Economic aspects of critical flux operability in star shaped microfiltration membranes: Influence of some operating conditions

The economic feasibility of operating at the achievable critical flux under different operating parameters (feed concentration, crossflow velocities and pH) using non-circular channelled membranes has been investigated. The increase in critical fluxes with increasing crossflow velocities is accompanied by increasing axial pressure loss. This leads to substantial increase in the specific energy consumption, reducing the energy-saving potential. Minimum specific energy consumption occurs at the crossflow velocity of 0.9 m s⁻¹ where the trade-off between axial pressure loss and the achievable critical flux occurs. Increasing the feed concentrations and pH led to declining and increasing critical fluxes, respectively. Axial pressure loss remains consistent at feed concentrations <10 g l⁻¹ and increases at feed concentrations >10 g l⁻¹. This is attributed to the change in the viscosity of the suspension which affects the specific energy consumption. The influence of pH on critical flux is attributed to the changes in the titanium dioxide particle charges and coincides with the changes in the viscosity of the suspension. The optimum energy-saving potential was found at pH 9.0. Solution chemistry (particle charges and rheology) and hydrodynamics influence the achievable critical flux and axial pressure loss within these channels which ultimately determine the economics of operation.     

Nanophase separation in segmented polyurethane elastomers: Effect of specific interactions on structure and properties

Polyurethanes were prepared from 4,4′-methylenebis (phenyl isocyanate) (MDI), 1,4-butanediol (BD) and poly (tetrahydrofurane) polyether polyol (PTHF). The -OH functional group ratio of polyol/total diol was kept constant at 0.4 in all experiments, while the ratio of the isocianate and hydroxyl groups (NCO/OH) changed between 0.940 and 1.150. Melt polymerization was carried out in an internal mixer. The polymers were characterized with a number of methods including GPC, FTIR, WAXS, DSC, DMA and tensile testing. Changing stoichiometry modifies molecular weight as expected, but the relative concentration of end-groups also changes at the same time. The respective end-groups preferentially associate with each other leading to phase separation. -OH end-groups enter into weaker interactions with each other than urethane and amine groups. The extent of phase separation, as well as the size and properties of the dispersed phase depend on composition. Each property of the polymer is affected differently by molecular weight and phase separation. Melt viscosity depends mostly on the length of the molecules, ultimate tensile properties are influenced also by interactions, while stiffness is determined almost exclusively by phase structure.     

Sensitive Electrochemical Prostate Specific Antigen Aptasensor: Effect of Carboxylic Acid Functionalized Carbon Nanotube and Glutaraldehyde Linker

The performance of carboxylic acid functionalized carbon nanotubes (CNTs_(COOH)), chitosan (Chit), carbon nanotubes‐chitosan (CNTs‐Chit and CNTs_(COOH)‐Chit) for immobilizing of amino‐functionalized ssDNA and fabrication of electrochemical prostate specific antigen (PSA) aptasensor were studied in detail using X‐ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR) and electrochemical impedance spectroscopy (EIS). The assemblies of capture probe are formed on the surface via two approaches: EDC/NHS chemistry and glutaraldehyde linker. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and EIS techniques were used to investigate the analytical performance of the PSA aptasensor. Under optimum conditions the sensitivity of 0.0026 µA/(ng/ml) and a limit of detection of 0.75 ng/ml (22 pM) were obtained for PSA detection. This protocol offers a new means for sensitive detection of PSA with some advantages in terms of simplicity, selectivity, ease of use and regenerability.     

Novel thermally stable and chiral poly(amide-imide)s bearing from N,N′-(4,4′-diphthaloyl)-bis-l-isoleucine diacid: Synthesis and characterization

Novel optically active aromatic poly(amide-imide)s (PAIs) were prepared from newly synthesized N,N′-(4,4′-diphthaloyl)-bis-l-isoleucine diacid (3) via polycondensation with various diamines. The diacid was synthesized by the condensation reaction of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (1) with l-isoleucine (2) in a mixture of acetic acid and pyridine (3:2 v/v). All the polymers were obtained in quantitative yields with inherent viscosities of 0.20-0.43 dL g⁻¹. All the polymers were highly organosoluble in solvents like N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, γ-butyrolactone, cyclohexanone and chloroform at room temperature or upon heating. These poly(amide-imide)s had glass transition temperatures between 198 and 231 °C, and their 10% weight-loss temperatures were ranging from 368 to 398 °C and 353 to 375 °C under nitrogen and air, respectively. The polyimide films had tensile strengths in the range of 63-88 MPa and tensile moduli in the range of 0.8-1.4 GPa. These poly(amide-imide)s possessed chiral properties and the specific rotations were in the range of −3.10° to −72.92°.     

A Novel Stepwise Recovery Strategy of Cellulase Adsorbed to the Residual Substrate after Hydrolysis of Steam Exploded Wheat Straw

Cellulase distribution between residual substrate and supernatant in the process of enzymatic hydrolysis of steam-exploded wheat straw was investigated. Subsequently, a novel stepwise recovery strategy with three successive steps was adopted to recover cellulase adsorbed to the residual substrate. The results showed that cellulase protein in the supernatant increased as the hydrolysis time increased. When hydrolysis ended, the cellulase remaining on the residual substrate accounted for 33–42% of the original added cellulase according to the different cellulase loading. To obtain the maximum cellulase recovery rate, the residual substrate was dealt with in three successive steps: washed with sodium acetate buffer (step 1), shaken with sodium acetate buffer (step 2), and then treated with 0.0015 mol/L, pH 10 Ca(OH)₂ (step 3). The total cellulase protein recovered by the three steps reached 96.70–98.14%. The enzyme activity of cellulase recovered by the first two steps was kept well. The ratios of the specific activity between the recovered cellulase and the original were 89–96%, which was by far higher than that using step 3 (the value was 48% ∼ 56%).     

Ballistic phonon studies in the lowest Landau level

We report time-resolved studies of ballistic phonon absorption in the fractional quantum Hall regime at Landau level filling factors of and . The technique used can resolve the interaction of the two-dimensional electron system with LA and TA phonons and has been used to measure the temperature variation of the heat capacity of a single layer of electrons at . The energy gaps at have also been measured and found to be in good agreement with theory. The roles of compressible and incompressible regions in the phonon absorption process are discussed. Angle resolved measurements at are also in good agreement with theory.     

Integrating trace Ti-doping and LiYO2-coating to stabilize Ni-rich cathodes for lithium-ion batteries

Ni-rich layered cathodes have become the promising candidates for the next-generation high-energy Li-ion batteries due to their high energy density and competitive cost. However, they suffer from rapid capacity fading due to the structural and interfacial instability upon long-term operation. Herein, the Ti-doped and LiYO₂-coated Ni-rich layered cathode has been synthesized via a facile one-step sintering strategy, which significantly restrains the interfacial parasitic side reactions and enhances the structural stability. Specifically, the trace Ti⁴⁺ doping greatly stabilizes the lattice oxygen and alleviates the Li/Ni disorder while the LiYO₂ coating layer can prevent the erosion of the cathode by the electrolyte during cycles. As a result, the Ti-NCM83@LYO delivers a high specific capacity of 135 mAh g⁻¹ even at 10C and there is almost no capacity loss at 1C for 100 cycles. This work provides a simple one-step dual-modification strategy to meet the commercial requirements of Ni-rich cathodes.     

Yb3Cu9(OH)19Cl8 单晶的生长和低温磁性研究

本文介绍了新型kagomé 晶格化合物 Yb3Cu9 (OH)19Cl8 单晶的生长及磁性质研究. 利用水热法制备了高品质的 Yb3Cu9 (OH)19Cl8 单晶,X 射线衍射的精修结果表明,Cu2+ 离子在ab 面内形成kagomé 结构,Yb3+ 离子处在kagomé 六角晶格的中心. 磁化率结果表明 Yb3Cu9 (OH)19Cl8 在温度低至2 K 仍没有磁有序转变, 表现出明显的顺磁行为. 居里-外斯拟合结果显示, 磁性离子间具有强的反铁磁耦合相互作用. 温度低至2 K 的比热曲线上没有明显的磁相变行为的出现, 而是表现出典型的肖特基特征     

Magnetic properties of (Ce1−xLax)PdIn2

We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce_1−xLa_x)PdIn₂ system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at T_C is only weakly dependent on x (ΔS≅0.92Rln2) indicating that T_K/T_C is approximately constant along the series. The T_C and T_K behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce_1−xLa_x)PdIn₂ system.     

Crystal electric field excitations in ferromagnetic CeTX compounds

A ferromagnetic ground state was identified for the compounds CeCuGe (T_C=10 K), CeCuSi (T_C=15 K) [F. Yang, et al., J. Appl. Phys. 69 (1991) 4705] and CeAuGe (T_C=10 K) [R. Pottgen, J. Magn. Magn. Mater. 152 (1996) 196]. The observed saturation magnetic moment values at low temperatures for all three compounds are considerably less than the theoretically expected value g_JJ=2.14μ_B for the free Ce³⁺ ion involving the entire six-fold J=5/2 multiplet, and thus provide a first indication of partial lifting of the f-electron level degeneracy in these compounds. Specific heat data yield crystal electric field (CEF) excitation energies (Δ_Sch) equivalent to 140 K for CeCuGe, 110 K for CeCuSi and 280 K for CeAuGe. To confirm the presence of CEF excitations directly, we have carried out inelastic neutron scattering (INS) measurements on all three compounds, using the HET spectrometer at ISIS Facility. Here, we present a detailed analysis of the INS spectra of CeCuSi on the basis of a CEF model and the detailed analysis of the INS of the other two compounds will be reported elsewhere.