The interrelation of failure modes observed in the penetration of metallic targets

Three of the main modes of failure observed in the penetration of metallic armour are classified as ductile failure, adiabatic shear plugging and discing. It is demonstrated that a change from ductile modes of failure to those which involve adiabatic shearing or discing can be understood in terms of the work done to penetrate a target. Adiabatic shearing is possible if the rate of thermal softening exceeds the rate of work hardening of the target material. In adiabatic shear failure, where several shear bands propagate independently towards the rear of the target, intersection of one band with the rear surface may lead to asymmetry in the deformation. Asymmetric conditions do not favour further propagation of adiabatic shear bands and failure can be completed by discing and/or ductile tearing giving a mixed mode of failure. Discing is accentuated if the target plate shows relatively low toughness particularly in the through thickness orientation. Other studies have shown that the fractures associated with discing may be produced by shearing in the plane of the plate, and it is demonstrated that discing is more likely when fracture occurs on a number of parallel planes.     

Properties of native and immobilised preparations of β-D-glucosidase from Aspergillus niger

The enzyme β-D-glucosidase from Aspergillus niger has been immobilised through its carbohydrate moiety on concanavalin A-Sepharose and on cyanogen bromide-activated Sepharose after aminoalkylation of the carbohydrate side chains of the enzyme. For comparison, the enzyme was also immobilised on microcrystalline cellulose through its protein moiety. High retention of activity and a decrease in K_m and V_max. were observed when β-D-glucosidase was immobilised by these methods. An increase in the thermal stability of the immobilised β-D-glucosidase preparations over the soluble enzyme was achieved if it was treated with glutaraldehyde before its adsorption on concanavalin A-Sepharose or if the enzyme immobilised on cyanogen bromide-activated Sepharose was subsequently treated with glutaraldehyde. Treatment of β-D-glucosidase immobilised on microcrystalline cellulose with glutaraldehyde hardly increased its thermal stability over the soluble enzyme.     

Energy transfer in ballistic perforation of fibre reinforced composites

High speed cine techniques have been used to examine the perforation of thin targets constructed of glass fibre reinforced plastic (GRP), Spectra (Allied Signal) and Kevlar (Du Pont) composites as well as nylon and Kevlar fabrics. From the film record the kinetic, strain and (for the composites only) delamination/surface energy terms were evaluated for the rear layer of material. Simple models for the deformation of the panels were used to compare these energies, summed for all layers, with the projectile energy loss. All the energy terms are shown to be significant. The Kevlar fabric does not fit the pattern of the other materials, in that for this material nearly all the projectile energy appeared as tensile strain energy in only the rear layer of the target. This result was a consequence of the high apparent strain observed in the fabric, and is not simply explained. Energy terms not evaluated, but which may be significant, are crushing and ejection of fibres for GRP composites and spalling of matrix phase with the Spectra composites. The work highlights many of the features which need to be accounted for in modelling ballistic perforation of fabric and fibre reinforced composite materials. © 1998 Chapman & Hall     

Predominant usage of the proximal poly(A) site in alpha mRNAs is not intrinsic to the 3' termini

The maturation of IgM-expressing B cells to IgM-secreting plasma cells is associated with both an increase in mu mRNA and the ratio of secreted to membrane forms of mu mRNA. In contrast, previous studies demonstrated that in vitro the secreted form of alpha mRNA (alpha s mRNA) predominates regardless of the stage of B cell differentiation. The present study demonstrates that alpha s mRNA predominates in both B cells derived from the germinal centers of murine Peyer's patches and in the functional IgA memory population, suggesting that in vitro events accurately represent the generation of a secretory IgA response in vivo. Although the predominant usage of the alpha s poly(A) site is due to RNA processing, it does not depend on either the alpha s poly(A) site, the 3' splice site associated with the exon encoding the membrane exon of IgA (alphaM) or the alphaM poly(A) sites. Analysis of the sequence of the intron between the alpha s terminus and alphaM (alpha s-alphaM intron) demonstrates the existence of several potential regulatory elements. Furthermore, the effects of deletions within the alpha s-alphaM intron on 3' terminus usage demonstrate that the predominant usage of the proximal terminus is not strictly dependent on the length of the intron. Together with previous work, these observations support the idea that choice of 3' terminus for all Ig heavy chain genes is regulated by a similar mechanism, but specific sequences within a heavy chain gene can impinge upon that mechanism.     

Generalised model for programmable sequence controllers

A theoretical analysis of the operation of a programmable sequence controller is presented. From this, a generalised model is developed that enables the sequence controller to be implemented as a sequential machine operating in conjunction with a stored program.     

Dependence of marital problems on parental family history.

Examined the relation of marital complaints to family history in 1,624 psychiatric outpatients. Marital complaints were recognized to be an aspect of a broader "depressive spectrum disorder" with distinctive age, gender, alcohol, and neurotic depressive symptom characteristics. However, holding constant the depressive spectrum characteristics, a specific independent relation of marital complaints to family history of parental marital discord was verified. It is concluded that marital problems have 2 primary etiologies in the psychiatric population, one as part of a broader depressive spectrum disorder and the other a more specific familial behavior patterning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of fast-rate, slow-rate, and silent previewing interventions on reading performance

Researchers investigated the effects of three different previewing interventions on the oral reading rates of 12 junior and senior high school students with learning disabilities. Under fast-rate listening previewing (FRLP), students were instructed to follow silently as experimenters read from a text at an average rate that was 77.7% faster than the students' current oral reading rate. During slow-rate listening previewing (SRLP), students followed along as experimenters read at an average rate that was 22.5% faster than the students' reading rate. Students were instructed to read passages silently under silent previewing (SP). Immediately following each previewing intervention, students read the same passage aloud. The number of words read correctly per minute and the number of errors per minute served as dependent variables. The results showed statistically significant decreases in error rates under SRLP and SP. The results also showed that SRLP resulted in statistically significantly fewer errors per minute than FRLP. These results suggest that orally reading while students follow along at a rate much higher than their current reading rates may not be as beneficial as reading aloud at slower rates.