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961.
Multimeric lactosides based on carbohydrate scaffolds with valencies ranging from 1 to 4 and different linker lengths were synthesized by a copper‐catalyzed azide–alkyne cycloaddition (CuAAC). The binding affinities and crosslinking abilities of the new “click clusters” toward biologically relevant galectins (gal‐1, gal‐3) and peanut lectin were evaluated by fluorescent polarization assay (FPA) and enzyme‐linked lectin assay (ELLA), respectively. FPA indicated that the binding affinities of the synthetic multilactosides towards the galectins increased proportionally with their lactosyl content, without significant differences due to the spacer length. ELLA evidenced a modest cluster effect for the multivalent conjugates, with a relative potency per lactoside ranging from 2.1 to 3.2. Nearly identical binding affinities were recorded for derivatives differing in the length of the linkers, in agreement with the FPA data. These results demonstrate that this parameter does not significantly influence the recognition process when interactions occur at a single lectin site. Molecular dynamics revealed that glycoconjugates adopt a pseudoglobular structure with a random localization of the lactoside residues. These spatial distributions were observed irrespective of the linker length; this explains the virtually equal affinities recorded by ELLA. In contrast, two‐site “sandwich” ELLA clearly revealed that multivalent derivatives bearing the longest spacers were more efficient for crosslinking lectins. Intrinsic affinities, devoid of aggregation effects, and crosslinking capabilities are, therefore, not directly related phenomena that must be taking into consideration in neoglycoconjugate design for specific applications.  相似文献   
962.
Flow distribution and mass transfer characteristics during CO2‐water flow through a parallel microchannel contactor integrated with two constructal distributors have been investigated numerically and experimentally. Each distributor comprises a dichotomic tree structure that feeds 16 microchannels with hydraulic diameters of 667 μm. It was found that constructal distributors could ensure a nearly uniform gas–liquid distribution at high gas flow rates where the ideal flow pattern was slug‐annular flow. Nevertheless, at small gas flow rates where the ideal flow pattern was slug flow, a significant flow maldistribution occurred primarily due to the lack of large pressure barrier inside each distributor, indicating that dynamic pressure fluctuation in parallel microchannels greatly disturbed an otherwise good flow distribution therein. It was further shown that the present parallel microchannel contactor could realize the desired mass transfer performance previously achieved in one single microchannel under relatively wide operational ranges due to the integration of constructal distributors. © 2009 American Institute of Chemical Engineers AIChE J, 2010  相似文献   
963.
Yves Termonia 《Polymer》2010,51(19):4448-5196
Monte-Carlo simulations of the configurations of polymer chains in reinforced elastomers reveal extensive wrapping of the chains around particle clusters. The resulting increase in chain entanglement density leads to a 3.5 power law dependence of modulus on particle loading, in perfect agreement with experimental observation. Our model also gives a consistent molecular explanation of the Payne effect and the associated energy dissipation in strained reinforced elastomers.  相似文献   
964.
Using a manometric experimental setup, high-pressure sorption measurements with CH4 and CO2 were performed on three Chinese coal samples of different rank (VRr = 0.53%, 1.20%, and 3.86%). The experiments were conducted at 35, 45, and 55 °C with pressures up to 25 MPa on the 0.354-1 mm particle fraction in the dry state. The objective of this study was to explore the accuracy and reproducibility of the manometric method in the pressure and temperature range relevant for potential coalbed methane (CBM) and CO2-enhanced CBM (CO2-ECBM) activities (P > 8 MPa, T > 35 °C). Maximum experimental errors were estimated using the Gauss error propagation theorem, and reproducibility tests of the high-pressure sorption measurements for CH4 and CO2 were performed. Further, the experimental data presented here was used to explicitly study the CO2 sorption behaviour of Chinese coal samples in the elevated pressure range (up to 25 MPa) and the effects of temperature on supercritical CO2 sorption isotherms.The experiments provided characteristic excess sorption isotherms which, in the case of CO2 exhibit a maximum around the critical pressure and then decline and level out towards a constant value. The results of these manometric tests are consistent with those of previous gravimetric sorption studies and corroborate a crossover of the 35, 45, and 55 °C CO2 excess sorption isotherms in the high-pressure range. The measurement range could be extended, however, to significantly higher pressures. The excess sorption isotherms tend to converge, indicating that the temperature dependence of CO2 excess sorption on coals at high-pressures (>20 MPa) becomes marginal. Further, all CO2 high-pressure isotherms measured in this study were approximated by a three-parameter excess sorption function with special consideration of the density ratio of the “free” phase and the sorbed phase. This function provided a good representation of the experimental data.The maximum excess sorption capacity of the three coal samples for methane ranged from 0.8 to 1.6 mmol/g (dry, ash-free) and increased from medium volatile bituminous to subbituminous to anthracite. The medium volatile bituminous coal also exhibited the lowest overall excess sorption capacity for CO2. However, the subbituminous coal was found to have the highest CO2 sorption capacity of the three samples. The mass fraction of adsorbed substance as a function of time recorded during the first pressure step was used to analyze the kinetics of CH4 and CO2 sorption on the coal samples. CO2 sorption proceeds more rapidly than CH4 sorption on the anthracite and the medium volatile bituminous coal. For the subbituminous coal, methane sorption is initially faster, but during the final stage of the measurement CO2 sorption approaches the equilibrium value more rapidly than methane.  相似文献   
965.
Pheromones in social insects play a key role in the regulation of group homoeostasis. It is well-established that parasites can modify hormone signaling of their host, but less is known about the effect of parasites on pheromone signaling in insect societies. We, thus, tested in honey bees (Apis mellifera) the effect of the widespread parasite Nosema spp. on the production of ethyl oleate (EO), the only identified primer pheromone in honey bee workers. Since environmental stressors like pesticides also can weaken honey bees, we also analyzed the effect of imidacloprid, a neonicotinoid widely used in agriculture, on EO production. We show that, contrary to imidacloprid, Nosema spp. significantly altered EO production. In addition, the level of Nosema infection was correlated positively with the level of EO production. Since EO is involved in the regulation of division of labor among workers, our result suggests that the changes in EO signaling induced by parasitism have the potential to disturb the colony homoeostasis.  相似文献   
966.
PACE4 plays important roles in prostate cancer cell proliferation. The inhibition of this enzyme has been shown to slow prostate cancer progression and is emerging as a promising therapeutic strategy. In previous work, we developed a highly potent and selective PACE4 inhibitor, the multi‐Leu (ML) peptide, an octapeptide with the sequence Ac‐LLLLRVKR‐NH2. Here, with the objective of developing a useful compound for in vivo administration, we investigate the effect of N‐terminal modifications. The inhibitory activity, toxicity, stability, and cell penetration properties of the resulting analogues were studied and compared to the unmodified inhibitor. Our results show that the incorporation of a polyethylene glycol (PEG) moiety leads to a loss of antiproliferative activity, whereas the attachment of a lipid chain preserves or improves it. However, the lipidated peptides are significantly more toxic when compared with their unmodified counterparts. Therefore, the best results were achieved not by the N‐terminal extension but by the protection of both ends with the d ‐Leu residue and 4‐amidinobenzylamide, which yielded the most stable inhibitor, with an excellent activity and toxicity profile.  相似文献   
967.
In this study, cellulose nanowhiskers (CNW) were prepared from alfa fiber (Stipa tenacissima) by an alkali treatment at room temperature in association with a bleaching treatment followed by a sulfuric acid hydrolysis. Fourier Transform Infrared (FT-IR) spectroscopy was used to highlight the evolution of chemical composition. Atomic Force Microscopy and Zeta-sizer indicated that the transverse size of the particles varied between 30 nm and 170 nm. Thermal stability was higher for CNW as compared to alfa fiber. FT-IR, X-ray diffraction, and Thermogravimetric analysis studies confirmed the removal of hemicelluloses and lignin during the chemical treatment process. The swelling of CNW in water with Cloisite 30B (CNW/C30B) or with the Polyethylene glycol (CNW/PEG) was carried out. The properties of Polyvinyl Chloride (PVC) nanocomposites reinforced with CNW which was dispersed with two different methods were also compared. The results showed that the morphology of both samples have drastic differences which may explain the fact that the storage modulus prepared with CNW/C30B was higher than those prepared with CNW/PEG. However, PVC/CNW/PEG nanocomposites exhibited more thermal stability. In the end, the obtained CNW may have potential applications in alternative power sources as a reinforcement phase.  相似文献   
968.

Background  

previous studies have shown that non-digestible inulin-type fructan intake can increase intestinal mineral absorption in both humans and animals. However, this stimulatory effect on intestinal absorption may depend on experimental conditions such as duration of fermentable fiber intake, mineral diet levels and animals' physiological status, in particular their age.  相似文献   
969.
Yves Termonia 《Polymer》2011,52(22):5193-5196
We present a Monte Carlo study of the structure of an entangled polymer melt confined between parallel plates separated by a distance smaller than the radius of gyration Rg of the chains. Within that regime, we find a dramatic increase in the molecular weight between entanglements and in the eigenvalues of the gyration tensor of the chains in the plane of the plates. The chains however appear to retain their Gaussian behavior throughout confinement. Interestingly, we also observe that individual chains at short length scales form “globules” whose density and size increase with the extent of confinement.  相似文献   
970.
This work shows the formation of a high internal phase ratio oil‐in‐water (O/W) emulsion using a new type of a two‐rod batch mixer. The mixture components have sharply different viscosities [1/3400 for water‐in‐oil (W/O)], similar densities (1/0.974 for W/O), and an O/W ratio of 91% (wt/wt). The simple design of this mixer leads to a low‐energy process (106 < energy density [J m?3] < 107), characterized by low rotational speed and laminar flow. The droplet size distribution during the emulsification was investigated according to different physical and formulation parameters such as stirring time (few minutes < t < 1 h), rotational speed (60 < Ω < 120 rpm), surfactant type (Triton X‐405 and X‐100), concentration (from 1 to 15.9 wt % in water), and salt addition (30 g/L). We show that all studied parameters allow a precise control of the droplet size distribution and the rheology. The resulting emulsions are unimodal and the mean droplet diameter is between 30 μm and 8 μm. © 2010 American Institute of Chemical Engineers AIChE J, 2011  相似文献   
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