Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine and naphthalene

Anisotropic displacement parameters (ADPs) are commonly used in crystallography, chemistry and related fields to describe and quantify thermal motion of atoms. Within the very recent years, these ADPs have become predictable by lattice dynamics in combination with first-principles theory. Here, we study four very different molecular crystals, namely urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene, by first-principles theory to assess the quality of ADPs calculated in the quasi-harmonic approximation. In addition, we predict both thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with experimental data. Very reliable ADPs are calculated within the quasi-harmonic approximation for all four cases up to at least 200 K, and they turn out to be in better agreement with experiment than the harmonic ones. In one particular case, ADPs can even reliably be predicted up to room temperature. Our results also hint at the importance of normal-mode anharmonicity in the calculation of ADPs

Cold-rolled austenitic stainless steel: materials properties and structural performance

The cold reduction in thickness of austenitic stainless steel sheet brings about the following significant characteristics of material properties: 1) higher strength with an increasing amount of cold working, 2) more pronounced anisotropic material properties with increasing cold working, 3) stress strain relations different in tension and compression and depending on directions, and 4) nonlinear stress strain curves with relatively low elastic limits, especially in longitudinal compression. In addition, local buckling is encountered in thin walled structural members. These are the problems associated with the structural design of stainless steel members. The purpose of this investigation is to develop the basic necessary information for design methods for light gage cold formed structural elements and members made of cold rolled austenitic stainless steel. A detailed investigation of material properties of cold worked stainless steel is made. A statistical approach is introduced to study the variation of yield strength due to cold working so that lower bound values may be established. An affinity approach is introduced to obtain the shear properties from normal stress behavior. Design mechanical properties for tempered Type 301 are obtained. In order to predict the member behavior, a study of element behavior is essential. The buckling and post buckling behavior of stiffened and unstiffened elements as a part of the structural member is investigated. The nonlinear and anisotropic material properties are considered in the approximate analyses. Bleich\u27s two-modulus concept of inelastic buckling and Von Karman\u27s effective width concept of post buckling strength were used for predicting the element behavior. Based on the element behavior, the response of structural members may be predicted in the post buckling domain. A numerical analysis of the inelastic flexural behavior of thin-walled cold formed members with considerations of the unique material properties is made by using a digital computer. The extensive treatment of flexural members is necessary because of its vital importance in light gage steel applications. Simplified methods are also recommended for design purposes. The theoretical predictions agree quite satisfactorily with experimental results. Design procedures with considerations of strength, local distortion, and deflection are recommended for structural elements and members

Flexibly Connected Thin-walled Space Frame Stability

The elastic stability of a cubic space frame composed of cold-formed steel members is studied for various bending and warping rigidities. A finite element technique is used to perform a parametric study of the elastic stability response of the flexibly connected frame. The results are compared with previously published observations for hot-rolled steel sections. The criterion used for deciding the significance of warping for hot-rolled sections is not found to be applicable to cold-formed sections

Rapidly variable Fe Kα\alpha line in NGC 4051

We present a detailed analysis on the variability of the Fe K emission line in NGC 4051 using ASCA data. Through simple Gaussian line fits, we find not only obvious Fe K line variability with no significant difference in the X-ray continuum flux between two ASCA observations which were separated by $\sim$ 440 days, but also rapid variability of Fe K line on time scales $\sim 10^4$ s within the second observation. During the second observation, the line is strong (EW = 733$^{+206}_{-219}$ eV) and broad ($\sigma = 0.96^{+0.49}_{-0.35}$ keV) when the source is brightest, and become weaker (EW = 165$^{+87}_{-86}$ eV) and narrower ($\sigma<0.09$ keV) whilst the source is weakest. The equivalent width of Fe K line correlates positively with the continuum flux, which shows an opposite trend with another Seyfert 1 galaxy MCG --6-30-15.Comment: 12 pages with 5 figures, to appear in ApJ Vol. 516, L6

Comparative Study of Livelihoods and Food Security Status of Sugarcane Out growers and Non-Cane Growers, Magobbo Scheme, Zambia

In recent times there is a surge in the number of large-scale agricultural based investments. The most common form of large-scale land based investment in Zambia is the out grower scheme. This study is a comparative study of the livelihoods pathways and food security status of out growers in the Magobbo Out grower scheme, Zambia and non cane out growers surrounding the out grower scheme. The livelihoods of the cane growers are slightly better than that of the non-cane growers. The cane out- growers have access to better water facilities; electricity and more income earnings though they have more debts compared to the non-cane growers. On the other hand the non-cane growers were in a survivalist livelihood mode, they were struggling to make ends meet and they straddled subsistence farming and wild fruit selling. In terms of food security at 6.00 Household Dietary Diversity (HDD) index, the food security of cane growers’ was higher standing at 74.3 percent than non-cane growers at 46.9 percent. The study draws from a mixed method approach. The qualitative method was used to explore the livelihoods of the two groups. Quantitative techniques such as t test were done to assess the food security and insecurity of the two groups. A total of 151 households (HH) (70 cane-growers and 81 HH of non-cane growers) participated in this study. Keywords: Sugar cane Outgrower; Non- cane Outgrower; livelihoods; food security; Zambia