Partial replacement of cement by fly ash in autoclaved products — theory and practice

Nine different fly ashes have been used in a study of autoclaved (216° C) cement-fly ash mixtures containing 50% fly ash (by weight). Paste samples for each fly ash were prepared at water-solid ratios of 0.22 to 0.45 and mechanical property-porosity relations were determined. The autoclaved products were characterized by several techniques. Linear correlations with a composition term, C/(S + A)–kF, were obtained for logarithms of zero-porosity modulus of elasticity and microhardness values. A linear correlation for modulus of elasticity of the porous solid and the composition term, 2 - C/S + A–kF, was also obtained for each water-solid ratio. Correlations for microhardness of the porous solid with a composition term, 2–C/S + A are reported, a different curve for each water-solid ratio. Impregnation of the porous products resulted in increased values for modulus of elasticity and microhardness and provided an alternate means of estimating zero-porosity values of these properties.     

Volume change on first drying of hydrated portland cement with and without admixtures

The effect of admixtures of several types on the volume change characteristics of portland cement pastes is reported. Samples were cut in the form of wafers and dried step by step through several humidities down to 40 per cent; other samples were dried to the d-dried state. Large first drying shrinkages were obtained with extra dosages of calcium lignosulphonate, hydroxy carboxylic acids, and triethanolamine. Below 40 per cent RH all samples showed similar behavior with further drying or rewetting. It is suggested that the effect of admixture is mainly one of degree of dispersion in terms of alignment of sheets and displacement of ends of sheets.     

Interferon alpha and Tat involvement in the immunosuppression of uninfected T cells and C-C chemokine decline in AIDS

HIV type 1 (HIV-1) not only directly kills infected CD4(+) T cells but also induces immunosuppression of uninfected T cells. Two immunosuppressive proteins, interferon alpha (IFNalpha) and extracellular Tat, mediate this process because specific antibodies against these proteins prevent generation of suppressor cells in HIV-1-infected peripheral blood mononuclear cell cultures. Furthermore, the production of C-C chemokines in response to immune cell activation, initially enhanced by IFNalpha and Tat, ultimately is inhibited by these proteins in parallel with their induction of immunosuppression. The clinical corollary is the immunosuppression of uninfected T cells and the decline in C-C chemokine release found at advanced stages of HIV-1 infection paralleling rising levels of IFNalpha and extracellular Tat. We, therefore, suggest that IFNalpha and Tat may be critical targets for anti-AIDS strategies.     

An evaluation of architectures incorporating wavelength divisionmultiplexing for broad-band fiber access

Wavelength division multiplexing (WDM) offers the potential to transport very high bit rates in access systems serving residential and small business customers. We describe the options for WDM access systems, and evaluate them on the basis of an international standard that is emerging for passive optical networks (PONs) that use wavelength-independent power splitting. The greatest impediment to meeting the high-bandwidth potential of WDM for downstream (i.e., from the central office to the home) transmission is the need for a moderately priced multiple-wavelength light source, implementing WDM in the upstream (home to central office) direction presents greater hurdles than in the downstream. The technical aspects of overcoming these hurdles can all be met. The real challenge will be in finding technical solutions that can meet the very stringent cost requirements of access systems. Systems that use WDM in the downstream direction only, while using wavelength-independent power-combining in a PON configuration for upstream, may prove economical before full WDM systems. WDM may also prove valuable if upgrades are needed in the future for power-splitting PON's     

Breaking the silence of factitious disorder

A terminally-ill patient is being cared for at home by relatives who have no medical or nursing experience but who are doing their best and are well supported by the holistic care of the community teams. As death becomes imminent, the relatives find themselves out of their depth, they panic and dial 999. The patient is rushed to Accident & Emergency (A & E) and is possibly dead on arrival or shortly afterwards. It is the relatives who now need nursing care, to help them through this totally unexpected upheaval. Aspects of this scenario are explored in this paper.     

Reduced specificity of autobiographical memory and depression: The role of executive control.

It has been widely established that depressed mood states and clinical depression, as well as a range of other psychiatric disorders, are associated with a relative difficulty in accessing specific autobiographical information in response to emotion-related cue words on an Autobiographical Memory Test (AMT; J. M. G. Williams & K. Broadbent, 1986). In 8 studies the authors examined the extent to which this relationship is a function of impaired executive control associated with these mood states and clinical disorders. Studies 1-4 demonstrated that performance on the AMT is associated with performance on measures of executive control, independent of depressed mood. Furthermore, Study 1 showed that executive control (as measured by verbal fluency) mediated the relationship between both depressed mood and a clinical diagnosis of eating disorder and AMT performance. Using a stratified sample in Study 5, the authors confirmed the positive association between depressed mood and impaired performance on the AMT. Studies 6-8 involved experimental manipulations of the parameters of the AMT designed to further indicate that reduced executive control is to a significant extent driving the relationship between depressed mood and AMT performance. The potential role of executive control in accounting for other aspects of the AMT literature is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Hydrostatic Laser Surface Textured Gas Seal

A theoretical model is developed to study the effect of partial laser surface texturing (LST) on a hydrostatic gas seal. The partial LST provides a mechanism for hydrostatic pressure build up in the sealing dam similar to that of a radial step. The surface texturing parameters are numerically optimized to obtain maximum efficiency in terms of the ratio of load carrying capacity over gas leakage. The performance of the optimum partial LST seal compares favorably with that of a radial step seal.