781 research outputs found
Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F center dot center dot center dot HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the (1h)J(F),(H(O)) coupling constant in the syn-exo isomer is modulated by the n(F)->sigma*(OH) interaction, i.e., the quantum nature of the F center dot center dot center dot HO hydrogen bond.812271232Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq
Combined effects of time spent in physical activity, sedentary behaviors and sleep on obesity and cardio-metabolic health markers: a novel compositional data analysis approach
<div><p>The associations between time spent in sleep, sedentary behaviors (SB) and physical activity with health are usually studied without taking into account that time is finite during the day, so time spent in each of these behaviors are codependent. Therefore, little is known about the combined effect of time spent in sleep, SB and physical activity, that together constitute a composite whole, on obesity and cardio-metabolic health markers. Cross-sectional analysis of NHANES 2005–6 cycle on N = 1937 adults, was undertaken using a compositional analysis paradigm, which accounts for this intrinsic codependence. Time spent in SB, light intensity (LIPA) and moderate to vigorous activity (MVPA) was determined from accelerometry and combined with self-reported sleep time to obtain the 24 hour time budget composition. The distribution of time spent in sleep, SB, LIPA and MVPA is significantly associated with BMI, waist circumference, triglycerides, plasma glucose, plasma insulin (all p<0.001), and systolic (p<0.001) and diastolic blood pressure (p<0.003), but not HDL or LDL. Within the composition, the strongest positive effect is found for the proportion of time spent in MVPA. Strikingly, the effects of MVPA replacing another behavior and of MVPA being displaced by another behavior are asymmetric. For example, re-allocating 10 minutes of SB to MVPA was associated with a lower waist circumference by 0.001% but if 10 minutes of MVPA is displaced by SB this was associated with a 0.84% higher waist circumference. The proportion of time spent in LIPA and SB were detrimentally associated with obesity and cardiovascular disease markers, but the association with SB was stronger. For diabetes risk markers, replacing SB with LIPA was associated with more favorable outcomes. Time spent in MVPA is an important target for intervention and preventing transfer of time from LIPA to SB might lessen the negative effects of physical inactivity.</p></div
Modified spin-wave study of random antiferromagnetic-ferromagnetic spin chains
We study the thermodynamics of one-dimensional quantum spin-1/2 Heisenberg
ferromagnetic system with random antiferromagnetic impurity bonds. In the
dilute impurity limit, we generalize the modified spin-wave theory for random
spin chains, where local chemical potentials for spin-waves in ferromagnetic
spin segments are introduced to ensure zero magnetization at finite
temperature. This approach successfully describes the crossover from behavior
of pure one-dimensional ferromagnet at high temperatures to a distinct Curie
behavior due to randomness at low temperatures. We discuss the effects of
impurity bond strength and concentration on the crossover and low temperature
behavior.Comment: 14 pages, 7 eps figure
Spatial Guilds in the Serengeti Food Web Revealed by a Bayesian Group Model
Food webs, networks of feeding relationships among organisms, provide
fundamental insights into mechanisms that determine ecosystem stability and
persistence. Despite long-standing interest in the compartmental structure of
food webs, past network analyses of food webs have been constrained by a
standard definition of compartments, or modules, that requires many links
within compartments and few links between them. Empirical analyses have been
further limited by low-resolution data for primary producers. In this paper, we
present a Bayesian computational method for identifying group structure in food
webs using a flexible definition of a group that can describe both functional
roles and standard compartments. The Serengeti ecosystem provides an
opportunity to examine structure in a newly compiled food web that includes
species-level resolution among plants, allowing us to address whether groups in
the food web correspond to tightly-connected compartments or functional groups,
and whether network structure reflects spatial or trophic organization, or a
combination of the two. We have compiled the major mammalian and plant
components of the Serengeti food web from published literature, and we infer
its group structure using our method. We find that network structure
corresponds to spatially distinct plant groups coupled at higher trophic levels
by groups of herbivores, which are in turn coupled by carnivore groups. Thus
the group structure of the Serengeti web represents a mixture of trophic guild
structure and spatial patterns, in contrast to the standard compartments
typically identified in ecological networks. From data consisting only of nodes
and links, the group structure that emerges supports recent ideas on spatial
coupling and energy channels in ecosystems that have been proposed as important
for persistence.Comment: 28 pages, 6 figures (+ 3 supporting), 2 tables (+ 4 supporting
Tricritical Points in the Sherrington-Kirkpatrick Model in the Presence of Discrete Random Fields
The infinite-range-interaction Ising spin glass is considered in the presence
of an external random magnetic field following a trimodal (three-peak)
distribution. The model is studied through the replica method and phase
diagrams are obtained within the replica-symmetry approximation. It is shown
that the border of the ferromagnetic phase may present first-order phase
transitions, as well as tricritical points at finite temperatures. Analogous to
what happens for the Ising ferromagnet under a trimodal random field, it is
verified that the first-order phase transitions are directly related to the
dilution in the fields (represented by ). The ferromagnetic boundary at
zero temperature also exhibits an interesting behavior: for , a single tricritical point occurs, whereas if
the critical frontier is completely continuous; however, for
, a fourth-order critical point appears. The stability
analysis of the replica-symmetric solution is performed and the regions of
validity of such a solution are identified; in particular, the Almeida-Thouless
line in the plane field versus temperature is shown to depend on the weight
.Comment: 23pages, 7 ps figure
Risk of surgical site infection in patients undergoing orthopedic surgery
This study aimed to identify risk factors associated with surgical site infections in orthopedic surgical patients at a public hospital in Minas Gerais, Brazil, between 2005 and 2007. A historical cohort of 3,543 patients submitted to orthopedic surgical procedures. A descriptive analysis was conducted and surgical site infection incidence rates were estimated. To verify the association between infection and risk factors, the Chi-square Test was used. The strength of association of the event with the independent variables was estimated using Relative Risk, with a 95% confidence interval and pEstudio para identificar factores de riesgo asociados a infecciones de sitio quirúrgico en pacientes quirúrgicos ortopédicos de un hospital público de Minas Gerais, Brasil, entre 2005 y 2007. Cohorte histórica de 3.543 pacientes sometidos a cirugÃas ortopédicas. Un análisis descriptivo fue realizado y la tasa de incidencia de infección fue estimada. Para verificar la asociación entre la infección y los factores de riesgo se usó el test chi-cuadrado. La fuerza de la asociación del evento con las variables independientes fue estimada por el Riesgo Relativo, con un intervalo de confianza de 95% y p Objetivou-se, neste estudo, identificar fatores de risco associados à s infecções de sÃtio cirúrgico, em pacientes cirúrgicos ortopédicos, de um hospital público de Minas Gerais, Brasil, entre 2005 e 2007. Como método usou-se coorte histórica em 3.543 pacientes submetidos a cirurgias ortopédicas. Análise descritiva e taxa de incidência de infecção foram estimadas. Para verificar a associação entre a infecção e os fatores de risco usou-se o teste qui-quadrado. A força da associação do evento com as variáveis independentes foi estimada pelo risco relativo, intervalo de confiança de 95% e p<0,05. A incidência de infecção de sÃtio cirúrgico foi de 1,8%. Potencial de contaminação da ferida cirúrgica, condições clÃnicas do paciente, tempo cirúrgico e tipo de procedimento ortopédico foram estatisticamente associados à infecção. A identificação de associação de infecção de sÃtio cirúrgico aos fatores de risco mencionados é importante e contribui para a prática clÃnica do enfermeiro
Uncertainty-based Traffic Accident Anticipation with Spatio-Temporal Relational Learning
Traffic accident anticipation aims to predict accidents from dashcam videos
as early as possible, which is critical to safety-guaranteed self-driving
systems. With cluttered traffic scenes and limited visual cues, it is of great
challenge to predict how long there will be an accident from early observed
frames. Most existing approaches are developed to learn features of
accident-relevant agents for accident anticipation, while ignoring the features
of their spatial and temporal relations. Besides, current deterministic deep
neural networks could be overconfident in false predictions, leading to high
risk of traffic accidents caused by self-driving systems. In this paper, we
propose an uncertainty-based accident anticipation model with spatio-temporal
relational learning. It sequentially predicts the probability of traffic
accident occurrence with dashcam videos. Specifically, we propose to take
advantage of graph convolution and recurrent networks for relational feature
learning, and leverage Bayesian neural networks to address the intrinsic
variability of latent relational representations. The derived uncertainty-based
ranking loss is found to significantly boost model performance by improving the
quality of relational features. In addition, we collect a new Car Crash Dataset
(CCD) for traffic accident anticipation which contains environmental attributes
and accident reasons annotations. Experimental results on both public and the
newly-compiled datasets show state-of-the-art performance of our model. Our
code and CCD dataset are available at https://github.com/Cogito2012/UString.Comment: Accepted by ACM MM 202
Lower production of IL-17A and increased susceptibility to Mycobacterium bovis in mice coinfected with Strongyloides venezuelensis
The presence of intestinal helminths can down-regulate the immune response required to control mycobacterial infection. BALB/c mice infected with Mycobacterium bovis following an infection with the intestinal helminth Strongyloides venezuelensis showed reduced interleukin-17A production by lung cells and increased bacterial burden. Also, small granulomas and a high accumulation of cells expressing the inhibitory molecule CTLA-4 were observed in the lung. These data suggest that intestinal helminth infection could have a detrimental effect on the control of tuberculosis (TB) and render coinfected individuals more susceptible to the development of TB
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