The influence of advanced age on the outcome of assisted reproduction

This study investigates within-subject variations and associations of salivary viscosities and flow rates in a test panel of healthy adults. After several practice sessions, unstimulated and stimulated whole saliva samples were collected 5 times daily (at 0800, 1100, 1400, 1700, and 2000 h) from 30 university students. There was a significant within-subject variation in viscosity and flow rate of unstimulated saliva (P<0.001). Intra-item correlations were significantly different for salivary flow rates (r= 0.82 for unstimulated, r= 0.88 for stimulated, P< 0.001) and viscosity of unstimulated saliva (r= 0.54, P< 0.05), but viscosity of stimulated saliva was different in this respect. Our results indicate that there is a significant within-subject variation in viscosity of unstimulated saliva.     

Mechanism of inhibition of tannic acid and related compounds on the growth of intestinal bacteria

Tannic acid, propyl gallate and methyl gallate, but not gallic acid, were found to be inhibitory to the growth of intestinal bacteria Bacteroides fragilis ATCC 25285, Clostridium clostridiiforme ATCC 25537, C. perfringens ATCC 13124, C. paraputrificum ATCC 25780, Escherichia coli ATCC 25922, Enterobacter cloacae ATCC 13047, Salmonella typhimurium TA98 and S. typhimurium YG1041 at 100-1000 microg/ml in culture broth. Neither Bifidobacterium infantis ATCC 15697 nor Lactobacillus acidophilus ATCC 4356 was inhibited by any of the above compounds up to 500 microg/ml. Tannic acid has a much greater relative binding efficiency to iron than propyl gallate, methyl gallate or gallic acid. The inhibitory effect of tannic acid to the growth of intestinal bacteria may be due to the strong iron binding capacity of tannic acid; whereas the effect of propyl gallate and methyl gallate probably occurs by a different mechanism. The growth of E. coli was restored by the addition of iron to the medium after the precipitate caused by tannic acid was removed. Neither B. infantis nor L. acidophilus require iron for growth. This probably contributes to their resistance to tannic acid. Because tannins are abundant in the human diet, tannins may affect the growth of some intestinal bacteria and thus may have an impact on human health.     

Local mobility within villin 14T probed via heteronuclear relaxation measurements and a reduced spectral density mapping

Villin 14T, a representative domain from the actin severing and bundling protein villin, binds calcium ions and actin monomers. To begin to understand the contributions of mobility to the villin-calcium and villin-actin interactions, relaxation rates for magnetization involving the amide nitrogens and protons have been measured for 15N-labeled villin 14T in solution. Although we have measured the complete set of rates required for a full spectral density map, difficulties in the accurate measurement of relaxation rates for antiphase coherence and two-spin order led us to consider a reduced mapping formalism. From the reduced spectral density map, a model-free analysis, or directly from the measured Nx,y relaxation rates, local variations in mobility along the backbone of villin 14T have been revealed. Fast motions are evident not only at the amino and carboxyl termini but also in the turn between strands beta 4 and beta 5 of the central beta-sheet and in the turn between helix alpha 3 and strand beta 7. Slower motions are suggested for the turn between strands beta 2 and beta 3. Motions on the microsecond to millisecond time scale have been probed directly by examining the dependence of the proton transverse relaxation rate on the spin-locking field strength. Leu11 shows a strong dependence on field strength, implying conformational exchange with a time constant of 125 +/- 69 microseconds. The backbone at the actin-binding interface appears to be rather rigid.     

Environmental antigen-induced IL-13 responses are elevated among subjects with allergic rhinitis, are independent of IL-4, and are inhibited by endogenous IFN-gamma synthesis

Human immediate hypersensitivity diseases represent the most common example of chronic excessive Th2-like activation in developed nations. While IL-13 shares many functional properties with IL-4, the intensity and regulation of environmental Ag-stimulated IL-13 synthesis by allergic vs nonallergic individuals remain ill defined. Here, we examine the intensity of polyclonally and Ag-stimulated IL-13 production by PBMC of 20 subjects with seasonal allergic rhinitis and 20 healthy controls. Polyclonally driven IL-13 responses did not differ significantly (Mann-Whitney U test, p = 0.68). In contrast, the median CD4-dependent IL-13 response among atopics was markedly stronger than nonatopics in Ag-stimulated primary culture (p = 0.0031) and exhibited a strong correlation with IL-5 (r = 0.76, p = 0.0009), but not IL-4 (r = 0.14, p > 0.05), responses. IL-13 production was unaffected by blocking endogenous IL-4 or IL-5 activity or by addition of rIL-4 or rIL-5. In contrast, it was inhibited by low levels of rIFN-gamma and strongly enhanced upon addition of neutralizing anti-IFN-gamma mAb. Collectively, the data are consistent with a negative regulatory role for endogenous IFN-gamma synthesis in controlling the intensity of systemic IL-13 responses evoked in both atopic and nonatopic populations following exposure to common Ags. They also suggest that the elevated levels of IL-4 and IL-5 characteristic of type 2-dominated responses in vivo are without detectable impact on the maintenance of recall Ag-stimulated IL-13 production.     

From ethnographic record to system design

This paper explores the issues involved in moving from ethnographic explorations of work in context to a practical contribution to system design. It does so using the example of an interdisciplinary research project involving sociologists and computer scientists in the domain of air traffic control systems. It forms a pair with another paper (Sommerville et al., 1992) exploring these questions from the perspective of our computer science partners. We characterise ethnography as a research method, and consider the differences between undertaking it for strictly sociological or anthropological purposes by contrast with interdisciplinary and design purposes. We summarise some of our results in ethnographic explications of the work of air traffic controllers, and the sociality which it manifests. We describe the dialogues involved in rendering these observations informative for systems design, and the mutual translations implied in attempting to reconcile sociological with software engineering questions about supporting the work. We conclude by specifying some features of cooperative work which an engineering approach is in danger of overlooking; the ways, and limits, in which ethnographers can form a bridge between users and designers; and some of the conflicts of interest entrained in generating technical change.The research is funded by the UK MRC/SERC/ESRC Cognitive Science/HCI Initiative with the title Social Analysis of Control Systems for HCI Design, grant number SPG 8931598. The computer science partners are Professor Ian Sommerville, Dr Tom Rodden, Dr Pete Sawyer and Mr Richard Bentley. Thanks are due to Val King, Kjeldt Schmidt, Ian Sommerville and Tom Rodden for very helpful comments on earlier drafts of this paper.     

Rheology and Consolidation of Colloidal Alumina-Coated Silicon Nitride Suspensions

In an attempt to improve the colloidal processing of Si₃N₄ ceramics, we studied the rheology and consolidation of colloidal suspensions of Si₃N₄ particles (average particle size 0.7 μm) with small Al₂O₃ particles (average particle size 20 nm). It was found that at pH >7, the viscosity of the mixtures increased and then decreased with an increasing concentration of Al₂O₃. λpotential measurements, optical micrographs, and visible light absorptance measurement suggest that such viscosity behavior is due to clustering of Si₃N₄ particles bridged by the small Al₂O₃ particles. This is also supported by the Derjaquin-Landau-Verwey-Overbeek (DLVO) potential calculations that show the barrier height in the DLVO potential between Al₂O₃ and Si₃N₄ is small. The small barrier height under current experimental conditions stems from the small size of the Al₂O₃ particles. The small barrier height allows the thermal motion of the two kinds of particles to overcome the barrier and attach to each other. The adsorption of small Al₂O₃ particles on Si₃N₄ can occur even when both Al₂O₃ and Si₃N₄ carry the same sign of charges. The adsorption of Al₂O₃ on Si₃N₄ also increases the density of consolidated compacts.     

Chromate leaching from inhibited primers: Part I. Characterisation of leaching

Leaching and characterisation studies have been undertaken on two chromate-inhibited epoxy polyamide primers. Leaching was carried out in 5% (w/v) NaCl solutions at different pH values (1, 3, 5 and 7) and the amount of Cr released into solution was monitored over time. Cr release was initially high, but as the immersion time increased the leaching from the primers slowed. Prior to and after immersion, the primers were characterised by a number of techniques including electron microprobe analysis, X-ray microdiffraction, Raman spectroscopy, and positron annihilation lifetime spectroscopy. The unexposed primers were found to contain the inorganic phases SrCrO₄, BaSO₄ and TiO₂ (anatase or rutile). Upon immersion, water uptake by the primers was observed, together with a decrease in the amount of SrCrO₄ in the primers. These studies provide insights into the mechanism of chromate leaching from inhibited primers.     

Binary and ternary blends of poly(vinyl chloride), hytrel,and a polyurethane

Binary blends of poly(vinyl chloride) and a poly(ether urethane) containing 20 and 40 weight percent, respectively, of poly(vinyl chloride) have been prepared by solution blending from tetrahydrofuran and their degree of mixing investigated using dynamic mechanical analysis. In the polyurethane, transitions were found at ?19°C and ?119°C. The former was attributed to the glass transition and the latter to a Schatzki type of motion of the polyether sequences. This latter transition occurred at a temperature which is higher than the literature value for the low temperature transition in poly(tetrahydrofuran), which is equivalent to the polyether sequence in the polyurethane. This discrepancy is attributed to the influence of neighboring hard segments present because of incomplete segmental phase separation of the polyurethane. For the blends only one very broad transition was observed, indicating that there was substantial mixing of these two polymers. Three ternary blends were prepared, also by solution blending, containing poly(vinyl chloride), Hytrel, and the polyurethane in the ratios 1:1:1, 1:2:1, and 2:1:1, respectively. In the first two blends there was clear evidence of phase separation. It was only in the 2:1:1 blend that an apparently significantly compatible material resulted.     

The estimation of the residual capacity of sealed lead-acid cells using the impedance technique

The problem of estimating the residual usable energy of a lead-acid cell has been intensified by the introduction of fully sealed units. These rely on the recombination of gaseous oxygen produced during overcharge at the positive electrode with the active material at the negative electrode. This introduction has removed the possibility of electrolyte density measurements, third electrode measurements and restricted residual capacity assessments to the two cell terminals. A method for this process is described using a parameter based on a characteristic frequency. The parameter is also a useful measure of cell ageing.Nomenclature R _SOL Ohmic resistance of cell () - Charge-transfer resistance of positive and negative electrodes () - CL Double-layer capacitance of both positive and negative electrodes (F) - Warburg diffusion (S^–1/2) - C _EXT External series capacitor in analogue Fig. 5 (F) - R _EXT External resistor in parallel withC _EXT in the anologue circuit Fig. 5 () - IND Inductor in Fig. 5 representing the geometrical effects of the cell at high frequencies (Henries) - R _IND External resistor in parallel with IND in the analogue circuit Fig. 5 () - Roughness factor allowing for the porosity of both electrodes