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OBJECTIVES To compare the mechanical properties of monofilament nylon leader and orthopaedic wire for median sternotomy closure in the dog. MATERIALS AND METHODS Median sternotomy was performed in 14 canine cadaver sternums with the manubrium intact. The sternotomy was closed with either 80 lb monofilament nylon leader or 20G orthopaedic stainless steel wire in a peristernal figure of 8 pattern. Constructs were loaded in a servohydraulic material testing machine. Load at yield, maximum load, stiffness, displacement and mode of failure were compared between constructs subjected to a single cycle load to failure. RESULTS No significant differences were found in load at yield, maximum load, stiffness or displacement between the monofilament nylon leader and the stainless steel wire constructs. No implant failure was evident in the stainless steel wire constructs. Four of the monofilament nylon leader constructs failed by pulling of the nylon through the crimp. CLINICAL SIGNIFICANCE Monofilament nylon leader is mechanically comparable to stainless steel wire and potentially a suitable alternative for closure of median sternotomy in the dog.

The ability of motor oils to control valve train wear adequately is ensured by the evaluation of new formulations in a variety of standard industry tests. The most critical of these tests have single-overhead-cam valve train systems with pivoted (rocker- or finger-type) followers. Although many vehicles in service have these types of valve train, there is a strong trend towards the use of roller-follower and direct-acting tappet (DAT) systems in recently introduced passenger car engine designs. Roller designs virtually eliminate sliding between the cam and follower and in gasoline engines reduce wear and friction to low levels. Practical experience indicates that DAT systems also give lower wear and friction than pivoted systems do. The parameters affecting wear in the pivoted-follower valve trains of the Sequence VE and Peugeot TU-3 tests are analysed in comparison with equivalent DAT systems. The friction and wear benefits observed with DAT systems are shown to be inherent in the geometry and kinematics of this type of valve train. The consequences of this finding are discussed in relation to the requirements for antiwear protection provided by future motor oils.

The positions of maximum wear on the surfaces of automotive cams and followers have been found to be characterized by low velocities of the point of contact over the surface in question, in combination with significant sliding velocities and thin oil films. The modelling of these critical conditions has now been extended to examine the significance of low contact velocities in two internationally accepted engine tests for the evaluation of the anti-wear properties of lubricants in valve train systems. Calculations of the contact dwell times and the corresponding sliding distances against the opposing surfaces indicate that the particular susceptibility to wear and surface distress in these systems arises from the extreme values of these parameters experienced by particular points on the surfaces during each rotation of the cam. The conditions on the follower surfaces appear to be more severe than on the cams in this respect. It is shown that kinematic conditions representative of the more severe parts of the operating cycles of the engine tests can be reproduced in a modified Amsler two-disc machine, thus enabling the use of small, flat test specimens, which are accessible to a wide range of advanced surface analysis instruments, to facilitate the study of lubricant anti-wear additive film formation.

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core.

SummaryThe purpose of this study was to compare the holding powers of 2.7 mm pre-tapped and self-tapped screws placed closely together and tightened in small bones. Pairs of metatarsals were collected from healthy, skeletally mature Greyhounds and part of a 2.7 mm dynamic compression plate was fixed to the dorsal surface of each bone using three 2.7 mm screws. Identical screws were used throughout but only one of each pair of bones had threads pre-cut using a tap prior to insertion. All of the screws were tightened before the constructs were mounted in a materials testing machine and the centrally placed screw was loaded incrementally until failure. Load-deformation curves were plotted and yield point, ultimate load to failure, stiffness and energy prior to yield point were measured. Mean values were recorded for each parameter and Student's T-test was used to test the null hypothesis that there is no difference in holding power between pre-tapped and self-tapped screws. Significant mechanical differences were not found between pre-tapped and self-tapped screws placed closely together and tightened into small bones. Self-tapped screws can be considered for use in small animal surgery even when multiple screws are to be placed closely together in relatively small pieces of bone.

AIMSTo investigate the relation between haemoglobin in children followed longitudinally from 8 to 18 months, and developmental outcome at 18 months.METHODSThe Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) is a longitudinal survey of a geographically defined population of children born in 1991–92. In a randomly selected subsample, blood samples were assayed for Hb at 8, 12, and 18 months; a developmental assessment was carried out at 18 months on 1141 children using the Griffiths Scales of Mental Development.RESULTSThere was a strong quadratic association between Hb at 8 months and performance on the locomotor subscale at 18 months. Average scores increased with increasing Hb up to 95 g/l; there was little additional developmental benefit in Hb levels beyond 95 g/l. Infants with Hb CONCLUSIONSLow Hb concentrations (⩽ 95 g/l) in 8 month old children are associated with impaired motor development at 18 months. This cut off point corresponds to the 5th centile of Hb at 8 months. The results indicate that if there is an adverse effect of low Hb on developmental outcome, screening may be more effective at 8 months or earlier, rather than after this age. We propose to examine the importance of infant anaemia in relation to more accurate and detailed long term outcomes as the children get older.

An investigation has been made of the frequency dependence of amplitude and phase information when broadband ultrasonic pulses, in the region 1–30 MHz, are reflected from layered targets. An on line computer performing Fourier analysis of sampled ultrasonic pulses allowed both amplitude and phase information to be studied. Layers of various acoustic impedances, velocities, and attenuation have been investigated, and in particular, layers of magnetite grown on mild steel. In all cases excellent agreement between experiment and theory has been achieved. The possible use of the techniques of deconvolution has also been considered for the measurement of the thickness of layers. The methods developed have found application in the problem of determining the thickness of a corrosion layer on the inside surface of a component where access can only be gained through the outer surface.

Since the days of Sputnik, 1, Transit and Early Bird, satellite communications and navigation have followed separate development paths. Now with the development of the INMARSAT Standard-C and Enhanced Group Call systems the two will be drawn more closely together. Standard-C will provide a simple low cost satellite solution for ships to send and receive data and messages throughout the world in any weather 24 hours a day. For the mariner this will mark a significant advancement over existing conventional services. The Enhanced Group Call (EGC) system uses the basic Standard-C system architecture to broadcast Marine Safety Information (SafetyNET) and commercial calls (FleetNET) to defined geographic areas or groups of ships. The EGC system therefore brings the mariner an optimal way to automatically receive shore-to-ship distress alerts, routine weather forecasts and NAVAREA and storm warnings applicable to the area in which he is sailing. For the commercial user it offers a means to provide news, stock, commodity market and other business information to a selected group of recipients. In the future it may also provide the means for automatically updating data bases containing electronic charts, light lists, tide tables, hazardous cargo and other information currently carried in printed form. The ability to advise ships in near real-time of pertinent Marine Safety Information will be demonstrated during sea trials of the EGC system in the North Atlantic during 1987. A successful trial is expected to lead to IMO making an EGC receiver capability a part of the Global Maritime Distress and Safety System (GMDSS) carriage requirements which, together with 518 KHz NAVTEX, will enable the mariner to receive crucial Marine Safety Information automatically anywhere he sails. The Standard-C ship earth station (SES) will have the ability to transmit the vessel's position automatically when connected to an electronic positioning system, either at pre-assigned intervals or on demand when polled. The same capability may also be used to transmit meteorological observations as well as cargo and engine monitoring/performance data. Starting in 1987, INMARSAT will test and demonstrate position determination through its satellites by using ranging techniques. It is planned that some of these tests will be conducted using modified Standard-C SESs. Sea Trials of Standard-C will begin in the latter part of 1987 with commercial service from 1988. The multifunctional capabilities of this small, lightweight, low-cost SES with omnidirectional antenna are remarkable. Standard-C will therefore have a significant impact on navigation and communications practice and thinking by the marine community into the 21st Century.

Despite the fact that forest trees are in early stages of domestication there has been little direct evaluation of either the origin of, or genetic diversity within the breeding material in tree improvement programs. Allozyme variation was used to compare the total genetic diversity in the breeding programs of P. radiata within Australia and the five wild populations in North America. The current breeding populations were very similar genetically and were essentially homogenous with only 1.8% of the variation among programs. The total genetic diversity in the species was 0.12, which is a low estimate compared to most conifers. Overall in the Australian material the genetic diversity was somewhat less. The comparison of allelic frequencies in the five native populations with the Australian material indicates that the Monterey and Año Nuevo populations were probably the major source of the original introductions and that a substantial portion of the genetic diversity in the two populations has been captured in current breeding programs. The three southern populations do not appear to be currently represented in the breeding programs. The implications for future breeding strategies are discussed.

Stress patterns in lubricated rolling-contact elements have been computed from surface pressures and temperatures between pairs of rolling disks, both cylindrical or both crowned, measured by means of evaporated surface transducers. The maximum mechanical shearing stresses computed for both cylindrical and crowned disks proved to be nearly equal to those that would have occurred under static contact, but the calculated depth of those stresses was reduced for cylindrical rollers in dynamic contact. The maximum shear reversals computed for rolling cylindrical disks were noticeably below the corresponding shear differences for the static cases. Local pressure anomalies, such as the pressure spike in the one particular case chosen for investigation, did not seem to alter significantly the shear-stress patterns. Thermal shearing stresses do not appear to be a significant portion of the maximum stress but do dominate over mechanical shearing stresses near the surface of the elements.

The thickness of the film formed by each of five lubricants between a pair of disks in rolling contact has been measured by an X-ray technique for a range of loads (80,000 to 225,000 psi maximum Hertz stress), two temperatures (178 F and 250 F), and three speeds (4300 fpm to 9100 fpm). An empirical formula fitted to the X-ray data shows a much higher sensitivity of film thickness to load than is normally predicted. In order to judge whether the measurements themselves are at fault, the X-ray measuring process has been reexamined for accuracy, especially where load-dependent errors might arise. Some weaknesses are noted, such as in the amount of X-ray absorption, but these should not affect load sensitivity greatly. New experiments designed to find effects of imperfect collimation of X-rays indicate that reflection of X-rays may be significant, but these effects too do not seem to account for the anomalies of the film thickness measurements.

Synopsis The paper describes the formation of a theoretical model which aims to describe the behaviour of a reinforced concrete slab throughout the whole of its loading range from initial loading to ultimate collapse. The model is based on the use of anisotropic finite elements, and a successive approximation technique. It synthesizes the section properties ofa slab from fundamental properties of the concrete and reinforcing steel. Moments, deflections and crack patterns are produced. The use of the model is illustrated by the analysis of a slab: the results of this analysis are compared with experimental results.

In the past zoonoses that caused serious human illness also caused serious loss of animal production, but there is growing awareness of the public health problems arising from infections that cause little or no such loss. Much can be learnt from the history of the control of bovine tuberculosis and brucellosis. In both cases there was reluctance to accept that animals were the principal cause of infection, and the earliest attempts at control failed because measures were taken only against clinical cases of the disease. The essential features in control of both infections were: official recognition of a problem, willingness of governments to allocate resources, and cooperation between the medical and veterinary professions. Salmonellosis is the most important zoonotic infection in Britain today, though several Orders have reduced the reservoir of infection in food animals. It is suggested that a national team of doctors should be set up to investigate and control zoonoses, that this team should be answerable to a central agency, and that it should build up close working relationships with the nominated officers of the veterinary profession.

Presented is the advanced antenna design techniques study program. Space vehicle antenna systems and ground-based tracking antenna system parameters were studied, and requirements were established as design goals. Various types of antenna configurations were investigated to meet the established requirements. Detail design, structural aspects, and performance for the three selected antennas were studied. New material applications were investigated, and new manufacturing techniques were developed. Design and fabrication of three models and evaluation of these to demonstrate the feasibility of the selected concepts are described. Twelve space vehicle antenna concepts representing a wide range of types were investigated and evaluated from the standpoints of weight, cost, pacakageability, and advancement of erectable or expandable techniques. Seven concepts consisting of inflatable and expandable pencil-beam and fanbeam antennas were selected for further study.

The distribution of current is computed in a cylindrical semiconductor specimen provided with cylindrical metallic end caps of the same diameter as that of the specimen and electrical lead wires of much smaller diameter. Nonuniformity of the longitudinal current density of 1% or less can be obtained in specimens with electrical resistivities at least 200 times greater than that of the end caps if the lengths of the specimens are at least equal to their diameters and if the length of each end cap is at least 0.3 diam.