Universal structural parameter to quantitatively predict metallic glass properties.

Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce 'flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parameter correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales.

A simple fabrication method for tapered capillary tip and its applications in high-speed CE and ESI-MS.

Fabrication of capillaries with tapered tips is an important technique that is required in many analytical chemistry areas, such as ESI-MS, CE, electrochemical analysis, and microinjection. This paper describes a simple and effective grinding-based fabrication method for capillaries with tapered tips. A novel grinding mode utilizing the combination of rotation and precession of an elastic capillary was developed, which significantly improved the controllability to the grinding process as well as the capillary tip shape. The capillary was fabricated by fixing it in an electric drill installed perpendicularly, and grind the capillary tip rotated around its own axis as well as the drill axis on sandpapers. Compared with conventional fabrication techniques for capillary tips, the present method is easy to control the capillary tip shape in routine laboratories without the requirement of expensive equipments or poisonous reagent (e.g. hydrofluoric acid (HF) solution). Various capillaries with different tip diameters and tip taper angles could be fabricated using the present method with good controllability and reproducibility. These capillaries were applied in high-speed CE and ESI-MS analysis to demonstrate the feasibility and potential of this fabrication method.

A three-dimensional polycatenation framework: catena-poly[[diaquabis(4-{4-[4-(pyridin-4-yl)phenoxy]phenyl}pyridine)nickel(II)]-µ2-naphthalene-2,6-dicarboxylato].

In the title compound, [Ni(C12H6O4)(C22H16N2O)2(H2O)2]n, the Ni(2+) cation resides on a centre of inversion in a slightly distorted octahedral [N2O4] environment. The two carboxylate groups of each naphthalene-2,6-dicarboxylate (NDC(2-)) ligand, which reside on centres of inversion, link the Ni(II) cations into a one-dimensional chain. Identical chains are linked by intermolecular hydrogen bonds between coordinated water molecules and the uncoordinated N atoms of 4-{4-[4-(pyridin-4-yl)phenoxy]phenyl}pyridine ligands to form (4,4)-topological sheets, and then the different sheets are interlocked in an inclined fashion to give a three-dimensional polycatenation network. The stability of the structure is further enhanced by π-π stacking interactions between pyridine and benzene rings.

Automated high-speed CE system for multiple samples.

A high-speed CE system for multiple samples was developed based on a short capillary and an automated sample introduction device consisting of a commercial multi-well plate and an x-y-z translation stage. The spontaneous injection method was used to achieve picoliter-scale sample injection from different sample wells. Under the optimized conditions, a 40 µm-long sample plug (corresponding to 78-pL plug volume) was obtained in a 50 µm id capillary, which ensured both the high separation speed and high separation efficiency. The performance of the system was demonstrated in the separation of FITC-labeled amino acids with LIF detection. Five FITC-labeled amino acids including arginine, phenylalanine, glycine, glutamic acid, and asparagine were separated within 15 s with an effective separation length of 1.5 cm. The separation efficiency ranged from 7.96 × 10(5)/m to 1.12 × 10(6)/m (corresponding to 1.26-0.89 µm plate heights). The repeatability of the peak heights calibrated with an inner standard for different sample wells was 2.4 and 2.7% (n = 20) for arginine and phenylalanine, respectively. The present system was also applied in consecutive separations of 20 different samples of FITC-labeled amino acids with a whole separation time of less than 6 min.

Approaching the ideal elastic limit of metallic glasses.

The ideal elastic limit is the upper bound to the stress and elastic strain a material can withstand. This intrinsic property has been widely studied for crystalline metals, both theoretically and experimentally. For metallic glasses, however, the ideal elastic limit remains poorly characterized and understood. Here we show that the elastic strain limit and the corresponding strength of submicron-sized metallic glass specimens are about twice as high as the already impressive elastic limit observed in bulk metallic glass samples, in line with model predictions of the ideal elastic limit of metallic glasses. We achieve this by employing an in situ transmission electron microscope tensile deformation technique. Furthermore, we propose an alternative mechanism for the apparent 'work hardening' behaviour observed in the tensile stress-strain curves.

Acetylcholinesterase inhibitory activity of Chinese sufu (fermented tofu) ethanol-extract.

Acetylcholinesterase (AChE) inhibitory activities of commercial sufu and self-produced sufu were investigated in this experiment. The anti-AChE activities of commercial sufu samples of 15 brands, sourcing from various parts of China, and self-produced sufu, fermented with Actinomucor elegans 3.118, were measured. The results indicated that ethanol extract of Chinese sufu exhibited significant inhibitory activity against AChE in vitro. The inhibitory activity of No. 5 sufu was the strongest (IC50, 0.191 mg/ml), while the pre-fermented sufu showed the highest inhibitory activity during sufu manufacturing. In addition, soybean extracts and potato extracts were used to culture A. elegans 3.118 in order to estimate which culture was preferable for the production of these AChE inhibitors. The soybean extracts, after fermentation by A. elegans 3.118, showed higher anti-AChE activity than did the potato extracts. The IC50 of the soybean extracts was 1.29 µg/ml.

High-speed separation of proteins by sodium dodecyl sulfate-capillary gel electrophoresis with partial translational spontaneous sample injection.

In this study, we developed a picoliter-scale partial translational spontaneous injection approach which is suitable for high-speed protein separation under sodium dodecyl sulfate-capillary gel electrophoresis mode. On the basis of this approach, we built a high-speed CE system for protein separation based on a short capillary and slotted-vial array. The system has the advantages of simple structure, ease of building without the requirement of microfabricated devices, convenient operation, and low cost. Under the optimized conditions, picoliter-scale sample plugs (corresponding to ∼65 µm plug length) were obtained, which ensured both the high speed and the high efficiency in protein separation. Five fluorescein isothiocyanate labeled proteins including myoglobin, egg albumin, bovine serum albumin, phosphorylase b, and myosin were separated within 60 s with an effective separation length of 1.5 cm. Theoretical plates per meter ranging from 2.58×105 to 1.28×106 (corresponding to 0.78-3.88 µm plate height) were obtained. The separation speed and separation efficiency of the present system are comparable to those of most microchip-based capillary electrophoresis systems for protein separation. The relative standard deviations of the migration times were in the range of 0.9-1.3% (n=5). Good linear relationships between log relative molecular mass and migration time were obtained in the molecular weigh range of 17,200-500,000, which demonstrate the present system can be applied in protein relative molecular mass determination.

Electron-beam-assisted superplastic shaping of nanoscale amorphous silica.

Glasses are usually shaped through the viscous flow of a liquid before its solidification, as practiced in glass blowing. At or near room temperature (RT), oxide glasses are known to be brittle and fracture upon any mechanical deformation for shape change. Here, we show that with moderate exposure to a low-intensity (<1.8×10(-2) A cm(-2)) electron beam (e-beam), dramatic shape changes can be achieved for nanoscale amorphous silica, at low temperatures and strain rates >10(-4) per second. We show not only large homogeneous plastic strains in compression for nanoparticles but also superplastic elongations >200% in tension for nanowires (NWs). We also report the first quantitative comparison of the load-displacement responses without and with the e-beam, revealing dramatic difference in the flow stress (up to four times). This e-beam-assisted superplastic deformability near RT is useful for processing amorphous silica and other conventionally-brittle materials for their applications in nanotechnology.

Purification and identification of 1-deoxynojirimycin (DNJ) in okara fermented by Bacillus subtilis B2 from Chinese traditional food (Meitaoza).

This study was to purify an alpha-glucosidase inhibitor from okara (soy pulp) fermented by Bacillus subtilis B2 and to identify its chemical structure. Membrane dialysis, active charcoal, CM-Sepharose chromatography, and preparative thin-layer chromatography (TLC) were used in the purification, while positive mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectrometry were used in the identification. The MS and NMR data showed that the purified alpha-glucosidase inhibitor was 1-deoxynojirimycin (DNJ) with a molecular weight of 163 Da. This is the first time that DNJ was isolated from foods fermented with Bacillus species. Okara fermentation with B. subtilis B2 might be used to produce a food-derived DNJ product as a functional food for diabetic patients.

An automated capillary electrophoresis system for high-speed separation of DNA fragments based on a short capillary.

A high-speed DNA fragment separation system was developed based on a short capillary and a slotted-vial array automated sample introduction system. The injection process of DNA sample in a short capillary was investigated systematically with three injection techniques including constant-field-strength, low-field-strength and translational spontaneous injections. Under the optimized conditions, picoliter-scale sample plugs (corresponding to ca. 20-µm plug length) were obtained, which ensure the high-speed and high-efficiency separation for DNA fragments with a short effective separation length. Other separation conditions including the sieving matrix concentration, separation field strength and effective separation length were also optimized. The present system was applied in the separation of ΦX174-Hae III digest DNA marker. With an effective separation length of 2.5 cm, the separation could be achieved in <100 s with plate heights ranging from 0.21 to 0.74 µm (corresponding to plate numbers from 4.86 × 10(6) to 1.36 × 10(6)/m). The repeatabilities for the migration time of the eleven fragments were between 0.4 and 1.1% RSD (n=8). By using the automated continuous injection method, the separation for four different DNA samples could be achieved within 250 s. The present system was further applied in the fast sizing of real DNA samples of PCR products.

Effects of sources of carbon and nitrogen on production of α-glucosidase inhibitor by a newly isolated strain of Bacillus subtilis B2.

This study examined production of α-glucosidase inhibitors by Bacillus subtilis B2 in Luria-Bertani (LB) fermentation with okara, soy powder, starch or pectin as additional source of carbon and nitrogen. All the fermentation broths of B. subtilis B2 exhibited gradual increase in α-glucosidase inhibitory activity during the fermentation process with or without supplemented source of carbon or nitrogen. Addition of okara into the LB medium greatly enhanced the strength (nearly twice as much of that without okara supplement) of α-glucosidase inhibitory activity of fermentation broth. The α-glucosidase inhibitory activity of B. subtilis B2 fermentation broth was positively correlated (p<0.05) with the bacterial populations grown in LB medium containing okara. Glucose and sucrose were not detected in LB medium during the entire fermentation process and were both reduced drastically in media containing okara, soy powder, starch or pectin after 6days of fermentation. The fermented LB medium containing okara by B. subtilis B2 possessed very strong α-glucosidase inhibitory activity and contained little glucose and sucrose, suggesting that fermentation of B. subtilis B2 in LB added with okara might be considered as a strategy for preparing functional foods for diabetic patients.