Transport Properties of K_xV_2O_5·nH_2O Nanocrystalline Films

Five different compositions of K x V 2 O 5 ·nH 2 O(where x=0.00,0.0017,0.0049,0.0064 and 0.0091 mol) were prepared by the sol-gel process.Electrical conductivity and thermoelectric power were measured parallel to the substrate surface in the temperature range of 300-480 K.The electrical conductivity showed that all samples were semiconductors and that conductivity increased with increasing K content.The conductivity of the present system was primarily determined by hopping carrier mobility.The carrier density was evaluated as well.The conduction was confirmed to obey non-adiabatic small polaron hopping.The thermoelectric power or Seebeck effect,increased with increasing K ions content.The results obtained indicated that an n-type semiconducting behavior within the temperature range was investigated.     

A revisited generalized self-consistent polycrystal model following an incremental small strain formulation and including grain-size distribution effect

A generalized self-consistent approach, recently proposed by Jiang and Weng (2004) [B. Jiang, G.J. Weng, A generalized self-consistent polycrystal model for the yield strength of Nanocrystalline materials, Journal of the Mechanics and Physics of Solids 52 (2004a) 1125-1149; B. Jiang, G.J. Weng, A theory of compressive yield strength of nano-grained ceramics, International Journal of Plasticity 20 (2004b) 2007-2056.] for investigating the so-called “breakdown” of the Hall-Petch law in the case of nanocrystalline (NC) materials, is revisited and reformulated following an incremental small strain scheme. The NC material is modelled as a composite material that takes each oriented grain and its immediate grain boundary to form a pair, which in turn is embedded in the infinite effective medium with a property representing the average orientation of all these pairs. The plastic deformation of the inclusion phase takes into account the dislocation glide mechanism whereas boundary phase is modelled as an amorphous material. As an application, the model’s parameters are identified under an optimization code with respect to data stated from pure copper submitted to tensile load. The aggregate is composed of spherical randomly distributed grains with a grain-size distribution following a log-normal statistical function.     

Preparation of water soluble chitosan by hydrolysis with commercial α-amylase containing chitosanase activity

Water soluble chitosan (WSC) was prepared by hydrolysing chitosan using α-amylase. The degradation was monitored by WSC recovery and the WSC structure was characterised by Fourier transform infrared spectroscopy. The optimal hydrolysis conditions were found to be at pH 5, 50 °C, 20 mg α-amylase in the reaction solution, with a reaction time of 4 h. Under these conditions, the average molecular weight of chitosan decreased to 730 Da. The resulting products were composed of chitooligosaccharides of DP 3–7. The hydrolysate was neutralised with 1 M NaOH, filtered, concentrated to 16% (w/v), precipitated with five volumes of ethanol to one volume of the concentrated hydrolysate solution, and dried at 60 °C for 3 h to yield a white powder. The WSC content of the product and the yield were 96.2% and 91.2% (w/w), respectively.     

αs-casein inhibits the pressure-induced aggregation of β-lactoglobulin through its molecular chaperone-like properties

In this work, the effects of α_s-casein (α_s-CN) on the pressure-induced aggregation of β-lactoglobulin (β-Lg) were studied. α_s-CN depressed the pressure-induced aggregation of β-Lg, and this function was dependent on the concentration of α_s-CN and the pressure holding time. Furthermore, α_s-CN altered the aggregation process of β-Lg by suppressing the transition of the aggregate from the soluble phase to the insoluble phase and, as a result, the fraction of insoluble aggregates was decreased. During this process, α_s-CN formed stable complexes with the denatured β-Lg and the formation of complexes prevented further aggregation of β-Lg and solubilized aggregated β-Lg to a small degree of polymerization. These results indicate that α_s-CN exhibits a chaperone-like activity under high pressure, and provide an insight into the possible mechanism by which α_s-CN accomplishes the task of stabilizing proteins to resist the pressure-induced aggregation of β-Lg.     

Novel peptides derived from egg white protein inhibiting alpha-glucosidase

The aim of this study was to search and identify potential anti-diabetic peptides with α-glucosidase and α-amylase inhibitory activities. After the Alcalase hydrolysis, egg white protein hydrolysates were purified and identified by LC–MS–MS. Eight identified peptides were further synthesized by the Fmoc solid-phase synthesis. The anti-diabetic activities of these synthetic peptides were assessed using enzymatic inhibitory assays against the α-glucosidase and α-amylase. Among the eight peptides, peptide RVPSLM was discovered as a potential α-glucosidase inhibitor with an IC₅₀ value at 23.07 μmol L⁻¹. However, it did not exhibit a visible or detectable inhibitory efficiency on the α-amylase. These studies indicate the potential of using egg white protein hydrolysates as a functional food product with the anti-diabetic activity.     

Studies on the adsorption of RuN3 dye on sheet-like nanostructured porous ZnO films

The interface between the ZnO and dye directly impacts the dye-sensitized solar cell (DSSC) performance. Nanostructured porous ZnO film was developed by a simple chemical solution process. Scanning electron microscope (SEM) images demonstrated the uniform ZnO films with sheet-like nanostructure. Adsorption studies indicated that the maximum adsorption capacity of RuN₃ dye on the surface of ZnO films was approximately 0.016 mmol RuN₃/g ZnO films. Adsorption studies were conducted at 25 and 40 °C. The results showed that the dye adsorption was significantly influenced by temperatures. Moreover, the problem of the dye aggregation on the ZnO surface was reduced at higher adsorption temperatures. The adsorption chemistry was studied with Raman spectroscopy.     

Nanocrystalline matrix TiC–Al3Ti and TiC–Al3Ti–Al composites produced by reactive hot-pressing of milled powders

Mechanically alloyed nanocrystalline TiC powder was short-term milled with 40 vol.% of Al powder. The powders mixture was consolidated at 1200 °C under the pressure of 4.8 GPa for 15 s and at 1000 °C under the pressure of 7.7 GPa for 180 s. The bulk materials were characterised by X-ray diffraction, light and scanning electron microscopy, energy dispersive spectroscopy, hardness, density and open porosity measurements. During the consolidation a reaction between TiC and Al occurred, yielding an Al₃Ti intermetallic. The microstructure of the produced composites consists of TiC areas surrounded by lamellae-like regions of Al₃Ti intermetallic (after consolidation at 1200 °C) or Al₃Ti and Al (after consolidation at 1000 °C). The mean crystallite size of TiC is 38 nm. The hardness of the TiC–Al₃Ti and TiC–Al₃Ti–Al composites is 13.28 GPa (1354 HV1) and 10.22 GPa (1041 HV1) respectively. The produced composites possess relatively high hardness and low density. The results obtained confirmed satisfactory quality of the consolidation with keeping a nanocrystalline structure of TiC.     

Novel α-glucosidase inhibitors from Macaranga tanarius leaves

One of the hyperglycaemic remedies is glucose absorption reduction by suppressing carbohydrate digestion due to utilisation of α-glucosidase inhibitors (AGIs). Determination of prospecting herbs done in vitro by using enzyme assay resulted in the finding of Macaranga tanarius, which showed a potent inhibitory activity. An EtOAc-soluble extract of M. tanarius leaves was chromatographed by a Diaion HP-20 column and the active fractions were further purified with high performance liquid chromatography (HPLC) to isolate active principles against α-glucosidase. Five ellagitannins were successfully isolated and identified. Structure determination revealed that these isolated compounds were mallotinic acid (IC₅₀ > 5.00 mM), corilagin (IC₅₀ = 2.63 mM), chebulagic acid (IC₅₀ = 1.00 mM), and two novel compounds named macatannins A (IC₅₀ = 0.80 mM) and B (IC₅₀ = 0.55 mM). AGIs play an important role for the treatment of diabetes, therefore this research results may suggest novel alternatives for diabetes treatment management.