Magnetic field induced band depopulation in intrinsic InSb: A revisit

The effect of Landau level formation on the population of intrinsic electrons in InSb is probed near room temperature in magnetic fields upto 16 Tesla. Although the measured magnetic field dependence of the Hall coefficient is qualitatively similar to published results, it is shown that the data may also be explained by simply including ambipolar conduction. Thus the inference on band depopulation drawn from previous measurements on InSb is inconclusive unless both the Hall and the magnetoresistive components of the resistivity tensor are simultaneously measured and modelled. When the model includes both depopulation and ambipolar conduction, a reasonable agreement with theory can be established.Comment: 5 figs, to appear in Journal of Physics : Condensed Matte

Scattering of Carriers by Charged Dislocations in Semiconductors

The scattering of carriers by charged dislocations in semiconductors is studied within the framework of the linearized Boltzmann transport theory with an emphasis on examining consequences of the extreme anisotropy of the scattering potential. A new closed-form approximate expression for the carrier mobility valid for all temperatures is proposed. The ratios of quantum and transport scattering times are evaluated after averaging over the anisotropy in the relaxation time. The value of the Hall scattering factor computed for charged dislocation scattering indicates that there may be a factor of two error in the experimental mobility estimates using the Hall data. An expression for the resistivity tensor when the dislocations are tilted with respect to the plane of transport is derived. Finally an expression for the isotropic relaxation time is derived when the dislocations are located within the sample with a uniform angular distribution.Comment: 3 figure

General anesthesia for cesarean section in the presence of mitral stenosis associated with severe pulmonary hypertension

Rheumatic heart disease (RHD) is the most common cause of cardiac disease during pregnancy in India. A case of severe pulmonary hypertension (pulmonary arterial pressure- 98 mm Hg) secondary to mitral stenosis associated with RHD in a 28-year old woman, is described. She underwent a high risk elective cesarean section under general anesthesia at 36 weeks of gestation. The intraoperative and postoperative course was uneventful. The advantages of general anesthesia over neuraxial blockade during cesarean section are discussed in this report. The management of patients at a high risk of developing pulmonary edema and decompensated heart failure in the perioperative period has been stressed upon. A thorough understanding of the pathophysiology and complications of RHD during pregnancy and cesarean section is required for managing the disease successfully

Gynecological profile of patients undergoing laparoscopy/laparotomy in a tertiary care hospital

Background: Laparoscopy is not only used in the elective surgery but also used in the emergency surgery. It is also found to be useful in the acute abdominal emergencies. It is useful in removing any diagnostic doubts. It is also useful in the treatment of diseases. The objective of the study was to study the gynecologic profile of patients undergoing laparoscopy/laparotomy in gynecology department of a tertiary care hospitalMethods: A hospital based cross sectional study was carried out at department of Obstetrics and Gynecology of S. V. Medical College, Tirupati from September 2014 to February 2015, for a period of six months. A total of 36 patients were evaluated for gynecological problems during the study period based on the inclusion and exclusion criteria. They were evaluated for menstrual complaints, chief presenting complaints, clinical diagnosis, scan diagnosis and laparotomy evaluation. Institutional Ethics Committee permission was taken before the start of the study. Informed consent was taken from all patients after explaining them about the nature of the study.Results: Ovarian cyst was the most common presentation which constituted more than half of the patients (55.6%). All patients i.e. 36 (100%) had menorrhagia as the complaint of menstrual irregularity. Out of 9 cases, clinical diagnosis differed in all cases, thus giving zero percent of accuracy for clinical diagnosis. Scan diagnosis matched with laparotomy confirmation in only 3 (33.3%) of cases. One case which was labeled as normal was found to have bilateral functional ovarian cyst on laparotomy confirmation. One case which was labeled as left ovarian cyst was found to have no cyst on laparotomy confirmation.Conclusions: Thus, laparoscopy is a useful tool for diagnosis and therapeutic accuracy in gynecological disease in routine as well as in emergencies. It is safe, effective, less time consuming, economical and patient friendly

Extended excitons and compact heliumlike biexcitons in type-II quantum dots.

We have used magneto-photoluminescence measurements to establish that InP/GaAs quantum dots have a type-II band (staggered) alignment. The average excitonic Bohr radius and the binding energy are estimated to be 15 nm and 1.5 meV respectively. When compared to bulk InP, the excitonic binding is weaker due to the repulsive (type-II) potential at the hetero-interface. The measurements are extended to over almost six orders of magnitude of laser excitation powers and to magnetic fields of up to 50 tesla. It is shown that the excitation power can be used to tune the average hole occupancy of the quantum dots, and hence the strength of the electron-hole binding. The diamagnetic shift coe±cient is observed to drastically reduce as the quantum dot ensemble makes a gradual transition from a regime where the emission is from (hydrogen-like) two-particle excitonic states to a regime where the emission from (helium-like) four-particle biexcitonic states also become significant