Algorithm-agile encryption in ATM networks

ATM encryption allows users to select an appropriate algorithm to implement security services for a given transmission. This flexibility is especially helpful when the choices for encryption algorithms between transmission points are limited. Algorithm flexibility also helps reduce operational costs, since multiple algorithms-which are typically implemented in several encryptors-can all be implemented in one device     

Texture strengthening and strength differential in titanium-6Al-4V

The alloy titanium-6 Al-4 V has been processed in the laboratory to develop a wide range of textures, and determinations have been made of the yield loci for these conditions. Optical and electron metallography have been used to gain information about the operative deformation modes under various states of stress. Only limited texture strengthening is observed for conditions of tensile loading, although quite significant effects are found in compression. In strongly textured material a large strength differential occurs along thec axis direction, but this cannot be attributed to twinning. It is shown that <c +a> slip can play a major role in plastic deformation, and that the observed mechanical properties result from the peculiar characteristics of the <c +a> dislocations. Formely with the Department of Physical Metallurgy, Univresity of Birmingham     

Energy savings due to changes in design of ventilation and air flow systems

Procedures for the design of ventilation and air flow systems are shown to be energy wasteful. The cause lies both in the methodologies and their technical bases, and in the influence of other factors that enter into a final systems choice for a building (particularly economics).The issue of general outside air requirements is discussed. It is found that any system in which outside air supply is sufficient to control body odor necessarily meets oxygen requirements many times over, and that the ventilation rate can be reduced by about 45% to 60% if higher humidities are used. The long-standing belief that required ventilation flow rate for odor control must increase as air space per occupant decreases has previously been proven untrue, yet a survey of the ASHRAE recommendations and various building codes shows that present standards are based on this inaccurate and energy-wasteful principle. New standards, including a rate of 7.5 cmf/person of outdoor air (not conditioned) during the heating season, are proposed based on the result that the ventilation rate is independent of air space per person.Air distribution systems and sub-systems are analyzed in terms of minimum energy requirements. Energy saving by velocity reduction is discussed. Fan power requirements for a high velocity air distribution system are increased by 2500% over that for a low velocity system in commercial buildings.A comparison of the “old” ASHRAE definition of Effective Temperature, which serves as a thermal comfort criterion in AC systems design, is made with the “new” definition, and the consequent energy savings that should result when the “new” definition is accepted in practice is demonstrated.     

Surface instabilities on statically strained plastic solids

An exploratory study is carried out of various aspects of the development of instabilities of traction-free surfaces of statically strained, rate-independent elastic-plastic solids. Existence of surface instabilities as predicted by either a bifurcation analysis or a quasi-static, imperfection-growth analysis, is found to be strongly dependent on the type of constitutive law assumed. In most instances no instabilities are found using the standard plastic flow law based on a smooth yield surface and isotropic hardening. Instabilities are predicted when a finite strain deformation theory is assumed. These are documented for a full range of proportional overall straining histories using a bifurcation analysis. A finite element analysis employing a corner theory of plasticity is used to study the non-linear growth of the instabilities starting from small initial surface undulations for the case of plane strain deformation. Some experimental observations of surface irregularities which may be due to surface instabilities are reported and discussed.     

Thiopyrano[2,3,4-cd]indoles as 5-lipoxygenase inhibitors: synthesis, biological profile, and resolution of 2-[2-[1-(4-chlorobenzyl)-4-methyl-6-[(5-phenylpyridin-2-yl)methoxy]-4,5 -dihydro-1H-thiopyrano[2,3,4-cd]indol-2-yl]ethoxy]butanoic acid

Leukotriene biosynthesis inhibitors have potential as new therapies for asthma and inflammatory diseases. The recently disclosed thiopyrano[2,3,4-cd]indole class of 5-lipoxygenase (5-LO) inhibitors has been investigated with particular emphasis on the side chain bearing the acidic functionality. The SAR studies have shown that the inclusion of a heteroatom (O or S) in conjunction with an alpha-ethyl substituted acid leads to inhibitors of improved potency. The most potent inhibitor prepared contains a 2-ethoxybutanoic acid side chain. This compound, 14d (2-[2-[1-(4-chlorobenzyl)-4-methyl-6-[(5-phenylpyridin-2-yl)methox y]- 4,5-dihydro-1H-thiopyrano[2,3,4-cd]indol-2-yl]ethoxy]-butanoic acid, L-699,333), inhibits 5-HPETE production by human 5-LO and LTB4 biosynthesis by human PMN leukocytes and human whole blood (IC50s of 22 nM, 7 nM and 3.8 microM, respectively). The racemic acid 14d has been shown to be functionally active in a rat pleurisy model (inhibition of LTB4, ED50 = 0.65 mg/kg, 6 h pretreatment) and in the hyperreactive rat model of antigen-induced dyspnea (50% inhibition at 2 and 4 h pretreatment; 0.5 mg/kg po). In addition, 14d shows excellent functional activity against antigen-induced bronchoconstriction in the conscious squirrel monkey [89% inhibition of the increase in RL and 68% inhibition in the decrease in Cdyn (0.1 mg/kg, n = 3)] and in the conscious sheep models of asthma (iv infusion at 2.5 micrograms/kg/min). Acid 14d is highly selective as an inhibitor of 5-LO activity when compared to the inhibition of human 15-LO, porcine 12-LO and ram seminal vesicle cyclooxygenase (IC50 > 5 microM) or competition in a FLAP binding assay (IC50 > 10 microM). Resolution of 14d affords 14g, the most potent diastereomer, which inhibits the 5-HPETE production of human 5-LO and LTB4 biosynthesis of human PMN leukocytes and human whole blood with IC50s of 8 nM, 4 nM, and 1 microM respectively. The in vitro and in vivo profile of 14d is comparable to that of MK-0591, which has showed biochemical efficacy in inhibiting ex vivo LTB4 biosynthesis and urinary LTE4 excretion in clinical trials.     

Epidemiological study of angioedema and ACE inhibitors

A total 30,040 pregnancies were reviewed at one institution over 5 years to determine the incidence of venous thrombotic complications. Thirty-one patients experienced such complications related to pregnancy (incidence 0.1%); 13 had deep venous thrombosis and 14 had superficial venous thrombophlebitis diagnosed by duplex ultrasound. Four had pelvic vein thrombophlebitis diagnosed by computed tomography scan; three patients (one from each group) sustained a non-fatal pulmonary embolus. Of those with deep venous thrombosis, 10 (77%) were left-sided, and three (23%) were right-sided. Three had a prior history of deep venous thrombosis and one of pulmonary embolism. Of those with superficial venous thrombophlebitis, seven (50%) were left-sided, six (43%) were right-sided, and one (7%) was bilateral. Most with deep venous thrombosis presented later in pregnancy; three in the first trimester, two in the second, three in the third, and five early postpartum. Most (10/14) with superficial venous thrombophlebitis presented within 48 hours of delivery. Distribution of thrombi in those with deep venous thrombosis was compared with 643 non-pregnant women with a similar condition. A pattern of proximal involvement on the left was found, with left common femoral vein (54% versus 28%, P = 0.03) and superficial femoral vein (62% versus 26%, P = 0.006) more often involved in pregnant patients. The average number of vein segments involved was greater on the left than the right (5.3 versus 3.7). Symptoms of chronic venous insufficiency developed in three with deep venous thrombosis (25%) and in three with superficial venous thrombophlebitis (27%). None had recurrence of deep venous thrombosis. It is concluded that venous thrombotic complications associated with pregnancy are not necessarily benign, with the risk of pulmonary embolism and chronic venous insufficiency not limited to patients with deep venous thrombosis only.     

A bivariate normal model for intra-accident correlations of driver injury with application to the effect of mass ratio

The data analysed consists of the joint distribution of severities of injury to vehicle drivers in head-on crashes, stratified according to the relative masses of the vehicles. On the basis of some fairly strong assumptions, a model is developed which results in the joint distribution being bivariate normal. The parameters are interpretable in terms of the effect of velocity change on injury severity, and the relative variability of velocity change and of injury severity at a particular velocity change. The predictions made by the model enjoy a considerable degree of success.     

InGaAsP/InGaAs heterojunction p-i-n detectors with low dark current and small capacitance for 1.3?1.6 ?m fibre optic systems

A new long wavelength p-i-n photodetector, consisting of an In0.53 Ga0.47 As absorbing layer and an adjacent InGaAsP p-n junction is demonstrated. These diodes exhibit dark currents as low as 0.2 nA and a capacitance < 0.5 pF at ? 10 V for a device area of 1.3 × 10?4 cm2. The external quantum efficiency is ? 60% at ? = 1.3 ?m for front illumination. A systematic study of the background doping of the quaternary layers using different InP sources is also reported.     

The generation of point defects in GaAs by electron-hole recombination at dislocations

The degradation of GaAs heterojunction lasers results in the formation of long dislocation dipoles which grow by a climb process involving point defect concentrations of the order of 10¹⁹ cm⁻³. The driving force for this climb process is not understood and it has been suggested that the material contains a supersaturation of native interstitials which condense on the dislocation during device operation. An alternative model proposed that the driving force is related to the energy released by electron-hole recombination on the dislocation which is partially dissipated by the dislocation emitting vacancies into the surrounding lattice.Gallium arsenide substrates containing greater than 2 × 10¹⁸ tellurium atoms cm⁻³ contain interstitial concentrations of the order of 10¹⁷ cm⁻³ which condense out to form small dislocation loops during an anneal at 880°C. The presence of these loops indicates that the annealed material does not contain excess interstitials in solution. This annealed material was optically pumped and examined by transmission electron microscopy. It was found that the loops developed into dipoles typical of degraded lasers. The number of point defects involved in this climb process increased with increasing pumping power and time. These results are discussed in terms of the two mechanisms listed above and it is concluded that the energy released by electron-hole recombination at the dislocation provides the driving force for the climb process.