Constraining the mass density of free-floating black holes using razor-thin lensing arcs

Strong lensing of active galactic nuclei in the radio can result in razor-thin arcs, with a thickness of less than a milli-arcsecond, if observed at the resolution achievable with very long baseline interferometry (VLBI). Such razor-thin arcs provide a unique window on the coarseness of the matter distribution between source and observer. In this paper, we investigate to what extent such razor-thin arcs can constrain the number density and mass function of `free-floating' black holes, defined as black holes that do not, or no longer, reside at the centre of a galaxy. These can be either primordial in origin or arise as by-products of the evolution of super-massive black holes in galactic nuclei. When sufficiently close to the line of sight, free-floating black holes cause kink-like distortions in the arcs, which are detectable by eye in the VLBI images as long as the black hole mass exceeds $\sim 1000$ Solar masses. Using a crude estimate for the detectability of such distortions, we analytically compute constraints on the matter density of free-floating black holes resulting from null-detections of distortions along a realistic, fiducial arc, and find them to be comparable to those from quasar milli-lensing. We also use predictions from a large hydrodynamical simulation for the demographics of free-floating black holes that are not primordial in origin, and show that their predicted mass density is roughly four orders of magnitude below the constraints achievable with a single razor-thin arc.Comment: 17 pages, 13 figures, 1 table, comments welcom

Inclusion of predatory journals in Scopus is inflating scholars’ metrics and advancing careers

Copper (Cu) interconnect lines are widely used in advanced, high-density integrated circuits (ICs), large-area flat panel displays, and many nano and microelectronic and optoelectronic products. Compared with aluminum (Al), Cu has many advantages, such as the higher conductivity and longer lifetime. However, Cu is difficult to etch into fine lines using the conventional plasma etching method because the reaction product is nonvolatile. Another problem of Cu interconnect lines is that it has poor adhesion to the dielectric film unless an adhesion layer is used. Recently, Kuo’s group solved the etching problem with a novel room-temperature process that consumes the Cu thin film with a plasma reaction and then removes the reaction product with a liquid solution. This method has been used in the fabrication of ICs and TFT LCDs. One of the most critical issues in applying Cu lines in products is the reliability – electromigration (EM) lifetime prediction. As the IC keeps shrinking, the geometry effect on the lifetime of the thin Cu line is important especially for advanced products. Previously, Kuo’s group had studied temperature and mechanical bending effects on the Cu fine line’s lifetime. Geometry effects on the lifetime of the Al or Al-Cu alloy line have also been discussed before. However, there are few reports on the geometry effect on the Cu fine line prepared by the plasma-based etch process. In this research, the author investigated the relationship between the Cu line width or length and the EM failure time. The change of the line resistance with the stress time has also been studied. The capping layer effect is very important in multi-layer devices. There were some research studies on Cu capping layer before, i.e., Ag layer to protect Cu oxidation and SiN layer as interlayer dielectrics. However, few studies had been done on the TiW capping layer effect on plasma etched Cu lines. In this study, the TiW capping layer effect on lifetime has been studied

Study on laser surface micro-treatment of stainless steel

Laser surface micro-treatment refers to the use of appropriate laser energy to induce the surrounding gas and stainless steel reaction to produce a film or the use of large laser energy to manufacture micrometer grating. Using the principle of thin film interference or grating diffraction, the surface of stainless steel is marked with color, which can be used for information storage of metallurgical products. The relationship between laser line scanning and laser power is studied experimentally, the range of laser power density with color variation is obtained, and the optimal process parameters of uniform color are obtained

Study on laser surface micro-treatment of stainless steel

Laser surface micro-treatment refers to the use of appropriate laser energy to induce the surrounding gas and stainless steel reaction to produce a film or the use of large laser energy to manufacture micrometer grating. Using the principle of thin film interference or grating diffraction, the surface of stainless steel is marked with color, which can be used for information storage of metallurgical products. The relationship between laser line scanning and laser power is studied experimentally, the range of laser power density with color variation is obtained, and the optimal process parameters of uniform color are obtained

Herbal products in Italy: the thin line between phytotherapy, nutrition and parapharmaceuticals; a normative overview of the fastest growing market in Europe

The Italian herbal products market is the most prosperous in Europe. The proof is represented by the use of these products in several marketing categories, ranging from medicine to nutrition and cosmetics. Market and legislation in Italy are at the same time cause and consequence of this peculiar situation. In fact, the legislation on botanical food supplements in Italy is very permissive and at the same time the market shows an overall satisfaction of users and strong feedback in terms of consumption, which brings a widening use of medicinal plants, formerly the prerogative of pharmaceuticals, to other fields such as nutrition. This review summarizes the market and normative panorama of herbal products in Italy, highlighting the blurred boundaries of health indications, marketing authorizations and quality controls between herbal medicines and non pharmaceutical products, such as food supplements, cosmetics and other herbal-based “parapharmaceuticals”

Microwave-assisted YBa2Cu3O7 precursors : a fast and reliable method towards chemical precursors for superconducting films

Highly stable, pure, and anhydrous organometallic YBa2Cu3O7- (YBCO) precursor solutions were prepared by dissolving commercial YBCO powder in acetone by trifluoroacetic anhydride (TFAA) or a mixture of TFAA with propionic acid for low fluorine precursors. It is shown that compared to conventional oil bath heating reported in literature, the reaction to produce YBCO precursor occurs 72 times faster by microwave heating. More importantly, the formation of byproducts is suppressed, as shown by nuclear magnetic resonance (NMR) and mass spectrometry (MS). This approach allows a highly reproducible preparation of superconducting coatings which is of interest for low-cost manufacturing processes capable of large-scale production of the coated conductors via chemical solution deposition (CSD). This technology requires reliable and stable precursor solutions for continuous deposition. In this work, we obtained YBCO thin films on single-crystal substrates ((100)-LaAlO3) with a high critical current density (J(c)) of 3-4 MA/cm(2) in self-field at 77 K using TFA-based YBCO precursors and J(c) of 5-6 MA/cm(2) using low fluorine YBCO precursors

Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbide

We investigate the chemical composition and adhesion of chemical vapour deposited thin-film alumina on TiC using and extending a recently proposed nonequilibrium method of ab initio thermodynamics of deposition growth (AIT-DG) [Rohrer J and Hyldgaard P 2010 Phys. Rev. B 82 045415]. A previous study of this system [Rohrer J, Ruberto C and Hyldgaard P 2010 J. Phys.: Condens. Matter 22 015004] found that use of equilibrium thermodynamics leads to predictions of a non-binding TiC/alumina interface, despite the industrial use as a wear-resistant coating. This discrepancy between equilibrium theory and experiment is resolved by the AIT-DG method which predicts interfaces with strong adhesion. The AIT-DG method combines density functional theory calculations, rate-equation modelling of the pressure evolution of the deposition environment and thermochemical data. The AIT-DG method was previously used to predict prevalent terminations of growing or as-deposited surfaces of binary materials. Here we extent the method to predict surface and interface compositions of growing or as-deposited thin films on a substrate and find that inclusion of the nonequilibrium deposition environment has important implications for the nature of buried interfaces.Comment: 8 pages, 6 figures, submitted to J. Phys.: Condens. Matte

Strong Products of Hypergraphs: Unique Prime Factorization Theorems and Algorithms

It is well-known that all finite connected graphs have a unique prime factor decomposition (PFD) with respect to the strong graph product which can be computed in polynomial time. Essential for the PFD computation is the construction of the so-called Cartesian skeleton of the graphs under investigation. In this contribution, we show that every connected thin hypergraph H has a unique prime factorization with respect to the normal and strong (hypergraph) product. Both products coincide with the usual strong graph product whenever H is a graph. We introduce the notion of the Cartesian skeleton of hypergraphs as a natural generalization of the Cartesian skeleton of graphs and prove that it is uniquely defined for thin hypergraphs. Moreover, we show that the Cartesian skeleton of hypergraphs can be determined in O(|E|^2) time and that the PFD can be computed in O(|V|^2|E|) time, for hypergraphs H = (V,E) with bounded degree and bounded rank

Modelling incomplete fusion dynamics of weakly-bound nuclei at near-barrier energies

The classical dynamical model for reactions induced by weakly-bound nuclei at near-barrier energies is developed further. It allows a quantitative study of the role and importance of incomplete fusion dynamics in asymptotic observables, such as the population of high-spin states in reaction products as well as the angular distribution of direct alpha-production. Model calculations indicate that incomplete fusion is an effective mechanism for populating high-spin states, and its contribution to the direct alpha production yield diminishes with decreasing energy towards the Coulomb barrier. It also becomes notably separated in angles from the contribution of no-capture breakup events. This should facilitate the experimental disentanglement of these competing reaction processes.Comment: 12 pages, 7 figures (for better resolution figures please contact the author), Accepted in Journal of Physics