408 research outputs found
Lawyers and the New Institutionalism
Drawing on the sociological theory of new institutionalism, this essay explores the ethical behavior and decision-making of lawyers by reference to the organizational context in which lawyers work. As the new institutionalism predicts, lawyers develop powerful assimilated informal norms, practices, habits, and customs that sometimes complement and other times supplant formal substantive law on professional conduct. Structural choices in practice settings influence the creation of these informal norms. The challenge for the legal profession, and particularly academics who teach legal ethics, is how to prepare law students and lawyers better to recognize and analyze the norms in their practice setting and to encourage management choices within practice settings that more likely provide norms that enhance rather than degrade ethical decision-making
Lynx X-Ray Observatory: An Overview
Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2- to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget
Outbursts in two new cool pulsating DA white dwarfs
The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with = 10,780 ± 140 K and = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with = 11,190 ± 170 K and = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts
Mechanisms explaining transitions between tonic and phasic firing in neuronal populations as predicted by a low dimensional firing rate model
Several firing patterns experimentally observed in neural populations have
been successfully correlated to animal behavior. Population bursting, hereby
regarded as a period of high firing rate followed by a period of quiescence, is
typically observed in groups of neurons during behavior. Biophysical
membrane-potential models of single cell bursting involve at least three
equations. Extending such models to study the collective behavior of neural
populations involves thousands of equations and can be very expensive
computationally. For this reason, low dimensional population models that
capture biophysical aspects of networks are needed.
\noindent The present paper uses a firing-rate model to study mechanisms that
trigger and stop transitions between tonic and phasic population firing. These
mechanisms are captured through a two-dimensional system, which can potentially
be extended to include interactions between different areas of the nervous
system with a small number of equations. The typical behavior of midbrain
dopaminergic neurons in the rodent is used as an example to illustrate and
interpret our results.
\noindent The model presented here can be used as a building block to study
interactions between networks of neurons. This theoretical approach may help
contextualize and understand the factors involved in regulating burst firing in
populations and how it may modulate distinct aspects of behavior.Comment: 25 pages (including references and appendices); 12 figures uploaded
as separate file
COSMIC: An Ethernet-based Commensal, Multimode Digital Backend on the Karl G. Jansky Very Large Array for the Search for Extraterrestrial Intelligence
The primary goal of the search for extraterrestrial intelligence (SETI) is to
gain an understanding of the prevalence of technologically advanced beings
(organic or inorganic) in the Galaxy. One way to approach this is to look for
technosignatures: remotely detectable indicators of technology, such as
temporal or spectral electromagnetic emissions consistent with an artificial
source. With the new Commensal Open-Source Multimode Interferometer Cluster
(COSMIC) digital backend on the Karl G. Jansky Very Large Array (VLA), we aim
to conduct a search for technosignatures that is significantly more
comprehensive, more sensitive, and more efficient than previously attempted.
The COSMIC system is currently operational on the VLA, recording data, and
designed with the flexibility to provide user-requested modes. This paper
describes the hardware system design, the current software pipeline, and plans
for future development.Comment: 30 pages, 17 figures. Accepted for publication in A
Recommended from our members
A multithickness sea ice model accounting for sliding friction
A multithickness sea ice model explicitly accounting for the ridging and sliding friction contributions to sea ice stress is developed. Both ridging and sliding contributions depend on the deformation type through functions adopted from the Ukita and Moritz kinematic model of floe interaction. In contrast to most previous work, the ice strength of a uniform ice sheet of constant ice thickness is taken to be proportional to the ice thickness raised to the 3/2 power, as is revealed in discrete element simulations by Hopkins. The new multithickness sea ice model for sea ice stress has been implemented into the Los Alamos “CICE” sea ice model code and is shown to improve agreement between model predictions and observed spatial distribution of sea ice thickness in the Arctic
Stellar Astrophysics and Exoplanet Science with the Maunakea Spectroscopic Explorer (MSE)
The Maunakea Spectroscopic Explorer (MSE) is a planned 11.25-m aperture
facility with a 1.5 square degree field of view that will be fully dedicated to
multi-object spectroscopy. A rebirth of the 3.6m Canada-France-Hawaii Telescope
on Maunakea, MSE will use 4332 fibers operating at three different resolving
powers (R ~ 2500, 6000, 40000) across a wavelength range of 0.36-1.8mum, with
dynamical fiber positioning that allows fibers to match the exposure times of
individual objects. MSE will enable spectroscopic surveys with unprecedented
scale and sensitivity by collecting millions of spectra per year down to
limiting magnitudes of g ~ 20-24 mag, with a nominal velocity precision of ~100
m/s in high-resolution mode. This white paper describes science cases for
stellar astrophysics and exoplanet science using MSE, including the discovery
and atmospheric characterization of exoplanets and substellar objects, stellar
physics with star clusters, asteroseismology of solar-like oscillators and
opacity-driven pulsators, studies of stellar rotation, activity, and
multiplicity, as well as the chemical characterization of AGB and extremely
metal-poor stars.Comment: 31 pages, 11 figures; To appear as a chapter for the Detailed Science
Case of the Maunakea Spectroscopic Explore
f(R) theories
Over the past decade, f(R) theories have been extensively studied as one of
the simplest modifications to General Relativity. In this article we review
various applications of f(R) theories to cosmology and gravity - such as
inflation, dark energy, local gravity constraints, cosmological perturbations,
and spherically symmetric solutions in weak and strong gravitational
backgrounds. We present a number of ways to distinguish those theories from
General Relativity observationally and experimentally. We also discuss the
extension to other modified gravity theories such as Brans-Dicke theory and
Gauss-Bonnet gravity, and address models that can satisfy both cosmological and
local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in
Relativity, Published version, Comments are welcom
Unraveling Twisty Linear Polarization Morphologies in Black Hole Images
We investigate general relativistic magnetohydrodynamic simulations (GRMHD)
to determine the physical origin of the twisty patterns of linear polarization
seen in spatially resolved black hole images and explain their morphological
dependence on black hole spin. By characterising the observed emission with a
simple analytic ring model, we find that the twisty morphology is determined by
the magnetic field structure in the emitting region. Moreover, the dependence
of this twisty pattern on spin can be attributed to changes in the magnetic
field geometry that occur due to the frame dragging. By studying an analytic
ring model, we find that the roles of Doppler boosting and lensing are
subdominant. Faraday rotation may cause a systematic shift in the linear
polarization pattern, but we find that its impact is subdominant for models
with strong magnetic fields and modest ion-to-electron temperature ratios.
Models with weaker magnetic fields are much more strongly affected by Faraday
rotation and have more complicated emission geometries than can be captured by
a ring model. However, these models are currently disfavoured by the recent EHT
observations of M87*. Our results suggest that linear polarization maps can
provide a probe of the underlying magnetic field structure around a black hole,
which may then be usable to indirectly infer black hole spins. The generality
of these results should be tested with alternative codes, initial conditions,
and plasma physics prescriptions.Comment: 25 pages, 19 figure
Phospho-regulation, nucleotide binding and ion access control in potassium-chloride cotransporters
Potassium-coupled chloride transporters (KCCs) play crucial roles
in regulating cell volume and intracellular chloride concentration.
They are characteristically inhibited under isotonic conditions via
phospho-regulatory sites located within the cytoplasmic termini.
Decreased inhibitory phosphorylation in response to hypotonic cell
swelling stimulates transport activity, and dysfunction of this
regulatory process has been associated with various human
diseases. Here, we present cryo-EM structures of human KCC3b
and KCC1, revealing structural determinants for phosphoregulation in both N- and C-termini. We show that phosphomimetic KCC3b is arrested in an inward-facing state in which
intracellular ion access is blocked by extensive contacts with the
N-terminus. In another mutant with increased isotonic transport
activity, KCC1D19, this interdomain interaction is absent, likely
due to a unique phospho-regulatory site in the KCC1 N-terminus.
Furthermore, we map additional phosphorylation sites as well as a
previously unknown ATP/ADP-binding pocket in the large Cterminal domain and show enhanced thermal stabilization of
other CCCs by adenine nucleotides. These findings provide fundamentally new insights into the complex regulation of KCCs and
may unlock innovative strategies for drug development
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