Engineering dissipation with phononic spectral hole burning.

Optomechanics, nano-electromechanics, and integrated photonics have brought about a renaissance in phononic device physics and technology. Central to this advance are devices and materials supporting ultra-long-lived photonic and phononic excitations that enable novel regimes of classical and quantum dynamics based on tailorable photon-phonon coupling. Silica-based devices have been at the forefront of such innovations for their ability to support optical excitations persisting for nearly 1 billion cycles, and for their low optical nonlinearity. While acoustic phonon modes can persist for a similar number of cycles in crystalline solids at cryogenic temperatures, it has not been possible to achieve such performance in silica, as silica becomes acoustically opaque at low temperatures. We demonstrate that these intrinsic forms of phonon dissipation are greatly reduced (by >90%) by nonlinear saturation using continuous drive fields of disparate frequencies. The result is a form of steady-state phononic spectral hole burning that produces a wideband transparency window with optically generated phonon fields of modest (nW) powers. We developed a simple model that explains both dissipative and dispersive changes produced by phononic saturation. Our studies, conducted in a microscale device, represent an important step towards engineerable phonon dynamics on demand and the use of glasses as low-loss phononic media.

Multiferroic BiFeO3 thin films for multifunctional devices.

We report the metalorganic chemical vapor deposition of crystalline BiFeO3 films on platinized silicon substrates using n-butylferrocene, triphenylbismuth and oxygen. Based on thermogravimetric analysis data, the suitability of these two precursors for depositing BiFeO3 is discussed. The deposited films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Composition analysis using X-ray photoelectron spectroscopy revealed that the films were stoichiometric BiFeO3. Electrostatic force microscopy indicated that the film had polarizable domains that showed no deterioration in polarization over time long after electric poling. The film showed a saturation magnetization of 10 +/- 1 emu/cm3 at room temperature.

Structural, magnetic, and electrical studies on polycrystalline transition-metal-doped BiFeO(3) thin films.

We have synthesized a range of transition-metal-doped BiFeO(3) thin films on conducting silicon substrates using a spin-coating technique from metal-organic precursor solutions. Bismuth, iron and transition-metal-organic solutions were mixed in the appropriate ratios to produce 3% transition-metal-doped samples. X-ray diffraction studies show that the samples annealed in a nitrogen atmosphere crystallize in a rhombohedrally distorted BiFeO(3) structure with no evidence for any ferromagnetic secondary phase formation. We find evidence for the disappearance of the 404 cm(-1) Raman mode for certain dopants indicative of structural distortions. The saturation magnetization of these BiFeO(3) films has been found to increase on doping with transition metal ions, reaching a maximum value of 8.5 emu cm(-3) for the Cr-doped samples. However, leakage current measurements find that the resistivity of the films typically decreases with transition metal doping. We find no evidence for any systematic variation of the electric or magnetic properties of BiFeO(3) depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.

Clinical profile of patients with pleural effusion admitted to KMCTH.

BACKGROUND: Pleural effusion is the common findings in patients presenting with cardiopulmonary symptoms but specific studies are lacking in Nepal. OBJECTIVE: The main objective of this study is to fi nd out the various causes of pleural effusion, their mode of clinical presentation and laboratory analysis of blood and pleural fluid to aid diagnosis of patients with pleural effusion. MATERIALS AND METHODS: Retrospective data from July 2009 to July 2007 from all the cases diagnosed with pleural effusion were taken. Altogether 100 cases diagnosed with pleural effusion by chest X-ray (Posterior- Anterior and Lateral view) and Ultrasonogram of the chest were studied. The following parameters were analysed: Patients demographic profile, causes, location (Unilateral, Bilateral), Blood haemoglobin and count, sputum profile, Monteux test, chest X-ray and USG findings and pleural fluid analysis[Biochemical, Haematological, Microbiological (culture and stain) and cytological]. This study was analysed by using SPSS 16. RESULTS: The mean age of the patient was 44.89 +/- 21.59 and must patients with pleural effusion belong to age group 21-30. Most common cause of pleural effusion was found to be tubercular effusion followed by parapneumonic effusion. Right sided effusion was seen in most cases of tubercular parapneumonic and malignant effusion whereas bilateral effusion was seen in 87.5% of the patient (7 out of 8) having congestive heart failure and all cases of renal disease (4 out of 4). Shortness of breath (83%), cough (67%) and fever (66%) are the most common mode of clinical presentation. CONCLUSION: Our study concluded that the most common cause of unilateral pleural effusion is tuberculosis followed by parapneumonic effusion and most cases of those belong to younger age group (21-30 yrs) and most common cause of bilateral pleural effusion is congestive cardiac failure.

Structural and magnetic properties of bulk Mn2PtSn.

Interplay between structural and magnetic order parameters is one of the key mechanisms of tuning properties of materials intended for device applications in spintronics. Here, using density functional calculations, we study combined effects of tetragonal distortion and non-collinear magnetic order in Mn2PtSn. We show that this material has two energetically close energy minimums corresponding to tetragonal lattice. In one of these phases, Mn2PtSn exhibits ferrimagnetic order with nearly fully compensated total magnetic moment, while in the other phase that corresponds to the lowest energy, a non-collinear magnetic arrangement emerges, with very large canting angle of the Mn local magnetic moments. The non-collinear alignment is explained through the interplay of exchange couplings between nearest and next nearest neighbor Mn atoms. Results are compared with those reported in recent literature, both experimental and theoretical.

Perception of Palliative Care among Medical Students in a Teaching Hospital.

INTRODUCTION: Palliative care is an approach that improves the quality of life of patients and their families facing the problems associated with life-threatening illness. Palliative care must be a part of every medical personnel's practice. But still medical education curriculums have not included palliative care in its syllabus, sufficiently due to which most of the health professional are not aware about this specialty. The purpose of this study is to find out the perception of the medical students in palliative care in a teaching hospital. METHODS: A descriptive study was done among 270 undergraduate medical students studying in Institute of Medicine using a self structured pretested questionnaire. Data was entered in Microsoft Excel and analyzed by using SPSS 21. RESULTS: Of the total 270 undergraduate medical students only 152 has heard the word "palliative care". Only 84 students know, palliative care can be provided early in the life threatening illness. Total 80 students know it doesn't intend to postpone and hasten death. Though only 49 students didn't know PC is not included in our curriculum, 227 are interested to learn about it if given any opportunity. CONCLUSIONS: The perception of palliative care medicine is low in first couple of year of medical study. It is increased in clinically exposed students but is surprisingly more in fourth year than final year undergraduate medical students. However, it should be included in undergraduate medical study.

Effect of Co substitution on the magnetic and electron-transport properties of Mn2PtSn.

The structural, magnetic and electron-transport properties of Mn(2)Pt(1-x)Co(x)Sn(x = 0, 0.3, 0.5, 0.7, 1) ribbons prepared by arc-melting and melt-spinning were investigated. The rapidly quenched alloys with x = 0 and 0.3 were found to crystallize in the inverse tetragonal structure, but the structure transformed into inverse cubic as x increased to 0.5. At room temperature, the samples are ferro or ferrimagnetic, and the Curie temperature increases by 225 K from 370 K for Mn(2)PtSn (x = 0) to 595 K for Mn(2)CoSn (x = 1). The measured anisotropy constants for the inverse-tetragonal alloys are on the order of 1 Merg cm(-3) at room temperature. The ribbons are moderately conducting with the room temperature resistivities being between 0.4 and 8.4 mΩ cm. Interestingly, the thermal coefficient of resistivity transforms from positive to negative and the magnetoresistance transforms from negative to positive as the value of x reaches 0.5.

Structural and magnetic transitions in cubic Mn3Ga.

The structural, magnetic and electron-transport properties of cubic Mn3Ga have been investigated. The alloys prepared by arc melting and melt-spinning show an antiferromagnetic spin order at room temperature but undergo coupled structural and magnetic phase transitions at 600 and 800 K. First-principles calculations show that the observed magnetic properties are consistent with that of a cubic Mn3Ga crystallizing in the disordered Cu3Au-type structure. The samples exhibit metallic electron transport with a resistance minimum near 30 K, followed by a logarithmic upturn below the minimum. The observed anomaly in the low-temperature resistivity has been discussed as a consequence of electron scattering at the low-lying excitations of the structurally disordered Mn3Ga lattice.

Anomalous Hall effect and electron transport in ferromagnetic MnBi films.

The electron transport properties of highly c-axis oriented MnBi thin films of various thicknesses have been investigated. Samples are metallic but the low temperature resistivity shows an unusual T(3) dependence. Transverse Hall effect measurements show that both the ordinary and anomalous Hall coefficients decrease with decreasing temperature below 300 K, but the ordinary Hall coefficient (R(0)) undergoes a sign reversal around 105 K, where the magnetic anisotropy also changes sign. Analysis of the Hall data for various samples shows that the anomalous Hall coefficient (R(s)) exhibits a strong ρ(2) dependence, where ρ is the longitudinal resistivity.