The 2009 outburst of accreting millisecond pulsar IGR J17511-3057 as observed by SWIFT and RXTE

The twelfth accretion-powered millisecond pulsar, IGR J17511-3057, was discovered in September 2009. In this work we study its spectral and timing properties during the 2009 outburst based on Swift and RXTE data. Our spectral analysis of the source indicates only slight spectral shape evolution during the entire outburst. The equivalent width of the iron line and the apparent area of the blackbody emission associated with the hotspot at the stellar surface both decrease significantly during the outburst. This is consistent with a gradual receding of the accretion disc as the accretion rate drops. The pulse profile analysis shows absence of dramatic shape evolution with a moderate decrease in pulse amplitude. This behaviour might result from a movement of the accretion column footprint towards the magnetic pole as the disc retreats. The time lag between the soft and the hard energy pulses increase by a factor of two during the outburst. A physical displacement of the centroid of the accretion shock relative to the blackbody spot or changes in the emissivity pattern of the Comptonization component related to the variations of the accretion column structure could cause this evolution. We have found that IGR J17511-3057 demonstrates outburst stages similar to those seen in SAX J1808.4-3658. A transition from the "slow decay" into the "rapid drop" stage, associated with the dramatic flux decrease, is also accompanied by a pulse phase shift which could result from an appearance of the secondary spot due to the increasing inner disc radius.Comment: 12 pages, 10 figures, MNRAS, in press. Title correcte

MOCCA-SURVEY Database I: Assessing GW kick retention fractions for BH-BH mergers in globular clusters

Anisotropy of gravitational wave (GW) emission results in a net momentum gained by the black hole (BH) merger product, leading to a recoil velocity up to $\sim10^3\text{ km s}^{-1}$, which may kick it out of a globular cluster (GC). We estimate GW kick retention fractions of merger products assuming different models for BH spin magnitude and orientation (MS0 - random, MS1 - spin as a function of mass and metalicity, MS2 - constant value of $0.5$). We check how they depend on BH-BH merger time and properties of the cluster. We analyze the implications of GW kick retention fractions on intermediate massive BH (IMBH) formation by repeated mergers in a GC. We also calculate final spin of the merger product, and investigate how it correlates with effective spin of the binary. We used data from MOCCA (MOnte Carlo Cluster simulAtor) GC simulations to get a realistic sample of BH-BH mergers, assigned each BH spin value according to a studied model, and calculated recoil velocity and final spin based on most recent theoretical formulas. We discovered that for physically motivated models, GW kick retention fractions are about $30\%$ and display small dependence on assumptions about spin, but are much more prone to cluster properties. In particular, we discovered a strong dependence of GW kick retention fractions on cluster density. We also show that GW kick retention fractions are high in final life stages of the cluster, but low at the beginning. Finally, we derive formulas connecting final spin with effective spin for primordial binaries, and with maximal effective spin for dynamical binaries.Comment: 13 pages, 9 figures, accepted for publication in MNRA

Single-single gravitational-wave captures in globular clusters: Eccentric deci-Hertz sources observable by DECIGO and Tian-Qin

We study the formation rate of binary black hole mergers formed through gravitational-wave emission between unbound, single black holes in globular clusters. While the formation of these binaries in very dense systems such as galactic nuclei has been well studied, we show here that this process can operate in lower-density stellar systems as well, forming binaries at a rate similar to other proposed pathways for creating eccentric mergers. Recent advances in post-Newtonian cluster dynamics indicate that a large fraction of dynamically-assembled binary black holes merge inside their host clusters during weak and strong binary-single and binary-binary interactions, and that these systems may retain measurable eccentricities as they travel through the LIGO and LISA sensitivity bands. Using an analytic approach to modeling binary black holes from globular clusters, we show that the formation of merging binaries from previously unbound black holes can operate at a similar rate to mergers forming during strong binary encounters, and that these binaries inhabit a unique region of the gravitational-wave frequency space which can be identified by proposed deci-Hertz space-based detectors.Comment: 16 pages, 5 figures. Accepted version (PRD

Developing a multiple glazing system to minimize transmission of direct insolation for particular latitudes

Too often, in the last 50 years, the energy-thrift lessons of vernacular architecture have been forgotten or ignored. In the Middle East, many recently-designed commercial buildings, with large areas of glazing, incur excessively high electricity-demands to provide energy for the required air-conditioning plant. One way of reducing the magnitude of this demand is through better window design. A new glazing system is proposed that utilizes the insertion of a clear glazing element within the cavity of a double glazed window. The main objective of this system is to achieve acceptable levels of daylight within a building by attempting to maintain the diffuse component of insolation while reducing the penetration of direct component by using the increased reflectivity of these materials with the angle of incidence of the direct beam component of solar irradiation. By using clear glazing materials the proposed system attempts to achieve acceptable performance without the need for elaborate and expensive coatings or substrates. Because solar geometry varies with latitude a varying performance of glazing systems is expected with current glazing systems. However, the suggested system utilizes an optimal angle for overall daylighting and thermal performance that relates to the particular solar geometry of interest, New software is also developed to assess the performance of the suggested system; this involved examining all the modes of heat transfer through the entire glazing system. Results then were assessed to calculate the optimal angle of the element that corresponds to the solar geometry of particular latitude. Such proposal takes a new perspective, once it is acknowledged that though different forms of advanced glazing systems currently are being used to inhibit the penetration of direct solar radiation, still the main disadvantages of such advanced glazing systems are that they are relatively expensive and would reduce the penetration of a considerable part of the daylight entering the space.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Synthesis of biosourced silica-Ag nanocomposites and amalgamation reaction with mercury in aqueous solutions

This paper focuses on the synthesis of a new silver nanocomposite adsorbent derived from rice husk as raw material. The synthesis is based on triethoxysilane chemistry and the reduction of silver without the aid of reductant chemicals. The derived AgNPs@SiO2 nanocomposites are fully characterized and then used for the removal of mercury (II) from aqueous solutions. The results demonstrated that the affinity of the composite for mercury is high and the removal mechanism is adsorption accompanied by a redox reaction between mercury and silver followed by the formation of calomel and amalgams between silver and mercury. The silver-mercury reaction is complex, and its stoichiometry seems to scale with the silver content. Besides the importance of the surface reactions, the successful implementation of biosourced silica for mercury removal from water is useful for the development of strategies for the valorization of agricultural waste and boosts the concept of circular economy and bioeconomy

Investigation of molecular docking, biological and DFT studies of Schiff base transition metal complexes

1666-1675The Schiff base ligand obtained from the reaction of 2-amino-3-hydroxypyridine, 2,4,6-trihydroxy benzaldehyde is described. Cu(II), Ni(II), Co(II), and Zn(II)complexes have been analyzed by various spectroscopic techniques like FT-IR, UV-visible, mass spectrometry and NMR. Based on spectral data octahedral geometry has been assigned to the complexes. In the present study the prepared Schiff base ligand and all the metal complexes have been synthesized and studied for their in vitro anti diabetic, antioxidant and antibacterial activities. Geometry optimization and the chemical stability and reactivity of complexes clearly understood with help of frontier molecular orbital’s (HOMO-LUMO) using B3LYP/LACVP++ basis sets based on density functional theory. Furthermore, Molecular docking study of the Schiff base ligand and their metal (II) complexes showed good binding score with human pancreatic α-amylase (PDB: 1HNY)