Normal vector generation for sampled data using fourier filtering

A three-dimensional surface is a useful graphic representation of a two-dimensional function which has been sampled on a regular grid. Shading the surface to simulate the effects of direct lighting makes visible small changes in the surface orientation, and enhances realism when the data represents a physical surface such as terrain. Shading interpolation calculations and surface patch generation techniques require the specification of a surface normal vector (or related slope information) at each sample point. These normal vectors are usually generated by averaging local data such as the normal vectors of the surfaces of a triangular mesh connecting the points. This paper describes a technique which uses Fourier filtering to generate normal vectors for two-dimensional sampled data. Images and analysis of frequency spectra are included to show how this technique preserves detail which is lost using the averaging method. Performance figures show that this enhancement of detail in the final image can be achieved for only a small increase in computation time.     

Carbon capture and storage: Fundamental thermodynamics and current technology

Carbon capture and storage (CCS) is considered a leading technology for reducing CO₂ emissions from fossil-fuelled electricity generation plants and could permit the continued use of coal and gas whilst meeting greenhouse gas targets. However considerable energy is required for the capture, compression, transport and storage steps involved. In this paper, energy penalty information in the literature is reviewed, and thermodynamically ideal and “real world” energy penalty values are calculated. For a sub-critical pulverized coal (PC) plant, the energy penalty values for 100% capture are 48.6% and 43.5% for liquefied CO₂, and for CO₂ compressed to 11 MPa, respectively. When assumptions for supercritical plants were incorporated, results were in broad agreement with published values arising from process modelling. However, we show that energy use in existing capture operations is considerably greater than indicated by most projections. Full CCS demonstration plants are now required to verify modelled energy penalty values. However, it appears unlikely that CCS will deliver significant CO₂ reductions in a timely fashion. In addition, many uncertainties remain over the permanence of CO₂ storage, either in geological formations, or beneath the ocean. We conclude that further investment in CCS should be seriously questioned by policy makers.     

Identification of microglial signal transduction pathways mediating a neurotoxic response to amyloidogenic fragments of beta-amyloid and prion proteins

Microglial interaction with amyloid fibrils in the brains of Alzheimer's and prion disease patients results in the inflammatory activation of these cells. We observed that primary microglial cultures and the THP-1 monocytic cell line are stimulated by fibrillar beta-amyloid and prion peptides to activate identical tyrosine kinase-dependent inflammatory signal transduction cascades. The tyrosine kinases Lyn and Syk are activated by the fibrillar peptides and initiate a signaling cascade resulting in a transient release of intracellular calcium that results in the activation of classical PKC and the recently described calcium-sensitive tyrosine kinase PYK2. Activation of the MAP kinases ERK1 and ERK2 follows as a subsequent downstream signaling event. We demonstrate that PYK2 is positioned downstream of Lyn, Syk, and PKC. PKC is a necessary intermediate required for ERK activation. Importantly, the signaling response elicited by beta-amyloid and prion fibrils leads to the production of neurotoxic products. We have demonstrated in a tissue culture model that conditioned media from beta-amyloid- and prion-stimulated microglia or from THP-1 monocytes are neurotoxic to mouse cortical neurons. This toxicity can be ameliorated by treating THP-1 cells with specific enzyme inhibitors that target various components of the signal transduction pathway linked to the inflammatory responses.     

System to measure the use of the backrest in sitting-posture office tasks

This paper presents an inexpensive and simple system to measure the way of use of the backrest. The system can be also used in field studies. It is based on a set of electrodes which, attached to the subject's back and the backrest, allows the contact area to be measured. A laboratory test was performed to validate the system. In the test the spontaneous use of the backrest in standard office chairs and tasks was studied. Four different types of backrest use have been detected, and it has been shown that they determine the lumbar curvature and pelvic inclination angles, as well as postural mobility. The comfort levels observed in the four types of backrest use were also different. Consequently, the system can be used as an indicator of back posture and comfort.     

Cartilage degeneration in relation to repetitive pressure: case study of a unilateral hip hemiarthroplasty patient

The mitochondrial, inner-membrane-associated, reversible NADPH-->NAD transhydrogenase of adult Hymenolepis diminuta physiologically couples matrix-localized, NADP-specific "malic" enzyme with NADH-dependent anaerobic electron transport. Employing submitochondrial particles (SMP) as the source of enzyme activity and both spectrophotometric and fluorometric assessments, the present study made evident that in its catalysis of transhydrogenation between NADPH and NAD, the cestode enzyme engages in the concomitant transmembrane translocation of protons. As assessed spectrophotometrically, the catalysis of NADPH-dependent NAD reduction by H. diminuta SMP was stimulated significantly by carbonyl cyanide 3-chlorophenylhydrazone (CCCP), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP), as well as by the protonophoric anthelmintic, niclosamide. In addition, N,N'-dicyclohexylcarbodiimide (DCCD) markedly diminished SMP-catalyzed hydride ion transfer between NADPH and NAD. The catalysis by SMP of concomitant, transhydrogenase-mediated proton translocation was evaluated more directly via fluorometric assays using 8-anilino-1-napthalenesulfonic acid (ANS) as the probe. These latter evaluations revealed a transhydrogenase-dependent enhancement of ANS fluorescence in accord with an intravesicular accumulation of protons. ANS fluorescence was quenched rapidly when the assay system was supplemented with CCCP, FCCP, or niclosamide. Consistent with the helminth transhydrogenase acting as a proton pump, transhydrogenase-mediated enhanced fluorescence also was inhibited by DCCD. Considered collectively, these data indicated, apparently for the first time for any invertebrate system, that the transhydrogenase, in catalyzing the NADPH-->NAD reaction, acts in the translocation of protons from the matrix to the intermembrane space mitochondrial compartment.     

The contribution of platelet-activating factor to allergen-induced eosinophil infiltration and bronchial hyperresponsiveness

Platelet-activating factor (PAF) is an ether-linked phospholipid having a range of biological properties of relevance to our understanding of the pathogenesis of bronchial asthma and related allergic diseases. In particular the ability of PAF to induce eosinophil activation and recruitment has received considerable attention. Since in experimental animals PAF and allergen-induced eosinophil infiltration are dependent upon platelet activation, it is suggested that platelet activation may be an important component of the allergic process. The ability of PAF antagonists to inhibit various aspects of the allergic response has been demonstrated in a number of animal models but not all of them have been extended into man. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Chronic lymphatic leukemia. Peroral cladribine as primary treatment

Ten patients with newly diagnosed B-chronic lymphocytic leukaemia were treated with cladribin orally for five days every four weeks with a median of four series. This is the first reported clinical study where a purine analogue is administered orally. The tumour reducing effect was fast. Eight out of 10 patients responded with a partial or clinical complete remission. Two of these were in molecular biological complete remission. With an observation time of 22 months we have seen no serious side effects so far. A randomized study (including a long term follow up) between chlorambucil, fludarabin and cladribin is needed to clarify the future role of cladribin in B-CLL treatment.