Search

In this article, grid interactive photovoltaic (PV) system is designed for an electric vehicle (EV) charging application, and the stability of the system is analyzed. The small signal model for the system is derived by averaging and linearizing the state space equations, and the condition for stable operation of PV-integrated charger system is identified from the transfer functions. The proposed charger system implements a coordinated control between the converters to maintain a power balance between the sources and load. System stability is examined using root-locus plots and in addition, the controller is designed to improve the overall stability and reliability of the system. The proposed method provides a general framework for modeling EV charging systems which also details the importance of deriving the model with multiple energy sources. Further, proposed topology has bidirectional capability, which transfers excess PV power to the grid during off-charging hours. The efficacy of the proposed method is verified using the MATLAB Simulink environment for the different scenarios, i.e., variation in the irradiation and disturbances in the grid voltage. The experimental study is conducted on a 1.5-kW laboratory prototype using a low-cost digital signal processing controller (launchpad TMS320F28027F) and the measured results authenticate the simulation findings.

The slip casting of ceramics uses synthetically prepared water-soluble polymers and polymer emulsions as binder to achieve adequate yield stress of the consolidated body and high green strength. Substitution of synthetically prepared binders with a naturally renewable one is highly recommended for environmental friendliness and sustainability. Herein, slip casting of aqueous alumina slurries using natural rubber latex (NRL) binder is studied for the first time. Slurries of high alumina loading (40–55 vol%) at rubber concentrations in the range of 2–8 wt% obtained by mixing a concentrated aqueous alumina powder dispersion and a concentrated NRL exhibit viscosity and yield stress suitable for slip casting. The thickness of the body produced in 1 h from the slurries containing the NRL binder by slip casting in a plaster of Paris mold is three times higher than that produced from a slurry prepared using 2 wt% polyvinyl alcohol (PVA) binder. The slip-cast green bodies after annealing at 200 °C show high strength (3–9.68 MPa) due to cross-linking of rubber. Sintered ceramics prepared from the slip-cast bodies exhibit ~ 97% theoretical density (T.D) with an average grain size of 1.8 μm. NRL binder-based slip casting is capable of producing sintered alumina crucibles of wall thickness as low as 1.2 mm. NRL can be an eco-friendly and sustainable candidate binder for the slip casting of ceramic materials.

This study presents a nonlinear controller with a wind speed estimator for a variable speed wind turbine at below-rated wind speed. A nonlinear controller is designed to address the rapid variations in wind and uncertainties in the wind system. The objective of nonlinear controller is to maximize the energy that can be extracted from wind with a reduction on mechanical loads. The synergetic and terminal synergetic controllers are proposed for improving energy capture and load mitigation. Also, the stability of the controllers is analysed by Lyapunov stability. The proposed controllers were validated using the FAST (Fatigue, aerodynamics, structures and turbulence) numerical model. Finally, a comparative study has been made between the controllers for different wind speed profiles.

ABSTRACTIn this study, aluminosilicate fiber-embedded SiBOC matrix composite foams are realised by a simple, cost-effective and easily scalable method. Aluminosilicate wool is transformed into a compressible preform using polyvinyl alcohol as a binder. The preforms are impregnated with methylvinylborosiloxane (MVBS), followed by heat treatment at 1400°C in an inert atmosphere. The composite foam’s density, compressive strength and thermal conductivity are modulated in the ranges 0.71–0.46 g/cc, 0.79–0.39 MPa and 0.21–0.13 Wm−1K−1, respectively, by varying MVBS concentration from 29 to 54 wt.%. While the incorporation of aluminosilicate fibers was observed to lower the thermal conductivity of the composite foams, it did not contribute to their compressive strength. Exposure of the foams to air at 1300°C for 90 min didn’t change their density, while it increased the compressive strength by up to 46% due to improved fiber-matrix adhesion and rounding of cracks.

A simple urea crystal templating method is reported for the preparation of SiBOC ceramic foams, with rectangular rod-like pores, from methylvinylborosiloxane (MVBS) preceramic polymer solution. Pastes of urea crystals in concentrated MVBS solution were filled in open rectangular mold and set by cross-linking of MVBS using ethylenediamine (EDA) at room temperature. The cross-linking is due to the formation of adduct between electron-deficient boron in the polymer backbone and lone pair of electrons in amino groups of EDA. The gelation time of 60 wt.% MVBS solution in ethanol is modulated in the range of 240 to 3.25 h using EDA concentration in the range 0.33 to 10 wt.%. The gelled body is water-washed to leach out urea, followed by inert heat treatment at 1500 °C to produce SiBOC foam. The SiBOC ceramic foams of density 0.739 to 0.215 g cm−3, compressive strength 2.75 to 0.207 MPa, and thermal conductivity 0.262 to 0.073 W m−1K−1were achieved with urea concentrations of 50 to 88 vol.%. SEM micrographs show rectangular rod-like pores resulting from the urea particle template, which increases with an increase in urea concentration. XRD and TEM confirm SiBOC as amorphous, with the presence of a few nanocrystals of β-SiC and turbostratic carbon layers. The low thermal conductivity, excellent oxidation resistance, and reasonably high compressive strength make the prepared foams suitable candidate for high temperature thermal protection in aerospace.

Under partial shading conditions, photovoltaic (PV) systems exhibit multiple peaks in their power-voltage ($\mathbf{P-V}$) characteristics. It is essential to extract maximum energy from the PV system. The global maximum power point tracking (GMPPT) algorithms presented in the literature, track the global peak using different methods. It is imperative to have minimal convergence time for GMPPT process. This paper proposes a novel algorithm to track the global peak using voltage and current perturbation. The new GMPPT algorithm operates in a current perturbation or voltage perturbation mode, based on the value of a control variable. In either mode, the proposed technique generates reference current or reference voltage, for navigating the operating point to GMPP location. The proposed algorithm is compared with two GMPPT algorithms, namely, modified maximum power trapezium (M-MPT) and high-performance GMPPT algorithms. The simulation studies are performed in MATLAB and is validated using a laboratory prototype, with dSPACE 1202 MicroLabBox controller for implementing GMPPT methods. Simulation and experimental results show that the new technique exhibits superior performance in terms of tracking time. Also, the energy efficiency is improved by 40% while using the proposed GMPPT algorithm for the irradiance profiles considered in this paper compared to the other two techniques.

In this paper, a photovoltaic (PV) fed boost inverter-based permanent-magnet synchronous motor (PMSM)-driven water-pumping system for stand-alone applications is proposed. The proposed system comprises PV panel, six switches, three inductors (L), three capacitors (C) and a water pump. In this work, the boost inverter is designed with a gain of two and thereby the direct current input required to run the motor is considerably reduced. Hence, the size of the system is reduced. The voltage gain factor depends upon the placement of the Land Ccomponents and their values. The speed reference is generated using a perturb and observe maximum power point tracking algorithm. Vector control is employed to control a boost inverter-fed PMSM drive. The proposed system is simulated using a MATLAB®/Simulink® environment and experimental validation is performed on a PMSM laboratory prototype using a field programmable gate array controller. The simulation and experimental results demonstrate the effectiveness of the proposed system.A stand-alone water pumping system powered by photovoltaic power is designed and tested. The proposed system is verified through numerical simulation and with a laboratory prototype. The simulation and experimental results demonstrate the effectiveness of the proposed system.Graphical Abstract

Preparation of advanced functional materials from agricultural waste by eco-friendly processing route is inevitable for sustainable development. This work demonstrates the development of carbon/silica (C/SiO2) and carbon/silicon carbide (C/SiC) composite foam monoliths of low thermal conductivity, high EMI shielding performance and reasonable compressive strength from rice husk. The C/SiO2and C/SiC composite foams are obtained by carbonization and subsequent carbothermal reduction, respectively, of rice husk–sucrose composites consolidated by filter-pressing rice husk powder dispersed in sucrose solutions of various concentrations (300–600 g L−1). The amorphous nature of silica in C/SiO2and the presence of β-SiC in C/SiC are evidenced from XRD and TEM analysis. The compressive strength and thermal conductivity are depending on the foam density which is tailored by sucrose solution concentration. The compressive strength in the ranges of 0.32–1.67 and 0.19–1.19 MPa are observed for C/SiO2and C/SiC foams, respectively, with density in the ranges of 0.26–0.37 and 0.18–0.29 g cm−3. The C/SiO2and C/SiC exhibited thermal conductivity in the ranges of 0.150–0.205 W m−1K−1and 0.165–0.431 W m−1K−1, respectively. The C/SiO2and C/SiC composite foams show absorption dominated EMI shielding effectiveness in the ranges of 18–38.5 dB and 20–43.7 dB, respectively. The inherent pore channels and corrugated surface structure in rice husk, electrically conducting carbon and dielectric SiO2and SiC contribute to the total EMI shielding.

• Conversion of biomass, medical-grade cotton and sucrose, into carbon foams by filter-pressing. • Foams exhibit density in the range of 0.06 to 0.31 g cm−3. • Foams possess reasonable compressive strength in the range 5 kPa to 1.4 MPa. • Foams possess partial compressibility. • Low thermal conductivity (0.069 to 0.185 W m −1K−1) and good flame resistance. • carbon composite foams are amenable to machining using conventional machines and tools. • CCFs materials showed good electrical and EMI shielding properties. • The rigid CCFs showed shielding effectiveness in the ranges of 21.5 to 38.9 dB with adsorption dominant shielding properties. Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization. The compressive strength (5 kPa to 1.4 MPa) and thermal conductivity (0.069 to 0.185 W m −1 K −1) depend on the foam density (0.06 to 0.31 g cm−3) which is modulated by varying the sucrose solutions concentration (100 to 700 g L −1). Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L −1. The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre- to- fibre bonding area at higher sucrose concentration results in rigid foam. The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity. The carbon composite foams prepared at a sucrose solution concentration of 500 g L −1 and above are amenable to machining using conventional machines and tools. The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 dB and 108–138 dB cm3 g −1, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The Mitrofanoff procedure is a versatile technique that is successfully used in achieving continent urinary diversion for a wide variety of urological conditions. Appendix and usable segment of ureter [...]

Grid integration of distributed energy resources has become a technical challenge in the distribution network operation due to the intermittent nature of renewable energy sources and their impact on grid voltage stability. Thus, a dynamic voltage restorer (DVR) is installed in the distribution network system to reduce such grid voltage impact on sensitive loads. In this article, a pseudo-derivative-feedback (PDF)-based voltage controller is implemented for the effective operation of DVR under voltage disturbances. Response of DVR primarily depends upon its controller action. This article addresses the issues in conventional P and PI multiloop controller with and without feedforward path then proposes PDF control strategy for DVR. Using the proposed controller, dynamic performance of DVR is improved. The efficacy of the proposed controller is illustrated by a comparative study with conventional P and PI controller using time response and relative stability analysis. Finally, PSCAD simulation studies for a 10 kV medium voltage DVR and experimental results using a low voltage laboratory prototype DVR are presented to prove the robustness of proposed controller for DVR under symmetric and asymmetric voltage sags.

Oxide dispersion strengthening is an effective method to improve the high-temperature mechanical properties of the alloys in which various reinforcements are added in the alloy matrix by mechanical milling and consolidating the mixture by different techniques like hot pressing, hot isostatic pressing and spark plasma sintering. This work presents the development of IN 718 ODS alloy by dispersing yttria in IN 718, which has improved mechanical properties at high temperatures. Yttria powder was added to IN 718 alloy powder in different weight fractions of 0.25, 0.5 and 1% and mechanically milled. The composite powders were consolidated by hot pressing and hot isostatic pressing (HIP). A small fraction of isolated porosities in the matrix was observed in hot-pressed samples which caused degradation of the mechanical properties. Percentage of porosities increased with the increase in yttria content. The hot-pressed samples were HIPed to heal the porosities. 0.5 wt% yttria-dispersed Inconel 718 hot-pressed compact exhibited better properties at 850 °C and showed 50 MPa improvement in ultimate compressive strength compared to Inconel 718 alloy.

Psychosis commonly develops in adolescence or early adulthood. Youths at clinical high risk (CHR) for psychosis exhibit similar, subtle symptoms to those with schizophrenia (SZ). Malfunctioning neurotransmitter systems, such as glutamate, are implicated in the disease progression of psychosis. Yet, in vivoimaging techniques for measuring glutamate across the cortex are limited. Here, we use a novel 7 Tesla MRI glutamate imaging technique (GluCEST) to estimate changes in glutamate levels across cortical and subcortical regions in young healthy individuals and ones on the psychosis spectrum. Individuals on the psychosis spectrum (PS; n=19) and healthy young individuals (HC; n=17) underwent MRI imaging at 3 and 7 T. At 7 T, a single slice GluCEST technique was used to estimate in vivoglutamate. GluCEST contrast was compared within and across the subcortex, frontal, parietal and occipital lobes. Subcortical (χ2(1)=4.65, P=0.031) and lobular (χ2(1)=5.17, P=0.023) GluCEST contrast levels were lower in PS compared with HC. Abnormal GluCEST contrast levels were evident in both CHR (n=14) and SZ (n=5) subjects, and correlated differentially, across regions, with clinical symptoms. Our findings describe a pattern of abnormal brain neurochemistry early in the course of psychosis. Specifically, CHR and young SZ exhibit diffuse abnormalities in GluCEST contrast attributable to a major contribution from glutamate. We suggest that neurochemical profiles of GluCEST contrast across cortex and subcortex may be considered markers of early psychosis. GluCEST methodology thus shows promise to further elucidate the progression of the psychosis disease state.

AbstractThe present study was conducted to investigate the genetic diversity and affinities of four South Indian tribal populations namely, Malaikuravan, Malasar, Palliyan and Kattunaikkan. DNA samples from 184 unrelated individuals belonging to four tribal populations were analyzed for nine human-specific insertion and deletion polymorphic loci. The results indicate that all the studied biallelic loci are highly polymorphic in terms of allele frequencies and average heterozygosities (HT= 0.49) in all the study populations. The genomic diversity (GST) of the four tribal populations was quite low (2.4%). The neighbor joining tree and centroid analysis showed that the four tribal populations under consideration are equally distant from other Indian tribal and world populations. The results reveal that the study populations have received moderate gene flow compared to other populations.

The present work focuses on the utilization of biowaste material for a sustainable environment. In order to support the concept of ‘value-added product from waste’, Eggshell waste, which is a rich source of calcium is considered as a sustainable and renewable precursor for the synthesis of porous hydroxyapatite. This study introduces a novel, green and facile method for the synthesis of highly porous nano hydroxyapatite (nHA) and its magnetic composite aerogels (SPIONS@nHA) by freeze-drying technology. The synthesized materials have undergone through characterization. Perchlorate removal efficiency of the materials was investigated for the first time and the factors that influence the perchlorate adsorption capacity were explored and optimized. The magnetic composite of nHA showed an excellent separation in the presence of an external magnetic field from contaminated water after adsorption. XPS analysis and zeta potential measurements showed that the main driving force behind the adsorption of perchlorate is ion exchange and ion-pair formation/electrostatic interaction. Very fast removal kinetics was observed and the experimental maximum adsorption capacity for nHA and SPIONS@nHA were 148.4 and 305.8 mgg−1respectively. It is commendable that other commonly existing ions exhibited no remarkable effect on the adsorption performance, indicating SPIONS@nHA has an immense application potential. The adsorption process was found to follow by pseudo-second-order and intra-particle diffusion kinetic models. A novel method for the regeneration of perchlorate loaded adsorbent using phosphate buffer was also studied in this paper. The regeneration performance of spent magnetic adsorbent showed greater than 90% recovery on the adsorption capacity even after fifth cycle, revealing the stability, reusability and economic efficiency of the adsorbent. Thus, magnetic nanocomposite of the biogenic hydroxyapaptite can be exploited as a sustainable and efficacious material for the abolishment of perchlorate from aqueous media at near neutral pH.

AbstractBackground: Autonomic dysreflexia (AD) is a frequent, serious acute syndrome that occurs in patients with spinal cord lesions at level T6 and above. The syndrome is caused by massive sympathetic discharge that is triggered by a noxious stimulus below the level of the spinal cord lesion. Pheochromocytomas are rare tumors that present with symptoms similar to AD.Methods: Case Report.Findings: A 50-year-old man with C7 American Spinal Injury Association scale A tetraplegia presented with episodes of severe headaches and paroxysmal hypertension. He was diagnosed with AD. Despite resolving bladder and bowel problems, he continued to have hypertensive episodes. A CT scan of the abdomen revealed a heterogeneous left adrenal mass. Further workup revealed significantly elevated serum and 24-hour urinary catecholamines. Clonidine failed to fully suppress the markedly elevated concentrations of serum catecholamines. These biochemical findings were consistent with the diagnosis of pheochromocytoma. Prior to surgery, the patient was treated with a-receptor blockers and volume expansion with intravenous fluids. A left adrenalectomy was performed. The surgical specimen revealed that the adrenal gland was expanded by a spherical mass. The pathologic report was benign pheochromocytoma of the left adrenal gland.Conclusion: Clinical symptoms and hypertensive episodes resolved following adrenalectomy. To our knowledge, this is the first reported case of a pheochromocytoma in an individual with spinal cord injury.

Purpose:: The aim of this study was to examine the authors' experience with patients who have floating sternum after correction of pectus excavatum via the classical Ravitch procedure. A floating sternum is defined as a sternum in which the only attachment to the chest wall is its superior (cranial) border, and in which the body is secured only by the manubrium and whatever lateral and inferior fibrous bands are present. Typically, a floating sternum is caused by either extensive resection of the costal cartilages and perichondrium during correction of pectus excavatum or failure of proper regrowth of these cartilages. Methods:: The authors retrospectively assessed the charts of all patients diagnosed with a floating sternum noting age at original correction of pectus excavatum, time from original correction of pectus excavatum to diagnosis of floating sternum, age at correction of floating sternum, complaints before stabilization of the sternum, methods of repair, and postoperative complications. Results:: Between July 1993 and June 1999, floating sternum was diagnosed in 7 patients. The mean age of patients who underwent operative correction of a floating sternum was 28.9 years (range, 16 to 42 years). The mean time interval between original correction of pectus excavatum, or ''redo,'' and diagnosis of a floating sternum was 9.9 years (range, 2 to 20 years). Complaints before correction of the floating sternum included sternal pain and instability, exercise intolerance, and difficulty breathing. Operative repair consisted of mobilizing the lateral and inferior edges of the sternum, detaching the fibrous perichondrium, performing anterior sternal osteotomies, and finally supporting the sternum with substernal Adkins struts. All 7 patients had successful stabilization of the sternum. Two of 7 patients underwent 2 procedures to successfully stabilize the sternum. One patient has Adkins struts still in place because of hematopoetic malignancy. Six of 7 patients are now without symptoms. Conclusions:: A floating sternum is a morbid phenomenon that may manifest many years after the original procedure. It can cause significant sternal pain, chest wall instability, and respiratory dysfunction, which are the hallmark indications for correction. Repair of a floating sternum can be accomplished successfully.

Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.

In this paper, we report a comparison of the thermal decomposition pathways of ultrathin oxide layers, formed on Ge(100) and Si(100) surfaces, as revealed by photoemission studies, employing synchrotron radiation. The oxide layer, in both the cases, consists of a mixture of, mainly, monoxide and dioxide species. On annealing, both the oxides undergo thermal decomposition and the desorbing species is the corresponding monoxide. However, we find that their decomposition pathways are entirely different. On annealing the Ge oxide layer, the GeO2species transforms to GeO on the surface and finally desorbs from the surface at ∼425°C. In contrast, annealing results in the transformation of SiO to SiO2up to a temperature, lower than the desorption temperature (∼760°C). At higher temperatures, SiO2possibly transforms back to SiO and subsequently desorbs. These phenomena may be related to the interface properties, since the thermodynamic properties of individual oxides predict an opposite trend in their thermal stability.

Purpose: This study reports the authors' cumulative experience with pediatric living related orthotopic liver transplantation. Methods: The charts of all patients who received living-related liver transplantation to study complications of transplant surgery, immunosuppression, rejection, and overall survival rate were reviewed retrospectively. Results: Between November 1992 and October 1988, 30 children underwent living-related liver transplantation. Patients were between the ages of 3 months and 7 years of age (mean, 28 months). All received left lateral segmental living-related transplants. At the time of transplant, 14 of 30 patients were listed as United Network of Organ Sharing (UNOS) status 3, 11 were listed as UNOS status 2B, and 5 were listed as UNOS status 1. Indications for transplant included biliary atresia (n = 21), @a-1-antitrypsin deficiency (n = 2), hepatitis C (n = 2), giant cell hepatitis (n = 2), hepatoblastoma (n = 1), valproic acid toxicity (n = 1), and hemangioendothelioma (n = 1). All donors were parents except for one uncle. There were no major donor complications. Minor complications included wound infection (n = 4), ventral hernia (n = 2), postoperative gastric dysmotility (n = 2), and 1 case of central line-related pneumothorax (n = 1). All but 4 recipients received primary tacrolimus immunosuppressive regimens, and the other, 4 underwent conversion from cyclosporine. Initial tacrolimus therapy was begun at 0.15 mg/kg/dose PO/NG every 12 hours. Concomitant immunosuppression included methylprednisolone and mycophenolate mofetil. Fifty-three percent of patients experienced at least 1 episode of rejection, and 27% experienced multiple episodes. Immediate postoperative complications included primary nonfunction (n = 2), vascular thrombosis (n = 3), biliary leaks (n = 3), and infections (n = 17). Two patients (n = 2) required retransplantation. Complications of immunosuppressive therapy included persistent systemic hypertension (n = 6), renal tubular acidosis (n = 3), short-term hyperglycemia (n = 2), neurotoxicity (n = 2), nephrotoxicity (n = 2), food allergies (n = 8), and posttransplant lymphoproliferative disease (n = 4). All patients with PTLD were treated with immunosuppression reduction or withdrawal. Two of 4 had disease progression requiring chemotherapy. The majority of complications were treated with dose adjustments. There were 4 early deaths (13%): 1 of primary nonfunction, 2 of sepsis, and 1 of arrhythmia and renal failure. There was 1 late death of recurrent disease. Twenty-five patients (83%) are alive at 3 months to 6 years post-transplant. Conclusion: Living-related orthotopic liver transplantation is an effective intervention for pediatric patients with end-stage disease.

2,4-Dinitrodiphenylamine (DNDPA) has been studied as regards its crystal structure and thermal decomposition characteristics using X-ray diffraction (XRD), simultaneous thermal analysis, ultraviolet and visible spectroscopy, infrared spectroscopy, hot-stage microscopy and high performance liquid chromatography (HPLC). The elementary cell parameters obtained from the XRD pattern are a=17.002 Å, b=17.002 Å, c=20.400 Å. The crystal structure belongs to the hexagonal system with c/a ratio 1.1999. IR spectra of 2,4-DNDPA have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal thermogravimetry (TG) and HPLC. The best linearity with a correlation coefficient of 0.994 was obtained for the two-dimensional diffusion controlled equation in TG. Activation energy was found to be 83.0 kJ/mol and log A (in s⁻¹)=6.0 from isothermal TG. The rupture of the C–NH bond followed by the C–NO2 bond constitutes the primary step in the thermolysis and the decomposition is free-radical assisted.

In this paper, we have briefly summarized our activity in the area of chemical bond manipulation for the integration of nanostructures on a full wafer scale. Chemical bond manipulation involves a judicious combination of surface phenomena: reactions or diffusion, and growth process such as molecular beam epitaxy (MBE). Here, we present our results on oxidation, metallization and nitridation and their role in the formation of nanostructures. We find that oxygen changes the bonding partner from Ge to Si and this phenomenon can be controlled by controlling the annealing temperature. We have employed this phenomenon for the fabrication of novel, multiperiod Si/SiO2/Ge layered structure which exhibits interesting light emitting properties. Further, by making use of selective diffusion of cobalt atoms through Ge layers it is possible to incorporate metallic features into Ge quantum dots. Moreover, it is possible to fabricate Si nanopillars through high temperature reaction of nitric oxide. NO molecules dissociate on the surface and nitrogen atoms thus produced form nitride islands. These islands act as protective masks for the etching of Si by the oxygen atoms, through the desorption of SiO species. Occurrence of these two simultaneous processes result in the formation of nanometre-sized Si pillars capped by silicon nitride. All these results emphasize the fact that we can extend information obtained through traditional surface science experiments for the fabrication of novel structures on a full wafer scale.

Abstract: The adsorption of CO has been studied on the surface of a Cu50Zr50 metallic glass using X-ray and ultraviolet photoelectron spectroscopic techniques. CO dissociates on both these surfaces leading to the formation of graphitic and carbidic carbon species on the surface. However a reversal in intensity of the two species is observed on the metallic glass surface compared to that on the Zr metal surface. While Zr gets oxidised due to the oxygen produced as a result of the dissociation of CO, Cu remains unoxidised.

Abstract: A series of complexes of salicylic acid-thiourea-trioxane polymer andp-hydroxybenzoic acid-thiourea-trioxane polymer respectively were isolated and characterised by elemental analysis and infrared data. The antimicrobial activity of these complexes against various bacteria and fungi is studied, which indicates that in several cases, the complexes possess fairly highly anti-microbial activity. A probable mechanism for the toxic action of these complexes against various organisms is discussed. ir spectra of complexes are also discussed.

Interaction of Co with a Ge covered Si(111) surface is studied employing ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS), medium energy ion scattering spectroscopy (MEIS), cross sectional transmission electron microscopy (XTEM), low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). 2 ML of Co is deposited on a Si(111) surface, which is covered with ∼ 3 ML of Ge, both at room temperature. On annealing the sample at 460°C, Co diffuses through the Ge layer and reacts with the Si atoms underneath. This results in the formation of a buried CoSi 2 layer. XTEM pictures as well as the blocking dip pattern in MEIS suggest that the CoSi 2 formed at the interface between Si and Ge, is a B-type epitaxial. The Co layer undergoes agglomeration and forms Ge/CoSi 2 /Si dot structures and Ge/Si terraces. A mixture of 1 × 1 and 5 × 5 patterns originating, respectively, from Ge/CoSi 2 /Si and Ge/Si regions are observed in RHEED and LEED. The results open up a novel way of fabrication of buried epitaxial metallic layers and semiconductor/metal nanostructures.

A series of complexes of salicylic acid-thiourea-trioxane polymer andp-hydroxybenzoic acid-thiourea-trioxane polymer respectively were isolated and characterised by elemental analysis and infrared data. The antimicrobial activity of these complexes against various bacteria and fungi is studied, which indicates that in several cases, the complexes possess fairly highly anti-microbial activity. A probable mechanism for the toxic action of these complexes against various organisms is discussed. ir spectra of complexes are also discussed.

Abstract: Nitroaminoguanidine (NAG) has been investigated as regards its thermal decomposition characteristics using simultaneous thermal analysis, infrared spectroscopy, X-ray diffraction and polarising microscopy. XRD studies show thatNAG crystal belongs to the tetragonal system. The crystal structure parameters are found to be:a=17.063±0.005Å,b=17.063±0.005Å,c=5.155±0.005Å andc/a axial ratio=0.302. Under non-isothermal conditions,NAG decomposed apparently in one stage with a loss in weight of 80%. But the thermal decomposition ofNAG in the solid phase under isothermal conditions proceeded through three stages. Both the first and the second stages obeyed theA-E (Avrami Erofee'v) equation forn=1. The 3rd stage is too slow and kinetics has not been attempted. The rate parameters for the first and second stages have been evaluated. Gaseous decomposition products detected using the IR gas cell are NH3, NO2, HCN, N2O, CO and CO2. High temperature IR studies indicate preferential deamination reaction initially indicating breaking of N−NH2 and C−NH2 bonds leading to NH2 radical formation. Addition of diphenylamine, a known chain inhibitor, decelerated the thermal decomposition, supporting a radical chain reaction.

Adsorption of CO has been investigated on the surfaces of polycrystalline transition metals as well as alloys by employing electron energy loss spectroscopy (eels) and ultraviolet photoelectron spectroscopy (ups). CO adsorbs on polycrystalline transition metal surfaces with a multiplicity of sites, each being associated with a characteristic CO stretching frequency; the relative intensities vary with temperature as well as coverage. Whilst at low temperatures (80–120 K), low coordination sites are stabilized, the higher coordination sites are stabilized at higher temperatures (270–300 K). Adsorption on surfaces of polycrystalline alloys gives characteristic stretching frequencies due to the constituent metal sites. Alloying, however, causes a shift in the stretching frequencies, indicating the effect of the band structure on the nature of adsorption. The up spectra provide confirmatory evidence for the existence of separate metal sites in the alloys as well as for the high-temperature and low-temperature phases of adsorbed CO.

The adsorption of CO has been studied on the surface of a Cu50Zr50metallic glass using X-ray and ultraviolet photoelectron spectroscopic techniques. CO dissociates on both these surfaces leading to the formation of graphitic and carbidic carbon species on the surface. However a reversal in intensity of the two species is observed on the metallic glass surface compared to that on the Zr metal surface. While Zr gets oxidised due to the oxygen produced as a result of the dissociation of CO, Cu remains unoxidised.

The value of anorectal manometry as a diagnostic tool for Hirschsprung's disease (HD) was assessed in 50 children presenting with chronic constipation. Anorectal manometric studies and rectal biopsy were performed on all children. Biopsy specimens were stained with hematoxylin and eosin and serial sections were examined for ganglion cells. Forty-five children had concordant manometric and histologic results, 15 of whom were positive for HD and 30 negative. In five children, the results were discordant. Using histologic aganglionosis as the reference point for the final diagnosis of HD, the overall accuracy of anorectal manometry as a discriminative test was 90.0. The sensitivity, specificity, and positive and negative predictive values of manometric studies for the diagnosis of HD were 0.79, 0.97, 0.94, and 0.88, respectively. Factors responsible for the inaccuracies of manometric studies are discussed.

Suspensions of Mycobacterium leprae purified from the organs (mostly spleen) of experimentally-infected armadillos (Dasypus novemcinctus, Linn) decarboxylated 1-(14C) glutamic acid liberating 14CO2. The reaction was pyridoxal phosphate-dependent and was inhibited by hydroxylamine, suggesting that it is a true amino acid decarboxylase. Loss of the activity at higher temperatures indicated the enzymatic nature of the reaction. Excess substrate or substrate analogs inhibited the decarboxylase whereas a-ketoglutarate and glutarate stimulated it. The activity was four times higher at pH 4.5 than at pH 6.8, suggesting that the enzyme is of microbial origin and not derived form the host cells. Armadillo spleen did not decarboxylate the amino acid. The Km value of the enzyme in the organisms was similar to that in Escherichia coli. The results reported here show that glutamate decarboxylase (EC 4.1.1.15) is an inherent metabolic activity of M. leprae, and might explain its unusual neural affinity. Glutamic acid is the most abundant amino acid occurring in the nerve tissue.