1,558 research outputs found
On the multiplicity of ALMA Compact Array counterparts of far-infrared bright quasars
We present ALMA Atacama Compact Array (ACA) 870 micron continuum maps of 28
infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4,
the largest such sample ever observed with ALMA. The ACA detections are centred
on the SDSS coordinates to within 1 arcsec for about 80 per cent of the sample.
Larger offsets indicate that the far-infrared (FIR) emission detected by
Herschel might come from a companion source. The majority of the objects (about
70 per cent) have unique ACA counterparts within the SPIRE beam down to 3-4
arcsec resolution. Only 30 per cent of the sample shows clear evidence for
multiple sources with secondary counterparts contributing to the total 870
micron flux within the SPIRE beam to at least 25 per cent. We discuss the
limitations of the data based on simulated pairs of point-like sources at the
resolution of the ACA and present an extensive comparison of our findings with
recent works on the multiplicities of sub-millimetre galaxies. We conclude
that, despite the coarse resolution of the ACA, our data support the idea that,
for a large fraction of FIR-bright quasars, the sub-mm emission comes from
single sources. Our results suggest that, on average, optically bright quasars
with strong FIR emission are not triggered by early-stage mergers but are,
instead, together with their associated star formation rates, the outcome of
either late-stage mergers or secular processes.Comment: 16 pages, 10 figure
Observations on the Natural History of the Green Anaconda (Eunectes murinus Linnaeus, 1758) in the Venezuelan Llanos: An Ecotourism Perspective
Observations on the Natural History of the Green Anaconda (Eunectes murinus Linnaeus, 1758) in the Venezuelan Llanos: An Ecotourism Perspective
An effective action for asymptotically safe gravity
Asymptotically safe theories of gravitation have received great attention in
recent times. In this framework an effective action embodying the basic
features of the renormalized flow around the non-gaussian fixed point is
derived and its implications for the early universe are discussed. In
particular, a "landscape" of a countably infinite number of cosmological
inflationary solutions characterized by an unstable de Sitter phase lasting for
a large enough number of e-folds is found.Comment: 5 pages, to appear as a Rapid Communication in Physical Review
As relações de equivalência como critério de análise da pertinência científica de categorias analíticas
El objetivo del presente trabajo es proponer las relaciones de equivalencia como criterio estructural o de ordenamiento analítico mediante el cual se puedan delimitar las funciones del conocimiento requeridas en una actividad científica. Se parte de considerar al conocimiento como un fenómeno estudiado por la psicología y cuya explicación requiere de dar cuenta de la manera en que se establecen, organizan y actualizan las funciones conductuales o del conocimiento. De este modo, se considera que las tareas de igualación a la muestra permiten comprender el modo de abstraer las categorías analíticas que estructuran científicamente el conocimiento de la realidad. Cuando se usan estos procedimiento, se derivan nuevas relaciones sin la necesidad de un entrenamiento directo y que no pueden explicarse con base en principios de generalización de estímulos, sino, más bien, como relaciones equivalentes diferenciadas mediante los entrenamientos previos y que adquieren un cierre en una categoría analítica cuando se abstraen los criterios categoriales o, si se quiere, cuando estas relaciones se nominan. Así, al categorizarse o nominarse, estas trascienden la situación -porque nominar se entiende como un ajuste a criterios convencionales- y una vez que las interacciones situacionales se nominan, regulan todas las prácticas sociales, incluidas las prácticas del conocimiento científico.O objetivo deste trabalho é propor as relações de equivalência como critério estrutural ou de ordenamento analítico pelo qual possam ser delimitadas as funções do conhecimento requeridas numa atividade científica. Parte-se de considerar o conhecimento como um fenômeno estudado pela psicologia e cuja explicação requer evidenciar a maneira na qual são estabelecidas, organizadas e atualizadas as funções comportamentais ou do conhecimento. Desse modo, considera-se que as tarefas de igualação à amostra permitem compreender o modo de abstrair as categorias analíticas que estruturam cientificamente o conhecimento da realidade. Quando são usados esses procedimentos, são derivadas novas relações que, sem a necessidade de um treinamento direto, não podem ser explicadas com base em princípios de generalização de estímulos, mas sim como relações equivalentes diferenciadas mediante os treinamentos prévios e que adquirem uma delimitação numa categoria analítica quando são abstraídos os critérios categoriais ou, se se quiser, quando essas relações são nominadas. Assim, ao serem categorizadas ou nominadas, elas transcendem a situação -porque nominar se entende como um ajuste a critérios convencionais- e, uma vez que as interações situacionais são nominadas, regulam todas as práticas sociais, incluídas as práticas do conhecimento científico.The aim of this paper is to propose equivalence relations as a structural criterion or analytical order, through which the functions of knowledge required in a scientific activity are delimited. It begins by considering knowledge as a phenomenon studied by psychology, whose explanation requires giving an account of the way in which such behavioral or knowledge functions are established, organized and updated. It is considered that the procedures of matching-to-sample allow understanding the way of abstracting the analytical categories that scientifically structure the knowledge of reality. When using these procedures, new relationships are derived that without the need for direct training, cannot be explained based on principles of stimulus generalization, but rather as equivalent relations differentiated through previous training. They get a closure in an analytical category, once the categorical criteria are abstracted or if desired, when these relationships are nominated. And when categorized or nominated, they transcend the situation, since nominating is understood as an adjustment to conventional criteria. Once situational interactions are nominated, they regulate all social practices, including practices of scientific knowledge
Functional relationship between the matrix proteins of feline and simian immunodeficiency viruses
AbstractTo investigate the functional relationship between the matrix (MA) proteins of feline and simian immunodeficiency viruses (FIV and SIV, respectively), we generated chimeric proviruses in which the MA-coding region of an SIV infectious molecular clone was partially or fully replaced by its FIV counterpart. Chimeric SIV proviruses containing the amino-terminal 36 residues or the central and carboxy-terminal regions of the FIV MA assembled into virions as efficiently as wild-type SIV. However, the resulting virions were noninfectious in single-cycle infectivity assays. Furthermore, a chimeric SIV provirus containing the entire FIV MA was found to be severely impaired in virion production due to inefficient membrane binding of the chimeric Gag polyprotein. Interestingly, the assembly defective phenotype of this chimeric Gag precursor could be reversed either by introducing the G31K/G33K double amino acid substitution in the FIV-derived MA domain or by coexpression with wild-type SIV Gag. Of note, a chimeric FIV provirus expressing the SIV MA not only assembled into particles as efficiently as wild-type FIV, but also replicated in feline T cells with wild-type kinetics. Our results thus provide novel information about the functional homology between the MA proteins of distantly related lentiviruses
Rapid and MR-Independent IK1 activation by aldosterone during ischemia-reperfusion
In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious
effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac
mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone
modulates K+ currents involved in the holding of the resting membrane potential (RMP).
The aim of this study was to assess the electrophysiological impact of aldosterone on IK1
current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone”
using right rabbit ventricle and standard microelectrode technique followed by cell-attached
recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments,
aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential
duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4ms to
116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature
ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely,
potassium canrenoate 100 nmol/L and RU 28318 1 μmol/l alone did not affect AP
parameters and premature ventricular contractions occurrence (except Vmax which was
decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone
induced a RMP hyperpolarization, evoking an implication of a K+ current involved in the
holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly
activated (within 6.2±0.4 min) a 30 pS K+-selective current, inward rectifier, with pharmacological
and biophysical properties consistent with the IK1 current (NPo =1.9±0.4 in control vs
NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318,
a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non
specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating
a MR-independent IK1 activation. In this ischemia-reperfusion context, aldosterone induced
rapid and MR-independent deleterious effects including an arrhythmia substrate (increased
APD90 dispersion) and triggered activities (increased premature ventricular contractions
occurrence on reperfusion) possibly related to direct IK1 activation
Quantum Interference in Single Molecule Electronic Systems
We present a general analytical formula and an ab initio study of quantum
interference in multi-branch molecules. Ab initio calculations are used to
investigate quantum interference in a benzene-1,2-dithiolate (BDT) molecule
sandwiched between gold electrodes and through oligoynes of various lengths. We
show that when a point charge is located in the plane of a BDT molecule and its
position varied, the electrical conductance exhibits a clear interference
effect, whereas when the charge approaches a BDT molecule along a line normal
to the plane of the molecule and passing through the centre of the phenyl ring,
interference effects are negligible. In the case of olygoynes, quantum
interference leads to the appearance of a critical energy , at which the
electron transmission coefficient of chains with even or odd numbers of
atoms is independent of length. To illustrate the underlying physics, we derive
a general analytical formula for electron transport through multi-branch
structures and demonstrate the versatility of the formula by comparing it with
the above ab-initio simulations. We also employ the analytical formula to
investigate the current inside the molecule and demonstrate that large counter
currents can occur within a ring-like molecule such as BDT, when the point
charge is located in the plane of the molecule. The formula can be used to
describe quantum interference and Fano resonances in structures with branches
containing arbitrary elastic scattering regions connected to nodal sites.Comment: 12 pages, 11 figure
Food security and migration in Africa: A validation of theoretical links using case studies from literature
The connection between food security and migration is increasingly discussed by both international agencies and academic literature. However, despite several improvements, we continue to know little about the complex causal-effect relations that link these aspects and, in particular, how much migration patterns are affected by food security issues and how much, as a feedback, migration can affect food security, on both the origin and destination areas. This paper aims firstly to draw a general framework of this nexus and then to validate it using empirical literature on the African continent. A few common points can be emphasized for the continent: due to structural and familiar characteristics, different strategies based on opportunity costs or risk minimization (including food security aspects) may emerge; individuals often migrate following household strategies; multi-nodal households are emerging; land grabbing and land tenure security represent important drivers to be considered; emergencies or critical situations often cause the erosion of women rights. In many situations, the poverty trap prevents most food insecure households to leave marginal lands
Tipos de implantes activos de oído medio
Active middle ear implants are classified as piezoelectric implants,
which use the properties of piezoelectric materials.
There are two types of piezoelectric implants: monomorphic
and dimorphic; electromagnetic transduction uses a magnet,
usually a rare earth magnet (e.g. samarium cobalt) and an
energizing coil. This magnetic field causes the magnet to vibrate,
which in turn, through the tympanic-ossicular chain,
causes movement of the cochlear fluids. Electromechanical
transduction is a variation of electromagnetic transduction
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