14,174 research outputs found
A practical, covariant puncture for second-order self-force calculations
Accurately modeling an extreme-mass-ratio inspiral requires knowledge of the
second-order gravitational self-force on the inspiraling small object.
Recently, numerical puncture schemes have been formulated to calculate this
force, and their essential analytical ingredients have been derived from first
principles. However, the \emph{puncture}, a local representation of the small
object's self-field, in each of these schemes has been presented only in a
local coordinate system centered on the small object, while a numerical
implementation will require the puncture in coordinates covering the entire
numerical domain. In this paper we provide an explicit covariant self-field as
a local expansion in terms of Synge's world function. The self-field is written
in the Lorenz gauge, in an arbitrary vacuum background, and in forms suitable
for both self-consistent and Gralla-Wald-type representations of the object's
trajectory. We illustrate the local expansion's utility by sketching the
procedure of constructing from it a numerically practical puncture in any
chosen coordinate system.Comment: 23 pages, 1 figure, final version to be published in Phys Rev
Epoxidation of Strained Alkenes Catalysed by (1,2-dimethyl-4(1H)pyridinone-3-olate)2MnIIICl
The mild epoxidation of strained alkenes using (DMPO)2MnCl catalyst (DMPO = 1,2-dimethyl-4(1H)-pyridinone-3-olate) in the presence of various oxidants was studied. Hydrogen peroxide and monopersulfate were found to be the best oxidants when used with imidazole in acetonitrile at 4 °C, with up to 94% conversion. Dismutation of hydrogen peroxide was also observed when used as an oxidant. The epoxidation using hydrogen peroxide or monoperoxysulfate appears to be mild and very selective for strained alkenes. A mechanism is proposed where imidazole is required for activation of the oxidant and where a detected MnV = O species is proposed as the active species. Competitive reaction between H2O2 and the substrate for the active species is proposed and homolytic vs heterolytic scissions of the Osingle bondO bond of the oxidant are discussed
QoE-Based Low-Delay Live Streaming Using Throughput Predictions
Recently, HTTP-based adaptive streaming has become the de facto standard for
video streaming over the Internet. It allows clients to dynamically adapt media
characteristics to network conditions in order to ensure a high quality of
experience, that is, minimize playback interruptions, while maximizing video
quality at a reasonable level of quality changes. In the case of live
streaming, this task becomes particularly challenging due to the latency
constraints. The challenge further increases if a client uses a wireless
network, where the throughput is subject to considerable fluctuations.
Consequently, live streams often exhibit latencies of up to 30 seconds. In the
present work, we introduce an adaptation algorithm for HTTP-based live
streaming called LOLYPOP (Low-Latency Prediction-Based Adaptation) that is
designed to operate with a transport latency of few seconds. To reach this
goal, LOLYPOP leverages TCP throughput predictions on multiple time scales,
from 1 to 10 seconds, along with an estimate of the prediction error
distribution. In addition to satisfying the latency constraint, the algorithm
heuristically maximizes the quality of experience by maximizing the average
video quality as a function of the number of skipped segments and quality
transitions. In order to select an efficient prediction method, we studied the
performance of several time series prediction methods in IEEE 802.11 wireless
access networks. We evaluated LOLYPOP under a large set of experimental
conditions limiting the transport latency to 3 seconds, against a
state-of-the-art adaptation algorithm from the literature, called FESTIVE. We
observed that the average video quality is by up to a factor of 3 higher than
with FESTIVE. We also observed that LOLYPOP is able to reach a broader region
in the quality of experience space, and thus it is better adjustable to the
user profile or service provider requirements.Comment: Technical Report TKN-16-001, Telecommunication Networks Group,
Technische Universitaet Berlin. This TR updated TR TKN-15-00
Supermax’s Kryptonite? \u3cem\u3eWilkinson v. Austin\u3c/em\u3e: The Due Process Challenge to Ohio’s Super-Maximum Security Prison
This note discusses the Supreme Court’s holding in Wilkinson that OSP’s system for inmate placement in its Supermax facility does not violate the Equal Protection Clause. Part II will summarize OSP’s purpose and condition, and will focus on Ohio’s New Policy regarding inmate placement. Part III will examine Supreme Court precedent and the Court’s conclusions of law in determining whether inmates have a protected liberty interest in avoiding assignment to OSP and the due process implications of the inmate selection process to OSP. Part IV will question the Supreme Court’s disregard of the adverse mental effects in inmates subjected to the extreme isolation conditions within Supermax prisons. Finally, Part V will analyze the likely impact of the Wilkinson decision on other jurisdictions in their development of fair inmate placement procedures for their Supermax facilities
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