Hypervelocity impact damage prediction in composites: Part II—experimental investigations and simulations

The extension of damage in composites during hypervelocity impact (HVI) of space debris is controlled by failure thresholds and subsequent energy consumption during damage growth. Characterisation and modelling of the material under partially and fully damaged states is essential for the prediction of HVI effects on fibre-composite structures. Improved experimental and numerical analysis techniques have been developed and are summarised in an accompanying paper. The present paper deals with the establishment of two precise damage experiments under HVI conditions as a validation basis for numerical simulations: The first type consists of space debris impact configurations optimised for damage evaluation and the second experiments reproduce HVI strain rates and compressions in plate impact. Coupling of damage analysis techniques (visual, ultrasonic, residual strength) to quantify different aspects of failure has been achieved. Numerical simulations using the commercial hydrocode AUTODYN in mesh-based and SPH formulations are presented using the material model and data described in the accompanying paper.     

Radio frequency electromagnetic fields in large conducting enclosures: effects of apertures and human bodies on propagation and field-statistics

Radio frequency propagation in an electrically large resonant chamber (a screened room) was simulated by two models: a statistical combination of multiple resonant modes and a computational electromagnetic simulation [the transmission line matrix (TLM) method]. The purpose of this work was to investigate the effects of passengers and windows on electromagnetic fields (EMF) in aircraft and other vehicles. Comparison of the multimode models with measurements made in a screened room showed that as the electromagnetic losses increased, the transmission between two internal antennas was reduced, and there were fewer turning points in its frequency response. The autocorrelation of this frequency response provided a useful estimate of the composite Q-factor of the resonances and showed that the Q of the chamber was reduced from a value of the order of 10 000 when emptied to 1000 when windows were added and when filled with people to 100. The TLM simulation provided further useful information about the statistical variation of electric field strength with position.     

Novel,Robust, and Versatile Bijels of Nitromethane,Ethanediol, and Colloidal Silica: Capsules,Sub‐Ten‐Micrometer Domains,and Mechanical Properties

Bicontinuous, interfacially jammed emulsion gels (bijels) are a class of soft solid materials in which interpenetrating domains of two immiscible fluids are stabilized by an interfacial colloidal monolayer. Such structures form through the arrest of the spinodal decomposition of an initially single‐phase liquid mixture containing a colloidal suspension. With the use of hexalmethyldisilazane, the wetting character of silica colloids, ranging in size and dye content, can be modified for fabricating a novel bijel system comprising the binary liquid ethanediol–nitromethane. Unlike the preceding water‐lutidine based system, this bijel is stable at room temperature and its fabrication and resultant manipulation are comparatively straightforward. The new system has facilitated three advancements: firstly, we use sub 100 nm silica particles to stabilize the first bijel made from low molecular weight liquids that has domains smaller than ten micrometers. Secondly, our new and robust bijel permits qualitative rheological work which reveals the bijel to be significantly elastic and self healing whilst its domains are able to break, reform and locally rearrange. Thirdly, we encapsulate the ethanediol–nitromethane bijel in Pickering drops to form novel particle‐stabilized bicontinuous multiple emulsions that we christen bijel capsules. These emulsions are stimuli responsive – they liberate their contained materials in response to changes in temperature and solvency, and hence they show potential for controlled release applications.     

Digital geological mapping with tablet PC and PDA: A comparison

Both the hardware and software available for digital geological mapping (DGM) have advanced considerably in recent years. Mobile computers have become cheaper, lighter, faster and more power efficient. Global Positioning Systems (GPS) have become cheaper, smaller and more accurate, and software specifically designed for geological mapping has become available. These advances have now reached a stage where it is effective to replace traditional paper-based mapping techniques with those employing DGM methodologies. This paper attempts to assess and evaluate two currently available DGM systems for geological outcrop mapping: one based on a Personal Digital Assistant (PDA) running ESRI “ArcPad”, and the second based on a Tablet PC running “Map IT” software. Evaluation was based on field assessment during mapping of a well-exposed coastal section of deformed Carboniferous and Permian rocks at N. Tynemouth in NE England. Prior to the field assessment, several key criteria were identified as essential attributes of an effective DGM system. These criteria were used as the basis for the assessment and evaluation process. Our findings suggest that the main concerns presented by sceptics opposed to DGM have largely been resolved.In general, DGM systems using a Tablet PC were found to be most suitable for a wide range of geological data collection tasks, including detailed outcrop mapping. In contrast, systems based on a PDA, due to small screen and limited processing power, were best suited for more basic mapping and simple data collection tasks. In addition, PDA-based systems can be particularly advantageous for mapping projects in remote regions, in situations where there is a limited power supply or where total weight of equipment is an important consideration.     

Thymic overexpression of CD40 ligand disrupts normal thymic epithelial organization

We characterized the distribution of CD40 and CD40 ligand (CD40-L) in the adult and developing murine thymus. Before birth, CD40 was almost exclusively localized to scattered foci of medullary cells. By birth there was a dramatic upregulation of CD40 expression by cortical epithelial cells, which was accompanied by a consolidation of medullary epithelial foci. CD40-L+ thymocytes displayed a medullary location. Analysis of mice deficient in CD40-L expression indicated that CD40-L/CD40 interactions were not required for development of the medullary compartment. Overexpression of CD40-L targeted to thymocytes altered thymic architecture, as reflected by a dramatic loss of cortical epithelial cells, expansion of the medullary compartment, and extensive infiltration of the capsule with a mixture of CD3+ cells, B-cells, and macrophages/dendritic cells. Reconstitution of lethally irradiated normal mice with lck CD40-L bone marrow cells also resulted in loss of cortical epithelium and expansion of the medullary compartment. Disruption of the normal pattern of thymic architecture and epithelial differentiation as a consequence of increased intrathymic levels of CD40-L expression points to a role for CD40-L/CD40 interactions in the normal pattern of epithelial compartmentalization/differentiation within the thymic environment.     

The significance of endothelial injury in the pathogenesis of coronary heart disease

In this study, the number of circulating endothelial cells (CEC) was counted and used as an indicator of the injury of vascular endothelial cells (VEC) in 27 cases with coronary heart disease (CHD), in vivo, CECs were identified with fluorescein-labeled anti-human antibody to factor VIII related antigen. The contents of MDA representing lipid peroxides were also measured in these cases. Meanwhile the number of CEC in normal people was counted as control and compared with that in patients before and after therapy. The results were as follows: The number of CEC and content of MDA in the patients were higher than that in normal people and these two induces were significantly correlated (r = 0.802). The CEC number reflects the severity of CHD. The present investigation suggests that VEC injury induced by the lipid peroxide may play an important role in the pathogenesis of the CHD and CEC counting can be used as a reference for judging the severity and the prognosis of the CHD.     

Heterogenous inhibition of platelet aggregation by monoclonal antibodies binding to multiple sites on GPIIIa

Six monoclonal IgG1-k antibodies (LK2, LK3r, LK4-55, LK5, LK6-55, LK7r) were raised against platelet membrane GPIIIa in order to study the structure-function relationship of this molecule. Antibodies were selected on their ability to react with GPIIIa by ELISA on adherent platelets, by immunoblot on platelet lysates and by fluorescence flow cytometry on intact platelets. Fluorescence reactivity varied from 3- to 202-fold greater than isotype control fluorescence. Two MoAbs reacted on immunoblot under reduced conditions (LK7r and LK3r). Two reacted with a 55 kD chymotrypsin/subtilisin digest of GPIIIa which is likely to exclude amino acids 121-348 (LK4-55 and LK6-55). Four of the MoAbs (LK5, LK3r, LK2 and LK4-55) inhibited tyrosine phosphorylation of one to four distinct bands on immunoblot. LK4-55 reacted with an N-terminal 66 amino acid fusion protein of GPIIIa near the PLA epitope (Leu 33). LK7r reacted with a 212-222 peptide reported to be an RGD fibrinogen binding site. LK2 reacted near a disintegrin-RGD binding site. Except for LK5, all inhibited ADP, collagen and thrombin-induced platelet aggregation in a heterogeneous fashion. Percentage inhibition of 125I-fibrinogen binding to platelets varied from 18% to 98%. No correlation was noted between inhibition of fibrinogen binding, location of MoAb binding on GPIIIa, reactivity of MoAb binding with GPIIIa, inhibition of thrombin-induced tyrosine phosphorylation or inhibition of platelet aggregation induced by ADP, collagen or thrombin. Thus MoAbs, binding to platelet GPIIIa at different sites, inhibit platelet aggregation in a heterogeneous manner.     

Textiles,fire and test standards—a polemic

Textiles usually form the exterior surface of an item which they cover. They are usually organic and therefore may be readily burned. Some actively spread flame. Thus, they are vunerable to fire and to controls designed to promote fire safety. This paper is essentially a personal view of the diversity of test methods, standards and controls concerned with textile flammability which have emerged or are emerging internationally. It suggests the need for collaboration in assessing fire hazards rationally, to counter emotive pressures for controls for controls and to promote their harmonization worldwide.