The magnetocaloric effect (MCE) is the basis for magnetic refrigeration, and can replace conventional gas compression technology due to its superior efficiency and environment friendliness. MCE materials must exhibit a large temperature variation in response to an adiabatic magnetic-field variation and a large isothermal entropic effect is also expected. In this respect, MnAs shows the colossal MCE, but the effect appears under high pressures. In this work, we report on the properties of Mn(1-x)Fe(x)As that exhibit the colossal effect at ambient pressure. The MCE peak varies from 285 K to 310 K depending on the Fe concentration. Although a large thermal hysteresis is observed, the colossal effect at ambient pressure brings layered magnetic regenerators with huge refrigerating power closer to practical applications around room temperature.

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Blends of soybean oil (SO) and fully hydrogenated soybean oil (FHSBO), with 10, 20, 30, 40, and 50% (w/w) FHSBO content were interesterified under the following conditions: 20 min reaction time, 0.4% sodium methoxide catalyst, and 500 rpm stirring speed, at 100°C. The original and interesterified blends were examined for triacylglycerol composition, thermal behavior, microstructure, crystallization kinetics, and polymorphism. Interesterification produced substantial rearrangement of the triacylglycerol species in all the blends, reduction of trisaturated triacylglycerol content and increase in monounsaturated-disaturated and diunsaturated-monosaturated triacylglycerols. Evaluation of thermal behavior parameters showed linear relations with FHSBO content in the original blends. Blend melting and crystallization thermograms were significantly modified by the randomization.Interesterification caused significant reductions in maximum crystal diameter in all blends, in addition to modifying crystal morphology. Characterization of crystallization kinetics revealed that crystal formation induction period (τ SFC ) and maximum solid fat content (SFC máx ) were altered according to FHSBO content in the original blends and as a result of the random rearrangement. Changes in Avrami constant (k) and exponent (n) indicated, respectively, thatas compared with the original blends-interesterification decreased crystallization velocities and modified crystallization processes, altering crystalline morphology and nucleation mechanism. X-ray diffraction analyses revealed that interesterification altered crystalline polymorphism. The interesterified blends showed a predominance of the β′ polymorph, which is of more interest for food applications.

Distortions produced in the unit cell of a nonlinear organic crystal under the influence of an applied electric field E are investigated by using synchrotron x-ray multiple diffraction (MD). A typical MD pattern shows numerous ͑hkl͒ secondary peaks and the position of each one is basically a function of the unit cell lattice parameters. Thus small changes in any parameter due to a strain produced by E give rise to a corresponding variation in the ͑hkl͒ peak position. The method was applied to the meta-nitroaniline (mNA) crystal and we were able to determine three piezoelectric coefficients. [S0031-9007(98)07912-5] PACS numbers: 77.65.Bn, 61.10. -i, 77.84.JdLarge high quality noncentrosymmetric organic single crystals have been grown in recent years mainly with the aim of exploiting their nonlinear optical properties, particularly for second harmonic generation and signal modulation via the linear electro-optic effect. The crystals, by virtue of their highly polar, anisotropic structures might also be expected to exhibit substantial piezoelectric and, in some cases, pyroelectric effects, and these responses are related to a range of interesting phenomena, including the optoacoustic and photorefractive effects.X-ray multiple diffraction (MD) is a technique which has been used by several authors [1-5] to provide a physical solution to the important crystallographic phase problem. Besides, it is closely related to the crystal lattice symmetry which provides three-dimensional information and then is inherently very sensitive to small changes in lattice parameters. A typical single MD pattern shows numerous multiple diffraction peaks, each one carrying information on one particular direction within the crystal. A review of the technique can be found in Ref. [6]. In this paper we present some preliminary results of investigations of the distortions produced in an organic crystal by the application of an electric field. We have measured both multiple and two-beam diffraction peak shifts. The combination of these types of diffraction should provide a versatile method of obtaining complete information on the piezoelectric tensors of crystals of the more anisotropic systems where there are a number of nonequivalent coefficients. The amount of information that can be extracted from one such experimental arrangement is greatly increased if some of the numerous multiple diffraction peaks which appear in a single MD pattern are investigated in addition to the two-beam case.In the following we discuss the theory relating the piezoelectric distortion of the lattice to the shifts in the diffraction peaks, using as an example one organic nonlinear optical crystal mounted in a particular orientation which has been found practicable. Experimental results already obtained are sufficient to establish the feasibility of the technique, as described later on. The organic crystal which has been examined is the meta-nitroaniline (mNA) [7,8] which crystallizes in the orthorhombic system with point group mm2 and lattice parameters ͑a 6.501 Å,...

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