Effect of exchange interaction on superparamagnetic relaxation

We use Langer's approach to calculate the reaction rate of a system of two (classical) spins interacting via the exchange coupling $J$ in a magnetic field $H$, with uniaxial anisotropy of constant $K$. We find a particular value of the exchange coupling, that is $j\equiv J/K = j_c\equiv 1-h^2$, where $h\equiv H/2K$, which separates two regimes corresponding to a two-stage and one-stage switching. For $j\gg j_c$ the N\'eel-Brown result for the one-spin problem is recovered.Comment: 7 pages, 2 eps figures, fig.1 of better quality can be provided upon reques

Memory and superposition in a spin glass

Non-equilibrium dynamics in a Ag(Mn) spin glass are investigated by measurements of the temperature dependence of the remanent magnetisation. Using specific cooling protocols before recording the thermo- or isothermal remanent magnetisations on re-heating, it is found that the measured curves effectively disclose non-equilibrium spin glass characteristics such as ageing and memory phenomena as well as an extended validity of the superposition principle for the relaxation. The usefulness of this "simple" dc-method is discussed, as well as its applicability to other disordered magnetic systems.Comment: REVTeX style; 8 pages, 4 figure

Extrinsic Curvature Embedding Diagrams

Embedding diagrams have been used extensively to visualize the properties of curved space in Relativity. We introduce a new kind of embedding diagram based on the {\it extrinsic} curvature (instead of the intrinsic curvature). Such an extrinsic curvature embedding diagram, when used together with the usual kind of intrinsic curvature embedding diagram, carries the information of how a surface is {\it embedded} in the higher dimensional curved space. Simple examples are given to illustrate the idea.Comment: 22 pages, 4 figure

Avaliação da toxicidade de Piraclostrobin, Epoxiconazol e sua mistura em alga Pseudokirchneriella subcapitata.

Resumo: Estudou-se o efeito toxicológico (inibição de crescimento) de formulações fungicidas à base de piraclostrobin e epoxiconazol, isoladamente e em formulação conjugada, sobre a alga Pseudokirchneriella subcapitata mediante determinação da Concentração Efetiva Média (CE50-72 h) dos princípios ativos de cada uma das formulações. Foram encontrados valores de CE50- 72 h de 5,57 mg.L-1 para a formulação à base de piraclostrobin, de 1,14 mg.L-1 para a formulação à base de epoxiconazol e de 0,20 mg.L-1 para a formulação conjugada. O piraclostrobin apresentou menor toxicidade às algas em relação aos dados encontrados na literatura, o epoxiconazol resultados semelhantes e a mistura maior toxicidade. A análise isobolográfica e a determinação do Índice de Aditividade (IA) sugerem forte sinergismo da mistura quanto à sua ação tóxica sobre o organismo-teste. Esse fato realça a necessidade de revisão dos padrões limitantes desses fungicidas em corpos de água, os quais tendem a subestimar os efeitos adversos resultantes da combinação dos agentes tóxicos

Avaliação da toxicidade aguda de Piraclostrobin, Epoxiconazol e sua mistura em Daphnia similis.

No presente trabalho avaliou-se o efeito toxicológico (inibição da mobilidade) de formulações fungicidas à base de piraclostrobin e epoxiconazol, isoladamente e em formulação conjugada sobre Daphnia similis, mediante determinação da Concentração Efetiva Média (CE50-48h) de cada uma das formulações. Também foi determinado o possível efeito sinérgico ou antagônico que o uso conjugado dos dois fungicidas poderia exercer em relação à sua toxicidade. Foram encontrados valores de CE50-48h de 18,36 mg.L-1 para a formulação à base de piraclostrobin, de 89,98 mg.L-1 para a formulação à base de epoxiconazol e de 23,50 mg.L-1 para a formulação conjugada. Das três formulações estudadas, o piraclostrobin mostrou-se o mais tóxico para os organismos em estudo. A análise isobolográfica e a determinação do Índice de Aditividade (IA) sugerem que a mistura dos princípios ativos exerce apenas efeito toxicológico aditivo sobre o organismo-alvo

Energy Efficiency as a Tool for Preservation of Affordable Rental Housing: Evaluation of the Efficiency Emphasis in the MacArthur Foundations Window of Opportunity Initiative

Note: This evaluation is accompanied by a blog post by the RAND Corporation about the initiative. Access these related materials here: https://www.macfound.org/press/grantee-publications/evaluation-investments-energy-efficiency-through-window-opportunity-initiative.In the late 1990s, there was growing concern that the significant portion of subsidized rental homes that were coming to the end of their initial subsidy period would not obtain renewed subsidy and that the amount of affordable rental housing for low and middle-income families in metropolitan areas would fall to even lower numbers. Responding to this escalating concern, the MacArthur Foundation identified preservation of the existing stock of affordable multifamily rental housing as a pressing need. Consequently, the Foundation launched the Window of Opportunity: Preservation of Affordable Rental Housing initiative in 2000. The initiative would expand to become a 20-year effort, during which the Foundation awarded $214 million in grants and loans to a wide range of organizations including non-profit owners of affordable rental housing, state governments, researchers, financial institutions, industry associations, and advocates.By 2011, the Foundation and its Window of Opportunity borrowers and grantees had increasingly recognized that energy costs of multifamily rental properties could be better controlled. To this end, the Foundation opted to extend Window of Opportunity with an explicit focus on increasing the energy efficiency of subsidized and unsubsidized multifamily affordable housing. Between 2012-2015, the Foundation awarded$27.5 million through 39 grants or loans as a part of what we term the Window of Opportunity - Energy Efficiency. The loans were Program-Related Investments, which were low-interest loans to create new business models or grow mission-oriented businesses. The Window of Opportunity - Energy Efficiency activities comprised a little over 10 percent of the overall $214 million Window of Opportunity initiative

Xylem as well as phloem sustains severe damage due to feeding by the Russian wheat aphid

Investigation of comparative effects of feeding damage by the Russian wheat aphid (RWA, biotype SA1, Diuraphis noxia Mordvilko) on leaf blades of susceptible and resistant wheat cultivars (Triticum aestivum L. var Betta and Betta-Dn1 respectively) were carried out to establish the level of ultrastructural damage caused by this aphid and the possible limitation of damage induced which could be ascribed to the resistance gene Dn1 over the susceptible cultivar. Ultrastructurally, Betta-Dn1 sustained less damage to the vascular tissue as well as to the mesophyll during the experimental period. Both inter- and intracellular probes resulted in considerable saliva deposition as the aphids probed for suitable feeding sites. Salivary tracks were observed between and within mesophyll, bundle sheath cells as well as the vascular tissue, including the xylem. Disruption of organelles and cytoplasm resulted from cell probing and sheath deposition. Cell and organelle damage was more evident in the non-resistant Betta cultivar. The aphids probed for and fed from thin-walled sieve tubes preferentially. Few thick-walled sieve tubes showed evidence of either aphid probing or feeding-related damage. Saliva was deposited when the aphids probed inter- and intracellularly for feeding sites. The aphids appeared preferentially to probe for and feed from thin-walled sieve tubes, as few thick-walled sieve tubes showed evidence of damage. Vessels, apparently probed for water, contained watery saliva that encased the secondary walls and sealed pit membranes between probed vessels and xylem parenchyma. The xylem probed by the RWA was rendered non-functional, probably contributing to symptoms of leaf roll, chlorosis and necrosis, which were observed within two weeks of infestation in the susceptible Betta cultivar. This damage was limited in the resistant Betta-Dn1 cultivar during the same time frame

Avaliação da toxicidade aguda de Piraclostrobin, Epoxiconazol e sua mistura em Colossoma macropomum (Tambaqui).

Resumo: O presente trabalho avaliou o efeito toxicológico de formulações fungicidas à base de piraclostrobin e epoxiconazol, isoladamente e em formulação conjugada sobre Colossoma macropomum (tambaqui) por 96 horas através da determinação da Concentração Letal Média (CL50-96h) de cada uma das formulações. Foram encontrados valores de CL50-96h equivalentes a 0,018 mg L-1 para o piraclostrobin, 2,28 mg L-1 para o epoxiconazol e 0,021 mg L-1 para sua formulação conjugada. Das três formulações utilizadas, o piraclostrobin isoladamente mostrou-se o mais tóxico para os organismos estudados e o uso conjugado das duas substâncias nas concentrações estudadas apresentou um fraco efeito sinérgico

Toxicidade subcrônica de dois fungicidas e sua mistura na atividade de algumas enzimas de pacu.

Resumo: Estudou-se o efeito sobre a atividade de enzimas hepáticas do metabolismo intermediário, de conjugação e antioxidantes, decorrente da exposição do peixe pacu (Piaractus mesopotamicus) por 14 dias aos fungicidas epoxiconazol, piraclostrobina e à mistura dos mesmos. As atividades da fosfatase ácida (Pac) e superóxido dismutase (SOD) foram aumentadas significativamente (p<0,05) em relação ao controle nas exposições ao epoxiconazol na concentração de 22,8 g.L-1. Esta é equivalente a 1/100 da concentração letal media (CL50-96h) determinada em peixes. Com relação aos efeitos da piraclostrobina e à mistura epoxiconazol+piraclostrobina, não se observou decréscimo ou incremento das atividades das enzimas avaliadas. Atribuíram-se valores de 1,8 e 2,0 micrograma.L-1, respectivamente para piraclostrobina e a mistura epoxiconazol+piraclostrobina, como concentrações de efeito não observado (CENO). O valor deste parâmetro para o epoxiconazol seria equivalente a 2,28 micrograma.L-1, já que observou-se efeito na concentração imediatamente superior a esta. Os dados são relevantes na identificação de possíveis biomarcadores e no direcionamento de políticas publicas quanto ao estabelecimento de níveis máximos de poluentes na água para a proteção da biota aquática. Abstract: We studied the effect on the activity of hepatic enzymes that acts in the intermediary metabolism, conjugation of xenobiotics and as antioxidants, due to the exposure (14 days) of the pacu fish (Piaractus mesopotamicus) to the fungicides epoxiconazole, pyraclostrobin and its mixture. In the epoxiconazole exposure at 22.8 microgramg L-1, the activities of acid phosphatase (Pac) and superoxide dismutase (SOD) were increased significantly (p<0.05) compared to the control. This concentration is equivalent to 1/100 the median lethal concentration (LC50-96h) determined in fishes. There was no significant decrease or increase in the enzyme activities in fishes exposed to pyraclostrobin or pyraclostrobin+epoxiconazole mixture. We assigned values equivalent to 1.8 and 2.0 microgram L-1, respectively for pyraclostrobin and pyraclostrobin+epoxiconazole mixture, which would be regarded as the no observed effect concentration (NOEC). The value of this parameter to the epoxiconazole would be equivalent to 2.28 microgram L-1. Data are relevant in the identification of candidate biomarkers and in guiding public policies regarding the setting of maximum levels of pollutants in the water for protection of the aquatic biota