421 research outputs found
The Stroke-related Effects of Hip Flexion Fatigue on Over Ground Walking
Individuals post stroke often rely more on hip flexors for limb advancement during walking due to distal weakness but the effects of muscle fatigue in this group is not known. The purpose of this study was to quantify how stroke affects the influence of hip flexor fatigue on over ground walking kinematics and performance and muscle activation. Ten individuals with chronic stroke and 10 without stroke (controls) participated in the study. Maximal walking speed, walking distance, muscle electromyograms (EMG), and lower extremity joint kinematics were compared before and after dynamic, submaximal fatiguing contractions of the hip flexors (30% maximal load) performed until failure of the task. Task duration and decline in hip flexion maximal voluntary contraction (MVC) and power were used to assess fatigue. The stroke and control groups had similar task durations and percent reductions in MVC force following fatiguing contractions. Compared with controls, individuals with stroke had larger percent reductions in maximal walking speed, greater decrements in hip range of motion and peak velocity during swing, greater decrements in ankle velocity and lack of modulation of hip flexor EMG following fatiguing dynamic hip flexion contractions. For a given level of fatigue, the impact on walking function was more profound in individuals with stroke than neurologically intact individuals, and a decreased ability to up regulate hip flexor muscle activity may contribute. These data highlight the importance of monitoring the effect of hip flexor muscle activity during exercise or performance of activities of daily living on walking function post stroke
New anti-perovskite-type Superconductor ZnNyNi3
We have synthesized a new superconductor ZnNyNi3 with Tc ~3 K. The crystal
structure has the same anti-perovskite-type such as MgCNi3 and CdCNi3. As far
as we know, this is the third superconducting material in Ni-based
anti-perovskite series. For this material, superconducting parameters,
lower-critical field Hc1(0), upper-critical field Hc2(0), coherence length
x(0), penetration depth l(0), and Gintzburg -Landau parameter k(0) have been
experimentally determined.Comment: 13 pages, 3 figures, 1 tabl
Ideal Spin Filters: Theoretical Study of Electron Transmission Through Ordered and Disordered Interfaces Between Ferromagnetic Metals and Semiconductors
It is predicted that certain atomically ordered interfaces between some
ferromagnetic metals (F) and semiconductors (S) should act as ideal spin
filters that transmit electrons only from the majority spin bands or only from
the minority spin bands of the F to the S at the Fermi energy, even for F with
both majority and minority bands at the Fermi level. Criteria for determining
which combinations of F, S and interface should be ideal spin filters are
formulated. The criteria depend only on the bulk band structures of the S and F
and on the translational symmetries of the S, F and interface. Several examples
of systems that meet these criteria to a high degree of precision are
identified. Disordered interfaces between F and S are also studied and it is
found that intermixing between the S and F can result in interfaces with spin
anti-filtering properties, the transmitted electrons being much less spin
polarized than those in the ferromagnetic metal at the Fermi energy. A patent
application based on this work has been commenced by Simon Fraser University.Comment: RevTeX, 12 pages, 5 figure
Gain and Loss Learning Differentially Contribute to Life Financial Outcomes
Emerging findings imply that distinct neurobehavioral systems process gains and losses. This study investigated whether individual differences in gain learning and loss learning might contribute to different life financial outcomes (i.e., assets versus debt). In a community sample of healthy adults (n = 75), rapid learners had smaller debt-to-asset ratios overall. More specific analyses, however, revealed that those who learned rapidly about gains had more assets, while those who learned rapidly about losses had less debt. These distinct associations remained strong even after controlling for potential cognitive (e.g., intelligence, memory, and risk preferences) and socioeconomic (e.g., age, sex, ethnicity, income, education) confounds. Self-reported measures of assets and debt were additionally validated with credit report data in a subset of subjects. These findings support the notion that different gain and loss learning systems may exert a cumulative influence on distinct life financial outcomes
The Affective Impact of Financial Skewness on Neural Activity and Choice
Few finance theories consider the influence of “skewness” (or large and asymmetric but unlikely outcomes) on financial choice. We investigated the impact of skewed gambles on subjects' neural activity, self-reported affective responses, and subsequent preferences using functional magnetic resonance imaging (FMRI). Neurally, skewed gambles elicited more anterior insula activation than symmetric gambles equated for expected value and variance, and positively skewed gambles also specifically elicited more nucleus accumbens (NAcc) activation than negatively skewed gambles. Affectively, positively skewed gambles elicited more positive arousal and negatively skewed gambles elicited more negative arousal than symmetric gambles equated for expected value and variance. Subjects also preferred positively skewed gambles more, but negatively skewed gambles less than symmetric gambles of equal expected value. Individual differences in both NAcc activity and positive arousal predicted preferences for positively skewed gambles. These findings support an anticipatory affect account in which statistical properties of gambles—including skewness—can influence neural activity, affective responses, and ultimately, choice
The Job Search Intensity Supply Curve: How Labor Market Conditions Affect Job Search Effort
During the Great Recession of 2007, unemployment reached nearly 10 percent and the ratio of unemployment to open positions (as measured by the Help Wanted OnLine Index) more than tripled. The weak labor market prompted an unprecedented extension in the length of time in which a claimant can collect unemployment insurance (UI) to 99 weeks, at an expense to date of $226.4 billion. While many claim that extending UI during a recession will reduce search intensity, the effect of weak labor market conditions on search remains a mystery. As a result, policymakers are in the dark as to whether UI extensions reduce already low search effort during recessions or perhaps decrease excessive search, which causes congestion in the labor market. At the same time, modelers of the labor market have little empirical justification for their assumptions on how search intensity changes over the business cycle. This paper develops a search model where the impact of macro labor market conditions on a worker’s search effort depends on whether these two factors are substitutes or complements in the job search process. Parameter estimates of the structural model using a sample of unemployment spells from the National Longitudinal Survey of Youth 1997 indicate that macro labor market conditions and individual search effort are complements and move together over the business cycle. The estimation also reveals that more risk-averse and less wealthy individuals exhibit less search effort
Under pressure: Response urgency modulates striatal and insula activity during decision-making under risk
When deciding whether to bet in situations that involve potential monetary loss or gain (mixed gambles), a subjective sense of pressure can influence the evaluation of the expected utility associated with each choice option. Here, we explored how gambling decisions, their psychophysiological and neural counterparts are modulated by an induced sense of urgency to respond. Urgency influenced decision times and evoked heart rate responses, interacting with the expected value of each gamble. Using functional MRI, we observed that this interaction was associated with changes in the activity of the striatum, a critical region for both reward and choice selection, and within the insula, a region implicated as the substrate of affective feelings arising from interoceptive signals which influence motivational behavior. Our findings bridge current psychophysiological and neurobiological models of value representation and action-programming, identifying the striatum and insular cortex as the key substrates of decision-making under risk and urgency
Efeito do tempo de repouso sobre produção e qualidade do leite de vacas mantidas em pastagem polifítica e sistema de Pastoreio Racional Voisin
Na pecuária leiteira, a produção de leite com maiores teores de compostos benéficos à saúde, tais como os ácidos graxos poliinsaturados e carotenoides, encontrados com abundância em produção à pasto, são um diferencial no mercado. Desse modo, este trabalho teve como objetivo avaliar o efeito de pastagens manejadas com três diferentes intervalos de corte, 14 dias (T14), 28 dias (T28) e 56 dias (T56) na composição do leite produzido. Os animais foram divididos em seis grupos e as pastagens manejadas nos respectivos intervalos. Para os compostos de interesse no leite, nos grupos T14 e T28 foram encontrados maiores teores de luteína (P<0,05) e do ácido graxo C20:5 (P<0,005) comparados ao T56. Para os demais parâmetros avaliados (demais ácidos graxos, carotenoides e vitaminas A e E), não se encontrou diferenças entre os tratamentos. Diante disso, o menor intervalo de corte resultou em um leite mais saudável.In dairy farming, the production of dairy products with greater concentrations of benefitial health compounds can add value to the product, such as carotenoids and polyunsaturated fatty acids. The aim of this study is to evaluate the effect of pasture management with three different cutting intervals (14, 28 and 56 days) on selected milk compounds. Animals were divided in 6 groups in a double latin-square design. Compounds of interest in milk were higher in T14 and T28 than T56 for lutein (P = 0.02) and C20:5 (P<0.005). Conjugated linoleic acid (CLA), vaccenic acid, omega 3 and 6, the ratio (omega6 / omega3), tocopherol, retinol and beta-carotene did not differ between treatments. There was no difference between T14 and T28, but T56 was different from both treatments for the diet consumed, bite rate and some milk components. Overall, the results show that the shorter cutting interval resulted in healthier milk.Eje: A1 Sistemas de producción de base agroecológica (Trabajos científicos)Facultad de Ciencias Agrarias y Forestale
Correspondence: Are Cognitive Functions Localizable? Colin Camerer et al. versus Marieke van Rooij and John G. Holden
The Fall 2011 issue of this journal published a
two-paper section on “Neuroeconomics.” One
paper, by Ernst Fehr and Antonio Rangel, clearly
and concisely summarized a small part of the fast-growing
literature. The second paper, “It’s about
Space, It’s about Time, Neuroeconomics, and the
Brain Sublime,” by Marieke van Rooij and Guy Van
Orden, is beautifully written and enjoyable to read,
but misleading in many critical ways. A number
of economists and neuroscientists working at the
intersection of the two fields shared our reaction
and have signed this letter, as shown below. Some of
the paper’s descriptions of empirical findings and
methods in neuroeconomics are incomplete, badly
out of date, or flatly wrong. In studies the authors
describe in detail, their skeptical interpretations
have often been refuted by published data, old and
new, that they overlook
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