bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Expansion of GaN at Low Temperatures - a Comparison of Bulk and Homo- and Heteroepitaxial Layers
Authors: Kirchner Verena , Heinke Heidrun , Einfeldt Sven , Hommel Detlef , Domagala Jaroslaw Z. , Leszczynski Michal 
Published: September 2012

AbstractThe thermal expansion of different GaN samples is studied by high-resolution Xray diffraction within the temperature range of 10 to 600 K. GaN bulk crystals, a homoepitaxial layer and different heteroepitaxial layers grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were investigated. Below 100 K the thermal expansion coefficients (TEC) were found to be nearly zero which has to be taken into account when estimating the thermal strain of GaN layers in optical experiments commonly performed at low temperatures. The homoepitaxial layer and the underlying GaN substrate with a lattice mismatch of –6×10−4 showed identical thermal expansion. The comparison between the temperature behavior of lattice parameters of heteroepitaxial layers and bulk GaN points to a superposition of thermally induced biaxial strain and compressive hydrostatic strain.
Physical Properties of Silicon Doped Hetero-Epitaxial MOCVD Grown GaN: Influence of Doping Level and Stress
Authors: Hageman P.R. , Kirilyuk V. , Zauner A.R.A. , Bauhuis G.J. , Larsen P.K. 
Published: September 2012

AbstractSilicon doped layers GaN were grown with MOCVD on sapphire substrates using silane as silicon precursor. The influence of the silicon doping concentration on the physical and optical properties is investigated. A linear relationship is found between the silane-input molfraction and the free carrier concentration in the GaN layers. The morphology of the samples is drastically changed at high silicon concentrations. Photoluminescence was used to probe bandgap variations as function of the silicon concentration. Increasing of the doping concentration led to a continuous shift of the exciton related PL to lower energies, while the intensity of the UV emission was found to increase up to a carrier concentration of n=2.5×1018 cm−3.
Structural and Electronic Properties of Line Defects in GaN
Authors: Elsner Joachim , Blumenau Alexander Th. , Frauenheim Thomas , Jones Robert , Heggie Malcolm I. 
Published: September 2012

AbstractWe present density-functional theory based studies for several types of line defects in both hexagonal and cubic GaN. {10-10} type surfaces play an important role in hexagonal GaN since similar configurations occur at open-core screw dislocations and nanopipes as well as at the core of threading edge dislocations. Except for full-core screw dislocations which possess heavily strained bonds all investigated stoichiometric extended defects in hexagonal GaN do not induce deep acceptor states in the band-gap and thus cannot be responsible for the yellow luminescence. However, electrically active point defects in particular gallium vacancies and oxygen related defect complexes are found to be trapped at the stress field of the dislocations. Preliminary calculations for cubic GaN find the ideal stoichiometric 60°-dislocations to be electrically active. As in hexagonal material, vacancies and impurities like oxygen are likely to be trapped at the dislocation core.
Simulation of H Behavior in p-GaN(Mg) at Elevated Temperatures
Authors: Myers S. M. , Wright A. F. , Petersen G. A. , Seager C. H. , Crawford M. H. , Wampler W. R. , Han J. 
Published: September 2012

AbstractThe behavior of H in p-GaN(Mg) at temperatures >400°C is modeled by using energies and vibration frequencies from density-functional theory to parameterize transport and reaction equations. Predictions agree semiquantitatively with experiment for the solubility, uptake, and release of the H when account is taken of a surface barrier.
Optical Activation Behavior of Ion Implanted Acceptor Species in GaN
Authors: Skromme B.J. , Martinez G.L. 
Published: September 2012

AbstractIon implantation is used to investigate the spectroscopic properties of Mg, Be, and C acceptors in GaN. Activation of these species is studied using low temperature photoluminescence (PL). Low dose implants into high quality undoped hydride vapor phase epitaxial (HVPE) material are used in conjunction with high temperature (1300 °C) rapid thermal anneals to obtain high quality spectra. Dramatic, dose-dependent evidence of Mg acceptor activation is observed without any co-implants, including a strong, sharp neutral Mg acceptor-bound exciton and strong donor-acceptor pair peaks. Variable temperature measurements reveal a band-to-acceptor transition, whose energy yields an optical binding energy of 224 meV. Be and C implants yield only slight evidence of shallow acceptor-related features and produce dose-correlated 2.2 eV PL, attributed to residual implantation damage. Their poor optical activation is tentatively attributed to insufficient vacancy production by these lighter ions. Clear evidence is obtained for donor-Zn acceptor pair and acceptor-bound exciton peaks in Zn-doped HVPE material.
Electrochemical Properties of Solution Synthesized Undoped and Aluminum Doped Lithium Manganate Thin Films
Authors: Das S.R. , Karan N.K. , Majumder S.B. , Katiyar R.S. 
Published: September 2012

AbstractThe spinel structured lithium manganate (LMO) is a promising cathode material for lithium ion rechargeable micro-batteries due to its higher energy density, environmentally benign nature, and low cost. To date, self-discharge and capacity fading (4 and 3V range), especially at elevated temperatures, still remains major research issues of LMO based cathodes. In the present work we have successfully synthesized lithium manganate thin films by a cost effective solution growth technique. These films exhibited excellent reversible lithium ion intercalation behavior with a discharge capacity of about 55.08:Ahcm−2:m−1 at a load of 20:Acm−2. The Li+ diffusivity was found to increase by substituting a part of manganese with aluminum (Al) in LMO lattice. Al substituted LMO films exhibited better cycleability as compared to the undoped LMO films. Further studies are in progress to investigate the effect of Al substitution on the cycleability of the films.
X-ray Absorption Spectroscopy Investigation of the Sub-Nanoscale Strain in Thin-Film Lithium Ion Battery Cathodes
Authors: Alamgir Faisal M. , Vansluytman Jason , Carter Daniel , Whitacre Jay , Kao Chi-Chang , Greenbaum Steve , Denboer Marten 
Published: September 2012

AbstractLiCoO2 and LiNiO2, two important cathode materials for Li-ion batteries, were studied in their respective bulk and thin-film form. X-ray absorption spectroscopy (XAS) has been used to probe the local atomic structure and structural defects in the thin-film and bulk cathodes. Results comparing Li(Co,Ni)O2 in the bulk and thin-film forms suggests a correlation between intrinsic stress and local strain in the thin-film. This local strain is manifested by a collapse of the six-fold rotational symmetry within the metal-metal layer of the Li(Co,Ni)O2 system into a two fold one. The relationship between annealing conditions and the resulting local strain in these films is examined.
Electrochemical Properties and Microstructure of Tin Base Thin Film Electrode for Lithium Secondary Batteries
Authors: Choi Wanuk , Lee Jeong Yong 
Published: September 2012

AbstractCu/Sn alloy electrode, as an anode for Li ion secondary batteries, was fabricated by annealing of Sn thin film electroplated on copper thin foil. The structure of Cu/Sn alloy electrode was determined using XRD, SEM and TEM. The thin film was consisted of Cu6Sn5, Cu3Sn and so on, the major component was a few ten nanometer sized Cu6Sn5 grains and the minor (Cu3Sn and β-(Cu,Sn)) was dispersed among the Cu6Sn5 grains. The electrochemical properties of Cu6Sn5 thin film were evaluated in coin type half-cell, which was configured with Cu6Sn5, thin film electrode, Li metal electrode and typical 1 mol LiPF6 in EC:DMC (1:1) electrolyte. Annealed Cu/Sn electrode took and released Li ions well during Li insertion and de-insertion. Cycle performance of annealed Cu/Sn electrode was better than that of as-deposited Sn electrode, which was caused by topotactic reaction of Cu6Sn5and composite structure of Cu/Sn alloys.
Controlled synthesis of anganese (oxihydr)oxides in queous olution by hermolysis
Authors: Cassaignon S. , Koelsch M. , Jolivet J-P. 
Published: September 2012

AbstractNanometric particles of manganese (oxihydr)oxides (Hausmannite, Manganite, Nsutite, Pyrolusite and Vernadite) have been synthesized by thermohydrolysis of MnCl2 and/or KMnO4in aqueous medium. The modification of various chemical parameters (pH and precursors concentration, nature of the reducer or oxidizer, temperature and duration of the thermolysis) allow the control of the nature, the size and the morphology of the obtained particles.
Synthesis of nanometric TiO2 in aqueous solution by soft chemistry: obtaining of anatase, brookite and rutile with controlled shapes
Authors: Koelsch Magali , Cassaignon Sophie , Jolivet Jean-Pierre 
Published: September 2012

AbstractNanometric particles of titania, exhibiting anatase, brookite or rutile polymorphs, were synthesized by thermohydrolysis of TiCl4 in aqueous medium. The adjustement of physico-chemical parameters (acidity, ionic strength, anions, temperature) allows to tune the crystalline structure, the size and the morphology of the particles. Brookite results from the precipitation of titanium in HCl, HBr or HNO3 whereas anatase is formed in H2SO4 medium. Adding salts in HCl medium leads to ionic strength or complexation effect. Varying the temperature of thermohydrolysis implies modification on yield, size and morphology of the particles.
Epitaxial Chemical Deposition of ZnO Nanocolumns from NaOH Solutions
Authors: Peterson Renee B. , Fields Clark L. , Gregg Brian A. 
Published: September 2012

AbstractA new method of depositing epitaxial ZnO nanocolumns on sputter-coated ZnO substrates is described that utilizes supersaturated zincate species in sodium hydroxide solutions and requires no complexing agents. Uniform arrays of columns are grown reproducibly over entire substrates in 10 to 50 min. Columns are 50 to 2000 nm long and 50 to 100 nm wide. Strict substrate cleaning and/or preparations are not necessary with this method, in contrast to many other techniques. Films grow only on substrates pre-coated with ZnO, not on bare glass or ITOor SnO2-coated glass. Factors affecting the column growth are elucidated and experimental observations are correlated with crystal growth theory.
Characterization of Vapor Deposited, NanoStructured Membranes
Authors: Jankowski Alan F. , Cherepy Nerine J. , Ferreira James. L. , Hayes Jeffrey P. 
Published: September 2012

AbstractThe vapor deposition methods of planar magnetron sputtering and electron-beam evaporation are used to synthesize materials with nanostructured morphological features that have ultra-high surface areas with continuous open porosity at the nanoscale. These nanostructured membranes are used in a variety of fuel cells to provide electrode and catalytic functions. Specifically, stand alone and composite nickel electrodes for use in thin film solid-oxide, and molten carbonate fuel cells are formed by sputter deposition and electron beam evaporation, respectively. Also, a potentially high-performance catalyst material for the direct reformation of hydrocarbon fuels at low temperatures is deposited as a nanostructure by the reactive sputtering of a copper-zinc alloy using a partial pressure of oxygen at an elevated substrate temperature.
A review of some Antiretroviral therapies used in Management of HIV/AIDS in Ghana
Authors: Osonuga A , Osonuga OA , Osonuga AA , Osonuga IO 
Published: September 2012

HIV is a RNA retrovirus that causes progressive weakening of the hosts immune system increasing susceptibility to opportunistic infections. Antiretroviral drugs are currently used to manage the infection. This paper reviews the benefits and the toxicity associated with ARTs currently used in Ghana. Google search, PUBMED and Google scholar were used to gather information from different books, websites and peerreviewed journal articles. ARTs significantly improved the quality of life of people living with HIV/AIDS by increasing the CD4 count and reducing the viral load. ARTs have short and long term side effects which may be life threatening. Toxicity may vary from drug to drug and from one drug class to the other. We conclude that it is important to select a regimen that is not only effective but also safe. This requires consideration of not only the toxicity potential of an ARV regimen but also an individual patients underlying conditions, concomitant medications and history of drug intolerance. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11716 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12
A Comparative Study Of Surgical Management Of Subtrochanteric Fractures In Children
Authors: Sahu RL , Gupta P 
Published: September 2012

Introduction: Subtrochateric femoral fracture is a major cause of morbidity and mortality in patients with lower extremity injuries. There have been no studies that have specifically looked at the management of subtrochanteric femoral fractures in skeletally immature adolescents. It was the purpose of this study to investigate the treatment of this injury in this unique patient population. Methods: This study was conducted in the Department of Orthopaedic surgery in M. M. Medical College from July 2006 to November 2008. Thirty-four patients were recruited from Emergency and out patient department having closed subtrochanteric femoral fracture. All patients were operated under general or spinal anesthesia. All patients were followed for twelve months. Results: All children achieved union in a mean time of 10 weeks (range from 6 - 16 weeks) depending on the type of long bone. Full weight bearing was possible in a mean time of 8.8 weeks. Mean duration of hospital stay was 9.8 days. The mean follow-up period was 28 months (17-48 months). Complications were recorded in 4 (11.77%) patients and included: two entry site skin irritations, one protrusion of the wires through the skin and one delayed union. The results were excellent in 97.06% and good in 2.97% patients. Conclusions: We conclude that Rigid and close interlocking nailing between the age of 9-16 years offered excellent fracture stability allowing early mobilization (early weight bearing) and joint motion in comparisons to the other groups and between the age of 6-8 years titanium elastic nail and bridging plate offered excellent result. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11718 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12
An Over-View of Tuberculosis of Female Genital Tract With Reference To Experience in a Medical College in Rural Set-Up in West Bengal: A Retrospective Two Year Study
Authors: Datta J , Ghosh TK , Ghosh S , Guha D 
Published: September 2012

Aim: To determine frequency of female genital tract (FGT) tuberculosis (TB) in the gynecological biopsies received in the Department of pathology of a peripheral medical college. Methods: This is a retrospective study conducted in the Department of Pathology of Burdwan Medical College & Hospital. Histopathological records of two year (2008-2010) were retrieved and searched for the cases of female genital tract TB. Relevant histopathological findings and clinical data were recorded and analyzed. Results: There were 1537 cases of gynecological biopsy and 9 cases were diagnosed as FGT tuberculosis based on histopathological and clinical findings. Ovarian benign cystic teratoma was seen in one case along with ipsilateral tuberculous salpingitis, one case showed B/L ovarian tuberculosis with involvement of both the tubes. Bilateral fallopian tubes were involved in 2 cases and endometrial tuberculosis was diagnosed in 5 cases with 1 case showing simultaneous involvement of the cervix. In one case omental biopsy received along with tubal specimen showed tuberculous granulomas. Conclusion: FGT tuberculosis was usually seen in age 16-28 years and constituted 0.59% of total gynecological cases. Fallopian tubes, ovaries and endometrium and cervix were affected with the involvement of peritoneum or omentum, commonest being tuberculous endometritis. Histopathology, in association with clinical findings still remains gold standard for the diagnosis of FGT tuberculosis in our country despite advancement in diagnostic modalities; however, incidental histological detection in clinically unanticipated cases is not an uncommon event. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11719 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12
Efficacy and Safety of Hydroquinone, Kojic Acid and Glycolic Acid Combination in the Treatment of Melasma
Authors: Chowdhury WK , Wahab MA , Khondker L , Khan MSI , Shirajul IK 
Published: September 2012

Background & Methodology: It was an opened clinical trial. The study was carried out from March 2009 to February 2011, in the outpatient department of Dermatology and Venereology, Bangabandhu Sheikh Mujib Medical University (BSMMU) Dhaka, Bangladesh to evaluate the efficacy and side effects of the combination therapy of hydroquinone(HQ), kojic acid(KA) and glycolic acid(GA) for the treatment of melasma. Patients suffering from melasma were selected as study population. Within the period of data collection, thirty patients of melasma were assigned purposively. The efficacy was evaluated using Melasma Area and Severity Index (MASI) Score. The severity of melasma of each of the four regions (forehead, right malar region, left malar region and chin) are assessed based on three variables, percentage of the total area involved (A), darkness (D) and homogenicity (H).Results:The study showed that majority (30%) of the cases were between 20 to 25 years, majority (77%) of patients were female, (50%) patients were housewives, (50%) were in graduation level of education, (50%) of patients was found as upper class and negative family history was present in majority (80%) of cases. It was seen that highest (93%) number of patients were malar type and 7% were centro-facial type. The study showed the change in MASI Score after treatment with combination therapy (GA 2%, HQ 2% and KA 1%). After 12 weeks of treatment, the average MASI score was decreased by 24.20% indicating mild reduction of the severity of melasma and 18%, 18%, 9% and 55% patients developed side -effects like itching, burning sensation, scaling, and erythema respectively. Conclusion: Combination therapy (GA 2%, HQ 2% and KA 1%) has a few lightening effect on melasma, with no remarkable side effects. Further study should be conducted with large number of sample and longer follow up. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11720 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12
The analgesic and acute anti-inflammatory effect of the ethanolic extract of the leaves of Paederia foetida (EEPF) on experimental animal models
Authors: Das S , Bordoloi P K , Saikia P , Kanodia L 
Published: September 2012

Objective:To study the analgesic and acute anti-inflammatory effect of the ethanolic extract of the leaves of Paederia foetida (EEPF) on experimental animal models. Materials and Methods: Fresh leaves were collected, air-dried, powdered, and percolated in 95% ethanol. Acute toxicity test was done according to OECD guidelines. Healthy albino rats (150-200 gm) of either sex were taken and divided into five groups with six animals in each group for central analgesic activity by tail flick method. Peripheral analgesic activity by 1% glacial acetic acid induced writhing test by taking albino mice (20-30 gm) of either sex which were divided into three groups with six animals in each. EEPF was used in a dose of 500 mg/kg bodyweight subcutaneously for tail-flick method and orally for writhing test. In tail-flick method the basal reaction time was taken and a cut-off period of 10 sec was observed. Reaction time were recorded at predrug, 15, 30, 60, 90, 120, 150 and 180 minutes after administration of drug . The standard drug used for central analgesic activity was pethidine 5 mg/kg bw, naloxone 1mg/kg as antagonist and naloxone 1mg/kg bw with 500mg/kg bw of EEPF to study the central mechanism of action. The standard drug used for peripheral analgesic activity was aspirin 100mg/kg bw orally. A control group was maintained in all the models. For anti-inflammatory study, three groups of animals of either sex (n = 6), weighing 150-200g of the species Rattus norvegicus were taken for the study. Group A was taken as control (Normal salie, 10 mL/kg body weight), Group B as test group (EEPF 500 mg/kg body weight), and Group C as standard (Aspirin 100 mg/kg body weight). The animals were studied for acute inflammation by Carrageenan-induced rat paw edema. Statistical analysis was done by one-way analysis of variance followed by multiple comparison tests.Results: EEPF significantly increased the reaction time in tail-flick method (p<0.05) whereas the combination of naloxone and EEPF decreased the reaction time indicating that naloxone inhibits the analgesic effect of EEPF. In 1% glacial acetic acid induced writhing EEPF reduced writhing significantly In acute inflammation, there was significant inhibition of paw edema in Groups B, C in comparison with Group A (P < 0.05). Conclusion:The ethanolic extract of Paederia foetida has significant analgesic and anti-inflammatory activity. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11723 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12
Primary squamous cell carcinoma of kidney - a case report of unusual local recurrence with literature review
Authors: Sharma S , Choudhury KB , Mandal S , Majumder A 
Published: September 2012

Primary squamous cell carcinoma of the kidney is a rare clinical entity. Primary squamous cell carcinoma is more frequently reported in urinary bladder and male urethra than in kidney. Primary renal squamous cell carcinoma (RSCC) accounts for less than 5% of urothelial tumours in urinary system. Very few cases of primary squamous cell carcinoma of kidney have been reported in the world literature. Only forty-six cases over forty four years had been reported from Mayo Clinic. These neoplasms are highly aggressive and locally advanced or metastatic at the time of presentation. Here we report such a case of primary squamous cell carcinoma of kidney in a 50-year-old lady at a locally recurrent stage with fistulous tract formation. Palliative radiotherapy came out to be a good clinical modality even in locally recurrent stage in this patient. DOI: http://dx.doi.org/10.3329/bjms.v11i3.11734 Bangladesh Journal of Medical Science Vol. 11 No. 03 July12