5,763 research outputs found
Emergence of skyrmion lattices and bimerons in chiral magnetic thin films with nonmagnetic impurities
Skyrmions are topologically protected field structures with particlelike characteristics that play important roles in several areas of science. Recently, skyrmions have been directly observed in chiral magnets. Here, we investigate the effects of pointlike nonmagnetic impurities on the distinct initial states (random or helical ones) and on the formation of the skyrmion crystal in a discrete lattice. Using Monte Carlo techniques, we have found that even a small percentage of spin vacancies present in the chiral magnetic thin film considerably affects the skyrmion order. The main effects of impurities are somewhat similar to thermal effects. The presence of these spin vacancies also induces the formation of bimerons in both the helical and skyrmion states. We also investigate how adjacent impurities forming a hole affect the skyrmion crystal
Checking Interaction-Based Declassification Policies for Android Using Symbolic Execution
Mobile apps can access a wide variety of secure information, such as contacts
and location. However, current mobile platforms include only coarse access
control mechanisms to protect such data. In this paper, we introduce
interaction-based declassification policies, in which the user's interactions
with the app constrain the release of sensitive information. Our policies are
defined extensionally, so as to be independent of the app's implementation,
based on sequences of security-relevant events that occur in app runs. Policies
use LTL formulae to precisely specify which secret inputs, read at which times,
may be released. We formalize a semantic security condition, interaction-based
noninterference, to define our policies precisely. Finally, we describe a
prototype tool that uses symbolic execution to check interaction-based
declassification policies for Android, and we show that it enforces policies
correctly on a set of apps.Comment: This research was supported in part by NSF grants CNS-1064997 and
1421373, AFOSR grants FA9550-12-1-0334 and FA9550-14-1-0334, a partnership
between UMIACS and the Laboratory for Telecommunication Sciences, and the
National Security Agenc
Mapeamento das épocas aptas para o plantio de milho consorciado com braquiária na segunda safra agrícola no Brasil.
bitstream/item/95971/1/circ-187.pd
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Patient-reported financial barriers to adherence to treatment in neurology
OBJECTIVE: Many effective medical therapies are available for treating neurological diseases, but these therapies tend to be expensive and adherence is critical to their effectiveness. We used patient-reported data to examine the frequency and determinants of financial barriers to medication adherence among individuals treated for neurological disorders.
PATIENTS AND METHODS: Patients completed cross-sectional surveys on iPads as part of routine outpatient care in a neurology clinic. Survey responses from a 3-month period were collected and merged with administrative sources of demographic and clinical information (eg, insurance type). We explored the association between patient characteristics and patient-reported failure to refill prescription medication due to cost in the previous 12 months, termed here as "nonadherence".
RESULTS: The population studied comprised 6075 adults who were presented between July and September 2015 for outpatient neurology appointments. The mean age of participants was 56 (standard deviation: 18) years, and 1613 (54%) were females. The patients who participated in the surveys (2992, 49%) were comparable to nonparticipants with respect to gender and ethnicity but more often identified English as their preferred language (94% vs 6%, p<0.01). Among respondents, 9.8% (n=265) reported nonadherence that varied by condition. These patients were more frequently Hispanic (16.7% vs 9.8% white, p=0.01), living alone (13.9% vs 8.9% cohabitating, p<0.01), and preferred a language other than English (15.3% vs 9.4%, p=0.02).
CONCLUSION: Overall, the magnitude of financial barriers to medication adherence appears to vary across neurological conditions and demographic characteristics
Proving Safety with Trace Automata and Bounded Model Checking
Loop under-approximation is a technique that enriches C programs with
additional branches that represent the effect of a (limited) range of loop
iterations. While this technique can speed up the detection of bugs
significantly, it introduces redundant execution traces which may complicate
the verification of the program. This holds particularly true for verification
tools based on Bounded Model Checking, which incorporate simplistic heuristics
to determine whether all feasible iterations of a loop have been considered.
We present a technique that uses \emph{trace automata} to eliminate redundant
executions after performing loop acceleration. The method reduces the diameter
of the program under analysis, which is in certain cases sufficient to allow a
safety proof using Bounded Model Checking. Our transformation is precise---it
does not introduce false positives, nor does it mask any errors. We have
implemented the analysis as a source-to-source transformation, and present
experimental results showing the applicability of the technique
A Formalized Extension of the Substitution Lemma in Coq
The substitution lemma is a renowned theorem within the realm of
lambda-calculus theory and concerns the interactional behaviour of the
metasubstitution operation. In this work, we augment the lambda-calculus's
grammar with an uninterpreted explicit substitution operator, which allows the
use of our framework for different calculi with explicit substitutions. Our
primary contribution lies in verifying that, despite these modifications, the
substitution lemma continues to remain valid. This confirmation was achieved
using the Coq proof assistant. Our formalization methodology employs a nominal
approach, which provides a direct implementation of the alpha-equivalence
concept. The strategy involved in variable renaming within the proofs presents
a challenge, specially on ensuring an exploration of the implications of our
extension to the grammar of the lambda-calculus.Comment: In Proceedings FROM 2023, arXiv:2309.1295
On the multiplicity of the hyperelliptic integrals
Let be an Abelian integral, where
is a hyperelliptic polynomial of Morse type, a
horizontal family of cycles in the curves , and a polynomial
1-form in the variables and . We provide an upper bound on the
multiplicity of , away from the critical values of . Namely: $ord\
I(t) \leq n-1+\frac{n(n-1)}{2}\deg \omega <\deg H=n+1\delta(t)nHHI(t)\gamma(t)\textbf C^ n\gamma(t)\omegaHI(t)\{H=t\}
\subseteq \textbf C^2\omega\gamma(t)\textbf C^{n+1}ord I(t)\deg \omega$.Comment: 18 page
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