3,662 research outputs found
An implementation of Deflate in Coq
The widely-used compression format "Deflate" is defined in RFC 1951 and is
based on prefix-free codings and backreferences. There are unclear points about
the way these codings are specified, and several sources for confusion in the
standard. We tried to fix this problem by giving a rigorous mathematical
specification, which we formalized in Coq. We produced a verified
implementation in Coq which achieves competitive performance on inputs of
several megabytes. In this paper we present the several parts of our
implementation: a fully verified implementation of canonical prefix-free
codings, which can be used in other compression formats as well, and an elegant
formalism for specifying sophisticated formats, which we used to implement both
a compression and decompression algorithm in Coq which we formally prove
inverse to each other -- the first time this has been achieved to our
knowledge. The compatibility to other Deflate implementations can be shown
empirically. We furthermore discuss some of the difficulties, specifically
regarding memory and runtime requirements, and our approaches to overcome them
The Correlation between EEG Signals as Measured in Different Positions on Scalp Varying with Distance
© 2018 The Author(s). Published by Elsevier B. V. This is an open access article under the CC BY-NC-ND license https://creativecommons.org/licenses/by-nc-nd/4.0/Biomedical signals such as electroencephalogram (EEG) are the time varying signal, and different position of electrodes give different time varying signals. There might be a correlation between these signals. It is likely that the correlation is related to the actual position of electrodes. In this paper, we show that correlation is related to the physical distance between electrodes as measured. This finding is independent of participants and brain hemisphere. Our results indicate that the EEG signal is not transmitted via neurons but through white matter in a brain.Peer reviewedFinal Published versio
The Eruption from a Sigmoidal Solar Active Region on 2005 May 13
This paper presents a multiwavelength study of the M8.0 flare and its
associated fast halo CME that originated from a bipolar active region NOAA
10759 on 2005 May 13. The source active region has a conspicuous sigmoid
structure at TRACE 171 A channel as well as in the SXI soft X-ray images, and
we mainly concern ourselves with the detailed process of the sigmoid eruption
as evidenced by the multiwavelength data ranging from Halpha, WL, EUV/UV,
radio, and hard X-rays (HXRs). The most important finding is that the flare
brightening starts in the core of the active region earlier than that of the
rising motion of the flux rope. This timing clearly addresses one of the main
issues in the magnetic eruption onset of sigmoid, namely, whether the eruption
is initiated by an internal tether-cutting to allow the flux rope to rise
upward or a flux rope rises due to a loss of equilibrium to later induce tether
cutting below it. Our high time cadence SXI and Halpha data shows that the
first scenario is relevant to this eruption. As other major findings, we have
the RHESSI HXR images showing a change of the HXR source from a confined
footpoint structure to an elongated ribbon-like structure after the flare
maximum, which we relate to the sigmoid-to-arcade evolution. Radio dynamic
spectrum shows a type II precursor that occurred at the time of expansion of
the sigmoid and a drifting pulsating structure in the flare rising phase in
HXR. Finally type II and III bursts are seen at the time of maximum HXR
emission, simultaneous with the maximum reconnection rate derived from the
flare ribbon motion in UV. We interpret these various observed properties with
the runaway tether-cutting model proposed by Moore et al. in 2001.Comment: 10 pages, 10 figures, The Astrophysical Journal, accepted July, 200
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Life-Expectancy Disparities Among Adults With HIV in the United States and Canada: The Impact of a Reduction in Drug- and Alcohol-Related Deaths Using the Lives Saved Simulation Model.
Improvements in life expectancy among people living with human immunodeficiency virus (PLWH) receiving antiretroviral treatment in the United States and Canada might differ among key populations. Given the difference in substance use among key populations and the current opioid epidemic, drug- and alcohol-related deaths might be contributing to the disparities in life expectancy. We sought to estimate life expectancy at age 20 years in key populations (and their comparison groups) in 3 time periods (2004-2007, 2008-2011, and 2012-2015) and the potential increase in expected life expectancy with a simulated 20% reduction in drug- and alcohol-related deaths using the novel Lives Saved Simulation model. Among 92,289 PLWH, life expectancy increased in all key populations and comparison groups from 2004-2007 to 2012-2015. Disparities in survival of approximately a decade persisted among black versus white men who have sex with men and people with (vs. without) a history of injection drug use. A 20% reduction in drug- and alcohol-related mortality would have the greatest life-expectancy benefit for black men who have sex with men, white women, and people with a history of injection drug use. Our findings suggest that preventing drug- and alcohol-related deaths among PLWH could narrow disparities in life expectancy among some key populations, but other causes of death must be addressed to further narrow the disparities
An Optimization Approach to the Ordering Phase of an Attended Home Delivery Service
Attended Home Delivery (AHD) systems are used whenever a supplying company
offers online shopping services that require that customers must be present
when their deliveries arrive. Therefore, the supplying company and the customer
must both agree on a time window, which ideally is rather short, during which
delivery is guaranteed. Typically, a capacitated Vehicle Routing Problem with
Time Windows forms the underlying optimization problem of the AHD system. In
this work, we consider an AHD system that runs the online grocery shopping
service of an international grocery retailer. The ordering phase, during which
customers place their orders through the web service, is the computationally
most challenging part of the AHD system. The delivery schedule must be built
dynamically as new orders are placed. We propose a solution approach that
allows to (non-stochastically) determine which delivery time windows can be
offered to potential customers. We split the computations of the ordering phase
into four key steps. For performing these basic steps we suggest both a
heuristic approach and a hybrid approach employing mixed-integer linear
programs. In an experimental evaluation we demonstrate the efficiency of our
approaches
Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for Pharmacogenetics-Guided Warfarin Dosing: 2017 Update
This document is an update to the 2011 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2C9 and VKORC1 genotypes and warfarin dosing. Evidence from the published literature is presented for CYP2C9, VKORC1, CYP4F2, and rs12777823 genotype-guided warfarin dosing to achieve a target international normalized ratio of 2-3 when clinical genotype results are available. In addition, this updated guideline incorporates recommendations for adult and pediatric patients that are specific to continental ancestry
A Self-Reference False Memory Effect in the DRM Paradigm: Evidence from Eastern and Western Samples
It is well established that processing information in relation to oneself (i.e., selfreferencing) leads to better memory for that information than processing that same information in relation to others (i.e., other-referencing). However, it is unknown whether self-referencing also leads to more false memories than other-referencing. In the current two experiments with European and East Asian samples, we presented participants the Deese-Roediger/McDermott (DRM) lists together with their own name or other peopleâs name (i.e., âTrumpâ in Experiment 1 and âLi Mingâ in Experiment 2). We found consistent results across the two experiments; that is, in the self-reference condition, participants had higher true and false memory rates compared to those in the other-reference condition. Moreover, we found that selfreferencing did not exhibit superior mnemonic advantage in terms of net accuracy compared to other-referencing and neutral conditions. These findings are discussed in terms of theoretical frameworks such as spreading activation theories and the fuzzytrace theory. We propose that our results reflect the adaptive nature of memory in the sense that cognitive processes that increase mnemonic efficiency may also increase susceptibility to associative false memories
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