Piyush Kumar

Thickness and electric-field-dependent polarizability and dielectric constant in phosphorene

Based on extensive first-principles calculations, we explore the thickness-dependent effective dielectric constant and slab polarizability of few-layer black phosphorene. We find that the dielectric constant in ultrathin phosphorene is thickness-dependent and it can be further tuned by applying an out-of-plane electric field. The decreasing dielectric constant with reducing number of layers of phosphorene is a direct consequence of the lower permittivity of the outer layers and the increasing surface-to-volume ratio. We also show that the slab polarizability depends linearly on the number of layers, implying a nearly constant polarizability per phosphorus atom. Our calculation of the thickness- and electric-field-dependent dielectric properties will be useful for designing and interpreting transport experiments in gated phosphorene devices, wherever electrostatic effects such as capacitance and charge screening are important.

Gliosarcoma: an audit from a single institution in India of 24 post-irradiated cases over 15 years.

BACKGROUND Gliosarcomas (GS) are biphasic brain tumors composed of glioblastoma multiforme (GBM) and sarcomatous component. Therapeutic approaches include maximum surgical decompression with postoperative radiotherapy. Outcomes in gliosarcoma are poor despite multimodality management. AIMS To analyze the outcome in patients of GS treated in our institute over a period of 15 years and compare it with GBM treated during the same period. SETTINGS AND DESIGN Clinical records of the post-irradiated GS patients and GBM patients seen between 1990 and 2004 were retrieved. MATERIALS AND METHODS Demographic and treatment variables were evaluated for their influence on overall survival (OS). The survival outcomes of GBM and GS treated during the same period were also compared. STATISTICAL ANALYSIS Univariate analysis was carried out using the Kaplan-Meier method and tested using log-rank test for significance. RESULTS During these 15 years, 24 evaluable GS patients were treated as compared to 251 evaluable patients of GBM. There was a slight male preponderance in GS (14 males vs.10 females) with a median age of 50 years. All patients underwent surgery followed by post-operative radiotherapy (median dose of 60 Gy). None of the patient or treatment related factors were found to be significantly influencing their OS. Median OS in GS was 7.3 months compared to 7.5 months in GBM patients (P = 0.790). CONCLUSIONS The OS appears to be similar for GS and GBM. None of the demographic variables appeared to prognosticate the survivals of GS.

Malignant peripheral nerve sheath tumor of the occipital region: case report.

OBJECTIVEA rare case of a malignant peripheral nerve sheath tumor of the occipital region is presented. The role of postoperative radiotherapy in such cases is reviewed. CLINICAL PRESENTATIONA 36-year-old man presented with a small spongy swelling in the posterior aspect of the cranium since childhood. The swelling gradually increased for 2 years and then rapidly over the next 7 months. There were no associated symptoms of headache, vomiting, vertigo, focal weakness, or visual impairment. INTERVENTIONA small occipital craniectomy for total excision of the tumor was attempted. However, as a result of intracranial extension to the transverse sinus, the tumor could not be completely excised. Local radiotherapy to a dose of 59.4 Gy in 33 fractions over 6.5 weeks was delivered to the residual microscopic disease in the posterior part of the cranium. The patient has been followed up regularly for the past 28 months and continues to remain asymptomatic. CONCLUSIONAn aggressive malignant peripheral nerve sheath tumor of an atypical site such as the scalp, in which complete surgery may not always be possible, could benefit from postoperative radiotherapy. A dose of approximately 60 Gy could be effectively delivered with a satisfactory outcome.

Anisotropic plasmons, excitons, and electron energy loss spectroscopy of phosphorene

In this article, we explore the anisotropic electron energy loss spectrum (EELS) in monolayer phosphorene based on ab-initio time dependent density functional theory calculations. Similar to black phosphorous, the EELS of undoped monolayer phosphorene is characterized by anisotropic excitonic peaks for energies in vicinity of the bandgap, and by interband plasmon peaks for higher energies. On doping, an additional intraband plasmon peak also appears for energies within the bandgap. Similar to other two dimensional systems, the intraband plasmon peak disperses as

Human papillomavirus confers radiosensitivity in cancer cervix: a hypothesis toward a possible restoration of apoptotic pathways based on clinical outcomes

\omega_{\rm pl} \propto \sqrt{q}

Chordoma with increased prolactin levels (pseudoprolactinoma) mimicking pituitary adenoma: a case report with review of the literature.

in both the zigzag and armchair directions in the long wavelength limit, and deviates for larger wavevectors. The anisotropy of the long wavelength plasmon intraband dispersion is found to be inversely proportional to the square root of the ratio of the effective masses:

MALIGNANT PERIPHERAL NERVE SHEATH TUMOR OF THE OCCIPITAL REGION

\omega_{\rm pl}(q \hat{y})/\omega_{\rm pl}(q \hat{x}) = \sqrt{m_x/m_y}

Comparison of Electron Beam Transmission of Different Energies With Two Different Block Materials at Different Placement Positions Within the Applicator

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Thickness and Stacking Dependent Polarizability and Dielectric Constant of Graphene–Hexagonal Boron Nitride Composite Stacks

AIM To evaluate if high baseline local human papillomavirus (HPV) titer confers radiosensitivity in cancer cervix. A hypothesis is proposed to explain the clinical outcomes. MATERIALS & METHODS 121 serial HPV titers from cervical smears of 21 patients were estimated during radiotherapy (RT) and correlated with RT dose-response curves, local response and local disease-free survival (LDFS). RESULTS Local response (p = 0.04) and LDFS (p = 0.06) were better in high HPV than low HPV baseline group. On multivariate analysis, RT doses for 50% tumor regression and baseline HPV titer were the only predictors for LDFS. CONCLUSION Serial reductions of HPV titers following RT could restore the HPV induced temporarily downregulated p53 and pRb apoptotic pathways resulting in radiosensitivity of these tumors.

2-Arylcyclopropylmethanol as a substitute for homoallyl aryl alcohol in the construction of cis-2,6-disubstituted tetrahydropyran: synthesis of (±)-centrolobine

The article deals with a rare case of chordoma with increased prolactin levels. It could often result in a diagnostic dilemma and problems in differentiating it from a pituitary adenoma.