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The equilibrium partitioning of Na and K between alkali feldspar and NaCl–KCl salt melt was determined at 800 ∘ C, 850 ∘ C, 900 ∘ C, 950 ∘ C and 1000 ∘ C and close to ambient pressure. Four different natural gem-quality alkali feldspars with low degree of Al–Si ordering covering the range from orthoclase to high sanidine and with slightly different minor element concentrations were used as starting materials. The partitioning curves obtained for the four feldspars are indistinguishable indicating that Na–K partitioning independent of the differences of Al–Si ordering state and minor element concentrations existing amongst these feldspars. A sub-regular two parameter Margules type solution model was fitted to the partitioning data, and the excess Gibbs energy describing the thermodynamic non-ideality of the alkali feldspar solid-solution and the respective Margules parameters W gK and W g including their temperature dependence expressed as W g = W h - T W s were determined: W gK = 19754 ± 3140 J · mol - 1 - T · 2.33 ± 2.67 J · mol - 1 · K - 1 W g = 14916 ± 4272 J · mol - 1 - T · 3.55 ± 3.64 J · mol - 1 · K - 1 The corresponding solvus has a critical temperature slightly above 650 ∘ C and is well comparable with earlier direct experimental determinations of the low-sanidine-albite solvus curve. Comparison of the vibrational excess entropy determined from low-temperature heat capacity measurements with the total excess entropy derived from the temperature dependence of the excess Gibbs energy yields a negative configurational contribution to the excess entropy pointing towards short-range Na–K ordering on the alkali site.

The study was conducted to investigate the impact of Ca(NO3)2 on  different levels of salt-stress in date palm. Three-years-old date palm plants were subjected to four NaCl levels: 50, 100, 150 and 200 mM. The saline solutions were supplemented with 0, 5, 10 and 20 mM Ca(NO3)2. The combined NaCl/Ca(NO3)2 treatments were conducted over a period of 10 weeks. Control plants were only subjected to the four salinity levels with no Ca (NO3)2 addition. Results showed an inhibitory effect of salinity on almost all plants' parameters under investigation, mainly the accumulation of ions such as N, K, Ca, plant dry weight, chlorophyll and net photosynthesis rate. Addition of Ca (NO3)2 in the solution was more beneficial when added in a moderate concentration (10 mM) compared to lower (5 mM) and higher (20 mM) under all salinity levels. The addition of 10 mM Ca (NO3)2 noticeably enhanced chlorophyll content under 50 mM Na Cl (2.5 mg/100 cm2) and 150 mM NaCl (2 mg/100 cm2). In addition, 10 mM Ca (NO3)2 reduced the accumulation of Na and Cl in plant parts. For instance, in trees subjected to 10 mM Ca (NO3)2, Cl content in leaves and stems under 50 mM Na Cl were 0.23% and 0.65%, respectively. On the other hand, Cl content under 100 mM Na Cl and 200 mM Na Cl were lower compared to their corresponding control treatments. It seems that the use of Ca (NO3)2 had ameliorative effects on salt-stressed date palm plants when used with moderate concentrations.

Two olive (Olea europaea L.) genotypes, 'Frantoio' and 'Leccino', were exposed to increasing concentrations of NaCl (0-30-60-120 mM) in an aeroponic cultivation system for 60 days. Dry weights and sodium and potassium contents of apical and basal leaves, new and old wood, and roots were measured to determine Na uptake rate, Na translocation rate and K-Na selectivity ratio (SK,Na). 'Frantoio' showed a higher salt resistance than 'Leccino'. 'Frantoio' and 'Leccino' had a similar Na uptake rate, but largely differed for Na translocation to the shoot. Furthermore 'Frantoio' exhibited a higher K-Na selectivity than 'Leccino' at both whole plant level and above all at the level of shoot system. Resistance mechanism of 'Frantoio' is probably related to Na esclusion by roots and to the ability to maintain an appropriate K/Na ratio in actively growing tissues.

Estudos relacionados a marcha de absorção e partição de nutrientes nos órgãos do feijoeiro irrigado são escassos e de suma importância para o aprimoramento de modelos de adubação. O presente estudo teve como objetivo avaliar o crescimento por meio de produção de biomassa e absorção de nutrientes nos componentes e parte aérea do feijoeiro comum irrigado, na safra de inverno. O delineamento experimental foi em blocos casualizados, com três repetições e sete tratamentos constituídos de coletas de plantas e separação em folhas, haste, vagem+flor e grãos aos 10, 20, 30, 40, 50, 60 e 70 dias após a emergência do feijão. Após determinação da matéria seca foi estimado o conteúdo de N, P, K, Ca, Mg e S absorvidos pela parte aérea e componentes do feijoeiro. Foram ajustados modelos não lineares gaussiano e sigmoidal para caracterizar a produção de biomassa e absorção de nutrientes durante o crescimento do feijoeiro. A absorção de macronutrientes pelo feijoeiro seguiu a ordem decrescente, em kg ha-1: 138 de K, 112 de N, 66 de Ca, 16 de P, 11 de S e 7 de Mg, indicando a elevada absorção de K e N pela cultura e a necessidade de reposição do K em cobertura. Na fase inicial de crescimento as folhas foram responsáveis pelo acúmulo de 80% dos macronutrientes na parte aérea e ao final do cultivo, os grãos respondem pela exportação de 90, 75 e 65% do P, N e Mg absorvidos pelo feijoeiro, indicando a elevada taxa de exportação destes macronutrientes.

Os tratamentos térmicos de têmpera e particionamento (Q&P) vem sendo largamente estudados, uma vez que tem sido relatado na literatura uma melhora nas propriedades mecânicas dos aços após esses tratamentos. Busca-se, então, analisar os efeitos do mesmo, em aços API usados no revestimento de poços de petróleo; e na condução de óleo e gás (aço API 5CT e aço API 5L, respectivamente). Esses tratamentos têm como objetivo a formação de uma microestrutura que consiste, normalmente, numa matriz martensítica com considerável teor de austenita retida (ɤR ). Desta forma, foi desenvolvida uma rota de tratamentos Q&P, empregando-se diferentes temperaturas de particionamento, em três aços API com aplicações na indústria petrolífera. As influências desses tratamentos nas propriedades mecânicas dos aços foram analisadas, via ensaios de tração, impacto Charpy e microdureza Vickers, e comparadas com os resultados obtidos ao se utilizar a rota habitual de tratamentos térmicos, de têmpera e revenimento (Q&T). Foram observadas melhoras na ductilidade, razão elástica e tenacidade ao impacto dos aços.

Sexual segregation in foraging is predicted from the great size disparity of male and female northern elephant seals, Mirounga angustirostris. Our aim was to test this prediction by measuring diving and foraging behavior, foraging locations, and distribution of the sexes during biannual migrations in the northeastern Pacific Ocean. Daily movements of 27 adult males and 20 adult females, during 56 migrations from Ano Nuevo, California, USA, were determined by Argos satellite telemetry via head-mounted platform transmitter terminals. Diving records were obtained with archival time-depth-speed recorders attached to the backs of seals that were recovered when the seals returned to the rookery. Pronounced sex differences were found in foraging location and foraging pattern, as reflected by horizontal transit speed and diving behavior. Males moved directly north or northwest at a mean speed of 90 ± 27 km/d to focal foraging areas along the continental margin ranging from coastal Oregon (534 km away) to the western Aleutian Islands (4775 km away). Males remained in these areas (mean size = 7892 km2) for 21-84% of their 4-mo stays at sea. The predominance of flat-bottom dives in these areas suggests concentrated feeding on benthic prey. Migration distance and estimated mass gain were positively correlated with male size, and individual males returned to the same area to forage on subsequent migrations. In contrast, females ranged across a wider area of the northeastern Pacific, from 38⚬to 60⚬N and from the coast to 172.5⚬E. Focal foraging areas, indicated by a reduction in swim speed to <0.4 m/s, were distributed over deep water along the migratory path, with females remaining on them a mean of 3.5 d before moving to another one. Jagged-bottom dives that tracked the deep scattering layer prevailed in these areas, suggesting that females were feeding on pelagic prey in the water column. Females took roughly similar initial paths in subsequent migrations, but large deviations from the previous route were observed. We conclude that there is habitat segregation between the sexes. Females range widely over deep water, apparently foraging on patchily distributed, vertically migrating, pelagic prey, whereas males forage along the continental margin at the distal end of their migration in a manner consistent with feeding on benthic prey.

Alimento é considerado o principal eixo da partilha de nicho entre peixes, sendo um fator importante para a organização de suas populações. Com o intuito de investigar essa assertiva para duas espécies filogeneticamente próximas, a dieta natural de dois peixes da família Heptapteridae, Rhamdioglanis transfasciatus e Rhamdia quelen foi caracterizada e comparada ao longo do curso longitudinal do rio Macaé. R. quelen foi classificada como carnívora, sendo crustáceos e peixes os itens mais importantes da sua dieta, ao passo que R. transfasciatus foi considerada invertívora, tendo consumido principalmente larvas de Trichoptera e de Diptera. A posição trófica calculada revelou que ambas as espécies são consumidoras secundárias, com valores um pouco maiores para R. quelen. As espécies podem ser consideradas generalistas, mas com algumas diferenças na estratégia alimentar adotada por suas populações: alguns grupos de indivíduos de R. quelen se comportaram de forma especialista, enquanto que a população de R. transfasciatus se comporta de forma generalista em sua maioria. Na comparação intraespecífica, a dieta de ambas foi muito semelhante entre as duas localidades, porém a sobreposição de nicho entre as populações das duas espécies foi quase nula nos locais de coocorrência, indicando a existência de partilha alimentar entre Rhamdia quelen e Rhamdioglanis transfasciatus no rio Macaé.

The reported partition coefficients of REE with calcite are reviewed and critically discussed. In some of the reported experimental sets, REE concentrations are found to be supersaturated with respect to individual REE2(CO3)3 but never to REE(OH)3. Although the solutions are unsaturated with respect to individual REY carbonates, REY including Y are incorporated in calcite surfaces, where they are overgrown by calcite. Charge balances may be obtained by building {REY–Na-(CO3)2}n or by exchange of 2Ca2+ against REY3+ + blank space calcite lattice. These surface compounds may either be homogeneously distributed or clustered. Both the size and frequency of clusters increase with [REY]/[Ca] or [ΣREY3+]/[Ca2+] in solution. If these surface precipitates are removed into solutions saturated with respect to ΣREE2(CO3)3, they start growing in the aqueous phase. In this case, the apparent DREY and kREY values decrease with increasing REY concentrations in solution. In previous studies, only the individual distribution coefficients are reported not considering that the entirety of REY determines their behavior in partitioning. Given enough time, these surface clusters equilibrate with the aqueous phase before being overgrown by calcite. In the double logarithmic plots of {REY}/{Ca} versus [REY]/[Ca] or [REY3+]/[Ca2+], two relationships evolve characterizing the REY distribution in marine calcite and experimental calcites grown in Mg2+-free solutions. The double logarithmic plots of partition coefficients of REYi3+ in calcite grown from seawater show a slope exceeding unity, whereas those from fluids without Mg2+ depict slopes less than unity being both in contrast to the Henderson–Kracek rule.

Conhecimentos sobre o acúmulo e a distribuição da fitomassa do feijoeiro comum, sob diferentes níveis de adubação, podem auxiliar no manejo da cultura. Este trabalho objetivou avaliar o crescimento, os índices fisiológicos e a produtividade de cultivares de feijão, sob diferentes níveis de adubação NPK. O experimento foi conduzido em um Nitossolo Vermelho distroférrico, no município de Botucatu, SP, no delineamento experimental de blocos casualizados, em parcelas subdivididas, com quatro repetições. As parcelas foram constituídas por seis tratamentos ('Pérola', sem adubação; 'Pérola', com 50% da adubação recomendada; 'Pérola', com 100% da adubação recomendada; 'IAC Alvorada', sem adubação; 'IAC Alvorada', com 50% da adubação recomendada e 'IAC Alvorada', com 100% da adubação recomendada) e, as subparcelas, por sete épocas de coletas no decorrer do ciclo. A adubação NPK aumentou os acúmulos de matéria seca, os componentes da produção e a produtividade de grãos dos cultivares Pérola e IAC Alvorada de forma semelhante. O cultivar IAC Alvorada apresentou maiores índices de área foliar e matéria seca de folhas, quando comparados com os de Pérola, sob adubação NPK recomendada, porém, sem esses índices refletirem-se em maior produtividade de grãos. O máximo acúmulo de matéria seca foi alcançado aos 80 DAE e a maior taxa de crescimento da cultura ocorreu aos 55 DAE, independentemente do tratamento.

Food is the main axis of niche partitioning among fishes, being an important factor for the organization of their populations. We herein investigate this premise for two closely related species, by characterization and comparison of the natural diet of two heptapterid fishes, Rhamdioglanis transfasciatus and Rhamdia quelen along the Macae River, Rio de Janeiro state, Southeastern Brazil. R. quelen was classified as carnivore, and the most important items of its diet were crustaceans and fishes. R. transfasciatus was classified as invertivore, as it ate mainly trichopteran and dipteran larvae. The calculation of the trophic position algorithm showed that both species are secondary consumers, but R. quelen had a slightly higher value. Both species can be considered as generalists but with differences of feeding strategies: some individuals of R. quelen behave as specialists, whereas most individuals of R. transfasciatus population act as generalists. Intraspecific comparisons revealed a similar diet of each species between the two sampling sites, however, the niche overlap between the populations of the two species was very low in the sites where both occurred, indicating the existence of resource partitioning between Rhamdia quelen e Rhamdioglanis transfasciatus in Macae river. [PUBLICATION ABSTRACT]