2,273 research outputs found
Double heterostructure lasers with facets formed by a hybrid wet and reactive-ion-etching technique
Double heterostructure lasers were fabricated in which one of the laser facets was produced by a hybrid wet and reactive-ion-etching technique. This technique is suitable for GaAs/GaAlAs heterostructure lasers and utilizes the selectivity of the plasma in preferentially etching GaAs over GaAlAs. Lasers fabricated by this technique are compatible with optoelectronic integration and have threshold currents and quantum efficiency comparable to lasers with both mirrors formed by cleaving. The technique enables the use of relatively higher pressures of noncorrosive gases in the etch plasma resulting in smoother mirror surfaces and further eliminates the nonreproducibility inherent in the etching of GaAlAs layers
Magnetoresistance in the superconducting state at the (111) LaAlO/SrTiO interface
Condensed matter systems that simultaneously exhibit superconductivity and
ferromagnetism are rare due the antagonistic relationship between conventional
spin-singlet superconductivity and ferromagnetic order. In materials in which
superconductivity and magnetic order is known to coexist (such as some
heavy-fermion materials), the superconductivity is thought to be of an
unconventional nature. Recently, the conducting gas that lives at the interface
between the perovskite band insulators LaAlO (LAO) and SrTiO (STO) has
also been shown to host both superconductivity and magnetism. Most previous
research has focused on LAO/STO samples in which the interface is in the (001)
crystal plane. Relatively little work has focused on the (111) crystal
orientation, which has hexagonal symmetry at the interface, and has been
predicted to have potentially interesting topological properties, including
unconventional superconducting pairing states. Here we report measurements of
the magnetoresistance of (111) LAO/STO heterostructures at temperatures at
which they are also superconducting. As with the (001) structures, the
magnetoresistance is hysteretic, indicating the coexistence of magnetism and
superconductivity, but in addition, we find that this magnetoresistance is
anisotropic. Such an anisotropic response is completely unexpected in the
superconducting state, and suggests that (111) LAO/STO heterostructures may
support unconventional superconductivity.Comment: 6 Pages 4 figure
Electric Field Effect in Diluted Magnetic Insulator Anatase Co:TiO2
An external electric field induced reversible modulation of room temperature
magnetic moment is achieved in an epitaxial and insulating thin film of
dilutely cobalt-doped anatase TiO2. This first demonstration of electric field
effect in any oxide based diluted ferromagnet is realized in a high quality
epitaxial heterostructure of PbZr0.2Ti0.8O3/Co:TiO2/SrRuO3 grown on (001)
LaAlO3. The observed effect, which is about 15% in strength in a given
heterostructure, can be modulated over several cycles. Possible mechanisms for
electric field induced modulation of insulating ferromagnetism are discussed.Comment: 14 pages, 4 figure
Superconductivity and Frozen Electronic States at the (111) LaAlO/SrTiO Interface
In spite of Anderson's theorem, disorder is known to affect superconductivity
in conventional s-wave superconductors. In most superconductors, the degree of
disorder is fixed during sample preparation. Here we report measurements of the
superconducting properties of the two-dimensional gas that forms at the
interface between LaAlO (LAO) and SrTiO (STO) in the (111) crystal
orientation, a system that permits \emph{in situ} tuning of carrier density and
disorder by means of a back gate voltage . Like the (001) oriented LAO/STO
interface, superconductivity at the (111) LAO/STO interface can be tuned by
. In contrast to the (001) interface, superconductivity in these (111)
samples is anisotropic, being different along different interface crystal
directions, consistent with the strong anisotropy already observed other
transport properties at the (111) LAO/STO interface. In addition, we find that
the (111) interface samples "remember" the backgate voltage at which they
are cooled at temperatures near the superconducting transition temperature
, even if is subsequently changed at lower temperatures. The low
energy scale and other characteristics of this memory effect ( K)
distinguish it from charge-trapping effects previously observed in (001)
interface samples.Comment: 6 pages, 5 Figure
METABOLIC SYNDROME IN MADHUMEGAM (TYPE 2 DIABETES MELLITUS) PATIENTS REPORTING AT NATIONAL INSTITUTE OF SIDDHA – A CROSS SECTIONAL STUDY
Introduction: Madhumegam is a clinical condition characterised by frequent and excessive urination which ultimately leads to deterioration of seven body constituents and three humours. Its signs and symptoms may be correlated with Diabetes mellitus in modern science. Since, metabolic syndrome has become major cause of morbidity and mortality, identifying its cause and prevention has gained immense importance.
Aim: This study aimed at determining the prevalence of metabolic syndrome in Madhumegam (Type 2 Diabetes mellitus) patients and to identify the most critical predictive risk factors of metabolic syndrome.
Methods: This hospital based cross sectional study involved 100 type 2 diabetes mellitus patients and was conducted at Ayothidoss Pandithar Hospital, National Institute of Siddha. This study used questionnaire to obtain information on diabetic condition, anthropometric measurements and lipid profile. Metabolic syndrome was defined according to the International Diabetes Federation criteria.
Results: The prevalence of metabolic syndrome was 53% in the study population. Elevated triglyceride was the commonest component (77.3%) followed by lowered HDL (51%). Female type 2 diabetic patients had a higher prevalence of metabolic syndrome (54.7%) than their male counterparts (45.3%). With respect to age, individual within the age group of 60-69 had highest prevalence of metabolic syndrome while age group of 30-39 has least prevalence of metabolic syndrome.
Conclusion: Elevated triglyceride for men and lowered HDL for women were the strongest risk factors. Metabolic syndrome is a significant health problem and its preventive strategies should focus on early diagnoses and lifestyle modification
Temperature dependent optical studies of TiCoO
We present the results of Raman and photoluminescence (PL) studies on
epitaxial anatase phase TiCoO films for = 0-0.07, grown by
pulsed laser deposition. The low doped system (=0.01 and 0.02) shows a Curie
temperature of ~700 K in the as-grown state. The Raman spectra from the doped
and undoped films confirm their anatase phase. The photoluminescence spectrum
is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV
at temperatures below 120 K. This peak is characteristic of the anatase-phase
TiO and shows a small blueshift with increasing doping concentration. In
addition to the emission from STE, the Co-doped samples show two emission lines
at 2.77 eV and 2.94 eV that are absent in the undoped film indicative of a
spin-flip energy.Comment: 8 pages, 4 figure
Standardization of the method for estimation of ethambutol in pharmaceutical preparations and biological fluid
A simple column chromatographic method for determination of ethambutol (EMB) in pharmaceutical preparations
containing EMB in combination with other anti-TB drugs is presented. The method involved extraction of EMB into an
organic solvent. followed by basification and column chromatographic separation on Amberlite CG 50 (100-200 mesh) and
elution with suitable eluants and estimation at a wavelength of 270 nm. The assay was linear from 25 to 400 μg/ml. The
relative standard deviations of intra and inter day assays were lower than 5%. Ethambutol was recovered from human urine
quantitatively and stable for a period of atleast one week in urine stored at-20°C
Interface characterization of all-perovskite oxide field effect heterostructures
All-oxide devices consisting of Niobium-doped Strontium Titanate (Nb:STO)/Strontium Titanate (STO)/Lanthanum Strontium Cuprous Oxide (LSCO) heterostructures were fabricated and characterized electrically for their interface properties through capacitance-voltage (C-V) and current-voltage (I-V) techniques, in the context of electric field effect studies. The C-V studies establish the occurrence of charge modulation in the LSCO channel. Absence of hysteresis in the C-V characteristic when the voltage is retraced suggests the absence of mobile ions in the gate oxide and slow interface traps. This is further corroborated by the absence of drift in the C-V characteristic and shift in the flat band voltage (V FB) when the device is subjected to temperature-bias aging. The interface state density obtained from V FB is ~1012/cm2. The uncompensated hole concentration in the LSCO channel calculated from the measured room temperature C-V data is ~1020/cm3 and is in good agreement with the expected hole concentration in LSCO. Current-time and current-voltage plots are invariant with respect to the polarity of the applied voltage up to ~5 V. This, in a structure with asymmetric interfaces, indicates that the electrical contacts to STO are non-blocking and the conduction through STO is bulk-limited in this voltage regime. Thickness dependent current and capacitance studies also corroborate the bulk-limited nature of conduction through the device in this voltage regime. However, I-V characteristic shows a rectifying nature beyond ~8 V indicating that the mechanism in this voltage regime could be interface limited
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