Fitness Considerations for Contemporary Composite Materials: (Who’s Afraid of the Composite Micro-Crack?)

Avoiding the catastrophic failure of a large structure demands the material’s microstructure be designed in such as a way as to render any crack present innocuous thereby raising the integrity of that structure. Structural integrity of a composite material embraces contributions from: materials science and engineering; processing science; design and fabrication technology. It combines a number of interacting factors: the criticality of the application; the accessibility for and ability to inspect vital parts and components; the intended use including load spectrum and time; the consequences of impact, fatigue, temperature and hostile environment; the nature of inherent flaws; the constituent properties of the material system utilized; and it takes into account human factors.     

A Computational Model for Masked Negative Films

The construction of a computational model representing a masked negative film is described. Model negative tripacks are then used in the context of a complete negative-positive system to demonstrate the changes in colour reproduction which result from increasing the degree of masking of the magenta dye.     

The Process of Activity and the Built Environment

Summary of some of the topics covered by the author under the ACSA-AMAX Research Fellowship, which he won in 1967.     

The eye of the beholder

This article falls into four broad sections.

1. A background to the physical, political, social and cultural attributes of Saudi Arabia.

2. Problems encountered by designers, such as communications, contractors, plant and construction materials, irrigation water.

3. An attempt to establish some design principles, particularly pertinent to working in an arid Islamic environment.

4. Concludes with some recent projects carried out in the Kingdom, which follow some of these principles.

     

Role of Tyrosine Kinase Syk in Thrombus Stabilisation at High Shear

Understanding the pathways involved in the formation and stability of the core and shell regions of a platelet-rich arterial thrombus may result in new ways to treat arterial thrombosis. The distinguishing feature between these two regions is the absence of fibrin in the shell which indicates that in vitro flow-based assays over thrombogenic surfaces, in the absence of coagulation, can be used to resemble this region. In this study, we have investigated the contribution of Syk tyrosine kinase in the stability of platelet aggregates (or thrombi) formed on collagen or atherosclerotic plaque homogenate at arterial shear (1000 s⁻¹). We show that post-perfusion of the Syk inhibitor PRT-060318 over preformed thrombi on both surfaces enhances thrombus breakdown and platelet detachment. The resulting loss of thrombus stability led to a reduction in thrombus contractile score which could be detected as early as 3 min after perfusion of the Syk inhibitor. A similar loss of thrombus stability was observed with ticagrelor and indomethacin, inhibitors of platelet adenosine diphosphate (ADP) receptor and thromboxane A₂ (TxA₂), respectively, and in the presence of the Src inhibitor, dasatinib. In contrast, the Btk inhibitor, ibrutinib, causes only a minor decrease in thrombus contractile score. Weak thrombus breakdown is also seen with the blocking GPVI nanobody, Nb21, which indicates, at best, a minor contribution of collagen to the stability of the platelet aggregate. These results show that Syk regulates thrombus stability in the absence of fibrin in human platelets under flow and provide evidence that this involves pathways additional to activation of GPVI by collagen.     

Multimerization behaviour of single chain Fv variants for the tumour-binding antibody B72.3

A systematic study has been performed on the relationship betweenlinker length, relative orientation of variable domains, multimerizationbehaviour and antigen binding activity for single chain Fvs(scFvs) of the tumour-binding antibody B72.3. Thirteen scFvvariants with linkers comprising up to six repeats of the motifGly-Gly-Gry-Gly-Ser were studied. All these scFvs showed a tendencyto form dimers or higher molecular weight species, and thistendency decreased with increasing linker length. The dimersand higher molecular weight forms may arise from head to tailintermolecular association of V_H and V_L domains. For each linkerlength, scFvs with the organization VL-linker-VH showed greaterbinding activity than those with the organization VH-linker-VL.In fact, for the latter organization only the variant with a30 amino acid linker showed good binding activity, suggestingthat (0 for B72.3 the C-tenninus of VH or the N-tenninus ofVL makes a structural contribution to antigen binding, and (ii)shorter linkers interfere with this contribution. Antigen bindingstudies on scFvs should be interpreted with caution becauseof their tendency to multlmerize. Such multimerization can beminimized by using linkers longer than those in common use     

Defect-Chemical Aspects in the Synthesis of Metallic Conductors La1–xBaxCuO3 (x= 0.0 to 0.5)

Compositions of La_{1- x} Ba _x CuO₃, where x ranges from 0.0 to 0.5, were fired in air, oxygen-enriched air, and oxygen. Studies show that BaO cannot make a solid solution with LaCuO₃ without changing the basic structure. The resulting phases, in all attempts, were the binary compounds La₂CuO₄, La_{1- x} Ba _x CuO_3-δ ( x = 0.2 to 0.5), or their mixtures. All samples showed metallic conductivity. Extra oxygen in the reaction atmosphere appeared to encourage the formation of the LaCuO₃-based phases of La_{1- x} Ba _x CuO_3-δ ( x = 0.2 or 0.5). We provide a defect-chemical and thermodynamical explanation for this observation.     

Wind speed variability across the UK between 1957 and 2011

By using surface data from 57 UK meteorological stations, a national [British Atmospheric Data Centre (BADC)‐57] and regional wind index for the UK has been calculated for the period 1983–2011. For a subset of seven stations, an additional national index (BADC‐7) has been calculated for the period 1957–2011. The indices show an annual variability of 4% over their respective periods, corresponding to a variation in typical wind turbine capacity factor of 7%. These indices are compared with indices calculated from other sources, namely an index generated using a gridded dataset of observed values interpolated across the UK, an index calculated from an area bounding the UK using the ERA‐40 re‐analysis dataset, indices calculated from bilinear interpolation of the ERA‐40 re‐analysis dataset to the 57 and 7 stations and another independent UK wind index. The indices show variation in trends, with all showing some level of decline with the exception of that generated using the ERA‐40 re‐analysis dataset averaged over the UK, which shows a significant increase. The various indices show varying degrees of agreement with correlation coefficients, after trends are removed, ranging between 0.611 and 0.979. The effect of changes in site exposure, instrument bias and measuring height was considered for the BADC‐7 and BADC‐57 indices. The change in instrument measurement height appears to have a significant biasing effect, and it is likely that this along with changes in exposure at urban sites has caused the decline in annual wind speeds observed for some of the indices. There does not appear to be evidence for significant changes in large‐area (mesoscale) surface roughness. The correlation between annual mean wind speeds at the seven surface station sites used to calculate the BADC‐7 index is seen to be quite weak, indicating very localized variations in inter‐annual variability. When regional differences in the index are investigated, it is seen that wind speeds show a very slight decline across the UK in all regions except the south‐east, which shows a slight increase. The greatest decrease is seen in the north‐west. These changes are in the same direction as the tentative predictions given by climate models for future changes in wind speed across the UK, although the uncertainty is large given the large degree of inter‐annual variation. Copyright © 2013 John Wiley & Sons, Ltd.