Comparison of the formation epitaxial graphenes on Si- and process and properties of C-face 6H-SiC substrates

In this paper,the epitaxial graphene layers grown on Si-and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600 C.By using atomic force microscopy and Raman spectroscopy,we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates,including the hydrogen etching process,the stacking type,and the number of layers.Hopefully,our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.     

Potentiometric determination of dialysate urea nitrogen

An enzymatically modified ammonium ion-selective electrode has been applied for the determination of urea in spent dialysate. The biosensor has been used in a simple flow-injection analysis (FIA) system. The system enables one to perform over 25 dialysate urea nitrogen (DUN) determinations per hour. The interferences from other components of posthemodialysis fluid were eliminated by simultaneous measurements with non-modified enzymatically ion-selective electrode. It is possible to use both the sensors in a simplified differential potentiometric system. The results of DUN determination using the biosensor/FIA system and a conventional method of urea determination were comparable. The presented analytical system can potentially find wider biomedical application in the monitoring of hemodialysis progress.     

The distribution of Ga and Sb impurities in Ge-Si crystals grown by the Bridgman method using a feeding rod

Gallium- and antimony-doped Ge_{1 ? x} Si _x crystals (0 ≤ x ≤ 0.25) have been grown by the improved Bridgman method using a silicon seed and a macrohomogeneous feeding Ge-Si rod of the corresponding composition. The impurity concentration profiles along the grown crystals were determined from Hall measurements. The mathematical problem of impurity distribution along two-component mixed crystals grown from a melt with uniform and graded composition is solved in the Pfann approximation and within the virtual-crystal model for the solid solution. It is shown that the experimental impurity distributions in Ge_{1 ? x} Si _x crystals are described well by the data calculated on the assumption of linear change in the impurity segregation coefficient with the crystal composition.     

A deterministic method study of the impact of the Pauli principle in double-gate MOSFETs

The Pauli principle is included in a multisubband deterministic solver for two-dimensional devices without approximations.The nonlinear Boltzmann equations are treated properly without compromising on accuracy,convergence,or CPU time.The simulation results indicate the significant impact of the Pauli principle on the transport properties of the quasi-2D electron gas,especially for the on state.     

Asymptotic solution for the El Nio time delay sea-air oscillator model

A sea-air oscillator model is studied using the time delay theory.The aim is to find an asymptotic solving method for the El Nio -southern oscillation (ENSO) model.Employing the perturbed method,an asymptotic solution of the corresponding problem is obtained.Thus we can obtain the prognoses of the sea surface temperature (SST) anomaly and the related physical quantities.     

Tb1-xLnxA3(A=对氨基苯甲酸,x=0-0.9)固体配合物的光谱分析和荧光增强

合成了一系列组成为 Tb1-x Lnx A3 (L n=Gd、Y、La,A=对氨基苯甲酸 ,x=0— 0 .9)的固体配合物。利用红外光谱和荧光光谱研究了配合物的结构和荧光性质 ,结果表明 ,掺杂配合物的结构与未掺杂的对氨基苯甲酸铽相似。荧光光谱的结果显示 ,Gd3 对 Tb3 的发光有明显的增敏作用 ,探讨了荧光增敏机理。     

Strain gauges of GaSbFeGa<Subscript>1.3</Subscript> eutectic composites

A needle-shaped metallic FeGa_1.3 phase oriented in a specific direction and uniformly distributed within a GaSb matrix was grown by a vertical Bridgman method. Strain-gauge characteristics, such as strain-sensitivity coefficient (S), temperature coefficient of strain sensitivity (TCS) and temperature coefficient of resistance, of GaSb and GaSbFeGa_1.3 eutectic alloy have been investigated in the range of 200 to 400 K under deformation up to strains of 1.3×10^-3. The value of S of the GaSbFeGa_1.3 composition is measured to be 40±5 and its TCS is about 0.2 %deg^-1 when the current is perpendicular to the needles and the needles are parallel to the plane of the gauge substrate. The strain-sensitivity characteristics are linear and hysteresis free in the investigated temperature range in the aforementioned direction. It was found that GaSbFeGa_1.3-based strain gauges possess better deformation characteristics than GaSb-based gauges. PACS 72.80.Tm; 73.40.-c; 77.65.-j     

Exploration of a Cheaper Carbon Source for Extracellular β-glucosidase Synthesis from <Emphasis Type="Italic">Debaryomyces pseudopolymorphus</Emphasis> NRRL YB-4229

In the present work, interactions between common media components and fermentation conditions were explored to come up with a simple media recipe for extracellular β-glucosidase (Dβ-gl) synthesis from Debaryomyces pseudopolymorphus to substitute cellobiose, which is currently used as a sole carbon source. Taguchi L₂₅ orthogonal array design was used to screen factors influencing Dβ-gl synthesis (carbon, organic nitrogen, inorganic nitrogen, trace elements, inoculum volume, and fermentation time). A significant influence of xylose, peptone, and potassium nitrate as carbon, organic nitrogen, and inorganic nitrogen sources, respectively, on Dβ-gl synthesis was identified by Taguchi. These factors were further optimized using central composite rotatable design (CCRD) of response surface methodology (RSM). The results showed that in the range studied, potassium nitrate had insignificant effect while xylose, peptone, and xylose-peptone interaction had a significant effect on Dβ-gl synthesis. Peptone/xylose ratio of 1.33 was found to be an important parameter for inducing Dβ-gl synthesis. The regression coefficient (R ²) of 0.915 and P value of <0.0003 for the model indicated that it was highly significant. The maximum activity obtained after RSM (32.2 U/ml) was comparable with that obtained (68.8 U/ml) when cellobiose (20 g/l) was used as a sole carbon source. Considering the cost difference between xylose and cellobiose, a 16-fold cost reduction could be obtained for equivalent Dβ-gl yield. Fed-batch fermentations were carried out wherein peptone/xylose ratio of 1.33 was maintained and continuous Dβ-gl synthesis was observed.     

Bound states of the Dirac equation with position-dependent mass for the Eckart potential

Studying with the asymptotic iteration method, we present approximate solutions of the Dirac equation for the Eckart potential in the case of position-dependent mass. The centrifugal term is approximated by an exponential form, and the relativistic energy spectrum and the normalized eigenfunctions are obtained explicitly.