Electronic properties of metal induced gap states at insulator/metal interfaces -- dependence on the alkali halide and the possibility of excitonic mechanism of superconductivity

Motivated from the experimental observation of metal induced gap states (MIGS) at insulator/metal interfaces by Kiguchi {\it et al.} [Phys. Rev. Lett. {\bf 90}, 196803 (2003)], we have theoretically investigated the electronic properties of MIGS at interfaces between various alkali halides and a metal represented by a jellium with the first-principles density functional method. We have found that, on top of the usual evanescent state, MIGS generally have a long tail on halogen sites with a $p_z$-like character, whose penetration depth ($\lambda$) is as large as half the lattice constant of bulk alkali halides. This implies that $\lambda$, while little dependent on the carrier density in the jellium, is dominated by the lattice constant (hence by energy gap) of the alkali halide, where $\lambda_{\rm LiF} < \lambda_{\rm LiCl} < \lambda_{\rm LiI}$. We also propose a possibility of the MIGS working favorably for the exciton-mediated superconductivity.Comment: 7 pages, 9 figure

Ultrafast dynamics of coherences in the quantum Hall system

Using three-pulse four-wave-mixing optical spectroscopy, we study the ultrafast dynamics of the quantum Hall system. We observe striking differences as compared to an undoped system, where the 2D electron gas is absent. In particular, we observe a large off-resonant signal with strong oscillations. Using a microscopic theory, we show that these are due to many-particle coherences created by interactions between photoexcited carriers and collective excitations of the 2D electron gas. We extract quantitative information about the dephasing and interference of these coherences.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let

Hypofractionated stereotactic radiotherapy for intracranial meningioma: A systematic review

Background: The availability of image guidance and intensity modulation has led to the increasing use of hypofractionated stereotactic radiotherapy (hSRT) as an alternative to conventionally fractionated radiotherapy or radiosurgery for intracranial meningiomas (ICMs). As the safety and efficacy of this approach is not well characterized, we conducted a systematic review of the literature to assess the clinical outcomes of hSRT in the setting of ICMs. Methods: A systematic review of Medline and EMBASE databases was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included studies were retrospective or prospective series that examined an ICM population of ≥10 patients, delivered \u3e1 fraction of photon hSRT (≥2.5 Gy per fraction), and had a median follow-up of ≥2 years. Descriptive statistics were generated for included studies. Results: Of 1480 initial studies, 14 met eligibility criteria for inclusion, reporting on 630 patients (age range, 18-90) treated for 638 tumors. Primary radiotherapy was delivered in 37% of patients, 36% had radiation following surgery, and surgical details were unavailable for 27%. In 474 tumors assessed for radiologic response, 78% remained stable, 18% decreased in size, and 4% increased in size. Crude local control was 90%-100% as reported in 10 studies. The median late toxicity rate was 10%. The most common significant late toxicities were decreased visual acuity and new cranial neuropathy. Conclusions: With limited follow-up, the available literature suggests hSRT for ICMs has local control and toxicity profiles comparable to other radiotherapy approaches. Confirmation in larger patient cohorts with a longer duration of follow-up is required

Metal-semiconductor (semimetal) superlattices on a graphite sheet with vacancies

It has been found that periodically closely spaced vacancies on a graphite sheet cause a significant rearrange-ment of its electronic spectrum: metallic waveguides with a high density of states near the Fermi level are formed along the vacancy lines. In the direction perpendicular to these lines, the spectrum exhibits a semimetal or semiconductor character with a gap where a vacancy miniband is degenerated into impurity levels.Comment: 4 pages, 3 figure

Landau Damping in a 2D Electron Gas with Imposed Quantum Grid

Dielectric properties of semiconductor substrate with imposed two dimensional (2D) periodic grid of quantum wires or nanotubes (quantum crossbars, QCB) are studied. It is shown that a capacitive contact between QCB and semiconductor substrate does not destroy the Luttinger liquid character of the long wave QCB excitations. However, the dielectric losses of a substrate surface are drastically modified due to diffraction processes on the QCB superlattice. QCB-substrate interaction results in additional Landau damping regions of the substrate plasmons. Their existence, form and the density of losses are strongly sensitive to the QCB lattice constant.Comment: 9 pages, 12 eps-figure

Atomic-scale Interaction Dynamics in Few-layer Hexagonal Boron Nitride (h-BN)

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7-August 11, 201

Patient-reported reasons for declining or discontinuing statin therapy: Insights from the PALM registry

Background: Many adults eligible for statin therapy for cardiovascular disease prevention are untreated. Our objective was to investigate patient‐reported reasons for statin underutilization, including noninitiation, refusal, and discontinuation.Methods and Results: This study included the 5693 adults recommended for statin therapy in the PALM (Patient and Provider Assessment of Lipid Management) registry. Patient surveys evaluated statin experience, reasons for declining or discontinuing statins, and beliefs about statins and cardiovascular disease risk. Overall, 1511 of 5693 adults (26.5%) were not on treatment. Of those not on a statin, 894 (59.2%) reported never being offered a statin, 153 (10.1%) declined a statin, and 464 (30.7%) had discontinued therapy. Women (relative risk: 1.22), black adults (relative risk: 1.48), and those without insurance (relative risk: 1.38) were most likely to report never being offered a statin. Fear of side effects and perceived side effects were the most common reasons cited for declining or discontinuing a statin. Compared with statin users, those who declined or discontinued statins were less likely to believe statins are safe (70.4% of current users vs. 36.9% of those who declined and 37.4% of those who discontinued) or effective (86.3%, 67.4%, and 69.1%, respectively). Willingness to take a statin was high; 67.7% of those never offered and 59.7% of patients who discontinued a statin would consider initiating or retrying a statin.Conclusions: More than half of patients eligible for statin therapy but not on treatment reported never being offered one by their doctor. Concern about side effects was the leading reason for statin refusal or discontinuation. Many patients were willing to reconsider statin therapy if offered

Early age at first sexual intercourse and early pregnancy are risk factors for cervical cancer in developing countries

Early age at first sexual intercourse (AFSI) has long been associated with an increased risk of invasive cervical carcinoma (ICC). Age at first pregnancy (AFP) and ICC have been investigated less, although AFSI and AFP are strongly interrelated in most developing countries. A pooled analysis of case–control studies on ICC from eight developing countries with 1864 cases and 1719 controls investigated the roles of AFSI, AFP, and ICC risk. Age at first sexual intercourse, AFP and age at first marriage (AFM) were highly interrelated and had similar ICC risk estimates. Compared with women with AFSI ⩾21 years, the odds ratio (OR) of ICC was 1.80 (95% CI: 1.50–2.39) among women with AFSI 17–20 years and 2.31 (95% CI: 1.85–2.87) for AFSI ⩽16 years (P-trend <0.001). No statistical interaction was detected between AFSI and any established risk factors for ICC. The ICC risk was 2.4-fold among those who reported AFSI and AFP at ⩽16 years compared with those with AFSI and AFP at ⩾21 years. These data confirm AFSI and AFB as risk factors for ICC in eight developing countries, but any independent effects of these two events could not be distinguished