitations of using of polyenes as fluorescence membrane probes for determination of strerol-enriched domains in plasma membrane of live cells.

  5. Synthesis of Giant Unilamellar Vesicles (GUV) from Liposomes Prepared by the Rapid Solvent Exchange (RSE) Method

    Science.gov (United States)

    Baykal-Caglar, Eda

    2010-10-01

    Lipid bilayers, which is an important constituent of cell membranes, has been extensively studied by biophysicists. Cell membranes perform many vital cell functions such as signal transduction and transportation of materials needed for the functioning of the cell organelles. Understanding the organization and dynamics of lipid bilayers is important for understanding the processes taking place in cell membranes. Giant Unilamellar Vesicles (GUVs) are cell-sized model systems that allow direct visualization of membrane-related phenomena using fluorescence microscopy. In this study, we investigated the synthesis of GUVs from much smaller liposomes (less than 0.5 microns) produced by the Rapid Solvent Exchange (RSE) method in aqueous solutions of high and low ionic strength. The GUVs synthesized using RSE liposomes are more uniform in lipid composition than that synthesized by other methods. We made a number of modifications to the original electroformation method, and we are able to prepare GUVs from RSE liposomes both in high ionic strength and low ionic strength buffers. Using our optimized procedure, we are also able to produce high quality multi-component GUVs to study the dynamics of lipid domains.

  6. The dynamics of giant unilamellar vesicle oxidation probed by morphological transitions.

    Science.gov (United States)

    Sankhagowit, Shalene; Wu, Shao-Hua; Biswas, Roshni; Riche, Carson T; Povinelli, Michelle L; Malmstadt, Noah

    2014-10-01

    We have studied the dynamics of Lissamine Rhodamine B dye sensitization-induced oxidation of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs), where the progression of the underlying chemical processes was followed via vesicle membrane area changes. The surface-area-to-volume ratio of our spherical GUVs increased after as little as ten seconds of irradiation. The membrane area expansion was coupled with high amplitude fluctuations not typical of GUVs in isoosmotic conditions. To accurately measure the area of deformed and fluctuating membranes, we utilized a dual-beam optical trap (DBOT) to stretch GUV membranes into a geometrically regular shape. Further oxidation led to vesicle contraction, and the GUVs became tense, with micron-scale pores forming in the bilayer. We analyzed the GUV morphological behaviors as two consecutive rate-limiting steps. We also considered the effects of altering DOPC and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (RhDPPE) concentrations. The resulting kinetic model allows us to measure how lipid molecular area changes during oxidation, as well as to determine the rate constants controlling how quickly oxidation products are formed. Controlled membrane oxidation leading to permeabilization is also a potential tool for drug delivery based on engineered photosensitizer-containing lipid vesicles. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Fluorescence depolarization analysis of thermal phase transition in DPPC and DMPG aqueous dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Amando Siuiti, E-mail: amandosi@ffclrp.usp.br; Rodrigues, Ana Paula; Moreira Pazin, Wallance; Berardi Barioni, Marina

    2015-02-15

    We performed an overall analysis of steady state, kinetic and dynamical parameters of phospholipids labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD), to investigate the structural changes accompanying the phase transition of dimyristoyl phosphatidylglycerol (DMPG) vesicles, under low and high ionic strength conditions. For comparison, we also performed experiments on dimyristoyl phosphatidylcholine (DPPC) vesicles, which exhibit a well-defined thermal phase transition. Fluorescence parameters alone (lifetime, pre-exponential factor, rotational correlation times, and initial anisotropy) do not describe the thermal behavior of the vesicles. Combination of intensity decay and anisotropy decay data allows the calculation of mean anisotropy values, and among the several parameters obtained from time-resolved measurements, the main contribution to the mean anisotropy comes from the residual anisotropy, obtained as the limit value at long times. The results of calculations were comparable to the steady state measurements, and allowed the observation of the dependence between the thermal phase transition in DMPG and the ionic strength of the medium. The presence of NaCl affects the lipid packing leading to structural constraints onto the probes that are systematically higher than those observed in low ionic strength. In low ionic strength the long rotational correlation time of the NBD-PE (NBD-phosphatidylethanolamine) probe presents peculiar behavior, showing transient changes along the broad gel–fluid transition, that occurs parallel to the modifications in the scattering intensity. - Highlights: • Time-resolved data were combined to calculate mean values of fluorescence anisotropy. • Fluorescence structural parameters describe lipid vesicles thermal phase transition. • Calculated fluorescence anisotropy describes ionic strength effects in DMPG bilayers.

  8. Visualization of SNARE-Mediated Hemifusion between Giant Unilamellar Vesicles Arrested by Myricetin

    Science.gov (United States)

    Heo, Paul; Park, Joon-Bum; Shin, Yeon-Kyun; Kweon, Dae-Hyuk

    2017-01-01

    Neurotransmitters are released within a millisecond after Ca2+ arrives at an active zone. However, the vesicle fusion pathway underlying this synchronous release is yet to be understood. At the center of controversy is whether hemifusion, in which outer leaflets are merged while inner leaflets are still separated, is an on-pathway or off-pathway product of Ca2+-triggered exocytosis. Using the single vesicle fusion assay, we recently demonstrated that hemifusion is an on-pathway intermediate that immediately proceeds to full fusion upon Ca2+ triggering. It has been shown that the flavonoid myricetin arrests soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE)-mediated vesicle fusion at hemifusion, but that the hemifused vesicles spontaneously convert to full fusion when the myricetin clamp is removed by the enzyme laccase. In the present study, we visualized SNARE-mediated hemifusion between two SNARE-reconstituted giant unilamellar vesicles (GUVs) arrested by myricetin. The large size of the GUVs enabled us to directly image the hemifusion between them. When two merging GUVs were labeled with different fluorescent dyes, GUV pairs showed asymmetric fluorescence intensities depending on the position on the GUV pair consistent with what is expected for hemifusion. The flow of lipids from one vesicle to the other was revealed with fluorescence recovery after photobleaching (FRAP), indicating that the two membranes had hemifused. These results support the hypothesis that hemifusion may be the molecular status that primes Ca2+-triggered millisecond exocytosis. This study represents the first imaging of SNARE-driven hemifusion between GUVs. PMID:28408867

  9. Probing lipid-cholesterol interactions in DOPC/eSM/Chol and DOPC/DPPC/Chol model lipid rafts with DSC and (13)C solid-state NMR.

    Science.gov (United States)

    Fritzsching, Keith J; Kim, Jihyun; Holland, Gregory P

    2013-08-01

    The interaction between cholesterol (Chol) and phospholipids in bilayers was investigated for the ternary model lipid rafts, DOPC/eSM/Chol and DOPC/DPPC/Chol, with differential scanning calorimetry (DSC) and (13)C cross polarization magic angle spinning (CP-MAS) solid-state NMR. The enthalpy and transition temperature (Tm) of the Lα liquid crystalline phase transition from DSC was used to probe the thermodynamics of the different lipids in the two systems as a function of Chol content. The main chain (13)C (CH2)n resonance is resolved in the (13)C CP-MAS NMR spectra for the unsaturated (DOPC) and saturated (eSM or DPPC) chain lipid in the ternary lipid raft mixtures. The (13)C chemical shift of this resonance can be used to detect differences in chain ordering and overall interactions with Chol for the different lipid constituents in the ternary systems. The combination of DSC and (13)C CP-MAS NMR results indicate that there is a preferential interaction between SM and Chol below Tm for the DOPC/eSM/Chol system when the Chol content is ≤20mol%. In contrast, no preferential interaction between Chol and DPPC is observed in the DOPC/DPPC/Chol system above or below Tm. Finally, (13)C CP-MAS NMR resolves two Chol environments in the DOPC/eSM/Chol system below Tm at Chol contents >20mol% while, a single Chol environment is observed for DOPC/DPPC/Chol at all compositions.

  10. Differential Effects of Cholesterol, Ergosterol and Lanosterol on a Dipalmitoyl Phosphatidylcholine (DPPC) membrane: A Molecular Dynamics Simulations Study

    Energy Technology Data Exchange (ETDEWEB)

    Cournia, Zoe [Yale University; Ullmann, G. Matthias [University of Bayreuth; Smith, Jeremy C [ORNL

    2007-02-01

    Lipid raft/domain formation may arise as a result of the effects of specific sterols on the physical properties of membranes. Here, using molecular dynamics simulation, we examine the effects of three closely-related sterols, ergosterol, cholesterol, and lanosterol, at a biologically relevant concentration (40 mol %) on the structural properties of a model dipalmitoyl phosphatidylcholine (DPPC) membrane at 309 and 323 K. All three sterols are found to order the DPPC acyl tails and condense the membrane relative to the DPPC liquid-phase membrane, but each one does this to a significantly different degree. The smooth {alpha}-face of ergosterol, together with the presence of tail unsaturation in this sterol, leads to closer interaction of ergosterol with the lipids and closer packing of the lipids with each other, so ergosterol has a higher condensing effect on the membrane, as reflected by the area per lipid. Moreover, ergosterol induces a higher proportion of trans lipid conformers, a thicker membrane, and higher lipid order parameters and is aligned more closely with the membrane normal. Ergosterol also positions itself closer to the bilayer/water interface. In contrast, the rough {alpha}-face of lanosterol leads to a less close interaction of the steroid ring system with the phospholipid acyl chains, and so lanosterol orders, straightens, and packs the lipid acyl chains less well and is less closely aligned with the membrane normal. Furthermore, lanosterol lies closer to the relatively disordered membrane center than do the other sterols. The behavior of cholesterol in all the above respects is intermediate between that of lanosterol and ergosterol. The findings here may explain why ergosterol is the most efficient of the three sterols at promoting the liquid-ordered phase and lipid domain formation and may also furnish part of the explanation as to why cholesterol is evolutionarily preferred over lanosterol in higher-vertebrate plasma membranes.

  11. Lipid domains in giant unilamellar vesicles and their correspondence with equilibrium thermodynamic phases: A quantitative fluorescence microscopy imaging approach

    DEFF Research Database (Denmark)

    Fidorra, Matthias; Garcia, Alejandra; Ipsen, John Hjort

    2009-01-01

    membrane domains correspond to equilibrium thermodynamic phases (i.e., solid ordered and liquid disordered phases). In addition, the fact that the lever rule is validated from 11 to 14 randomly selected GUVs per molar fraction indicates homogeneity in the lipid composition among the explored GUV...... lipid phase diagram's tie lines and to test whether or not the coexistence of lipid domains in GUVs correspond to equilibrium thermodynamic phases. The analysis was applied to DLPC/DPPC GUVs displaying coexistence of lipid domains. Our results confirm the lever rule, demonstrating that the observed...... populations. In conclusion, our study shows that GUVs are reliable model systems to perform equilibrium thermodynamic studies of membranes....

  12. Molecular dynamics simulations of lipid vesicle fusion in atomic detail

    NARCIS (Netherlands)

    Knecht, Volker; Marrink, Siewert-Jan

    The fusion of a membrane-bounded vesicle with a target membrane is a key step in intracellular trafficking, exocytosis, and drug delivery. Molecular dynamics simulations have been used to study the fusion of small unilamellar vesicles composed of a dipalmitoyl-phosphatidylcholine (DPPC)/palmitic

  13. Mechanisms of Action of (Methacrylates in Hemolytic Activity, in Vivo Toxicity and Dipalmitoylphosphatidylcholine (DPPC Liposomes Determined Using NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Seiichiro Fujisawa

    2012-01-01

    Full Text Available We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H50 or in vivo mouse intraperitoneal (ip LD50 using reported data for α,β-unsaturated carbonyl compounds such as (methacrylate monomers and their 13C-NMR β-carbon chemical shift (δ. The log 1/H50 value for methacrylates was linearly correlated with the δCβ value. That for (methacrylates was linearly correlated with log P, an index of lipophilicity. The ipLD50 for (methacrylates was linearly correlated with δCβ but not with log P. For (methacrylates, the δCβ value, which is dependent on the π-electron density on the β-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω, whereas log P was linearly correlated with heat of formation (HF. Also, the interaction between (methacrylates and DPPC liposomes in cell membrane molecular models was investigated using 1H-NMR spectroscopy and differential scanning calorimetry (DSC. The log 1/H50 value was related to the difference in chemical shift (ΔδHa (Ha: H (trans attached to the β-carbon between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (methacrylates.

  14. Interfacial properties in Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H7OH).

    Science.gov (United States)

    Nakahara, Hiromichi; Hirano, Chikayo; Fujita, Ichiro; Shibata, Osamu

    2013-01-01

    Two-component interactions between (perfluorooctyl) heptanol (F8H7OH) and dipalmitoylphosphatidylcholine (DPPC), which is a major component of pulmonary surfactants in mammals, were systematically elucidated using Langmuir monolayers and Langmuir-Blodgett (LB) films of the compounds. The interactions such as the miscibility of the compounds and their phase behavior were examined from thermodynamic and morphological perspectives. The surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of the binary monolayers containing F8H7OH in different mole fractions (XF8H7OH) were measured simultaneously. The excess Gibbs free energy of mixing of the two components was calculated from the π-A isotherms. The resulting isotherm data were employed to construct a two-dimensional (2D) phase diagram of the system. The phase diagram revealed that the transition pressure as well as the monolayer collapse pressure change with changes in XF8H7OH. These thermodynamic analyses suggested that the miscibility of the two components and the solidification of DPPC monolayers can be induced by the addition of F8H7OH. The phase behavior upon monolayer compression was observed morphologically in situ using Brewster angle microscopy (BAM) and fluorescence microscopy (FM), as well as ex situ using atomic force microscopy (AFM). Interestingly, the AFM-based analysis revealed the formation of monodispersed 2D micelles consisting of F8H7OH at low surface pressures.

  15. Visualization of lipid domains in giant unilamellar vesicles using an environment-sensitive membrane probe based on 3-hydroxyflavone.

    Science.gov (United States)

    Klymchenko, Andrey S; Oncul, Sule; Didier, Pascal; Schaub, Emmanuel; Bagatolli, Luis; Duportail, Guy; Mély, Yves

    2009-02-01

    We characterized the recently introduced environment-sensitive fluorescent membrane probe based on 3-hydroxyflavone, F2N12S, in model lipid membranes displaying liquid disordered (Ld) phase, liquid ordered (Lo) phase, or their coexistence. Steady-state fluorescence studies in large unilamellar vesicles show that the probe dual emission drastically changes with the lipid bilayer phase, which can be correlated with the difference in their hydration. Using two-photon excitation microscopy on giant unilamellar vesicles, the F2N12S probe was found to bind both Ld and Lo phases, allowing visualization of the individual phases from the fluorescence intensity ratio of its two emission bands. By using a linearly polarized excitation light, a strong photoselection was observed for F2N12S in the Lo phase, indicating that its fluorophore is nearly parallel to the lipid chains of the bilayer. In contrast, the absence of the photoselection with the Ld phase indicated no predominant orientation of the probe in the Ld phase. Comparison of the present results with those reported previously for F2N12S in living cells suggests a high content of the Lo phase in the outer leaflet of the cell plasma membranes. Taking into account the high selectivity of F2N12S for the cell plasma membranes and its suitability for both single- and two-photon excitation, applications of this probe to study membrane lateral heterogeneity in biological membranes are foreseen.

  16. Monolayer compression induces fluidization in binary system of partially fluorinated alcohol (F4H11OH) with DPPC.

    Science.gov (United States)

    Nakahara, Hiromichi; Ohmine, Aya; Kai, Shoko; Shibata, Osamu

    2013-01-01

    A two-component Langmuir monolayer consisting of (perfluorobutyl)undecanol (F4H11OH) and dipalmitoylphosphatidylcholine (DPPC), a major component of pulmonary surfactants in mammals, has been investigated at the air-water interface. The binary monolayer has been systematically examined from both thermodynamic and morphological perspectives. The excess Gibbs free energy of mixing has been calculated from surface pressure (π)-molecular area (A) isotherms, and the results indicate that the miscibility of the two-component system shows a maximum in thermodynamical stability when the mole fraction (X(F4H11OH)) is 0.3. Results from a two-dimensional phase diagram (π vs. X(F4H11OH)) are consistent with these findings and depict the degree of miscibility resulting from the variation in the transition and collapse pressures relative to the concentration of X(F4H11OH). The miscibility is also supported by in situ Brewster angle microscopy and fluorescence microscopy, as well as ex situ atomic force microscopy for the system after transfer onto a mica substrate. Aside from temperature, a known driving force for the fluidization of DPPC monolayers is a change in surface composition caused by the addition of additive molecules. In the present study, however, the fluidization is driven by increasing surface pressures even at constant X(F4H11OH). Such a fluidization is a fascinating property when looked at in context of its potential implications for pulmonary replacement therapy, and hence, this study provides a fundamental insight into designing fluorinated materials for biomedical use.

  17. Dynamic molecular structure of DPPC-DLPC-cholesterol ternary lipid system by spin-label electron spin resonance.

    Science.gov (United States)

    Chiang, Yun-Wei; Shimoyama, Yuhei; Feigenson, Gerald W; Freed, Jack H

    2004-10-01

    The hydrated ternary lamellar lipid mixture of dipalmitoyl-PC/dilauroyl-PC/cholesterol (DPPC/DLPC/Chol) has been studied by electron spin resonance (ESR) to reveal the dynamic structure on a molecular level of the different phases that exist and coexist over virtually the full range of composition. The spectra for more than 100 different compositions at room temperature were analyzed by nonlinear least-squares fitting to provide the rotational diffusion rates and order parameters of the end-chain labeled phospholipid 16-PC. The ESR spectra exhibit substantial variation as a function of composition, even though the respective phases generally differ rather modestly from each other. The Lalpha and Lbeta phases are clearly distinguished, with the former exhibiting substantially lower ordering and greater motional rates, whereas the well-defined Lo phase exhibits the greatest ordering and relatively fast motional rates. Typically, smaller variations occur within a given phase. The ESR spectral analysis also yields phase boundaries and coexistence regions which are found to be consistent with previous results from fluorescence methods, although new features are found. Phase coexistence regions were in some cases confirmed by observing the existence of isosbestic points in the absorption mode ESR spectra from the phases. The dynamic structural properties of the DPPC-rich Lbeta and DLPC-rich Lalpha phases, within their two-phase coexistence region do not change with composition along a tie-line, but the ratio of the two phases follows the lever rule in accordance with thermodynamic principles. The analysis shows that 16-PC spin-label partitions nearly equally between the Lalpha and Lbeta phases, making it a useful probe for studying such coexisting phases. Extensive study of two-phase coexistence regions requires the determination of tie-lines, which were approximated in this study. However, a method is suggested to accurately determine the tie-lines by ESR.

  18. Destabilization and fusion of zwitterionic large unilamellar lipid vesicles induced by a beta-type structure of the HIV-1 fusion peptide

    NARCIS (Netherlands)

    Nieva, JL; Nir, S; Wilschut, J

    1998-01-01

    The peptide HIVarg, corresponding to a sequence of 23 amino acid residues at the N-terminus of HIV-1 gp41, has the capacity to induce fusion of large unilamellar vesicles (LUV) consisting of negatively charged or zwitterionic phospholipids. In the present study, we further characterize this destabil

  19. Influence of temperature, anions and size distribution on the zeta potential of DMPC, DPPC and DMPE lipid vesicles.

    Science.gov (United States)

    Morini, M A; Sierra, M B; Pedroni, V I; Alarcon, L M; Appignanesi, G A; Disalvo, E A

    2015-07-01

    The purpose of the work is to compare the influence of the multilamellarity, phase state, lipid head groups and ionic media on the origin of the surface potential of lipid membranes. With this aim, we present a new analysis of the zeta potential of multilamellar and unilamellar vesicles composed by phosphatidylcholines (PC) and phosphatidylethanolamines (PE) dispersed in water and ionic solutions of polarizable anions, at temperatures below and above the phase transition. In general, the adsorption of anions seems to explain the origin of the zeta potential in vesicles only above the transition temperature (Tc). In this case, the sign of the surface potential is ascribed to a partial orientation of head group moiety toward the aqueous phase. This is noticeable in PC head groups but not in PEs, due to the strong lateral interaction between PO and NH group in PE.

  20. Molecular dynamics simulation of human serum paraoxonase 1 in DPPC bilayer reveals a critical role of transmembrane helix H1 for HDL association.

    Science.gov (United States)

    Patra, Mahesh Chandra; Rath, Surya Narayan; Pradhan, Sukanta Kumar; Maharana, Jitendra; De, Sachinandan

    2014-01-01

    Serum paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-bound mammalian enzyme exhibiting antiatherosclerotic activity. Despite years of research, an accurate model for the binding interaction between PON1 and HDL has not been established. However, it is reported that anchoring of PON1 to HDL is mainly governed by an N-terminal alpha helix H1 and another short helix H2. Here, we studied the molecular association of full-length human PON1 (huPON1) with a HDL-mimetic dipalmitoylphosphatidylcholine (DPPC) bilayer using homology modeling and molecular dynamics simulations. Our results indicate that H1 is the highly dynamic part of huPON1, showing clockwise rotation of up to 30° within the DPPC bilayer. However, without phospholipid molecules, H1 experiences helical distortions, illustrating an incompatible HDL-anchoring conformation. Snorkeling interactions of K3, R18, and R27 together with aromatic locks formed by Y187, Y190, W194, and W202 are highly essential for anchoring of huPON1 to HDL's surface. Molecular mechanics/Poisson-Boltzmann solvent-accessible surface area (MM/PBSA) binding free energy calculation revealed that H1 displays greater binding affinity towards lipid molecules compared with H2 and H3, suggesting that H1 is the most probable HDL-binding domain of PON1. Binding free energy decomposition showed that K3, R18, and R27 interact with polar headgroups of DPPC membrane through electrostatic interaction. Moreover, Y187, Y190, W194, and W202 interact with DPPC lipids mainly through van der Waals interaction. Taken together, these results show that the transmembrane helix H1 along with the interfacial positively charged and aromatic resides were crucial for PON1's association with HDL particle. The current study will be useful towards understanding the antiatherosclerotic and bioscavenging properties of this promiscuous enzyme.

  1. Visualization of lipid domains of lipid domains in giant unilamellar vesicles using an environment-sensitive membrane probe based on 3-hydroxyflavone

    DEFF Research Database (Denmark)

    Klymchenko, Andrey; Oncul, Sule; Didier, Pascal

    2009-01-01

    of the photoselection with the Ld phase indicated no predominant orientation of the probe in the Ld phase. Comparison of the present results with those reported previously for F2N12S in living cells suggests a high content of the Lo phase in the outer leaflet of the cell plasma membranes. Taking into account the high......We characterized the recently introduced environment-sensitive fluorescent membrane probe based on 3-hydroxyflavone, F2N12S, in model lipid membranes displaying liquid disordered (Ld) phase, liquid ordered (Lo) phase, or their coexistence. Steady-state fluorescence studies in large unilamellar...... vesicles show that the probe dual emission drastically changes with the lipid bilayer phase, which can be correlated with the difference in their hydration. Using two-photon excitation microscopy on giant unilamellar vesicles, the F2N12S probe was found to bind both Ld and Lo phases, allowing visualization...

  2. DPPC/poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) chimeric nanostructures as potential drug nanocarriers

    Energy Technology Data Exchange (ETDEWEB)

    Pippa, Natassa [Faculty of Pharmacy, National and Kapodistrian University of Athens, Department of Pharmaceutical Technology (Greece); Kaditi, Eleni; Pispas, Stergios [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation (Greece); Demetzos, Costas, E-mail: demetzos@pharm.uoa.gr [Faculty of Pharmacy, National and Kapodistrian University of Athens, Department of Pharmaceutical Technology (Greece)

    2013-06-15

    In this study, we report on the self assembly behavior and on stability studies of mixed (chimeric) nanosystems consisting of dipalmitoylphosphatidylcholine (DPPC) and poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) gradient copolymer in aqueous media and in fetal bovine serum (FBS). A gamut of light scattering techniques and fluorescence spectroscopy were used in order to extract information on the size and morphological characteristics of the nanoassemblies formed, as a function of gradient block copolymer content, as well as temperature. The hydrodynamic radii (R{sub h}) of nanoassemblies decreased in the process of heating up to 50 Degree-Sign C, while the fractal dimension (d{sub f}) values, also increased. Indomethacin was successfully incorporated into these chimeric nanocarriers. Drug release was depended on the components ratio. The present studies show that there are a number of parameters that can be used in order to alter the properties of chimeric nanosystems, and this is advantageous to the development of 'smart' nanocarriers for drug delivery.

  3. DPPC/poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) chimeric nanostructures as potential drug nanocarriers

    Science.gov (United States)

    Pippa, Natassa; Kaditi, Eleni; Pispas, Stergios; Demetzos, Costas

    2013-06-01

    In this study, we report on the self assembly behavior and on stability studies of mixed (chimeric) nanosystems consisting of dipalmitoylphosphatidylcholine (DPPC) and poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (MPOx) gradient copolymer in aqueous media and in fetal bovine serum (FBS). A gamut of light scattering techniques and fluorescence spectroscopy were used in order to extract information on the size and morphological characteristics of the nanoassemblies formed, as a function of gradient block copolymer content, as well as temperature. The hydrodynamic radii ( R h) of nanoassemblies decreased in the process of heating up to 50 °C, while the fractal dimension ( d f) values, also increased. Indomethacin was successfully incorporated into these chimeric nanocarriers. Drug release was depended on the components ratio. The present studies show that there are a number of parameters that can be used in order to alter the properties of chimeric nanosystems, and this is advantageous to the development of "smart" nanocarriers for drug delivery.

  4. Alternative methods of determining phase transition temperatures of phospholipids that constitute liposomes on the example of DPPC and DMPC

    Energy Technology Data Exchange (ETDEWEB)

    Pentak, Danuta, E-mail: danuta.pentak@us.edu.pl

    2014-05-01

    Highlights: • New phase transition for DMPC was found. • FT-IR method is an important addition to the DSC studies. • The proposed method for determining the T{sub C} give very consistent results. - Abstract: In this work, alternatives to differential scanning calorimetry (DSC) as a method of determining the main phospholipid phase transition temperature are presented. The bilayer phase transitions from the ripple gel phase (P{sub β{sup ′}}) to the liquid-crystal phase (L{sub α}) of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were studied by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) methods. In this work, two correlations between the DSC and FT-IR methods, and NMR and EPR methods are shown. The proposed methods allow for determining the T{sub C} temperature with a high degree of accuracy. Furthermore, a comparison of results obtained using the DSC and FT-IR methods allowed for an observation of a new DMPC phase transition. The liposomes analyzed in this work were obtained by the modified reverse-phase evaporation method (mREV)

  5. Dynamic molecular structure and phase diagram of DPPC-cholesterol binary mixtures: a 2D-ELDOR study.

    Science.gov (United States)

    Chiang, Yun-Wei; Costa-Filho, Antonio J; Freed, Jack H

    2007-09-27

    This paper is an application of 2D electron-electron double resonance (2D-ELDOR) with the "full Sc- method" to study model membranes. We obtain and confirm the phase diagram of 1,2-dipalmitoyl-sn-glycerophosphatidylcholine (DPPC)-cholesterol binary mixtures versus temperature and provide quantitative descriptions for its dynamic molecular structure using 2D-ELDOR at the Ku band. The spectra from the end-chain 16-PC spin label in multilamellar phospholipid vesicles are obtained for cholesterol molar concentrations ranging from 0 to 50% and from 25 to 60 degrees C. This phase diagram consists of liquid-ordered, liquid-disordered, and gel phases and phase coexistence regions. The phase diagram is carefully examined according to the spectroscopic evidence, and the rigorous interpretation for the line shape changes. We show that the 2D-ELDOR spectra differ markedly with variation in the composition. The extensive line shape changes in the 2D-plus-mixing-time representation provide useful information to define and characterize the membrane phases with respect to their dynamic molecular structures and to determine the phase boundaries. The homogeneous T2's are extracted from the pure absorption spectra and are used to further distinguish the membrane phases. These results show 2D-ELDOR to be naturally suitable for probing and reporting the dynamic structures of microdomains in model membrane systems and, moreover, providing a very detailed picture of their molecular dynamic structure, especially with the aid of the "full Sc- method".

  6. Membrane fusion of pH-sensitive liposomes – a quantitative study using giant unilamellar vesicles

    DEFF Research Database (Denmark)

    Trier, Sofie; Henriksen, Jonas Rosager; Andresen, Thomas Lars

    2011-01-01

    This article presents a methodology for developing small-signal behavioral electromagnetic (EM) models of p-i-n photodiodes (PDs) for high-speed applications. The EM model includes RC bandwidth limitation effect and transit-time effect. The model is capable of accurately modeling arbitrary comple...

  7. Counterions control whether self-assembly leads to formation of stable and well-defined unilamellar nanotubes or nanoribbons and nanorods

    DEFF Research Database (Denmark)

    Shi, Dong; Schwall, Christian; Sfintes, George

    2014-01-01

    Self-assembly of the amphiphilic π-conjugated carbenium ion ATOTA-1(+) in aqueous solution selectively leads to discrete and highly stable nanotubes or nanoribbons and nanorods, depending on the nature of the counterion (Cl(-) vs. PF6(-), respectively). The nanotubes formed by the Cl(-) salt...... illustrate an exceptional example of a structural well-defined (29±2 nm in outer diameter) unilamellar tubular morphology featuring π-conjugated functionality and high stability and flexibility, in aqueous solution....

  8. Design, characterization, and aerosolization of organic solution advanced spray-dried moxifloxacin and ofloxacin dipalmitoylphosphatidylcholine (DPPC microparticulate/nanoparticulate powders for pulmonary inhalation aerosol delivery

    Directory of Open Access Journals (Sweden)

    Duan J

    2013-09-01

    Full Text Available Jinghua Duan,1,2 Frederick G Vogt,3 Xiaojian Li,1 Don Hayes Jr,4,5 Heidi M Mansour6 1University of Kentucky College of Pharmacy, Department of Pharmaceutical Sciences – Drug Development Division, Lexington, KY, USA; 2University of Washington-Seattle, College of Pharmacy, Department of Pharmaceutics, Seattle, WA, USA; 3GlaxoSmithKline, Analytical Sciences, Product Development, King of Prussia, PA, USA; 4The Ohio State University College of Medicine, Departments of Pediatrics and Internal Medicine, Nationwide Children's Hospital Lung and Heart-Lung Transplant Programs, Columbus, OH, USA; 5The Ohio State University, Davis Heart and Lung Research Institute, Columbus, OH, USA; 6The University of Arizona–Tucson, College of Pharmacy, Skaggs Center of Pharmaceutical Sciences, Tucson, AZ, USA Abstract: The aim of this study was to design and develop respirable antibiotics moxifloxacin (MOXI hydrochloride and ofloxacin (OFLX microparticles and nanoparticles, and multifunctional antibiotics particles with or without lung surfactant 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced by advanced spray-drying particle engineering from an organic solution in closed mode (no water from dilute solution. Scanning electron microscopy indicated that these particles had both optimal particle morphology and surface morphology, and the particle size distributions were suitable for pulmonary delivery. Comprehensive and systematic physicochemical characterization and in vitro aerosol dispersion performance revealed significant differences between these two fluoroquinolone antibiotics following spray drying as drug aerosols and as cospray-dried antibiotic drug: DPPC aerosols. Fourier transform infrared spectroscopy and confocal Raman microspectroscopy were employed to probe composition and interactions in the solid state. Spray-dried MOXI was

  9. Interaction of sodium diclofenac with freeze-dried soya phosphatidylcholine and unilamellar liposomes Interação do diclofenaco com fosfatidilcolina de soja e lipossomas unilamelares liofilizados

    Directory of Open Access Journals (Sweden)

    Luciana Biagini Lopes

    2006-12-01

    Full Text Available Phospholipids are widely used as structural amphiphilic compounds in liposome formulations. In this study, we have analyzed the interaction the sodium diclofenac (SD with soya phosphaditylcholine (PC and soya phosphatidylcholine from lyophilized small unilamellar liposomes (SUV. The changes in the properties of the co-lyophilized drug/PC from SUV liposomes, lyophilized PC from SUV liposomes, and lyophilized soya phosphatidylcholine, were studied by Differential Scanning Calorimetry (DSC. The DSC data showed that the previous organization of phospholipids molecules to form liposome affects intensely the thermal behavior of PC when compared to non-lipossomal PC. SD modified the thermal properties of PC from liposomes. It was verified that SD affects intensely the located group peaks in the regions of 120-140 ºC and in the higher temperature region of 240-260 ºC. The results of this work demonstrated that the presence of the drug modified the DSC behavior for both liposomal and non-liposomal PC and that these modifications can be easily monitored by DSC analysis.Fosfolipídios são freqüentemente usados como compostos anfifílicos estruturais em formulações de lipossomas. Neste estudo foi analisada a interação do diclofenaco sódico (SD com a fosfatidilcolina de soja liofilizada e a fosfatidilcolina de soja (PC obtida de lipossomas unilamelares pequenos liofilizados (SUV. As modificações nas propriedades da mistura fármaco/PC co-liofilizados a partir de SUV pré-formados, lipossomas de PC vazios e PC liofilizada foram estudadas por Calorimetria Diferencial de Varredura (DSC. Os resultados de DSC mostraram que a organização prévia das moléculas PC para formar lipossomas interfere significativamente no perfil de DSC da PC, quando comparada ao perfil de DSC da PC não-lipossômica. Verificou-se que o SD afeta intensamente o grupo de picos situados nas regiões de 120-140ºC e na região de mais alta temperatura (240-260ºC. Os resultados

  10. Introducing micrometer-sized artificial objects into live cells: a method for cell-giant unilamellar vesicle electrofusion.

    Directory of Open Access Journals (Sweden)

    Akira C Saito

    Full Text Available Here, we report a method for introducing large objects of up to a micrometer in diameter into cultured mammalian cells by electrofusion of giant unilamellar vesicles. We prepared GUVs containing various artificial objects using a water-in-oil (w/o emulsion centrifugation method. GUVs and dispersed HeLa cells were exposed to an alternating current (AC field to induce a linear cell-GUV alignment, and then a direct current (DC pulse was applied to facilitate transient electrofusion. With uniformly sized fluorescent beads as size indexes, we successfully and efficiently introduced beads of 1 µm in diameter into living cells along with a plasmid mammalian expression vector. Our electrofusion did not affect cell viability. After the electrofusion, cells proliferated normally until confluence was reached, and the introduced fluorescent beads were inherited during cell division. Analysis by both confocal microscopy and flow cytometry supported these findings. As an alternative approach, we also introduced a designed nanostructure (DNA origami into live cells. The results we report here represent a milestone for designing artificial symbiosis of functionally active objects (such as micro-machines in living cells. Moreover, our technique can be used for drug delivery, tissue engineering, and cell manipulation.

  11. Encapsulation of Nucleic Acids into Giant Unilamellar Vesicles by Freeze-Thaw: a Way Protocells May Form

    Science.gov (United States)

    Qiao, Hai; Hu, Na; Bai, Jin; Ren, Lili; Liu, Qing; Fang, Liaoqiong; Wang, Zhibiao

    2016-11-01

    Protocells are believed to consist of a lipid membrane and encapsulated nucleic acid. As the lipid membrane is impermeable to macromolecules like nucleic acids, the processes by which nucleic acids become encapsulated inside lipid membrane compartments are still unknown. In this paper, a freeze-thaw method was modified and applied to giant unilamellar vesicles (GUVs) and deoxyribonucleic acid (DNA) in mixed solution resulting in the efficient encapsulation of 6.4 kb plasmid DNA and similar length linear DNA into GUVs. The mechanism of encapsulation was followed by observing the effect of freeze-thaw temperatures on GUV morphological change, DNA encapsulation and ice crystal formation, and analyzing their correlation. Following ice crystal formation, the shape of spherical GUVs was altered and membrane integrity was damaged and this was found to be a necessary condition for encapsulation. Heating alone had no effects on DNA encapsulation, but was helpful for restoring the spherical shape and membrane integrity of GUVs damaged during freezing. These results suggested that freeze-thaw could promote the encapsulation of DNA into GUVs by a mechanism: the vesicle membrane was breached by ice crystal formation during freezing, DNA entered into damaged GUVs through these membrane gaps and was encapsulated after the membrane was resealed during the thawing process. The process described herein therefore describes a simple way for the encapsulation of nucleic acids and potentially other macromolecules into lipid vesicles, a process by which early protocells might have formed.

  12. Precise detection of pH inside large unilamellar vesicles using membrane-impermeable dendritic porphyrin-based nanoprobes.

    Science.gov (United States)

    Leiding, Thom; Górecki, Kamil; Kjellman, Tomas; Vinogradov, Sergei A; Hägerhäll, Cecilia; Arsköld, Sindra Peterson

    2009-05-15

    Accurate real-time measurements of proton concentration gradients are pivotal to mechanistic studies of proton translocation by membrane-bound enzymes. Here we report a detailed characterization of the pH-sensitive fluorescent nanoprobe Glu(3), which is well suited for pH measurements in microcompartmentalized biological systems. The probe is a polyglutamic porphyrin dendrimer in which multiple carboxylate termini ensure its high water solubility and prevent its diffusion across phospholipid membranes. The probe's pK is in the physiological pH range, and its protonation can be followed ratiometrically by absorbance or fluorescence in the ultraviolet-visible spectral region. The usefulness of the probe was enhanced by using a semiautomatic titration system coupled to a charge-coupled device (CCD) spectrometer, enabling fast and accurate titrations and full spectral coverage of the system at millisecond time resolution. The probe's pK was measured in bulk solutions as well as inside large unilamellar vesicles in the presence of physiologically relevant ions. Glu(3) was found to be completely membrane impermeable, and its distinct spectroscopic features permit pH measurements inside closed membrane vesicles, enabling quantitative mechanistic studies of membrane-spanning proteins. Performance of the probe was demonstrated by monitoring the rate of proton leakage through the phospholipid bilayer in large vesicles with and without the uncoupler gramicidin present. Overall, as a probe for biological proton translocation measurements, Glu(3) was found to be superior to the commercially available pH indicators.

  13. The single-giant unilamellar vesicle method reveals lysenin-induced pore formation in lipid membranes containing sphingomyelin.

    Science.gov (United States)

    Alam, Jahangir Md; Kobayashi, Toshihide; Yamazaki, Masahito

    2012-06-26

    Lysenin is a sphingomyelin (SM)-binding pore-forming toxin. To reveal the interaction of lysenin with lipid membranes, we investigated lysenin-induced membrane permeation of a fluorescent probe, calcein, through dioleoylphosphatidylcholine(DOPC)/SM, DOPC/SM/cholesterol(chol), and SM/chol membranes, using the single-giant unilamellar vesicle (GUV) method. The results clearly show that lysenin formed pores in all the membranes, through which membrane permeation of calcein occurred without disruption of GUVs. The membrane permeation began stochastically, and the membrane permeability coefficient increased over time to reach a maximum, steady value, Ps, which persisted for a long time(100--500 s), indicating that the pore concentration increases over time and finally reaches its steady value, NP s . The Ps values increased as the SM/lysenin ratio decreased, and at low concentrations of lysenin, the Ps values of SM/DOPC/chol (42/30/28)GUVs were much larger than those of SM/DOPC (58/42) GUVs. The dependence of Ps on the SM/lysenin ratio for these membranes was almost the same as that of the fraction of sodium dodecyl sulfate (SDS)-resistant lysenin oligomers, indicating that NP s increases as the SDS-resistant oligomer fraction increases. On the other hand, lysenin formed pores in GUVs of SM/chol(60/40) membrane, which is in a homogeneous liquid-ordered phase, indicating that the phase boundary is not necessary for pore formation. The Ps values of SM/chol (60/40) GUVs were smaller than those of SM/DOPC/chol (42/30/28) GUVs even though the SDS-resistant oligomer fractions were similar for both membranes, suggesting that not all of the oligomers can convert into a pore. On the basis of these results, we discuss the elementary processes of lysenin-induced pore formation.

  14. Towards bio-silicon interfaces: formation of an ultra-thin self-hydrated artificial membrane composed of dipalmitoylphosphatidylcholine (DPPC) and chitosan deposited in high vacuum from the gas-phase.

    Science.gov (United States)

    Retamal, María J; Cisternas, Marcelo A; Gutierrez-Maldonado, Sebastian E; Perez-Acle, Tomas; Seifert, Birger; Busch, Mark; Huber, Patrick; Volkmann, Ulrich G

    2014-09-14

    The recent combination of nanoscale developments with biological molecules for biotechnological research has opened a wide field related to the area of biosensors. In the last years, device manufacturing for medical applications adapted the so-called bottom-up approach, from nanostructures to larger devices. Preparation and characterization of artificial biological membranes is a necessary step for the formation of nano-devices or sensors. In this paper, we describe the formation and characterization of a phospholipid bilayer (dipalmitoylphosphatidylcholine, DPPC) on a mattress of a polysaccharide (Chitosan) that keeps the membrane hydrated. The deposition of Chitosan (~25 Å) and DPPC (~60 Å) was performed from the gas phase in high vacuum onto a substrate of Si(100) covered with its native oxide layer. The layer thickness was controlled in situ using Very High Resolution Ellipsometry (VHRE). Raman spectroscopy studies show that neither Chitosan nor DPPC molecules decompose during evaporation. With VHRE and Atomic Force Microscopy we have been able to detect phase transitions in the membrane. The presence of the Chitosan interlayer as a water reservoir is essential for both DPPC bilayer formation and stability, favoring the appearance of phase transitions. Our experiments show that the proposed sample preparation from the gas phase is reproducible and provides a natural environment for the DPPC bilayer. In future work, different Chitosan thicknesses should be studied to achieve a complete and homogeneous interlayer.

  15. Towards bio-silicon interfaces: Formation of an ultra-thin self-hydrated artificial membrane composed of dipalmitoylphosphatidylcholine (DPPC) and chitosan deposited in high vacuum from the gas-phase

    Energy Technology Data Exchange (ETDEWEB)

    Retamal, María J., E-mail: moretama@uc.cl; Cisternas, Marcelo A.; Seifert, Birger; Volkmann, Ulrich G. [Instituto de Física, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, 7820436 Santiago (Chile); Centro de Investigación en Nanotecnología y Materiales Avanzados (CIEN-UC), Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, 7820436 Santiago (Chile); Gutierrez-Maldonado, Sebastian E.; Perez-Acle, Tomas [Computational Biology Lab (DLab), Fundación Ciencia y Vida, Av. Zañartu 1482, Santiago (Chile); Centro Interdisciplinario de Neurociencias de Valparaiso (CINV), Universidad de Valparaiso, Pasaje Harrington 287, Valparaiso (Chile); Busch, Mark; Huber, Patrick [Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg (Germany)

    2014-09-14

    The recent combination of nanoscale developments with biological molecules for biotechnological research has opened a wide field related to the area of biosensors. In the last years, device manufacturing for medical applications adapted the so-called bottom-up approach, from nanostructures to larger devices. Preparation and characterization of artificial biological membranes is a necessary step for the formation of nano-devices or sensors. In this paper, we describe the formation and characterization of a phospholipid bilayer (dipalmitoylphosphatidylcholine, DPPC) on a mattress of a polysaccharide (Chitosan) that keeps the membrane hydrated. The deposition of Chitosan (∼25 Å) and DPPC (∼60 Å) was performed from the gas phase in high vacuum onto a substrate of Si(100) covered with its native oxide layer. The layer thickness was controlled in situ using Very High Resolution Ellipsometry (VHRE). Raman spectroscopy studies show that neither Chitosan nor DPPC molecules decompose during evaporation. With VHRE and Atomic Force Microscopy we have been able to detect phase transitions in the membrane. The presence of the Chitosan interlayer as a water reservoir is essential for both DPPC bilayer formation and stability, favoring the appearance of phase transitions. Our experiments show that the proposed sample preparation from the gas phase is reproducible and provides a natural environment for the DPPC bilayer. In future work, different Chitosan thicknesses should be studied to achieve a complete and homogeneous interlayer.

  16. Towards bio-silicon interfaces: Formation of an ultra-thin self-hydrated artificial membrane composed of dipalmitoylphosphatidylcholine (DPPC) and chitosan deposited in high vacuum from the gas-phase

    Science.gov (United States)

    Retamal, María J.; Cisternas, Marcelo A.; Gutierrez-Maldonado, Sebastian E.; Perez-Acle, Tomas; Seifert, Birger; Busch, Mark; Huber, Patrick; Volkmann, Ulrich G.

    2014-09-01

    The recent combination of nanoscale developments with biological molecules for biotechnological research has opened a wide field related to the area of biosensors. In the last years, device manufacturing for medical applications adapted the so-called bottom-up approach, from nanostructures to larger devices. Preparation and characterization of artificial biological membranes is a necessary step for the formation of nano-devices or sensors. In this paper, we describe the formation and characterization of a phospholipid bilayer (dipalmitoylphosphatidylcholine, DPPC) on a mattress of a polysaccharide (Chitosan) that keeps the membrane hydrated. The deposition of Chitosan (˜25 Å) and DPPC (˜60 Å) was performed from the gas phase in high vacuum onto a substrate of Si(100) covered with its native oxide layer. The layer thickness was controlled in situ using Very High Resolution Ellipsometry (VHRE). Raman spectroscopy studies show that neither Chitosan nor DPPC molecules decompose during evaporation. With VHRE and Atomic Force Microscopy we have been able to detect phase transitions in the membrane. The presence of the Chitosan interlayer as a water reservoir is essential for both DPPC bilayer formation and stability, favoring the appearance of phase transitions. Our experiments show that the proposed sample preparation from the gas phase is reproducible and provides a natural environment for the DPPC bilayer. In future work, different Chitosan thicknesses should be studied to achieve a complete and homogeneous interlayer.

  17. PLGA/DPPC/trimethylchitosan spray-dried microparticles for the nasal delivery of ropinirole hydrochloride: in vitro, ex vivo and cytocompatibility assessment

    Energy Technology Data Exchange (ETDEWEB)

    Karavasili, Christina [Laboratory of Pharmaceutical Technology, Department of Pharmacy, Aristotle University of Thessaloniki, 54124 (Greece); Bouropoulos, Nikolaos [Department of Materials Science, University of Patras, 26504 Rio, Patras (Greece); Foundation for Research and Technology, Hellas-Institute of Chemical Engineering and High Temperature, P.O. Box 1414, 26504 Patras (Greece); Sygellou, Lamprini [Foundation for Research and Technology, Hellas-Institute of Chemical Engineering and High Temperature, P.O. Box 1414, 26504 Patras (Greece); Amanatiadou, Elsa P.; Vizirianakis, Ioannis S. [Laboratory of Pharmacology, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Fatouros, Dimitrios G., E-mail: dfatouro@pharm.auth.gr [Laboratory of Pharmaceutical Technology, Department of Pharmacy, Aristotle University of Thessaloniki, 54124 (Greece)

    2016-02-01

    In the present study we investigated polymer-lipid microparticles loaded with ropinirole hydrochloride (RH) for nasal delivery. RH microparticles were further evaluated by means of scanning electron microscopy (SEM), ζ-potential measurements, Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD). In vitro release studies were performed in simulated nasal electrolyte solution (SNES) pH 5.5 at 35 °C. Ex vivo permeation studies were conducted across sheep nasal mucosa. Cytocompatibility was tested in cultured human airway epithelial cells (Calu-3). SEM studies revealed spheroid microparticles in the range of 2.09 μm to 2.41 μm. The presence of trimethylchitosan (TMC) induced a slight shift towards less negative ζ-potential values. Surface chemistry (XPS) revealed the presence of dipalmitoylphospatidylcholine (DPPC) and poly(lactic-co-glycolic acid) (PLGA) onto microparticles' surface, further corroborating the FT-IR and XRD findings. In vitro release studies showed that the microparticle composition can partly modulate the release of RH. Ex vivo studies demonstrated a 2.35-folded enhancement of RH permeation when RH was co-formulated with TMC of low molecular weight, compared to the control. All formulations tested were found to be non-toxic to cells. The results suggest that polymer-lipid microparticles may be a promising carrier for the nasal delivery of RH. - Highlights: • Development of microparticles comprising PLGA/DPPC/TMC for nasal drug delivery. • Physicochemical characterization showed that DPPC dominated microparticles' surface. • Microparticles enhanced permeation of ropinirole across sheep nasal epithelium. • The cytotoxicity assay with Calu-3 cells demonstrated satisfactory cell viability.

  18. Comparison of sorafenib-loaded poly (lactic/glycolic) acid and DPPC liposome nanoparticles in the in vitro treatment of renal cell carcinoma.

    Science.gov (United States)

    Liu, James; Boonkaew, Benjawan; Arora, Jaspreet; Mandava, Sree Harsha; Maddox, Michael M; Chava, Srinivas; Callaghan, Cameron; He, Jibao; Dash, Srikanta; John, Vijay T; Lee, Benjamin R

    2015-03-01

    The objective of this study is to develop and compare several Sorafenib-loaded biocompatible nanoparticle models in order to optimize drug delivery and tumor cellular kill thereby improving the quality of Sorafenib-regimented chemotherapy. Sorafenib-loaded poly (lactic-co-glycolic) acid (PLGA), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, and hydrophobically modified chitosan (HMC)-coated DPPC liposomes were evaluated for several characteristics including zeta potential, drug loading, and release profile. Cytotoxicity and uptake trials were also studied using cell line RCC 786-0, a human metastatic clear cell histology renal cell carcinoma cell line. Sorafenib-loaded PLGA particles and HMC-coated DPPC liposomes exhibited significantly improved cell kill compared to Sorafenib alone at lower concentrations, namely 10-15 and 5-15 μM from 24 to 96 h, respectively. At maximum dosage and time (15 μM and 96 h), Sorafenib-loaded PLGA and HMC-coated liposomes killed 88.3 ± 1.8% and 98 ± 1.1% of all tumor cells, significant values compared with Sorafenib 81.8 ± 1.7% (p < 0.01). Likewise, HMC coating substantially improved cell kill for liposome model for all concentrations (5-15 μM) and at time points (24-96 h) (p < 0.01). PLGA and HMC-coated liposomes are promising platforms for drug delivery of Sorafenib. Because of different particle characteristics of PLGA and liposomes, each model can be further developed for unique clinical modalities.

  19. Oriented reconstitution of a membrane protein in a giant unilamellar vesicle: experimental verification with the potassium channel KcsA.

    Science.gov (United States)

    Yanagisawa, Miho; Iwamoto, Masayuki; Kato, Ayako; Yoshikawa, Kenichi; Oiki, Shigetoshi

    2011-08-03

    We report a method for the successful reconstitution of the KcsA potassium channel with either an outside-out or inside-out orientation in giant unilamellar vesicles, using the droplet-transfer technique. The procedure is rather simple. First, we prepared water-in-oil droplets lined with a lipid monolayer. When solubilized KcsA was encapsulated in the droplet, it accumulated at monolayers of phosphatidylglycerol (PG) and phosphoethanolamine (PE) but not at a monolayer of phosphatidylcholine (PC). The droplet was then transferred through an oil/water interface having a preformed monolayer. The interface monolayer covered the droplet so as to generate a bilayer vesicle. By creating chemically different lipid monolayers at the droplet and oil/water interface, we obtained vesicles with asymmetric lipid compositions in the outer and inner leaflets. KcsA was spontaneously inserted into vesicles from the inside or outside, and this was accelerated in vesicles that contained PE or PG. Integrated insertion into the vesicle membrane and the KcsA orientation were examined by functional assay, exploiting the pH sensitivity of the opening of the KcsA when the pH-sensitive cytoplasmic domain (CPD) faces toward acidic media. KcsA loaded from the inside of the PG-containing vesicles becomes permeable only when the intravesicular pH is acidic, and the KcsA loaded from the outside becomes permeable when the extravesicular pH is acidic. Therefore, the internal or external insertion of KcsA leads to an outside-out or inside-out configuration so as to retain its hydrophilic CPD in the added aqueous side. The CPD-truncated KcsA exhibited a random orientation, supporting the idea that the CPD determines the orientation. Further application of the droplet-transfer method is promising for the reconstitution of other types of membrane proteins with a desired orientation into cell-sized vesicles with a targeted lipid composition of the outer and inner leaflets.

  20. Topologies, structures and parameter files for lipid simulations in GROMACS with the OPLS-aa force field: DPPC, POPC, DOPC, PEPC, and cholesterol

    Directory of Open Access Journals (Sweden)

    Waldemar Kulig

    2015-12-01

    Full Text Available In this data article we provide topologies and force field parameters files for molecular dynamics simulations of lipids in the OPLS-aa force field using the GROMACS package. This is the first systematic parameterization of lipid molecules in this force field. Topologies are provided for four phosphatidylcholines: saturated DPPC, mono-cis unsaturated POPC and DOPC, and mono-trans unsaturated PEPC. Parameterization of the phosphatidylcholines was achieved in two steps: first, we supplemented the OPLS force field parameters for DPPC with new parameters for torsion angles and van der Waals parameters for the carbon and hydrogen atoms in the acyl chains, as well as new partial atomic charges and parameters for torsion angles in the phosphatidylcholine and glycerol moieties [1]. Next, we derived parameters for the cis and trans double bonds and the neighboring them single bonds [2]. Additionally, we provide GROMACS input files with parameters describing simulation conditions (md.mdp, which are strongly recommended to be used with these lipids models. The data are associated with the research article “Cis and trans unsaturated phosphatidylcholine bilayers: a molecular dynamics simulation study” [2] and provided as supporting materials.

  1. Mechanisms of action of (meth)acrylates in hemolytic activity, in vivo toxicity and dipalmitoylphosphatidylcholine (DPPC) liposomes determined using NMR spectroscopy.

    Science.gov (United States)

    Fujisawa, Seiichiro; Kadoma, Yoshinori

    2012-01-01

    We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H(50)) or in vivo mouse intraperitoneal (ip) LD(50) using reported data for α,β-unsaturated carbonyl compounds such as (meth)acrylate monomers and their (13)C-NMR β-carbon chemical shift (δ). The log 1/H(50) value for methacrylates was linearly correlated with the δC(β) value. That for (meth)acrylates was linearly correlated with log P, an index of lipophilicity. The ipLD(50) for (meth)acrylates was linearly correlated with δC(β) but not with log P. For (meth)acrylates, the δC(β) value, which is dependent on the π-electron density on the β-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω), whereas log P was linearly correlated with heat of formation (HF). Also, the interaction between (meth)acrylates and DPPC liposomes in cell membrane molecular models was investigated using (1)H-NMR spectroscopy and differential scanning calorimetry (DSC). The log 1/H(50) value was related to the difference in chemical shift (ΔδHa) (Ha: H (trans) attached to the β-carbon) between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (meth)acrylates.

  2. Temperature-dependent drug release from DPPC:C12H25-PNIPAM-COOH liposomes: control of the drug loading/release by modulation of the nanocarriers' components.

    Science.gov (United States)

    Pippa, Natassa; Meristoudi, Anastasia; Pispas, Stergios; Demetzos, Costas

    2015-05-15

    Novel polymer-modified thermosensitive liposomes were developed for the delivery of indomethacin in order to control its release profile. When attached to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, the end functionalized C12H25-poly(N-isopropylacrylamide)-COOH (C12H25-PNIPAM-COOH) polymer was membrane-disruptive in a temperature-dependent manner. The interest for this polymer is driven by its famous lower critical solution temperature (LCST) behavior, where heating an aqueous solution of PNIPAM above 32°C induces nanophase separation and polymer chain aggregation. The physicochemical/structural behavior of these polymer-modified thermosensitive liposomes was found to depend on the PNIPAM:lipid molar ratio and the composition of the polymeric guest. The incorporation of PNIPAM has caused alterations in the thermotropic behavior of DPPC liposomes, as the differential scanning calorimetry (DSC) experiments revealed. The drug loading and the release were found to be strongly dependent on the thermotropic characteristics of the PNIPAM grafted DPPC liposomes. Namely, the in vitro release is immediate at 37°C (>LCST) ("burst" effect), while the prepared mixed nanocarriers did not release the encapsulated bioactive substance at <32°C (DPPC/PNIPAM components, as well as the molecular characteristics of the polymeric guest.

  3. Structural Effects of Small Molecules on Phospholipid Bilayers Investigated by Molecular Simulations

    CERN Document Server

    Lee, B W; Sum, A K; Vattulainen, I; Patra, M; Karttunen, M; Lee, Bryan W; Faller, Roland; Sum, Amadeu K; Vattulainen, Ilpo; Patra, Michael; Karttunen, Mikko

    2004-01-01

    We summarize and compare recent Molecular Dynamics simulations on the interactions of dipalmitoylphosphatidylcholine (DPPC) bilayers in the liquid crystalline phase with a number of small molecules including trehalose, a disaccharide of glucose, alcohols, and dimethylsulfoxide (DMSO). The sugar molecules tend to stabilize the structure of the bilayer as they bridge adjacent lipid headgroups. They do not strongly change the structure of the bilayer. Alcohols and DMSO destabilize the bilayer as they increase its area per molecule in the bilayer plane and decrease the order parameter. Alcohols have a stronger detrimental effect than DMSO. The observables which we compare are the area per molecule in the plane of the bilayer, the membrane thickness, and the NMR order parameter of DPPC hydrocarbon tails. The area per molecule and the order parameter are very well correlated whereas the bilayer thickness is not necessarily correlated with them.

  4. Transfer of a lipophilic drug (temoporfin) between small unilamellar liposomes and human plasma proteins: influence of membrane composition on vesicle integrity and release characteristics.

    Science.gov (United States)

    Decker, Christiane; Steiniger, Frank; Fahr, Alfred

    2013-06-01

    The introduction of PEG lipid conjugates into lipid bilayers leads to long circulating liposomes with improved pharmacokinetics and pharmacodynamics characteristics. The concentration range of PEG-lipids is limited by their micelle forming properties. We investigated two phosphatidyl oligoglycerols as potential alternatives to PEG-lipid conjugates and compared their micelle forming properties after incorporation of increasing amounts of oligoglycerols into gel-phase liposomes via cryo-transmission electron microscopy. The incorporation of highly hydrophobic drugs into liposomes makes water soluble formulations possible and improves the therapeutic properties of the drug. We incorporated the hydrophobic photosensitizer temoporfin into liposomes varying in membrane fluidity and nature of surface modifying agents. The main purpose of this study was the investigation of liposome integrity and temoporfin incorporation stability in the presence of plasma. After incubation of temoporfin-loaded liposomes with human plasma for different time intervals, liposomes and the single lipoprotein fractions were separated via size-exclusion chromatography. Liposome stability and temoporfin distribution profile over the lipoprotein fractions were determined with the help of a non-exchangeable ³H-lipid label and ¹⁴C-labeled temoporfin. The results demonstrate that both oligoglycerols are suitable alternatives to PEG-lipid conjugates because of the lack of micelle forming properties, comparable liposome stability, and a reduced temoporfin transfer rate compared to PEG-lipids. Furthermore, the incorporation stability of temoporfin is--at least to some extent--influenced by membrane fluidity, indicating that fluid membranes may be better suited for retention of lipophilic drugs.

  5. Structure and phase transformations of DPPC lipid bilayers in the presence of nanoparticles: insights from coarse-grained molecular dynamics simulations.

    Science.gov (United States)

    Prates Ramalho, J P; Gkeka, P; Sarkisov, L

    2011-04-05

    In this article, we investigate fluid-gel transformations of a DPPC lipid bilayer in the presence of nanoparticles, using coarse-grained molecular dynamics. Two types of nanoparticles are considered, specifically a 3 nm hydrophobic nanoparticle located in the core of the bilayer and a 6 nm charged nanoparticle located at the interface between the bilayer and water phase. Both negatively and positively charged nanoparticles at the bilayer interface are investigated. We demonstrate that the presence of all types of nanoparticles induces disorder effects in the structure of the lipid bilayer. These effects are characterized using computer visualization of the gel phase in the presence of nanoparticles, radial distribution functions, and order parameters. The 3 nm hydrophobic nanoparticle immersed in the bilayer core and the positively charged nanoparticle at the bilayer surface have no effect on the temperature of the fluid-gel transformation, compared to the bulk case. Interestingly, a negatively charged hydrophobic nanoparticle located at the surface of the bilayer causes slight shift of the fluid-gel transformation to a lower temperature, compared to the bulk bilayer case.

  6. Optimizing Process and Formula and Analyzing Quality for IvermectinSingle Unilamellar Vesicles%伊维菌素小单室脂质体工艺配方优化及质量分析

    Institute of Scientific and Technical Information of China (English)

    何书海; 巴桑旺堆; 佘永新

    2012-01-01

    To obtain high entrapment rate of ivermectin single unilamellar vesicles. The study was aim to optimizing preparation process of ivermectin single unilamellar vesicles; we had selected some factors such as ultrasonic frequency, ultrasonic time, mass ratio of lecithin to cholesterol and mass ratio of ivermectin to lecithin to design orthogonal test Ls (27) , and we used RP-HPLC to determine the entrapment rate of ivermectin single unilamellar vesicles under every combination of process and formula. The results showed the optimal process and formula combination of ivermectin single unilamellar vesicles were as follows; the ultrasonic frequency was 200 kHz, the ultrasonic time was 6 minutes and the mass ratio of ivermectin to lecithin was 1: 10. We have obtained high qualitative ivermectin single unilamellar vesicles by optimization, the loading rate reach (92. 35± 0. 61)% ,the quality of drug is fine, the preparation process are simple and feasible.%为获得高包封率的伊维菌素小单室脂质体,本研究对其制备工艺进行了优化,并选取超声波频率、超声时间、卵磷脂与胆固醇质量比、伊维菌素与卵磷脂质量比各因素进行正交交互作用考察,同时利用反相高效液相色谱法对各工艺配方组合下伊维菌素小单室脂质体的包封率进行了测定.结果显示,伊维菌素小单室脂质体的制备最佳配方和工艺组合为超声波频率200 kHz,超声时间6 min,伊维菌素与大豆卵磷脂质量比为1∶10.经过优化组合,得到了较高品质的伊维菌素小单室脂质体,平均载药量达到(92.35±0.61)%,药物品质优良,且制备工艺简单可行.

  7. Mode of interaction of ganglioside Langmuir monolayer originated from echinoderms: three binary systems of ganglioside/DPPC, ganglioside/DMPE, and ganglioside/cholesterol.

    Science.gov (United States)

    Hoda, Kazuki; Ikeda, Yuriko; Kawasaki, Hideya; Yamada, Koji; Higuchi, Ryuichi; Shibata, Osamu

    2006-09-01

    The surface pressure (pi)-area (A), the surface potential (DeltaV)-A, and the dipole moment (mu( perpendicular))-A isotherms were obtained for monolayers made from a ganglioside originated from echinoderms [Diadema setosum ganglioside (DSG-1)], dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylethanolamine (DMPE), cholesterol (Ch), and their combinations. Monolayers spread on several different substrates were investigated at the air/water interface by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM) and atomic force microscopy (AFM). Surface potentials (DeltaV) of pure components were analyzed using the three-layer model proposed by Demchak and Fort [R.J. Demchak, T. Fort, J. Colloid Interface Sci. 46 (1974) 191-202]. The new finding was that DSG-1 was stable and showed a liquid-expanded film and that its monolayer behavior of DeltaV was sensitive for the change of the NaCl concentration in the subphase. Moreover, the miscibility of DSG-1 and three major lipids in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the DSG-1 molar fraction (X(DSG-1)), using the additivity rule. From the A-X(DSG-1) and DeltaV(m)-X(DSG-1) plots, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible system. The miscibility was also investigated from the two-dimensional phase diagrams. Furthermore, a regular surface mixture, for which the Joos equation was used for the analysis of the collapse pressure of two-component monolayers, allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltavarepsilon) between them. The observations using fluorescence microscopy and AFM image also provide us the miscibility in the monolayer state.

  8. Structure and dynamics of H{sub 2}O vis-á-vis phenylalanine recognition at a DPPC lipid membrane via interfacial H-bond types: Insights from polarized FT-IRRAS and ADMP simulations

    Energy Technology Data Exchange (ETDEWEB)

    Sarangi, Nirod Kumar; Ramesh, Nivarthi; Patnaik, Archita [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India)

    2015-01-14

    Preferential and enantioselective interactions of L-/D-Phenylalanine (L-Phe and D-Phe) and butoxycarbonyl-protected L-/D-Phenylalanine (LPA and DPA) as guest with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (L-DPPC) as host were tapped by using real time Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Polarization-modulated FT-IRRAS of DPPC monolayers above the phenylalanine modified subphases depicted fine structure/conformation differences under considerations of controlled 2D surface pressure. Selective molecular recognition of D-enantiomer over L-enantiomer driven by the DPPC head group via H-bonding and electrostatic interactions was evident spectroscopically. Accordingly, binding constants (K) of 145, 346, 28, and 56 M{sup −1} for LPA, DPA, L-Phe, and D-Phe, respectively, were estimated. The real time FT-IRRAS water bands were strictly conformation sensitive. The effect of micro-solvation on the structure and stability of the 1:1 diastereomeric L-lipid⋯, LPA/DPA and L-lipid⋯, (L/D)-Phe adducts was investigated with the aid of Atom-centered Density Matrix Propagation (ADMP), a first principle quantum mechanical molecular dynamics approach. The phosphodiester fragment was the primary site of hydration where specific solvent interactions were simulated through single- and triple- “water-phosphate” interactions, as water cluster’s “tetrahedral dice” to a “trimeric motif” transformation as a partial de-clusterization was evident. Under all the hydration patterns considered in both static and dynamic descriptions of density functional theory, L-lipid/D-amino acid enantiomer adducts continued to be stable structures while in dynamic systems, water rearranged without getting “squeezed-out” in the process of recognition. In spite of the challenging computational realm of this multiscale problem, the ADMP simulated molecular interactions complying with polarized vibrational spectroscopy unraveled a novel route to chiral

  9. Structure and dynamics of H2O vis-á-vis phenylalanine recognition at a DPPC lipid membrane via interfacial H-bond types: Insights from polarized FT-IRRAS and ADMP simulations

    Science.gov (United States)

    Sarangi, Nirod Kumar; Ramesh, Nivarthi; Patnaik, Archita

    2015-01-01

    Preferential and enantioselective interactions of l-/d-Phenylalanine (l-Phe and d-Phe) and butoxycarbonyl-protected l-/d-Phenylalanine (LPA and DPA) as guest with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (l-DPPC) as host were tapped by using real time Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Polarization-modulated FT-IRRAS of DPPC monolayers above the phenylalanine modified subphases depicted fine structure/conformation differences under considerations of controlled 2D surface pressure. Selective molecular recognition of d-enantiomer over l-enantiomer driven by the DPPC head group via H-bonding and electrostatic interactions was evident spectroscopically. Accordingly, binding constants (K) of 145, 346, 28, and 56 M-1 for LPA, DPA, l-Phe, and d-Phe, respectively, were estimated. The real time FT-IRRAS water bands were strictly conformation sensitive. The effect of micro-solvation on the structure and stability of the 1:1 diastereomeric l-lipid⋯, LPA/DPA and l-lipid⋯, (l/d)-Phe adducts was investigated with the aid of Atom-centered Density Matrix Propagation (ADMP), a first principle quantum mechanical molecular dynamics approach. The phosphodiester fragment was the primary site of hydration where specific solvent interactions were simulated through single- and triple- "water-phosphate" interactions, as water cluster's "tetrahedral dice" to a "trimeric motif" transformation as a partial de-clusterization was evident. Under all the hydration patterns considered in both static and dynamic descriptions of density functional theory, l-lipid/d-amino acid enantiomer adducts continued to be stable structures while in dynamic systems, water rearranged without getting "squeezed-out" in the process of recognition. In spite of the challenging computational realm of this multiscale problem, the ADMP simulated molecular interactions complying with polarized vibrational spectroscopy unraveled a novel route to chiral recognition and

  10. Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering.

    Science.gov (United States)

    Kontro, Inkeri; Svedström, Kirsi; Duša, Filip; Ahvenainen, Patrik; Ruokonen, Suvi-Katriina; Witos, Joanna; Wiedmer, Susanne K

    2016-12-01

    The effects of ionic liquids on model phospholipid membranes were studied by small-angle X-ray scattering, dynamic light scattering (DLS) and zeta potential measurements. Multilamellar 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes and large unilamellar vesicles composed of l-α-phosphatidylcholine (eggPC) and l-α-phosphatidylglycerol (eggPG) (80:20mol%) or eggPC, eggPG, and cholesterol (60:20:20mol%) were used as biomimicking membrane models. The effects of the phosphonium-based ionic liquids: tributylmethylphosphonium acetate, trioctylmethylphosphonium acetate, tributyl(tetradecyl)-phosphonium acetate, and tributyl(tetradecyl)-phosphonium chloride, were compared to those of 1-ethyl-3-methyl-imidazolium acetate. With multilamellar vesicles, the ionic liquids that did not disrupt liposomes decreased the lamellar spacing as a function of concentration. The magnitude of the effect depended on concentration for all studied ionic liquids. Using large unilamellar vesicles, first a slight decrease in the vesicle size, then aggregation of vesicles was observed by DLS for increasing ionic liquid concentrations. At concentrations just below those that caused aggregation of liposomes, large unilamellar vesicles were coated by ionic liquid cations, evidenced by a change in their zeta potential. The ability of phosphonium-based ionic liquids to affect liposomes is related to the length of the hydrocarbon chains in the cation. Generally, the ability of ionic liquids to disrupt liposomes goes hand in hand with inducing disorder in the phospholipid membrane. However, trioctylmethylphosphonium acetate selectively extracted and induced a well-ordered lamellar structure in phospholipids from disrupted cholesterol-containing large unilamellar vesicles. This kind of effect was not seen with any other combination of ionic liquids and liposomes.

  11. Femtosecond three-photon excitation and single-photon timing detection of α-NPO fluorescence

    Science.gov (United States)

    Volkmer, A.; Hatrick, D. A.; Bai, Y.; Birch, D. J. S.

    1997-04-01

    We demonstrate the application of three-photon excitation to fluorescence probe studies using time-correlated single-photon counting (TCSPC). By exciting with 120 fs Ti:sapphire laser pulses at 800 nm we have observed fluorescence emission from the scintillator 2-(1-napthyl)-5-phenyloxazole (α-NPO) in solutions and small unilamellar vesicles (SUVs) of L-α-dipalmitoylphosphatidylcholine (DPPC). In SUVs the time-resolved excimer emission and fluorescence anisotropy are consistent with a heterogeneous distribution of α-NPO molecules between isolated sites and ground state clusters in a similar manner to that which we reported previously for 2,5-diphenyloxazole (PPO).

  12. Structural features of colloidal species in the human fasted upper small intestine

    DEFF Research Database (Denmark)

    Mullertz, Anette; Reppas, Christos; Psachoulias, Dimitrios;

    2015-01-01

    Objectives This paper aims to study the features of colloidal species in the lumen of the upper small intestine of two healthy adults at fasted state by means of electron microscopy. Methods Samples were aspirated from a location near the ligament of Treitz 30 min (volunteer no. 1, Aspirate30min...... with previously studied samples from the lower intestine in the fasted state. Micelles and unilamellar vesicles observed in both samples closely resemble morphological characteristics of those found in fluids simulating the colloidal species in fasted upper intestinal environment. Conclusions Features...... of colloidal species in contents of fasted small intestine have similarities with fluids simulating the contents in fasted upper small intestine and with contents of lower intestine in the fasted state....

  13. A study of the antibacterial activity of L-phenylalanine and L-tyrosine esters in relation to their CMCs and their interactions with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC as model membrane.

    Science.gov (United States)

    Joondan, Nausheen; Jhaumeer-Laulloo, Sabina; Caumul, Prakashanand

    2014-01-01

    Cationic amino acid-based surfactants are known to interact with the lipid bilayer of cell membranes resulting in depolarization, lysis and cell death through a disruption of the membrane topology. A range of cationic surfactant analogues derived from L-Phenylalanine (C1-C20) and L-Tyrosine (C8-C14) esters have been synthesized and screened for their antibacterial activity. The esters were more active against gram positive than gram negative bacteria. The activity increased with increasing chain length, exhibiting a cut-off effect at C12 for gram positive and C8/C10 for gram negative bacteria. The cut-off effect for gram negative bacteria was observed at a lower alkyl chain length. The CMC was correlated with the MIC, inferring that micellar activity contribute to the cut-off effect in antibacterial activity. The interaction of the cationic surfactants with the phospholipid vesicles (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC) in the presence of 1-anilino-8-naphthalene sulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescence probes showed that an increase in ionic interaction causes an increase in antibacterial activity. Increase in hydrophobic interaction increases the antibacterial activity only to a certain chain length, attributing to the cut-off effect. Therefore, both electrostatic and hydrophobic interactions, involving the polar and nonpolar moieties are of paramount importance for the bactericidal properties.

  14. Hydration lubrication and shear-induced self-healing of lipid bilayer boundary lubricants in phosphatidylcholine dispersions.

    Science.gov (United States)

    Sorkin, Raya; Kampf, Nir; Zhu, Linyi; Klein, Jacob

    2016-03-14

    Measurements of normal and shear (frictional) forces between mica surfaces across small unilamellar vesicle (SUV) dispersions of the phosphatidylcholine (PC) lipids DMPC (14:0), DPPC (16:0) and DSPC (18:0) and POPC (16:0, 18:1), at physiologically high pressures, are reported. We have previously studied the normal and shear forces between two opposing surfaces bearing PC vesicles across pure water and showed that liposome lubrication ability improved with increasing acyl chain length, and correlated strongly with the SUV structural integrity on the substrate surface (DSPC > DPPC > DMPC). In the current study, surprisingly, we discovered that this trend is reversed when the measurements are conducted in SUV dispersions, instead of pure water. In their corresponding SUV dispersion, DMPC SUVs ruptured and formed bilayers, which were able to provide reversible and reproducible lubrication with extremely low friction (μ lubrication, but with slightly higher friction coefficients (μ = 10(-3)-10(-4)). We believe these differences originate from fast self-healing of the softer surface layers (which are in their liquid disordered phase, POPC, or close to it, DMPC), which renders the robustness of the DPPC or DSPC (both in their solid ordered phase) less important in these conditions. Under these circumstances, the enhanced hydration of the less densely packed POPC and DMPC surface layers is now believed to play an important role, and allows enhanced lubrication via the hydration lubrication mechanism. Our findings may have implications for the understanding of complex biological systems such us biolubrication of synovial joints.

  15. Aggregation of liposomes in presence of La3+: a study of the fractal dimension.

    Science.gov (United States)

    Sabín, Juan; Prieto, Gerardo; Ruso, Juan M; Messina, Paula; Sarmiento, Félix

    2007-07-01

    A study of the fractal dimension of the aggregation of three different types of large unilamellar vesicles, formed by egg yolk phosphatidylcholine (EYPC), dimyristoyl-phosphocholine (DMPC), and dipalmitoyl-phosphocholine (DPPC), in the presence of La3+, is presented. Aggregate liposome fractal dimensions were calculated by two methods, aggregation kinetics, using the approaches diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA) and angle-scattering light dispersion. Electrophoretic measurements show a similar variation of the zeta potential (zeta potential) for EYPC and DPPC, with a small increase of initial positive values. However, the zeta potential of DMPC changes from a initial negative value to near zero with increasing La3+ concentration. The evolution of the aggregate sizes was followed by light scattering. DPPC and DMPC show a RLCA regimen growth at low La3+ concentrations and a DLCA regimen at higher concentrations. In the case of EYPC, the final size of aggregation strongly depends on La3+ concentration. The calculated fractal dimension is in the range 1.8 to 2.1.

  16. Design, physicochemical characterization, and optimization of organic solution advanced spray-dried inhalable dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine poly(ethylene glycol) (DPPE-PEG) microparticles and nanoparticles for targeted respiratory nanomedicine delivery as dry powder inhalation aerosols.

    Science.gov (United States)

    Meenach, Samantha A; Vogt, Frederick G; Anderson, Kimberly W; Hilt, J Zach; McGarry, Ronald C; Mansour, Heidi M

    2013-01-01

    Novel advanced spray-dried and co-spray-dried inhalable lung surfactant-mimic phospholipid and poly(ethylene glycol) (PEG)ylated lipopolymers as microparticulate/nanoparticulate dry powders of biodegradable biocompatible lipopolymers were rationally formulated via an organic solution advanced spray-drying process in closed mode using various phospholipid formulations and rationally chosen spray-drying pump rates. Ratios of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine PEG (DPPE-PEG) with varying PEG lengths were mixed in a dilute methanol solution. Scanning electron microscopy images showed the smooth, spherical particle morphology of the inhalable particles. The size of the particles was statistically analyzed using the scanning electron micrographs and SigmaScan® software and were determined to be 600 nm to 1.2 μm in diameter, which is optimal for deep-lung alveolar penetration. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were performed to analyze solid-state transitions and long-range molecular order, respectively, and allowed for the confirmation of the presence of phospholipid bilayers in the solid state of the particles. The residual water content of the particles was very low, as quantified analytically via Karl Fischer titration. The composition of the particles was confirmed using attenuated total-reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and confocal Raman microscopy (CRM), and chemical imaging confirmed the chemical homogeneity of the particles. The dry powder aerosol dispersion properties were evaluated using the Next Generation Impactor™ (NGI™) coupled with the HandiHaler® dry powder inhaler device, where the mass median aerodynamic diameter from 2.6 to 4.3 μm with excellent aerosol dispersion performance, as exemplified by high values of emitted dose, fine particle fraction, and respirable fraction. Overall, it was determined that the pump rates defined in the

  17. Design, physicochemical characterization, and optimization of organic solution advanced spray-dried inhalable dipalmitoylphosphatidylcholine (DPPC and dipalmitoylphosphatidylethanolamine poly(ethylene glycol (DPPE-PEG microparticles and nanoparticles for targeted respiratory nanomedicine delivery as dry powder inhalation aerosols

    Directory of Open Access Journals (Sweden)

    Meenach SA

    2013-01-01

    Full Text Available Samantha A Meenach,1,2 Frederick G Vogt,3 Kimberly W Anderson,2,4 J Zach Hilt,2,4 Ronald C McGarry,5Heidi M Mansour1,41Department of Pharmaceutical Sciences-Drug Development Division, University of Kentucky College of Pharmacy, Lexington, KY; 2Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY, USA; 3Analytical Sciences, Product Development, GlaxoSmithKline, King of Prussia, PA; 4Center of Membrane Sciences, University of Kentucky, Lexington, KY, 5Department of Radiation Medicine, University of Kentucky College of Medicine, Lexington, KY, USAAbstract: Novel advanced spray-dried and co-spray-dried inhalable lung surfactant-mimic phospholipid and poly(ethylene glycol (PEGylated lipopolymers as microparticulate/nanoparticulate dry powders of biodegradable biocompatible lipopolymers were rationally formulated via an organic solution advanced spray-drying process in closed mode using various phospholipid formulations and rationally chosen spray-drying pump rates. Ratios of dipalmitoylphosphatidylcholine (DPPC and dipalmitoylphosphatidylethanolamine PEG (DPPE-PEG with varying PEG lengths were mixed in a dilute methanol solution. Scanning electron microscopy images showed the smooth, spherical particle morphology of the inhalable particles. The size of the particles was statistically analyzed using the scanning electron micrographs and SigmaScan® software and were determined to be 600 nm to 1.2 μm in diameter, which is optimal for deep-lung alveolar penetration. Differential scanning calorimetry (DSC and powder X-ray diffraction (PXRD were performed to analyze solid-state transitions and long-range molecular order, respectively, and allowed for the confirmation of the presence of phospholipid bilayers in the solid state of the particles. The residual water content of the particles was very low, as quantified analytically via Karl Fischer titration. The composition of the particles was confirmed using attenuated

  18. Small Interfering RNA Transfection Across a Phospholipid Membrane

    Science.gov (United States)

    Ngo, Van; Choubey, Amit; Kalia, Rajiv; Nakano, Aiichiro; Vashishta, Priya

    2012-02-01

    Small interfering RNA (siRNA) molecules play a pivotal role in silencing gene expression via the RNA interference mechanism. We have performed steered MD simulations to study the transfection of a bare siRNA and siRNA/Oleic Acid (OA) complex across the dipalmitoylphosphatidycholine (DPPC) bilayer at T = 323 K. Bare siRNA induces the formation of frustrated lipid gel domains, whereas in the presence of siRNA/OA complex the membrane is found to be in the liquid-ordered phase. In both cases the stress profiles across the membrane indicate that the membrane is under tension near the head groups and highly compressed at the water-hydrophobic interface. During transfection, the membrane is deformed and the lateral stress is significantly lowered for the bare siRNA and siRNA/OA complex. The bare siRNA transfects through a lipid-nanopore of hydrophilic head-groups and hydrophobic carbon chains, whereas the siRNA/OA complex transfects through a lipid-nanopore of hydrophilic head groups.

  19. Small Orbits

    CERN Document Server

    Borsten, L; Ferrara, S; Marrani, A; Rubens, W

    2012-01-01

    We study both the "large" and "small" U-duality charge orbits of extremal black holes appearing in D = 5 and D = 4 Maxwell-Einstein supergravity theories with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan algebras and their associated Freudenthal triple systems, in order to derive the minimal charge representatives, their stabilizers and the associated "moduli spaces". After recalling N = 8 maximal supergravity, we consider N = 2 and N = 4 theories coupled to an arbitrary number of vector multiplets, as well as N = 2 magic, STU, ST^2 and T^3 models. While the STU model may be considered as part of the general N = 2 sequence, albeit with an additional triality symmetry, the ST^2 and T^3 models demand a separate treatment, since their representative Jordan algebras are Euclidean or only admit non-zero elements of rank 3, respectively. Finally, we also consider minimally coupled N = 2, matter coupled N = 3, and "pure" N = 5 theories.

  20. In vivo Stability of Ester- and Ether-Linked Phospholipid-Containing Liposomes as Measured by Perturbed Angular Correlation Spectroscopy

    Science.gov (United States)

    Derksen, Johannes T.; Baldeschwieler, John D.; Scherphof, Gerrit L.

    1988-12-01

    To evaluate liposome formulations for use as intracellular sustained-release drug depots, we have compared the uptake and degradation in rat liver and spleen of liposomes of various compositions, containing as their bulk phospholipid an ether-linked phospholipid or one of several ester-linked phospholipids, by perturbed angular correlation spectroscopy. Multilamellar and small unilamellar vesicles (MLVs and SUVs), composed of egg phosphatidylcholine, sphingomyelin, distearoyl phosphatidylcholine (DSPC), dipalmitoyl phosphatidylcholine (DPPC) or its analog dihexadecylglycerophosphorylcholine (DHPC), and cholesterol plus phosphatidylserine, and containing 111In complexed to nitrilotriacetic acid, were injected intravenously in rats. Recovery of 111In-labeled liposomes in blood, liver, and spleen was assessed at specific time points after injection and the percentage of liposomes still intact in liver and spleen was determined by measurement of the time-integrated angular perturbation factor 111In of the [G22(∞ )] label. We found that MLVs but not SUVs, having DHPC as their bulk phospholipid, showed an increased resistance against lysosomal degradation as compared to other phospholipid-containing liposomes. The use of diacyl phospholipids with a high gel/liquid-crystalline phase-transition temperature, such as DPPC and DSPC, also retarded degradation of MLV, but not of SUV in the dose range tested, while the rate of uptake of these liposomes by the liver was lower.

  1. Small cationic DDA:TDB liposomes as protein vaccine adjuvants obviate the need for TLR agonists in inducing cellular and humoral responses.

    Directory of Open Access Journals (Sweden)

    Anita Milicic

    Full Text Available Most subunit vaccines require adjuvants in order to induce protective immune responses to the targeted pathogen. However, many of the potent immunogenic adjuvants display unacceptable local or systemic reactogenicity. Liposomes are spherical vesicles consisting of single (unilamellar or multiple (multilamellar phospholipid bi-layers. The lipid membranes are interleaved with an aqueous buffer, which can be utilised to deliver hydrophilic vaccine components, such as protein antigens or ligands for immune receptors. Liposomes, in particular cationic DDA:TDB vesicles, have been shown in animal models to induce strong humoral responses to the associated antigen without increased reactogenicity, and are currently being tested in Phase I human clinical trials. We explored several modifications of DDA:TDB liposomes--including size, antigen association and addition of TLR agonists--to assess their immunogenic capacity as vaccine adjuvants, using Ovalbumin (OVA protein as a model protein vaccine. Following triple homologous immunisation, small unilamellar vesicles (SUVs with no TLR agonists showed a significantly higher capacity for inducing spleen CD8 IFNγ responses against OVA in comparison with the larger multilamellar vesicles (MLVs. Antigen-specific antibody reponses were also higher with SUVs. Addition of the TLR3 and TLR9 agonists significantly increased the adjuvanting capacity of MLVs and OVA-encapsulating dehydration-rehydration vesicles (DRVs, but not of SUVs. Our findings lend further support to the use of liposomes as protein vaccine adjuvants. Importantly, the ability of DDA:TDB SUVs to induce potent CD8 T cell responses without the need for adding immunostimulators would avoid the potential safety risks associated with the clinical use of TLR agonists in vaccines adjuvanted with liposomes.

  2. Small cationic DDA:TDB liposomes as protein vaccine adjuvants obviate the need for TLR agonists in inducing cellular and humoral responses.

    Science.gov (United States)

    Milicic, Anita; Kaur, Randip; Reyes-Sandoval, Arturo; Tang, Choon-Kit; Honeycutt, Jared; Perrie, Yvonne; Hill, Adrian V S

    2012-01-01

    Most subunit vaccines require adjuvants in order to induce protective immune responses to the targeted pathogen. However, many of the potent immunogenic adjuvants display unacceptable local or systemic reactogenicity. Liposomes are spherical vesicles consisting of single (unilamellar) or multiple (multilamellar) phospholipid bi-layers. The lipid membranes are interleaved with an aqueous buffer, which can be utilised to deliver hydrophilic vaccine components, such as protein antigens or ligands for immune receptors. Liposomes, in particular cationic DDA:TDB vesicles, have been shown in animal models to induce strong humoral responses to the associated antigen without increased reactogenicity, and are currently being tested in Phase I human clinical trials. We explored several modifications of DDA:TDB liposomes--including size, antigen association and addition of TLR agonists--to assess their immunogenic capacity as vaccine adjuvants, using Ovalbumin (OVA) protein as a model protein vaccine. Following triple homologous immunisation, small unilamellar vesicles (SUVs) with no TLR agonists showed a significantly higher capacity for inducing spleen CD8 IFNγ responses against OVA in comparison with the larger multilamellar vesicles (MLVs). Antigen-specific antibody reponses were also higher with SUVs. Addition of the TLR3 and TLR9 agonists significantly increased the adjuvanting capacity of MLVs and OVA-encapsulating dehydration-rehydration vesicles (DRVs), but not of SUVs. Our findings lend further support to the use of liposomes as protein vaccine adjuvants. Importantly, the ability of DDA:TDB SUVs to induce potent CD8 T cell responses without the need for adding immunostimulators would avoid the potential safety risks associated with the clinical use of TLR agonists in vaccines adjuvanted with liposomes.

  3. Small Business Development Center

    Data.gov (United States)

    Small Business Administration — Small Business Development Centers (SBDCs) provide assistance to small businesses and aspiring entrepreneurs throughout the United States and its territories. SBDCs...

  4. Using Small-Angle Neutron Scattering to Detect Nanoscopic Lipid Domains

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Jianjun [ORNL; Heberle, Frederick A [ORNL; Petruzielo, Robin S [Cornell University; Katsaras, John [ORNL

    2013-01-01

    The cell plasma membrane is a complex system, which is thought to be capable of exhibiting non-random lateral organization. Studies of live cells and model membranes have yielded mechanisms responsible for the formation, growth, and maintenance of nanoscopic heterogeneities, although the existence and mechanisms that give rise to these heterogeneities remain controversial. Small-angle neutron scattering (SANS) is a tool ideally suited to interrogate lateral heterogeneity in model membranes, primarily due to its unique spatial resolution (i.e., "5 100 nm) and its ability to resolve structure with minimal perturbation to the membrane. In this review we examine several methods used to analyze the SANS signal arising from freely suspended unilamellar vesicles containing lateral heterogeneity. Specifically, we discuss an analytical model for a single, round domain on a spherical vesicle. We then discuss a numerical method that uses Monte Carlo simulation to describe systems with multiple domains and/or more complicated morphologies. Also discussed are several model-independent approaches that are sensitive to membrane heterogeneity. The review concludes with several recent applications of SANS to the study of membrane raft mixtures.

  5. Are Subject Small Clauses Really Small Clauses?

    Science.gov (United States)

    Kubo, Miori

    1993-01-01

    This paper discusses the ongoing debate over small clauses concerning the structure of the verb phrase in "I consider Bill smart." It is demonstrated that the subject constituent in question is not a small clause, but a Noun Phrase (NP), following Noun (N). It is shown that some peculiar phenomena under the small clause analysis are natural…

  6. Lung cancer - small cell

    Science.gov (United States)

    Cancer - lung - small cell; Small cell lung cancer; SCLC ... About 15% of all lung cancer cases are SCLC. Small cell lung cancer is slightly more common in men than women. Almost all cases of SCLC are ...

  7. Small Business Size Standards

    Data.gov (United States)

    Small Business Administration — Certain government programs, such as SBA loan programs and contracting opportunities, are reserved for small business concerns. In order to qualify, businesses must...

  8. Lipid lateral organization on giant unilamellar vesicles containing lipopolysaccharides

    DEFF Research Database (Denmark)

    Kubiak, Jakub; Brewer, Jonathan R.; Hansen, Søren

    2011-01-01

    spectroscopy (using fluorescently labeled LPS) and Laurdan GP experiments in these microscopically homogeneous membranes suggests the presence of LPS clusters with dimensions below our microscope's resolution (∼380 nm radial). Our results indicate that LPSs can cluster into gel-like domains in these bacterial...

  9. BRANDING IN SMALL BUSINESS

    Directory of Open Access Journals (Sweden)

    Mihai Răzvan Constantin BARBU

    2010-01-01

    Full Text Available In this paper we analyzed the branding in small business. Using a desk research on Internet and the press we have identified the practices small businesses use to enhance their brand and the brand dynamics in small business. Our main contribution is that we tried to figure out the strategy of branding in small business. This need further to be investigated in order to understand how branding works in small business and to better capture the role of branding in small business.

  10. Small-scale Biorefining

    NARCIS (Netherlands)

    Visser, de C.L.M.; Ree, van R.

    2016-01-01

    One promising way to accelerate the market implementation of integrated biorefineries is to promote small (regional) biorefinery initiatives. Small-scale biorefineries require relatively low initial investments, and therefore are often lacking the financing problems that larger facilities face. They

  11. Chairing a Small Department.

    Science.gov (United States)

    Bowker, Lee H.; Lynch, David M.

    Ten management problems for chairs of small departments in small colleges are discussed, along with problem-solving strategies for these administrators. Serious disagreements within a small and intimate department may create a country club culture in which differences are smoothed over and the personal idiosyncrasies of individual members are…

  12. Small cell glioblastoma or small cell carcinoma

    DEFF Research Database (Denmark)

    Hilbrandt, Christine; Sathyadas, Sathya; Dahlrot, Rikke H

    2013-01-01

    was admitted to the hospital with left-sided loss of motor function. A MRI revealed a 6 cm tumor in the right temporoparietal area. The histology was consistent with both glioblastoma multiforme (GBM) and small cell lung carcinoma (SCLC) but IHC was suggestive of a SCLC metastasis. PET-CT revealed...

  13. Small asteroid system evolution

    OpenAIRE

    Jacobson, Seth A.

    2014-01-01

    Observations with radar, photometric and direct imaging techniques have discovered that multiple asteroid systems can be divided clearly into a handful of different morphologies, and recently, the discovery of small unbound asteroid systems called asteroid pairs have revolutionized the study of small asteroid systems. Simultaneously, new theoretical advances have demonstrated that solar radiation dictates the evolution of small asteroids with strong implications for asteroid internal structur...

  14. Small asteroid system evolution

    OpenAIRE

    Jacobson, Seth A.

    2014-01-01

    Observations with radar, photometric and direct imaging techniques have discovered that multiple asteroid systems can be divided clearly into a handful of different morphologies, and recently, the discovery of small unbound asteroid systems called asteroid pairs have revolutionized the study of small asteroid systems. Simultaneously, new theoretical advances have demonstrated that solar radiation dictates the evolution of small asteroids with strong implications for asteroid internal structur...

  15. Small Intestine Disorders

    Science.gov (United States)

    ... disease Crohn's disease Infections Intestinal cancer Intestinal obstruction Irritable bowel syndrome Ulcers, such as peptic ulcer Treatment of disorders of the small intestine depends on the cause.

  16. Small Animal Care.

    Science.gov (United States)

    Livesey, Dennis W.; Fong, Stephen

    This small animal care course guide is designed for students who will be seeking employment in veterinary hospitals, kennels, grooming shops, pet shops, and small-animal laboratories. The guide begins with an introductory section that gives the educational philosophy of the course, job categories and opportunities, units of instruction required…

  17. Small Schools, Big Future

    Science.gov (United States)

    Halsey, R. John

    2011-01-01

    Historically, small schools have played a very important role in the provision of schooling in Australia. Numerically, using an enrollment of 200 or less, small schools represent approximately 45% of the schools in Australia. Population growth and the consequences of this, in particular for food production, water and energy, mean that the…

  18. Hume = Small Hume

    OpenAIRE

    Ketland, Jeffrey

    2002-01-01

    We can modify Hume’s Principle in the same manner that George Boolos suggested for modifying Frege’s Basic Law V. This leads to the principle Small Hume. Then, we can show that Small Hume is interderivable with Hume’s Principle.

  19. Small School Reform

    Directory of Open Access Journals (Sweden)

    Carroll E. Bronson

    2013-05-01

    Full Text Available This qualitative ethnographic case study explored the evolution of a public urban high school in its 3rd year of small school reform. The study focused on how the high school proceeded from its initial concept, moving to a small school program, and emerging as a new small high school. Data collection included interviews, observations, and document review to develop a case study of one small high school sharing a multiplex building. The first key finding, “Too Many Pieces, Not Enough Glue,” revealed that the school had too many new programs starting at once and they lacked a clear understanding of their concept and vision for their new small school, training on the Montessori philosophies, teaching and learning in small schools, and how to operate within a teacher-cooperative model. The second key finding, “A Continuous Struggle,” revealed that the shared building space presented problems for teachers and students. District policies remain unchanged, resulting in staff and students resorting to activist approaches to get things done. These findings offer small school reform leaders suggestions for developing and sustaining a small school culture and cohesion despite the pressures to revert back to top-down, comprehensive high school norms.

  20. IBM Small Business Survey.

    Science.gov (United States)

    International Business Machines Corp., Armonk, NY.

    A telephone survey conducted March 15-22, 1991, examined how small businesses are currently performing. Interviewees were 400 small business owners randomly selected from a Dun and Bradstreet list of companies with 50 or fewer employees. Major findings were as follows: (1) owners were survivors, highly confident in their own abilities, and…

  1. Small Wind Information (Postcard)

    Energy Technology Data Exchange (ETDEWEB)

    2011-08-01

    The U.S. Department of Energy's Wind Powering America initiative maintains a website section devoted to information about small wind turbines for homeowners, ranchers, and small businesses. This postcard is a marketing piece that stakeholders can provide to interested parties; it will guide them to this online resource.

  2. Small business & employment

    NARCIS (Netherlands)

    Lieshout, Harm van

    2015-01-01

    Understanding SMEs is essential to our aspired succes as an economic partner. Small enterprises are not small big enterprises, and differ substantially among them The key ingredient to our help from education remains the education of a new highly skilled generation of workers … and entrepreneurs.

  3. Small Group Inquiry.

    Science.gov (United States)

    Koller, Martin M.

    Learning in small groups is a practical way to bring about behavior change. The inquiry learning process is perceived to be the most natural and scientific way of learning. Skills developed include those of problem-solving task analysis, decision-making, value formation and adaptability. The art of small group interaction is developed. Factual…

  4. Small GTPases and cilia.

    Science.gov (United States)

    Li, Yujie; Hu, Jinghua

    2011-01-01

    Small GTPases are key molecular switches that bind and hydrolyze GTP in diverse membrane- and cytoskeleton-related cellular processes. Recently, mounting evidences have highlighted the role of various small GTPases, including the members in Arf/Arl, Rab, and Ran subfamilies, in cilia formation and function. Once overlooked as an evolutionary vestige, the primary cilium has attracted more and more attention in last decade because of its role in sensing various extracellular signals and the association between cilia dysfunction and a wide spectrum of human diseases, now called ciliopathies. Here we review recent advances about the function of small GTPases in the context of cilia, and the correlation between the functional impairment of small GTPases and ciliopathies. Understanding of these cellular processes is of fundamental importance for broadening our view of cilia development and function in normal and pathological states and for providing valuable insights into the role of various small GTPases in disease processes, and their potential as therapeutic targets.

  5. SmallSat Database

    Science.gov (United States)

    Petropulos, Dolores; Bittner, David; Murawski, Robert; Golden, Bert

    2015-01-01

    The SmallSat has an unrealized potential in both the private industry and in the federal government. Currently over 70 companies, 50 universities and 17 governmental agencies are involved in SmallSat research and development. In 1994, the U.S. Army Missile and Defense mapped the moon using smallSat imagery. Since then Smart Phones have introduced this imagery to the people of the world as diverse industries watched this trend. The deployment cost of smallSats is also greatly reduced compared to traditional satellites due to the fact that multiple units can be deployed in a single mission. Imaging payloads have become more sophisticated, smaller and lighter. In addition, the growth of small technology obtained from private industries has led to the more widespread use of smallSats. This includes greater revisit rates in imagery, significantly lower costs, the ability to update technology more frequently and the ability to decrease vulnerability of enemy attacks. The popularity of smallSats show a changing mentality in this fast paced world of tomorrow. What impact has this created on the NASA communication networks now and in future years? In this project, we are developing the SmallSat Relational Database which can support a simulation of smallSats within the NASA SCaN Compatability Environment for Networks and Integrated Communications (SCENIC) Modeling and Simulation Lab. The NASA Space Communications and Networks (SCaN) Program can use this modeling to project required network support needs in the next 10 to 15 years. The SmallSat Rational Database could model smallSats just as the other SCaN databases model the more traditional larger satellites, with a few exceptions. One being that the smallSat Database is designed to be built-to-order. The SmallSat database holds various hardware configurations that can be used to model a smallSat. It will require significant effort to develop as the research material can only be populated by hand to obtain the unique data

  6. Small Vehicle Launch Platform

    Science.gov (United States)

    2000-09-19

    the art will appreciate that release 21 mechanisms 41 can be a spring-loaded release pin with a lanyard 22 pull initiated by an actuator mechanism or...an explosive squib 23 which breaks the attachment latching on the small UUV. Whatever 1 release mechanism is used, it is controlled by the host...carries four small 1 UUV’s, it will be understood that, depending on the size of the 3 small UUV’s employed, greater or fewer numbers of UUV’s can be 4

  7. Small scale optics

    CERN Document Server

    Yupapin, Preecha

    2013-01-01

    The behavior of light in small scale optics or nano/micro optical devices has shown promising results, which can be used for basic and applied research, especially in nanoelectronics. Small Scale Optics presents the use of optical nonlinear behaviors for spins, antennae, and whispering gallery modes within micro/nano devices and circuits, which can be used in many applications. This book proposes a new design for a small scale optical device-a microring resonator device. Most chapters are based on the proposed device, which uses a configuration know as a PANDA ring resonator. Analytical and nu

  8. Modelling Ser129 phosphorylation inhibits membrane binding of pore-forming alpha-synuclein oligomers.

    Directory of Open Access Journals (Sweden)

    Georg Sebastian Nübling

    Full Text Available BACKGROUND: In several neurodegenerative diseases, hyperphosphorylation at position Ser129 is found in fibrillar deposits of alpha-synuclein (asyn, implying a pathophysiological role of asyn phosphorylation in neurodegeneration. However, recent animal models applying asyn phosphorylation mimics demonstrated a protective effect of phosphorylation. Since metal-ion induced asyn oligomers were identified as a potential neurotoxic aggregate species with membrane pore-forming abilities, the current study was undertaken to determine effects of asyn phosphorylation on oligomer membrane binding. METHODS: We investigated the influence of S129 phosphorylation on interactions of metal-ion induced asyn oligomers with small unilamellar lipid vesicles (SUV composed of POPC and DPPC applying the phosphorylation mimic asyn129E. Confocal single-particle fluorescence techniques were used to monitor membrane binding at the single-particle level. RESULTS: Binding of asyn129E monomers to gel-state membranes (DPPC-SUV is slightly reduced compared to wild-type asyn, while no interactions with membranes in the liquid-crystalline state (POPC-SUV are seen for both asyn and asyn129E. Conversely, metal-ion induced oligomer formation is markedly increased in asyn129E. Surprisingly, membrane binding to POPC-SUV is nearly absent in Fe(3+ induced asyn129E oligomers and markedly reduced in Al(3+ induced oligomers. CONCLUSION: The protective effect of pseudophosphorylation seen in animal models may be due to impeded oligomer membrane binding. Phosphorylation at Ser129 may thus have a protective effect against neurotoxic asyn oligomers by preventing oligomer membrane binding and disruption of the cellular electrophysiological equilibrium. Importantly, these findings put a new complexion on experimental pharmaceutical interventions against POLO-2 kinase.

  9. Small Intestine Cancer Treatment

    Science.gov (United States)

    ... intestine . The digestive system removes and processes nutrients ( vitamins , minerals , carbohydrates , fats, proteins , and water) from foods ... a microscope to see whether they contain cancer. Bypass : Surgery to allow food in the small intestine ...

  10. Small Mammal Trapping 2003

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Small mammal traps were placed in the Baring division and in the Edmunds division of Moosehom National Wildlife Refuge. There were a total of 98 traps set for up to...

  11. Small bowel bacterial overgrowth

    Science.gov (United States)

    ... Surgical procedures that create a loop of small intestine where excess bacteria can grow. An example is a Billroth II type of stomach removal ( gastrectomy ). Some cases of irritable bowel syndrome (IBS).

  12. Small - Display Cartography

    DEFF Research Database (Denmark)

    Nissen, Flemming; Hvas, Anders; Münster-Swendsen, Jørgen

    This report comprises the work carried out in the work-package of small display cartography. The work-package has aimed at creating a general framework for the small-display cartography. A solid framework facilitates an increased use of spatial data in mobile devices - thus enabling, together...... with the rapidly evolving positioning techniques, a new category of position-dependent, map-based services to be introduced. The report consists of the following parts: Part I: Categorization of handheld devices, Part II: Cartographic design for small-display devices, Part III: Study on the GiMoDig Client ? Portal...... Service Communication and finally, Part IV: Concluding remarks and topics for further research on small-display cartography. Part II includes a separate Appendix D consisting of a cartographic design specification. Part III includes a separate Appendix C consisting of a schema specification, a separate...

  13. Small public private partnerships

    DEFF Research Database (Denmark)

    Koch, Christian; Jensen, Jesper Ole

    2009-01-01

    by the authorities, which recommend sizes over 13,5 million € (100 million DKr). PPP is here understood as Design, Build, Finance and Operate projects. The paper shows, when looking at Germany, Italy and United Kingdom, that small PPP (below 13,5 million €) are widespread in two investigated countries; United...... Kingdom and Italy, whereas German projects are still emerging. Quantitative material on small PPP in Italy and UK shows no lower limit in size for these established PPPs. This apparent paradox is then qualitatively investigated. Only small projects are investigated, and these seem largely to be sound...... businesses and represent operable units for the clients and citizens. Cases are focused within education and healthcare. The analysis suggests that another type of economy apparently is in play. It is thus characteristic within education projects in UK that the largest portion of small PPPs are of a size...

  14. Small intestine (image)

    Science.gov (United States)

    The small intestine is the portion of the digestive system most responsible for absorption of nutrients from food into the bloodstream. The pyloric sphincter governs the passage of partly digested food ...

  15. Impact on Small Mammals

    African Journals Online (AJOL)

    abundance and diversity of the small mammal community on burnt and unbumt habitats of the area using .... Captured animals were shaken gently ..... Wetlands Management Project: Environ- ... ofrodents, SwedishNatural Science Research.

  16. Small Satellite Transporter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The primary objective is to determine whether this small satellite transporter is capable of transporting at least four 6U CubeSats is possible for a given set of...

  17. Small simple impact craters

    CERN Document Server

    Sparavigna, Amelia Carolina

    2010-01-01

    The paper discusses some examples of image processing applied to improve optical satellite imagery of small craters (Kamil, Veevers, Haviland). The examples show that image processing can be quite useful for further in-situ researches, because the resultant imagery helps to have a better picture of the crater shape and of the distribution of debris about it. The paper is also disclosing an interesting underwater structure, with shape and size of a small crater, located on the coast-line of Sudan.

  18. Small test SDHW systems

    DEFF Research Database (Denmark)

    Vejen, Niels Kristian

    1999-01-01

    Three small test SDHW systems was tested in a laboratory test facility.The three SDHW systems where all based on the low flow principe and a mantle tank but the design of the systems where different.......Three small test SDHW systems was tested in a laboratory test facility.The three SDHW systems where all based on the low flow principe and a mantle tank but the design of the systems where different....

  19. Neptune's small satellites

    Science.gov (United States)

    Thomas, P.

    1992-04-01

    The small satellites of Neptune and other planets discovered during the Voyager 2 mission are discussed in terms of their composition and relationship to the planetary systems. The satellite Proteus is described in terms of its orbit, five other satellites are described, and they are compared to ther small satellites and systems. Neptune's satellites are hypothesized to be related to the ring system, and the satellite Galatea is related to the confinement of the rings.

  20. Small business & employment

    OpenAIRE

    Lieshout, Harm van

    2015-01-01

    Understanding SMEs is essential to our aspired succes as an economic partner. Small enterprises are not small big enterprises, and differ substantially among them The key ingredient to our help from education remains the education of a new highly skilled generation of workers … and entrepreneurs. Entrepreneurs do not necessarily want to be employers, and are not necessarily good at it. But to ensure a healthy life in a healthy business, they need to be.

  1. Small test SDHW systems

    DEFF Research Database (Denmark)

    Vejen, Niels Kristian

    1999-01-01

    Three small test SDHW systems was tested in a laboratory test facility.The three SDHW systems where all based on the low flow principe and a mantle tank but the design of the systems where different.......Three small test SDHW systems was tested in a laboratory test facility.The three SDHW systems where all based on the low flow principe and a mantle tank but the design of the systems where different....

  2. Small-x physics

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, A.H. [Columbia Univ., New York, NY (United States). Dept. of Physics

    1997-06-01

    After a brief review of the kinematics of deep inelastic lepton-proton scattering, the parton model is described. Small-x behavior coming from DGLAP evolution and from BFKL evolution is discussed, and the two types of evolution are contrasted and compared. Then a more detailed discussion of BFKL dynamics is given. The phenomenology of small-x physics is discussed with an emphasis on ways in which BFKL dynamics may be discussed and measured. 45 refs., 12 figs.

  3. SMALL SCALE MORPHODYNAMICAL MODELLING

    Institute of Scientific and Technical Information of China (English)

    D. Ditschke; O. Gothel; H. Weilbeer

    2001-01-01

    Long term morphological simulations using complete coupled models lead to very time consuming computations. Latteux (1995) presented modelling techniques developed for tidal current situations in order to reduce the computational effort. In this paper the applicability of such methods to small scale problems is investigated. It is pointed out that these methods can be transferred to small scale problems using the periodicity of the vortex shedding process.

  4. How small is a small cloud?

    Directory of Open Access Journals (Sweden)

    I. Koren

    2008-07-01

    Full Text Available The interplay between clouds and aerosols and their contribution to the radiation budget is one of the largest uncertainties of climate change. Most work to date has separated cloudy and cloud-free areas in order to evaluate the individual radiative forcing of aerosols, clouds, and aerosol effects on clouds.

    Here we examine the size distribution and the optical properties of small, sparse cumulus clouds and the associated optical properties of what is considered a cloud-free atmosphere within the cloud field. We show that any separation between clouds and cloud free atmosphere will incur errors in the calculated radiative forcing.

    The nature of small cumulus cloud size distributions suggests that at any resolution, a significant fraction of the clouds are missed, and their optical properties are relegated to the apparent cloud-free optical properties. At the same time, the cloudy portion incorporates significant contribution from non-cloudy pixels.

    We show that the largest contribution to the total cloud reflectance comes from the smallest clouds and that the spatial resolution changes the apparent energy flux of a broken cloudy scene. When changing the resolution from 30 m to 1 km (Landsat to MODIS the average "cloud-free" reflectance at 1.65 μm increases from 0.0095 to 0.0115 (>20%, the cloud reflectance decreases from 0.13 to 0.066 (~50%, and the cloud coverage doubles, resulting in an important impact on climate forcing estimations. The apparent aerosol forcing is on the order of 0.5 to 1 Wm−2 per cloud field.

  5. MINERVA: Small Planets from Small Telescopes

    Science.gov (United States)

    Wittenmyer, Robert A.; Johnson, John Asher; Wright, Jason; McCrady, Nate; Swift, Jonathan; Bottom, Michael; Plavchan, Peter; Riddle, Reed; Muirhead, Philip S.; Herzig, Erich; Myles, Justin; Blake, Cullen H.; Eastman, Jason; Beatty, Thomas G.; Lin, Brian; Zhao, Ming; Gardner, Paul; Falco, Emilio; Criswell, Stephen; Nava, Chantanelle; Robinson, Connor; Hedrick, Richard; Ivarsen, Kevin; Hjelstrom, Annie; Vera, Jon De; Szentgyorgyi, Andrew

    2015-09-01

    The Kepler mission has shown that small planets are extremely common. It is likely that nearly every star in the sky hosts at least one rocky planet. We just need to look hard enough-but this requires vast amounts of telescope time. MINERVA (MINiature Exoplanet Radial Velocity Array) is a dedicated exoplanet observatory with the primary goal of discovering rocky, Earth-like planets orbiting in the habitable zone of bright, nearby stars. The MINERVA team is a collaboration among UNSW Australia, Harvard-Smithsonian Center for Astrophysics, Penn State University, University of Montana, and the California Institute of Technology. The four-telescope MINERVA array will be sited at the F.L. Whipple Observatory on Mt Hopkins in Arizona, USA. Full science operations will begin in mid-2015 with all four telescopes and a stabilised spectrograph capable of high-precision Doppler velocity measurements. We will observe ~100 of the nearest, brightest, Sun-like stars every night for at least five years. Detailed simulations of the target list and survey strategy lead us to expect new low-mass planets.

  6. Small Island Visitor Attractions

    Directory of Open Access Journals (Sweden)

    Haven Allahar

    2015-03-01

    Full Text Available This article proposes a process framework for developing and managing visitor attractions (VA in small island developing states with Trinidad and Tobago, a two-island state in the Caribbean, as the case study. An extensive literature review was conducted, supported by field observations, individual depth interviews, and small and large focus group meetings. The process framework identified four sets of processes: national policy formulation and legislation; inventory, classification, evaluation, and ranking of VA; general operations management involving project management activities; and site specific activities of development, operations, and maintenance. The value of the framework lies in the fact that no similar framework applicable to small islands was covered in the literature and validation was obtained from a panel of experts and a cross section of tourism stakeholders in Tobago.

  7. Small hydroelectric engineering practice

    CERN Document Server

    Leyland, Bryan

    2014-01-01

    Small Hydroelectric Engineering Practice is a comprehensive reference book covering all aspects of identifying, building, and operating hydroelectric schemes between 500 kW and 50 MW. In this range of outputs there are many options for all aspects of the scheme and it is very important that the best options are chosen.As small hydroelectric schemes are usually built against a limited budget it is extremely important that the concept design is optimum and every component is designed to maximise the benefi t and minimise the cost. As operating costs are often a high proportion of the income it i

  8. Small-Gap Flows

    Science.gov (United States)

    1984-04-01

    34’OF CALIFORNIA# BERKELEY, CA 5.1720 ft (45 642-141 SMALL- GAP FLOWS BY E. 0. TUCK REPORT No. NAUE 84-1 CONTRACT N00014-84-K-OU26 APRIL i984...Mechanics, 41 (1970) 769-792. 11 3. Shallow-Water Waves at Discontinuities Shallow-water waves represent perhaps the prototype small- gap flow , the...solving (4.4) we need "initial" conditions at the starting station z = 0, and "exit" conditions at the station z = L where the gap flow merges with the

  9. How Small are Small Stars Really?

    Science.gov (United States)

    2002-11-01

    VLT Interferometer Measures the Size of Proxima Centauri and Other Nearby Stars [1] Summary At a distance of only 4.2 light-years, Proxima Centauri is the nearest star to the Sun currently known [2]. It is visible as an 11-magnitude object in the southern constellation of Centaurus and is the faintest member of a triple system, together with Alpha Centauri , the brightest (double) star in this constellation. Proxima Centauri is a very-low-mass star, in fact barely massive enough to burn hydrogen to helium in its interior. It is about seven times smaller than the Sun, and the surface temperature is "only" about 3000 degrees, about half of that of our own star. Consequently, it is also much fainter - the intrinsic brightness is only 1/150th of that of our Sun. Low-mass stars are very interesting objects , also because the physical conditions in their interiors have much in common with those of giant planets, like Jupiter in our solar system. A determination of the sizes of the smallest stars has been impossible until now because of their general faintness and lack of adequate instrumentation. However, astronomers have long been keen to move forward in this direction, since such measurements would provide indirect, crucial information about the behaviour of matter under extreme conditions. When the first observations with the VLT Interferometer (VLTI), combining the light from two of the 8.2-m VLT Unit Telescopes (ANTU and MELIPAL), were made one year ago ( ESO PR 23/01 ), interferometric measurements were also obtained of Proxima Centauri . They formed part of the VLTI commissioning and the data were soon released to the ESO community, cf. the special website. Now, an international team of astronomers from Switzerland, France and ESO/Chile has successfully analysed these observations by means of newly developed, advanced software. For the first time ever, they obtained a highly accurate measurement of the size of such a small star . Three other small stars were also

  10. Imaging the small bowel.

    LENUS (Irish Health Repository)

    Murphy, Kevin P

    2014-03-01

    Radiologic investigations continue to play a pivotal role in the diagnosis of pathologic conditions of the small intestine despite enhancement of capsule endoscopy and double-balloon endoscopy. Imaging techniques continue to evolve and new techniques in MRI in particular, are being developed.

  11. Light within small particles

    Energy Technology Data Exchange (ETDEWEB)

    Iati, Maria Antonia [Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Universita di Messina, Salita Sperone, 31 - 98166 Messina (Italy)]. E-mail: maiati@unime.it; Saija, Rosalba [Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Universita di Messina, Salita Sperone, 31 - 98166 Messina (Italy); Giusto, Arianna [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Denti, Paolo [Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Universita di Messina, Salita Sperone, 31 - 98166 Messina (Italy); Borghese, Ferdinando [Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Universita di Messina, Salita Sperone, 31 - 98166 Messina (Italy); Cecchi-Pestellini, Cesare [Osservatorio Astronomico di Cagliari, Strada n.54, Loc. Poggio dei Pini, 09012 Capoterra (CA) (Italy)

    2006-07-15

    We calculate the energy density distribution in the ultraviolet within small spheres containing concentric cavities, aimed at simulating interstellar dust grains. We explore the dependence on chemical composition by progressively changing, in an arbitrary way, the refractive index of the sphere material. We conclude that a significant fraction of the energy of the impinging radiation is trapped throughout the particle interior.

  12. small Cell Lung Cancer

    African Journals Online (AJOL)

    treatment response in a non-small cell lung cancer (NSCLC). Methodology: A single-center ..... groupings in the forthcoming (7th) edition of the TNM. Classification of ... overall survival in patients with metastatic colorectal cancer. J Clin Oncol ...

  13. Small Modular Biomass Systems

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-12-01

    This fact sheet provides information about modular biomass systems. Small modular biomass systems can help supply electricity to rural areas, businesses, and the billions of people who live without power worldwide. These systems use locally available biomass fuels such as wood, crop waste, animal manures, and landfill gas.

  14. Small bowel resection - discharge

    Science.gov (United States)

    ... that rubs against your wound while it is healing. Use a thin gauze pad over it to protect it if needed. If you have an ileostomy, follow care instructions from your provider. Diet Eat small amounts of food several times a day. DO NOT eat 3 ...

  15. Small holding circles

    CERN Document Server

    Fruchard, Augustin

    2010-01-01

    A circle C holds a convex body K if C does not meet the interior of K and if there does not exist any euclidean displacement which moves C as far as desired from K, avoiding the interior of K. The purpose of this note is to explore how small can be a holding circle.

  16. Small Group Research

    Science.gov (United States)

    McGrath, Joseph E.

    1978-01-01

    Summarizes research on small group processes by giving a comprehensive account of the types of variables primarily studied in the laboratory. These include group structure, group composition, group size, and group relations. Considers effects of power, leadership, conformity to social norms, and role relationships. (Author/AV)

  17. On a small Monacanthus

    NARCIS (Netherlands)

    Popta, C.M.L.

    1900-01-01

    Among fishes sent to the Leyden Museum by the late Dr. Bleeker, I found a Monacanthus which I cannot bring to one of the described species. It is a small specimen and it may be young, it is however interesting on account of its beautiful markings. When later on more or larger specimens will be found

  18. Deburring small intersecting holes

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, L.K.

    1980-08-01

    Deburring intersecting holes is one of the most difficult deburring tasks faced by many industries. Only 14 of the 37 major deburring processes are applicable to most intersecting hole applications. Only five of these are normally applicable to small or miniature holes. Basic process capabilities and techniques used as a function of hole sizes and intersection depths are summarized.

  19. Extrapulmonary small cell carcinoma.

    NARCIS (Netherlands)

    Heijden, E. van der; Heijdra, Y.F.

    2005-01-01

    This article reviews the recent literature on extrapulmonary small cell carcinomas. Until now, only four cases have been published in the English literature, two of those in the Southern Medical Journal. Sharing the information on diagnosis and treatment of these cases is important for better unders

  20. Small Public Library Management

    Science.gov (United States)

    Pearlmutter, Jane; Nelson, Paul

    2012-01-01

    Anyone at the helm of a small public library knows that every little detail counts. But juggling the responsibilities that are part and parcel of the job is far from easy. Finally, here's a handbook that includes everything administrators need to keep a handle on library operations, freeing them up to streamline and improve how the organization…

  1. Small and Magical

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Ant genome study offers promising evidence in medical and anti-aging research While children often love observing ants happily for hours, grownups are more likely to ignore these small creatures. Some scientists, however, show greater interest in ants than children do.

  2. Small Bowel Lymphangioma

    Directory of Open Access Journals (Sweden)

    Shou-jiang Tang

    2014-01-01

    Conclusions: Small bowel lymphangiomas can cause gross or occult GI bleeding, anemia, abdominal pain, and/or obstruction. Endoscopists should be aware of this rare tumor and its unique endoscopic features. The optimal treatment is radical excision, since incomplete resection may lead to recurrence. Argon plasma coagulation or polypectomy have been used to achieve endoscopic ablation and palliation of GI bleeding.

  3. 78 FR 11745 - Small Business Size Regulations, Small Business Innovation Research (SBIR) Program and Small...

    Science.gov (United States)

    2013-02-20

    ... / Wednesday, February 20, 2013 / Rules and Regulations#0;#0; ] SMALL BUSINESS ADMINISTRATION 13 CFR Part 121 RIN 3245-AG46 Small Business Size Regulations, Small Business Innovation Research (SBIR) Program and Small Business Technology Transfer (STTR) Program; Correction AGENCY: U.S. Small Business...

  4. Small Multiples with Gaps.

    Science.gov (United States)

    Meulemans, Wouter; Dykes, Jason; Slingsby, Aidan; Turkay, Cagatay; Wood, Jo

    2017-01-01

    Small multiples enable comparison by providing different views of a single data set in a dense and aligned manner. A common frame defines each view, which varies based upon values of a conditioning variable. An increasingly popular use of this technique is to project two-dimensional locations into a gridded space (e.g. grid maps), using the underlying distribution both as the conditioning variable and to determine the grid layout. Using whitespace in this layout has the potential to carry information, especially in a geographic context. Yet, the effects of doing so on the spatial properties of the original units are not understood. We explore the design space offered by such small multiples with gaps. We do so by constructing a comprehensive suite of metrics that capture properties of the layout used to arrange the small multiples for comparison (e.g. compactness and alignment) and the preservation of the original data (e.g. distance, topology and shape). We study these metrics in geographic data sets with varying properties and numbers of gaps. We use simulated annealing to optimize for each metric and measure the effects on the others. To explore these effects systematically, we take a new approach, developing a system to visualize this design space using a set of interactive matrices. We find that adding small amounts of whitespace to small multiple arrays improves some of the characteristics of 2D layouts, such as shape, distance and direction. This comes at the cost of other metrics, such as the retention of topology. Effects vary according to the input maps, with degree of variation in size of input regions found to be a factor. Optima exist for particular metrics in many cases, but at different amounts of whitespace for different maps. We suggest multiple metrics be used in optimized layouts, finding topology to be a primary factor in existing manually-crafted solutions, followed by a trade-off between shape and displacement. But the rich range of possible

  5. Small Engine & Accessory Test Area

    Data.gov (United States)

    Federal Laboratory Consortium — The Small Engine and Accessories Test Area (SEATA) facilitates testaircraft starting and auxiliary power systems, small engines and accessories. The SEATA consists...

  6. Small Wind Energy Systems

    DEFF Research Database (Denmark)

    2017-01-01

    This chapter intends to serve as a brief guide when someone is considering the use of wind energy for small power applications. It is discussed that small wind energy systems act as the major energy source for residential or commercial applications, or how to make it part of a microgrid...... as a distributed generator. In this way, sources and loads are connected in such a way to behave as a renewable dispatch center. With this regard, non-critical loads might be curtailed or shed during times of energy shortfall or periods of high costs of energy production. If such a wind energy system is connected...... to the public distibutor, it can serve as a backup system, as a non-interruptible power supply (with storage aggregation), provide low-voltage support, or give a clean surplus of energy transferred to the public network under economical and technological basis. In this chapter, several factors are also...

  7. Aerodynamics of Small Vehicles

    Science.gov (United States)

    Mueller, Thomas J.

    In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.

  8. Small Business Innovations

    Science.gov (United States)

    1992-01-01

    The purpose of QASE RT is to enable system analysts and software engineers to evaluate performance and reliability implications of design alternatives. The program resulted from two Small Business Innovation Research (SBIR) projects. After receiving a description of the system architecture and workload from the user, QASE RT translates the system description into simulation models and executes them. Simulation provides detailed performance evaluation. The results of the evaluations are service and response times, offered load and device utilizations and functional availability.

  9. Plant Mobile Small RNAs

    OpenAIRE

    Dunoyer, Patrice; Melnyk, Charles; Molnar, Attila; Slotkin, R Keith

    2013-01-01

    In plants, RNA silencing is a fundamental regulator of gene expression, heterochromatin formation, suppression of transposable elements, and defense against viruses. The sequence specificity of these processes relies on small noncoding RNA (sRNA) molecules. Although the spreading of RNA silencing across the plant has been recognized for nearly two decades, only recently have sRNAs been formally demonstrated as the mobile silencing signals. Here, we discuss the various types of mobile sRNA mol...

  10. Small Generation Gap

    Institute of Scientific and Technical Information of China (English)

    JANE SHAW

    1994-01-01

    IT was while I was making milk for my son that I discovered the generation gap between us. A little thing of two years and three months, my son stood on a big chair I brought him and joined me to make milk. Holding a small spoon in his plump little hand, he scooped flour out of a jar and poured it into the feeding bottle and then scooped milk powder and

  11. Small and Magical

    Institute of Scientific and Technical Information of China (English)

    TANG YUANKAI

    2011-01-01

    While children often love observing ants happily for hours,grown-ups are more likely to ignore these small creatures.Some scientists,however,show greater interest in ants than children do.One of them is Zhang Guojie,Associate Director of the Bioinformatics Center and Leader of Genome Projects in BGI.BG1 is China's largest genome and bioinformatics analysis center in Shenzhen,in south China's Guangdong Province.

  12. When small is beautiful. Boom time for small hydro?

    Energy Technology Data Exchange (ETDEWEB)

    Osborne, John

    2002-08-01

    Although small hydropower projects generally contribute a small proportion of most nations' electricity needs their importance often exceeds their size. The author, a freelance industrial journalist considers prospects for small hydro, how such schemes are benefiting communities throughout the world and why some countries are more successfully using small hydro than others. (Author)

  13. DEVELOPMENT OF SMALL INJECTION MOULDING MACHINE FOR FORMING SMALL PLASTIC ARTICLES FOR SMALL-SCALE INDUSTRIES

    OpenAIRE

    OYETUNJI, A.

    2010-01-01

    Development of small injection moulding machine for forming small plastic articles in small-scale industries was studied. This work which entailed design, construction and test small injection moulding machine that was capable of forming small plastic articles by injecting molten resins into a closed, cooled mould, where it solidifies to give the desired products was developed. The machine was designed and constructed to work as a prototype for producing very small plastic components. Design ...

  14. Origins of extreme boundary lubrication by phosphatidylcholine liposomes.

    Science.gov (United States)

    Sorkin, Raya; Kampf, Nir; Dror, Yael; Shimoni, Eyal; Klein, Jacob

    2013-07-01

    Phosphatidylcholine (PC) vesicles have been shown to have remarkable boundary lubricating properties under physiologically-high pressures. Here we carry out a systematic study, using a surface force balance, of the normal and shear (frictional) forces between two opposing surfaces bearing different PC vesicles across water, to elucidate the origin of these properties. Small unilamellar vesicles (SUVs, diameters lubrication ability improves markedly with increasing acyl chain length, and correlates strongly with the liposomes' structural integrity on the substrate surface: DSPC-SUVs were stable on the surface, and provided extremely efficient lubrication (friction coefficient μ ≈ 10(-4)) at room temperature at pressures up to at least 18 MPa. DMPC-SUVs ruptured following adsorption, providing poor high-pressure lubrication, while DPPC-SUVs behavior was intermediate between the two. These results can be well understood in terms of the hydration-lubrication paradigm, but suggest that an earlier conjecture, that highly-efficient lubrication by PC-SUVs depended simply on their being in the SO rather than in the liquid-disordered phase, should be more nuanced. Our results indicate that the resistance of the SUVs to mechanical deformation and rupture is the dominant factor in determining their overall boundary lubrication efficiency in our system.

  15. Ecology in Small Aquatic Ecosystems

    DEFF Research Database (Denmark)

    Andersen, Mikkel René

    Small ecosystems are many-fold more abundant than their larger counterparts. Both on regional and global scale small lakes outnumber medium and large lakes and account for a much larger surface area. Small streams are also far more common than rivers. Despite their abundance small ecosystems are ...

  16. Ecology in Small Aquatic Ecosystems

    DEFF Research Database (Denmark)

    Andersen, Mikkel René

    Small ecosystems are many-fold more abundant than their larger counterparts. Both on regional and global scale small lakes outnumber medium and large lakes and account for a much larger surface area. Small streams are also far more common than rivers. Despite their abundance small ecosystems are ...

  17. The small library manager's handbook

    CERN Document Server

    Graves, Alice

    2014-01-01

    The Small Library Manager's Handbook is for librarians working in all types of small libraries. It covers the everyday nuts-and-bolts operations that all librarians must perform. This handbook, written by experts who are small librarians themselves, will help all small librarians to do multiple jobs at the same time.

  18. The Small Mars System

    Science.gov (United States)

    Fantino, E.; Grassi, M.; Pasolini, P.; Causa, F.; Molfese, C.; Aurigemma, R.; Cimminiello, N.; de la Torre, D.; Dell'Aversana, P.; Esposito, F.; Gramiccia, L.; Paudice, F.; Punzo, F.; Roma, I.; Savino, R.; Zuppardi, G.

    2017-08-01

    The Small Mars System is a proposed mission to Mars. Funded by the European Space Agency, the project has successfully completed Phase 0. The contractor is ALI S.c.a.r.l., and the study team includes the University of Naples ;Federico II;, the Astronomical Observatory of Capodimonte and the Space Studies Institute of Catalonia. The objectives of the mission are both technological and scientific, and will be achieved by delivering a small Mars lander carrying a dust particle analyser and an aerial drone. The former shall perform in situ measurements of the size distribution and abundance of dust particles suspended in the Martian atmosphere, whereas the latter shall demonstrate low-altitude flight in the rarefied planetary environment. The mission-enabling technology is an innovative umbrella-like heat shield, known as IRENE, developed and patented by ALI. The mission is also a technological demonstration of the shield in the upper atmosphere of Mars. The core characteristics of SMS are the low cost (120 M€) and the small size (320 kg of wet mass at launch, 110 kg at landing), features which stand out with respect to previous Mars landers. To comply with them is extremely challenging at all levels, and sets strict requirements on the choice of the materials, the sizing of payloads and subsystems, their arrangement inside the spacecraft and the launcher's selection. In this contribution, the mission and system concept and design are illustrated and discussed. Special emphasis is given to the innovative features and to the challenges faced in the development of the work.

  19. Small Unit Operations

    Science.gov (United States)

    2007-11-02

    best demonstrated value for small (< AA size) lithium - thionyl - chloride batteries (Halpert 1993). Equation (2-3) shows that the solar power...However, this energy den- sity this is only ~ 3 times larger than the demonstrated performance of the best lithium batteries , and the fuel cells are...Units 13 2.2.2 ASIC Capability 15 2.2.3 Power and Size 17 2.2.4 Cost 19 2.3 Power Sources 20 2.3.1 Batteries 21 2.3.2 Solar Augmentation

  20. Plant Mobile Small RNAs

    Science.gov (United States)

    Dunoyer, Patrice; Melnyk, Charles; Molnar, Attila; Slotkin, R. Keith

    2013-01-01

    In plants, RNA silencing is a fundamental regulator of gene expression, heterochromatin formation, suppression of transposable elements, and defense against viruses. The sequence specificity of these processes relies on small noncoding RNA (sRNA) molecules. Although the spreading of RNA silencing across the plant has been recognized for nearly two decades, only recently have sRNAs been formally demonstrated as the mobile silencing signals. Here, we discuss the various types of mobile sRNA molecules, their short- and long-range movement, and their function in recipient cells. PMID:23818501

  1. Small hydro in Africa

    CSIR Research Space (South Africa)

    Jonker Klunne, W

    2011-10-01

    Full Text Available stream_source_info Klunne1_2011.pdf.txt stream_content_type text/plain stream_size 12260 Content-Encoding ISO-8859-1 stream_name Klunne1_2011.pdf.txt Content-Type text/plain; charset=ISO-8859-1 INTERNATIONAL WATER POWER..., only 4 to 7% of the potential for large scale hydropower has been exploited [1,2]. For small and micro scale hydropower this percentage is most probably even lower, although no proper statistics are available. To indicate the low rate...

  2. SmallSat Lab

    Science.gov (United States)

    2014-03-05

    CubeSat. Mr. Alvarez worked with four students on the PCB layout for the solar panels and the construction of the 6U CubeSat mockup . Support for Mr...Hull and Mr. Alvarez was $49k including fringe benefits. !! Purchases: During this time period a license for MatLab software and the Princeton...Satellite ToolBox was purchased using funds from this award. This software adds tremendous capability to the SmallSat Lab by enabling students to analyze

  3. Small changes for works

    Institute of Scientific and Technical Information of China (English)

    Jiarui Wu

    2011-01-01

    The central dogma of molecular biology indicates that genetic information from DNA is transmitted to RNA,and then translated into proteins that play various roles during all physiological and pathological processes.However,most of the proteins have to make small chemical changes on their amino acid chains,so-called post-translational modifications,before they start to work.The collection of four articles in this issue presents timely developments in the area of protein modifications,ranging from how proteins carry out their biological functions based on protein modifications to what are molecular mechanisms of protein modifications.

  4. Small engine technology programs

    Science.gov (United States)

    Niedzwiecki, Richard W.

    1990-01-01

    Described here is the small engine technology program being sponsored at the Lewis Research Center. Small gas turbine research is aimed at general aviation, commuter aircraft, rotorcraft, and cruise missile applications. The Rotary Engine program is aimed at supplying fuel flexible, fuel efficient technology to the general aviation industry, but also has applications to other missions. The Automotive Gas Turbine (AGT) and Heavy-Duty Diesel Transport Technology (HDTT) programs are sponsored by DOE. The Compound Cycle Engine program is sponsored by the Army. All of the programs are aimed towards highly efficient engine cycles, very efficient components, and the use of high temperature structural ceramics. This research tends to be generic in nature and has broad applications. The HDTT, rotary technology, and the compound cycle programs are all examining approaches to minimum heat rejection, or 'adiabatic' systems employing advanced materials. The AGT program is also directed towards ceramics application to gas turbine hot section components. Turbomachinery advances in the gas turbine programs will benefit advanced turbochargers and turbocompounders for the intermittent combustion systems, and the fundamental understandings and analytical codes developed in the research and technology programs will be directly applicable to the system projects.

  5. Problems of Small Debris

    Directory of Open Access Journals (Sweden)

    V. V. Zelentsov

    2015-01-01

    Full Text Available During the exploration of outer space (as of 1/1 2011 6853 was launched spacecraft (SC are successful 6264, representing 95% of the total number of starts. The most intensively exploited space Russia (USSR (3701 starts, 94% successful, USA (2774 starts, 90% successful, China (234 starts, 96% successful and India (89 starts, 90% successful. A small part of running the spacecraft returned to Earth (manned spacecraft and transport, and the rest remained in orbit. Some of them are descended from orbit and burned up in the atmosphere, the rest remained in the OCP and turned into space debris (SD.The composition of the Cabinet is diverse: finish the job spacecraft; boosters and the last stage of launch vehicles left in orbit after SC injection; technological waste arising during the opening drop-down structures and fragments of the destroyed spacecraft. The resulting explosion orbital SD forms ellipsoidal region which orbits blasted object. Then, as a result of precession, is the distribution of objects in orbit explosion exploding spacecraft.The whole Cabinet is divided into two factions: the observed (larger than 100 mm and not observed (less than 100 mm. Observed debris katalogalizirovan and 0.2% of the total number of SD, there was no SD is the bulk - 99.8%.SC meeting working with a fragment observed SD predictable and due to changes in altitude spacecraft avoids a possible meeting. Contact spacecraft with large fragment lead to disaster (which took place at a meeting of the Russian communications satellite "Cosmos-2251" and the American machine "Iridium". Meeting with small SD is not predictable, especially if it was formed by an explosion or collision fragments together. Orbit that KM is not predictable, and the speed can be up to 10 km / s. Meeting with small particle SD no less dangerous for the spacecraft. The impact speed of spacecraft with space debris particles can reach up to 10 ... 15 km / s at such speeds the breakdown probability thin

  6. Small Wind Energy Systems

    DEFF Research Database (Denmark)

    Simoes, Marcelo; Farret, Felix Alberto; Blaabjerg, Frede

    2015-01-01

    devices, and a centralized distribution control. In order to establish a small wind energy system it is important to observe the following: (i) Attending the energy requirements of the actual or future consumers; (ii) Establishing civil liabilities in case of accidents and financial losses due to shortage...... or low quality of energy; (iii) Negotiating collective conditions to interconnect the microgrid with the public network or with other sources of energy that is independent of wind resources; (iv) Establishing a performance criteria of power quality and reliability to end-users, in order to reduce costs...... and guaranteeing an acceptable energy supply. This paper discuss how performance is affected by local conditions and random nature of the wind, power demand profiles, turbine related factors, and presents the technical issues for implementing a self-excited induction generator system, or a permanent magnet based...

  7. [Is allastrim small pox?].

    Science.gov (United States)

    Tiexeira, L A

    2000-01-01

    Between 1910 and 1913, two renowned physicians in the city of Sao Paulo found themselves engaged in a scientific controversy regarding the classification of a disease then assailing the state. Antonio Carini, director of the Instituto Pasteur de Sao Paulo, believed the illness to be small pox, while Emilio Ribas, director of the Servico Sanitario, claimed it was allastrim, or milk pox. The controversy started in the Sociedade de Medicina e Cirurgia but later migrated to other forums and came to incorporate other figures as well. This presentation and discussion of the polemic is meant as a contribution to our understanding of the process by which a scientific consensus is constructed and solidified within the field of the biomedical sciences.

  8. Rolling at small scales

    DEFF Research Database (Denmark)

    Nielsen, Kim L.; Niordson, Christian F.; Hutchinson, John W.

    2016-01-01

    The rolling process is widely used in the metal forming industry and has been so for many years. However, the process has attracted renewed interest as it recently has been adapted to very small scales where conventional plasticity theory cannot accurately predict the material response. It is well....... Metals are known to be stronger when large strain gradients appear over a few microns; hence, the forces involved in the rolling process are expected to increase relatively at these smaller scales. In the present numerical analysis, a steady-state modeling technique that enables convergence without...... dealing with the transient response period is employed. This allows for a comprehensive parameter study. Coulomb friction, including a stick-slip condition, is used as a first approximation. It is found that length scale effects increase both the forces applied to the roll, the roll torque, and thus...

  9. Modular small hydro configuration

    Science.gov (United States)

    1981-09-01

    Smaller sites (those under 750 kilowatts) which previously were not attractive to develop using equipment intended for application at larger scale sites, were the focal point in the conception of a system which utilizes standard industrial components which are generally available within short procurement times. Such components were integrated into a development scheme for sites having 20 feet to 150 feet of head. The modular small hydro configuration maximizes the use of available components and minimizes modification of existing civil works. A key aspect of the development concept is the use of a vertical turbine multistage pump, used in the reverse mode as a hydraulic turbine. The configuration allows for automated operation and control of the hydroelectric facilities with sufficient flexibility for inclusion of potential hydroelectric sites into dispersed storage and generation (DSG) utility grid systems.

  10. Small intestinal transplantation.

    LENUS (Irish Health Repository)

    Quigley, E M

    2012-02-03

    The past few years have witnessed a considerable shift in the clinical status of intestinal transplantation. A great deal of experience has been gained at the most active centers, and results comparable with those reported at a similar stage in the development of other solid-organ graft programs are now being achieved by these highly proficient transplant teams. Rejection and its inevitable associate, sepsis, remain ubiquitous, and new immunosuppressant regimes are urgently needed; some may already be on the near horizon. The recent success of isolated intestinal grafts, together with the mortality and morbidity attendant upon the development of advanced liver disease related to total parenteral nutrition, has prompted the bold proposal that patients at risk for this complication should be identified and should receive isolated small bowel grafts before the onset of end-stage hepatic failure. The very fact that such a suggestion has begun to emerge reflects real progress in this challenging field.

  11. Small particle heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, A.J.

    1978-06-01

    A dispersion of small absorbing particles forms an ideal system to collect radiant energy, transform it to heat, and efficiently transfer the heat to a surrounding fluid. If the heated fluid is a pressurized gas, it can be passed through an expansion turbine to create useful mechanical energy. The most obvious application of this technique is its use in a solar collection system. In this case, the incoming sunlight is used to heat a compressed gas in an engine utilizing a Brayton cycle. The solar collection system may utilize high concentration as provided by a central receiver or parabolic dish, medium concentration from a linear collector, or possibly no concentration using a flat plate collector, if precautions were taken to reduce the heat losses. The same concept may be applied generally to non-solar heat exchangers. These may be of the type used to heat a gas from a combustion source, or in general as a gas to gas heat exchanger. The latter application may be limited to rather high temperature. Each of the above applications is discussed. First, a description of the concept is applied to a solar central-tower system. The general principles are described, including the optical and physical characteristics of the particles, the confinement of the gas-particle mixture, and the system considerations; the latter include the amount and type of particles, the receiver efficiency and the generation of the particles. The same considerations are reviewed for applications to linear trough and flat plate receivers. Finally, the use of small particles in non-solar heat exchangers is considered.

  12. Small rover exploration capabilities

    Science.gov (United States)

    Salotti, Jean-Marc; Laithier, Corentin; Machut, Benoit; Marie, Aurélien; Bruneau, Audrey; Grömer, Gernot; Foing, Bernard H.

    2015-05-01

    For a human mission to the Moon or Mars, an important question is to determine the best strategy for the choice of surface vehicles. Recent studies suggest that the first missions to Mars will be strongly constrained and that only small unpressurized vehicles will be available. We analyze the exploration capabilities and limitations of small surface vehicles from the user perspective. Following the “human centered design” paradigm, the team focused on human systems interactions and conducted the following experiments: - Another member of our team participated in the ILEWG EuroMoonMars 2013 simulation at the Mars Desert Research Station in Utah during the same period of time. Although the possible traverses were restricted, a similar study with analog space suits and quads has been carried out. - Other experiments have been conducted in an old rock quarry close to Bordeaux, France. An expert in the use of quads for all types of terrains performed a demonstration and helped us to characterize the difficulties, the risks and advantages and drawbacks of different vehicles and tools. The vehicles that will be used on the surface of Mars have not been defined yet. Nevertheless, the results of our project already show that using a light and unpressurized vehicle (in the order of 150 kg) for the mobility on the Martian surface can be a true advantage. Part of the study was dedicated to the search for appropriate tools that could be used to make the vehicles easier to handle, safer to use and more efficient in the field to cross an obstacle. The final recommendation is to use winches and ramps, which already are widely used by quad drivers. We report on the extension of the reachable areas if such tools were available. This work has been supported by ILEWG, EuroMoonMars and the Austrian Space Forum (OEWF).

  13. Small-crack test methods

    Science.gov (United States)

    Larsen, James M.; Allison, John E.

    This book contains chapters on fracture mechanics parameters for small fatigue cracks, monitoring small-crack growth by the replication method, measurement of small cracks by photomicroscopy (experiments and analysis), and experimental mechanics of microcracks. Other topics discussed are the real-time measurement of small-crack-opening behavior using an interferometric strain/displacement gage; direct current electrical potential measurement of the growth of small cracks; an ultrasonic method for the measurement of the size and opening behavior of small fatigue cracks; and the simulation of short crack and other low closure loading conditions, utilizing constant K(max) Delta-K-decreasing fatigue crack growth procedures.

  14. Small Business's Big Training Needs.

    Science.gov (United States)

    Kelly, Leslie

    1984-01-01

    Discusses the training needs of small businesses in light of their high failure rate (50 percent). Includes characteristics of successful small businesses, potential training needs, training methods, and topics for seminars. (JOW)

  15. Small intestine contrast injection (image)

    Science.gov (United States)

    ... and throat, through the stomach into the small intestine. When in place, contrast dye is introduced and ... means of demonstrating whether or not the small intestine is normal when abnormality is suspected.

  16. Small Area Fair Market Rent

    Data.gov (United States)

    Department of Housing and Urban Development — Due to the increasing demand for more localized rents for a variety of purposes, HUD is making Small Area FMRs for all metropolitan areas available. Small Area FMRs...

  17. Small intestine aspirate and culture

    Science.gov (United States)

    ... ency/article/003731.htm Small intestine aspirate and culture To use the sharing features on this page, please enable JavaScript. Small intestine aspirate and culture is a lab test to check for infection ...

  18. Formal versus informal small businesses

    African Journals Online (AJOL)

    There is renewed interest in entrepreneurship, business formation and growth. ... acumen, while small formal businesses show higher levels of growth instigated by an ... Small business support strategies should focus on businesses with ...

  19. Entrepreneurship and small business sustainability

    African Journals Online (AJOL)

    Southern African Business Review Volume 14 Number 3 2010. Entrepreneurship and small ... 16Key words: entrepreneurship, small business development, business sustainability, competition ...... Boston, MA: Harvard. Business School Press ...

  20. Globalization, Entrepreneurship and Small Business

    OpenAIRE

    Stan ªtefania Anca

    2012-01-01

    New product innovation often comes from small business. Most the radical inventions of the last century, such as the computer, come from small companies, not large ones. And this will not change. Globalization will continue to modify and mold the environment or small business and entrepreneurship. The competition from abroad places strong pressure on small business in terms of efficiency, price, quality, cost, control, marketing, expertise, customer satisfaction and innovativeness. Globalizat...

  1. Effect of Gd3+ on the colloidal stability of liposomes.

    Science.gov (United States)

    Sabín, Juan; Prieto, Gerardo; Sennato, Simona; Ruso, Juan M; Angelini, Roberta; Bordi, Federico; Sarmiento, Félix

    2006-09-01

    Lanthanide ions such as La3+ and Gd3+ are well known to have large effects on the structure of phospholipid membranes. Unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC) were prepared by sonication method and confirmed by transmission electron microscopy. The effects of concentration of gadolinium ions Gd3+ on DPPC unilamellar vesicles in aqueous media were studied by different techniques. As physical techniques, photon correlation spectroscopy, electrophoretic mobility, and differential scanning calorimetry were used. The theoretical predictions of the colloidal stability of liposomes were followed using the Derjaguin-Landau-Verwey-Overbeek theory. Changes in the size of liposomes and high polydispersities values were observed as Gd3+ concentration increases, suggesting that this cation induces the aggregation of vesicles. Electrophoretic mobility measurements on unilamellar vesicles as a function of Gd3+ ion concentration show that the vesicles adsorb Gd3+ ions. Above Gd3+ concentrations of 0.1 mol dm-3, the zeta potential and light scattering measurements indicate the beginning of aggregation process. For comparison with similar phospholipids, the zeta potential of phosphatidylcholine interacting with Gd3+ was measured, showing an analogous behavior. Differential scanning calorimetry has been used to determine the effect of Gd3+ on the transition temperature (Tc) and on the enthalpy (DeltaHc) associated with the process.

  2. Quality and the Small School.

    Science.gov (United States)

    Hildebrand, Edwin P., Ed.

    The 1965-1968 progress report of the Western States Small Schools Project focuses on the problem and challenge posed by small schools, which have thus far lacked the depth of resources compared to urban schools. The goals of the project are to assist small schools to: (1) provide individualized programs of career selection education; (2) develop…

  3. Small scale sanitation technologies.

    Science.gov (United States)

    Green, W; Ho, G

    2005-01-01

    Small scale systems can improve the sustainability of sanitation systems as they more easily close the water and nutrient loops. They also provide alternate solutions to centrally managed large scale infrastructures. Appropriate sanitation provision can improve the lives of people with inadequate sanitation through health benefits, reuse products as well as reduce ecological impacts. In the literature there seems to be no compilation of a wide range of available onsite sanitation systems around the world that encompasses black and greywater treatment plus stand-alone dry and urine separation toilet systems. Seventy technologies have been identified and classified according to the different waste source streams. Sub-classification based on major treatment methods included aerobic digestion, composting and vermicomposting, anaerobic digestion, sand/soil/peat filtration and constructed wetlands. Potential users or suppliers of sanitation systems can choose from wide range of technologies available and examine the different treatment principles used in the technologies. Sanitation systems need to be selected according to the local social, economic and environmental conditions and should aim to be sustainable.

  4. Small Hydropower in Nigeria

    Institute of Scientific and Technical Information of China (English)

    P.EOKRANEFE; S.OWOLABI

    2002-01-01

    Nigeria is the most populaous black nation in the world. It has an area of 913,072 square kilometres. The country population is about 120 million. There are three major languages, Hausa, Yoruba and Igbo, although there is still more than 380 dialects in local languages. There are large number of household on the African continent that are unelectrified.In Nigeria about 70 million people remain literally in the dark without access to electricity. The majority of these numbers are in the rural areas. This workshop is apt in a number of ways. It is a joint effort between government, private sector, the academic and other practitioners in small hydro power station, it is also a promotion of business and industrial activities as well as development of renewable energy resources. I wish to commend the organizers of this workshop. The focus of the workshop is relevant to the agenda of the Federal Ministry of Power and Steel and aspirations of the Federal Government of Nigeria to provide regular and steady electricity to majority of Nigerians before the end of year 2001.

  5. Small Stirling Cycle Convertors

    Science.gov (United States)

    Penswick, L. Barry; Schreiber, Jeffery

    2005-02-01

    The Stirling convertor concept continues to be a viable potential candidate for various space power applications at electrical power levels ranging from greater than 100 KW to on the order of 10+watts. Various development efforts, both in the past and currently underway, have clearly demonstrated the potential for long operating life of this concept, its high efficiency in comparison to alternative power systems (>50% of Carnot based on electric power out to heat in), and its excellent specific power characteristics. A truly unique attribute of the Stirling convertor is the ability to maintain many of these same advantages at significantly lower electrical power levels (on the order of 1 watt and below). This provides the opportunity for a wider range of potential space power applications and the use of alternative heat sources operating at dramatically lower hot-end temperatures (about 250 °C vs. current values of about 650 °C). An overview of low-power Stirling convertors and related Stirling cooler technology is provided with an emphasis on assessing the technical maturity of this concept's key components at the low power level of interest. A conceptual design of a small, 1-watt (electrical output) Stirling convertor utilizing multiple Low Weight Radioisotope Heater Unit heat sources will be described. Key technical issues in the development of this power level Stirling convertor are discussed.

  6. 48 CFR 970.1907 - Subcontracting with Small Business, Small Disadvantaged Business and Woman-Owned Small Business...

    Science.gov (United States)

    2010-10-01

    ... Business, Small Disadvantaged Business and Woman-Owned Small Business Concerns. 970.1907 Section 970.1907... MANAGEMENT AND OPERATING CONTRACTS Small, Small Disadvantaged and Women-Owned Small Business Concerns 970.1907 Subcontracting with Small Business, Small Disadvantaged Business and Woman-Owned Small...

  7. Small Thermophotovoltaic Prototype Systems

    Science.gov (United States)

    Durisch, Wilhelm; Bitnar, Bernd; von Roth, Fritz; Palfinger, Günther

    2003-01-01

    In an earlier paper [1], we reported on a small grid-connected thermophotovoltaic (TPV) system consisting of an ytterbia mantle emitter and silicon solar cells with 16 % efficiency (under solar irradiance at Standard Test Conditions, STC). The emitter was heated up using a butane burner with a rated thermal power of 1.35 kW (referring to the lower heating value). This system produced an electrical output of 15 W, which corresponds to a thermal to electric (direct current) conversion efficiency of 1.1 %. In the interim, further progress has been made, and significantly higher efficiencies have been achieved. The most important development steps are: 1) The infrared radiation-absorbing water filter between emitter and silicon cells (to protect the cells against overheating and against contact with flue gasses) has been replaced by a suitable glass tube. By doing this, it has been possible to prevent losses of convertible radiation in water. 2) Cell cooling has been significantly improved, in order to reduce cell temperature, and therefore increase conversion efficiency. 3) The shape of the emitter has been changed from spherical to a quasi-cylindrical geometry, in order to obtain a more homogeneous irradiation of the cells. 4) The metallic burner tube, on which the ytterbia emitter was fixed in the initial prototypes, has been replaced by a heat-resistant metallic rod, carrying ceramic discs as emitter holders. This has prevented the oxidation and clogging of the perforated burner tube. 5) Larger reflectors have been used to reduce losses in useful infrared radiation. 6) Smaller cells have been used, to reduce electrical series resistance losses. Applying all these improvements to the basic 1.35 kW prototype, we attained a system efficiency of 1.5 %. By using preheated air for combustion (at approximately 370 °C), 1.8 % was achieved. In a subsequent step, a photocell generator was constructed, consisting of high-efficiency silicon cells (21% STC efficiency). In this

  8. Small angle neutron scattering

    Directory of Open Access Journals (Sweden)

    Cousin Fabrice

    2015-01-01

    Full Text Available Small Angle Neutron Scattering (SANS is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ∼ 1 nm up to ∼ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ∼ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area… through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer, form factor analysis (I(q→0, Guinier regime, intermediate regime, Porod regime, polydisperse system, structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates, and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast. It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of

  9. Small Mercury Relativity Orbiter

    Science.gov (United States)

    Bender, Peter L.; Vincent, Mark A.

    1989-01-01

    The accuracy of solar system tests of gravitational theory could be very much improved by range and Doppler measurements to a Small Mercury Relativity Orbiter. A nearly circular orbit at roughly 2400 km altitude is assumed in order to minimize problems with orbit determination and thermal radiation from the surface. The spacecraft is spin-stabilized and has a 30 cm diameter de-spun antenna. With K-band and X-band ranging systems using a 50 MHz offset sidetone at K-band, a range accuracy of 3 cm appears to be realistically achievable. The estimated spacecraft mass is 50 kg. A consider-covariance analysis was performed to determine how well the Earth-Mercury distance as a function of time could be determined with such a Relativity Orbiter. The minimum data set is assumed to be 40 independent 8-hour arcs of tracking data at selected times during a two year period. The gravity field of Mercury up through degree and order 10 is solved for, along with the initial conditions for each arc and the Earth-Mercury distance at the center of each arc. The considered parameters include the gravity field parameters of degree 11 and 12 plus the tracking station coordinates, the tropospheric delay, and two parameters in a crude radiation pressure model. The conclusion is that the Earth-Mercury distance can be determined to 6 cm accuracy or better. From a modified worst-case analysis, this would lead to roughly 2 orders of magnitude improvement in the knowledge of the precession of perihelion, the relativistic time delay, and the possible change in the gravitational constant with time.

  10. Small 'l' leadership.

    Science.gov (United States)

    Parsons, Jenni

    2009-05-01

    Recently I attended the RACGP Leadership Masterclass in Sydney. When I enrolled, I thought, 'Yes... sounds interesting...good speakers... I need to learn something about leadership...'As the time drew closer I started to get a bit anxious about the whole thing. I realised that the title, 'Masterclass', probably implied that the attendees were expected to already know something about leadership and its theories, if not have considerable expertise and experience in leadership. I also wondered how the workshop sessions were going to go and I started to feel a bit sorry for the facilitators. Imagine trying to facilitate a group of 10 aspiring leaders... a bit like trying to herd cats. A few days later I received a call from the organisers,saying they were a bit short of facilitators and could I help out if necessary. Great... better do a crash course in cat herding! Then there was the first 'predisposing activity'. Step 1: think of leaders you admire. Easy enough. Leaders of social justice and social change on a world stage, people who have shown great courage of their convictions and great orators popped into my head... Ghandi, Martin Luther King, Mandela, JFK. Step 2:describe the ways in which you are like these leaders. Whoa!Never going to measure up here. I wondered if there was going to be sessions on 'leadership for introverts', or 'leadership of small things', or 'leaders without grand vision or fabulous oratory skills', or perhaps 'leadership for people who are deeply suspicious of the corrupting influence of power'.

  11. Small diameter carbon nanopipettes

    Science.gov (United States)

    Singhal, Riju; Bhattacharyya, Sayan; Orynbayeva, Zulfiya; Vitol, Elina; Friedman, Gary; Gogotsi, Yury

    2010-01-01

    Nanoscale multifunctional carbon probes facilitate cellular studies due to their small size, which makes it possible to interrogate organelles within living cells in a minimally invasive fashion. However, connecting nanotubes to macroscopic devices and constructing an integrated system for the purpose of fluid and electrical signal transfer is challenging, as is often the case with nanoscale components. We describe a non-catalytic chemical vapor deposition based method for batch fabrication of integrated multifunctional carbon nanopipettes (CNPs) with tip diameters much smaller (10-30 nm) than previously reported (200 nm and above) and approaching those observed for multiwalled carbon nanotubes. This eliminates the need for complicated attachment/assembly of nanotubes into nanofluidic devices. Variable tip geometries and structures were obtained by controlled deposition of carbon inside and outside quartz pipettes. We have shown that the capillary length and gas flow rate have a marked effect on the carbon deposition. This gives us a flexible protocol, useful for growing carbon layers of different thicknesses at selective locations on a glass pipette to yield a large variety of cellular probes in bulk quantities. The CNPs possess an open channel for fluid transfer with the carbon deposited inside at 875 °C behaving like an amorphous semiconductor. Vacuum annealing of the CNP tips at temperatures up to 2000 °C yields graphitic carbon structures with an increase in conductivity of two orders of magnitude. Penetration of the integrated carbon nanoprobes into cells was shown to produce minimal Ca2+ signals, fast recovery of basal Ca2+ levels and no adverse activation of the cellular metabolism during interrogation times as long as 0.5-1 h.

  12. Regular Small-World Network

    Institute of Scientific and Technical Information of China (English)

    ZOU Zhi-Yun; MAO Bao-Hua; HAO Hai-Ming; GAO Jian-Zhi; YANG Jie-Jiao

    2009-01-01

    According to the deficiencies in Watts and Strogatz's small-world network model, we present a new regular model to establish the small-world network. Besides the property of the small-world, this model has other properties such as accuracy in controlling the average shortest path length L, and the average clustering coefficient C, also regular network topology as well as enhanced network robustness. This method improves the construction of the small-world network essentially, so that the regular small-world network closely resembles the actual network. We also present studies on the relationships among the quantities of a variety of edges, L and C in regular small-world network in detail. This research lays the foundation for the establishment of the regular small-world network and acts as a good guidance for further research of this model and its applications.

  13. 77 FR 30227 - Small Business Size Regulations, Small Business Innovation Research (SBIR) Program and Small...

    Science.gov (United States)

    2012-05-22

    ... (SBIR) Program and Small Business Technology Transfer (STTR) Program AGENCY: U.S. Small Business... (SBIR) and Small Business Technology Transfer (STTR) Programs. The proposed rule would implement... technological constraints, participation is limited to 125 registrants for the Webinar. If demand...

  14. Shock-induced poration, cholesterol flip-flop and small interfering RNA transfection in a phospholipid membrane: Multimillion atom, microsecond molecular dynamics simulations

    Science.gov (United States)

    Choubey, Amit

    performing a 15 mus all-atom MD simulation of a DPPC-CHOL bilayer. We find that the CHOL flip-flop rates are on the sub microsecond timescale. These results are verified by performing various independent parallel replica (PR) simulations. Our PR simulations provide significant boost in sampling of the flip-flop events. We observe that the CHOL flip-flop can induce membrane order, regulate membrane-bending energy, and facilitate membrane relaxation. The rapid flip-flop rates reported here have important implications for the role of CHOL in mechanical properties of cell membranes, formation of domains, and maintaining CHOL concentration asymmetry in plasma membrane. Our PR approach can reach submillisecond time scales and bridge the gap between MD simulations and Nuclear Magnetic Resonance (NMR) experiments on CHOL flip-flop dynamics in membranes. The last project deals with transfection barriers encountered by a bare small interfering RNA (siRNA) in a phospholipid bilayer. SiRNA molecules play a pivotal role in therapeutic applications. A key limitation to the widespread implementation of siRNA-based therapeutics is the difficulty of delivering siRNA-based drugs to cells. We have examined structural and mechanical barriers to siRNA passage across a phospholipid bilayer using all-atom MD simulations. We find that the electrostatic interaction between the anionic siRNA and head groups of phospholipid molecules induces a phase transformation from the liquid crystalline to ripple phase. Steered MD simulations reveal that the siRNA transfection through the ripple phase requires a force of ˜ 1.5 nN.

  15. Small Bowel Hamartoma: A Huge Diverticulum of Small Bowel

    Directory of Open Access Journals (Sweden)

    Hamdi Ebdewi

    2013-01-01

    Full Text Available A-20-year old male, with no significant medical history, presented with clinical features mimicking a perforated acute appendicitis. Because of features of peritonitis, a laparotomy was performed which showed a segment of small bowel with multiple large diverticula and mesenteric cysts. A segmental small bowel resection was performed. The patient made an uneventful recovery from surgery. Histology revealed features of a small bowel hamartoma.

  16. Jupiter small satellite montage

    Science.gov (United States)

    2000-01-01

    A montage of images of the small inner moons of Jupiter from the camera onboard NASA's Galileo spacecraft shows the best views obtained of these moons during Galileo's 11th orbit around the giant planet in November 1997. At that point, Galileo was completing its first two years in Jupiter orbit--known as the Galileo 'prime mission'--and was about to embark on a successful two-year extension, called the Galileo Europa Mission. The top two images show the moon Thebe. Thebe rotates by approximately 50 degrees between the time these two images were taken, so that the same prominent impact crater is seen in both views; this crater, which has been given the provisional name Zethus, is near the point on Thebe that faces permanently away from Jupiter. The next two images show the moon Amalthea; they were taken with the Sun directly behind the observer, an alignment that emphasizes patterns of intrinsically bright or dark surface material. The third image from the top is a view of Amalthea's leading side, the side of the moon that 'leads' as Amalthea moves in its orbit around Jupiter. This image looks 'noisy' because it was obtained serendipitously during an observation of the Jovian satellite Io (Amalthea and Io shared the same camera frame but the image was exposed for bright Io rather than for the much darker Amalthea). The fourth image from the top emphasizes prominent 'spots' of relatively bright material that are located near the point on Amalthea that faces permanently away from Jupiter. The bottom image is a view of the tiny moon Metis. In all the images, north is approximately up, and the moons are shown in their correct relative sizes. The images are, from top to bottom: Thebe taken on November 7, 1997 at a range of 504,000 kilometers (about 313,000 miles); Thebe on November 7, 1997 at a range of 548,000 kilometers (about 340,000 miles); Amalthea on November 6, 1997 at a range of about 650,000 kilometers (about 404,000 miles); Amalthea on November 7, 1997 at a

  17. Small Business Innovation Research and Small Business Technology Transfer Programs

    Science.gov (United States)

    Garrison, Lynn; Jasper, Gwen

    2015-01-01

    The Small Business Innovation Research (SBIR)/Small Business Technology Transfer (STTR) programs fund the research, development, and demonstration of innovative technologies that fulfill NASA's needs as described in the annual Solicitations and have significant potential for successful commercialization. The only eligible participants are small business concern (SBC) with 500 or fewer employees or a nonprofit research institute such as a university or a research laboratory with ties to an SBC. These programs are potential sources of seed funding for the development of small business innovations.

  18. Small Wind Site Assessment Guidelines

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, Tim [Advanced Energy Systems LLC, Eugene, OR (United States); Preus, Robert [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-09-01

    Site assessment for small wind energy systems is one of the key factors in the successful installation, operation, and performance of a small wind turbine. A proper site assessment is a difficult process that includes wind resource assessment and the evaluation of site characteristics. These guidelines address many of the relevant parts of a site assessment with an emphasis on wind resource assessment, using methods other than on-site data collection and creating a small wind site assessment report.

  19. Investigation on a Small Oscillogram

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A small oscillogram, one end of which was substituted by a bright point caused by the redox of an appropriate depolarizer and the other end of which was the redox of Hg or the redox of supporting electrolyte cation, was investigated in this paper. Experimental results of application of the small oscillogram to oscillographic determination of cefoperazone showed that the small oscillogram was more stable, sensitive, and less interference than classical oscillogram.

  20. Financial management for small companies

    Science.gov (United States)

    Bruce Hansen; Jeff Palmer; Jeff Palmer

    2000-01-01

    The wood-products industry is characterized by many small manufacturers that lack the staff to compile and analyze information on their operations and investments. Two computer programs, FRAN and JEFFI, have been developed by the USDA Forest Service at Princeton, West Virginia,to help small companies better analyze and monitor current performance, and better evaluate...

  1. Introduction: innovation and small business

    NARCIS (Netherlands)

    A.R. Thurik (Roy)

    1996-01-01

    textabstractThis paper introduces the special issue of Small Business Economics on Innovation. What binds the papers together is either their focus on the effect of firm size on the causes and consequences of innovation or their focus on the role small firms play in reshaping the industrial landscap

  2. INNOVATION IN BRAZILIAN SMALL COMPANIES

    National Research Council Canada - National Science Library

    Rodrigues, Tonny Kerley de Alencar; Lira, Átila De Melo; Naas, Irenilza De Alencar

    2015-01-01

    .... And the data confirms that small Brazilian companies generally have difficulties to sell their innovations. Keywords: innovation, small enterprises, patents. 1. INTRODUCTION Companies worldwide are looking to technological innovation as feasible for your market expansion (BURNS; STALKER, 1961; NELSON, 1993) alternative. In Brazil, the change an...

  3. Small Molecular as SIRT Modulators.

    Science.gov (United States)

    Yao, Lei; Xu, Xiangming; Chen, Kai

    2016-06-19

    Sirtuins are class III histone deacetylases, they involve in many important biological functions. Small molecules that can modulate sirtuin activity have been shown to have potential for treating many human diseases. In the article, recent development of small molecular as SIRT modulators has been reviewed.

  4. Standard Deviation for Small Samples

    Science.gov (United States)

    Joarder, Anwar H.; Latif, Raja M.

    2006-01-01

    Neater representations for variance are given for small sample sizes, especially for 3 and 4. With these representations, variance can be calculated without a calculator if sample sizes are small and observations are integers, and an upper bound for the standard deviation is immediate. Accessible proofs of lower and upper bounds are presented for…

  5. Small Bowel Review - Part I

    OpenAIRE

    ABR Thomson; Wild, G.

    1997-01-01

    Significant advances have been made in the study of the small bowel. Part I of this two-part review of the small bowel examines carbohydrates, including brush border membrane hydrolysis and sugar transport; amino acids, dipeptides, proteins and food allergy, with a focus on glutamine, peptides and macromolecules, and nucleoside...

  6. Introduction: innovation and small business

    NARCIS (Netherlands)

    A.R. Thurik (Roy)

    1996-01-01

    textabstractThis paper introduces the special issue of Small Business Economics on Innovation. What binds the papers together is either their focus on the effect of firm size on the causes and consequences of innovation or their focus on the role small firms play in reshaping the industrial

  7. APPROACH TO SMALL FAMILY NORM

    Directory of Open Access Journals (Sweden)

    Nonibala

    2014-09-01

    Full Text Available The Idea of approach to maintain small family norm in the family and so to the society is the hope for almost all of the couples as the saying -"Small family is a happy family". And every couple always thinks and plan for a safer and better future.

  8. APPROACH TO SMALL FAMILY NORM

    OpenAIRE

    Nonibala

    2014-01-01

    The Idea of approach to maintain small family norm in the family and so to the society is the hope for almost all of the couples as the saying -"Small family is a happy family". And every couple always thinks and plan for a safer and better future.

  9. How Small Is a Billionth?

    Science.gov (United States)

    Gough, John

    2007-01-01

    Children's natural curiosity about numbers, big and small can lead to exploring place-value ideas. But how can these abstract concepts be experienced more concretely? This article presents some practical approaches for conceptualising very small numbers using linear models, area models, volume models, and diagrams.

  10. Resourcing Change in Small Schools

    Science.gov (United States)

    Anderson, Michelle; White, Simone

    2011-01-01

    The theme of this article is the challenge that school leaders face in creating the conditions for learning in small schools. We draw on the concepts of "social capital" and "social entrepreneurship" to identify tensions and possibilities for school leaders in a case study of a small rural school as they seek to find resources…

  11. Small bowel obstruction- a surprise.

    Science.gov (United States)

    Mathew, Jeffrey Daniel; Cp, Ganesh Babu; M, Balachandar; M, Ramanathan

    2015-01-01

    Trans - omental hernia is very rare, accounting to 1-4% of all internal hernias which is an unusual cause of small bowel obstruction. Here we present a case report of a small bowel obstruction in a female due to trans - omental hernia presenting with central abdominal pain, distension and bilious vomiting. She had no previous history of trauma, surgery. Plain X-ray abdomen erect showed multiple air fluid levels with dilated small bowel loops. Emergency laparotomy revealed a segment of congested small bowel loop (ileum) through a defect in greater omentum. On table the herniated bowel loop was reduced and the defect in greater omentum was closed primarily. There was no necessity for bowel resection as it regained normal colour after reduction. Postoperative period was uneventful with complete resolution of symptoms. This case is presented for its rarity and its importance in clinical differential diagnosis of acute abdomen due to small bowel obstruction.

  12. Understanding the small object argument

    CERN Document Server

    Garner, Richard

    2007-01-01

    The small object argument is a transfinite construction which, starting from a set of maps in a category, generates a weak factorisation system on that category. As useful as it is, the small object argument has some problematic aspects: it possesses no universal property; it does not converge; and it does not seem to be related to other transfinite constructions occurring in categorical algebra. In this paper, we give an ``algebraic'' refinement of the small object argument, cast in terms of Grandis and Tholen's natural weak factorisation systems, which rectifies each of these three deficiencies.

  13. Cosmic Strings with Small Tension

    CERN Document Server

    Halyo, Edi

    2009-01-01

    We describe cosmic F--term strings with exponentially small tension which are D3 branes wrapped on deformed $A_3$ singularities. We show that brane instanton effects which can be calculated after a geometric transition give rise to an exponentially small volume for the node on which the D3 branes wrap leading to a string with small tension. We generalize our description to the case of non--Abelian cosmic strings and argue that these strings are stable against monopole--anti monopole pair creation.

  14. Stages of Small Intestine Cancer

    Science.gov (United States)

    ... intestine . The digestive system removes and processes nutrients ( vitamins , minerals , carbohydrates , fats, proteins , and water) from foods ... a microscope to see whether they contain cancer. Bypass : Surgery to allow food in the small intestine ...

  15. Severe small bowel radiation enteritis

    Energy Technology Data Exchange (ETDEWEB)

    Jaen, J.; Santos, J.A.; Carrion, J.R.; Garcia, P. (Hospital General Gregorio Maranon, Madrid (Spain))

    1989-01-01

    We have during recent years observed 8 patients with serious radiation injury to the small intestine. As the cases are quite illustrative, their symptomatology is briefly reported and the treatment and possible predisposing factors are analysed. (orig./MG).

  16. Small Airframe Manufacturer's Icing Perspective

    Science.gov (United States)

    Hoppins, Jim

    2009-01-01

    This viewgraph presentation describes the icing effects, risk mitigation practices, and icing certifications for various Cessna small aircraft models. NASA's role in the development of simulation tools for icing certifications is also discussed.

  17. Small Probe Reentry System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Aerospace Corporation (GAC), and its research partner, Cal Poly San Luis Obispo (CPSLO), will develop an integrated Small Probe Reentry System (SPRS) for low...

  18. Convenient measurement of small impulses

    Science.gov (United States)

    Brost, G.; Deaton, T.; Duvall, B.; Boyle, W.; Tinsley, J.; Bohn, C.; Stephen, M.; Souders, J.

    1986-01-01

    This paper describes a convenient method which has been used for the measurement of small impulses (1-20 dyn s). An inductive displacement gauge was used to monitor displacement of a ballistic pendulum.

  19. Small- x resummation from HELL

    Science.gov (United States)

    Bonvini, Marco; Marzani, Simone; Peraro, Tiziano

    2016-11-01

    Small- x logarithmic enhancements arising from high-energy gluon emissions affect both the evolution of collinearly-factorized parton densities and partonic coefficient functions. With the higher collider energy reached by the LHC, the prospect of a future high-energy collider, and the recent deep-inelastic scattering (DIS) results at small- x from HERA, providing phenomenological tools for performing small- x resummation has become of great relevance. In this paper we discuss a framework to perform small- x resummation for both parton evolution and partonic coefficient functions and we describe its implementation in a computer code named High-Energy Large Logarithms ( HELL). We present resummed and matched results for the DGLAP splitting functions and, as a proof of principle, for the massless structure functions in DIS. Furthermore, we discuss the uncertainty from subleading terms on our results.

  20. Small satellites and their regulation

    CERN Document Server

    Jakhu, Ram S

    2014-01-01

    Since the launch of UoSat-1 of the University of Surrey (United Kingdom) in 1981, small satellites proved regularly to be useful, beneficial, and cost-effective tools. Typical tasks cover education and workforce development, technology demonstration, verification and validation, scientific and engineering research as well as commercial applications. Today the launch masses range over almost three orders of magnitude starting at less than a kilogram up to a few hundred kilograms, with budgets of less than US$ 100.00 and up to millions within very short timeframes of sometimes less than two years. Therefore each category of small satellites provides specific challenges in design, development and operations. Small satellites offer great potentials to gain responsive, low-cost access to space within a short timeframe for institutions, companies, regions and countries beyond the traditional big players in the space arena. For these reasons (particularly the low cost of construction, launch and operation), small (m...

  1. Cryoablation for Small Renal Masses

    Directory of Open Access Journals (Sweden)

    J. L. Dominguez-Escrig

    2008-01-01

    Full Text Available Advances in imaging techniques (CT and MRI and widespread use of imaging especially ultrasound scanning have resulted in a dramatic increase in the detection of small renal masses. While open partial nephrectomy is still the reference standard for the management of these small renal masses, its associated morbidity has encouraged clinicians to exploit the advancements in minimally invasive ablative techniques. The last decade has seen the rapid development of laparoscopic partial nephrectomy and novel ablative techniques such as, radiofrequency ablation (RFA, high-intensity focused ultrasound (HIFU, and cryoablation (CA. In particular, CA for small renal masses has gained popularity as it combines nephron-sparing surgery with a minimally invasive approach. Studies with up to 5-year followup have shown an overall and cancer-specific 5-year survival of 82% and 100%, respectively. This manuscript will focus on the principles and clinical applications of cryoablation of small renal masses, with detailed review of relevant literature.

  2. Small Sat Analysis Laboratory Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Low-Cost Small Spacecraft Program is focused on the technologies, subsystems, methodologies, and mission concepts for space missions which lower the...

  3. JPL Small Body Database Browser

    Data.gov (United States)

    National Aeronautics and Space Administration — The JPL Small-Body Database Browser provides data for all known asteroids and many comets. Newly discovered objects and their orbits are added on a daily basis....

  4. Development project of small accelerator

    CERN Document Server

    Yamada, S

    2002-01-01

    The object of this project is demonstration of a small proton and heavy ion synchrotron and a small hard X-ray photon radiation source by using new technology and application of them to therapy, diagnosis, material science and life science. In this paper, a part of small proton and heavy ion synchrotron is discussed. Nine organizations joined in this project. There are four development themes such as optimization of laser-ion 100 TW class source target, beam storage and cooling device, small synchrotron ring and FFAG accelerator. Outline and contents of development of them are explained. This project is planning to generate a few MeV/u carbon ions in fully ionized states by impact of laser with about 100 TW output. 3 T maximum bending magnetic field using normal conduction AC magnet will be actualized for synchrotron with 200 MeV proton beam. (S.Y.)

  5. Quantum Small-world Networks

    CERN Document Server

    Wei, Zong-Wen; Han, Xiao-Pu

    2011-01-01

    Quantum networks are critical to quantum communication and distributed quantum computing. Here we propose a small-world model of large-scale quantum repeater networks, where "small-world" is a fundamental concept rooted in complex networks, which describe a broad range of real systems. The core of the model is to relate the hierarchical fashion of measurements to coarse-graining process, when quantum repeater protocols are implemented. We demonstrate that quantum repeater networks with fractal structure can be enlarged with certain length scale in geographic space, while preserving topology by performing renormalization. Actually, renormalization here serves as an organizing principle determining the distribution of long-range entangled links over quantum networks, which gives rise to fractal to small-world transition. Furthermore, by iterative implementation of renormalization on the former coarse-grained network, we eventually obtain an onion-like, hierarchical quantum small-world network, where the distanc...

  6. Matrix Theory of Small Oscillations

    Science.gov (United States)

    Chavda, L. K.

    1978-01-01

    A complete matrix formulation of the theory of small oscillations is presented. Simple analytic solutions involving matrix functions are found which clearly exhibit the transients, the damping factors, the Breit-Wigner form for resonances, etc. (BB)

  7. Small and Scenic Fenghuang City

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    FENGHUANG(Chinese for phoenix), a small city under the jurisdiction of the Tujia Autonomous Prefecture of Hunan Province, borders northern Guizhou Province and eastern Chongqing Municipality. Surrounded by mountains and girdled by the Tuojiang River, this small, quiet city is famous for its beautiful landscape, and as birthplace of several celebrated Chinese personages.Fenghuang’s history dates back 1,316 years. It was originally named Weiyang, and its location was in today’s Huangsiqiao

  8. Small Bowel Review - Part I

    OpenAIRE

    Thomson, ABR; Wild, G.

    1997-01-01

    Significant advances have been made in the study of the small bowel. Part I of this two-part review of the small bowel examines carbohydrates, including brush border membrane hydrolysis and sugar transport; amino acids, dipeptides, proteins and food allergy, with a focus on glutamine, peptides and macromolecules, and nucleosides, nucleotides and polyamines; salt and water absorption, and diarrhea, including antidiarrheal therapy and oral rehydration treatment; lipids (digestion and absorption...

  9. Small Satellite Reaction Wheel Optimization

    OpenAIRE

    Michaelis, Ted

    1990-01-01

    The very "smallness" of small satellites mandates mass minimization. This paper addresses minimization of overall reaction wheel mass, including the incremental mass of the power subsystem needed to support the reaction wheel. The results are applicable to a wide range of wheel sizes and are suitable for optimization at the configuration level. For an average momentum and torque operating point, the minimization process yields wheel radius and angular velocity, as well as, the masses associat...

  10. World Small Hydropower Development Report

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Heng; Esser, Lara (ICSGP (China)); Masera, Diego (UNIDO, Vienna (Austria))

    2013-07-01

    Currently, small hydropower plants with a capacity of 10 MW, exist in 148 countries or territories worldwide. Four other countries have been identified with resource potential. This report aims to identify the development status and resource potential of small hydro in various countries, territories and regions throughout the world. Working with experts at the ground level to compile and share existing information, experiences and challenges, one comprehensive report was created. Decision-makers, stakeholders and potential investors clearly need this comprehensive information to more effectively promote small hydropower as a renewable and rural energy source for sustainable development and to overcome the existing development barriers. The findings of this report show that small hydropower potential globally is approximated at almost 173 GW. The figure is arrived by totaling data from a wide range of sources with potential compromise of data integrity to varying degrees. For example, research data on economically feasible potential were more readily available in developed countries than those in the least developed or developing countries. More than half of the world's known hydropower potential is located in Asia, around one third can be found in Europe and the Americas. It is possible in the future that more small hydropower potential might be identified both on the African and American continents. The installed small hydropower capacity (up to 10 MW) is estimated to be 75 GW in 2011/2012. The report provides detailed data for each country/region, including recommendations on the national, regional and international level.

  11. Chartering Launchers for Small Satellites

    Science.gov (United States)

    Hernandez, Daniel

    The question of how to launch small satellites has been solved over the years by the larger launchers offering small satellites the possibility of piggy-backing. Specific fixtures have been developed and commercialized: Arianespace developed the ASAP interface, the USAF studied ESPA, NASA has promoted Shuttle launch possibilities, Russian authorities and companies have been able to find solutions with many different launchers... It is fair to say that most launcher suppliers have worked hard and finally often been able to find solutions to launch most small satellites into orbit. It is also true, however, that most of these small satellites were technology demonstration missions capable of accepting a wide range of orbit and launch characteristics: orbit altitude and inclination, launch date, etc. In some cases the small satellite missions required a well-defined type of orbit and have therefore been obliged to hire a small launcher on which they were the prime passenger. In our paper we would like to propose an additional solution to all these possibilities: launchers could plan well in advance (for example about 3 years), trips to precisely defined orbits to allow potential passengers to organize themselves and be ready on the D-Day. On the scheduled date the chartered launcher goes to the stated orbit while on another date, another chartered launcher goes to another orbit. The idea is to organize departures for space like trains or airplanes leaving on known schedules for known destinations.

  12. Small group discussion: Students perspectives.

    Science.gov (United States)

    Annamalai, Nachal; Manivel, Rajajeyakumar; Palanisamy, Rajendran

    2015-08-01

    Various alternative methods are being used in many medical colleges to reinforce didactic lectures in physiology. Small group teaching can take on a variety of different tasks such as problem-solving, role play, discussions, brainstorming, and debate. Research has demonstrated that group discussion promotes greater synthesis and retention of materials. The aims of this study were to adopt a problem-solving approach by relating basic sciences with the clinical scenario through self-learning. To develop soft skills, to understand principles of group dynamics, and adopt a new teaching learning methodology. Experimental study design was conducted in Phase I 1(st) year medical students of 2014-2015 batch (n = 120). On the day of the session, the students were grouped into small groups (15 each). The session started with the facilitator starting off the discussion. Feedback forms from five students in each group was taken (n = 40). A five point Likert scale was used ranging from strongly agree to strongly disagree. Data were analyzed using IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp. Our results show that 70% of the students opined that small group discussion were interactive, friendly, innovative, built interaction between teacher and student. Small group discussion increased their thought process and helped them in better communication. The small group discussion was interactive, friendly, and bridged the gap between the teacher and student. The student's communication skills are also improved. In conclusion, small group discussion is more effective than the traditional teaching methods.

  13. Small Bowel and Liver/Small Bowel Transplantation in Children

    Science.gov (United States)

    Reyes, Jorge; Tzakis, Andreas G.; Todo, Satoru; Nour, Bakr; Starzl, Thomas E.

    2010-01-01

    A clinical trial of intestinal transplantation was initiated at the University of Pittsburgh in May 1990. Eleven children received either a combined liver/small bowel graft (n = 8) or an isolated small bowel graft (n = 3). Induction as well as maintenance immunosuppression was with FK-506 and steroids. Four patients were male, and seven were female; the age range was 6 months to 10.2 years. There were 3 deaths (all in recipients of the combined liver/small bowel graft), which were attributed to graft-versus-host disease (n = 1), posttransplant lymphoproliferative disease (n = 1), and biliary leak (n = 1). Transplantation of the intestine has evolved into a feasible operation, with an overall patient and graft survival rate of 73%. These survivors are free of total parenteral nutrition, and the majority are home. These encouraging results justify further clinical trials. PMID:8062049

  14. DEVELOPMENT OF SMALL INJECTION MOULDING MACHINE FOR FORMING SMALL PLASTIC ARTICLES FOR SMALL-SCALE INDUSTRIES

    Directory of Open Access Journals (Sweden)

    OYETUNJI, A.

    2010-03-01

    Full Text Available Development of small injection moulding machine for forming small plastic articles in small-scale industries was studied. This work which entailed design, construction and test small injection moulding machine that was capable of forming small plastic articles by injecting molten resins into a closed, cooled mould, where it solidifies to give the desired products was developed. The machine was designed and constructed to work as a prototype for producing very small plastic components. Design concept, operation, and assembly of components parts were made. Also, working drawings and materials selection were made based on calculations of the diameter of injection plunger, number of teeth required for the plunger rack and spur gear, the angular velocity, number of revolution, torque and power obtained from the electric motor selected and the leverage on the handle of the machine. The machine parts/components were then assembled in line with the designed made, thereafter the constructed machine was tested using high density polyethylene and master batch. The results obtained from the test were satisfactory.

  15. Small bowel faeces sign in patients without small bowel obstruction

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, S.L. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States)]. E-mail: stacylynnjacobs@yahoo.com; Rozenblit, A. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States); Ricci, Z. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States); Roberts, J. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States); Milikow, D. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States); Chernyak, V. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States); Wolf, E. [Department of Radiology, Montefiore Medical Center, Bronx, NY (United States)

    2007-04-15

    Aim: To evaluate frequency and clinical relevance of the 'small bowel faeces' sign (SBFS) on computed tomography (CT) in patients with and without small bowel obstruction (SBO) presenting with acute abdominal or acute abdominal and flank pain. Methods: Abdominal CTs of consecutive patients presenting to the emergency department with abdominal or flank pain over a 6 month period were retrospectively reviewed by six radiologists, independently, for the presence of the SBFS. Examinations with positive SBFS were further evaluated in consensus by three radiologists, blinded to the final diagnosis. The small bowel was graded as non-dilated (<2.5 cm) and mildly (2.5-2.9 cm), moderately (3-4 cm) or severely (>4 cm) dilated. The location of SBFS and presence of distal small bowel collapse indicative of SBO was recorded. Imaging findings were subsequently correlated with the final diagnosis via chart review and compared between patients with and without SBO. Results: Of 1642 CT examinations, a positive SBFS was found in 100 (6%) studies. Of 100 patients with a positive SBFS, 32 (32%) had documented SBO. The remaining 68 patients had other non-obstructive diagnoses. SBFS was located in proximal, central, distal and multisegmental bowel loops in one (3.1%), eight (25.0%), 21 (65.6%) and two (6.3%) patients with SBO, and in zero (0%), 10 (14.7%), 53 (77.9%) and five (7.4%) of patients without SBO (p < 0.273). The small bowel was non-dilated and mildly, moderately or severely dilated in one (3%), five (16%), 20 (62%) and six (19%) patients with SBO, and in 61(90%), seven (10%), zero (0%) and zero (0%) patients without SBO. Normal or mildly dilated small bowel was seen in all (100%) patients without SBO, but only in six (19%) of 32 patients with SBO (p < 0.0001). Moderate or severe small bowel dilatation was seen in 26 (81%) patients with SBO (p < 0.0001), but it was absent in patients without SBO. Distal small bowel collapse was found in 27 (84.4%) of 32 patients with

  16. Tumours in the Small Bowel

    Directory of Open Access Journals (Sweden)

    N. Kurniawan

    2014-01-01

    Full Text Available Small bowel tumours are rare and originate from a wide variety of benign and malignant entities. Adenocarcinomas are the most frequent primary malignant small bowel tumours. Submucosal tumours like gastrointestinal stromal tumours (GIST or neuroendocrine tumours (NET may show a central umbilication, pathologic vessels, bridging folds or an ulceration of the overlying mucosa. These signs help to differentiate them from harmless bulges caused by impression from outside, e.g. from other intestinal loops. Sarcomas of the small bowel are rare neoplasias with mesenchymal origin, sometimes presenting as protruding masses. Benign tumours like lipoma, fibrolipoma, fibroma, myoma, and heterotopias typically present as submucosal masses. They cannot be differentiated endoscopically from those with malignant potential as GIST or NET. Neuroendocrine carcinomas may present with diffuse infiltration, which may resemble other malignant tumours. The endoscopic appearance of small bowel lymphomas has a great variation from mass lesions to diffuse infiltrative changes. Melanoma metastases are the most frequent metastases to the small bowel. They may be hard to distinguish from other tumours when originating from an amelanotic melanoma.

  17. Small-ductprimarysclerosingcholangitis withhepatocellularcarcinomarequiringliver transplantation

    Institute of Scientific and Technical Information of China (English)

    Sharif Ali; Veena Shah

    2010-01-01

    BACKGROUND: Primary sclerosing cholangitis (PSC) is a chronic progressive cholestatic liver disease, which usually affects young adults and is diagnosed by cholangiography. On a few occasions, the disease either starts in or exclusively involves the small intrahepatic bile ducts, referred to as small-duct PSC. METHODS: A 31-year-old man presented with severe hematemesis secondary to liver cirrhosis. Over a course of 8 years, his liver decompensated and required an orthotopic liver transplantation. In this report we discuss his disease presentation, course of management, and the post-transplantation course of manage-ment, and review the morphologic diagnosis, and differential diagnosis of the disease with large-duct type and other diseases that involve small intrahepatic bile ducts. RESULTS:The patient's explanted liver showed changes of PSC affecting only the small- and medium-sized bile ducts in addition to three incidental nodules of hepatocellular carcinoma. CONCLUSIONS: Small-duct PSC has a substantially better prognosis than the large-duct type, with less chance of developing cirrhosis and an equal risk for developing hepato-cellular carcinoma, but no increased risk for developing cholangiocarcinoma. Treatment seems to help relieve the symptoms but not necessarily improve survival. Liver transplantation remains the ultimate cure.

  18. Industry Research and Recommendations for Small Buildings and Small Portfolios

    Energy Technology Data Exchange (ETDEWEB)

    Langner, Rois [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hendron, Bob [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pless, Shanti [National Renewable Energy Lab. (NREL), Golden, CO (United States); Huppert, Mark [National Trust for Historic Preservation, Washington, DC (United States); Cochrane, Ric [National Trust for Historic Preservation, Washington, DC (United States)

    2013-12-01

    Small buildings have been left behind in the energy efficiency marketplace because financial and technical resources have flowed to larger commercial buildings. DOE's Building Technologies Office works with the commercial building industry to accelerate the uptake of energy efficiency technologies and techniques in existing and new commercial buildings (DOE 2013). BTO recognizes the SBSP sector'spotential for significant energy savings and the need for investments in resources that are tailored to this sector's unique needs. The industry research and recommendations described in this report identify potential approaches and strategic priorities that BTO could explore over the next 3-5 years that will support the implementation of high-potential energy efficiency opportunities for thisimportant sector. DOE is uniquely positioned to provide national leadership, objective information, and innovative tools, technologies, and services to support cost-effective energy savings in the fragmented and complex SBSP sector. Properly deployed, the DOE effort could enhance and complement current energy efficiency approaches. Small portfolios are loosely and qualitatively defined asportfolios of buildings that include only a small number of small buildings. This distinction is important because the report targets portfolio owners and managers who generally do not have staff and other resources to track energy use and pursue energy efficiency solutions.

  19. Marketing the Uniqueness of Small Towns. Small Town Strategy.

    Science.gov (United States)

    Hogg, David H.; Dunn, Douglas

    A small town can strengthen its local economy as a result of business people and concerned citizens collectively identifying that community's uniqueness and then capitalizing on it via advertising, personal selling, sales promotion, or publicity. This publication relates the science of marketing to communities. Seven simple techniques are provided…

  20. Purchasing cooperatives for small employers.

    Science.gov (United States)

    Mallozzi, J

    1997-12-01

    Despite a booming economy, the number of uninsured Americans is rising. It hit nearly 42 million in 1996. Many of the uninsured work at businesses with fewer than 50 employees. Because small firms have traditionally found it difficult to provide health benefits, purchasing cooperatives have grown in scope and size across the country in recent years. By bringing small businesses together to buy insurance as a group, these organizations can help employers provide greater choice to their workers at a lower cost. However, to operate well in the insurance market, purchasing cooperatives must be well-designed and provided with adequate legal protections.

  1. Small Bowel Review - Part I

    Directory of Open Access Journals (Sweden)

    ABR Thomson

    1997-01-01

    Full Text Available Significant advances have been made in the study of the small bowel. Part I of this two-part review of the small bowel examines carbohydrates, including brush border membrane hydrolysis and sugar transport; amino acids, dipeptides, proteins and food allergy, with a focus on glutamine, peptides and macromolecules, and nucleosides, nucleotides and polyamines; salt and water absorption, and diarrhea, including antidiarrheal therapy and oral rehydration treatment; lipids (digestion and absorption, fatty acid binding proteins, intracellular metabolism, lipoproteins and bile acids; and metals (eg, iron and vitamins.

  2. Appropriate technology for small turbines

    Energy Technology Data Exchange (ETDEWEB)

    Strohmer, F.; Walch, E.

    1981-11-01

    The investment costs of small-scale hydro plants are relatively high; of these the electro-mechanical equipment is generally a high proportion. One way of reducing these costs is to use information and experience gained in the manufacture of equipment for large plants, avoiding expensive testing and assessment. To exploit this experience, a standard program has been developed which can be applied quickly and easily for the design of small turbines. In this way the best choice of turbines and configurations can be determined rapidly for any site.

  3. Department of the Navy Small Business Programs

    Science.gov (United States)

    2014-08-13

    small business concerns and to women -owned small business concerns eligible under the Women -Owned Small Business Program. The dollar...2014 For All US-Based Women Owned Small Business Awards Over $ 200M Over $ 100M Over...Department of the Navy Small Business Programs Gold Coast August 13, 2014 Report Documentation Page Form ApprovedOMB No. 0704-0188

  4. Hispanic Women Small Business Owners.

    Science.gov (United States)

    Sarason, Yolanda; Koberg, Christine

    1994-01-01

    A survey of 22 Hispanic women who owned small businesses in a western state found that most were located in metropolitan areas, were new to business ownership, had started the business themselves, engaged in "miscellaneous services," and generated lower than average revenues. Respondents were similar to nonminority owners in educational…

  5. Small store presence in Japan

    NARCIS (Netherlands)

    M.A. Carree (Martin); J.C.A. Potjes; A.R. Thurik (Roy)

    1993-01-01

    textabstractThe determinants of the development of small store presence in Japan are investigated using a fixed effects multinomial logit market share model. Large stores tend to have higher market shares in shop-types with increasing shares in consumer expenditures, increasing inventory turnover,

  6. Economics: An Emerging Small World?

    NARCIS (Netherlands)

    S. Goyal (Sanjeev); M.J. van der Leij (Marco); J.L. Moraga-Gonzalez (José Luis)

    2004-01-01

    textabstractThis paper examines the small world hypothesis. The first part of the paper presents empirical evidence on the evolution of a particular world: the world of journal publishing economists during the period 1970-2000. We find that in the 1970's the world of economics was a collection of is

  7. Sonography of the small intestine

    Institute of Scientific and Technical Information of China (English)

    Kim Nylund; Svein (φ)degaard; Trygve Hausken; Geir Folvik; Gülen Arslan Lied; Ivan Viola; Helwig Hauser; Odd-Helge Gilja

    2009-01-01

    In the last two decades, there has been substantial development in the diagnostic possibilities for examining the small intestine. Compared with computerized tomography, magnetic resonance imaging, capsule endoscopy and double-balloon endoscopy, ultrasonography has the advantage of being cheap, portable, flexible and user- and patient-friendly, while at the same time providing the clinician with image data of high temporal and spatial resolution. The method has limitations with penetration in obesity and with intestinal air impairing image quality. The flexibility ultrasonography offers the examiner also implies that a systematic approach during scanning is needed. This paper reviews the basic scanning techniques and new modalities such as contrast-enhanced ultrasound, elastography, strain rate imaging, hydrosonography, allergosonography, endoscopic sonography and nutritional imaging, and the literature on disease-specific findings in the small intestine. Some of these methods have shown clinical benefit, while others are under research and development to establish their role in the diagnostic repertoire. However, along with improved overall image quality of new ultrasound scanners, these methods have enabled more anatomical and physiological changes in the small intestine to be observed. Accordingly, ultrasound of the small intestine is an attractive clinical tool to study patients with a range of diseases.

  8. Disorders of the Small Intestine

    Science.gov (United States)

    ... peristaltic). They occur mostly in the upper small intestine and fade out before moving too far down-stream. They occur in most people at infrequent intervals, but in patients with irritable bowel syndrome (IBS) they may be associated with abdominal pain. ...

  9. Calculator. Owning a Small Business.

    Science.gov (United States)

    Parma City School District, OH.

    Seven activities are presented in this student workbook designed for an exploration of small business ownership and the use of the calculator in this career. Included are simulated situations in which students must use a calculator to compute property taxes; estimate payroll taxes and franchise taxes; compute pricing, approximate salaries,…

  10. Small Secondary Schools Administrative Manual.

    Science.gov (United States)

    Alaska State Dept. of Education, Juneau. Office of Public Information and Publications.

    A guideline for providing quality secondary education in situations where only a relatively small number of students are involved, this manual describes the organizational options for high school programs. The options discussed are regional high schools, area secondary schools, and local high schools. Local high schools can be further classified…

  11. Small Molecule PET-Radiopharmaceuticals

    NARCIS (Netherlands)

    Elsinga, Philip H.; Dierckx, Rudi A. J. O.

    2014-01-01

    This review describes several aspects required for the development of small molecule PET-tracers. Design and selection criteria are important to consider before starting to develop novel PET-tracers. Principles and latest trends in C-11 and F-18-radiochemistry are summarized. In addition an update o

  12. New Russian Combat Small Boats

    Directory of Open Access Journals (Sweden)

    Aleksandr F. Mitrofanov

    2016-12-01

    Full Text Available The article presents an overview of small combat boats. The author provides a description and gives an analysis of the characteristics of the boat "Raptor", boat "BK-16", boat "Strizh-4-1 DSh", and assault boat "BK-10".

  13. Small Mammals, Reptiles, and Amphibians

    Science.gov (United States)

    Bryce Rickel

    2005-01-01

    This chapter focuses on small mammals, reptiles, and amphibians that inhabit the grasslands within the Southwestern Region of the USDA Forest Service. The chapter is not intended to be an all inclusive list of species, but rather to address the species that play important roles in grassland ecosystems and that often are associated with the management of grasslands....

  14. Exact completions and small sheaves

    CERN Document Server

    Shulman, Michael

    2012-01-01

    We prove a general theorem which includes most notions of "exact completion". The theorem is that "k-ary exact categories" are a reflective sub-2-category of "k-ary sites", for any regular cardinal k. A k-ary exact category is an exact category with disjoint and universal k-small coproducts, and a k-ary site is a site whose covering sieves are generated by k-small families and which satisfies a weak size condition. For different values of k, this includes the exact completions of a regular category or a category with (weak) finite limits; the pretopos completion of a coherent category; and the category of sheaves on a small site. For a large site with k the size of the universe, it gives a well-behaved "category of small sheaves". Along the way, we define a slightly generalized notion of "morphism of sites", and show that k-ary sites are equivalent to a type of "enhanced allegory".

  15. Small firm transformation through IS

    NARCIS (Netherlands)

    Levy, Margi; Powell, Philip

    2008-01-01

    Globally, Small and Medium-sized Enterprises (SMEs) are encouraged, particularly by governments, to embrace c-business. Fully adopting e-business involves substantial change in firms, both internally and externally. However, there is little understanding of the mechanisms by which such business

  16. Small bowel transplantation: An overview

    NARCIS (Netherlands)

    R.W.F. de Bruin (Ron); E. Heineman (Erik); R.L. Marquet (Richard)

    1994-01-01

    textabstractSmall bowel transplantation (SBT) would, in theory, be the treatment of choice for patients suffering from the short bowel syndrome. Although SBT has been done with a considerable degree of success in some centers [36,145], it is by no means an established or widely applicable therapy fo

  17. Small firm transformation through IS

    NARCIS (Netherlands)

    Levy, Margi; Powell, Philip

    2008-01-01

    Globally, Small and Medium-sized Enterprises (SMEs) are encouraged, particularly by governments, to embrace c-business. Fully adopting e-business involves substantial change in firms, both internally and externally. However, there is little understanding of the mechanisms by which such business tran

  18. Biological productivity in small impoundments

    Science.gov (United States)

    Most ponds and small impoundments are built or used with a principal use in mind. That use may be recreational fishing, commercial aquaculture, waterfowl hunting, potable water storage, irrigation water supply, livestock watering, stormwater retention, landscaping, swimming, or others. In practice, ...

  19. Small artery remodelling in diabetes.

    Science.gov (United States)

    Rosei, Enrico Agabiti; Rizzoni, Damiano

    2010-05-01

    The aim of this article is to briefly review available data regarding changes in the structure of microvessels observed in patients with diabetes mellitus, and possible correction by effective treatment. The development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, small arteries of smooth muscle cells are restructured around a smaller lumen and there is no net growth of the vascular wall, although in some secondary forms of hypertension, a hypertrophic remodelling may be detected. Moreover, in non-insulin-dependent diabetes mellitus a hypertrophic remodelling of subcutaneous small arteries is present. Indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive and diabetic patients, over and above all other known cardiovascular risk factors. Therefore, regression of vascular alterations is an appealing goal of antihypertensive treatment. Different antihypertensive drugs seem to have different effect on vascular structure. In diabetic hypertensive patients, a significant regression of structural alterations of small resistance arteries with drugs blocking the renin-angiotensin system (angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers) was demonstrated. Alterations in the microcirculation represent a common pathological finding, and microangiopathy is one of the most important mechanisms involved in the development of organ damage as well as of clinical events in patients with diabetes mellitus. Renin-angiotensin system blockade seems to be effective in preventing/regressing alterations in microvascular structure.

  20. The Case of Small Retailers

    OpenAIRE

    World Bank Group; World Economic Forum

    2016-01-01

    This report aims to deepen the understanding of barriers to and incentives for the acceptance and use of electronic payments, from the perspective of micro, small and medium retailers (merchants). Developing and accelerating acceptance of electronic payments by these merchants is essential to expanding financial access. A basic transaction account for payments and deposits is considered an...

  1. Modeling Interactions in Small Groups

    Science.gov (United States)

    Heise, David R.

    2013-01-01

    A new theory of interaction within small groups posits that group members initiate actions when tension mounts between the affective meanings of their situational identities and impressions produced by recent events. Actors choose partners and behaviors so as to reduce the tensions. A computer model based on this theory, incorporating reciprocal…

  2. Economics : An emerging small world

    NARCIS (Netherlands)

    Goyal, S; van der Leij, MJ; Moraga-Gonzalez, JL

    2006-01-01

    We study the evolution of social distance among economists over the period 1970-2000. While the number of economists has more than doubled, the distance between them, which was already small, has declined significantly. The key to understanding the short average distances is the observation that eco

  3. Small store presence in Japan

    NARCIS (Netherlands)

    M.A. Carree (Martin); J.C.A. Potjes; A.R. Thurik (Roy)

    1993-01-01

    textabstractThe determinants of the development of small store presence in Japan are investigated using a fixed effects multinomial logit market share model. Large stores tend to have higher market shares in shop-types with increasing shares in consumer expenditures, increasing inventory turnover, a

  4. Small Bodies, Big Discoveries: NASA's Small Bodies Education Program

    Science.gov (United States)

    Mayo, L.; Erickson, K. J.

    2014-12-01

    2014 is turning out to be a watershed year for celestial events involving the solar system's unsung heroes, small bodies. This includes the close flyby of comet C/2013 A1 / Siding Spring with Mars in October and the historic Rosetta mission with its Philae lander to comet 67P/Churyumov-Gerasimenko. Beyond 2014, the much anticipated 2015 Pluto flyby by New Horizons and the February Dawn Mission arrival at Ceres will take center stage. To deliver the excitement and wonder of our solar system's small bodies to worldwide audiences, NASA's JPL and GSFC education teams in partnership with NASA EDGE will reach out to the public through multiple venues including broadcast media, social media, science and math focused educational activities, observing challenges, interactive visualization tools like "Eyes on the Solar System" and more. This talk will highlight NASA's focused education effort to engage the public in small bodies mission science and the role these objects play in our understanding of the formation and evolution of the solar system.

  5. Small is beautiful: models of small neuronal networks.

    Science.gov (United States)

    Lamb, Damon G; Calabrese, Ronald L

    2012-08-01

    Modeling has contributed a great deal to our understanding of how individual neurons and neuronal networks function. In this review, we focus on models of the small neuronal networks of invertebrates, especially rhythmically active CPG networks. Models have elucidated many aspects of these networks, from identifying key interacting membrane properties to pointing out gaps in our understanding, for example missing neurons. Even the complex CPGs of vertebrates, such as those that underlie respiration, have been reduced to small network models to great effect. Modeling of these networks spans from simplified models, which are amenable to mathematical analyses, to very complicated biophysical models. Some researchers have now adopted a population approach, where they generate and analyze many related models that differ in a few to several judiciously chosen free parameters; often these parameters show variability across animals and thus justify the approach. Models of small neuronal networks will continue to expand and refine our understanding of how neuronal networks in all animals program motor output, process sensory information and learn.

  6. Small-scale explosive welding of aluminum

    Science.gov (United States)

    Bement, L. J.

    1972-01-01

    Welding technique uses very small quantities of explosive ribbon to accomplish small-scale lap-welding of aluminum plates. Technique can perform small controlled welding with no length limitations and requires minimal protective shielding.

  7. Propulsion Challenges for Small Spacecraft: 2005

    Institute of Scientific and Technical Information of China (English)

    Vadim Zakirov; LI Luming

    2006-01-01

    Small (<100 kg) spacecrafts are being developed in many countries but their propulsion systems still have many challenges. Although there is demand for small spacecraft propulsion, the number of missions at present is small due to several commercial and technical reasons. Poor performance of existing small spacecraft propulsion systems is one of the main reasons for the small number of missions. Several reasons are given for the poor performance of existing small spacecraft propulsion. Suggested improvements focus on small spacecraft and propulsion hardware mass optimization rather than on specific impulse enhancement. Propellantless propulsion systems are also recommended for small spacecraft interplanetary missions.

  8. Small-Engine Research Laboratory (SERL)

    Data.gov (United States)

    Federal Laboratory Consortium — Description: The Small-Engine Research Laboratory (SERL) is a facility designed to conduct experimental small-scale propulsion and power generation systems research....

  9. Unveiling small sphere's scattering behavior

    CERN Document Server

    Tzarouchis, Dimitrios C; Sihvola, Ari

    2016-01-01

    A classical way for exploring the scattering behavior of a small sphere is to approximate Mie coefficients with a Taylor series expansion. This ansatz delivered a plethora of insightful results, mostly for small spheres supporting electric localized plasmonic resonances. However, many scattering aspects are still uncharted, especially for the case of magnetic resonances. Here, an alternative system ansatz is proposed based on the Pad\\'e approximants for the Mie coefficients. The extracted results reveal new aspects, such as the existence of a self-regulating radiative damping mechanism for the first magnetic resonance. Hence, a systematic way of exploring the scattering behavior is introduced, sharpening our understanding about sphere's scattering behavior and its emergent functionalities.

  10. INNOVATION IN BRAZILIAN SMALL COMPANIES

    Directory of Open Access Journals (Sweden)

    Tonny Kerley de Alencar Rodrigues

    2015-03-01

    Full Text Available This study aims to identify the interfaces and boundaries of innovation orientation of Brazilian MSEs because despite the importance of innovation for Brazilian MSEs, a thorough analysis of such initiatives in Brazil still has not actually happened. The search was developed from a quantitative approach, of applied nature and descriptive. For that a structured questionnaire was used where were interviewed 700 MSEs using a probabilistic sampling. The study offers two important conclusions. The challenges for innovation can be perceived along three dimensions: design innovation, the implementation of innovation and functional area of innovation. And the data confirms that small Brazilian companies generally have difficulties to sell their innovations. The study offers two important conclusions. The challenges for innovation can be perceived along three dimensions: design innovation, the implementation of innovation and functional area of innovation. And the data confirms that small Brazilian companies generally have difficulties to sell their innovations.

  11. Small Business Social Responsibility Communication

    DEFF Research Database (Denmark)

    Morsing, Mette; Spence, Laura J.

    2015-01-01

    of conduct and CSR reporting (i.e. CSR as a “regime of truth”, Foucault) and an internally prescribed ethos of a personal philosophy of ethics and norms such as family identity and employee values, concern for local community and legacy of the company (i.e. CSR as personally held values). We contribute......Purpose: Corporate social responsibility communication by small and medium sized enterprises is theorized to form the concept of Small Business Social Responsibility (SBSR) Communication. Design/methodology/approach: This is a conceptual paper that draws on Foucault’s theory of governmentality...... to develop a theoretical explanation for SBSR communication. Findings: Our analysis conceptualizes the ‘governmentality dilemma’ as SBSR managers face two simultaneous and potentially counterproductive expectations: responding to externally prescribed expectations, norms and standards such as branding, codes...

  12. Small-for-sizesyndromeinlivingdonorliver transplantation

    Institute of Scientific and Technical Information of China (English)

    Shintaro Yagi; Shinji Uemoto

    2012-01-01

    When the graft volume is too small to satisfy the recipient's metabolic demand, the recipient may thus experience small-for-size syndrome (SFSS). Because the occurrence of SFSS is determined by not only the liver graft volume but also a combination of multiple negative factors, the deifnitions of small-for-size graft (SFSG) and SFSS are different in each institute and at each time. In the clinical setting, surgical inlfow modulation and maximizing the graft outlfow are keys to overcoming SFSS. Accordingly, relatively smaller-sized grafts can be used with surgical modiifcation and pharmacological manipulation targeting portal circulation and liver graft quality. Therefore, the focus of the SFSG issue is now shifting from how to obtain a larger graft from the living donor to how to manage the use of a smaller graft to save the recipient, considering donor safety to be a priority.

  13. Small Business Social Responsibility Communication

    DEFF Research Database (Denmark)

    Morsing, Mette; Spence, Laura J.

    2015-01-01

    /implications: The conceptualization of SBSR communication would be enhanced by in-depth, nuanced empirical research. Practical implications: This paper has policy implications for those seeking to understand CSR among SMEs using formal communication mechanisms as a metric and control. Our paper suggests this to be an inadequate......Purpose: Corporate social responsibility communication by small and medium sized enterprises is theorized to form the concept of Small Business Social Responsibility (SBSR) Communication. Design/methodology/approach: This is a conceptual paper that draws on Foucault’s theory of governmentality...... to develop a theoretical explanation for SBSR communication. Findings: Our analysis conceptualizes the ‘governmentality dilemma’ as SBSR managers face two simultaneous and potentially counterproductive expectations: responding to externally prescribed expectations, norms and standards such as branding, codes...

  14. Small Countries with Volatile Revenue

    OpenAIRE

    Naoko C. Kojo

    2015-01-01

    Bhutan and Botswana share a number of similarities. The two countries, land locked small states, have grown rapidly over the past few decades, boosted by sustained, large-scale inflows of foreign exchange. Botswana’s annual real growth rate averaged 9 percent over the past 40 years, driven by diamond exploration, whereas Bhutan has taken full advantage of generous foreign aid inflows to ac...

  15. Wastewater services for small communities.

    Science.gov (United States)

    Gray, S; Booker, N

    2003-01-01

    Connection to centralised regional sewage systems has been too expensive for small-dispersed communities, and these townships have traditionally been serviced by on-site septic tank systems. The conventional on-site system in Australia has consisted of an anaerobic holding tank followed by adsorption trenches. This technique relies heavily on the uptake of nutrients by plants for effective removal of nitrogen and phosphorus from the effluent, and is very seasonal in its efficiency. Hence, as these small communities have grown in size, the environmental effects of the septic tank discharges have become a problem. In locations throughout Australia, such as rural Victoria and along the Hawkesbury-Nepean River, septic tanks as being replaced with the transport of sewage to regional treatment plants. For some isolated communities, this can mean spending 20,000 dollars-40,000 dollars/household, as opposed to more common connection prices of 7,000 dollars/household. This paper explores some alternative options that might be suitable for these small communities, and attempts to identify solutions that provide acceptable environmental outcomes at lower cost. The types of alternative systems that are assessed in the paper include local treatment systems, separate blackwater and greywater collection and treatment systems both with and without non-potable water recycling, a small township scale treatment plant compared to either existing septic tank systems or pumping to a remote regional treatment facility. The work demonstrated the benefits of a scenario analysis approach for the assessment of a range of alternative systems. It demonstrated that some of the alternatives systems can achieve better than 90% reductions in the discharge of nutrients to the environment at significantly lower cost than removing the wastewater to a remote regional treatment plant. These concepts allow wastewater to be retained within a community allowing for local reuse of treated effluent.

  16. Small intestinal bacterial overgrowth syndrome

    Institute of Scientific and Technical Information of China (English)

    Jan; Bures; Jiri; Cyrany; Darina; Kohoutova; Miroslav; Frstl; Stanislav; Rejchrt; Jaroslav; Kvetina; Viktor; Vorisek; Marcela; Kopacova

    2010-01-01

    Human intestinal microbiota create a complex polymi-crobial ecology. This is characterised by its high population density, wide diversity and complexity of interaction. Any dysbalance of this complex intestinal microbiome, both qualitative and quantitative, might have serious health consequence for a macro-organism, including small intestinal bacterial overgrowth syndrome (SIBO).SIBO is defined as an increase in the number and/or alteration in the type of bacteria in the upper gastro-intestinal tract. There...

  17. Document management for small business

    OpenAIRE

    Valkonen, Juho

    2015-01-01

    The objective of the thesis was to find out the most important things about document management which are needed for selecting a proper document management system for a small business. The thesis explores several document management systems and the differences between them. The goal of the development project was to find the most suitable system for the client and to define document management processes for the company. The theory part of the thesis focuses on different document manageme...

  18. Evolution of small prokaryotic genomes

    OpenAIRE

    Martínez-Cano, David J.; Reyes-Prieto, Mariana; Martínez-Romero, Esperanza; Partida-Martínez, Laila P.; Latorre, Amparo; Moya, Andrés; Delaye, Luis

    2015-01-01

    As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ∼800 genes as well as endosymbiotic bacteria with as few as ∼140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent ...

  19. Evolution of small prokaryotic genomes

    OpenAIRE

    David José Martínez-Cano; Mariana eReyes-Prieto; Esperanza eMartinez-Romero; Laila Pamela Partida-Martinez; Amparo eLatorre; Andres eMoya; Luis eDelaye

    2015-01-01

    As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ~800 genes as well as endosymbiotic bacteria with as few as ~140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent ...

  20. Desmoplastic small round cell tumour

    Energy Technology Data Exchange (ETDEWEB)

    Tan, T.H.L. [North District Hospital, Fanling, Kowloon (Hong Kong). Radiology Department; Ong, K.L. [Prince of Wales Hospital, Shatin, Kowloon (Hong Kong). Accident and Emergency Department; Au, Y.M.C. [Princess Margarete Hospital, Kowloon, (Hong Kong). Department of Radiology

    1998-11-01

    The present report describes a rare case of primary desmoplastic small cell tumour of the recto-sigmoid colon with hepatic metastases and lymphadenopathy. There are no pathognomonic radiological features and often their features overlap with other diseases including lymphoma. Histology is necessary to confirm this diagnosis. Unfortunately despite aggressive therapy, the prognosis for this disease is poor. Copyright (1998) Blackwell Science Pty Ltd 8 refs., 1 fig.

  1. Small Break Air Ingress Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chang Oh; Eung Soo Kim

    2011-09-01

    The small break air-ingress experiment, described in this report, is designed to investigate air-ingress phenomena postulated to occur in pipes in a very high temperature gas-cooled reactor (VHTRs). During this experiment, air-ingress rates were measured for various flow and break conditions through small holes drilled into a pipe of the experimental apparatus. The holes were drilled at right angles to the pipe wall such that a direction vector drawn from the pipe centerline to the center of each hole was at right angles with respect to the pipe centerline. Thus the orientation of each hole was obtained by measuring the included angle between the direction vector of each hole with respect to a reference line anchored on the pipe centerline and pointing in the direction of the gravitational force. Using this reference system, the influence of several important parameters on the air ingress flow rate were measured including break orientation, break size, and flow velocity . The approach used to study the influence of these parameters on air ingress is based on measuring the changes in oxygen concentrations at various locations in the helium flow circulation system as a function of time using oxygen sensors (or detectors) to estimate the air-ingress rates through the holes. The test-section is constructed of a stainless steel pipe which had small holes drilled at the desired locations.

  2. Evolution of small prokaryotic genomes

    Directory of Open Access Journals (Sweden)

    David José Martínez-Cano

    2015-01-01

    Full Text Available As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ~800 genes as well as endosymbiotic bacteria with as few as ~140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent role. However, new experimental data suggest that selective processes may be at operation as well for endosymbiotic prokaryotes at least during the first stages of genome reduction. Endosymbiotic prokaryotes have evolved diverse strategies for living with reduced gene sets inside a host-defined medium. These include utilization of host-encoded functions (some of them coded by genes acquired by gene transfer from the endosymbiont and/or other bacteria; metabolic complementation between co-symbionts; and forming consortiums with other bacteria within the host. Recent genome sequencing projects of intracellular mutualistic bacteria showed that previously believed universal evolutionary trends like reduced G+C content and conservation of genome synteny are not always present in highly reduced genomes. Finally, the simplified molecular machinery of some of these organisms with small genomes may be used to aid in the design of artificial minimal cells. Here we review recent genomic discoveries of the biology of prokaryotes endowed with small gene sets and discuss the evolutionary mechanisms that have been proposed to explain their peculiar nature.

  3. Superconductivity of small metal grains

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Renrong; CHEN; Zhiqian; ZHU; Shunquan

    2005-01-01

    The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

  4. 78 FR 48537 - Small Business Innovation Research and Small Business Technology Transfer Programs...

    Science.gov (United States)

    2013-08-08

    ... ADMINISTRATION Small Business Innovation Research and Small Business Technology Transfer Programs... Administration (SBA) is publishing the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) program Commercialization Benchmark for the 11 participating agencies for public comment...

  5. A Quantitative Analytical Method to Test for Salt Effects on Giant Unilamellar Vesicles

    DEFF Research Database (Denmark)

    Hadorn, Maik; Bönzli, Eva; Eggenberger Hotz, Peter

    2011-01-01

    Today, free-standing membranes, i.e. liposomes and vesicles, are used in a multitude of applications, e.g. as drug delivery devices and artificial cell models. Because current laboratory techniques do not allow handling of large sample sizes, systematic and quantitative studies on the impact...

  6. Riboflavin and chlorophyll as photosensitizers in electroformed giant unilamellar vesicles as food models

    DEFF Research Database (Denmark)

    Wang, Hui Jing; Liang, Ran; du, Hui Hui

    2017-01-01

    for hydrophilic riboflavin, while lipophilic chlorophyll a initiated GUV budding and subsequent disintegration under light irradiation, indicating that lipophilic photosensitizers are the more important in such structured lipids. Lipophilic β-carotene provided protection against oxidative damage induced...... by chlorophyll a as shown by an increased lag phase for budding; however, it had no effect on subsequent budding rate. Hydrophilic puerarin alone exhibited little protection in terms of lag phase, but decreased together with β-carotene budding rate after the lag phase by a factor of more than 2, showing a clear...

  7. Shape deformations of giant unilamellar vesicles with a laser tweezer array

    Science.gov (United States)

    Losert, Wolfgang; Poole, Cory; Bradford, Peter; English, Doug

    2004-10-01

    Vesicles are phospholipid bilayers that form a surface enclosing a volume of water or solution. They are of importance as model systems to study cells, as well as having practical applications such as containers for performing nanochemistry and facilitating drug delivery. Their properties have been studied for decades. Using a holographic laser tweezer array (LTA), which converts a single laser beam into many laser tweezer points, we stretch the vesicles in controlled ways from several points at once, measuring each force applied. Here, we present data on shape deformations of simple, spherical vesicles and on membrane fracture.

  8. Fundamental Studies of Assembly and Mechanical Properties of Lipid Bilayer Membranes and Unilamellar Vesicles

    Science.gov (United States)

    Wang, Xi

    This dissertation work focuses on: (i) obtaining a phospholipid bilayer membrane (LBM)/conducting electrode system with low defect density and optimized rigidity; (ii) investigating vesicle stability and mechanical properties. LBM is a simplified yet representative cell membrane model. LBMs assembled on conductive surfaces can probe protein-LBM interactions activities electrochemically. Sterically stabilized vesicles could be used as cell models or for drug delivery. The main challenges for LBM assembly on gold are vesicles do not spontaneously rupture to form LBMs on gold and the roughness of the gold substrate has considerable influence on molecular film defect density. In this study, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles were functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine- N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio)propionate] (DSPE-PEG-PDP) to yield stable LBMs on gold without surface modification. A template-stripping method was used to obtain atomically flat and pristine gold surfaces. The critical force to initiate vesicle rupture decreases with increasing DSPE-PEG-PDP concentration, indicating that gold-thiolate bonding between DSPE-PEG-PDP and gold substrates promotes LBM formation. Mechanical properties of LBMs and vesicles were investigated as a function of DSPE-PEG-PDP concentration via Atomic Force Microscopy. The elastic moduli of LBMs were determined with DSPE-PEG-PDP concentration ranging from 0mol% to 24mol% and were found to depend on PEG chain conformation. Incorporating DSPE-PEG-PDP molecules with PEG in mushroom conformation results in a decrease of LBM rigidity, while incorporating PEG in brush conformation leads to LBM stiffening. Contrarily, mechanical properties of functionalized vesicles did not vary significantly by varying DSPE-PEG-PDP concentration. LBM with tunable rigidity by adjusting DSPE-PEG-PDP concentration provides a versatile cell membrane model for studying protein or peptide activities. The study of vesicle rupture mechanics and mechanical properties provide a means of understanding triggered release of internal payload from vesicular structures. POPC vesicles were also deposited on graphene; a transparent and highly conductive electrode. A combination method of diffusion bonding and template-stripping was used to prepare metal surfaces for graphene growth without concerns of outgassing, thermal and chemical compatibility. Continuous LBM formed on graphene-single crystal Cu, while tubular features with 120°C patterns formed on graphene-Cu foil, indicating the step edge of Cu below graphene may also guide the assembly of tubular LBM features on graphene.

  9. Formation of supported phospholipid bilayers from unilamellar vesicles investigated by atomic force microscopy

    NARCIS (Netherlands)

    Reviakine, [No Value; Brisson, A

    2000-01-01

    Since their introduction through the work of McConnell et al. in the early 80s, supported phospholipid bilayers (SPBs) have proven to be a versatile model system for investigating a wide variety of phenomena. Despite their continuous application in fundamental as well as applied research fields, the

  10. Caspase-8 Binding to Cardiolipin in Giant Unilamellar Vesicles Provides a Functional Docking Platform for Bid

    DEFF Research Database (Denmark)

    Jalmar, Olivier; Franc¸ois-Moutal, Liberty; García-Sáez, Ana-Jesus

    2013-01-01

    Caspase-8 is involved in death receptor-mediated apoptosis in type II cells, the proapoptotic programme of which is triggered by truncated Bid. Indeed, caspase-8 and Bid are the known intermediates of this signalling pathway. Cardiolipin has been shown to provide an anchor and an essential activa...

  11. 78 FR 59798 - Small Business Subcontracting: Correction

    Science.gov (United States)

    2013-09-30

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION 13 CFR Part 125 RIN 3245-AG22 Small Business Subcontracting: Correction AGENCY: U.S. Small..., 2013 (78 FR 42391). The document amended SBA's regulations governing small business subcontracting...

  12. Small Group Communication in the 1980's.

    Science.gov (United States)

    Neer, Michael R., Ed.

    1981-01-01

    This special edition of "Communication" brings together the work of nine leading scholars of small group communication. The following topics are discussed: (1) small group communication research in the 1980s; (2) unanswered questions in research on communication in the small group; (3) emerging trends in small group research; (4) structure in…

  13. 76 FR 74749 - Small Business Subcontracting

    Science.gov (United States)

    2011-12-01

    ... small business subcontracting plan is required, currently valued above $1.5 million for construction and... contracting officer is responsible for monitoring and evaluating small business subcontracting plan...; ] SMALL BUSINESS ADMINISTRATION 13 CFR Parts 121 and 125 RIN 3245-AG22 Small Business...

  14. Japanese Small Type Coastal Whaling

    Directory of Open Access Journals (Sweden)

    Sue Fisher

    2016-07-01

    Full Text Available 2016 marks the 70th anniversary of the International Convention for the Regulation of Whaling (ICRW as well as the 30th anniversary of the International Whaling Commission’s (IWC moratorium on commercial whaling. It also marks three decades of effort by Japan to overturn this ban. Its strategy to circumvent the moratorium by issuing permits to kill protected whales for scientific research is famous—even the subject of a 2014 lawsuit at the International Court of Justice. Less well known is Japan’s strategy to overturn the ban by persuading the Commission to authorise a category of commercial whaling known as Small Type Coastal Whaling (STCW that is conducted on minke and other small whales in Japanese waters but has never been regulated, or even formally recognised, by the IWC. For three decades Japan has sought STCW catch limits for four communities which it claims are still suffering distress as a result of the moratorium. While the Commission has rejected each proposal, mainly citing concerns that the commercial nature and purpose of STCW violates the moratorium, Japan has persisted, exhibiting great flexibility in its approach. Its tactics changed significantly in 2014; it no longer denied (or defended the commerciality of the hunt, but argued that it is irrelevant since it sought only a small exemption to the moratorium which would remain intact for all other populations. This is a perspective on Japan’s evolving STCW strategy and the risk that lifting, or modifying, the moratorium would pose to the conservation of whales.

  15. Rain on small tropical islands

    Science.gov (United States)

    Sobel, A. H.; Burleyson, C. D.; Yuter, S. E.

    2011-04-01

    A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997-2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow

  16. Small angle scattering and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, J.P. [Laboratoire Leon Brillouin (LLB) - Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1996-12-31

    The determination of polymer structure is a problem of interest for both statistical physics and industrial applications. The average polymer structure is defined. Then, it is shown why small angle scattering, associated with isotopic substitution, is very well suited to the measurement of the chain conformation. The corresponding example is the old, but pedagogic, measurement of the chain form factor in the polymer melt. The powerful contrast variation method is illustrated by a recent determination of the concentration profile of a polymer interface. (author) 12 figs., 48 refs.

  17. GEF small grants programme - overview

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-01

    This paper describes the GEF small grants program which seeks to enhance the role of households and communities in conserving global biodiversity, mitigating global climate change, and protecting international waters. Grants up to $50k have been granted for projects in 33 countries, with plans for 12 other countries. The author describes the framework that the program works under, and the methodology followed in developing and planning projects. The approach to climate change concerns is to emphasize the development of non-carbon energy development activities to provide energy sources and economic development.

  18. Small Bowel Review: Part I

    Directory of Open Access Journals (Sweden)

    ABR Thomson

    2000-01-01

    Full Text Available In the past year, there have been many advances in the area of small bowel physiology and pathology. More than 1500 papers were assessed in preparation for this review. Some were selected and reviewed, with a particular focus on presenting clinically useful information for the practising gastroenterologist. Relevant review articles have been highlighted, and important clinical learning points have been stressed. The topics are varied in scope, and wherever possible show a logical progression from basic physiology to pathophysiology to clinical disorders and management.

  19. Small Bowel Review: Part II

    Directory of Open Access Journals (Sweden)

    ABR Thomson

    1996-01-01

    Full Text Available Major scientific advances have been made over the past few years in the areas of small bowel physiology, pathology, microbiology and clinical sciences. Over 1000 papers have been reviewed and a selective number are considered here. Wherever possible, the clinical relevance of these advances have been identified. Topics discussed are enterocyte proliferation and growth factors; amino acids, peptides and allergies; motility; salt and water absorption and secretion – diarrhea; vitamins and minerals; early development and ageing of the intestine; and ethanol effects.

  20. Chlamydial infections in small ruminants.

    Science.gov (United States)

    Nietfeld, J C

    2001-07-01

    Chlamydophila abortus (formerly Chlamydia psittaci) is one of the most important causes of reproductive failure in sheep and goats, especially in intensively managed flocks. The disease is usually manifested as abortion in the last 2 to 3 weeks of gestation, regardless of when the animal was infected. Ewes that abort are resistant to future reproductive failure due to C. abortus, but they become inapparent carriers and persistently shed the organism from their reproductive tracts during estrus. Chlamydophila pecorum is the other member of the genus that affects small ruminants, and it is recognized as a primary cause of keratoconjunctivitis in sheep and goats and of polyarthritis in sheep.

  1. Small intestinal tophus mimicking tumor

    Directory of Open Access Journals (Sweden)

    Pragya Katoch

    2014-03-01

    Full Text Available A 72 year old male with hypertension, diabetes mellitus type 2 and previous gouty arthritis presented with weight loss, nausea, and vomiting. Ultrasound and CT scanning of the abdomen revealed a circumscribed tumor mass of the jejunum, 3.7 cm in diameter. Microscopic examination of the resected jejunum revealed the tumor to be a gouty tophus. To the best of our knowledge, three cases of tophi in the large intestine have previously been reported but none in the small intestine.

  2. Trust Propagation in Small Worlds

    DEFF Research Database (Denmark)

    Gray, Elizabeth; Seigneur, Jean-Marc; Chen, Yong

    2003-01-01

    The possibility of a massive, networked infrastructure of diverse entities partaking in collaborative applications with each other increases more and more with the proliferation of mobile devices and the development of ad hoc networking technologies. In this context, traditional security measures...... do not scale well. We aim to develop trust-based security mechanisms using small world concepts to optimise formation and propagation of trust amongst entities in these vast networks. In this regard, we surmise that in a very large mobile ad hoc network, trust, risk, and recommendations can...

  3. Small signal microwave amplifier design

    CERN Document Server

    Grosch, Theodore

    2000-01-01

    This book explains techniques and examples for designing stable amplifiers for high-frequency applications in which the signal is small and the amplifier circuit is linear. An in-depth discussion of linear network theory provides the foundation needed to develop actual designs. Examples throughout the book will show you how to apply the knowledge gained in each chapter leading to the complex design of low noise amplifiers. Many exercises at the end of each chapter will help students to practice their skills. The solutions to these design problems are available in an accompanying solutions book

  4. Investigation of the Influence of Sucrose and Cholesterol on the Phase Transition Temperature of nanoliposomal formulation besides using particle size Reduction Techniques (Ultrasonication/High Pressure Homogenization

    Directory of Open Access Journals (Sweden)

    Z Malaei-Balasi

    2017-05-01

    Full Text Available Introduction: The successful application of nanoliposoms as an effective drug delivery system depends on their stability in the medium. In this article, influence of additive materials such as cholesterol and sucrose besides two natural and synthesized phospholipids have been investigated. Methods: In the present study, designing and synthesis of nanoliposomal formulations were prepared using thin film method. This liposomal suspension was downsized by two methods, the high-pressure homogenizer and ultrasound to form small unilamellar vesicles. The size distributions, zeta potentials and phase transition temperature of formulations were all determined by a zetasizer and differential scanning calorimetry(DSC. In addition, the contribution of nanoliposomal formulation has been investigated by HPLC and FTIR methods. Results: Results of the DSC measurments indicated that incorporation of unsaturated phospholipid (SOY PC may cause phase separation with partial miscibility in the liposome bilayer containing of DPPG. The optimal nanoliposomal formulation was composed of (DPPC: CHOL: mPEG2000-DSPE with the mole percents equal to (83:15:2, respectively. In addition, sucrose has been used in the formulation with a total amounts six times greater than that of the lipids. The properties of optimized nanoliposome have been shown as the size average 104nm, zeta potential 8.04mv and phase transition temperature of lipid less than 37°C which were stable enough to be utilized for loading and releasing bioactives in body temperature. Conclusion: Finally the produced nanoliposomes were stable vesicles in the proper size, phase transition temperature and surface charge without any aggregation and fusion.

  5. Reactions of small molecular systems

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, C. [Univ. of Southern California, Los Angeles, CA (United States)

    1993-12-01

    This DOE program remains focused on small molecular systems relevant to combustion. Though a number of experimental approaches and machines are available for this research, the authors` activities are centered around the high-n Rydberg time-of-flight (HRTOF) apparatus in this laboratory. One student and one postdoc carry out experiments with this machine and also engage in small intra-group collaborations involving shared equipment. This past year was more productive than the previous two, due to the uninterrupted operation of the HRTOF apparatus. Results were obtained with CH{sub 3}OH, CH{sub 3}SH, Rg-HX complexes, HCOOH, and their deuterated analogs where appropriate. One paper is in print, three have been accepted for publication, and one is under review. Many preliminary results that augur well for the future were obtained with other systems such as HNO{sub 3}, HBr-HI complexes, toluene, etc. Highlights from the past year are presented below that display some of the features of this program.

  6. Small crater populations on Vesta

    CERN Document Server

    Marchi, S; O'Brien, D P; Schenk, P; Mottola, S; De Sanctis, M C; Kring, D A; Williams, D A; Raymond, C A; Russell, C T

    2013-01-01

    The NASA Dawn mission has extensively examined the surface of asteroid Vesta, the second most massive body in the main belt. The high quality of the gathered data provides us with an unique opportunity to determine the surface and internal properties of one of the most important and intriguing main belt asteroids (MBAs). In this paper, we focus on the size frequency distributions (SFDs) of sub-kilometer impact craters observed at high spatial resolution on several selected young terrains on Vesta. These small crater populations offer an excellent opportunity to determine the nature of their asteroidal precursors (namely MBAs) at sizes that are not directly observable from ground-based telescopes (i.e., below ~100 m diameter). Moreover, unlike many other MBA surfaces observed by spacecraft thus far, the young terrains examined had crater spatial densities that were far from empirical saturation. Overall, we find that the cumulative power-law index (slope) of small crater SFDs on Vesta is fairly consistent with...

  7. Small Bowel Dissemination of Coccidioidomycosis

    Directory of Open Access Journals (Sweden)

    Shengmei Zhou

    2015-01-01

    Full Text Available Gastrointestinal coccidioidomycosis is extremely rare, with less than 10 cases reported in the literature. We report a case of small bowel dissemination of coccidioidomycosis in a 21-year-old African American male with a history of living in San Joaquin Valley. The patient presented with one week of abdominal pain, nausea, shortness of breath, intermittent fever, and sweat, and one month of abdominal distention. A chest radiograph revealed complete effusion of left lung. A computed tomography scan of the abdomen showed diffuse small bowel thickening and enhancement, as well as omental and peritoneal nodules, and ascites. The coccidioidal complement fixation titer was 1 : 256. The duodenal biopsy revealed many spherules filled with round fungal endospores. Later, blood fungal culture showed positivity for Coccidioides immitis. The final diagnosis is disseminated coccidioidomycosis involving lungs, blood, and duodenum. Despite aggressive antifungal therapy, the patient’s clinical situation deteriorated and he succumbed to multisystem organ failure one and half months later. A high index of suspicion for gastrointestinal coccidioidomycosis should be maintained in patients from an endemic area presenting as abdominal distention and pain.

  8. Small Molecules Target Carcinogenic Proteins

    Science.gov (United States)

    Gradinaru, Claudiu

    2009-03-01

    An ingenious cellular mechanism of effecting protein localization is prenylation: the covalent attachment of a hydrophobic prenyl group to a protein that facilitates protein association with cell membranes. Fluorescence microscopy was used to investigate whether the oncogenic Stat3 protein can undergo artificial prenylation via high-affinity prenylated small-molecule binding agents and thus be rendered inactive by localization at the plasma membrane instead of nucleus. The measurements were performed on a home-built instrument capable of recording simultaneously several optical parameters (lifetime, polarization, color, etc) and with single-molecule sensitivity. A pH-invariant fluorescein derivative with double moiety was designed to bridge a prenyl group and a small peptide that binds Stat3 with high affinity. Confocal fluorescence images show effective localization of the ligand to the membrane of liposomes. Stat3 predominantly localizes at the membrane only in the presence of the prenylated ligand. Single-molecule FRET (fluorescence resonance energy transfer) between donor-labeled prenylated agents and acceptor-labeled, surface tethered Stat3 protein is used to determine the dynamic heterogeneity of the protein-ligand interaction and follow individual binding-unbinding events in real time. The data indicates that molecules can effect protein localization, validating a therapeutic design that influences protein activity via induced localization.

  9. Small Spacecraft for Planetary Science

    Science.gov (United States)

    Baker, John; Castillo-Rogez, Julie; Bousquet, Pierre-W.; Vane, Gregg; Komarek, Tomas; Klesh, Andrew

    2016-07-01

    As planetary science continues to explore new and remote regions of the Solar system with comprehensive and more sophisticated payloads, small spacecraft offer the possibility for focused and more affordable science investigations. These small spacecraft or micro spacecraft (electronics, advanced manufacturing for lightweight structures, and innovative propulsion are making it possible to fly much more capable micro spacecraft for planetary exploration. While micro spacecraft, such as CubeSats, offer significant cost reductions with added capability from advancing technologies, the technical challenges for deep space missions are very different than for missions conducted in low Earth orbit. Micro spacecraft must be able to sustain a broad range of planetary environments (i.e., radiations, temperatures, limited power generation) and offer long-range telecommunication performance on a par with science needs. Other capabilities needed for planetary missions, such as fine attitude control and determination, capable computer and data handling, and navigation are being met by technologies currently under development to be flown on CubeSats within the next five years. This paper will discuss how micro spacecraft offer an attractive alternative to accomplish specific science and technology goals and what relevant technologies are needed for these these types of spacecraft. Acknowledgements: Part of this work is being carried out at the Jet Propulsion Laboratory, California Institute of Technology under contract to NASA. Government sponsorship acknowledged.

  10. Small RNA in rice genome

    Institute of Scientific and Technical Information of China (English)

    王凯; 朱小蓬; 钟兰; 陈润生

    2002-01-01

    Rice has many characteristics of a model plant. The recent completion of the draft of the rice genome represents an important advance in our knowledge of plant biology and also has an important contribution to the understanding of general genomic evolution. Besides the rice genome finishing map, the next urgent step for rice researchers is to annotate the genes and noncoding functional sequences. The recent work shows that noncoding RNAs (ncRNAs) play significant roles in biological systems. We have explored all the known small RNAs (a kind of ncRNA) within rice genome and other six species sequences, including Arabidopsis, maize, yeast, worm, mouse and pig. As a result we find 160 out of 552 small RNAs (sRNAs) in database have homologs in 108 rice scaffolds, and almost all of them (99.41%) locate in intron regions of rice by gene predication. 19 sRNAs only appear in rice. More importantly, we find two special U14 sRNAs: one is located in a set of sRNA ZMU14SNR9(s) which only appears in three plants, 86% sequences of them can be compared as the same sequence in rice, Arabidopsis and maize; the other conserved sRNA XLHS7CU14 has a segment which appears in almost all these species from plants to animals. All these results indicate that sRNA do not have evident borderline between plants and animals.

  11. Small Space Launch: Origins & Challenges

    Science.gov (United States)

    Freeman, T.; Delarosa, J.

    2010-09-01

    The United States Space Situational Awareness capability continues to be a key element in obtaining and maintaining the high ground in space. Space Situational Awareness satellites are critical enablers for integrated air, ground and sea operations, and play an essential role in fighting and winning conflicts. The United States leads the world space community in spacecraft payload systems from the component level into spacecraft, and in the development of constellations of spacecraft. In the area of launch systems that support Space Situational Awareness, despite the recent development of small launch vehicles, the United States launch capability is dominated by an old, unresponsive and relatively expensive set of launchers in the Expandable, Expendable Launch Vehicles (EELV) platforms; Delta IV and Atlas V. The United States directed Air Force Space Command to develop the capability for operationally responsive access to space and use of space to support national security, including the ability to provide critical space capabilities in the event of a failure of launch or on-orbit capabilities. On 1 Aug 06, Air Force Space Command activated the Space Development & Test Wing (SDTW) to perform development, test and evaluation of Air Force space systems and to execute advanced space deployment and demonstration projects to exploit new concepts and technologies, and rapidly migrate capabilities to the warfighter. The SDTW charged the Launch Test Squadron (LTS) with the mission to develop the capability of small space launch, supporting government research and development space launches and missile defense target missions, with operationally responsive spacelift for Low-Earth-Orbit Space Situational Awareness assets as a future mission. This new mission created new challenges for LTS. The LTS mission tenets of developing space launches and missile defense target vehicles were an evolution from the squadrons previous mission of providing sounding rockets under the Rocket

  12. Amyloidosis of the small intestine

    Energy Technology Data Exchange (ETDEWEB)

    Kala, Zdenek [Department of Surgery, Faculty Hospital Brno, Jihlavska 20, 62500 Brno (Czech Republic)]. E-mail: zkala@tiscali.cz; Valek, Vlastimil [Department of Radiology, Faculty Hospital Brno, Jihlavska 20, 62500 Brno (Czech Republic)]. E-mail: v.valek@fnbrno.cz; Kysela, Petr [Department of Surgery, Faculty Hospital Brno, Jihlavska 20, 62500 Brno (Czech Republic)]. E-mail: pkysel@email.cz

    2007-07-15

    Amyloidosis is a rare disease characterized by forming pathological protein deposits - amyloid - in many organs and tissues. This decreases their functionality. The aim of this small study was to determine, whether the radiological picture of the small intestine involvement in amyloidosis is in some sense specific as sometimes described in literature giving rise to high suspicion for the disease in symptomatic patients. Material and methods: The prospective study comprising seven patients hospitalized in surgical department is presented together with a survey on the disease, its appearance in radiological imaging. All patients underwent abdominal ultrasound (ATL 5000 HDI, 7-12 MHz linear probe, no contrast enhancement, supine position), abdominal CT (Somatom Plus, Siemens, single detector, conventional abdominal CT protocol) and enteroclysis (Micropaque suspension 300 ml, application rate of 75 ml/min, dilution with HP-7000 being 1:1 and HP-7000 solution 2000 ml, application rate of 120 ml/min.). Results: The amyloid deposits in the small intestine could be visualized in five of seven patients with the disease. Enteroclysis revealed a diffuse slowed down intestinal motility with an obstruction-like picture in all of our seven patients. The intestinal secretion was normal, plicae were getting polyp-like shape in five of them forming so called 'thumb printing' picture. CT showed thickening of the intestinal wall due to deposits with poor blood supply and contrast retention in five of seven patients. Ultrasound visualized thickened, hypoechoic nodular plicae and slowed down motility in these five patients. The most striking finding was the pathological deposits in the intestinal wall were highly hypo-vascular. However, this picture is very similar to that of ischemic enteritis. All seven patients had proven amyloid deposits from bioptic specimens. Conclusion: The diagnosis of amyloidosis must be supported by bioptic examination as it has no pathognomic

  13. Small molecule fluoride toxicity agonists.

    Science.gov (United States)

    Nelson, James W; Plummer, Mark S; Blount, Kenneth F; Ames, Tyler D; Breaker, Ronald R

    2015-04-23

    Fluoride is a ubiquitous anion that inhibits a wide variety of metabolic processes. Here, we report the identification of a series of compounds that enhance fluoride toxicity in Escherichia coli and Streptococcus mutans. These molecules were isolated by using a high-throughput screen (HTS) for compounds that increase intracellular fluoride levels as determined via a fluoride riboswitch reporter fusion construct. A series of derivatives were synthesized to examine structure-activity relationships, leading to the identification of compounds with improved activity. Thus, we demonstrate that small molecule fluoride toxicity agonists can be identified by HTS from existing chemical libraries by exploiting a natural fluoride riboswitch. In addition, our findings suggest that some molecules might be further optimized to function as binary antibacterial agents when combined with fluoride. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Disturbances in small bowel motility.

    LENUS (Irish Health Repository)

    Quigley, E M

    2012-02-03

    Recently, the small intestine has become the focus of investigation as a potential site of dysmotility in the irritable bowel syndrome (IBS). A number of motor abnormalities have been defined in some studies, and include \\'clustered\\' contractions, exaggerated post-prandial motor response and disturbances in intestinal transit. The significance of these findings remains unclear. The interpretation of available studies is complicated by differences in subject selection, the direct influence of certain symptoms, such as diarrhoea and constipation, and the interference of compounding factors, such as stress and psychopathology. Dysmotility could also reflect autonomic dysfunction, disturbed CNS control and the response to heightened visceral sensation or central perception. While motor abnormalities may not explain all symptoms in IBS, sensorimotor interactions may be important in symptom pathogenesis and deserve further study.

  15. The significance of small streams

    Science.gov (United States)

    Wohl, Ellen

    2017-09-01

    Headwaters, defined here as first- and secondorder streams, make up 70%‒80% of the total channel length of river networks. These small streams exert a critical influence on downstream portions of the river network by: retaining or transmitting sediment and nutrients; providing habitat and refuge for diverse aquatic and riparian organisms; creating migration corridors; and governing connectivity at the watershed-scale. The upstream-most extent of the channel network and the longitudinal continuity and lateral extent of headwaters can be difficult to delineate, however, and people are less likely to recognize the importance of headwaters relative to other portions of a river network. Consequently, headwaters commonly lack the legal protections accorded to other portions of a river network and are more likely to be significantly altered or completely obliterated by land use.

  16. Small FDIRC Designs and Performances

    CERN Document Server

    Dey, B; Va'vra, J

    2016-01-01

    In this article we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100-200ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. We find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, coupled to cylindrical lens focusing.

  17. Small Cell Network Topology Comparison

    Directory of Open Access Journals (Sweden)

    Jan Oppolzer

    2013-01-01

    Full Text Available One of the essential problems in a mobile network with small cells is that there is only a limited number of (PCIs available. Due to this fact, operators face the inevitable need for reusing (PCIs. In our contribution, we are dealing with a (PCI assignment to FAPs in three different topologies. The first model places FAPs randomly within the network while respecting overlapping defined. The second model places FAPs in a grid without other restrictions. The third model forms a grid as well, although buildings and roads are taken into account and (FAPs are always inside buildings. The proposed models are compared and a conclusion is made based on simulation results.

  18. Conversations between kingdoms: small RNAs.

    Science.gov (United States)

    Weiberg, Arne; Bellinger, Marschal; Jin, Hailing

    2015-04-01

    Humans, animals, and plants are constantly under attack from pathogens and pests, resulting in severe consequences on global human health and crop production. Small RNA (sRNA)-mediated RNA interference (RNAi) is a conserved regulatory mechanism that is involved in almost all eukaryotic cellular processes, including host immunity and pathogen virulence. Recent evidence supports the significant contribution of sRNAs and RNAi to the communication between hosts and some eukaryotic pathogens, pests, parasites, or symbiotic microorganisms. Mobile silencing signals—most likely sRNAs—are capable of translocating from the host to its interacting organism, and vice versa. In this review, we will provide an overview of sRNA communications between different kingdoms, with a primary focus on the advances in plant-pathogen interaction systems.

  19. Immunization against Small Ruminant Lentiviruses

    Directory of Open Access Journals (Sweden)

    Beatriz Amorena

    2013-08-01

    Full Text Available Multisystemic disease caused by Small Ruminant Lentiviruses (SRLV in sheep and goats leads to production losses, to the detriment of animal health and welfare. This, together with the lack of treatments, has triggered interest in exploring different strategies of immunization to control the widely spread SRLV infection and, also, to provide a useful model for HIV vaccines. These strategies involve inactivated whole virus, subunit vaccines, DNA encoding viral proteins in the presence or absence of plasmids encoding immunological adjuvants and naturally or artificially attenuated viruses. In this review, we revisit, comprehensively, the immunization strategies against SRLV and analyze this double edged tool individually, as it may contribute to either controlling or enhancing virus replication and/or disease.

  20. Small Tank Tetraphenylborate Catalyst Studies

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, M.J.

    2001-06-04

    The Salt Disposition Systems Engineering Team identified Small Tank Tetraphenylborate Precipitation (STTP) as an alternative to replace the In-Tank Precipitation Facility at the Savannah River Site. The Department of Energy discontinued operation of the In-Tank Precipitation facility due to the potential for catalytic decomposition of sodium tetraphenylborate. The STTP applies the same process chemistry for removal of cesium from the radioactive wastes but at a controlled lower temperature and in a smaller facility that offers engineering features to mitigate potential for a catalytic reaction. However, additional understanding of the catalytic reaction, through further experimental investigation, is needed to better define the potential for a reaction to occur in the proposed facility.

  1. Episodic tremor triggers small earthquakes

    Science.gov (United States)

    Balcerak, Ernie

    2011-08-01

    It has been suggested that episodic tremor and slip (ETS), the weak shaking not associated with measurable earthquakes, could trigger nearby earthquakes. However, this had not been confirmed until recently. Vidale et al. monitored seismicity in the 4-month period around a 16-day episode of episodic tremor and slip in March 2010 in the Cascadia region. They observed five small earthquakes within the subducting slab during the ETS episode. They found that the timing and locations of earthquakes near the tremor suggest that the tremor and earthquakes are related. Furthermore, they observed that the rate of earthquakes across the area was several times higher within 2 days of tremor activity than at other times, adding to evidence of a connection between tremor and earthquakes. (Geochemistry, Geophysics, Geosystems, doi:10.1029/2011GC003559, 2011)

  2. Small Molecule Fluoride Toxicity Agonists

    Science.gov (United States)

    Nelson1, James W.; Plummer, Mark S.; Blount, Kenneth F.; Ames, Tyler D.; Breaker, Ronald R.

    2015-01-01

    SUMMARY Fluoride is a ubiquitous anion that inhibits a wide variety of metabolic processes. Here we report the identification of a series of compounds that enhance fluoride toxicity in Escherichia coli and Streptococcus mutans. These molecules were isolated by using a high-throughput screen (HTS) for compounds that increase intracellular fluoride levels as determined via a fluoride riboswitch-reporter fusion construct. A series of derivatives were synthesized to examine structure-activity relationships, leading to the identification of compounds with improved activity. Thus, we demonstrate that small molecule fluoride toxicity agonists can be identified by HTS from existing chemical libraries by exploiting a natural fluoride riboswitch. In addition, our findings suggest that some molecules might be further optimized to function as binary antibacterial agents when combined with fluoride. PMID:25910244

  3. Aeration equipment for small depths

    Science.gov (United States)

    Sluše, Jan; Pochylý, František

    2015-05-01

    Deficit of air in water causes complications with cyanobacteria mainly in the summer months. Cyanobacteria is a bacteria that produces poison called cyanotoxin. When the concentration of cyanobacteria increases, the phenomena "algal bloom" appears, which is very toxic and may kill all the organisms. This article describes new equipment for aeration of water in dams, ponds and reservoirs with small depth. This equipment is mobile and it is able to work without any human factor because its control is provided by a GPS module. The main part of this equipment consists of a floating pump which pumps water from the surface. Another important part of this equipment is an aerator where water and air are blended. Final aeration process runs in the nozzles which provide movement of all this equipment and aeration of the water. Simulations of the flow are solved by multiphase flow with diffusion in open source program called OpenFOAM. Results will be verified by an experiment.

  4. Minimum Q Electrically Small Antennas

    DEFF Research Database (Denmark)

    Kim, O. S.

    2012-01-01

    for a multiarm spherical helix antenna confirm the theoretical predictions. For example, a 4-arm spherical helix antenna with a magnetic-coated perfectly electrically conducting core (ka=0.254) exhibits the Q of 0.66 times the Chu lower bound, or 1.25 times the minimum Q.......Theoretically, the minimum radiation quality factor Q of an isolated resonance can be achieved in a spherical electrically small antenna by combining TM1m and TE1m spherical modes, provided that the stored energy in the antenna spherical volume is totally suppressed. Using closed-form expressions...... for the stored energies obtained through the vector spherical wave theory, it is shown that a magnetic-coated metal core reduces the internal stored energy of both TM1m and TE1m modes simultaneously, so that a self-resonant antenna with the Q approaching the fundamental minimum is created. Numerical results...

  5. Small Scale High Speed Turbomachinery

    Science.gov (United States)

    London, Adam P. (Inventor); Droppers, Lloyd J. (Inventor); Lehman, Matthew K. (Inventor); Mehra, Amitav (Inventor)

    2015-01-01

    A small scale, high speed turbomachine is described, as well as a process for manufacturing the turbomachine. The turbomachine is manufactured by diffusion bonding stacked sheets of metal foil, each of which has been pre-formed to correspond to a cross section of the turbomachine structure. The turbomachines include rotating elements as well as static structures. Using this process, turbomachines may be manufactured with rotating elements that have outer diameters of less than four inches in size, and/or blading heights of less than 0.1 inches. The rotating elements of the turbomachines are capable of rotating at speeds in excess of 150 feet per second. In addition, cooling features may be added internally to blading to facilitate cooling in high temperature operations.

  6. Characterization of Small (Energy CT.

    Science.gov (United States)

    Patel, Bhavik N; Bibbey, Alex; Choudhury, Kingshuk R; Leder, Richard A; Nelson, Rendon C; Marin, Daniele

    2017-10-01

    The purpose of this study is to determine whether single-phase contrast-enhanced dual-energy quantitative spectral analysis improves the accuracy of diagnosis of small (energy attenuation measurements. In this retrospective study, 136 consecutive patients (95 men and 41 women; mean age, 54 years) with 144 renal lesions (111 benign and 33 malignant) underwent single-energy unenhanced and dual-energy contrast-enhanced CT of the abdomen. For each renal lesion, attenuation measurements were obtained, and an attenuation change of 15 HU or greater was considered evidence of enhancement. Dual-energy spectral attenuation curves were generated for each lesion. The slope of each curve was measured between 40 and 50 keV (λHU40-50), 40 and 70 keV (λHU40-70), and 40 and 140 keV (λHU40-140). Mean lesion attenuation values and spectral attenuation curve parameters were compared between benign and malignant renal lesions by use of the two-sample t test. Diagnostic accuracy was assessed and validated using cross-validation analysis. With the use of cross-validated optimal thresholds at 100% sensitivity, specificity for differentiating between benign and malignant renal lesions improved significantly when both λHU40-70 and λHU40-140 were used, compared with conventional enhancement measurements (93% [103/111; 95% CI, 86-97%] vs 81% [90/111; 95% CI, 73-88%]) (p = 0.02). The sensitivity of λHU40-70 and λHU40-140 was also higher than that of conventional enhancement measurements, although it was not statistically significant. Single-phase contrast-enhanced dual-energy quantitative spectral analysis significantly improves the specificity for characterization of small (energy attenuation measurements.

  7. Small government or big government?

    Directory of Open Access Journals (Sweden)

    MATEO SPAHO

    2015-03-01

    Full Text Available Since the beginning of the twentieth century, economists and philosophers were polarizedon their positions beyond the role that the government should have in the economy. On one hand John Maynard Keynes represented, within the optics of market economy, a position where the state should intervene in the economy to maintain the aggregate demand and the employment in the country, without hesitation in creating budget deficits and public debt expansion. This approach happens especially in the moments when the domestic economy and global economic trends show a weak growth or a recession. This means a heavy interference inthe economy, with higher income but with high expenditure to GDP too. On the other side, Liberals and Neoliberalsled by Friedrich Hayek advocated a withdrawal of the government from economic activity not just in moments of economic growth but also during the crisis, believing that the market has self-regulating mechanisms within itself. The government, as a result will have a smaller dimension with lower income and also low expenditures compared to the GDP of the country. We took the South-Eastern Europe countries distinguishing those with a "Big Government" or countries with "Small Government". There are analyzed the economic performances during the global crisis (2007-2014. In which countries the public debt grew less? Which country managed to attract more investments and which were the countries that preserved the purchasing power of their consumers? We shall see if during the economic crisis in Eastern Europe the Great Government or the Liberal and "Small" one has been the most successful the model.

  8. Geophysics of Small Planetary Bodies

    Science.gov (United States)

    Asphaug, Erik I.

    1998-01-01

    As a SETI Institute PI from 1996-1998, Erik Asphaug studied impact and tidal physics and other geophysical processes associated with small (low-gravity) planetary bodies. This work included: a numerical impact simulation linking basaltic achondrite meteorites to asteroid 4 Vesta (Asphaug 1997), which laid the groundwork for an ongoing study of Martian meteorite ejection; cratering and catastrophic evolution of small bodies (with implications for their internal structure; Asphaug et al. 1996); genesis of grooved and degraded terrains in response to impact; maturation of regolith (Asphaug et al. 1997a); and the variation of crater outcome with impact angle, speed, and target structure. Research of impacts into porous, layered and prefractured targets (Asphaug et al. 1997b, 1998a) showed how shape, rheology and structure dramatically affects sizes and velocities of ejecta, and the survivability and impact-modification of comets and asteroids (Asphaug et al. 1998a). As an affiliate of the Galileo SSI Team, the PI studied problems related to cratering, tectonics, and regolith evolution, including an estimate of the impactor flux around Jupiter and the effect of impact on local and regional tectonics (Asphaug et al. 1998b). Other research included tidal breakup modeling (Asphaug and Benz 1996; Schenk et al. 1996), which is leading to a general understanding of the role of tides in planetesimal evolution. As a Guest Computational Investigator for NASA's BPCC/ESS supercomputer testbed, helped graft SPH3D onto an existing tree code tuned for the massively parallel Cray T3E (Olson and Asphaug, in preparation), obtaining a factor xIO00 speedup in code execution time (on 512 cpus). Runs which once took months are now completed in hours.

  9. Small Molecule Organic Optoelectronic Devices

    Science.gov (United States)

    Bakken, Nathan

    Organic optoelectronics include a class of devices synthesized from carbon containing 'small molecule' thin films without long range order crystalline or polymer structure. Novel properties such as low modulus and flexibility as well as excellent device performance such as photon emission approaching 100% internal quantum efficiency have accelerated research in this area substantially. While optoelectronic organic light emitting devices have already realized commercial application, challenges to obtain extended lifetime for the high energy visible spectrum and the ability to reproduce natural white light with a simple architecture have limited the value of this technology for some display and lighting applications. In this research, novel materials discovered from a systematic analysis of empirical device data are shown to produce high quality white light through combination of monomer and excimer emission from a single molecule: platinum(II) bis(methyl-imidazolyl)toluene chloride (Pt-17). Illumination quality achieved Commission Internationale de L'Eclairage (CIE) chromaticity coordinates (x = 0.31, y = 0.38) and color rendering index (CRI) > 75. Further optimization of a device containing Pt-17 resulted in a maximum forward viewing power efficiency of 37.8 lm/W on a plain glass substrate. In addition, accelerated aging tests suggest high energy blue emission from a halogen-free cyclometalated platinum complex could demonstrate degradation rates comparable to known stable emitters. Finally, a buckling based metrology is applied to characterize the mechanical properties of small molecule organic thin films towards understanding the deposition kinetics responsible for an elastic modulus that is both temperature and thickness dependent. These results could contribute to the viability of organic electronic technology in potentially flexible display and lighting applications. The results also provide insight to organic film growth kinetics responsible for optical

  10. 75 FR 66411 - Small Entity Compliance Guide: Women-Owned Small Business Program

    Science.gov (United States)

    2010-10-28

    ... ADMINISTRATION Small Entity Compliance Guide: Women-Owned Small Business Program AGENCY: Small Business...) is announcing the availability of a compliance guide for the Women-Owned Small Business (WOSB... final rule amending 13 CFR part 127, entitled ``The Women-Owned Small Business Federal...

  11. 12 CFR 32.7 - Residential real estate loans, small business loans, and small farm loans.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Residential real estate loans, small business... OF THE TREASURY LENDING LIMITS § 32.7 Residential real estate loans, small business loans, and small farm loans. (a) Residential real estate, small business, and small farm loans. (1) In addition to the...

  12. Small Vacuum Energy from Small Equivalence Violation in Scalar Gravity

    CERN Document Server

    Agrawal, Prateek

    2016-01-01

    The theory of scalar gravity proposed by Nordstr\\"{o}m, and refined by Einstein and Fokker, provides a striking analogy to general relativity. In its modern form, scalar gravity appears as the low-energy effective field theory of the spontaneous breaking of conformal symmetry within a CFT, and is AdS/CFT dual to the original Randall-Sundrum I model, but without a UV brane. Scalar gravity faithfully exhibits several qualitative features of the cosmological constant problem of standard gravity coupled to quantum matter, and the Weinberg no-go theorem can be extended to this case as well. Remarkably, a solution to the scalar gravity cosmological constant problem has been proposed, where the key is a very small violation of the scalar equivalence principle, which can be elegantly formulated as a particular type of deformation of the CFT. In the dual AdS picture this involves implementing Goldberger-Wise radion stabilization where the Goldberger-Wise field is a pseudo-Nambu Goldstone boson. In quantum gravity howe...

  13. Chemisorption and Reactions of Small Molecules on Small Gold Particles

    Directory of Open Access Journals (Sweden)

    Geoffrey C. Bond

    2012-02-01

    Full Text Available The activity of supported gold particles for a number of oxidations and hydrogenations starts to increase dramatically as the size falls below ~3 nm. This is accompanied by an increased propensity to chemisorption, especially of oxygen and hydrogen. The explanation for these phenomena has to be sought in kinetic analysis that connects catalytic activity with the strength and extent of chemisorption of the reactants, the latter depending on the electronic structure of the gold atoms constituting the active centre. Examination of the changes to the utilisation of electrons as particle size is decreased points to loss of metallic character at about 3 nm, as energy bands are replaced by levels, and a band gap appears. Detailed consideration of the Arrhenius parameters (E and ln A for CO oxidation points clearly to a step-change in activity at the point where metallic character is lost, as opposed to there being a monotonic dependence of rate on a physical property such as the fraction of atoms at corners or edges of particles. The deplorable scarcity of kinetic information on other reactions makes extension of this analysis difficult, but non-metallic behaviour is an unavoidable property of very small gold particles, and therefore cannot be ignored when seeking to explain their exceptional activity.

  14. Small Proteins Can No Longer Be Ignored

    Science.gov (United States)

    Storz, Gisela; Wolf, Yuri I.; Ramamurthi, Kumaran S.

    2014-01-01

    Small proteins, here defined as proteins of 50 amino acids or less in the absence of processing, have traditionally been overlooked due to challenges in their annotation and biochemical detection. In the past several years however, increasing numbers of small proteins have been identified either through the realization that mutations in “intergenic” regions actually are within unannotated small protein genes, or through the discovery that some small, regulatory RNAs (sRNAs) encode small proteins. These insights together with comparative sequence analysis indicate that tens if not hundreds of small proteins are synthesized in a given organism. This review will summarize what has been learned about the functions of several of these bacterial small proteins, most of which act at the membrane, illustrating the astonishing range of processes in which the small proteins act and pointing to several general conclusions. Important questions for future studies of these overlooked proteins also will be discussed. PMID:24606146

  15. Beam Coupling Impedances of Small Discontinuities

    CERN Document Server

    Kurennoy, S S

    2000-01-01

    A general derivation of the beam coupling impedances produced by small discontinuities on the wall of the vacuum chamber of an accelerator is reviewed. A collection of analytical formulas for the impedances of small obstacles is presented.

  16. Enabling Technology for Small Satellite Launch Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Access to space for Small Satellites is enabled by the use of excess launch capacity on existing launch vehicles. A range of sizes, form factors and masses of small...

  17. How Is Small Intestine Adenocarcinoma Diagnosed?

    Science.gov (United States)

    ... use an endoscope. Instead, the patient swallows a capsule (about the size of a large vitamin pill) that has a light and a very small camera. Like any other pill, the capsule goes through the stomach and into the small ...

  18. Lung cancer - non-small cell

    Science.gov (United States)

    Cancer - lung - non-small cell; Non-small cell lung cancer; NSCLC; Adenocarcinoma - lung; Squamous cell carcinoma - lung ... Smoking causes most cases (around 90%) of lung cancer. The risk depends on the number of cigarettes ...

  19. Small $x$ Phenomenology - Summary and status 2002

    CERN Document Server

    Andersen, J R; Collins, J; Dokshitzer, Y; Görlich, L; Grindhammer, G; Gustafson, G; Jönsson, L B; Jung, H; Kwiecinski, J; Levin, E; Lipatov, A V; Lönnblad, L; Lublinsky, M; Maul, M; Milcewicz, I; Miu, G; Nowak, G; Sjöstrand, Torbjörn; Stasto, A M; Tîmneanu, N; Turnau, J; Zotov, N P

    2003-01-01

    A second workshop on small x physics, within the Small x Collaboration, was held in Lund in June 2002 with the aim of over-viewing recent theoretical progress in this area and summarizing the experimental status.

  20. SMALL MAMMAL USE OF MICROHABITAT REVIEWED

    Science.gov (United States)

    Small mammal microhabitat research has greatly influenced vertebrate community ecologists. There exists a "microhabitat paradigm" that states that sympatry among small mammal species is enabled by differential use of microhabitat (i.e., microhabitat partitioning). However, seve...

  1. 77 FR 46909 - Small Business Innovation Research (SBIR) Program and Small Business Technology Transfer (STTR...

    Science.gov (United States)

    2012-08-06

    ... Innovation Research (SBIR) Program and Small Business Technology Transfer (STTR) Program Policy Directives... Small Business Innovation Research (SBIR) and Small Business Technology Transfer Program (STTR) Policy... technology@sba.gov . SUPPLEMENTARY INFORMATION: I. Background Information SBA is publishing Policy Directives...

  2. Mutual Guarantee Institutions and Small Business Finance

    NARCIS (Netherlands)

    Columba, F.; Gambacorta, L.; Mistrulli, P.E.

    2009-01-01

    A large literature showed that small firms experience difficulties in accessing the credit market due to informational asymmetries; these may be mitigated by collateral or relationship lending, possibilities often precluded to small business. We investigate the effect on small business finance of an

  3. Student Perceptions of Small-Group Learning

    Science.gov (United States)

    Florez, Ida Rose; McCaslin, Mary

    2008-01-01

    Background/Context: Elementary school teachers regularly arrange students in small groups for learning activities. A rich literature discusses various types of small-group learning formats and how those formats affect achievement. Few studies, however, have examined students' perceptions of small-group learning experiences. Our work extends the…

  4. 27 CFR 19.912 - Small plants.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Small plants. 19.912... OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Distilled Spirits For Fuel Use Permits § 19.912 Small plants. Persons wishing to establish a small plant shall apply for a permit as provided in...

  5. 78 FR 77352 - Small Business Policy

    Science.gov (United States)

    2013-12-23

    ... required by Federal law, NASA's general policy for small business programs is described in 48 CFR part 1819... SPACE ADMINISTRATION 14 CFR Part 1204 RIN 2700-AD97 Small Business Policy AGENCY: National Aeronautics... establishes NASA's small business policy and outlines the delegation of authority to implement this policy,...

  6. XP in a Small Software Development Business

    DEFF Research Database (Denmark)

    Babb, Jeffry; Hoda, Rashina; Nørbjerg, Jacob

    2014-01-01

    While small software development shops have trended towards the adoption of Agile methods, local conditions and high iteration pressure typically cause adaptations and appropriations of Agile methods. This paper shares evidence from a study concerning how a small software development company adopts...... most sustainable for small shop teams, with process maintenance and viability as a goal, are highlighted....

  7. Small GTPases : emerging targets in rheumatoid arthritis

    NARCIS (Netherlands)

    Ferreira de Abreu, J.R.

    2009-01-01

    The studies provided in this thesis show that modulation of small GTPase function regulates cellular activation and inflammation in RA and animal models of the disease. Small GTPases are therefore emerging targets in RA and further studies should explore the development of novel small GTPase modulat

  8. New examples of small Polish structures

    OpenAIRE

    Dobrowolski, Jan

    2013-01-01

    We answer some questions from a paper of Krupi\\'nski by giving suitable examples of small Polish structures. First, we present a class of small Polish group structures without generic elements. Next, we construct a first example of a small non-zero-dimensional Polish $G$-group.

  9. Yes, small firms can commercialize photonics

    Science.gov (United States)

    Nelson, Carl W.

    1997-01-01

    Small young companies can commercialize photonics. Many are already doing so and may more are getting started with a small government subsidy from Small Business Innovation Research. Capital is gushing, even begging for good investment opportunities, for companies ready to commit themselves to commercial success.

  10. Mutual Guarantee Institutions and Small Business Finance

    NARCIS (Netherlands)

    Columba, F.; Gambacorta, L.; Mistrulli, P.E.

    2009-01-01

    A large literature showed that small firms experience difficulties in accessing the credit market due to informational asymmetries; these may be mitigated by collateral or relationship lending, possibilities often precluded to small business. We investigate the effect on small business finance of an

  11. [Small fibre neuropathy: knowledge is power].

    NARCIS (Netherlands)

    Hoeijmakers, J.G.; Bakkers, M.; Blom, E.W.; Drenth, J.P.H.; Merkies, I.S.; Faber, C.G.

    2012-01-01

    Small fibre neuropathy is a neuropathy of the small non-myelinated C-fibres and myelinated Adelta-fibres. Clinically, an isolated small fibre neuropathy is distinguished by sensory and autonomic symptoms, with practically no abnormalities on neurological examination other than possible distorted pai

  12. Small is beautiful, and dry

    Institute of Scientific and Technical Information of China (English)

    SHERIDAN; John

    2010-01-01

    Thousands of plant and animal species have been observed to have superhydrophobic surfaces that lead to various novel behaviors. These observations have inspired attempts to create artificial superhydrophobic surfaces, given that such surfaces have multitudinous applications. Superhydrophobicity is an enhanced effect of surface roughness and there are known relationships that correlate surface roughness and superhydrophobicity, based on the underlying physics. However, while these examples demonstrate the level of roughness they tell us little about the independence of this effect in terms of its scale. Thus, they are not capable of explaining why such naturally occurring surfaces commonly have micron-submicron sizes. Here we report on the discovery of a new relation, its physical basis and its experimental verification. The results reveal that scaling-down roughness into the micro-submicron range is a unique and elegant strategy to not only achieve superhydrophobicity but also to increase its stability against environmental disturbances. This new relation takes into account the previously overlooked but key fact that the accumulated line energy arising from the numerous solid-water-air intersections that can be distributed over the apparent contact area, when air packets are trapped at small scales on the surface, can dramatically increase as the roughness scale shrinks. This term can in fact become the dominant contributor to the surface energy and so becomes crucial for accomplishing superhydrophobicity. These findings guide fabrication of stable super water-repellant surfaces.

  13. Small and lightweight power amplifiers

    Science.gov (United States)

    Shams, Qamar A.; Barnes, Kevin N.; Fox, Robert L.; Moses, Robert W.; Bryant, Robert G.; Robinson, Paul C.; Shirvani, Mir

    2002-07-01

    The control of u wanted structural vibration is implicit in most of NASA's programs. Currently several approaches to control vibrations in large, lightweight, deployable structures and twin tail aircraft at high angles of attack are being evaluated. The Air Force has been examining a vertical tail buffet load alleviation system that can be integrated onboard an F/A-18 and flown. Previous wind tunnel and full-scale ground tests using distributed actuators have shown that the concept works; however, there is insufficient rom available onboard an F/A-18 to store current state-of- the-art system components such as amplifiers, DC-to-DC converter and a computer for performing vibration suppression. Sensor processing, power electronics, DC-to-DC converters, and control electronics that may be collocated with distributed actuators, are particularly desirable. Such electronic system would obviate the need for complex, centralized, control processing and power distribution components that will eliminate the weight associated with lengthy wiring and cabling networks. Several small and lightweight power amplifiers ranging from 300V pp to 650V pp have been designed using off the shelf components for different applications. In this paper, the design and testing of these amplifiers will be presented under various electrical loads.

  14. Neurological examination in small animals

    Directory of Open Access Journals (Sweden)

    Viktor Paluš

    2014-03-01

    Full Text Available This clinical review about the neurological examination in small animals describes the basics about the first steps of investigation when dealing with neurological patients. The knowledge of how to perform the neurological examination is important however more important is how to correctly interpret these performed tests. A step-by-step approach is mandatory and examiners should master the order and the style of performing these tests. Neurological conditions can be sometimes very distressing for owners and for pets that might not be the most cooperating. The role of a veterinary surgeon, as a professional, is therefore to collect the most relevant history, to examine a patient in a professional manner and to give to owners an educated opinion about the further treatment and prognosis. However neurological examinations might look challenging for many. But it is only the clinical application of neuroanatomy and neurophysiology to an every-day situation for practicing veterinarians and it does not require any specific in-to-depth knowledge. This clinical review is aimed not only to provide the information on how to perform the neurological examination but it is also aimed to appeal on veterinarians to challenge their daily routine and to start practicing on neurologically normal patients. This is the best and only way to differentiate between the normal and abnormal in a real situation.

  15. Small-bowel permeability in collagenous colitis

    DEFF Research Database (Denmark)

    Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J

    2006-01-01

    Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small-intestinal biopsies......, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal permeability....

  16. Fast Development Of China's Small Satellite Industry

    Institute of Scientific and Technical Information of China (English)

    Sun Hongjin

    2009-01-01

    @@ China Spacesat Co., Ltd of China Academy of Space Technology (CAST) recently said, along with the successful launch of HJ-1A/B for the environment and disaster monitoring and forecasting small satellite constellation and after years of efforts, small satellite development technology has achieved fruitful results, and the development status has been greatly improved.China's small satellite technology has realized a great-leap-forward in development from a single satellite model to series model, from the satellite program to space industry. China has explored a development road for China's small satellite industrialization, and a modern small satellite development base has resulted.

  17. Mastering Microsoft Windows Small Business Server 2008

    CERN Document Server

    Johnson, Steven

    2010-01-01

    A complete, winning approach to the number one small business solution. Do you have 75 or fewer users or devices on your small-business network? Find out how to integrate everything you need for your mini-enterprise with Microsoft's new Windows Server 2008 Small Business Server, a custom collection of server and management technologies designed to help small operations run smoothly without a giant IT department. This comprehensive guide shows you how to master all SBS components as well as handle integration with other Microsoft technologies.: Focuses on Windows Server 2008 Small Business Serv

  18. Fractal aggregates induced by liposome-liposome interaction in the presence of Ca2+.

    Science.gov (United States)

    Sabín, J; Prieto, G; Ruso, J M; Sarmiento, F

    2007-10-01

    We present a study of the fractal dimension of clusters of large unilamellar vesicles (LUVs) formed by egg yolk phosphatidylcholine (EYPC), dimyristoylphosphocholine (DMPC) and dipalmitoylphosphocholine (DPPC) induced by Ca2+ . Fractal dimensions were calculated by application of two methods, measuring the angular dependency of the light scattered by the clusters and following the evolution of the cluster size. In all cases, the fractal dimensions fell in the range from 2.1 to 1.8, corresponding to two regimes: diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA). Whereas DMPC clusters showed a typical transition from the RLCA to the DLCA aggregation, EYPC exhibited an unusual behaviour, since the aggregation was limited for a higher concentration than the critical aggregation concentration. The behaviour of DPPC was intermediate, with a transition from the RLCA to the DLCA regimes with cluster sizes depending on Ca2+ concentration. Studies on the reversibility of the aggregates show that EYPC and DPPC clusters can be re-dispersed by dilution with water. DMPC does not present reversibility. Reversibility is evidence of the existence of secondary minima in the DLVO potential between two liposomes. To predict these secondary minima, a correction of the DLVO model was necessary taking into account a repulsive force of hydration.

  19. Ether- versus ester-linked phospholipid bilayers containing either linear or branched apolar chains.

    Science.gov (United States)

    Balleza, Daniel; Garcia-Arribas, Aritz B; Sot, Jesús; Ruiz-Mirazo, Kepa; Goñi, Félix M

    2014-09-16

    We studied the properties of bilayers formed by ether-and ester-containing phospholipids, whose hydrocarbon chains can be either linear or branched, using sn-1,2 dipalmitoyl, dihexadecyl, diphytanoyl, and diphytanyl phosphatidylcholines (DPPC, DHPC, DPhoPC, and DPhPC, respectively) either pure or in binary mixtures. Differential scanning calorimetry and confocal fluorescence microscopy of giant unilamellar vesicles concurred in showing that equimolar mixtures of linear and branched lipids gave rise to gel/fluid phase coexistence at room temperature. Mixtures containing DHPC evolved in time (0.5 h) from initial reticulated domains to extended solid ones when an equilibrium was achieved. The nanomechanical properties of supported planar bilayers formed by each of the four lipids studied by atomic force microscopy revealed average breakdown forces Fb decreasing in the order DHPC ≥ DPPC > DPhoPC > DPhPC. Moreover, except for DPPC, two different Fb values were found for each lipid. Atomic force microscopy imaging of DHPC was peculiar in showing two coexisting phases of different heights, probably corresponding to an interdigitated gel phase that gradually transformed, over a period of 0.5 h, into a regular tilted gel phase. Permeability to nonelectrolytes showed that linear-chain phospholipids allowed a higher rate of solute + water diffusion than branched-chain phospholipids, yet the former supported a smaller extent of swelling of the corresponding vesicles. Ether or ester bonds appeared to have only a minor effect on permeability.

  20. Small Molecules-Big Data.

    Science.gov (United States)

    Császár, Attila G; Furtenbacher, Tibor; Árendás, Péter

    2016-11-17

    Quantum mechanics builds large-scale graphs (networks): the vertices are the discrete energy levels the quantum system possesses, and the edges are the (quantum-mechanically allowed) transitions. Parts of the complete quantum mechanical networks can be probed experimentally via high-resolution, energy-resolved spectroscopic techniques. The complete rovibronic line list information for a given molecule can only be obtained through sophisticated quantum-chemical computations. Experiments as well as computations yield what we call spectroscopic networks (SN). First-principles SNs of even small, three to five atomic molecules can be huge, qualifying for the big data description. Besides helping to interpret high-resolution spectra, the network-theoretical view offers several ideas for improving the accuracy and robustness of the increasingly important information systems containing line-by-line spectroscopic data. For example, the smallest number of measurements necessary to perform to obtain the complete list of energy levels is given by the minimum-weight spanning tree of the SN and network clustering studies may call attention to "weakest links" of a spectroscopic database. A present-day application of spectroscopic networks is within the MARVEL (Measured Active Rotational-Vibrational Energy Levels) approach, whereby the transitions information on a measured SN is turned into experimental energy levels via a weighted linear least-squares refinement. MARVEL has been used successfully for 15 molecules and allowed to validate most of the transitions measured and come up with energy levels with well-defined and realistic uncertainties. Accurate knowledge of the energy levels with computed transition intensities allows the realistic prediction of spectra under many different circumstances, e.g., for widely different temperatures. Detailed knowledge of the energy level structure of a molecule coming from a MARVEL analysis is important for a considerable number of modeling

  1. Resectable pancreatic small cell carcinoma

    Directory of Open Access Journals (Sweden)

    Jordan M. Winter

    2011-01-01

    Full Text Available Primary pancreatic small cell carcinoma (SCC is rare, with just over 30 cases reported in the literature. Only 7 of these patients underwent surgical resection with a median survival of 6 months. Prognosis of SCC is therefore considered to be poor, and the role of adjuvant therapy is uncertain. Here we report two institutions’ experience with resectable pancreatic SCC. Six patients with pancreatic SCC treated at the Johns Hopkins Hospital (4 patients and the Mayo Clinic (2 patients were identified from prospectively collected pancreatic cancer databases and re-reviewed by pathology. All six patients underwent a pancreaticoduodenectomy. Clinicopathologic data were analyzed, and the literature on pancreatic SCC was reviewed. Median age at diagnosis was 50 years (range 27-60. All six tumors arose in the head of the pancreas. Median tumor size was 3 cm, and all cases had positive lymph nodes except for one patient who only had five nodes sampled. There were no perioperative deaths and three patients had at least one postoperative complication. All six patients received adjuvant therapy, five of whom were given combined modality treatment with radiation, cisplatin, and etoposide. Median survival was 20 months with a range of 9-173 months. The patient who lived for 9 months received chemotherapy only, while the patient who lived for 173 months was given chemoradiation with cisplatin and etoposide and represents the longest reported survival time from pancreatic SCC to date. Pancreatic SCC is an extremely rare form of cancer with a poor prognosis. Patients in this surgical series showed favorable survival rates when compared to prior reports of both resected and unresectable SCC. Cisplatin and etoposide appears to be the preferred chemotherapy regimen, although its efficacy remains uncertain, as does the role of combined modality treatment with radiation.

  2. Large and small photovoltaic powerplants

    Science.gov (United States)

    Cormode, Daniel

    The installed base of photovoltaic power plants in the United States has roughly doubled every 1 to 2 years between 2008 and 2015. The primary economic drivers of this are government mandates for renewable power, falling prices for all PV system components, 3rd party ownership models, and a generous tariff scheme known as net-metering. Other drivers include a desire for decreasing the environmental impact of electricity generation and a desire for some degree of independence from the local electric utility. The result is that in coming years, PV power will move from being a minor niche to a mainstream source of energy. As additional PV power comes online this will create challenges for the electric grid operators. We examine some problems related to large scale adoption of PV power in the United States. We do this by first discussing questions of reliability and efficiency at the PV system level. We measure the output of a fleet of small PV systems installed at Tucson Electric Power, and we characterize the degradation of those PV systems over several years. We develop methods to predict energy output from PV systems and quantify the impact of negatives such as partial shading, inverter inefficiency and malfunction of bypass diodes. Later we characterize the variability from large PV systems, including fleets of geographically diverse utility scale power plants. We also consider the power and energy requirements needed to smooth those systems, both from the perspective of an individual system and as a fleet. Finally we report on experiments from a utility scale PV plus battery hybrid system deployed near Tucson, Arizona where we characterize the ability of this system to produce smoothly ramping power as well as production of ancillary energy services such as frequency response.

  3. Small-bowel permeability in collagenous colitis

    DEFF Research Database (Denmark)

    Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J

    2006-01-01

    OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small-intestin......OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small......-intestinal biopsies, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal...

  4. EFFECT OF MARKET ORIENTATION ON SMALL BUSINESS PERORMANCE IN SMALL TOWN IN MALAYSIA: AN EMPRICAL STUDY ON MALAYSIAN SMALL FIRMS

    Directory of Open Access Journals (Sweden)

    Muhammad Masroor ALAM

    2010-01-01

    Full Text Available Most research on market orientation, and performance was related to big firms. In this study, based on the theoretical framework, a model was developed to investigate the effect of market orientation on business performance in small firms. To test the relationships among the variables, data from 53 small firms in the small town of Chunglun at Sintok, Kedah was used. The findings show that the three components of market orientation are related positive to business performance of small firms. The further analysis also confirmed that customer orientation and competitor orientation are strong predictors of small firm performance. The findings of this study confirm that market orientation behavior also applies to small firms.

  5. Density of very small meteoroids

    Science.gov (United States)

    Kikwaya Eluo, Jean-Baptiste

    2015-08-01

    Knowing the density of meteoroids helps to determine the physical structure and gives insight into the composition of their parent bodies. The density of meteoroids can provide clues to their origins, whether cometary or asteroidal. Density helps also to characterize the risk meteoroids may pose to artificial satellites.Ceplecha (1968) calculated the density of small meteoroids based on a parameter KB (meteoroid beginning height) and classified them in four categories (A,B,C,D) with densities going from 2700 to 180 kgm-3.Babadzhanov(2002) applied a model based on quasi-continuous fragmentation (QCF) on 413 photographic Super-Schmidt meteors by solely fitting their light curves. Their densities range from 400 to 7800 kgm-3. Bellot Rubio et al. (2002) analyzed the same 413 photographic meteors assuming the single body theory based on meteoroid dynamical properties and found densities ranging from 400 to 4800 kgm-3. A thermal erosion model was used by Borovicka et al. (2007) to analyze, simultaneously, the observed decelerations and light curves of six Draconid meteors. The density was found to be 300 kgm-3, consistent with the fact that the Draconid meteors are porous aggregates of grains associated with the Jupiter-family-comet 21P/Giacobini-Zinner (Jacchia, L.G., 1950).We used the Campbell-Brown and Koschny (2004) model of meteoroid ablation to determine the density of faint meteoroids from the analysis of both observed decelerations and light curves of meteoroids (Kikwaya et al., 2009; Kikwaya et al., 2011). Our work was based on a collection of six and ninety-two sporadic meteors. The grain masses used in the modeling ranged from 10-12 Kg to 10-9 Kg. We computed the orbit of each meteoroid and determined its Tisserand parameter. We found that meteoroids with asteroidal orbits have bulk densities ranging from 3000-5000 kgm-3. Meteoroids consistent with HTC/NIC parents have bulk densities from 400 kgm-3 to 1600 kg m-3. JFC meteoroids were found to have surprisingly

  6. Small Modular Reactors: Institutional Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Joseph Perkowski, Ph.D.

    2012-06-01

    ? Objectives include, among others, a description of the basic development status of “small modular reactors” (SMRs) focused primarily on domestic activity; investigation of the domestic market appeal of modular reactors from the viewpoints of both key energy sector customers and also key stakeholders in the financial community; and consideration of how to proceed further with a pro-active "core group" of stakeholders substantially interested in modular nuclear deployment in order to provide the basis to expedite design/construction activity and regulatory approval. ? Information gathering was via available resources, both published and personal communications with key individual stakeholders; published information is limited to that already in public domain (no confidentiality); viewpoints from interviews are incorporated within. Discussions at both government-hosted and private-hosted SMR meetings are reflected herein. INL itself maintains a neutral view on all issues described. Note: as per prior discussion between INL and CAP, individual and highly knowledgeable senior-level stakeholders provided the bulk of insights herein, and the results of those interviews are the main source of the observations of this report. ? Attachment A is the list of individual stakeholders consulted to date, including some who provided significant earlier assessments of SMR institutional feasibility. ? Attachments B, C, and D are included to provide substantial context on the international status of SMR development; they are not intended to be comprehensive and are individualized due to the separate nature of the source materials. Attachment E is a summary of the DOE requirements for winning teams regarding the current SMR solicitation. Attachment F deserves separate consideration due to the relative maturity of the SMART SMR program underway in Korea. Attachment G provides illustrative SMR design features and is intended for background. Attachment H is included for overview

  7. Advantages with small control valves

    Energy Technology Data Exchange (ETDEWEB)

    Nilsson, Gunnar

    2008-09-15

    Between 1995 and 2005, the Swedish District Heating Association carried out several research projects concerning small dimensions on control valves. This lecture aims at giving a summary of these findings which, if they are carried out, have a great impact on the district heating system. The outcome is advantages on both the production side and the customer side. Some of the project's conclusions are as follows: 1. The simulations show that the consequences of temperature disturbances can be reduced when applying smaller control valves, especially at low outdoor temperatures (-5 deg C). 2. The consequences of flow disturbances (pump stop) are not depending on the outdoor temperature (heat demand), but results over the whole year in reduced maximum flow during the process of operation recovery. With adequately reduced valve size, the resulting maximum flow at restart can be approximately reduced to the half, leading in reduced need of pumping peak power. 3. Similarly, the maximum peak power taken from the net at net recovery will be reduced, however, this effect is not as strong as that for flow. 4. Generally, we have found clear indications for that the adjustment of the K{sub vs}-values of control valves in substations should follow a certain logical order of priority. An important factor is the location of substations in respect to the production plant and to the pressure control points in the network. Another important factor is the absolute K{sub vs}-value of the over sizing, i.e. the difference of the actual installed valve and the targeted valve size. 5. Smaller size of control valves means also an improvement of the everyday operation of the district heating net, especially in the case when flow and power peaks are expected to occur. Examples for that could be the morning peaks with increase heat and hot water demands, or such events when the air temperature is decreasing very fast because of weather phenomena. Smaller control valves will smear out the

  8. Zoonotic risks from small ruminants.

    Science.gov (United States)

    Ganter, M

    2015-12-14

    Zoonoses are infections that spread naturally between species (sometimes by a vector) from animals to other animal species or to humans or from humans to animals. Most of the zoonoses diagnosed in sheep and goats are transmitted by close contact of man with these animals and are, more often, occupational diseases that principally affect breeders, veterinarians and/or slaughterhouse workers. Some other diseases have an airborne transmission and affect the population in the vicinity of sheep/goat farms. Due to the fact that small ruminants are almost the only remaining animals which are migrating in industrialised countries, there is a severe risk for transmitting the diseases. Some other zoonotic diseases are foodborne diseases, which are mainly transmitted from animals to humans and to other animal species by contaminated food and water. Within the last decade central Europe was threatened by some new infections, e.g., bluetongue disease and schmallenberg disease, which although not of zoonotic interest, are caused by pathogens transmitted by vectors. Causal agents of both diseases have found highly effective indigenous vectors. In the future, climate change may possibly modify conditions for the vectors and influence their distribution and competence. By this, other vector-borne zoonotic infections may propagate into former disease free countries. Changes in human behaviour in consummation and processing of food, in animal housing and management may also influence future risks for zoonosis. Monitoring, prevention and control measures are proposed to limit further epidemics and to enable the containment of outbreaks. Measures depend mainly on the damage evoked or anticipated by the disease, the local situation, and the epidemiology of the zoonoses, the presence of the infective agent in wild and other animals, as well as the resistance of the causal microorganisms in the environment and the possibility to breed sheep and goats which are resistant to specific

  9. SMALL ENTERPRENEURSHIP IN HOSPITALITY: CROATIAN EXPERIENCES

    Directory of Open Access Journals (Sweden)

    Slobodan Ivanovic

    2013-03-01

    Full Text Available After introductory explanations regarding the selection problems of small enterprises in the Croatian hotel industry, the author provides a number of key indicators of their role in improving the competitiveness of the Croatian hotel industry in the global tourism market. In developed tourism countries, small enterprises have a dominant share in the structure of the hotel industry, and their importance is growing even in the former socialist countries of Europe. Small hotels in Italy accounted for more than 50%, and in Austria with more than 70% of lodging facilities and represent a generator of hotel business in a large number of European tourism countries, and great attention is given to the small enterpreneurs stimulating their growth with different measures of tourist and general economy politics. The author reflects on the Croatian experience of the small businesses in the hospitality through research of development of small family hotels and their importance for the improvement of the supply of the Croatian hotel industry which future is built on personal approach to guests and present trends in the tourism market. States that the role of the National Association of family and small hotels, which represents the specific interests of small hoteliers and enables the continuous improvement of the quality of their offerings, as well as measures to encourage small business development at the macro level. Based on the made analysis the measures of increasing the efficiency of small businesses in the Croatian hospitality are given.

  10. 76 FR 8221 - Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status...

    Science.gov (United States)

    2011-02-11

    ... February 11, 2011 Part VII Small Business Administration 13 CFR Parts 121 and 124 Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status Determinations; Final Rule #0;#0... BUSINESS ADMINISTRATION 13 CFR Parts 121 and 124 RIN 3245-AF53 Small Business Size Regulations; 8(a...

  11. 77 FR 28237 - Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status...

    Science.gov (United States)

    2012-05-14

    ... / Monday, May 14, 2012 / Rules and Regulations#0;#0; ] SMALL BUSINESS ADMINISTRATION 13 CFR Part 124 RIN 3245-AF53 Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status Determinations; Correction AGENCY: U.S. Small Business Administration. ACTION: Correcting...

  12. 75 FR 1296 - Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status...

    Science.gov (United States)

    2010-01-11

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION 13 CFR Parts 121 and 124 Small Business Size Regulations; 8(a) Business Development/Small Disadvantaged Business Status Determinations AGENCY: U.S. Small Business Administration. ACTION: Notice of...

  13. 78 FR 59410 - Small Business Innovation Research and Small Business Technology Transfer Programs...

    Science.gov (United States)

    2013-09-26

    ... ADMINISTRATION Small Business Innovation Research and Small Business Technology Transfer Programs... period for the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR... Street SW., Washington, DC 20416; or send an email to Technology@sba.gov . Highlight the information that...

  14. Success Essentials of Yiwu Small Commodity Market

    OpenAIRE

    Han, Yu

    2013-01-01

    The objective of this thesis was to find the success factors of Yiwu Small Commodity Market. Beside this main objective, the historical reasons of Yiwu Small Commodity Market’s formation also have been analyzed. The purpose was to integrate the historical reasons and internal reasons together to get more comprehensive analysis results of Yiwu market. During the process of research, interviews of five shopkeepers in Yiwu Small Commodity Market were done. The interviews were held in April 2...

  15. Small Package Transportation Companies: An Exploratory Analysis

    OpenAIRE

    Scott Lee WILLIAMS; Nabil RAZZOUK; Victoria SEITZ

    2008-01-01

    Purpose: To determine the evaluative criteria used when choosing small-package transportation companies, the level of importance of selected criteria, and how selected package carriers are perceived by small business decision makers. Methodology: Data were collected via self-administered questionnaires from a total of 31 decision makers in small businesses. The self-administered questionnaire was designed with four sections that handled separate but related topics. Questions from all four sec...

  16. ATLAS- lowering the muon small wheel

    CERN Multimedia

    CERN Audiovisual Service

    2008-01-01

    ATLAS - the two muon small wheels lowered into the cavern Like briefly separated twin sisters, ATLAS’s small wheels were once again united at the experiment’s surface building at Point 1 on St Valentine’s Day. The lowering of the small wheels into the tunnel will mark the end of the installation of detector components for the experiment. At around 15.40 on Friday 29th February the ATLAS collaboration cracked open the champagne as the second of the small wheels was lowered into the cavern.

  17. Small-bowel permeability in collagenous colitis

    DEFF Research Database (Denmark)

    Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J

    2006-01-01

    OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small-intestin......OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small...

  18. Small hepatic veins Budd-Chiari syndrome.

    Science.gov (United States)

    Riggio, Oliviero; Marzano, Chiara; Papa, Alessia; Pasquale, Chiara; Gasperini, Maria Ludovica; Gigante, Antonietta; Valla, Dominique Charles; Plessier, Aurélie; Amoroso, Antonio

    2014-05-01

    Budd-Chiari syndrome is a rare disorder characterized by hepatic venous outflow obstruction at any level from the small hepatic veins to the atrio-caval junction, in the absence of heart failure or constrictive pericarditis. Various imaging modalities are available for investigating the gross hepatic vascular anatomy but there are rare forms of this disease where the obstruction is limited to the small intrahepatic veins, with normal appearance of the large hepatic veins at imaging. In this cases only a liver biopsy can demonstrate the presence of a small vessels outflow block. We report two cases of small hepatic veins Budd-Chiari syndrome.

  19. VTrans Small Culvert Inventory - Access Holes

    Data.gov (United States)

    Vermont Center for Geographic Information — Vermont Agency of Transportation Small Culvert Inventory: Access Holes. This data contains access hole locations along VTrans maintained roadways. The data was...

  20. ATLAS- lowering the muon small wheel

    CERN Multimedia

    2008-01-01

    ATLAS - the two muon small wheels lowered into the cavern Like briefly separated twin sisters, ATLAS’s small wheels were once again united at the experiment’s surface building at Point 1 on St Valentine’s Day. The lowering of the small wheels into the tunnel will mark the end of the installation of detector components for the experiment. At around 15.40 on Friday 29th February the ATLAS collaboration cracked open the champagne as the second of the small wheels was lowered into the cavern.

  1. Small wind planning and building successful installations

    CERN Document Server

    Clark, Nolan

    2013-01-01

    This book provides a cohesive guide to achieving successful small wind installations. It is a comprehensive information resource from one of the world's most experienced small wind professionals, covering all the key issues for small wind system development, from site and machine selection to international standards compliance. Engineers who are tasked with planning and developing these small wind systems, from choosing the best site and accurately estimating likely power output to obtaining proper permitting and troubleshooting operational inefficiencies, will find this book an ess

  2. IMPROVEMENT OF SMALL BUSINESS CREDIT IN RUSSIA

    Directory of Open Access Journals (Sweden)

    Klimova N. V.

    2015-12-01

    Full Text Available Small business is the basis for the development of the national economy, providing 60% of revenues in foreign countries. In Russia, this sector is developing slowly due to lack of funding. In connection with the development of small business, lending is growing in popularity in this sphere. The state develops a variety of programs to support small businesses in the form of public and private lending institutions, venture capital funds, credit unions. However, the volume of lending to small business remains relatively low, due to mistrust of banks and credit organizations in the sphere of small business. Nevertheless, it is here, according to statistics, the debt on loans is only 1.5% of the total. The article describes the features of small business lending, it analyzes the dynamics of the volume of loans granted, and the amount of debt, identifies main obstacles to obtaining loans to entrepreneurs, gives the analysis of credit conditions of small business in Russia and Germany. The problem of credit was considered from two perspectives: from the perspective of credit institutions and the banks themselves. We have developed measures to improve credit conditions, which must take into account not only credit institutions but also the state. It is necessary to provide tax incentives, encouraging the establishment and development of insurance business associations, to support the creation of specialized banks lending to small businesses, the development of cooperation of small and large banks to increase bank lending and reduce credit risks

  3. Site participation in the small community experiment

    Science.gov (United States)

    Holbeck, H. J.; Fellows, M.

    1981-01-01

    The Small Community Solar Thermal Experiment, planned to test a small, developmental solar thermal power plant in a small community application, is assessed. The baseline plan is to install a field of parabolic dishes with distributed generation to provide 1 MWe of experimental power. Participation by the site proposer is an integral element of the experiment; the proposer will provide a ten-acre site, a connection to the electrical distributional system serving the small community, and various services. In addition to the primary participant, site study efforts may be pursued at as many as five alternative sites.

  4. The Innovation Types Evaluation of Small Business

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-jie; TANG Bing-yong; Ronald K. Mitchell; XING Xi-rong

    2002-01-01

    The technology innovation and technology innovation capability plays an important role in management study of small business's growth and development. In this paper, the types of innovation in small business are discussed. Then, a hierarchy comprehensive fuzzy index system evaluating the types of small businesses is proposed. Because of the fuzziness of 15 factors used to analyze the small business, L-R fuzzy number is applied to describe the basic fuzzy state index. Furthermore, the corresponding fuzzy evaluation algorithm is designed. An application example indicated the effects of the methods.

  5. Entrepreneurial Orientation in Small Established Firms

    DEFF Research Database (Denmark)

    Middel, Rick; Lassen, Astrid Heidemann; Laugen, Bjørge Timenes

    2010-01-01

    While research findings have provided important insights on radical innovation for small start-ups and large established organizations, there is still a gap in knowledge on the ability of the well-established small firm to engage in radical innovation. This paper addresses this gap in knowledge...... by discussing how small established firms exhibit entrepreneurial orientation and how does this influence their involvement in development of radical innovation. Through the case studies it became apparent that the small established firms do embody several characteristics which can be associated both......-taking and autonomy plays a very important role, and that the three dimensions are often intertwined....

  6. FACTORS CRISIS OF SMALL BUSINESS DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    A. I. Khorev

    2015-01-01

    Full Text Available Today it became clear that Russia needs not only economic growth, but also economic growth of a certain quality. Re¬gions are not an exception, since they are the most vulnerable to changes in market conditions resource exports. The main economic indicators for larger regions of the country should become entrepreneurs. The main economic indicators for larger regions of the country should become entrepreneurs. Not accidentally retrospective analysis of the evolutionary development of small business shows that the most important role in the economic development of Europe and America have played and continue to play a small business. Results of activity of small businesses are generally positive; the country saw an increase in the main indicators: the number of small enterprises, the average number of employees in small enterprises, turnover of small businesses and investments in fixed assets. The statistics of recent years show a decline of interest in the business population. Number of small businesses created in the last few years there has been a downward trend, while the proportion of surviving for three years after their registration is low. The greatest negative impact on the business affairs of the factors of regulatory and administrative regulation of small business, corruption and bribery of officials and the activities of control and inspection bodies. Addressing these challenges will require proper coordination of regional and local resources in building infrastructure, forming investment mechanisms to support small enterprises, the development of the entrepreneurial potential of the population.

  7. Population cycles in small rodents.

    Science.gov (United States)

    Krebs, C J; Gaines, M S; Keller, B L; Myers, J H; Tamarin, R H

    1973-01-05

    We conclude that population fluctuations in Microtus in southern Indiana are produced by a syndrome of changes in birth and death rates similar to that found in other species of voles and lemmings. The mechanisms which cause the changes in birth and death rates are demolished by fencing the population so that no dispersal can occur. Dispersal thus seems critical for population regulation in Microtus. Because most dispersal occurs during the increase phase of the population cycle and there is little dispersal during the decline phase, dispersal is not directly related to population density. Hence the quality of dispersing animals must be important, and we have found one case of increased dispersal tendency by one genotype. The failure of population regulation of Microtus in enclosed areas requires an explanation by any hypothesis attempting to explain population cycles in small rodents. It might be suggested that the fence changed the predation pressure on the enclosed populations. However, the fence was only 2 feet (0.6 meter) high and did not stop the entrance of foxes, weasels, shrews, or avian predators. A striking feature was that the habitat in the enclosures quickly recovered from complete devastation by the start of the spring growing season. Obviously the habitat and food quality were sufficient to support Microtus populations of abnormally high densities, and recovery of the habitat was sufficiently quick that the introduction of new animals to these enclosed areas resulted in another population explosion. Finally, hypotheses of population regulation by social stress must account for the finding that Microtus can exist at densities several times greater than normal without "stress" taking an obvious toll. We hypothesize that the prevention of dispersal changes the quality of the populations in the enclosures in comparison to those outside the fence. Voles forced to remain in an overcrowded fenced population do not suffer high mortality rates and continue

  8. Small Group Multitasking in Literature Classes

    Science.gov (United States)

    Baurain, Bradley

    2007-01-01

    Faced with the challenge of teaching American literature to large, multilevel classes in Vietnam, the writer developed a flexible small group framework called "multitasking". "Multitasking" sets up stable task categories which rotate among small groups from lesson to lesson. This framework enabled students to work cooperatively in a variety of…

  9. Morphometric Characterization of Small Cell Lymphocytic Lymphoma

    Directory of Open Access Journals (Sweden)

    Chisoi Anca

    2014-11-01

    Full Text Available The morphometry in histopathology is used to characterize cell populations belonging to different tissues and to identify differences in their parameters with prognostic implications. To achieve morphometric examination were selected 6 of 24 cases identified as small cell lymphocytic lymphoma. For each case analysis was done on five fields, for each field measuring the parameters of 20 cells. The studied parameters were for cytoplasm: cytoplasmic area, maximum and minimum cytoplasmic diameter, cytoplasmic perimeter; for nucleus were measured: nuclear area, minimum and maximum nuclear diameter, nuclear perimeter, nuclear contour index, nuclear ellipticity index, nuclear irregularity index. Also the nucleocytoplasmic ratio was calculated in all studied cases. Small cell lymphocytic lymphoma is characterized in morphometric terms having a small cytoplasmic area (average 29.206 and also a small nuclear area (mean 28.939 having a nucleo-cytoplasmic ratio appearance suggestive for adult lymphocyte. A nuclear contour index small value (3.946, ellipticity index value also small (3.521 and small nuclear irregularity index (3.965. Standard deviations, in any of the studied morphometric categories, is around or below 1 suggesting monomorphic cell appearance. These morphometric and microscopic features characterized mainly by a small population of adult lymphocytes, monomorphic, with rounded hipercromic nuclei, dense chromatin, support the framing into indolent lymphoma group in terms of clinical outcome.

  10. Exploring Small Animal Care. Teacher's Guide.

    Science.gov (United States)

    Livesey, Dennis W.

    This course guide in small animal care is designed to give students seeking employment in veterinary hospitals, kennels, or pet shops an opportunity to (1) develop basic skills in small animal handling, sanitation of housing, and nutrition, (2) acquire skills in dog and cat grooming, including shop operation, (3) develop attitudes which contribute…

  11. Multi-User MIMO Across Small Cells

    DEFF Research Database (Denmark)

    Finn, Danny; Ahmadi, Hamed; Cattoni, Andrea Fabio

    2014-01-01

    The main contribution of this work is the proposal and assessment of the MU-MIMO across Small Cells concept. MU-MIMO is the spatial multiplexing of multiple users on a single time-frequency resource. In small cell networks, where the number of users per cell is low, finding suitable sets of users...

  12. A High-performance Small Signal Amplifier

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    According to questions in the design of high quality small signal amplifier, this paper gave a new-type high performance small signal amplifier. The paper selected the operational amplifier of ICL Company and designed a new-type circuit with simple, low cost and excellent performance.

  13. "small ACCELERATORS" 24 May - 2 June 2005

    CERN Multimedia

    2005-01-01

    CERN Accelerator School and Kernfysisch Versneller Instituut (KVI) Groningen, the Netherlands announce a course on "Small Accelerators", Hotel Golden Tulip Drenthe, Zeegse, the Netherlands, 24 May - 2 June 2005. This specialised course is dedicated to the physics and the main applications of small accelerators. The course will review the different accelerator types as well as their specificities in terms of accelerator physics.

  14. 14 CFR 252.13 - Small aircraft.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Small aircraft. 252.13 Section 252.13 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS SMOKING ABOARD AIRCRAFT § 252.13 Small aircraft. Air carriers shall prohibit smoking on aircraft...

  15. Governance of ecosystem services on small islands

    NARCIS (Netherlands)

    Polman, Nico; Reinhard, Stijn; Bets, van L.K.J.; Kuhlman, Tom

    2016-01-01

    Natural ecosystems provide an attractive focus for tourism on small islands. However, at the same time tourism and other human actions can be detrimental to these ecosystems especially because governance of the ecosystem may be difficult due to the limited resilience of small island ecosystems. I

  16. The Small Book Press: A Cultural Essential.

    Science.gov (United States)

    Henderson, Bill

    1984-01-01

    Discussion of small literary book publishers notes works of small-press authors (Thomas Paine, Washington Irving, Walt Whitman, Mark Twain, Upton Sinclair, Anais Nin); today's outstanding presses (Creative Arts Book Company, Persea Books, Full Court Press, Reed and Cannon Company, Tuumba Books); and role of little magazines. Thirty-seven…

  17. Problems of marketing in small innovative enterprises.

    OpenAIRE

    Sidorchuk, Roman

    2011-01-01

    Article is devoted to the continuation of the study hypotheses on the relationship between marketing and life cycle of a small business. Some results of studies of small innovative companies in the Russian Federation: Moscow and St. Petersburg, Moscow, Novgorod, Novosibirsk, Sverdlovsk, Tomsk, Chelyabinsk Region and the Krasnodar Territory. Some results of the analysis, showing the feature in the marketing of innovative enterprises.

  18. Small Group Multitasking in Literature Classes

    Science.gov (United States)

    Baurain, Bradley

    2007-01-01

    Faced with the challenge of teaching American literature to large, multilevel classes in Vietnam, the writer developed a flexible small group framework called "multitasking". "Multitasking" sets up stable task categories which rotate among small groups from lesson to lesson. This framework enabled students to work cooperatively…

  19. Radiation Hardness Assurance (RHA) for Small Missions

    Science.gov (United States)

    Campola, Michael J.

    2016-01-01

    Varied mission life and complexity is growing for small spacecraft. Small missions benefit from detailed hazard definition and evaluation as done in the past. Requirements need to flow from the system down to the parts level and aid system level radiation tolerance. RHA is highlighted with increasing COTS usage.

  20. Small Molecules in the Cone Snail Arsenal.

    Science.gov (United States)

    Neves, Jorge L B; Lin, Zhenjian; Imperial, Julita S; Antunes, Agostinho; Vasconcelos, Vitor; Olivera, Baldomero M; Schmidt, Eric W

    2015-10-16

    Cone snails are renowned for producing peptide-based venom, containing conopeptides and conotoxins, to capture their prey. A novel small-molecule guanine derivative with unprecedented features, genuanine, was isolated from the venom of two cone snail species. Genuanine causes paralysis in mice, indicating that small molecules and not just polypeptides may contribute to the activity of cone snail venom.

  1. Small cell undifferentiated carcinoma in the epididymis

    Institute of Scientific and Technical Information of China (English)

    CHEN Jia-wei; YUAN Lin; Hu Hong-hui

    2005-01-01

    @@ Small cell undifferentiated carcinoma is a special type of tumor which is usually found in the lungs. However, it is very rare in extra pulmonary tissues, especially in epididymis. One case of small cell undifferentiated carcinoma in the right epididymis, with partial differentiation to adenocarcinoma and neuroendocrine carcinoma is reported as follows.

  2. Analyst Information Precision and Small Earnings Surprises

    NARCIS (Netherlands)

    S. Bissessur; D. Veenman

    2014-01-01

    Prior research attributes zero and small positive earnings surprises to managers’ incentives for earnings management. In contrast, this study introduces and empirically tests an explanation for zero and small positive earnings surprises based on predictable variation in analyst forecast errors. We a

  3. E-Learning in Small Organisations

    Science.gov (United States)

    Sambrook, Sally

    2003-01-01

    This paper focuses on the existing and potential role of electronic learning in small and medium-sized organisations (SMEs). Innovations in information and communication technologies (ICTs) could create new forms of learning, particularly appealing to small organisations, to overcome traditional barriers such as lack of financial resources, time,…

  4. Small Drinking Water Systems Research and Development

    Science.gov (United States)

    In the United States, there are 152,002 public water systems (PWS) in operation. Of these, 97% are considered small systems under the Safe Drinking Water Act (SDWA)—meaning they serve 10,000 or fewer people. While many of these small systems consistently provide safe, relia...

  5. Small Hydropower in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Hadjerioua, Boualem [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Kurt [Telluride Energy, Telluride, CO (United States)

    2015-09-01

    Small hydropower, defined in this report as hydropower with a generating capacity of up to 10 MW typically built using existing dams, pipelines, and canals has substantial opportunity for growth. Existing small hydropower comprises about 75% of the current US hydropower fleet in terms of number of plants. The economic feasibility of developing new small hydropower projects has substantially improved recently, making small hydropower the type of new hydropower development most likely to occur. In 2013, Congress unanimously approved changes to simplify federal permitting requirements for small hydropower, lowering costs and reducing the amount of time required to receive federal approvals. In 2014, Congress funded a new federal incentive payment program for hydropower, currently worth approximately 1.5 cents/kWh. Federal and state grant and loan programs for small hydropower are becoming available. Pending changes in federal climate policy could benefit all renewable energy sources, including small hydropower. Notwithstanding remaining barriers, development of new small hydropower is expected to accelerate in response to recent policy changes.

  6. Hate Speech on Small College Campuses.

    Science.gov (United States)

    Hemmer, Joseph J., Jr.

    A study identified and evaluated the approach of small colleges in dealing with hate speech and/or verbal harassment incidents. A questionnaire was sent to the Dean of Students at 200 randomly-selected small (500-2000 students), private, liberal arts colleges and universities. Responses were received from 132 institutions, for a response rate of…

  7. Legalising small coal mines in Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa Bula, D.

    2000-07-01

    It was estimated that in 1996 some 97% of the coal mines in Colombia comprised small-scale operations. This paper discusses the legal framework of the Colombian mining sector, the regulatory framework of small-scale mining, the illegal mining issue, and the Colombian approach to illegal coal mining. 1 fig., 13 tabs.

  8. Small Business Administration Semiannual Regulatory Agenda

    Science.gov (United States)

    2010-12-20

    ... address teams and joint ventures of small businesses and the requirement that each federal agency must... for teaming and joint ventures involving small businesses. Timetable: Action Date FR Cite NPRM 01/00... (NAICS) Sector 72, Accommodation and Food Services -- namely NAICS 721110, Hotels and Motels, from $7.0...

  9. Epidemics in interconnected small-world networks

    NARCIS (Netherlands)

    Liu, M.; Li, D.; Qin, P.; Liu, C.; Wang, H.; Wang, F.

    2015-01-01

    Networks can be used to describe the interconnections among individuals, which play an important role in the spread of disease. Although the small-world effect has been found to have a significant impact on epidemics in single networks, the small-world effect on epidemics in interconnected networks

  10. Astrophysics with small satellites in Scandinavia

    DEFF Research Database (Denmark)

    Lund, Niels

    2003-01-01

    The small-satellites activities in the Scandinavian countries are briefly surveyed with emphasis on astrophysics research. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.......The small-satellites activities in the Scandinavian countries are briefly surveyed with emphasis on astrophysics research. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved....

  11. Insights from Small-"N" Studies

    Science.gov (United States)

    Gouvea, Julia

    2017-01-01

    Small-"N" studies have been relatively uncommon in biology education research and are likely less familiar to instructors and administrators than large-"N" studies. Nevertheless, many scholars in the social sciences have argued for the value of small-"N" studies in informing research and practice (e.g., Flyvbjerg…

  12. Clinical radiology of the small intestine

    Energy Technology Data Exchange (ETDEWEB)

    Herlinger, H.; Maglinte, D.

    1989-01-01

    This book discussed embryology, anatomy, physiology, and immunology of the small intestine. Radiographic procedures in the small intestine especially enterolysis are presented. Focus is on the role of other types of imaging techniques including sonography, computed tomography, radionuclide imaging, angiography, biopsy, and enteroscopy.

  13. Allosteric small-molecule kinase inhibitors

    DEFF Research Database (Denmark)

    Wu, Peng; Clausen, Mads Hartvig; Nielsen, Thomas E.

    2015-01-01

    current barriers of kinase inhibitors, including poor selectivity and emergence of drug resistance. In spite of the small number of identified allosteric inhibitors in comparison with that of inhibitors targeting the ATP pocket, encouraging results, such as the FDA-approval of the first small...

  14. XP in a Small Software Development Business

    DEFF Research Database (Denmark)

    Babb, Jeffry; Hoda, Rashina; Nørbjerg, Jacob

    2014-01-01

    While small software development shops have trended towards the adoption of Agile methods, local conditions and high iteration pressure typically cause adaptations and appropriations of Agile methods. This paper shares evidence from a study concerning how a small software development company adopts...

  15. Gestures: Silent Scaffolding within Small Groups

    Science.gov (United States)

    Carter, Glenda; Wiebe, Eric N.; Reid-Griffin, Angela

    2006-01-01

    This paper describes how gestures are used to enhance scaffolding that occurs in small group settings. Sixth and eighth grade students participated in an elective science course focused on earth science concepts with a substantial spatial visualization component. Gestures that students used in small group discussions were analyzed and four…

  16. Gravity Compensation Technique Uses Small dc Motor

    Science.gov (United States)

    Hollow, Richard

    1988-01-01

    Small dc servomotor powered by simple constant-current source and with suitable gearing used to cancel effect of gravity upon load. Lead-screw positioning system has load counterbalanced by small supplementary motor powered by constant current source. Motor lighter and more compact alternative to counterbalance. Used in variety of mechanical systems where load positioned or accelerated in vertical plane.

  17. Environmental Education and Small Business Environmental Activity

    Science.gov (United States)

    Redmond, Janice; Walker, Beth

    2011-01-01

    Environmental education is seen as a key driver of small business environmental management, yet little is known about the activities small business owner-managers are undertaking to reduce their environmental impact or in what areas they may need education. Therefore, research that can identify environmental management activities being undertaken…

  18. Rural and Small Town School Counselors.

    Science.gov (United States)

    Pearson, Richard E.; Sutton, John M., Jr.

    1999-01-01

    Group discussions and interviews with counselors in small and rural schools in Maine and upstate New York focused on the advantages and disadvantages of working in small schools, role generalization and confusion experienced by school counselors, professional autonomy and accountability, and the need for relevant inservice training. (Contains 33…

  19. 75 FR 29393 - Small Business Week, 2010

    Science.gov (United States)

    2010-05-26

    ... heart of the American dream. They are the backbone of our Nation's economy, they employ tens of millions... small businesses drive our economy toward recovery and long- term growth. The American Recovery and... a proud reflection of our character. A healthy small business sector will give us vibrant...

  20. Arteriovenous Malformation Detected by Small Bowel Endoscopy

    Directory of Open Access Journals (Sweden)

    Takaaki Fujii

    2014-10-01

    Full Text Available Gastrointestinal bleeding that originates in the small intestine is often difficult to diagnose. When successful diagnosis reveals a lesion that can be localized preoperatively, the laparoscopic approach is an appropriate and beneficial treatment modality for small bowel resection. A 69-year-old man presented with a 6-month history of gastrointestinal bleeding and symptomatic transfusion-dependent anemia. Upper and lower endoscopy were normal. Double-balloon endoscopy established the source of the bleeding as a 0.5-cm polypoid mass appearing as a submucosal tumor with redness and pulsation in the lower ileum, suggesting a vascular lesion. Laparoscopic small bowel resection was successful in removing the mass in the ileum. Histological evaluation of the mass revealed an arteriovenous malformation. Preoperative small bowel endoscopy can be useful for diagnosing the cause and localization of arteriovenous malformation in the small intestine.

  1. Research progress of cerebral small vessel disease

    Directory of Open Access Journals (Sweden)

    Jun-dong JIA

    2015-03-01

    Full Text Available Cerebral small vessel disease refers to a group of pathological processes with various etiologies that affect small arteries, arterioles, venules, and capillaries of the brain. Recently, the researches of cerebral small vessel disease have got initial progressions, and a definite diagnosis of this disease is comfirmed by biopsy. Given the pathological material is difficult to obtain, clinicians should pay more attention to the imaging features and clinical manifestations. Correct understanding of imaging and clinical manifestations contributes to the early identification of cerebral small vessel disease. Herein, an overview is provided on the present status, common imaging features, pathogenesis, clinical manifestations and treatment of cerebral small vessel disease. DOI: 10.3969/j.issn.1672-6731.2015.02.003

  2. Generically large nongaussianity in small multifield inflation

    Energy Technology Data Exchange (ETDEWEB)

    Bramante, Joseph [Department of Physics, University of Notre Dame,Notre Dame, IN, 46556 (United States)

    2015-07-07

    If forthcoming measurements of cosmic photon polarization restrict the primordial tensor-to-scalar ratio to r<0.01, small field inflation will be a principal candidate for the origin of the universe. Here we show that small multifield inflation, without the hybrid mechanism, typically results in large squeezed nongaussianity. Small multifield potentials contain multiple flat field directions, often identified with the gauge invariant field directions in supersymmetric potentials. We find that unless these field directions have equal slopes, large nongaussianity arises. After identifying relevant differences between large and small two-field potentials, we demonstrate that the latter naturally fulfill the Byrnes-Choi-Hall large nongaussianity conditions. Computations of the primordial power spectrum, spectral index, and squeezed bispectrum, reveal that small two-field models which otherwise match observed primordial perturbations, produce excludably large nongaussianity if the inflatons’ field directions have unequal slopes.

  3. Small-x phenomenology - Summary of the 3rd Lund small-x workshop in 2004

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, J.R. [University of Cambridge, Cavendish Laboratory, Cambridge (United Kingdom); Baranov, S. [Lebedev Institute of Physics, Moscow (Russian Federation); Bartels, J.; Chachamis, G.; Kutak, K. [Hamburg University, Hamburg (Germany); Barnafoldi, G.G.; Levai, P. [KFKI RMKI, Budapest (Hungary); Collins, J. [Penn State Univ., 104 Davey Lab., University Park, PA (United States); Grindhammer, G. [Max Planck Institut, Munich (Germany); Gustafson, G.; Loennblad, L.; Sjoedahl, M. [Lund University, Department of Theoretical Physics, Lund (Sweden); Hansson, M.; Joensson, L.; Knutsson, A. [Lund University, Department of Physics, Lund (Sweden); Ingelman, G. [University of Uppsala, Uppsala (Sweden); Jung, H.; Kowalski, H.; Risler, C. [DESY, Hamburg (Germany); Kyrieleis, A. [University of Manchester, Manchester (United Kingdom); Lipatov, A.; Zotov, N. [Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Lublinsky, M. [University of Connecticut, Storrs (United States); Marchesini, G. [University of Milan-Bicocca and INFN, Sezione di Milano-Bicocca, Milano (Italy); Milcewicz, I.; Turnau, J. [H. Niewodniczanski Institute of Nuclear Physics, Cracow (Poland); Sabio-Vera, A. [CERN, Geneva (Switzerland); Stasto, A. [Brookhaven National Lab., Physics Department, Upton, NY (United States); Watt, G. [IPPP, Durham (United Kingdom)]|[DESY, Hamburg (Germany)

    2006-10-15

    A third workshop on small-x physics, within the Small-x Collaboration, was held in Hamburg in May 2004 with the aim of overviewing recent theoretical progress in this area and summarizing the experimental status. (orig.)

  4. The Ethical Dilemma in Globalizing Small Businesses

    Directory of Open Access Journals (Sweden)

    Jacob C. Nganga

    2014-09-01

    Full Text Available This paper is largely a theoretical exposition of ethical challenges that stifle the participation of smallbusinesses in the global value chains with particular reference to businesses in developing countries. Smallbusinessclusters in developing economies, remain locked in low-quality products and low-income markets.With little innovation, small business lack capacity to produce goods that can attract foreign demand. Yet,small enterprises must provide productive employment for an increasing number of job-seekers in thesecountries. Innovation growth in small enterprises is normally limited to apprenticeship process and as such,results in a dead-end to progress of indigenous technology. To promote creation and growth of small business,efforts are required to put the small business clusters in a global value chain as this enhances possibilities ofnew market avenues and as well as benching market indigenous innovative efforts to international standards.Exposure of small business to global market also encourages networks formations which are conduits of skillsfor quality improvement and valuation of products from the sector. However, the quest for improving theparticipation and market share of small business is faced with challenges that stem from the way the process ofglobalization has taken place over time. To overcome these globalization challenges, policy makers mustcontend with ethical issues that require to be addressed through consultative efforts at international arena.

  5. Collaborative Manufacturing for Small-Medium Enterprises

    Science.gov (United States)

    Irianto, D.

    2016-02-01

    Manufacturing systems involve decisions concerning production processes, capacity, planning, and control. In a MTO manufacturing systems, strategic decisions concerning fulfilment of customer requirement, manufacturing cost, and due date of delivery are the most important. In order to accelerate the decision making process, research on decision making structure when receiving order and sequencing activities under limited capacity is required. An effective decision making process is typically required by small-medium components and tools maker as supporting industries to large industries. On one side, metal small-medium enterprises are expected to produce parts, components or tools (i.e. jigs, fixture, mold, and dies) with high precision, low cost, and exact delivery time. On the other side, a metal small- medium enterprise may have weak bargaining position due to aspects such as low production capacity, limited budget for material procurement, and limited high precision machine and equipment. Instead of receiving order exclusively, a small-medium enterprise can collaborate with other small-medium enterprise in order to fulfill requirements high quality, low manufacturing cost, and just in time delivery. Small-medium enterprises can share their best capabilities to form effective supporting industries. Independent body such as community service at university can take a role as a collaboration manager. The Laboratory of Production Systems at Bandung Institute of Technology has implemented shared manufacturing systems for small-medium enterprise collaboration.

  6. Optimisation of Investment Resources at Small Enterprises

    Directory of Open Access Journals (Sweden)

    Shvets Iryna B.

    2014-03-01

    Full Text Available The goal of the article lies in the study of the process of optimisation of the structure of investment resources, development of criteria and stages of optimisation of volumes of investment resources for small enterprises by types of economic activity. The article characterises the process of transformation of investment resources into assets and liabilities of the balances of small enterprises and conducts calculation of the structure of sources of formation of investment resources in Ukraine at small enterprises by types of economic activity in 2011. On the basis of the conducted analysis of the structure of investment resources of small enterprises the article forms main groups of criteria of optimisation in the context of individual small enterprises by types of economic activity. The article offers an algorithm and step-by-step scheme of optimisation of investment resources at small enterprises in the form of a multi-stage process of management of investment resources in the context of increase of their mobility and rate of transformation of existing resources into investments. The prospect of further studies in this direction is development of a structural and logic scheme of optimisation of volumes of investment resources at small enterprises.

  7. Influence of the interdigitated gel phase in mixtures of ether-linked and monofluorinated ester-linked phospholipids.

    Science.gov (United States)

    Smith, Eric A; Dea, Phoebe K

    2012-12-01

    To evaluate the influence of the hydrocarbon chain linkage on the thermodynamic phase behavior of spontaneously interdigitating lipids, mixtures of ether-linked 1,2-di-O-hexadecyl-phosphocholine (DHPC) and ester-linked 1-palmitoyl-2-[16-fluoropalmitoyl]sn-glycero-3-phosphocholine (F-DPPC) were studied. A combination of differential scanning calorimetry (DSC), fluorescence spectroscopy, and transmittance spectrophotometry was used. Small amounts of F-DPPC increase the pretransition temperature (T(p)) between the interdigitated gel phase (L(β)I) and the ripple gel phase (P(β)'). There are some signs of immiscibility where the non-interdigitated lipid is present in the phase diagram. However, at around 20mol.% F-DPPC, the pretransition merges with the main transition and is no longer detectable as a separate entity. Additionally, the T(m) hysteresis increases steadily with higher mole fractions of F-DPPC. These results support that incorporating F-DPPC progressively stabilizes the L(β)I phase of DHPC until the membrane is fully interdigitated below the main transition temperature (T(m)). The mixtures of F-DPPC and DHPC are miscible once the membrane is entirely interdigitated in the gel phase. Therefore, the ability of both lipids to interdigitate is an important factor controlling gel phase miscibility. Our results also demonstrate that the gel phase behavior of DHPC is highly sensitive to changes in its environment.

  8. 47 CFR 101.1107 - Bidding credits for very small businesses, small businesses and entrepreneurs.

    Science.gov (United States)

    2010-10-01

    ..., small businesses and entrepreneurs. 101.1107 Section 101.1107 Telecommunication FEDERAL COMMUNICATIONS... Procedures for LMDS § 101.1107 Bidding credits for very small businesses, small businesses and entrepreneurs.... (c) A winning bidder that qualifies as an entrepreneur, as defined in § 101.1112, or a consortium...

  9. Thinking Big about Getting Small: An Ideological Genealogy of Small-School Reform

    Science.gov (United States)

    Kafka, Judith

    2008-01-01

    Background: Support for small schools, and specifically for the creation of small, autonomous schools of choice, has grown considerably in the past decade--particularly in the context of urban schooling. Funded by private and public monies, small-school initiatives have been implemented in most of the nation's city school districts and have become…

  10. Great governance in small societies : Effective public sector practices in small-scale democracies

    NARCIS (Netherlands)

    Douglas, Scott

    2011-01-01

    Every government faces its own particular challenges. For a small-scale democracy, the size of its society might be the obvious limitation. Most discussion about small societies thus focuses on the governance failures caused by this small size. This book argues that it would be more useful to explor

  11. FINANCIAL MECHANISM OF SMALL ENTERPRISES STABILITY

    Directory of Open Access Journals (Sweden)

    G.M. Zaloznaya

    2007-03-01

    Full Text Available Rates of growth of parameters of development and role of small enterprises in economy of Russia and its regions today it is much less, than in the developed countries of the world. The significant role in the decision of this problem belongs to the financial mechanism. The complex changes of financial attitudes directed on increase of efficiency of functioning of the enterprises of small business are necessary. In this connection experience of the Orenburg area on formation of system of support of small business is reasonably interesting, and also its involving in development of real sector of economy and the decision of social questions of region.

  12. Small cell carcinoma of the appendix

    Directory of Open Access Journals (Sweden)

    Carey Declan P

    2008-01-01

    Full Text Available Abstract Background An extrapulmonary small cell carcinoma is a rare condition. It has similar histological features to pulmonary small cell carcinoma and is equally aggressive. Case presentation We present the case of a 60-year-old woman who presented with right upper quadrant pain. Computerised tomography revealed an appendiceal lesion and multiple liver metastases. Exploratory laparotomy and right hemicolectomy was performed with histopathological analysis confirming a primary small cell carcinoma of her appendix. Conclusion This is the first reported case of a pure extrapulmonary carcinoma arising from the appendix.

  13. Estimation of Poverty in Small Areas

    Directory of Open Access Journals (Sweden)

    Agne Bikauskaite

    2014-12-01

    Full Text Available A qualitative techniques of poverty estimation is needed to better implement, monitor and determine national areas where support is most required. The problem of small area estimation (SAE is the production of reliable estimates in areas with small samples. The precision of estimates in strata deteriorates (i.e. the precision decreases when the standard deviation increases, if the sample size is smaller. In these cases traditional direct estimators may be not precise and therefore pointless. Currently there are many indirect methods for SAE. The purpose of this paper is to analyze several diff erent types of techniques which produce small area estimates of poverty.

  14. Small scale smugglers in Tamaulipas, Mexico

    OpenAIRE

    Simón Pedro Izcara Palacios

    2013-01-01

    Small-scale part-time smugglers are embedded in the migrant community itself. They work in the United States for several months before returning to their place of origin to organize, with the help of several assistants, a small group of migrants, who are transported where the coyotes themselves are going. This article analyses small-scale smuggling carried out by Tamaulipas' polleros, who transport to the United States, one or a few times per year, migrants from their hometowns or other neigh...

  15. Treatment Option Overview (Small Intestine Cancer)

    Science.gov (United States)

    ... intestine . The digestive system removes and processes nutrients ( vitamins , minerals , carbohydrates , fats, proteins , and water) from foods ... a microscope to see whether they contain cancer. Bypass : Surgery to allow food in the small intestine ...

  16. General Information about Small Intestine Cancer

    Science.gov (United States)

    ... intestine . The digestive system removes and processes nutrients ( vitamins , minerals , carbohydrates , fats, proteins , and water) from foods ... a microscope to see whether they contain cancer. Bypass : Surgery to allow food in the small intestine ...

  17. High Tc superconducting small loop antenna

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.; Mehler, M.J.; Maclean, T.S.M.; Lancaster, M.J.; Gough, C.E. (Univ. of Birmingham (UK)); Alford, N. (I.C.I. Advanced Materials Div., Runcorn (UK))

    1989-12-01

    The improvement in the radiation efficiency of an electrically small loop antenna is analysed when it is fabricated from a superconductor, and experimental results for a liquid nitrogen cooled, ceramic superconducting loop at 450MHz are presented. (orig.).

  18. Micro Resistojet for Small Satellites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Micro-resistojets offer the best combination of simplicity, performance, wet system mass and power consumption for small satellites (<100kg, <50Watts)...

  19. Biomass for energy - small scale technologies

    Energy Technology Data Exchange (ETDEWEB)

    Salvesen, F.; Joergensen, P.F. [KanEnergi, Rud (Norway)

    1997-12-31

    The bioenergy markets and potential in EU region, the different types of biofuels, the energy technology, and the relevant applications of these for small-scale energy production are reviewed in this presentation

  20. Antimicrobial stewardship in small animal veterinary practice

    DEFF Research Database (Denmark)

    Guardabassi, Luca; Prescott, John F

    2015-01-01

    Despite the increasing recognition of the critical role for antimicrobial stewardship in preventing the spread of multidrug-resistant bacteria, examples of effective antimicrobial stewardship programs are rare in small animal veterinary practice. This article highlights the basic requirements...