DSpace collection: 期刊論文

Wet nanogranular materials: Colloidal glass and gel

title: Wet nanogranular materials: Colloidal glass and gel abstract: Partially wet granular medium is a mouldable material due to capillary cohesion and its behavior plays key roles in geophysics. However, completely wet nanogranules may also demonstrate mouldable properties via van der Waals attraction and they exhibit colloidal glass or gel characteristics, depending on the solvent. As solvent-enhanced attractions prevail, phase separation is observed and nanogranular gel can be obtained. In contrast, as cage effects dominate, the stable slurry is seen and the nanogranular glass can be prepared. Upon surfactant addition, however, the arrested glass state changes into colloidal gel due to the formation of hydrogen bonds between nanogranules. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3658501]

Using isothermal titration calorimetry to real-time monitor the heat of metabolism: A case study using PC12 cells and A beta(1-40)

title: Using isothermal titration calorimetry to real-time monitor the heat of metabolism: A case study using PC12 cells and A beta(1-40) abstract: Isothermal titration calorimetry (ITC) is one of the most powerful means for direct determination of thermodynamic information associated with most physiochemical and biological processes. The deposition and aggregation of beta-amyloid (A beta) on cell membranes was considered as one of the primary factors in having Alzheimer's disease (AD). Recently, a growing body of evidence has suggested that plasma membrane could accelerate the accumulation of A beta on the plasma membranes. However, the mechanism of AD is still a controversial issue. This study provided a biothermodynamic approach to real-time monitor the heat of metabolism involved in the co-incubation of PC12 cells and A beta(1-40) by ITC. The effects of A beta conformation and concentration of oligomeric A beta on cytotoxicity were successfully distinguished by ITC. This approach with rapid and direct measurement may provide not only real-time information for the effects of A beta species on living cells but also a platform for the screening of drug candidates for AD. (C) 2010 Elsevier B.V. All rights reserved.

Understanding Three Hydration-Dependent Transitions of Zwitterionic Carboxybetaine Hydrogel by Molecular Dynamics Simulations

title: Understanding Three Hydration-Dependent Transitions of Zwitterionic Carboxybetaine Hydrogel by Molecular Dynamics Simulations abstract: In this work, molecular dynamics simulations were performed to study a carboxybetaine methacrylate (CBMA) hydrogel under various swelling states. The water content in this study ranged from 28% to 91% of the total weight of the hydrogel. Three transitions of the CBMA hydrogel were observed as the water content increased. The first transition occurs when the water content increases from 33% to 37%. The observed kink in the self-diffusion coefficient of water indicates that the hydration of the polymer network of the hydrogel is saturated; the further added water is in a less confined state. The second transition was found to be related to the physical cross-links of the polymer network. As the water content rises to above 62%, the lifetime of the physical cross-links decreases significantly. This abrupt change in the lifetime indicates that the transition represents the equilibrium swelling state of the hydrogel. Finally, the third transition was observed when the water content goes above 81%. The significant increases in the bond and angle energies of the polymer network indicate that the hydrogel reaches its upper limit swelling state at this transition. These results are comparable to previously published experimental studies of similar zwitterionic hydrogels.

The effect of poly-N-vinylpyrrolidone modification on NiCoB catalysts for hydrogenation of p-chloronitrobenzene

title: The effect of poly-N-vinylpyrrolidone modification on NiCoB catalysts for hydrogenation of p-chloronitrobenzene abstract: A series of poly-N-vinylpyrrolidone (PVP)-modified NiCoB catalysts with various PVP contents were prepared by chemical reduction method. The Ni and Co cations were reduced by NaBH(4) at room temperature. PVP was added during preparation. The materials were characterized by X-ray diffraction, transmission electron microscopy, and differential scanning calorimeter. The results showed that all samples possessed amorphous structure. After washing, the residual PVP adsorbed on the surface of NiCoB and acted as a spacer to prevent NiCoB particles from aggregation and agglomeration. The liquid-phase hydrogenation of p-chloronitrobenzene was carried out to investigate the catalytic properties of the PVP-modified NiCoB catalysts. The catalytic activities of NiCoB catalysts decreased by modifying with PVP but the selectivities for p-chloroaniline improved significantly. The competitive adsorption of PVP with p-chloronitrobenzene and p-chloroaniline on the NiCoB nanoparticles was responsible for the catalytic performance. The amount of the PVP played a key role in the hydrogenation reaction. (C) 2010 Elsevier B.V. All rights reserved.