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Kaushik Bhattacharya

Publications and source records attributed to Kaushik Bhattacharya.

13 recordsLinked to original sources
PubMed2006

Temperature of the inflaton and duration of inflation from Wilkinson microwave anisotropy probe data.

If the initial state of the inflaton field is taken to have a thermal distribution instead of the conventional zero particle vacuum state then the curvature power spectrum gets modified by a temperature dependent factor such that the fluctuation spectrum of the microwave background radiation is enhanced at larger angles. We compare this modified cosmic microwave background spectrum with Wilkinson microwave anisotropy probe data to obtain an upper bound on the temperature of the inflaton at the time our current horizon crossed the horizon during inflation. We further conclude that there must be additional -foldings of inflation beyond what is needed to solve the horizon problem.

Journal Article↗
PubMed2006

Uterus didelphys with fibroid uterus and ovarian cyst--rare Muellerian malformation.

Persistent Muellerian duct syndrome is a very rare anomaly. A woman of 46-year-old was admitted with the history of lower abdominal pain, bleeding per vaginum and irregular menstrual cycles for last 6 months. An irregular non-tender mass of 16 x 10cm in size was palpable in suprapubic region. Per vaginal examination revealed two cervices and an incomplete vaginal septum. Ultrasound abdomen showed one uterus with endometrial cavity clearly delineated with a fibroid and an ovarian cyst in the left lumbar region. On laparotomy, 2 uterii along with a fibroid from the anterior wall of left uterus and a left ovarian cyst was seen. Patient had undergone total abdominal hysterectomy and adnexa removal. The specimen showed florid adenomyosis with leiomyoma of fibroid.

Cervix Uteri↗
PubMed2005

Depletion layers and domain walls in semiconducting ferroelectric thin films.

Commonly used ferroelectric perovskites are also wide-band-gap semiconductors. In such materials, the polarization and the space-charge distribution are intimately coupled, and this Letter studies them simultaneously with no a priori ansatz on either. In particular, we study the structure of domain walls and the depletion layers that form at the metal-ferroelectric interfaces. We find the coupling between polarization and space charges leads to the formation of charge double layers at the 90 degrees domain walls, which, like the depletion layers, are also decorated by defects like oxygen vacancies. In contrast, the 180 degrees domain walls do not interact with the defects or space charges. Implications of these results to domain switching and fatigue in ferroelectric devices are discussed.

Journal Article↗
PubMed2004

Investigation of twin-wall structure at the nanometre scale using atomic force microscopy.

The structure of twin walls and their interaction with defects has important implications for the behaviour of a variety of materials including ferroelectric, ferroelastic, co-elastic and superconducting crystals. Here, we present a method for investigating the structure of twin walls with nanometre-scale resolution. In this method, the surface topography measured using atomic force microscopy is compared with candidate displacement fields, and this allows for the determination of the twin-wall thickness and other structural features. Moreover, analysis of both complete area images and individual line-scan profiles provides essential information about local mechanisms of twin-wall broadening, which cannot be obtained by existing experimental methods. The method is demonstrated in the ferroelectric material PbTiO(3), and it is shown that the accumulation of point defects is responsible for significant broadening of the twin walls. Such defects are of interest because they contribute to the twin-wall kinetics and hysteresis.

Journal Article↗
PubMed2004

Crystal symmetry and the reversibility of martensitic transformations.

Martensitic transformations are diffusionless, solid-to-solid phase transitions, and have been observed in metals, alloys, ceramics and proteins. They are characterized by a rapid change of crystal structure, accompanied by the development of a rich microstructure. Martensitic transformations can be irreversible, as seen in steels upon quenching, or they can be reversible, such as those observed in shape-memory alloys. In the latter case, the microstructures formed on cooling are easily manipulated by loads and disappear upon reheating. Here, using mathematical theory and numerical simulation, we explain these sharp differences in behaviour on the basis of the change in crystal symmetry during the transition. We find that a necessary condition for reversibility is that the symmetry groups of the parent and product phases be included in a common finite symmetry group. In these cases, the energy barrier to lattice-invariant shear is generically higher than that pertaining to the phase change and, consequently, transformations of this type can occur with virtually no plasticity. Irreversibility is inevitable in all other martensitic transformations, where the energy barrier to plastic deformation (via lattice-invariant shears, as in twinning or slip) is no higher than the barrier to the phase change itself. Various experimental observations confirm the importance of the symmetry of the stable states in determining the macroscopic reversibility of martensitic transformations.

Journal Article↗
PubMed2004

Chronic nonhealing ulcer of the lower limb with mixed arterio-venous pathology.

Chronic wounds in which arterial and venous pathology coexist are relatively uncommon. The authors report a case of a diabetic lady who presented with claudication pain and a chronic nonhealing lower extremity wound of more than 6 months. In these patients, it is mandatory to treat the arterial insufficiency first, and it is also important to avoid compression bandaging, which is advised for venous ulcers.

Journal Article↗
PubMed2003

Mycetoma leg a--case report.

One rare and peculiar result of repeated minor trauma to the leg is Madura foot. Caused by fungi or fungus-like bacteria, Madura foot is found mainly in the tropics. A report of a classic case with chronic indurated swelling involving the leg and a discharge of yellowish granules is presented. The case is reported to highlight the fact that though Maduramycosis needs prolonged intensive antibacterial chemotherapy, even extensive disease can be successfully managed with conservative therapy.

Journal Article↗
PubMed2003

Acute compartment syndrome of the lower leg: changing concepts.

The acute limb compartment syndrome is caused by bleeding or edema in a closed muscle compartment surrounded by fascia and bone, leading to muscle and nerve ischemia. The value of fasciotomy has been demonstrated in the management of acute compartment syndrome, but if performed after a delay of 8 to 10 hours, it can prove to be a double-edged weapon, as necrotic muscle would get exposed leading to muscle infections and massive bleeding.

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