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51.
The percolation behavior of normal-state thermopower, resistivity, and superconductivity have been studied in YBa2Cu3O7-δ─Ag (YBCO─Ag) composite systems. The normal-state resistivity and thermopower show a percolation threshold at a Ag volume fraction ( V Ag) of 20% to 30%, whereas the superconducting network shows a threshold at a V Ag of ≅70% to 80%. The results obtained from this study show that the YBCO─Ag composite obtained from Ag2O and YBCO powders is uniformly distributed with Ag and YBCO remaining as separate phases without changing their characteristics. The measurements of thermopower indicate that the normal-state thermopower and phonon-drag thermopower are affected by the Ag addition. The stability of YBCO is increased when it is in composite form.  相似文献   
52.
The pantothenate biosynthetic pathway is essential for the persistent growth and virulence of Mycobacterium tuberculosis (Mtb) and one of the enzymes in the pathway, pantothenate synthetase (PS, EC: 6.3.2.1), encoded by the panC gene, has become an appropriate target for new therapeutics to treat tuberculosis. Herein, we report nanomolar thiazolidine inhibitors of Mtb PS developed by a rational inhibitor design approach. The thiazolidine compounds were discovered by using energy‐based pharmacophore modelling and subsequent in vitro screening, which resulted in compounds with a half maximal inhibitory concentration (IC50) value of (1.12±0.12) μM . These compounds were subsequently optimised by a combination of modelling and synthetic chemistry. Hit expansion of the lead by chemical synthesis led to an improved inhibitor with an IC50 value of 350 nM and an Mtb minimum inhibitory concentration (MIC) of 1.55 μM . Some of these compounds also showed good activity against dormant Mtb cells.  相似文献   
53.
Sulfur ion (S6+) was doped into the anatase TiO2 prepared by sol–gel method (SG-TiO2) using sulfur powder as a sulfur source (S-TiO2) and its photoreactivity was probed for the degradation of phenol under UV/solar light illumination. The S-TiO2 and SG-TiO2 were characterized by PXRD, UV–vis DRS, FTIR, SEM, XPS, BET and PL techniques. It was observed that S6+ ion was incorporated into the TiO2 crystal lattice at Ti4+ lattice site and the sulfur on the surface gets modified to 4SO2−SO42 due to the heat treatment under atmospheric conditions. The high photocatalytic activity of S-TiO2 compared to SG-TiO2 is attributed to the surface modification of sulfur as sulfate which plays a crucial role in trapping electrons. S-TiO2 shows significant increase in the surface area, reduced crystallite size, increased surface acidity, visible light absorption and prolonged lifetime of the photogenerated charge carriers. Hole scavengers like potassium iodide and tertiary butanol suggested the surface degradation mechanism rather than the bulk degradation pathway. Addition of oxidizing agents to the degradation reaction did not show any enhancement in the degradation rates since the presence of 4SO2−SO42 on the TiO2 surface itself acts as the efficient electron trapping centers. Both trapping and detrapping of the electron takes place more efficiently at 4SO2−SO42 centers. The enhanced activity of S-TiO2 is attributed to the synergistic effect between S6+ dopant with surface modified 4SO2−SO42.  相似文献   
54.
Very fast frequency response of metal-insulator-metal (MIM) diodes extends into the terahertz regime making them attractive as key elements as alternative to photovoltaic solar energy harvesting and ultrahigh speed wireless communication systems. The tunnelling phenomena, which is crucial for achieving high performance in these devices is extremely sensitive to the nanoscale structural and chemical quality of interface regions. Modern chemical deposition techniques like Pulsed Injected Metal-Organic Chemical Vapour Deposition (PICVD), Atomic Layer Deposition (ALD) and Atomic Vapour Deposition (AVD®) will be used for the extremely precise growth of thin HfO2 films on TiN bottom electrodes. However, different deposition techniques may give unpredictably different results in terms of film density, surface and interface property and consequently in physical properties of the device.In this work, the influence of deposition techniques on the charge transport characteristics of HfO2 MIM diodes was investigated by Conducting Atomic Force Microscopy (C-AFM) and X-ray Photoelectron Spectroscopy (XPS).  相似文献   
55.
Lead free (Ba(1−3x)Nd(2x))(Ti(1−y)Zry)O3 (x = 0, 0.025, y = 0, 0.025, 0.05) ceramics were prepared successfully using sol–gel method. The effect of Nd, Zr content on dielectric and polarisation properties of BaTiO3 were studied using dielectric and hysteresis measurements. SEM analysis proved that the particle size of compounds as prepared were in the order of 30–60 nm. The ferroelectric phase transition from tetragonal to cubic phase was observed around 130 °C for pure BaTiO3. With the addition of Nd (2.5 mol%) and increasing content of Zr (2.5 and 5 mol%), it was observed that transition temperature (Tc) shifts to lower temperatures (70–50 °C), but didn’t show any relaxor behaviour. Dielectric measurements showed an increase in the values at room temperature in all the doped samples. The synthesized ceramics exhibited typical P–E hysteresis loops at room temperature accompanied by saturation polarisation (Ps) and remanent polarisation (Pr). Behaviour of polarisation phenomena in these compounds showed interesting results with increasing temperature.  相似文献   
56.
Ultrafast optical probing of electric field by means of electroabsorption combined with conventional photocurrent measurements was employed to investigate the drift and mobility dynamics of photo-generated charge carriers in the pristine PC61BM film and in the blend with a merocyanine dye. Electrons passed a 40 nm thick PC61BM film within a few picoseconds with time-independent and weakly dispersive mobility. The electron mobility is 1 cm2/(V s) at 1 MV/cm and an estimate of the zero-field mobility yields 5 ⋅ 10−2 cm2/(V s). The initial electron mobility in the blend is of the order of 10−2 cm2/(V s) and decreases rapidly. We conclude that electron motion in PC61BM based organic bulk hetero-junction solar cells is limited by barriers between PC61BM domains rather than by intrinsic PC61BM properties.  相似文献   
57.
Diacetyl (2,3-butanedione) a food additive, was found to be very effective in inhibiting growth and toxin production of Aspergillus flavus, A. versicolor and A. ochraceus when grown on synthetic liquid media and on natural substrates of maize and maize flour. Total growth inhibition of A. flavus and A. versicolor was observed at 250 ppm when grown on liquid medium, whereas 3000–4000 ppm were required to inhibit growth on maize and maize flour. A. ochraceus required 3000 and 6000 ppm of diacetyl for complete inhibition of growth on liquid medium and solid substrates respectively, suggesting it was less sensitive to the compound.  相似文献   
58.
This work utilizes the mechanistic modeling approach for predicting cutting forces and simulating the milling process of fiber-reinforced polymers (FRP) with a straight cutting edge. Specific energy functions were developed by multiple regression analysis (MR) and committee neural network approximation (CN) of milling force data and a cutting model was developed based on these energies and the cutting geometry. It is shown that both MR and CN models are capable of predicting the cutting forces in milling of unidirectional and multidirectional composites. Model predictions were compared with experimental data and were found to be in good agreement over the entire range of fiber orientations from 0 to 180°. Furthermore, CN model predictions were found to greatly outperform MR model predictions.  相似文献   
59.
The role of the anti-inflammatory cytokine interleukin-10 (IL-10) was investigated in the mouse model of liver injury induced by carbon tetrachloride (CCl4). To address the role of endogenous IL-10 production, acute hepatitis was induced by CCl4 in C57Bl/6 IL-10 gene knock out (KO) and wild-type (WT) mice. After CCl4 challenge, serum and liver levels of tumor necrosis factor-alpha (TNF-) and serum levels of transforming growth factor-beta 1 (TGF-beta1) increased and were significantly higher in IL-10 KO mice, whereas IL-6 serum levels were only slightly increased compared with WT mice. At histological examination, the livers disclosed a significantly more prominent neutrophilic infiltration in IL-10 KO mice 12 and 24 hours after CCl4 injection. In contrast, hepatocyte necrosis, evaluated by histological examination and serum alanine aminotransferase levels, was only marginally affected. The proliferative response of hepatocytes, assessed by the proliferating cell nuclear-antigen labeling index, was significantly increased in IL-10 KO mice, compared with WT mice 48 hours after CCl4 injection. Finally, repeated CCl4 injections led to more liver fibrosis in IL-10 KO mice after 7 weeks. In conclusion, endogenous IL-10 marginally affects the hepatocyte necrosis although it controls the acute inflammatory burst induced by CCl4. During liver repair, it limits the proliferative response of hepatocytes and the development of fibrosis.  相似文献   
60.
Withaferin A (WA), a steroidal lactone, and Plumbagin (Pl), a naphthoquinone, from the roots of Withania somnifera and Plumbago rosea, respectively, have been shown to possess growth inhibitory and radiosensitizing effects on experimental mouse tumours. An aqueous extract of the leaves of Ocimum sanctum (OE) was found to protect mice against radiation lethality. Therefore, the radiomodifying effects of the above plant products on the bone marrow of the adult Swiss mouse was studied. Single doses of WA (30 mg kg-1) or Pl (5 mg kg-1) were injected intraperitoneally (ip) and OE (10 mg kg-1) was injected ip once daily for five consecutive days. Administration of extracts was followed by 2 Gy whole body gamma irradiation. Bone marrow stem cell survival was studied by an exogenous spleen colony unit (CFU-S) assay. The effects of WA and Pl were compared with that of cyclophosphamide (CP) and radioprotection by OE was compared with that of WR-2721 (WR). Radiation reduced the CFU-S to less than 50% of normal. WA, CP and Pl significantly enhanced this effect and reduced the CFU-S to almost the same extent (to < 20% of normal), although individually WA and Pl were less cytotoxic than CP. These results indicate that radiosensitization by WA and Pl is not tumour specific. OE significantly increased CFU-S compared with radiotherapy (RT) alone. OE+RT gave a higher stem cell survival (p < 0.05) than that produced by WR+RT. While WR alone had a toxic effect, OE treatment showed no such effect, suggesting that the latter may have an advantage over WR in clinical application.  相似文献   
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