Direct Observation of Orbital Ordering in Layered Manganites

Soft X-ray resonant diffraction is a new technique and there exist several examples of large resonant enhancements of charge and magnetic scattering that can be obtained at the L-edges of 3d transition metal oxides. Here we have employed resonant soft X-ray scattering at the manganese L edges which provide a direct measurement of the orbital ordering. We have studied the layered manganite La_0.5Sr_1.5MnO₄ that displays charge, spin, and orbital ordering. Energy scans at constant wavevector show that there are two separate contributions to the observed scattering, direct Goodenough orbital ordering and strong cooperative Jahn–Teller distortions of the Mn³⁺ ions. Finally we will show how that the charge, spin and orbital degrees of freedom are strongly correlated in these materials.     

Atomic force microscopy study of the antimicrobial activity of aqueous garlic versus ampicillin against Escherichia coli and Staphylococcus aureus

BACKGROUND: In this study the effects of ampicillin and aqueous garlic extract on Escherichia coli (ATCC 9637) and Staphylococcus aureus (ATCC 25923) were compared. Atomic force microscopy (AFM) was used to study the possible mechanisms of membrane disruption. RESULTS: Ampicillin disrupted the cell membrane of E. coli, inducing pores and cell leakage. Aqueous garlic extract also induced leakage from the cell membrane in E. coli, but no pores were observed. The trend in Young's modulus for E. coli was E_native ≈ E_age > E_amp. In contrast, S. aureus incubated with low ampicillin (≤50µg mL^?1) and garlic (≤50 mg mL^?1) concentrations showed no significant changes in surface morphology compared with the untreated bacterium. The trend in Young's modulus for S. aureus was E_native ≈ E_age ≈ E_amp. CONCLUSION: The trend E_native ≈ E_age for E. coli and S. aureus supports the hypothesis that the compounds in garlic show intracellular activity. This proof‐of‐concept study of the aqueous crude isolate of garlic points to the feasibility of further AFM investigations to compare the antimicrobial properties of various pure thiosulfinate isolates found in garlic. Copyright © 2009 Society of Chemical Industry     

The preparation and some mechanical properties of high-purity vanadium

Electron beam melting of vanadium at total dynamic pressures of less than 10^?9 has been shown to reduce the oxygen content. Internal friction analyses and chemical analyses show good agreement. The purification is attributed to the metallic vapor envelope around the molten zone which may have the effect of reducing the partial pressure of oxygen below 10^?13 adjacent to the molten metal and also to the vaporization of VO molecules from the surface of the molten zone. Three stages of work hardening have been shown to exist in vanadium. However, a small interstitial concentration is required to observe stage II. Optical microscope examination reveals that secondary slip lines appear as stage II proceeds. The maximum rate of work hardening of 14 kg per sq mm is in good agreement with the rate of work hardening observed in other bcc metals.     

Visualization of hypersurfaces and multivariable (objective) functions by partial global optimization

Hypersurfaces of the type z=F(x₁,...,x_n), where F are single-valued functions of n real variables, cannot be visualized directly due to our inability to perceive dimensions higher than three. However, by projecting them down to two or three dimensions many of their properties can be revealed. In this paper a method to generate such projections is proposed, requiring successive global minimizations and maximizations of the function with respect to n-1 or n-2 variables. A number of examples are given to show the usefulness of the method, particularly for optimization problems where there is a direct interest in the minimum or maximum domains of objective functions.     

Remarks on standard fibre-optic LANs

This paper explains the importance of standard fibre-optic LANs, and gives an overview of the state of development of the main emerging fibre-optic LAN standards. Fibre-optic enhancements to 802·3, 802·4 and 802·5 are discussed, as well as FDDI and FDDI-2. A brief mention is made of 802·6 and SONET, which are not LANs but are relevant to the discussion. The need for a rational cabling infrastructure is mentioned, as is the need for conformance tests. Some of the practical reasons why it makes sense to have fibre available at the end stations are discussed.     

Solid-Fluid Phase Coexistence of Hard Heteronuclear Dumbbells via Cell Theory and Monte Carlo Simulation

We study the solid-fluid equilibria of hard heteronuclear dumbbells using cell theory and isobaric ensemble Monte Carlo simulations. Calculations for six cases of L* (bond length) and σ* (sphere diameter ratio) near the homonuclear limit are discussed with two base-centered monoclinic orientationally-ordered crystal structures which have been considered. The two crystal structures exhibit nearly identical properties at freezing within the accuracy of the calculations for the cases we present. The reduced pressure at coexistence increases with decreasing σ*.     

A review of Takayasu's arteritis in children in Gauteng, South Africa

We have reviewed 31 patients with Takayasu's arteritis followed at two pediatric nephrology units in Gauteng, South Africa over a 15-year period. There were 25 black patients, 4 white, and 2 of mixed race. The mean age at diagnosis was 8.42+/-3.59 (range 2.4-14.5, median 8) years. The most common presenting sign was hypertension, followed by cardiac failure, bruits, and absent pulses. The Mantoux test was strongly positive in 27 patients (90%, control population 5%). Markers of activity included a raised erythrocyte sedimentation rate (23 patients) or Gallium single photon emission tomography (positive in 12 of 16 patients). Angiography revealed type II (abdominal aorta) and III (arch plus abdominal aorta) lesions to be most common (11 in each group). All patients received antituberculous therapy and most low-dose aspirin for its antithromboxane effect. Corticosteroids and further immunosuppression were used to control disease activity. We added total lymphoid irradiation (TLI) or cyclophosphamide. Twenty-six patients in all received further immunosuppression, with 13 patients in each group. Results were similar in the two groups, with similar pre- and posttherapy systolic blood pressures and creatinine clearances. Two patients in each group relapsed, 3 died in the TLI group and 2 in the cyclophosphamide group. Surgical intervention, usually in the quiescent phase, consisted mainly of renal autotransplantation. Because of the problems with TLI and 2 patients with papillary carcinoma of the thyroid with long-term follow-up, we no longer use TLI. We have shown that with active medical and surgical intervention the aggressive course of this disease in children can be modified.     

Low pressure gas scattering of electron-beam- evaporated MCrAlY alloys

Multi-element overlay coatings applied by electron beam physical vapor deposition techniques have been the subject of intensive research and development programs for many years. The basic line-of-sight nature of the process may present a serious limitation to wider and possible future usage. The results of a program to investigate low pressure gas scattering phenomena in multi-element coatings are presented. Coating thickness and chemical composition uniformity, surface texture and scattering power are discussed.