Transmission electron microscopy characterization of microstructural features of Al-Li-Cu alloys

A transmission electron microscopy (TEM) examination of aluminum-lithium-copper alloys was conducted. The principal purpose is to characterize the nature, size, and distribution of stringer particles which result from the powder metallurgy (P/M) processing of these alloys. Microstructural features associated with the stringer particles are reported that help explain the stress corrosion susceptibility of the powder metallurgy-processed Al-Li-Cu alloys. In addition, matrix precipitation events are documented for a variety of heat treatments and process variations. Hot rolling is observed to significant alter the nature of matrix precipitation, and the observations are correlated with concomitant mechanical property variations

Father's occupational exposure to carcinogenic agents and childhood acute leukemia: a new method to assess exposure (a case-control study)

<p>Abstract</p> <p>Background</p> <p>Medical research has not been able to establish whether a father's occupational exposures are associated with the development of acute leukemia (AL) in their offspring. The studies conducted have weaknesses that have generated a misclassification of such exposure. Occupations and exposures to substances associated with childhood cancer are not very frequently encountered in the general population; thus, the reported risks are both inconsistent and inaccurate. In this study, to assess exposure we used a new method, an exposure index, which took into consideration the industrial branch, specific position, use of protective equipment, substances at work, degree of contact with such substances, and time of exposure. This index allowed us to obtain a grade, which permitted the identification of individuals according to their level of exposure to known or potentially carcinogenic agents that are not necessarily specifically identified as risk factors for leukemia. The aim of this study was to determine the association between a father's occupational exposure to carcinogenic agents and the presence of AL in their offspring.</p> <p>Methods</p> <p>From 1999 to 2000, a case-control study was performed with 193 children who reside in Mexico City and had been diagnosed with AL. The initial sample-size calculation was 150 children per group, assessed with an expected odds ratio (OR) of three and a minimum exposure frequency of 15.8%. These children were matched by age, sex, and institution with 193 pediatric surgical patients at secondary-care hospitals. A questionnaire was used to determine each child's background and the characteristics of the father's occupation(s). In order to determine the level of exposure to carcinogenic agents, a previously validated exposure index (occupational exposure index, OEI) was used. The consistency and validity of the index were assessed by a questionnaire comparison, the sensory recognition of the work area, and an expert's opinion.</p> <p>Results</p> <p>The adjusted ORs and 95% confidence intervals (CI) were 1.69 (0.98, 2.92) during the preconception period; 1.98 (1.13, 3.45) during the index pregnancy; 2.11 (1.17, 3.78) during breastfeeding period; 2.17 (1.28, 3.66) after birth; and 2.06 (1.24, 3.42) for global exposure.</p> <p>Conclusion</p> <p>This is the first study in which an OEI was used to assess a father's occupational exposure to carcinogenic agents as a risk factor for the development of childhood AL in his offspring. From our results, we conclude that children whose fathers have been exposed to a high level of carcinogenic agents seem to have a greater risk of developing acute leukemia. However, confounding factors cannot be disregarded due to an incomplete control for confounding.</p

Nanogold on nanodiamonds – A microscopic study

status: publishe

INFLUENCE OF PHOSPHORUS ON THE STRUCTURE AND THE HYDRODESULFURIZATION AND HYDRODENITROGENATION ACTIVITY OF W/AL2O3 CATALYSTS

A series of W/Al2O3 catalysts containing various amounts of phosphorus (0-6 wt.-% P2O5) were characterized, in the oxide state by X-ray diffraction and temperature-programmed reduction (TPR), and in the sulphide form by high-resolution transmission electron microscopy (HRTEM

Template-free synthesis of CoMoO4 rods and their characterization

The effect of pressure and temperature on the synthesis of cobalt-molybdenum oxides and their characterisation is herein reported. The synthesis was performed under hydrothermal conditions without any template. It was found that the experimental conditions affect the physical properties of the CoMoO4. SEM images demonstrate that the synthesised powder is comprised of rods, and the width of the structures is about 100 nm but the length varies from about 5 μm to less than 1 μm. Low temperature and pressure favour the formation of longer rods. © 2013 Elsevier Ltd. All rights reserved

MIXED IMPREGNATED THIOSALT DECOMPOSITION CATALYSTS CHARACTERIZED BY X-RAY-DIFFRACTION

We used the impregnated thiosalt decomposition method (ITD) to prepare catalysts of molybedenum sulfide promoted with cobalt in atomic ratios (r = Co/(Co + Mo)) ranging from 0.0 to 1.0. Measurements obtained by X-ray diffraction (XRD) show the presence of the MoS2-2H phase in all mixed samples, and segregation of cobalt in two phases: Co9S8, for r greater-than-or-equal-to 0.3, and CoS1.035, for 0.3 less-than-or-equal-to r less-than-or-equal-to 0.5

Synthesis and characterization of NiWO4 crystals

Nickel tungstate (NiWO4) catalyst has been synthesized by reacting ammonium metatungstate and nickel nitrate as a function of temperature from 673 to 1073 K and of 1-h reaction time. It was found that NiWO4 is formed from 823 to 1073 K. The yield of 99% was obtained from 903 K to higher temperatures. The average crystal sizes have been determined by the Scherrer analysis and the surface area was measured by the Brunauer-Emmett-Teller (BET) method. The former increase from 55 to 112 nm, while the second decrease from 16 to 3 m(2) g(-1) in both cases, as the reaction temperature increases from 823 to 1073 K. Elemental composition and morphological structure were studied by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The structural characterization has been performed using X-ray diffraction (XRD). (C) 2001 Elsevier Science B.V. All rights reserved

Hydrodesulfurization activity of MoS2 catalysts modified by chemical exfoliation

The surface area of unsupported MoS2 catalysts prepared by thiosalt decomposition is found to increase after undergoing a treatment known as chemical exfoliation. Rate measurements of dibenzothiophene hydrodesulfurization in a batch reactor show that activity decreases for the chemically modified MoS2 catalysts, along with the hydrogenation/hydrodesulfurization ratios (HYD/HDS). These results indicate that both basal and edge planes of the layered sulfides are rearranged by the exfoliation treatment, but that other processes must also be involved. Reference crystalline MoS2 is also discussed in the work