The glass fibre-polymer interface: II—Work of fracture and shear stresses

Pull-out experiments have been carried out on single production fibres under carefully controlled conditions. Four parameters were determined. The interfacial yield stresses, of about 9–14 MPa, were very much smaller than the shear strengths of the bulk polymers in the case of an epoxy, whether post-cured or not, and a non-post-cured polyester. Values for the work of fracture of the interface varied from 140 to 300 Jm^?2, and again were less than those of the polymer. Interface failure sometimes took place in the epoxy rather than at the fibre surface, whereas with the polyester it always took place at the fibre surface. After interface failure, pull-out was governed by friction, with maximum shear stresses of 7–10 MPa for polyester, and 21–34 MPa for epoxy, the higher values being obtained for the post-cured resins. Average frictional shear stresses were sometimes less than a half of the maximum shear stress, indicating that the fibre Poisson's shrinkage was playing an important role in the pull-out process. A silicone release agent reduced the frictional shear stresses to 2·5 MPa, with both resins.     

The effect of fibre alignment on composite strength: II. The strength of angle-ply laminates

Experiments have been carried out on relatively wide angle-ply laminate samples with very short gauge lengths. These proved to be very much stronger than samples tested in earlier work, and which form the basis for our present design with these materials. It is highly likely that the early results for strength were more indicative of edge effects than true laminate strength. This is confirmed by data from tests on pressurized tubes. A review of the literature on this shows that such tests produced results which can be an order of magnitude higher than the early laminate tests. Thus our design calculations could well be severely underestimating the potential strength of angle-ply laminates. This may be having serious consequences for the aerospace industry, through the use of design criteria for strength which may be too conservative. Single-fibre experiments may pave the way for more realistic estimates of angle-ply laminate strengths. These indicate that a simple one-third power rule can be used to estimate the potential strength. However, this is purely ad hoc at present, and needs to be put on a firmer footing through both theoretical and experimental studies. Furthermore, if this approach is adopted, edge effects will still have to be allowed for, and estimated on the basis of the aspect ratio of the part.     

An ant swarm-inspired energy-aware routing protocol for wireless ad-hoc networks

Primitive routing protocols for ad-hoc networks are “power hungry” and can therefore consume considerable amount of the limited amount of battery power resident in the nodes. Thus, routing in ad-hoc networks is very much energy-constrained. Continuous drainage of energy degrades battery performance as well. If a battery is allowed to intermittently remain in an idle state, it recovers some of its lost charge due to the charge recovery effect, which, in turn, results in prolonged battery life.In this paper, we use the ideas of naturally occurring ants’ foraging behavior (Dorigo and Stuetzle, 2004) [1] and based on those ideas, we design an energy-aware routing protocol, which not only incorporates the effect of power consumption in routing a packet, but also exploits the multi-path transmission properties of ant swarms and, hence, increases the battery life of a node. The efficiency of the protocol with respect to some of the existing ones has been established through simulations. It has been observed that the energy consumed in the network, the energy per packet in the case of EAAR are 60% less compared to MMBCR and the packets lost is only around 12% of what we have in AODV, in mobility scenarios.     

The effect of matrix stresses on fibre pull-out forces

A pull-out test was developed to measure the bond strengths and frictional forces between steel wires, and polycarbonate and epoxy matrices when the matrix was under tensile stress. Some debonding occurred due to the matrix stress. Despite this, the nominal bond strength, in the polycarbonate case, increased with increasing matrix applied stress. When the pull-out force had caused complete debonding, sliding under approximately constant friction coefficient,, occurred. The value of for steel sliding in polycarbonate was 0.6, and for epoxy it was 0.19. The values were reduced to 0.12 and 0.10 respectively when the steel was coated with a fluorocarbon release agent. The normal stresses at the interface, in the absence of any applied stresses, were found to be about 7 MN m^–2 in the polycarbonate, and 3.0 MN m^–2 in the epoxy case. It was observed that the frictional forces due to these residual stresses could be less than one third of those generated by the applied stresses on the matrix. Thus residual stresses are not as important for fibre reinforcement as are matrix Poisson's shrinkage stresses.     

A multi-element thermal imaging system based on an uncooled bolometric array

A thermal imaging system based on a commercial uncooled microbolometric array of 384 × 288 elements has been developed and produced. The temperature and spatial resolutions of the system are <0.08°C and 0.96 mrad, respectively. The system has been designed to monitor the technical state of thermal power industry objects. Owing to the “open architecture” and the modular structure of the hardware and software, the system can be adapted for any thermal diagnostic task.     

THZ531 Induces a State of BRCAness in Multiple Myeloma Cells: Synthetic Lethality with Combination Treatment of THZ 531 with DNA Repair Inhibitors

Multiple myeloma (MM) is a hematological disease marked by abnormal growth of B cells in bone marrow. Inherent chromosomal instability and DNA damage are major hallmarks of MM, which implicates an aberrant DNA repair mechanism. Studies have implicated a role for CDK12 in the control of expression of DNA damage response genes. In this study, we examined the effect of a small molecule inhibitor of CDK12–THZ531 on MM cells. Treatment of MM cells with THZ531 led to heightened cell death accompanied by an extensive effect on gene expression changes. In particular, we observed downregulation of genes involved in DNA repair pathways. With this insight, we extended our study to identify synthetic lethal mechanisms that could be exploited for the treatment of MM cells. Combination of THZ531 with either DNA-PK inhibitor (KU-0060648) or PARP inhibitor (Olaparib) led to synergistic cell death. In addition, combination treatment of THZ531 with Olaparib significantly reduced tumor burden in animal models. Our findings suggest that using a CDK12 inhibitor in combination with other DNA repair inhibitors may establish an effective therapeutic regimen to benefit myeloma patients.     

Factors influencing quantities of sugars and organic acids in blackcurrant concentrates

 Use of endogenous non-volatile flavour components, i. e. sugars and organic acids, in fruit juice products is desirable. A study of 133 blackcurrant concentrates from three seasons examined variation in sugars and acids arising from storage of fruit at freezing or sub-ambient temperature, seasonal differences, geographical origin and choice of conventional thermal-evaporative or freeze concentration technology. Compared with freeze concentrates, conventional concentrates had significantly higher contents of total sugars and acids, notably malic acid, and higher fructose/glucose, lower malic/citric acid and similar sugar/acid ratios. Concentrates from frozen fruit generally had smaller amounts of fructose, total sugars and fructose/glucose ratios than those from fresh fruit, as well as less citric, ascorbic and total acids and lower sugar/acid ratios. Principal component analysis of 40 randomly chosen concentrates showed that variance is dominated by differences in fructose, total sugars and ascorbic acid contents and sugar/acid ratios. Geographical origin and concentration technology were major sources of variance but changes in post-production sub-ambient storage could not be excluded. Received: 4 July 1997 /  Revised version: 14 October 1997     

Fluid flow stability analysis of multilayer fiber drawing

We here investigate drawing of multi-layered Newtonian and non-Newtonian fluid fibers, drawn under isothermal and non-isothermal conditions. We first develop one-dimensional equations governing mass, momentum, and energy balances and solve them numerically to obtain steady state draw root shape, velocity, and temperature profiles. These solutions are then used to perform linear stability analysis. For the case of isothermal draw, the system displays an oscillatory instability when the draw ratio (ratio of cross-sectional areas of fiber at the entrance and exit of the drawing) is higher than a critical draw ratio (highest stable draw ratio) of about 20.21. Investigation of stability behavior under non-isothermal draw conditions is performed by considering radiative heating and convective cooling. Employing only radiative heating enhances the critical draw ratio, and simultaneous heating and convective cooling increase the critical draw ratio even further. For the case of simultaneous heating and cooling, with increasing convective cooling strength, the critical draw ratio first increases, reaches a maximum, and then gradually decreases. However, with only convective cooling, the critical draw ratio decreases with an increase in convective cooling strength. We also find that the stabilizing effect of a non-isothermal operation can be enhanced by considering fluids with higher viscosity sensitivity to temperature, increasing the maximum temperature, and for sharper attenuation of the fiber cross-sectional area with length. For the case of isothermal drawing of non-Newtonian fluid fibers, the system has a higher critical draw ratio for shear thickening fluids (power-law exponent, n>1). In contrast, the use of a shear thinning fluid (n<1) reduces the critical draw ratio. Consideration of a non-isothermal operation of non-Newtonian fluid fibers reveals that the critical draw ratio is primarily determined by the non-Newtonian behavior rather than the non-isothermal drawing.     

FLAVOUR CHARACTERIZATION BY TRAINED AND UNTRAINED ASSESSORS

The flavours of four beers were characterized by four panels of assessors, using a flavour profiling system. One panel carried out duplicate assessments. The results showed that training and experience improved reproducibility and discrimination, without distorting the general pattern of flavour terms reported. On the basis of the flavour profiles, the assessors could be divided into novices, those with some experience, and experts. Those novices likely to be good assessors could also be identified.