Basic investigation of HfO2 based metal-insulator-metal diodes

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).     

Effect of simultaneous double doping in Ba and Ti sites on dielectric and ferroelectric properties of sol–gel synthesized nano-BaTiO<Subscript>3</Subscript>

Lead free (Ba_(1−3x)Nd_(2x))(Ti_(1−y)Zr_y)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 (T_c) 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 (P_s) and remanent polarisation (P_r). Behaviour of polarisation phenomena in these compounds showed interesting results with increasing temperature.     

Time-independent,high electron mobility in thin PC61BM films: Relevance to organic photovoltaics

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.     

Diacetyl—A growth and toxin inhibitor of Aspergilli

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.     

MULTIPLE REGRESSION AND COMMITTEE NEURAL NETWORK FORCE PREDICTION MODELS IN MILLING FRP

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.     

Interleukin-10 controls neutrophilic infiltration, hepatocyte proliferation, and liver fibrosis induced by carbon tetrachloride in mice

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.     

Modification of bone marrow radiosensensitivity by medicinal plant extracts

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.     

Immobilization of β-galactosidase onto polymeric supports

Poly(vinyl alcohol) cross-linked with para-formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β-galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant K_m and maximum reaction velocity V_m were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (E_a) and inactivation constant (K_i) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.     

Estimation of fuzzy memberships from histograms

Based on the conclusions drawn in the bijective transformation between possibility and probability, a method is proposed to estimate the fuzzy membership function for pattern recognition purposes. A rational function approximation to the probability density function is obtained from the histogram of a finite (and sometimes very small) number of samples. This function is normalized such that the highest ordinate is one. The parameters representing the rational function are used for classifying the pattern samples based on a max-min decision rule. The method is illustrated with examples.     

Anomaly of arch of atlas--a rare cause of symptomatic canal stenosis in children

Symptomatic canal stenosis at the level of atlas (C1) without atlantoaxial dislocation is thought to be very rare in children. Though common, anomalies of the arch of atlas are generally incidental findings in X-rays. High cord compression due to a narrow canal from a bifid posterior arch, or an absent posterior arch, is a very rare condition. We report 5 children with high cord compression from stenosis of C1 arch.