465 research outputs found
Transient effects in the backscattered current of a Luttinger liquid
We study the backscattered current in a Luttinger liquid in the presence of a
point like weak impurity switched on at finite time, taking into account
finite-temperature effects. We show how the well-known results for a static
impurity are distorted. We derive a dimensionless parameter as
function of the electron-electron interaction and the temperature, such that
for ) the switching process is relevant (irrelevant). Our
results suggest the possibility of determining the value of the Luttinger
parameter through time measurements in transport experiments at fixed
voltage.Comment: 8 pages, 3 figures. To appear in Physical Review
Acúmulo de nitrogênio e produtividade do milho adubado com dejeto líquido de suínos aplicado em superfície ou injetado no solo com ou sem inibidor de nitrificação.
Ammonia volatilization from soil amended with swine slurry: effect of application method and use of nitrification inhibitor.
Efeitos do treinamento da musculatura do assoalho pélvico sobre o parto e recém-nascido: estudo controlado randomizado
BACKGROUND: The use of the pelvic floor muscle training for urinary incontinence treatment is well established but little is known about its effects in labor and newborn outcomes. OBJECTIVES: To evaluate the effects of antenatal pelvic floor muscle training and strength in labor and newborn outcomes in low-income pregnant women. METHODS: This is a randomized controlled trial that recruited forty-two nulliparous healthy pregnant women aged between 18-36 years old and able to contract the pelvic floor muscles. The participants were included in the study with 20 weeks of gestational age and had their pelvic floor muscles measured by vaginal squeeze pressure. They were randomly allocated into two groups: training group and a non-intervention control group. Then, all participants had their labor and newborn outcomes evaluated through consultation of medical records by a blinded researcher. RESULTS: There were no statistically significant differences between the groups regarding gestational age at birth, type of labor, duration of the second stage of labor, total time of labor, prevalence of laceration, weight and size of the baby, and Apgar score. No correlation was observed between pelvic floor muscle strength and the second stage or the total length of labor. CONCLUSIONS: This randomized controlled trial did not find any effect of pelvic floor muscle training or pelvic floor muscle strength on labor and newborn outcomes.CONTEXTUALIZAÇÃO: O treinamento da musculatura do assoalho pélvico para tratamento da incontinência urinária é bem estabelecida, mas pouco se sabe sobre seus efeitos sobre o parto e o recém-nascido. OBJETIVOS: Avaliar se os desfechos do parto e os resultados dos recém-nascidos são influenciados pelo treinamento e força da musculatura do assoalho pélvico realizados por gestantes de baixa renda. MÉTODOS: Trata-se de um ensaio clínico randomizado que incluiu 42 gestantes nulíparas de baixo risco, com idade entre 18 e 36 anos, e que eram capazes de contrair a musculatura do assoalho pélvico. As gestantes foram incluídas no estudo com 20 semanas de idade gestacional, e realizava-se a avaliação da pressão de contração vaginal pela contração da musculatura do assoalho pélvico. Elas foram randomizadas em dois grupos: grupo de treinamento e grupo controle. Todas as voluntárias tiveram o trabalho de parto e os resultados dos recém-nascidos avaliados por meio de consulta ao prontuário por um pesquisador não envolvido com o grupo de treinamento. RESULTADOS: Não houve diferença significativa entre os grupos quanto à idade gestacional no nascimento, tipo de parto, duração da segunda fase de trabalho de parto, tempo total de trabalho de parto, prevalência da laceração perineal, peso e tamanho do bebê e índice de Apgar. Nenhuma correlação foi encontrada entre a força muscular do assoalho pélvico e a segunda fase ou a duração total do trabalho de parto. CONCLUSÕES: Este ensaio clínico randomizado não verificou qualquer influência do treinamento muscular do assoalho pélvico e da força dos músculos do assoalho pélvico sobre o trabalho de parto e os resultados do recém-nascido
Experimental Rugged Fitness Landscape in Protein Sequence Space
The fitness landscape in sequence space determines the process of biomolecular evolution. To plot the fitness landscape of protein function, we carried out in vitro molecular evolution beginning with a defective fd phage carrying a random polypeptide of 139 amino acids in place of the g3p minor coat protein D2 domain, which is essential for phage infection. After 20 cycles of random substitution at sites 12–130 of the initial random polypeptide and selection for infectivity, the selected phage showed a 1.7×10(4)-fold increase in infectivity, defined as the number of infected cells per ml of phage suspension. Fitness was defined as the logarithm of infectivity, and we analyzed (1) the dependence of stationary fitness on library size, which increased gradually, and (2) the time course of changes in fitness in transitional phases, based on an original theory regarding the evolutionary dynamics in Kauffman's n-k fitness landscape model. In the landscape model, single mutations at single sites among n sites affect the contribution of k other sites to fitness. Based on the results of these analyses, k was estimated to be 18–24. According to the estimated parameters, the landscape was plotted as a smooth surface up to a relative fitness of 0.4 of the global peak, whereas the landscape had a highly rugged surface with many local peaks above this relative fitness value. Based on the landscapes of these two different surfaces, it appears possible for adaptive walks with only random substitutions to climb with relative ease up to the middle region of the fitness landscape from any primordial or random sequence, whereas an enormous range of sequence diversity is required to climb further up the rugged surface above the middle region
A decision aid regarding long-term tube feeding targeting substitute decision makers for cognitively impaired older persons in Japan: A small-scale before-and-after study
Green manure in coffee systems in the region of Zona da Mata, Minas Gerais: characteristics and kinetics of carbon and nitrogen mineralization.
The use of green manure may contribute to reduce soil erosion and increase the soil organic matter content and N availability in coffee plantations in the Zona da Mata, State of Minas Gerais, in Southeastern Brazil. The potential of four legumes (A. pintoi, C. mucunoides, S. aterrimum and S. guianensis)to produce above-ground
biomass, accumulate nutrients and mineralize N was studied in two coffee plantations of subsistence farmers under different climate conditions. The biomass production of C. mucunoides was influenced by the shade of the coffee plantation.C. mucunoides tended to mineralize more N than the other legumes due to the low polyphenol content and polyphenol/N ratio. In the first year, the crop establishment of A. pintoi in the area took longer than of the other legumes, resulting in lower biomass production and N2 fixation. In the long term, cellulose was the main
factor controlling N mineralization. The biochemical characteristics, nutrient accumulation and biomass production of the legumes were greatly influenced by
the altitude and position of the area relative to the sun
Predictability of evolutionary trajectories in fitness landscapes
Experimental studies on enzyme evolution show that only a small fraction of
all possible mutation trajectories are accessible to evolution. However, these
experiments deal with individual enzymes and explore a tiny part of the fitness
landscape. We report an exhaustive analysis of fitness landscapes constructed
with an off-lattice model of protein folding where fitness is equated with
robustness to misfolding. This model mimics the essential features of the
interactions between amino acids, is consistent with the key paradigms of
protein folding and reproduces the universal distribution of evolutionary rates
among orthologous proteins. We introduce mean path divergence as a quantitative
measure of the degree to which the starting and ending points determine the
path of evolution in fitness landscapes. Global measures of landscape roughness
are good predictors of path divergence in all studied landscapes: the mean path
divergence is greater in smooth landscapes than in rough ones. The
model-derived and experimental landscapes are significantly smoother than
random landscapes and resemble additive landscapes perturbed with moderate
amounts of noise; thus, these landscapes are substantially robust to mutation.
The model landscapes show a deficit of suboptimal peaks even compared with
noisy additive landscapes with similar overall roughness. We suggest that
smoothness and the substantial deficit of peaks in the fitness landscapes of
protein evolution are fundamental consequences of the physics of protein
folding.Comment: 14 pages, 7 figure
Manejo da adubação nitrogenada na sucessão aveia-preta/milho no sistema plantio direto
- …