3,591 research outputs found
Representing Network Trust and Using It to Improve Anonymous Communication
Motivated by the effectiveness of correlation attacks against Tor, the
censorship arms race, and observations of malicious relays in Tor, we propose
that Tor users capture their trust in network elements using probability
distributions over the sets of elements observed by network adversaries. We
present a modular system that allows users to efficiently and conveniently
create such distributions and use them to improve their security. The major
components of this system are (i) an ontology of network-element types that
represents the main threats to and vulnerabilities of anonymous communication
over Tor, (ii) a formal language that allows users to naturally express trust
beliefs about network elements, and (iii) a conversion procedure that takes the
ontology, public information about the network, and user beliefs written in the
trust language and produce a Bayesian Belief Network that represents the
probability distribution in a way that is concise and easily sampleable. We
also present preliminary experimental results that show the distribution
produced by our system can improve security when employed by users; further
improvement is seen when the system is employed by both users and services.Comment: 24 pages; talk to be presented at HotPETs 201
Innovativeness and Innovation: Implications for the Renewable Materials Supply Chain
innovativeness, innovation, supply chain management, triple bottom line, corporate social responsibility, Agribusiness, Agricultural Finance, Demand and Price Analysis, Financial Economics, Q10, Q27, Q42, Q47,
Self-consistent predictions for LIER-like emission lines from post-AGB stars
Early type galaxies (ETGs) frequently show emission from warm ionized gas.
These Low Ionization Emission Regions (LIERs) were originally attributed to a
central, low-luminosity active galactic nuclei. However, the recent discovery
of spatially-extended LIER emission suggests ionization by both a central
source and an extended component that follows a stellar-like radial
distribution. For passively-evolving galaxies with old stellar populations, hot
post-Asymptotic Giant Branch (AGB) stars are the only viable extended source of
ionizing photons. In this work, we present the first prediction of LIER-like
emission from post-AGB stars that is based on fully self-consistent stellar
evolution and photoionization models. We show that models where post-AGB stars
are the dominant source of ionizing photons reproduce the nebular emission
signatures observed in ETGs, including LIER-like emission line ratios in
standard optical diagnostic diagrams and H equivalent widths of order
0.1-3 angstroms. We test the sensitivity of LIER-like emission to the details
of post-AGB models, including the mass loss efficiency and convective mixing
efficiency, and show that line strengths are relatively insensitive to post-AGB
timescale variations. Finally, we examine the UV-optical colors of the models
and the stellar populations responsible for the UV-excess observed in some
ETGs. We find that allowing as little as 3% of the HB population to be
uniformly distributed to very hot temperatures (30,000 K) produces realistic UV
colors for old, quiescent ETGs.Comment: ApJ accepted. 20 pages, 8 figure
Women in higher education: A brief report on stress during COVID-19
Higher education institutions have evolved into a more stressful environment. Women have been experiencing higher levels of stress than their male counterparts. With higher education adopting to the onset of the pandemic, this brief report studied womenâs perceived stress in relation to perceived organizational and supervisory support, and age during times of crisis. In an era of social distancing, quarantines, and lockdowns, the findings suggest that womenâs perceived stress is negatively related to age, perceived organizational support, and perceived supervisory support. Society as we once knew it pre-pandemic will never be the same. Higher education is inevitably going to have to manage the aftermath, a new normal that can only be as effective as the employees that help keep the organization running
Efficient Gravitational Wave Searches with Pulsar Timing Arrays using Hamiltonian Monte Carlo
Pulsar timing arrays (PTAs) detect low-frequency gravitational waves (GWs) by
looking for correlated deviations in pulse arrival times. Current Bayesian
searches use Markov Chain Monte Carlo (MCMC) methods, which struggle to sample
the large number of parameters needed to model the PTA and GW signals. As the
data span and number of pulsars increase, this problem will only worsen. An
alternative Monte Carlo sampling method, Hamiltonian Monte Carlo (HMC),
utilizes Hamiltonian dynamics to produce sample proposals informed by
first-order gradients of the model likelihood. This in turn allows it to
converge faster to high dimensional distributions. We implement HMC as an
alternative sampling method in our search for an isotropic stochastic GW
background, and show that this method produces equivalent statistical results
to similar analyses run with standard MCMC techniques, while requiring 100-200
times fewer samples. We show that the speed of HMC sample generation scales as
where is the number of
pulsars, compared to for MCMC methods. These
factors offset the increased time required to generate a sample using HMC,
demonstrating the value of adopting HMC techniques for PTAs.Comment: 9 pages, 5 figures, submitted to Physical Review
Vascular Alteration with Postural Change as Observed Using the Anterior Tibial Artery: A Pilot Study
Plantar fasciopathy and plantar fasciosis are common lower extremity conditions. Vascular health is an important aspect of plantar fascia health. Footwear choices are thought to influence lower extremity vascular flow, but how the anterior tibial artery is affected by purely postural changes over time is unknown. PURPOSE: To observe the anterior tibial artery vascular alterations over a ten-minute period after transitioning from a sitting to a standing position while barefoot. METHODS: Nine participants (age= 23.8yrs ±2.5, height= 176.0cm ±8.0, weight= 69.8kg ±10.2) were recruited from Brigham Young University for a single 30-minute visit. The participants had no previous lower extremity injuries within 6 months. The individualâs dominant foot arch height index was recorded, and the participant had a 3-lead ECG placed on their trunk. A Logic Fortis machine with an L8-18i probe was used to capture pulse wave (PW) images of the anterior tibial artery of the dominant foot. The participant sat barefoot on an elevated platform for five minutes and baseline PW was recorded. The participant then stood on the platform for 11 total minutes. PW images were captured once at the end of every minute for the first five minutes and a final PW measurement was captured after ten minutes of standing. A paired t-test was used to compare standing time points to baseline (α=0.05). RESULTS: After standing, time-averaged mean velocity (TAMean) significantly dropped through minutes one (pCONCLUSION: Blood flow through the anterior tibial artery is significantly altered with postural changes likely through cardiovascular responses. Vascular recovery is observed after three minutes while the average increase in vascular response occurs around ten minutes
Implementation of an efficient Bayesian search for gravitational wave bursts with memory in pulsar timing array data
The standard Bayesian technique for searching pulsar timing data for
gravitational wave (GW) bursts with memory (BWMs) using Markov Chain Monte
Carlo (MCMC) sampling is very computationally expensive to perform. In this
paper, we explain the implementation of an efficient Bayesian technique for
searching for BWMs. This technique makes use of the fact that the signal model
for Earth-term BWMs (BWMs passing over the Earth) is fully factorizable. We
estimate that this implementation reduces the computational complexity by a
factor of 100. We also demonstrate that this technique gives upper limits
consistent with published results using the standard Bayesian technique, and
may be used to perform all of the same analyses that standard MCMC techniques
can perform.Comment: 19 pages, 3 figures, 1 table. Submitted to Astrophysical Journa
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