Resistivity of non-Fermi liquid U2Pt2In under pressure

Non-Fermi liquid behaviour in single-crystalline U2Pt2In has been studied by means of resistivity experiments (I||c) under hydrostatic pressure (P<1.5 GPa). At ambient pressure the resistivity rho(T) follows a power law rho~T^alpha with alpha~0.5. Upon applying pressure alpha increases. For P>1 GPa a minimum develops in rho(T). A study of the field dependence of the minimum confirms its magnetic origin. The ratio c/a is proposed as the effective control parameter, rather than the unit cell volume.Comment: 5 pages (incl. 2 figures), submitted to SCES'99, Nagan

Methodology for Optimization of Polymer Blends Composition

The research of polymer blends, or alloys, has experienced enormous growth in size and sophistication in terms of its scientific base, technology and commercial development (Paul &amp; Bucknall, 2000). As a consequence two very important issues arise: the increased availability of new materials and the need for materials with better performance. Polymer blends are polymer systems originated from the physical mixture of two or more polymers and/or copolymers, without a high degree of chemical reactions between them. To be considered a blend, the compounds should have a concentration above 2% in mass of the second component (Hage &amp; Pessan, 2001; Ihm &amp; White, 1996). However, the commercial viability of new polymers has begun to become increasingly difficult, due to several factors. The advantages of polymer blends lie in the ability to combine existing polymers into new compositions obtaining in this way, materials with specific properties. This strategy allows for savings in research and development of new materials with equivalent properties, as well as versatility, simplicity, relatively low cost (Koning et al., 1998) and faster development time of new materials (Silva, 2011). Rossini (2005) mentions that economically and environmentally, a very viable alternative is to replace the recycling of pure polymers by mixtures of discarded materials. Mechanical recycling causes the breakdown of polymer chains, which impairs the properties of polymers. This degradation is directly proportional to the number of cycles of recycling. Therefore, the blend of two or more discarded polymers can be a realistic alternative, since it can result in materials with very interesting properties, at a low cost. Besides its inexpensiveness, this choice is also a smart solution to the reutilization of garbage. Postconsumption package disposal always occurs in a disorderly manner and without regard for the environment. The recycling process becomes increasingly more important and necessary to remediate environmental impact. According Pang et al. (2000) apud Marconcini &amp; Ruvolo Filho (2006) polyolefins such as high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) and polyesters such as poly (ethylene terephthalate) (PET) are classes of thermoplastics that have been widely used in packaging and constitute a large part of post-consumer waste. The recycling of these materials and their mechanical characterization anticipating the possibility of a new cycle of life in the form of new products is challenging, although technologically and environmentally correct (Marconcini &amp; Ruvolo Filho, 2006). The polymer blends can be obtained basically in two ways (Rossini, 2005):  By dissolving the polymers in a good solvent, common to them, and subsequently letting the solvent evaporate; and  In a mixer where the working temperature is high enough to melt or mollify the polymeric components, without causing degradation of the same. According to Wessler (2007), the polymer blends may be miscible or immiscible. The miscibility is the most important property to be analyzed in a blend, given that all other system properties depend on the number of phases, their morphology and adhesion between them. The miscibility term is directly related to the solubility, i.e., a blend is miscible when the polymers dissolve in each other mutually (Silva, 2011). The immiscible between the various engineering polymers is a limiting factor for its production. Thus, it is necessary to use compatibilization agents for their production. Computational modeling has become increasingly popular. The main objective of models is to assist process optimization with minimal investment of time and resources for experimental work. Most techniques are classified into two main groups: physical models and statistical models as shown by Malinov &amp; Sha (2003). Statistical methods are chosen according to research objectives. There are several multivariate analysis methods for purposes quite different from each other. The desired value and quality of one or more product characteristics can be obtained via experiment analysis and DOE. These methods help determining optimal settings and controllable factors of a process such as: temperature, pressure, amount of reagents, operating time, etc.. When compared to the method of trial and error, DOE also allows a reduction of the number of required tests, and savings in time, labor and money. An important application of DOE is the optimization of experimental formulations as, for example, the composition of mixtures. The formulation development is a fundamental part of the food industry, chemicals, plastics, rubber, paints, medicines, and the like. In materials science, it is important to understand the correlation between material processing, microstructure and properties that enable the optimization of process parameters and compositions of materials to achieve the desired combination of properties, according Malinov &amp; Sha (2003). The problem presented here is to determine the fraction of each polymer blend component, and to determine the agent or, in some cases, an agents system, when it is necessary to use more than one compatibilizing agent. Thus, this text studies the effect of factors, for example, amount of polypropylene, additive type, and amount of additive in the composition of polymer blends, i.e., the optimal polymer blends formulation using factorial design

Sensitivity of precipitation forecasts to convective parameterization in the October 2007 Flash Flood in the Valencia Region (Eastern Spain)

The Valencia region, on the Mediterranean coast of the Iberian Peninsula, is an area prone to torrential rains, especially the north of Alicante province and the south of Valencia province. In October 2007, a torrential rain event with accumulated rainfall values exceeding 400 mm in less than 24 h affected the aforementioned areas, producing flash floods that caused extensive economic losses and human casualties. Several simulations of this rain event have been performed with the Regional Atmospheric Modeling System (RAMS) to test the influence of the different convective parameterization scheme implemented in the model on the precipitation forecast

Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix

Micrometer width and nanometer thick wires with different shapes were produced \approx 3~\upmum below the surface of a diamond crystal using a microbeam of He$^+$ ions with 1.8~MeV energy. Initial samples are amorphous and after annealing at $T\approx 1475$~K, the wires crystallized into a graphite-like structures, according to confocal Raman spectroscopy measurements. The electrical resistivity at room temperature is only one order of magnitude larger than the in-plane resistivity of highly oriented pyrolytic bulk graphite and shows a small resistivity ratio($\rho(2{\rm K})/\rho(315{\rm K}) \approx 1.275$). A small negative magnetoresistance below $T=200$~K was measured and can be well understood taking spin-dependent scattering processes into account. The used method provides the means to design and produce millimeter to micrometer sized conducting circuits with arbitrary shape embedded in a diamond matrix.Comment: 12 pages, 5 figures, to be published in Journal of Physics D: Applied Physics (Feb. 2017

Magnetic quantum critical point and superconductivity in UPt3 doped with Pd

Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find that the critical Pd concentration for the emergence of the large-moment antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic quantum critical point in the phase diagram, which coincides with the critical point for superconductivity, provides evidence for ferromagnetic spin-fluctuation mediated odd-parity superconductivity, which competes with antiferromagnetic order.Comment: 4 pages (includes 3 figures); postscript fil

Magnetic quantum critical point and superconductivity in UPt3 doped with Pd

Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find that the critical Pd concentration for the emergence of the large-moment antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic quantum critical point in the phase diagram, which coincides with the critical point for superconductivity, provides evidence for ferromagnetic spin-fluctuation mediated odd-parity superconductivity, which competes with antiferromagnetic order.Comment: 4 pages (includes 3 figures); postscript fil

Proteção dos frutos do abacaxi ao ataque de Strymon megarus (Godt., 1824) utilizando óleo essencial rico em dilapiol.

O óleo essencial de Piper aduncum L. apresenta potencial de uso inseticida relatado em vários trabalhos realizados em condições de laboratório. No estado do Acre, esta piperácea é abundante e a produção do óleo em escala comercial apresenta viabilidade econômica. O efeito inseticida desse óleo essencial, rico em dilapiol, foi avaliado ao nível de campo, no controle da broca-do-abacaxi, Strymon megarus (Godt., 1824), por meio de um experimento em blocos casualizados com 7 repetições dos seguintes tratamentos: a) óleo de P. aduncum (75,3% de dilapiol) a 1,5 L/ha; b) inseticida comercial a base de deltametrina a 300 mL/ha e c) testemunha (pulverização com água). A cultivar regional utilizada foi a Rio Branco plantada em fileiras duplas no espaçamento de 1,20m x 0,50 m x 0,50m. Adotou-se como parcela experimental 8 fileiras de 10 m de comprimento cada, correspondendo a 160 plantas (frutos). A uniformização do florescimento foi realizada por indução com carbureto de cálcio. As pulverizações dos tratamentos e a contagem dos frutos com sintomas de ataque da broca foram realizadas quinzenalmente a partir do florescimento, totalizando sete avaliações. A comparação do número médio de frutos atacados foi realizada pelo teste de Tukey a 5% de probabilidade. Não houve diferença significativa dentro de cada época de avaliação, entre o número de frutos atacados por S. megarus em plantas tratadas com o óleo de P. aduncum e o inseticida a base de deltametrina, que mantiveram, respectivamente, o nível de danos entre 13% e 6% do total de frutos avaliados. Tais valores diferiram significativamente da testemunhada (60% de frutos danificados). Desta forma, pode-se considerar promissora a utilização do óleo essencial de P. aduncum na proteção de frutos de abacaxi contra a broca dos frutos, S. megarus.Projeto 03.10.01.026.00.0