SEARCHING FOR DEBRIS DISKS AROUND SEVEN RADIO PULSARS

We report on our searches for debris disks around seven relatively nearby radio pulsars, which are isolated sources that were carefully selected as targets on the basis of our deep Ks-band imaging survey. The Ks images obtained with the 6.5m Baade Magellan Telescope at Las Campanas Observatory are analyzed together with the Spitzer/IRAC images at 4.5 and 8.0μm and the WISE images at 3.4, 4.6, 12, and 22μm. No infrared counterparts of these pulsars are found, with flux upper limits of ∼μJy at near-infrared (λ < 10μm) and ∼10–1000μJy at mid-infrared wavelengths (λ > 10 μm). The results of this search are discussed in terms of the efficiency of converting the pulsar spin-down energy to thermal energy and X-ray heating of debris disks, with a comparison made of the two magnetars 4U 0142+61 and 1E 2259+586, which are suggested to harbor a debris disk.published_or_final_versio

Quantum anti-Zeno effect without wave function reduction

We study the measurement-induced enhancement of the spontaneous decay (called quantum anti-Zeno effect) for a two-level subsystem, where measurements are treated as couplings between the excited state and an auxiliary state rather than the von Neumann's wave function reduction. The photon radiated in a fast decay of the atom, from the auxiliary state to the excited state, triggers a quasi-measurement, as opposed to a projection measurement. Our use of the term "quasi-measurement" refers to a "coupling-based measurement". Such frequent quasi-measurements result in an exponential decay of the survival probability of atomic initial state with a photon emission following each quasi-measurement. Our calculations show that the effective decay rate is of the same form as the one based on projection measurements. What is more important, the survival probability of the atomic initial state which is obtained by tracing over all the photon states is equivalent to the survival probability of the atomic initial state with a photon emission following each quasi-measurement to the order under consideration. That is because the contributions from those states with photon number less than the number of quasi-measurements originate from higher-order processes.Comment: 7 pages, 3 figure

Radio pulsar populations

The goal of this article is to summarize the current state of play in the field of radio pulsar statistics. Simply put, from the observed sample of objects from a variety of surveys with different telescopes, we wish to infer the properties of the underlying sample and to connect these with other astrophysical populations (for example supernova remnants or X-ray binaries). The main problem we need to tackle is the fact that, like many areas of science, the observed populations are often heavily biased by a variety of selection effects. After a review of the main effects relevant to radio pulsars, I discuss techniques to correct for them and summarize some of the most recent results. Perhaps the main point I would like to make in this article is that current models to describe the population are far from complete and often suffer from strong covariances between input parameters. That said, there are a number of very interesting conclusions that can be made concerning the evolution of neutron stars based on current data. While the focus of this review will be on the population of isolated Galactic pulsars, I will also briefly comment on millisecond and binary pulsars as well as the pulsar content of globular clusters and the Magellanic Clouds.Comment: 16 pages, 6 figures, to appear in Proceedings of ICREA Workshop on The High-Energy Emission from Pulsars and their Systems, Sant Cugat, Spain, 2010 April 12-16 (Springer

On the inverse Compton scattering model of radio pulsars

Some characteristics of the inverse Compton scattering (ICS) model are reviewed. At least the following properties of radio pulsars can be reproduced in the model: core or central emission beam, one or two hollow emission cones, different emission heights of these components, diverse pulse profiles at various frequencies, linear and circular polarization features of core and cones.Comment: 5 pages, no figures, LaTeX, a proceeding paper for Pacific Rim Conference on Stellar Astrophysics, Aug. 1999, HongKong, Chin

Hyaluronidase Coated Molecular Envelope Technology Nanoparticles Enhance Drug Absorption via the Subcutaneous Route

Parenteral chemotherapy is usually administered intravenously, although patient preference and health economics suggest the subcutaneous (sc) route could be an attractive alternative. However, due to the low aqueous solubility of hydrophobic drugs and injection volume limitations, the total amount of drug that can be administered in a single sc injection is frequently insufficient. We have developed hyaluronidase coated nanoparticles (NPs) that efficiently encapsulate such drugs, thus addressing both issues and allowing sufficient amounts of hydrophobic drug to be administered and absorbed effectively. CUDC-101, a poorly water-soluble multitargeted anticancer drug that simultaneously inhibits the receptor tyrosine kinases (RTKs) EGFR and HER2, as well as histone deacetylase (HDAC), was encapsulated in polymeric Molecular Envelope Technology (MET) NPs. The role of polymer chemistry, formulation parameters, and coating with hyaluronidase (HYD) on MET-CUDC-101 NP formulations was examined and optimized to yield high drug loading and colloidal stability, and, after freeze-drying, stable storage at room temperature for up to 90 days. The pharmacokinetic studies in healthy rats showed that plasma AUC0-24h after sc administration correlates tightly with formulation physical chemistry, specifically in vitro colloidal stability. Compared to uncoated NPs, the HYD-coating doubled the drug plasma exposure. In a murine A431 xenograft model, the coated HYD-MET-CUDC-101 NPs at a dose equivalent to 90 mg kg-1 CUDC-101 increased the survival time from 15 days (control animals treated with hyaluronidase alone) to 43 days. Polymer MET nanoparticles coated with hyaluronidase enabled the subcutaneous delivery of a hydrophobic drug with favorable therapeutic outcomes

A survey of qualitative spatial representations

Representation and reasoning with qualitative spatial relations is an important problem in artificial intelligence and has wide applications in the fields of geographic information system, computer vision, autonomous robot navigation, natural language understanding, spatial databases and so on. The reasons for this interest in using qualitative spatial relations include cognitive comprehensibility, efficiency and computational facility. This paper summarizes progress in qualitative spatial representation by describing key calculi representing different types of spatial relationships. The paper concludes with a discussion of current research and glimpse of future work

Adipokine Imbalance in the Pericardial Cavity of Cardiac and Vascular Disease Patients

Aim Obesity and especially hypertrophy of epicardial adipose tissue accelerate coronary atherogenesis. We aimed at comparing levels of inflammatory and atherogenic hormones from adipose tissue in the pericardial fluid and circulation of cardiovascular disease patients. Methods and Results Venous plasma (P) and pericardial fluid (PF) were obtained from elective cardiothoracic surgery patients (n = 37). Concentrations of leptin, adipocyte fatty acid-binding protein (AFABP) and adiponectin (APN) were determined by enzyme-linked immunosorbent assays (ELISA). The median concentration of leptin in PF (4.3 (interquartile range: 2.8-9.1) mu g/L) was comparable to that in P (5.9 (2.2-11) mu g/L) and these were significantly correlated to most of the same patient characteristics. The concentration of A-FABP was markedly higher (73 (28-124) versus 8.4 (5.2-14) mu g/L) and that of APN was markedly lower (2.8 (1.7-4.2) versus 13 (7.2-19) mg/L) in PF compared to P. APN in PF was unlike in P not significantly related to age, body mass index, plasma triglycerides or coronary artery disease. PF levels of APN, but not A-FABP, were related to the size of paracardial adipocytes. PF levels of APN and A-FABP were not related to the immunoreactivity of paracardial adipocytes for these proteins. Conclusion In cardiac and vascular disease patients, PF is enriched in A-FABP and poor in APN. This adipokine microenvironment is more likely determined by the heart than by the circulation or paracardial adipose tissue.published_or_final_versio

Facile Synthesis of High Quality Graphene Nanoribbons

Graphene nanoribbons have attracted attention for their novel electronic and spin transport properties1-6, and because nanoribbons less than 10 nm wide have a band gap that can be used to make field effect transistors. However, producing nanoribbons of very high quality, or in high volumes, remains a challenge. Here, we show that pristine few-layer nanoribbons can be produced by unzipping mildly gas-phase oxidized multiwalled carbon nanotube using mechanical sonication in an organic solvent. The nanoribbons exhibit very high quality, with smooth edges (as seen by high-resolution transmission electron microscopy), low ratios of disorder to graphitic Raman bands, and the highest electrical conductance and mobility reported to date (up to 5e2/h and 1500 cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the nanoribbons exhibit phase coherent transport and Fabry-Perot interference, suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2% of the starting raw nanotube soot material, which was significantly higher than previous methods capable of producing high quality narrow nanoribbons1. The relatively high yield synthesis of pristine graphene nanoribbons will make these materials easily accessible for a wide range of fundamental and practical applications.Comment: Nature Nanotechnology in pres

Operator entanglement of two-qubit joint unitary operations revisited: Schmidt number approach

Operator entanglement of two-qubit joint unitary operations is revisited. Schmidt number is an important attribute of a two-qubit unitary operation, and may have connection with the entanglement measure of the unitary operator. We found the entanglement measure of two-qubit unitary operators is classified by the Schmidt number of the unitary operators. The exact relation between the operator entanglement and the parameters of the unitary operator is clarified too.Comment: To appear in the Brazilian Journal of Physic