[en] We have developed a simple volumetric method for oxygen content determination in high-T_c materials. Application of this method in Fe and Co doped YBa₂Cu₃O_y systems is presented in this paper. This method shows several advantages. First, the apparatus is simple and inexpensive, so it can be widely used. Second, the operational procedure is simple and time saving. Moreover, the oxygen contents determined using this method are quite accurate. According to the error analysis, we found that the experimental accuracy can be improved further by reducing the original gas volume in the apparatus and increasing the sample mass. Besides the high-T_c copper oxides, this method can also be used to determine the oxygen content of other materials such as the colossal magnetoresistance materials

[en] The effect of replacement Cu by V in La_2-xSr_xCuO_4+δ system has been studied in this paper. XRD analysis shows that La_1.85Sr_0.15Cu_1-xV_xO_4+δ keeps tetragonal structure with the concentration of V increasing from 0.0 to 0.15. Resistance and Meissner measurement show that the substitution of V will destroy the superconductivity in this system. The well-defined 'T_c-onset' systematically shifts to lower temperature with increasing V concentration and disappears at x=0.15. It is much higher than that of the La_1.85Sr_0.15Cu_1-xM_xO_4+δ (M=Fe, Co, Ni, Zn, Mg, Al and Ga) systems, in which T_c's disappear when x are small (x=0.04 at most). A possible explanation for this phenomenon is presented

[en] Boron nitride (BN) nanometer thin films are synthesized on Si (1 0 0) substrates by RF reactive magnetron sputtering. Then the film surfaces are treated in the case of the base pressure below 5 x 10^-4 Pa and the temperature of 800 and 1000 deg. C, respectively. And the films are studied by Fourier transform infrared spectra (FTIR), atomic force microscopic (AFM) and field emission characteristics at different annealing temperature. The results show that the surface heat treatment makes no apparent influence on the surface morphology of the BN films. The transformations of the sample emission characteristics have to do with the surface negative electron affinity (NEA) of the films possibly. The threshold electric fields are lower for BN samples without heat-treating than the treated films, which possibly ascribed to the surface negative electron affinity effect. A threshold field of 8 V/μm and the emission current of 80 μA are obtained. The surface NEA is still presence at the heat treatment temperature of 800 deg. C and disappeared at temperature of 1000 deg. C

[en] The site occupancy, structure, and bonding properties of O in an NiAl grain boundary (GB) have been investigated by employing a first-principles total energy method based on density functional theory with the generalized gradient approximation and ultrasoft pseudopotential. The Σ5(310)/[001] tilt GB of NiAl has been chosen because (i) the Σ = 5 GB has been observed to be a higher fraction in NiAl experimentally, and (ii) the Σ5(310)/[001] is energetically favorable in comparison with the Σ5(210)/[001]. The NiAl GB is shown to favor the O segregation with a segregation energy of -1.75 eV, indicating that most of the O impurity will distribute in the NiAl GB thermodynamically. Moreover, O is shown to prefer occupying the interstitial sites rather than the substitutional sites in the GB according to the calculated formation energies. The O-Al bond is energetically favorable as compared with the O-Ni bond due to different electronegativity of Al and Ni in reference to O. Charge distribution and the density of states further indicate the intrinsic bonding properties of O-Al that contain obvious covalent characteristics. It is interesting to find that O is coplanar with the surrounding Al atoms in both interstitial and substitutional cases with lower formation energies, forming stronger coplanar O-Al bonding clusters. Such stronger bonding clusters in the GB can embrittle the NiAl intermetallics and thus are not beneficial to the plasticity of NiAl. Our results will provide a useful reference for improving the mechanical properties and for understanding the oxidation effect of the NiAl intermetallics.

[en] Objective: To summarize the diagnostic efficacy of ADC value for differentiation of benign and malignant lymph nodes on diffusion MRI with Meta-analysis. Methods: Published papers on differentiation of benign and malignant lymph nodes with ADC value were searched and reviewed. Quality evaluation was performed for the eligible papers before data extraction.Test for heterogeneity was performed first, then appropriate model was selected to calculate the weighted mean difference, sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio,pretest and posttest probability. The potential of ADC value for differentiation of benign and malignant lymph nodes was assessed qualitatively and quantitatively. Results: Fifteen papers including 735 cases and 1963 lymph nodes were selected. According to Meta-regression analysis, subgroup analysis and robust analysis, two studies with benign lymph nodes in patients with benign lesion and one study using chemical shift saturation technique were excluded because of their impact on the robustness of the pooled results. The weighted mean difference (WMD) between malignant and benign lymph nodes was -0.355 × 10"-"3 mm"2/s [95% confidence interval (CI):-0.423 ×10-3- -0.288 × 10"-"3 mm"2/s]. Although the cutoff of ADC value for differentiation in each study was different, the diagnostic efficacy was stable, the pooled sensitivity,specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio and area under summarized receiver operator's curve were 0.87 (95% CI: 0.79-0.92), 0.87 (95% CI: 0.82-0.90), 6.5 (95% CI: 4.7-9.2), 0.15 (95% CI: 0.09-0.25), 43 (95% CI: 21-87), 0.93 (95% CI: 0.90-0.95). The posttest malignancy probability of benign lymph node indicated by ADC was 6%, while that of malignant lymph node was 72%. Conclusion: The ADC value can be used to differentiate benign and malignant lymph nodes with good sensitivity and specificity noninvasively. (authors)

[en] Ordered porous polymer (OPP) materials have extensively application prospects in the field of separation and purification, biomembrane, solid supports for sensors catalysts, scaffolds for tissue engineering, photonic band gap materials owing to ordered pore arrays, uniform and tunable pore size, high specific surface area, great adsorption capacity, and light weight. The present paper reviewed the preparation techniques of OPP materials like breath figures, hard template, and soft template. Finally, the applications of OPP materials in the field of separation, sensors, and biomedicine are introduced, respectively. - Highlights: • Breath figures involve polymer casting under moist ambience. • Hard template employs monodisperse colloidal spheres as a template. • Soft template utilizes the etched block in copolymers as template

[en] Total laryngectomy was recommended to be the main surgical method for patients with laryngeal carcinoma for the purpose of radical cure in the past. Recently, partial laryngectomy with larynx reconstruction has been emphasized to preserve phonation and swallowing function, to avoid tracheostoma and to improve the patients' long-term quality-of-life, with no increase of recurrence rate. The key points to achieve this are selection of proper patients and complete excision of tumors in the surgical procedure. Imaging is important in the pre-operative evaluation of laryngeal carcinoma. It can provide essential information for tumor staging and treatment planning. Moreover, it is of great value in the postoperative follow up process as well as the evaluation of radiotherapy effectiveness. (authors)

[en] In this paper, the effects of residual charges on nanofiber alignment in a gap method are studied and presented. The gap method was presented by Li and Xia (2003 Nano Lett. 3 1167); in it, a gap is introduced into a traditional collector. Due to the non-perfect conductivity of electrospun nanofibers, they carry residual charges after deposition across the gap. These residual charges will interact with the charges carried by the upcoming jet/fiber, that will also deposit across the gap. The effects of these charge interactions on nanofiber alignment were studied numerically at various gap sizes. Results showed that alignments of nanofibers improve substantially with the gap size increasing from 3 to 8 mm. Numerical studies on the effect of residual charges in already deposited nanofibers on the alignment of nanofibers deposited afterwards were also conducted. Studies showed that the residual charges result in worse alignment, with a 10%-25% decrease in orientation parameters

[en] We perform a first-principles computational tensile test (FPCTT) on a ZnO single crystal based on density functional theory to systematically investigate structural transitions, mechanical, and intrinsic bonding properties in the three representative directions, [211-bar0], [0001], and [011-bar0]. Stress as a function of tensile strain shows that the ideal tensile strengths in the three directions are 16.2 GPa, 22.4 GPa, and 19.0 GPa, corresponding to strains of 0.20, 0.16, and 0.16, respectively. The [0001] is the strongest direction due to the strongest bonding between the most closely packed Zn and O(0001) layers. We demonstrate that different structures in these three directions lead to different structural transitions, i.e. from a wurtzite (WZ) to a body-centered tetragonal (BCT) structure for [211-bar0], to a graphite-like (GP-like) structure for [0001], and to a quasi-hexagonal (quasi-HX) structure for [011-bar0], respectively. Bond length and charge density evolution under tension indicate the occurrence of bond formation and disassociation during these structure transitions. New O-Zn bonds form in the WZ → BCT and WZ → quasi-HX transitions, and the original O-Zn bonds break in the WZ → GP-like transition.

[en] We have measured the thermal conductivity in the ab-plane (κ_ab) as well as the c-axis (κ_c) of a series of underdoped La_2-xSr_xCuO₄ (LSCO) single crystals grown by the travelling-solvent floating-zone (TSFZ) method. It was found that temperature dependence of thermal conductivity exhibits an interesting feature: there exists a steplike drop of thermal conductivity below ∼10 K in both κ_ab(T) and κ_c(T), and this drop in thermal conductivity occurs at lower temperature with lower Sr concentration. Furthermore, it is found that the magnitude of this drop at x = 0.11 and 0.125 is larger than at other doping levels. We suspect that this phenomenon is due to an LTO (low-temperature orthorhombic) to short-range (local) or dynamical LTT-like (low-temperature tetragonal) structure transition