Gamma Ray Bursts with peculiar temporal asymmetry

Based on the study of temporal asymmetry of 631 gamma ray bursts from the BATSE 3B catalog by Link and Epstein [Ap J 466, 764 (1996)], we identify the population of bursts whose rising times are longer than their decays, thus showing atypical profiles. We analyse their sky distribution, morphology, time-space clustering and other average properties and compare them with those associated with the bulk of the bursts. We show how most of the peculiar bursts analysed are consistent with recent fireball models, but a fraction of bursts ($\sim 4$% of the total sample) appear to be inconsistent.Comment: mn style (included in the submission), 4 figures that must be printed separately. Submitted to Monthly Notices of RA

In search for natural wormholes

We have investigated 631 time profiles of gamma ray bursts from the BATSE database searching for observable signatures produced by microlensing events related to natural wormholes. The results of this first search of topologically nontrivial objects in the Universe can be used to constrain their number and mass.Comment: Mod. Phys. Lett. A. (in press) Latex (revtex style) with no figure

Neutrinos from Accreting Neutron Stars

The magnetospheres of accreting neutron stars develop electrostatic gaps with huge potential drops. Protons and ions, accelerated in these gaps along the dipolar magnetic field lines to energies greater than 100 TeV, can impact onto a surrounding accretion disc. A proton-induced cascade so develops, and $\nu$-emission is produced from charged pion decays. Using GEANT4, a computer code that tracks particles produced in high energy collisions, we have calculated the resulting $\nu$-spectrum with extensive disc shower simulations. We show that the $\nu$-spectrum produced out of the proton beam is a power law. We use this result to propose accretion-powered X-ray binaries (with highly magnetized neutron stars) as a new population of point-like $\nu$-sources for km-scale detectors, such as ICECUBE. As a particular example we discuss the case of A0535+26. We show that ICECUBE should find A0535+26 to be a periodic $\nu$-source: one for which the formation and loss of its accretion disc can be fully detected. Finally, we briefly comment on the possibility that smaller telescopes, like AMANDA, could also detect A0535+26 by folding observations with the orbital period.Comment: 7 pages, 5 figures. Updates to match accepted version in Astrophys.

Wormholes, Gamma Ray Bursts and the Amount of Negative Mass in the Universe

In this essay, we assume that negative mass objects can exist in the extragalactic space and analyze the consequences of their microlensing on light from distant Active Galactic Nuclei. We find that such events have very similar features to some observed Gamma Ray Bursts and use recent satellite data to set an upper bound to the amount of negative mass in the universe.Comment: Essay awarded ``Honorable Mention'' in the Gravity Foundation Research Awards, 199

Abordagem de uma conceituação do custo

In this paper, elements of the analysis of the concept of cost that transcend the limits traditionally found between the economic and accounting disciplines are offered. The problem of the weakness of the concept of cost and the need to clarify it and expand its scope in the perspective of current pedagogical, economic and financial needs is evident. Experience and tradition have led to many notions and concepts hibernate without clarity, breadth and accuracy adequate to be understood, learned and taught. One of those concepts is cost. Everything indicates that this concept lacks an adequate theoretical structure capable of constituting a conceptual framework that supports the uses, the daily practices and the multiplicity of applications that can be derived from it. Product of a bibliographic exploration, this research focuses on the interpretation of notions, concepts and definitions present in the literature, to provide a conceptual precision that avoids misunderstandings in the use of language and promotes a conceptual and not only functional learning.En este escrito se ofrecen elementos de análisis del concepto de costo que trascienden los límites que tradicionalmente se han tejido entre las disciplinas económica y contable. Se hace evidente la problemática de la debilidad del concepto de costo y la necesidad de dilucidarlo y ampliar su alcance en la perspectiva de las necesidades pedagógicas, económicas y financieras actuales. La experiencia y la tradición han conducido a que muchas nociones y conceptos hibernen sin claridad, amplitud y precisión adecuados para ser comprendidos, aprendidos y enseñados. El concepto de costo es uno de estos. Todo indica que este concepto carece de una adecuada estructura teórica capaz de constituir un entramado conceptual que sostenga los usos, las prácticas cotidianas y la multiplicidad de aplicaciones que pueden derivarse de este. Producto de una exploración bibliográfica, esta investigación se centra en la interpretación de nociones, conceptos y definiciones presentes en la literatura, para allegar una precisión conceptual que evite los malentendidos en el uso del lenguaje y se promueva un aprendizaje conceptual y no solamente funcional.  Cet article propose des éléments d’analyse de la notion de coût qui dépassent les frontières qui ont traditionnellement été tissées entre les disciplines économique et comptable. Le problème de la faiblesse de la notion de coût et la nécessité del’élucider et d’en élargir la portée dans la perspective des besoins pédagogiques économiques et financiers actuels sont évidents. L’expérience et la tradition ont conduit à l’hibernation de nombreuses notions et concepts sans clarté, ampleur et précision suffisantes pour être compris, appris et enseignés. La notion decoût est l’une d’entre elles. Tout indique que ce concept manque d’une structure théorique appropriée capable de constituer un cadre conceptuel qui soutienne les usages, les pratiques quotidiennes et la multiplicité des applications qui peuvent endécouler. Cette recherche est le fruit d’une exploration bibliographique et se concentre sur l’interprétation des notions, concepts et définitions présents dans la littérature, pour atteindre une précision conceptuelle qui évite les malentendus dans l’utilisation du langage et favorise l’apprentissage conceptuel et non seulement fonctionnel.Este artigo oferece elementos de análise do conceito de custo que ultrapassam aos limites que tradicionalmente ocorreram entre as disciplinas econômicas e contábeis. Fazem-se evidentes os problemas da debilidade do conceito de custo e a necessidade de elucidar e expandir seu alcance na perspectiva das atuais necessidades pedagógicas, econômicas e financeiras. A experiência e a tradição levaram a que muitas noções e conceitos estarão hibernando sem a clareza, amplitude e precisão adequadas para ser compreendidos, aprendidos e ensinados. O conceito de custo é um desses. Tudo indica que este conceito não tem uma estrutura teórica adequada capaz de estabelecer um quadro conceitual que mantém os usos, as práticas cotidianas e a multiplicidade de aplicações que podem ser derivados deste. Esta investigação decorre de uma exploração bibliográfica e centra-se na interpretação de noções, conceitos e definições presentes na literatura, para alcançar uma precisão conceitual para evitar mal-entendidos no uso da linguagem e que seja promovido um aprendizagem conceitual e não apenas funcional

Interaction between lactose and cadmium chloride in aqueous solutions as seen by diffusion coefficients measurements

Diffusion coefficients of an aqueous system containing cadmium chloride 0.100 mol · dm−3 and lactose at different concentrations at 25 °C have been measured, using a conductimetric cell and an automatic apparatus to follow diffusion. The cell relies on an open-ended capillary method and a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at recorded times. From these results and by ab initio calculations, it was possible to obtain a better understanding of the effect of lactose on transport of cadmium chloride in aqueous solutions

Quantum Size Effects in the Magnetic Susceptibility of a Metallic Nanoparticle

We theoretically study quantum size effects in the magnetic response of a spherical metallic nanoparticle (e.g. gold). Using the Jellium model in spherical coordinates, we compute the induced magnetic moment and the magnetic susceptibility for a nanoparticle in the presence of a static external magnetic field. Below a critical magnetic field the magnetic response is diamagnetic, whereas above such field the magnetization is characterized by sharp, step-like increases of several tenths of Bohr magnetons, associated with the Zeeman crossing of energy levels above and below the Fermi sea. We quantify the robustness of these regimes against thermal excitations and finite linewidth of the electronic levels. Finally, we propose two methods for experimental detection of the quantum size effects based on the coupling to superconducting quantum interference devices.Comment: 5+6 pages, 3+3 figure

Influence of Surface Chemistry on the Electrochemical Performance of Biomass-Derived Carbon Electrodes for its Use as Supercapacitors

The following are available online at https://www.mdpi.com/1996-1944/12/15/2458/s1, Figure S1. N2 adsorption and desorption isotherms at 77K of CK-series samples. Figure S2: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Custard apple tree wood (CK-Serie). Figure S3: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Fig tree wood (FK-Serie). Figure S4: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Olive tree wood (OK-Serie).first_page settings Open AccessFeature PaperArticle Influence of Surface Chemistry on the Electrochemical Performance of Biomass-Derived Carbon Electrodes for its Use as Supercapacitors by Abdelhakim Elmouwahidi 1 [OrcID] , Esther Bailón-García 1, Luis A. Romero-Cano 2 [OrcID] , Ana I. Zárate-Guzmán 3, Agustín F. Pérez-Cadenas 1,* [OrcID] and Francisco Carrasco-Marín 1 [OrcID] 1 Research Group in Carbon Materials, Inorganic Chemistry Department, Faculty of Sciences, University of Granada, Campus Fuente Nueva s/n. 18071 Granada, Spain 2 Facultad de Ciencias Químicas, Universidad Autónoma de Guadalajara, Av. Patria 1201, Zapopan, Jalisco C. P. 45129, Mexico 3 Centro de Investigación y Desarrollo Tecnológico en Electroquímica (CIDETEQ) S.C., Parque Tecnológico Sanfandila, Pedro Escobedo, Querétaro 760703, Mexico * Author to whom correspondence should be addressed. Materials 2019, 12(15), 2458; https://doi.org/10.3390/ma12152458 Received: 28 June 2019 / Revised: 31 July 2019 / Accepted: 1 August 2019 / Published: 2 August 2019 (This article belongs to the Special Issue Element-Doped Functional Carbon-based Materials) Download PDF Browse Figures Cite This Paper Abstract Activated carbons prepared by chemical activation from three different types of waste woods were treated with four agents: melamine, ammonium carbamate, nitric acid, and ammonium persulfate, for the introduction of nitrogen and oxygen groups on the surface of materials. The results indicate that the presence of the heteroatoms enhances the capacitance, energy density, and power density of all samples. The samples treated with ammonium persulfate show the maximum of capacitance of 290 F g−1 while for the melamine, ammonium carbamate, and nitric acid treatments, the samples reached the maximum capacitances values of 283, 280, and 455 F g−1 respectively. This remarkable electro-chemical performance, as the high specific capacitances can be due to several reasons: i) The excellent and adequate textural characteristics makes possible a large adsorption interface for electrolyte to form the electrical double layer, leading to a great electrochemical double layer capacitance. ii) The doping with hetero-atoms enhances the surface interaction of these materials with the aqueous electrolyte, increasing the accessibility of electrolyte ions. iii) The hetero-atoms groups can also provide considerable pseudo-capacitance improving the overall capacitance.This work was supported by FEDER and Spanish MINECO (grant number CTQ-2013-44789-R); and Junta de Andalucía (grant numbers P12-RNM-2892, RNM172)

Sneddon syndrome a case report and literature review

Sneddon’s syndrome (SS) is characterized by livedo racemosa (LR) or reticularis and recurrent ischemic strokes. At the skin and brain level a non-inflammatory thrombotic vasculopathy is observed. Almost 80% of cases are women around 40 years old. The most accepted etiological proposal is an autoimmune and inflammatory mechanism versus the presence of thrombophilia. Neurological manifestations occur in 3 phases: prodromal symptoms (headache, dizziness, and vertigo), recurrent strokes, and early-onset dementia. Livedo racemosa has been reported to precede strokes by more than 10 years. Treatment is mainly based on secondary prophylaxis preventing a stroke with antiplatelet and antithrombotic agents. The neuropsychiatric prognosis is relatively poor with deficits in concentration, attention, visual perception, and visuospatial skills

The Mysterious Ultrahigh Energy Cosmic Ray Clustering

We examine the correlation between compact radio quasars (redshifts in the range $z = 0.3 - 2.2$) and the arrival direction of ultrahigh energy cosmic rays forming clusters. Our Monte Carlo simulation reveals a statistically significant correlation on the AGASA sample: the chance probability of this effect being less than 1%. The implications of this result on the origin of ultrahigh energy cosmic rays are discussed.Comment: Updates to match journal versio