396 resultados para ASTRO-R3


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Title varies slightly.

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On verso: ASTRO; Co. B-4

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Mode of access: Internet.

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Publication suspended from July 1870-Jan. 1871

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Previous ed. entered under: United States. Bureau of the Census.

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Jakob Fromer

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von Dr. A. Sammter

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The human startle response is a sensitive, noninvasive measure of central nervous system activity that is Currently used in a wide variety of research and clinical settings. In this article, we raise methodological issues and present recommendations for optimal methods of startle blink electromyographic (EMG) response elicitation, recording, quantification, and reporting. It is hoped that this report Will foster more methodological validity and reliability in research using the startle response, Lis well Lis increase the detail with which relevant methodology is reported in publications using this measure.

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Aspergillus spp. produce aflatoxins in peanut, which poses a health risk to humans and animals, as well as affecting the marketability of peanuts. The current research found that more aflatoxin is produced under rain fed (RF) compared to irrigated (IRR) conditions, and was more predominant in juvenile (R3-5 stage) compared to older (R6-8 stage) pods. No aflatoxin was recorded in marketable pods of the Streeton cultivar in either of the growing conditions, whereas the cultivar NC-7 produced aflatoxin under RF conditions only. Sugars such as glucose, fructose and sucrose were positively correlated with total aflatoxins. It appears that Aspergillus utilises these simple carbohydrates as substrates in biosynthesis of aflatoxins.

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In this PhD study, the effects of the cation substitutions on the physical properties of pyroxenes have been discussed. The results of this work extend the knowledge on pyroxenes with different chemical compositions. These properties might be used in the development of ceramic pigments, advanced materials and for the mineralogical phase identification. First of all, the crystallographic differences between Ge and Si pyroxenes have been examined. The structure of C2/c Ca rich Ge clinopyroxenes is very close to the low pressure C2/c structural configuration found in Ca-rich Si-pyroxenes. The shear of the unit cell is very similar, and the difference between a Ge end member and the corresponding Si-rich one is less than 1°. Instead, a remarkable difference exists between Ca-poor Si and Ge clinopyroxenes. First, Ca-poor Ge pyroxenes do not display a P21/c symmetry, but retain the C2/c symmetry; second, the observed C2/c structure shows, at room pressure, the configuration with highly kinked tetrahedral chains characteristic of the high pressure C2/c symmetry of Si Ca-poor pyroxenes. In orthopyroxenes, with Pbca symmetry, Ge-pyroxenes have volume larger than Si-pyroxenes. Samples along the system CaCoGe2O6 - CoCoGe2O6 have been synthesized at three different temperatures: 1050 °C, 1200 °C and 1250 °C. The aim of these solid state syntheses was to obtain a solid solution at ambient pressure, since the analogues Si-system needs high pressure. Unfortunately, very limited solution occurs because the structure forms of the two end member (high temperature for CaCoGe2O6 and high pressure CoCoGe2O6) are incompatible. The phase diagram of this system has been sketched and compared to that of Si. The cobalt end member (CoCoGe2O6) is stable at ambient pressure in two symmetries: at 1050 °C C2/c and 1200 °C Pbca. The impurity phase formed during these experiments is cobalt spinel. Raman spectroscopy has been used to investigate the vibrational properties of Ca-pyroxenes CaCoGe2O6, CaMgGe2O6, CaMgSi2O6 and CaCoSi2O6. A comparison between silicate and germanate pyroxenes shows significant changes in peak positions of the corresponding modes caused mainly by the difference of the Ge-Si atomic weight along with the distortion and compression of the coordination polyhedra. Red shift in Raman spectra of germanates has been calculated by a rough scale factor calculated by a simple harmonic oscillator model, considering the different bond lengths for 4-coordinated Si ~ 1.60- 1.65 Å vs Ge–O distance ~1.70 - 1.80 Å. The Raman spectra of CaMgGe2O6 and CaCoGe2O6 have been classified, in analogy with silicate (Wang et al., 2001) counterparts, in different ranges: - R1 (880-640 cm-1): strong T-O stretching modes of Ge and non-bridging O1 and O2 atoms within the GeO4 tetrahedron; - R2 (640-480 cm-1): stretching/bending modes of Ge-Obr-Ge bonds (chain stretching and chain bending); - R4 (480-360 cm-1): O-Ge-O vibrations; - R3 (360-240 cm-1): motions of the cations in M2 and M1 sites correlated with tetrahedral chain motion and tilting tetrahedra; - R5 (below 240 cm-1): lattice modes. The largest shift with respect to CaMgSi2O6 - CaCoSi2O6 is shown by the T-O stretching and chain modes. High-pressure Raman spectroscopy (up to about 8 GPa) on the same samples of Ca-pyroxenes using an ETH-type diamond anvil cell shows no phase transition within the P-ranges investigated, as all the peak positions vary linearly as a function of pressure. Our data confirm previous experimental findings on Si-diopside (Chopelas and Serghiou, 2000). In the investigated samples, all the Raman peaks shift upon compression, but the major changes in wavenumber with pressure are attributed to the chain bending (Ge-Obr-Ge bonds) and tetrahedra stretching modes (Ge-Onbr). Upon compression, the kinking angle, the bond lengths and T-T distances between tetrahedra decrease and consequently the wavenumber of the bending chain mode and tetrahedra stretching mode increases. Ge-pyroxenes show the higher P-induced peak-position shifts, being more compressible than corresponding silicates. The vibrational properties of CaM2+Ge2O6 (M2+ =Mg, Mn, Fe, Co, Ni, Zn) are reported for the first time. The wavenumber of Ge-Obr-Ge bending modes decreases linearly with increasing ionic radius of the M1 cation. No simple correlation has been found with M1 atomic mass or size or crystallographic parameters for the peak at ~850 cm-1 and in the low wavenumber regions. The magnetic properties of the system CaCoSi2O6 - CoCoSi2O6 have been investigated by magnetometry. The join is always characterized by 1 a.p.f.u. of cobalt in M1 site and this causes a pure collinear antiferromagnetic behaviour of the intra-chain superexchange interaction involving Co ions detected in all the measurements, while the magnetic order developed by the cobalt ions in M2 site (intra-chain) is affected by weak ferromagnetism, due to the non-collinearity of their antiferromagnetic interaction. In magnetically ordered systems, this non-collinearity effect promotes a spin canting of anti-parallel aligned magnetic moments and thus is a source of weak ferromagnetic behaviour in an antiferromagnetic. The weak ferromagnetism can be observed only for the samples with Co content higher than 0.5 a.p.f.u. in M2, when the concentration is sufficiently high to create a long range order along the M2 chain which is magnetically independent of M1 chain. The ferromagnetism was detected both in the M(T) at 10 Oe and M(H).

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The literature relating to the drying characteristics of pure liquid drops and particulate slurry drops has been reviewed. The experimental investigation was, therefore, divided into three parts: Pure water drops, Aqueous sodium sulphate decahydrate drops, and, Slurry drops from nine detergent formulations. The value of the constant,'Ψ, reported by Ranz and Marshall, was found to be temperature dependent. In the temperature range o 26.5≤T≤118.5°C,Ψ , for pure water drops, varied between 0.38 and 0.47. A revised correlation of the mass transfer coefficients is therefore proposed.  A mathematical model for estimating the variation of crust thickness, for aqueous sodium sulphate drops, with time is proposed: β = R _ {R3 - ( 1.5G/πCo ) ( ΔHD - ΔHU) Δ} 1/3 Experimental crust thickness evaluated from stereoscan micrographs showed good agreement with theoretical prediction. It has been shown that drying characteristics of detergent drops can be evaluated from the porosity:thickness ratio, {ε/\β}. Formulations having large {ε/β I-ratios dry better than those with smaller values. The agreement between the experimental and theoretical mass transfer coefficients shows, in addition to the above correlation, that the overall mass transfer coefficient can be predicted from the expression1/K = 1/K + β/DMε 1.5 The crust is the controlling resistance to transfer in particulate slurry drops. For aqueous sodium sulphate drops, the crust provides 64.2% of the total resistance while for detergents with thicker, but less porous crusts, the value is 97.5%.