Mullite formation from ethyl silicate and aluminium chlorides

The formation of mullite via gels prepared from technical ethyl silicate and aluminium chlorides has been studied. Normally, gels prepared specifically with the oxide stoichiometry of mullite (3Al₂O₃·2SiO₂) do not form the mineral mullite on firing to 1200° C in the absence of a mineralizer. However, when the stoichiometric gel is homogeneous (achieved by acidic or neutral catalysts during the gel preparation) firing at 1200° C can lead to an almost quantitative yield of mullite. For a homogeneous gel, the presence of strontium or caesium salts, or an organo-tin compound such as dibutyltin diacetate or dibutyltin oxide during the gel preparation promotes almost quantitative conversion to mullite at about 1000° C. There is a threshold concentration under which conversion to mullite is incomplete, some cristobalite being formed. For the organo-tin compounds, the type of aluminium chloride is unimportant and the way in which water for the hydrolysis step is added is also unimportant. When the gel is non-homogeneous, the product obtained on firing contains cristobalite and-alumina or-alumina, with little mullite, even if strontium or caesium salts, or organ-otin compounds are present. A ceramic bond is formed from alumina and some other refractory grains during firing.     

Imaging of packaging-related problems in electronic components by scanning acoustic microscopy

Low-frequency (50 MHz) scanning acoustic microscopy has been applied to the problem of imaging defects in semiconductor packages. The results have been compared with the more established technique of X-ray shadow imaging. The scanning acoustic microscope has been found to be able to image a greater variety of defects than X-ray shadow imaging, although the acoustic image could often only be fully interpreted after comparison with the corresponding X-ray image. Scanning acoustic microscopy is now proving to be a valuable analysis technique for the detection and characterisation of packaging related problems.     

The geometric relationship between Holland's personality typology and the Vocational Preference Inventory.

Administered Holland's Vocational Preference Inventory to 373 undergraduates. The 11 scales of the inventory were intercorrelated and factor analyzed. 6 common factors were obtained: (a) Conventional Economic, (b) Feminine, Social, (c) Social Desirability, (d) Material World Orientation, (e) Status, and (f) Artistic. The distances between each pair of the 6 personality types in the 6-dimensional space defined by the common factors were computed and compared with Holland's 1971 hexagonal model of the relationships among the 6 types. The placement of the 6 personality types in 6-dimensional space by the factor analysis corresponded closely to Holland's model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation,characterization and uses of mullite grain

The properties were compared of grain formed at low temperature from a homogeneous mullite precursor gel, and grain formed from the manufactured material produced at high temperature by fusion or by sintering. A homogeneous precursor gel with the oxide stoichiometry of mullite was prepared by treating technical ethyl silicate with aluminium chlorohydrate, with or without dibutyltin oxide as hydrolysis/gelation catalyst. The gel was dried and heated for 5 h at 700 ° C to remove organic residues then ground to 8 m nominal size to obtain a mullite precursor grain. Crystallites form even at this moderate temperature. Commercially produced fine mullite grain manufactured by fusion or by high temperature sintering was also ground to a give a grain of 8 m nominal size to provide a comparative standard with well known material. Each of the three grain materials, homogeneous precursor gel, fused mullite and sintered mullite, each ground to 8 m nominal size, representative of the fines fraction of a grain mix to be used in producing refractory shapes, was made into compacts which were sintered, and, when cold, tested for compressive and bend strength. Materials of this size were chosen for comparison because of their significance in applications where properties at temperature are important. The precursor gel compacts were 95% crystalline mullite and reached 86% of theoretical density. At 1500 ° C, heated in a 90 deg min^–1 schedule, they had strength comparable to sintered mullite; both materials were much stronger than fused mullite. The results show that sintering procedure has a profound effect on strength, and indicated that in the absence of binder, fused mullite is less reactive than sintered mullite. Some properties of refractory shapes and bricks made from the sintered or fused mullite grain are discussed and some uses in refractory shapes are considered.     

Tensile Structure Design An Engineer's Perspective

Here, David Wakefield, the founder of Tensys, an engineering consultancy that specialises in lightweight fabric structure analysis, describes the leading principles that underlie tensile structure design. He explains not only the application of materials and the importance of detailed stress analysis, but also where future developments might lie in this field. Copyright © 2006 John Wiley & Sons, Ltd.     

Modelling post-mortem tenderisation-I: Texture of electrically stimulated and non-stimulated beef

Texture in electrically stimulated and non-stimulated beef M Pectoralis profundus, stored under a range of temperatures from 0 to 30°C, while avoiding muscle shortening, was measured from 1 to 21 days after stunning. The pre-rigor temperature (from 0 to 30°C), maintained until the pH had fallen to 6·4 and then held at 15°C, had no effect on the toughness nor on the rate of tenderisation after rigor. Modelling toughness prior to 24 h suggested that toughness of all muscles could be rationalised and that first-order tenderisation began when the muscles reached pH 6·1 when the toughness of all the muscles was projected to be 12·5 kg. After pH 6·1, the rate of tenderisation at 30°C was 10-fold higher than at 1°C and was not affected by variations in pH from 6·1 to 5·5. At the higher temperatures, the ultimate toughness of aged meat was slightly higher than at the lower temperatures.     

Unit-based acute confusion resource nurse: an educational program to train staff nurses

Despite the high prevalence of acute confusion among elders and the importance of its early detection, there are few reports of systematic efforts to increase staff competence. This article describes the development and evaluation of an 8-hour educational program designed to prepare staff nurses to perform in a new role, the unit-based acute confusion Resource Nurse (ACRN). Pre- and posttest scores were obtained for the 80 registered nurses who participated in the program. Paired t tests showed that knowledge and confidence significantly increased for participants as a result of their participation in the educational program. This program can serve as an effective model for geriatric staff education.     

Ultrasound echogenicity in experimental venous thrombosis

This study characterizes the echogenicity of experimentally induced venous thrombosis. Venous duplex imaging (Diasonics Spectra) was performed of the rat (n 12) and primate (n 3) inferior vena cava (IVC). Thrombosis was induced by IVC ligation at the level of the renal veins (rat, baboon) or balloon occlusion (baboon) of the IVC at the renal vein and iliac vein bifurcation level. Sham-treated rats served as controls. B-mode images were stored for off-line computer analysis. Fixed depth gain control curves allowed for measuring gain-corrected echogenicity units over the IVC in both a longitudinal and transverse orientation. In rat studies, thrombus was removed at time of euthanasia and dissolved, allowing for fibrin monomer determination using a chromogenic assay. Echogenicity values generally increased over time in both rat and primate studies. Significant differences between ligated and sham-treated rats were noted at each time point measured (6 h, 2 days, and 6 days after IVC ligation) and fibrin monomer values correlated (p < 0.05) with echogenicity units. In primate studies, echogenicity values significantly were different from baseline values at all time points measured (6 h, 2 days, 6 days, and 13 days after thrombus induction). Duplex ultrasound can be used to quantitate thrombus echogenicity, which correlates to fibrin content. Such measurement may potentially allow for improved thrombus age determination and the noninvasive quantitation of thrombus progression/resolution.     

The DSM's theory-neutral nosology is scientifically progressive: Response to Follette and Houts (1996).

W. C. Follette and A. C. Houts (1996) argued on philosophy-of-science grounds that the Diagnostic and Statistical Manual of Mental Disorders (DSM) is scientifically unprogressive and should be replaced by competing theory-laden manuals. The author responds to their various arguments as follows: (a) The ways things can go wrong with the mind are inherently diverse, so failure to reduce the DSM's categories to 1 parsimonious theory is not necessarily scientifically unprogressive; (b) it is empirically untrue that growth in the number of a taxonomy's categories is inconsistent with scientific progress; (c) progress in theoretically fragmented fields requires shared theory-neutral categories, not theory-laden definitions of basic concepts; (d) at present in the mental health field, theoretical integration is scientifically more progressive than competition, and integration is promoted by the DSM's theory-neutral nosology; and (e) FoIlette and Houts's proposed behaviorist alternative to the DSM is incoherent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)