1,246 research outputs found
Nash Codes for Noisy Channels
This paper studies the stability of communication protocols that deal with
transmission errors. We consider a coordination game between an informed sender
and an uninformed decision maker, the receiver, who communicate over a noisy
channel. The sender's strategy, called a code, maps states of nature to
signals. The receiver's best response is to decode the received channel output
as the state with highest expected receiver payoff. Given this decoding, an
equilibrium or "Nash code" results if the sender encodes every state as
prescribed. We show two theorems that give sufficient conditions for Nash
codes. First, a receiver-optimal code defines a Nash code. A second, more
surprising observation holds for communication over a binary channel which is
used independently a number of times, a basic model of information
transmission: Under a minimal "monotonicity" requirement for breaking ties when
decoding, which holds generically, EVERY code is a Nash code.Comment: More general main Theorem 6.5 with better proof. New examples and
introductio
Antimicrobial activity of the fiber produced by “pochote” Ceiba aesculifolia subsp. parvifolia
Background: The cotton-like fiber from the fruit of Pochote (Ceiba aesculifolia subsp. parvifolia) can be applied to wounds for healing purposes. As microorganisms can infect wounds and hamper the wound healing process, the aim of this study was to determine the antimicrobial activity and chemical composition of the methanolic extract of Pochote fiber.Materials and Methods: The methanolic extract was tested against bacteria and fungi. For bacteria, the Kirby-Baüer disc diffusion and broth dilution methods were employed to determine the MIC and MBC. In addition, bactericidal kinetic curves were generated. The antifungal activity was determined by the radial diffusion method. The antioxidant activity, total phenolic content, and the flavonoid content were determined. Bioassay guided fractionation was also performed.Results: The methanolic extract showed activity against Enterococcus faecalis, Staphylococcus aureus and Vibrio cholerae (cc). The tested V. cholerae strains were the most sensitive strains, and exhibited a clear CFU size reduction from the bactericidal kinetic curves. The methanolic extract had activity against T. mentagrophytes and R. lilacina. The antioxidant activity (SC50= 36.42 μg/mL) was related to the total phenolic (74.4 mg eAG/g) and flavonoid content (21.982 mg (eQ)/g). The bioassay guided fractionation results suggested that the antimicrobial properties of the extract may act through synergism because the total extract had higher activity against bacteria compared to the collected fractions.Conclusion: This study scientifically validates the application of the fruit fiber from Pochote as a part of a traditional medicine approach to alleviate infections caused by bacteria and fungi.Keywords: antimicrobial, Ceiba, Bombacaceae, fruit fib
Auslander-Buchweitz approximation theory for triangulated categories
We introduce and develop an analogous of the Auslander-Buchweitz
approximation theory (see \cite{AB}) in the context of triangulated categories,
by using a version of relative homology in this setting. We also prove several
results concerning relative homological algebra in a triangulated category
\T, which are based on the behavior of certain subcategories under finiteness
of resolutions and vanishing of Hom-spaces. For example: we establish the
existence of preenvelopes (and precovers) in certain triangulated subcategories
of \T. The results resemble various constructions and results of Auslander
and Buchweitz, and are concentrated in exploring the structure of a
triangulated category \T equipped with a pair (\X,\omega), where \X is
closed under extensions and is a weak-cogenerator in \X, usually
under additional conditions. This reduces, among other things, to the existence
of distinguished triangles enjoying special properties, and the behavior of
(suitably defined) (co)resolutions, projective or injective dimension of
objects of \T and the formation of orthogonal subcategories. Finally, some
relationships with the Rouquier's dimension in triangulated categories is
discussed.Comment: To appear at: Appl. Categor. Struct. (2011); 22 page
The low-energy limit of AdS(3)/CFT2 and its TBA
We investigate low-energy string excitations in AdS3 × S3 × T4. When the worldsheet is decompactified, the theory has gapless modes whose spectrum at low energies is determined by massless relativistic integrable S matrices of the type introduced by Al. B. Zamolodchikov. The S matrices are non-trivial only for excitations with identical worldsheet chirality, indicating that the low-energy theory is a CFT2. We construct a Thermodynamic Bethe Ansatz (TBA) for these excitations and show how the massless modes’ wrapping effects may be incorporated into the AdS3 spectral problem. Using the TBA and its associated Y-system, we determine the central charge of the low-energy CFT2 to be c = 6 from calculating the vacuum energy for antiperiodic fermions — with the vacuum energy being zero for periodic fermions in agreement with a supersymmetric theory — and find the energies of some excited states
Two-year clinical outcome from the Iberian registry patients after left atrial appendage closure
AIMS:
The aim of this study was to observe the percentage of thromboembolic and haemorrhagic events over a 2-year follow-up in patients with non-valvular atrial fibrillation (NVAF) undergoing closure of the left atrial appendage (LAA) with an occlusion device. Observed events and CHADS2 (congestive heart failure, hypertension, age, diabetes, stroke history), CHA2DS2-VASc (also adding: vascular disease and sex) and HAS-BLED (hypertension, abnormal liver/renal function, stroke history, bleeding predisposition, labile international normalised ratios, elderly, drugs/alcohol use)-predicted events were compared.
METHODS:
LAA closure with an occlusion device was performed in 167 NVAF patients contraindicated for oral anticoagulants and recruited from 12 hospitals between 2009 and 2013. At least two transoesophageal echocardiograms were performed in the first 6 months postimplantation. Antithrombotics included clopidogrel and aspirin. Patients were monitored for death, stroke, major and relevant bleeding and hospitalisation for concomitant conditions. Mean age was 74.68±8.58, median follow-up was 24 months, 5.38% had intraoperative complications and implantation was successful in 94.6% of subjects. Mortality during follow-up was 10.8%, mostly (9.5%) non-cardiac related. Bleeding occurred in 10.1% of subjects, 5.7% major and 4.4% minor though relevant, and 4.4% suffered stroke. Major bleeding and stroke/transient ischaemic attack events within 2 years (annual event rates, 290 patients/year) were less frequent than expected from CHADS2 (2.4% vs 9.6%), CHA2DS2-VASc (2.4% vs 8.3%) and HAS-BLED (3.1% vs 6.6%) risk scores (p<0.001, p=0.003, p=0.047, respectively).
CONCLUSIONS:
LAA closure with an occlusion device in patients contraindicated for oral anticoagulants is a therapeutic option associated with fewer thromboembolic and haemorrhagic events than expected from risk scores, particularly in the second year postimplantation
Time-Fractional Optimal Control of Initial Value Problems on Time Scales
We investigate Optimal Control Problems (OCP) for fractional systems
involving fractional-time derivatives on time scales. The fractional-time
derivatives and integrals are considered, on time scales, in the
Riemann--Liouville sense. By using the Banach fixed point theorem, sufficient
conditions for existence and uniqueness of solution to initial value problems
described by fractional order differential equations on time scales are known.
Here we consider a fractional OCP with a performance index given as a
delta-integral function of both state and control variables, with time evolving
on an arbitrarily given time scale. Interpreting the Euler--Lagrange first
order optimality condition with an adjoint problem, defined by means of right
Riemann--Liouville fractional delta derivatives, we obtain an optimality system
for the considered fractional OCP. For that, we first prove new fractional
integration by parts formulas on time scales.Comment: This is a preprint of a paper accepted for publication as a book
chapter with Springer International Publishing AG. Submitted 23/Jan/2019;
revised 27-March-2019; accepted 12-April-2019. arXiv admin note: substantial
text overlap with arXiv:1508.0075
Functional and neurometabolic asymmetry in SHR and WKY rats following vasoactive treatments
A lateralized distribution of neuropeptidase activities in the frontal cortex of normotensive and
hypertensive rats has been described depending on the use of some vasoactive drugs and linked to
certain mood disorders. Asymmetrical neuroperipheral connections involving neuropeptidases from the
left or right hemisphere and aminopeptidases from the heart or plasma have been suggested to play
a role in this asymmetry. We hypothesize that such asymmetries could be extended to the connection
between the brain and physiologic parameters and metabolic factors from plasma and urine. To
assess this hypothesis, we analyzed the possible correlation between neuropeptidases from the left
and right frontal cortex with peripheral parameters in normotensive (Wistar Kyoto [WKY]) rats and
hypertensive rats (spontaneously hypertensive rats [SHR]) untreated or treated with vasoactive drugs
such as captopril, propranolol and L-nitro-arginine methyl ester. Neuropeptidase activities from the
frontal cortex were analyzed fluorometrically using arylamide derivatives as substrates. Physiological
parameters and metabolic factors from plasma and urine were determined using routine laboratory
techniques. Vasoactive drug treatments differentially modified the asymmetrical neuroperipheral
pattern by changing the predominance of the correlations between peripheral parameters and central
neuropeptidase activities of the left and right frontal cortex. The response pattern also differed between
SHR and WKY rats. These results support an asymmetric integrative function of the organism and
suggest the possibility of a different neurometabolic response coupled to particular mood disorders,
depending on the selected vasoactive drug.This work was supported by the Ministry of Science and Innovation through project no. SAF 2008 04685 C02 01
Estimating retention benchmarks for salvage logging to protect biodiversity
S.T. was supported by the Humboldt-Foundation and by the MOST (Ministry of Science
and Technology) Taiwan Research Fellowship to work with A.C. at National Tsing Hua
University, Taiwan. S.T. received funds from the Gregor Louisoder Environmental
Foundation. A.B.L. received funds from the Humboldt-Foundation.Forests are increasingly affected by natural disturbances. Subsequent salvage logging, a
widespread management practice conducted predominantly to recover economic capital,
produces further disturbance and impacts biodiversity worldwide. Hence, naturally disturbed
forests are among the most threatened habitats in the world, with consequences for their
associated biodiversity. However, there are no evidence-based benchmarks for the proportion
of area of naturally disturbed forests to be excluded from salvage logging to conserve biodiversity.
We apply a mixed rarefaction/extrapolation approach to a global multi-taxa dataset
from disturbed forests, including birds, plants, insects and fungi, to close this gap. We find
that 75 ± 7% (mean ± SD) of a naturally disturbed area of a forest needs to be left unlogged
to maintain 90% richness of its unique species, whereas retaining 50% of a naturally disturbed
forest unlogged maintains 73 ± 12% of its unique species richness. These values do
not change with the time elapsed since disturbance but vary considerably among taxonomic
groups.Open Access funding enabled and organized by Projekt DEA
Estimation of PM10-bound As, Cd, Ni and Pb levels by means of statistical modelling: PLSR and ANN approaches
Air quality assessment regarding metals and metalloids using experimental measurements is expensive and time consuming due to the cost and time required for the analytical determination of the levels of these pollutants. According to the European Union (EU) Air Quality Framework Directive (Directive 2008/50/EC), other alternatives, such as objective estimation techniques, can be considered for ambient air quality assessment in zones and agglomerations where the level of pollutants is below a certain concentration value known as the lower assessment threshold. These conditions occur in urban areas in Cantabria (northern Spain). This work aims to estimate the levels of As, Cd, Ni and Pb in airborne PM10 at two urban sites in the Cantabria region (Castro Urdiales and Reinosa) using statistical models as objective estimation techniques. These models were developed based on three different approaches: partial least squares regression (PLSR), artificial neural networks (ANNs) and an alternative approach consisting of principal component analysis (PCA) coupled with ANNs (PCA-ANN). Additionally, these models were externally validated using previously unseen data. The results show that the models developed in this work based on PLSR and ANNs fulfil the EU uncertainty requirements for objective estimation techniques and provide an acceptable estimation of the mean values. As a consequence, they could be considered as an alternative to experimental measurements for air quality assessment regarding the aforementioned pollutants in the study areas while saving time and resources.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the Project CMT2010-16068. The authors also thank the Regional Environment Ministry of the Cantabria Government for providing the PM10 samples at the Castro Urdiales and Reinosa sites
Topological Lattice Actions
We consider lattice field theories with topological actions, which are
invariant against small deformations of the fields. Some of these actions have
infinite barriers separating different topological sectors. Topological actions
do not have the correct classical continuum limit and they cannot be treated
using perturbation theory, but they still yield the correct quantum continuum
limit. To show this, we present analytic studies of the 1-d O(2) and O(3)
model, as well as Monte Carlo simulations of the 2-d O(3) model using
topological lattice actions. Some topological actions obey and others violate a
lattice Schwarz inequality between the action and the topological charge Q.
Irrespective of this, in the 2-d O(3) model the topological susceptibility
\chi_t = \l/V is logarithmically divergent in the continuum limit.
Still, at non-zero distance the correlator of the topological charge density
has a finite continuum limit which is consistent with analytic predictions. Our
study shows explicitly that some classically important features of an action
are irrelevant for reaching the correct quantum continuum limit.Comment: 38 pages, 12 figure
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