61 research outputs found
Determination of superconducting anisotropy from magnetization data on random powders as applied to LuNiBC, YNiBC and MgB
The recently discovered intermetallic superconductor MgB2 appears to have a
highly anisotopic upper critical field with Hc2(max)/Hc2(min} = \gamma > 5. In
order to determine the temperature dependence of both Hc2(max) and Hc2(min) we
propose a method of extracting the superconducting anisotropy from the
magnetization M(H,T) of randomly oriented powder samples. The method is based
on two features in dM/dT the onset of diamagnetism at Tc(max), that is commonly
associated with Hc2, and a kink in dM/dT at a lower temperature Tc(min).
Results for LuNi2B2C and YNi2B2C powders are in agreement with anisotropic Hc2
obtained from magneto-transport measurements on single crystals. Using this
method on four different types of MgB2 powder samples we are able to determine
Hc2(max)(T) and Hc2(min)(T) with \gamma \approx 6
Emoções, “stress”, ansiedade e “coping": estudo qualitativo com treinadores de nível internacional
A influência dos fatores e processos psicológicos no desempenho desportivo dos atletas está, de uma forma geral, amplamente demonstrada; todavia, poucas investigações procuraram estudar esta relação nos treinadores. Neste sentido, empregando uma entrevista semi-estruturada, a presente investigação procurou, junto de seis treinadores de elite com idades compreendidas entre os 55 e os 63 anos (M = 59 ± 3,03) de diversas modalidades, identificar as características/competências psicológicas mais importantes para o sucesso desportivo, as principais fontes de “stress” e ansiedade experienciadas e as estratégias de “coping” a que recorriam em situações estressantes e/ou problemáticas, adicionalmente, pretendeu explorar o papel de outras emoções no seu desempenho. Os resultados revelaram que: 1) a motivação era uma das competências/características psicológicas percepcionadas pelos treinadores como mais importantes para o sucesso; 2) as principais fontes de “stress” estavam relacionadas com preocupações com o desempenho dos atletas, sendo comuns a diferentes modalidades; 3) os treinadores recorriam a diversas estratégias de “coping” em simultâneo, geralmente adaptativas; e 4) para além da ansiedade, outras emoções, positivas e negativas, pareciam influenciar o desempenho dos treinadores.Fundação para a Ciência e Tecnologia (FCT
WEST: A northern California study of the role of wind-driven transport in the productivity of coastal plankton communities
Hydrography, nutrients and chlorophyll during El Niño and La Niña 1997-99 winters in the Gulf of the Farallones, California
Nutrient and chlorophyll concentrations were measured in January 1997, 1998 and 1999 in the Gulf of the Farallones, CA at locations stretching north/south from Point Reyes to Half Moon Bay, and seaward from the Golden Gate to the
Farallon Islands. The cruises were all carried out during periods of high river flow, but under different climatological
conditions with 1997 conditions described as relatively typical or ‘neutral/normal’, compared to the El Niño warmer
water temperatures in 1998, and the cooler La Niña conditions in 1999. Near-shore sea-surface temperatures ranged from cold (9.5–10.5°C) during La Niña 1999, to average (11–13°C) during 1997 to warm (13.5–15°C) during El Niño 1998. Nutrients are supplied to the Gulf of the Farallones both from San Francisco Bay (SFB) and from oceanic sources, e.g. coastal upwelling near Point Reyes. Nutrient supplies are strongly influenced by the seasonal cycle of fall calms,
with storms (commencing in January), and the spring transition to high pressure and northerly upwelling favorable
winds. The major effect of El Niño and La Niña climatic conditions was to modulate the relative contribution of SFB to nutrient concentrations in the coastal waters of the Gulf of the Farallones; this was intensified during the El Niño winter and reduced during La Niña. During January 1998 (El Niño) the oceanic water was warm and had low or
undetectable nitrate, that did not reach the coast. Instead, SFB dominated the supply of nutrients to the coastal waters Additionally, these data indicate that silicate may be a good tracker of SFB water. In January, delta outflow into SFB
produces low salinity, high silicate, high nitrate water that exits the bay at the Golden Gate and is advected northward
along the coast. This occurred in both 1997 and 1998. However during January 1999, a La Niña, this SFB feature was
reduced and the near-shore water was more characteristic of high salinity oceanic water penetrated all the way to the
coast and was cold (10°C) and nutrient rich (16 μM NO3, 30 μM Si(OH)4). January chlorophyll concentrations ranged
from 1–1.5 μg l 1 in all years with the highest values measured in 1999 (2.5–3 μg l 1) as a result of elevated nutrients
in the area. The impact of climatic conditions on chlorophyll concentrations was not as pronounced as might be expected
from the high temperatures and low nutrient concentrations measured offshore during El Niño due to the sustained
supply of nutrients from the Bay supporting continued primary production
Physical, Chemical, and Productivity Data From an Investigation of the Northeastern Tropical Pacific Ocean: RV Thomas G. Thompson Cruise 026 (PONCHO): 3 January-14 March 1968
National Science Foundation Grant GA-644 and Office of Naval Research Contract Nonr-477(37) Project NR-083-01
Nitrogen kinetics of algal populations in two gulfs adjoining the Attica peninsula, one receiving effluents
4 pagesPeer reviewe
Variaciones en la actividad de reductasa de nitrato en el fitoplancton
11 pages, 4 figures, 2 tables[EN] The study of biochemical processes in the ocean can be facilitated by analysis of the enzyme systems that control them. Such analysis may provide explanations for oceanographic phenomena by facilitating the location of the sites and the determination of the rates of nitrate reduction, sulfate reduction, ammonia oxidation, photosynthesis, and respiration. [...] Skeletonema costatum, Amphora sp., Platymoras sp., Corethron histrix, Rhizosolenia fragilissima [...][ES] Uno de los procesos más importantes en el mar es la asimilación del nitrato por el fitoplancton. El análisis de la actividad de las enzimas que reducen el nitrato en fitoplancton puede permitir conocer su capacidad para asimilar nitrato y la velocidad de esta asimilación. [...
The kinetics of nitrate and ammonia uptake by natural populations of marine phytoplankton
Modeling Phytoplankton New Production in the Peru Upwelling from Nitrate Reductase Activity and Light
V Simposio Internacional de Ciencias del Mar, 20-22 July 2016, Alicante.-- 2 pages, 3 figuresOceanic New Production is limited by nitrate (NO3-), ammonium (NH4+), and light. Measuring it by 15NO3- incubations is the current gold-standard, but the data acquisition rate is slow. Calculating it from plankton nitrate reductase activity (NR) is an inexpensive alternative with a higher data acquisition rate. Here, we calculate phytoplankton new production for the Peru upwelling ecosystem from measurements of NR activity using an enzyme kinetic model based on lighth -limitation. Calculations for the C-Line section at 155°S find new production ranging from 0.1 to 0.4 micro M N h-1 at the shelf edge and compares well to gross primary productivity when Redfield equivalents are used for N-C conversiion. JASON-CUEA expedition data for r September 1976 were usedThis study was supported by CUEA-12 (OCE75-23718) to ttp and BIOMBA (CTM2012-2729-MAR) to mgPeer Reviewe
- …