506 research outputs found
Lorentz-covariant Hamiltonian analysis of BF gravity with the Immirzi parameter
We perform the Lorentz-covariant Hamiltonian analysis of two Lagrangian
action principles that describe general relativity as a constrained BF theory
and that include the Immirzi parameter. The relation between these two
Lagrangian actions has been already studied through a map among the fields
involved. The main difference between these is the way the Immirzi parameter is
included, since in one of them the Immirzi parameter is included explicitly in
the BF terms, whereas in the other (the CMPR action) it is in the constraint on
the B fields. In this work we continue the analysis of their relationship but
at the Hamiltonian level. Particularly, we are interested in seeing how the
above difference appears in the constraint structure of both action principles.
We find that they both possess the same number of first-class and second-class
constraints and satisfy a very similar (off-shell) Poisson-bracket algebra on
account of the type of canonical variables employed. The two algebras can be
transformed into each other by making a suitable change of variablesComment: LaTeX file, no figure
Use of camera trapping in determining Iberian lynx population parameters: The use area and its limitations
Below are the results of the survey of the Iberian lynx obtained with camera-trapping between 2000 and 2007 in Sierra Morena. Two very important aspects of camera-trapping concerning its efficiency are also analyzed. The first is the evolution along years according to the camera-trapping type used of two efficiency indicators. The results obtained demonstrate that the most efficient lure is rabbit, though it is the less proven (92 trap-nights), followed by camera-trapping in the most frequent marking places (latrines). And, we propose as a novel the concept of use area as a spatial reference unit for the camera-trapping monitoring of non radio-marked animals is proposed, and its validity discussed
Modeling viral coevolution: HIV multi-clonal persistence and competition dynamics
The coexistence of different viral strains (quasispecies) within the same
host are nowadays observed for a growing number of viruses, most notably HIV,
Marburg and Ebola, but the conditions for the formation and survival of new
strains have not yet been understood. We present a model of HIV quasispecies
competition, that describes the conditions of viral quasispecies coexistence
under different immune system conditions. Our model incorporates both T and B
cells responses, and we show that the role of B cells is important and additive
to that of T cells. Simulations of coinfection (simultaneous infection) and
superinfection (delayed secondary infection) scenarios in the early stages
(days) and in the late stages of the infection (years) are in agreement with
emerging molecular biology findings. The immune response induces a competition
among similar phenotypes, leading to differentiation (quasi-speciation), escape
dynamics and complex oscillations of viral strain abundance. We found that the
quasispecies dynamics after superinfection or coinfection has time scales of
several months and becomes even slower when the immune system response is weak.
Our model represents a general framework to study the speed and distribution of
HIV quasispecies during disease progression, vaccination and therapy.Comment: 20 pages, 10 figure
Hipotiroidismo subclínico y factores de riesgo cardiovascular
Objetivo: Conocer la prevalencia del hipotiroidismo
subclínico en la población general de un centro de salud
urbano y describir las características clínicas y factores
de riesgo cardiovascular de los pacientes con hipotiroidismo
subclínico.
Métodos: Se realizó un estudio observacional descriptivo,
transversal, retrospectivo, revisando las historias clínicas
de los pacientes incluidos en la muestra desde junio de 2005
hasta julio de 2007. Se analizaron las siguientes variables;
Datos generales: edad y sexo. Antecedentes familiares:
patología tiroidea y otras enfermedades. Antecedentes personales:
cardiovasculares, pulmonares, enfermedades
autoinmunes, alteraciones gineco-obstétricas, diabetes,
hipertensión (HT), dislipemia, obesidad, alteraciones psiquiátricas
y hematológicas. Datos de laboratorio: niveles
de TSH, niveles de T4 libre,presencia de anticuerpos antiperoxidasa,
niveles de colesterol total y sus fracciones.
Resultados: La prevalencia de la muestra de 100
pacientes recogida durante 8 meses fue de 3,8% de la
población general mayor de 14 años, de la cual 79 eran
mujeres y 21 eran hombres. El 13% eran diabéticos tipo
2, 23% tenían HT y un 40% tenían dislipemia. Sobrepeso
y obesidad estaban presentes en un 26%. El nivel medio
de TSH fue 6.92 ± 2,29 U/ml y el nivel medio de T4 libre
fue 1,16 ± 0,16 ng/ml.
Conclusiones: La prevalencia del hipotiroidismo subclínico
fue 3,8%. sobre todo en mujeres con una edad
media de 46 años. La incidencia de factores de riesgo cardiovascular
en los sujetos estudiados es mayor en DM
(13%), similar a la población general en cuanto a la dislipemia
(40%) y obesidad (20%) y menor en HTA (23%).
En nuestro estudio no se observa una pauta común en
el manejo del hipotiroidismo subclínico, siendo necesaria
la implementación y promoción de guías de actuación en
Atención PrimariaObjective: To determine the prevalence of subclinical
hypothyroidism in the general population of an urban
health center and describe the clinical characteristics and
cardiovascular risk factors in patients with subclinical
hypothyroidism.
Methods: An observational study, retrospective, reviewing
the medical histories of patients sampled from June
2005 until July 2007. We analyzed the following variables;
facts: age and sex. Family history thyroid disease
and other diseases. Personal history: cardiovascular pulmonary
autoimmune, alterations gynecology obstetric
diabetes, hypertension (HT) dislipemia, obesity, psychiatric
alterations and haematological. Laboratory data:
novel TSH, free T4, antiperoxidase antibodies, total cholesterol
and its fractions.
Results: The prevalence of the sample of 100 patients
collected over 8 months was 3.8% in the general population
over 14 years, of which 79 were women and 21 were
men. 13% were type 2 diabetics, 23% had HT and 40%
had dyslipidemia. Overweight and obesity were present
in 26%. The average level of TSH was 6.92 ± 2.29 U/ml
and the average level of free T4 was 1.16 ± 0.16 ng/ml.
Conclusions: Prevalence subclinical hypothyroidism
was 3.8%. especially in women with a mean age of 46. The
incidence of cardiovascular risk factors in the subjects
studied is higher in DM (13%), similar to general population
in terms of dyslipidemia (40%) and obesity (23%)
and lowest in hypertension (23%). In our study we observed
a common pattern in the management of subclinical
hypothyroidism, requiring the implementation and promotion
of practice guidelines in primary car
A statistical mechanics approach to autopoietic immune networks
The aim of this work is to try to bridge over theoretical immunology and
disordered statistical mechanics. Our long term hope is to contribute to the
development of a quantitative theoretical immunology from which practical
applications may stem. In order to make theoretical immunology appealing to the
statistical physicist audience we are going to work out a research article
which, from one side, may hopefully act as a benchmark for future improvements
and developments, from the other side, it is written in a very pedagogical way
both from a theoretical physics viewpoint as well as from the theoretical
immunology one.
Furthermore, we have chosen to test our model describing a wide range of
features of the adaptive immune response in only a paper: this has been
necessary in order to emphasize the benefit available when using disordered
statistical mechanics as a tool for the investigation. However, as a
consequence, each section is not at all exhaustive and would deserve deep
investigation: for the sake of completeness, we restricted details in the
analysis of each feature with the aim of introducing a self-consistent model.Comment: 22 pages, 14 figur
Impact of a COVID-19 Outbreak in an Elderly Care Home after Primary Vaccination
[EN] Elderly care home residents are particularly vulnerable to COVID-19 due to immunesenescence, pre-existing medical conditions, and the risk of transmission from staff and visitors.
This study aimed to describe the outcomes of a COVID-19 outbreak in a long-term care facility
for elderly persons following the initial vaccination. A single-center, retrospective, observational
design was used to analyze the variables associated with hospitalization and death rate by logistic
regression. Adjusted odds ratios (aOR) and their 95% confidence intervals (CI) were calculated.
Sixty-eight residents received the first dose of the COVID-19 vaccine. Despite being negative six days
after vaccination, the performance of a second test 4 days later revealed 51 positives (75.0%) among
residents and 18 among workers (56.3%). A total of 65 of the 68 residents (95.58%) had positive
results with symptoms, whereas 34.9% required hospitalization, and 25.8% died. The best-fitting
model to explain the distribution of cases reflects three points at the time of infection.. The time
from vaccination to symptom onset explains the hospitalization and mortality rates since a day
elapsed halves the risk of hospitalization (aOR = 0.57; CI = 0.38−0.75) and the risk of death by a
quarter (aOR = 0.74; CI = 0.63−0.88). Nursing homes present an elevated risk of transmission and
severity of SARS-CoV-2 infection. Although vaccination reduces the risk of hospitalization and
death, extreme prevention and control measures are essential in these institutions despite the high
vaccination coverage.S
Timely HAART initiation may pave the way for a better viral control
<p>Abstract</p> <p>Background</p> <p>When to initiate antiretroviral therapy in HIV infected patients is a diffcult clinical decision. Actually, it is still a matter of discussion whether early highly active antiretroviral therapy (HAART) during primary HIV infection may influence the dynamics of the viral rebound, in case of therapy interruption, and overall the main disease course.</p> <p>Methods</p> <p>In this article we use a computational model and clinical data to identify the role of HAART timing on the residual capability to control HIV rebound after treatment suspension. Analyses of clinical data from three groups of patients initiating HAART respectively before seroconversion (very early), during the acute phase (early) and in the chronic phase (late), evidence differences arising from the very early events of the viral infection.</p> <p>Results</p> <p>The computational model allows a fine grain assessment of the impact of HAART timing on the disease outcome, from acute to chronic HIV-1 infection. Both patients' data and computer simulations reveal that HAART timing may indeed affect the HIV control capability after treatment discontinuation. In particular, we find a median time to viral rebound that is significantly longer in very early than in late patients.</p> <p>Conclusions</p> <p>A timing threshold is identified, corresponding to approximately three weeks post-infection, after which the capability to control HIV replication is lost. Conversely, HAART initiation occurring within three weeks from the infection could allow to preserve a significant control capability. This time could be related to the global triggering of uncontrolled immune activation, affecting residual immune competence preservation and HIV reservoir establishment.</p
Pyramidal Neurons in Rat Prefrontal Cortex Projecting to Ventral Tegmental Area and Dorsal Raphe Nucleus Express 5-HT2A Receptors
The prefrontal cortex (PFC) is involved in higher brain functions altered in schizophrenia. Classical antipsychotics modulate cortico-limbic circuits mainly through subcortical D2 receptor blockade, whereas second generation (atypical) antipsychotics preferentially target cortical 5-HT receptors. Anatomical and functional evidence supports a PFC-based control of the brainstem monoaminergic nuclei. Using a combination of retrograde tracing experiments and in situ hybridization we report that a substantial proportion of PFC pyramidal neurons projecting to the dorsal raphe (DR) and/or ventral tegmental area (VTA) express 5-HT2A receptors. Cholera-toxin B application into the DR and the VTA retrogradely labeled projection neurons in the medial PFC (mPFC) and in orbitofrontal cortex (OFC). In situ hybridization of 5-HT2A receptor mRNA in the same tissue sections labeled a large neuronal population in mPFC and OFC. The percentage of DR-projecting neurons expressing 5-HT2A receptor mRNA was ∼60% in mPFC and ∼75% in OFC (n = 3). Equivalent values for VTA-projecting neurons were ∼55% in both mPFC and ventral OFC. Thus, 5-HT2A receptor activation/blockade in PFC may have downstream effects on dopaminergic and serotonergic systems via direct descending pathways. Atypical antipsychotics may distally modulate monoaminergic cells through PFC 5-HT2A receptor blockade, presumably decreasing the activity of neurons receiving direct cortical inputs
Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study
Volatile organic compounds (VOCs) and carbonaceous aerosol were measured at a sub-urban site near Mexico City in March of 2006 during the MILAGRO study (Megacity Initiative: Local and Global Research Objectives). Diurnal variations of hydrocarbons, elemental carbon (EC) and hydrocarbon-like organic aerosol (HOA) were dominated by a high peak in the early morning when local emissions accumulated in a shallow boundary layer, and a minimum in the afternoon when the emissions were diluted in a significantly expanded boundary layer and, in case of the reactive gases, removed by OH. In comparison, diurnal variations of species with secondary sources such as the aldehydes, ketones, oxygenated organic aerosol (OOA) and water-soluble organic carbon (WSOC) stayed relatively high in the afternoon indicating strong photochemical formation. Emission ratios of many hydrocarbon species relative to CO were higher in Mexico City than in the U.S., but we found similar emission ratios for most oxygenated VOCs and organic aerosol. Secondary formation of acetone may be more efficient in Mexico City than in the U.S., due to higher emissions of alkane precursors from the use of liquefied petroleum gas. Secondary formation of organic aerosol was similar between Mexico City and the U.S. Combining the data for all measured gas and aerosol species, we describe the budget of total observed organic carbon (TOOC), and find that the enhancement ratio of TOOC relative to CO is conserved between the early morning and mid afternoon despite large compositional changes. Finally, the influence of biomass burning is investigated using the measurements of acetonitrile, which was found to correlate with levoglucosan in the particle phase. Diurnal variations of acetonitrile indicate a contribution from local burning sources. Scatter plots of acetonitrile versus CO suggest that the contribution of biomass burning to the enhancement of most gas and aerosol species was not dominant and perhaps not dissimilar from observations in the U.S
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