115 research outputs found
Quantum confinement in Si and Ge nanostructures: Effect of crystallinity
We look at the relationship between the preparation method of Si and Ge
nanostructures (NSs) and the structural, electronic, and optical properties in
terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap
energy with decreasing NS dimension. Directly measuring the effect of QC is
complicated by additional parameters, such as stress, interface and defect
states. In addition, differences in NS preparation lead to differences in the
relevant parameter set. A relatively simple model of QC, using a
`particle-in-a-box'-type perturbation to the effective mass theory, was applied
to Si and Ge quantum wells, wires and dots across a variety of preparation
methods. The choice of the model was made in order to distinguish contributions
that are solely due to the effects of QC, where the only varied experimental
parameter was the crystallinity. It was found that the hole becomes
de-localized in the case of amorphous materials, which leads to stronger
confinement effects. The origin of this result was partly attributed to
differences in the effective mass between the amorphous and crystalline NS as
well as between the electron and hole. Corrections to our QC model take into
account a position dependent effective mass. This term includes an inverse
length scale dependent on the displacement from the origin. Thus, when the
deBroglie wavelength or the Bohr radius of the carriers is on the order of the
dimension of the NS the carriers `feel' the confinement potential altering
their effective mass. Furthermore, it was found that certain interface states
(Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.Comment: arXiv admin note: substantial text overlap with arXiv:1111.201
Plurality Voting: the statistical laws of democracy in Brazil
We explore the statistical laws behind the plurality voting system by
investigating the election results for mayor held in Brazil in 2004. Our
analysis indicate that the vote partition among mayor candidates of the same
city tends to be "polarized" between two candidates, a phenomenon that can be
closely described by means of a simple fragmentation model. Complex concepts
like "government continuity" and "useful vote" can be identified and even
statistically quantified through our approach.Comment: 4 pages, 4 figure
Indicadores técnicos e econômicos do maracujazeiro amarelo irrigado com fonte de água subterrânea
The research aimed to quantify technical and economic indicators of yellow passion fruit tree irrigated with fractions of irrigation with underground source of water, to generate information that helps farmers in decision making on the implementation of investment in irrigated fruit growing (yellow passion fruit). For this purpose, we used the passion fruit crop irrigated with Microjet type irrigation system, with conducting system in simple espaliers. The treatments consisted of five hours of application of the depth of water required by the crop with irrigation frequency of two days. The results showed that the highest yield (16660kg ha-1) was obtained with the fractionation of irrigation twice a day (50% to 7h and 50% to 21h30), which provided an increase in productivity of 54%, demonstrating the financial viability and being highly profitable to the interest rate of 2% per year, with low sensitivity of financial risk to real interest rates above the prevailing market.O trabalho teve como objetivo quantificar indicadores técnicos e econômicos do maracujazeiro-amarelo irrigado com fracionamento da irrigação com fonte de água subterrânea, de forma a gerar informações que auxiliem os agricultores na tomada de decisão sobre a aplicação de seus investimentos na fruticultura irrigada (maracujá-amarelo). Para tanto, utilizou-se da cultura do maracujá, irrigado com sistema de irrigação tipo microjet, sob a forma de condução em espaldeiras simples. Os tratamentos constaram da combinação de horários de aplicação da lâmina de água requerida pela cultura, com frequência de irrigação de dois dias. Os resultados permitiram concluir que a maior produtividade (16.660 kg ha-1) foi obtida com o fracionamento da irrigação em duas vezes ao dia (50% às 7h e 50% às 21h30), a qual proporcionou um incremento de produtividade de 54%, demonstrando viabilidade do ponto de vista financeiro e altamente lucrativo à taxa de juros de 2% ao ano, com baixa sensibilidade de risco financeiro a taxas reais de juros acima das praticadas no mercado.94095
Produtividade e análise de indicadores técnicos do maracujazeiro-amarelo irrigado em diferentes horários.
Diante da necessidade de pesquisas sobre o manejo da irrigação em horários alternativos e com menor custo com eletricidade na produção do maracujá-amarelo irrigado objetivou-se, com esta pesquisa, avaliar os efeitos do fracionamento da irrigação em diferentes horários de aplicação sobre a produtividade e qualidade do fruto do maracujazeiro-amarelo tal como, também, a quantificação de indicadores técnicos; para tanto se conduziu um experimento no municÃpio de Pentecoste, CE, no perÃodo de setembro de 2009 a agosto de 2010, no delineamento em blocos ao acaso com cinco tratamentos e quatro repetições. Os tratamentos corresponderam aos horários de aplicação da lâmina de água requerida (LR) pela cultura (T1: 100% da LR à s 07 h; T2: 50% da LR à s 07 h e 50% da LR à s 15 h; T3: 25% da LR à s 07 h; 50% da LR à s 15 h e 25% da LR à s 21 h 30 min; T4: 100% da LR à s 21 h 30 min: T5: 50% da LR à s 07 h e 50% da LR à s 21 h 30 min). De acordo com os resultados a aplicação fracionada da lâmina de água requerida pela cultura com 50% à s 07 h e 50% à s 21 h 30 min, foi a alternativa que proporcionou a maior produtividade do maracujazeiro; os atributos de qualidade dos frutos de maracujazeiro sólidos solúveis totais e pH se mantiveram indiferentes quanto aos tratamentos
Effects of shoulder compensatory strength training program in rotator cuff strength of young swimmers
INTRODUCTION
The purpose of this study was to evaluate de effects of 16 week compensatory strength
training program in shoulder strength and respective conventional ratios (concentric ER/IR).
METHODS
A total of 40 national level male swimmers were assessed and randomly divided in two
groups – experimental group (N=20)-(age:14.65±0.67 years old, height:173.48±6.87 cm,
body mass:63.15±5.68 kg) and control group (N=20)-(age:14.60±0.60 years old, height:
170.79±6.48 cm, body mass:61.73±4.68 kg). Experimental subjects participated in a 16 week
shoulder strength program with Thera-Band® elastic bands (3 times a week). The peak-torque
of shoulder internal (IR) and external rotators (ER) was measured in both groups at baseline
and after 16 weeks. Concentric action at 60º/s (3 rep) and 180º/s (20 rep) were measured, in a
seated position, with the shoulder at 90º of abduction and the elbow flexed to 90º, using an
isokinetic dynamometer (Biodex System 3 – Biodex Corp., Shirley, USA). Anova with
repeated measures was used to determine significant main effects in shoulder rotators strength
and unilateral ER/IR ratios. The level of significance was set at 0.05.
RESULTS
Significant differences were found in all variables that measure the ER shoulder strength at
60º/s in dominant(DT) (P=0.031) and non-dominant(NDT) shoulder (P=0.001). Meanwhile
concentric action at 180º/s, only showed significant differences on DT shoulder (P=0.032). In
respect of ER/IR ratio, a compensatory strength training programme induces significant
differences in both shoulders at 60º/s (DT: P=0.001; NDT: P=0.001). At 180º/s we just found
significant effects on the DT ER/IR ratio (P=0.002).
DISCUSSION
The results of this study support earlier research [1] that showed that the unilateral shoulder
strength ratios increases substantially after a period of a strength training program. Since the
ratios describe the quality of muscular balance/imbalance [1], we can conclude that a 16 week
compensatory shoulder strength training program using Thera-Band® elastic bands, reduces
muscular imbalances in rotator cuff of competitive young swimmers. These results highlight
the useful of this kind of compensatory program to prevent shoulder injuries
Morse potential derived from first principles
We show that a direct connection can be drawn, based on fundamental quantum
principles, between the Morse potential, extensively used as an empirical
description for the atomic interaction in diatomic molecules, and the harmonic
potential. This is conceptually achieved here through a non-additive
translation operator, whose action leads to a perfect equivalence between the
quantum harmonic oscillator in deformed space and the quantum Morse oscillator
in regular space. In this way, our theoretical approach provides a distinctive
first principle rationale for anharmonicity, therefore revealing a possible
quantum origin for several related properties as, for example, the dissociation
energy of diatomic molecules and the deformation of cubic metals.Comment: 4 pages, 1 figur
Genetic parameters for faecal egg count, packed-cell volume and body-weight in Santa Inês lambs
Worm infection is one of the main factors responsible for economic losses in sheep breeding in Brazil. Random regression analysis was used to estimate genetic parameters for the factors faecal egg-count (FEC), packed-cell volume (PCV) and body weight (BW) in Santa Inês lambs. Data from 119 female, offspring of nine rams, were collected between December, 2005 and December, 2006, from the experimental flock of Embrapa Tabuleiros Costeiros, the Brazilian Agricultural Research Corporation located in Frei Paulo, SE, Brazil. After weaning, females were drenched until the faecal egg count had dropped to zero. Two natural challenges were undertaken. FEC heritability was extremely variable, this increasing from 0.04 to 0.27 in the first challenge and from 0.01 to 0.52 during the second. PCV heritability peaks were 0.31 and 0.12 in the first and second challenges, respectively. In the second challenge, BW heritability was close to 0.90. The genetic correlations among these traits did not differ from zero. There is the possibility of increasing parasite resistance in Santa Inês by selecting those animals with lower FEC. Selection to increase resistance will not adversely affect lamb-growth, although lambs with a slow growth-rate may be more susceptible to infection
Restoration Effects of the Riparian Forest on the Intertidal Fish Fauna in an Urban Area of the Amazon River
Urbanization causes environmental impacts that threaten the health of aquatic communities and alter their recovery patterns. In this study, we evaluated the diversity of intertidal fish in six areas affected by urbanization (areas with native vegetation, deforested areas, and areas in process of restoration of vegetation) along an urban waterfront in the Amazon River. 20 species were identified, representing 17 genera, 14 families, and 8 orders. The different degrees of habitat degradation had a major effect on the composition of the fish fauna; the two least affected sectors were the only ones in that all 20 species were found. Eight species were recorded in the most degraded areas. The analysis revealed two well-defined groups, coinciding with the sectors in better ecological quality and degraded areas, respectively. The native vegetation has been identified as the crucial factor to the recovery and homeostasis of the studied ecosystem, justifying its legal protection and its use in the restoration and conservation of altered and threatened environments. These results reinforce the importance of maintaining the native vegetation as well as its restoration in order to benefit of the fish populations in intertidal zones impacted by alterations resulting from inadequate urbanization
Evidence of two lineages of the dengue vector Aedes aegypti in the Brazilian Amazon, based on mitochondrial DNA ND4 gene sequences
Genetic variation was estimated in ten samples populations of Aedes aegypti from the Brazilian Amazon, by using a 380 bp fragment of the mitochocondrial NADH dehydrogenase subunit 4 (ND4) gene. A total of 123 individuals were analyzed, whereby 13 haplotypes were found. Mean genetic diversity was slightly high (h = 0.666 ± 0.029; π = 0.0115 ± 0.0010). Two AMOVA analyses indicated that most of the variation (~70%-72%) occurred within populations. The variation found among and between populations within the groups disclosed lower, but even so, highly significant values. FST values were not significant in most of the comparisons, except for the samples from Pacaraima and Rio Branco. The isolation by distance (IBD) model was not significant (r = 0.2880; p = 0.097) when the samples from Pacaraima and Rio Branco were excluded from the analyses, this indicating that genetic distance is not related to geographic distance. This result may be explained either by passive dispersal patterns (via human migrations and commercial exchange) or be due to the recent expansion of this mosquito in the Brazilian Amazon. Phylogenetic relationship analysis showed two genetically distinct groups (lineages) within the Brazilian Amazon, each sharing haplotypes with populations from West Africa and Asia
The Fate of an Amazonian Savanna: Government Land-Use Planning Endangers Sustainable Development in Amapá, the Most Protected Brazilian State
Although Amapa´ is the most protected Brazilian state, the same level of protection does not extend to its savannas. These
are currently suffering increased pressure from threats including large-scale agriculture, particularly the expansion of soybean
plantations. In September 2016, the Government of Amapa´ presented a zoning proposal (Zoneamento Socioambiental do
Cerrado [ZSC]) that reserves most of the savannas for agricultural activities. Here, we outline how the methodology
employed is flawed because it does not include fauna surveys, evaluations of ecosystem services or an assessment of the
social importance of the savannas. The ZSC authors admit that, contrary to Brazilian legislation, the zoning was carried out
with the single intention of increasing agriculture production. Current knowledge indicates that Amapa´’s savannas are rich in
biodiversity, including endemic and threatened species, and are also home to a rich culture of traditional populations. These
savannas are important providers of ecosystem services that, if intact, could represent around US$ 1.52 billion annually. We
hold that the ZSC should be reformulated, with fair participation of stakeholders, in accordance with Brazil’s legal requirements.
At least 30% of the savannas should be protected, local family farming should be supported, and the rights of
traditional peoples must now be assured through recognition of their land rights
- …