To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The development of laser wakefield accelerators (LWFA) over the past several years has led to an interest in very compact sources of X-ray radiation – such as “table-top” free electron lasers. However, the use of conventional undulators using permanent magnets also implies system sizes which are large. In this work, we assess the possibilities for the use of novel mini-undulators in conjunction with a LWFA so that the dimensions of the undulator become comparable with the acceleration distances for LWFA experiments (i.e., centimeters). The use of a prototype undulator using laser machining of permanent magnets for this application is described and the emission characteristics and limitations of such a system are determined. Preliminary electron propagation and X-ray emission measurements are taken with a LWFA electron beam at the University of Michigan.
ZnO has a huge potential and is already a crucial material in a range of key technologies from photovoltaics to opto and printed electronics. ZnO is being characterized by versatile metrologies to reveal electrical, optical, structural and other parameters with the aim of process optimization for best device performance. The aim of the present work is to reveal the capabilities of vacuum ultra-violet (VUV) reflectometry for the characterization of ZnO films of nominally 50 nm, doped by Ga and In. Optical metrologies have already shown to be able to sensitively measure the gap energy, the exciton strength, the density, the surface nanoroughness and a range of technologically important structural and material parameters. It has also been shown that these optical properties closely correlate with the most important electrical properties like the carrier density and hence the specific resistance of the film. We show that VUV reflectometry is a highly sensitive optical method that is capable of the characterization of crucial film properties. Our results have been cross-checked by reference methods such as ellipsometry and X-ray fluorescence.
We present data on micrometer-scale localized single-pulse laser irradiation of Au, Cu, Al, or Ti films on borosilicate glass substrates. These metals represent a range of thermal properties, chemical reactivity levels, and relevance to specific applications. A mask projection technique employing a Q-switched Nd:YAG laser, emitting at its fourth harmonic of 266nm, was used to produce the irradiation spots in this work. The metal films, deposited by RF-sputtering, had thicknesses of several hundred nanometers. Sample irradiation was performed in either vacuum or ambient air, and the resulting microstructures were examined by electron microscopy. The results indicate that irradiation of Cu films can lead to the formation of bumps, sharp cones or protrusions. However, the controllability of these structures on Cu films is limited, compared to those formed on Au or Si. The results, upon irradiation of Ti films, are limited to melting and surface roughening or ablation openings, regardless of the conditions of irradiation, film thickness, substrate or ambient gas. The modifications that occur within Al films are reproducible, but limited in shape and size.
To present the auditory implant manipulator, a navigation-controlled mechanical and electronic system which enables minimally invasive (‘keyhole’) transmastoid access to the tympanic cavity.
Materials and methods:
The auditory implant manipulator is a miniaturised robotic system with five axes of movement and an integrated drill. It can be mounted on the operating table. We evaluated the surgical work field provided by the system, and the work sequence involved, using an anatomical whole head specimen.
The work field provided by the auditory implant manipulator is considerably greater than required for conventional mastoidectomy. The work sequence for a keyhole procedure included pre-operative planning, arrangement of equipment, the procedure itself and post-operative analysis.
Although system improvements are necessary, our preliminary results indicate that the auditory implant manipulator has the potential to perform keyhole insertion of implantable hearing devices.
To determine the prescribing patterns for antipsychotics in care homes for the elderly, a cross-sectional study was carried out using data from the intervention group of a randomised controlled trial of medication review in care homes.
Of 331 residents studied, 67 (20%) were prescribed an antipsychotic (70% atypical); 57 of these (85%) did not have a diagnosis of a psychotic disorder. The antipsychotic prescribing rate was 32% (46 out of 146) for those with dementia and 10% (17 out of 174) for those without dementia. A quarter (82 out of 331) had received a medication review by the general practitioner in the preceding 12 months.
One-fifth of residents were prescribed an antipsychotic with little evidence of review. Systems should ensure residents' treatment is reviewed regularly.
Alternate 2·4 m wide strips of a mixture of birdsfoot trefoil (Lotus corniculatus L.) with white clover (Trifolium repens L.) (BW), and of red clover (Trifolium pratense L.) (RC) were offered in the proportions (by area) of 0·80[ratio ]0·20, 0·67[ratio ]0·33, 0·33[ratio ]0·67 and 0·20[ratio ]0·80 to yearling heifers in groups of three for periods of 3 days over four replicates in time, balanced for effects of previous treatments. Observations on the distribution of grazing activity and biting rate were made over 3 h periods each evening, and on the morning of Day 2. Biting rates were consistently higher on BW than RC (52·3 v. 46·3±0·59 bites/min, P<0·001). Initially the animals showed a strong tendency to concentrate grazing on the sward of smaller proportional area, but the selection coefficient (log θ) changed from positive to negative with time as herbage on minority strips was depleted. These results are discussed in the context of concepts of partial grazing preference.
The effects of manipulation of sward maturity on ingestive behaviour and diet selection of grazing cattle were tested in two experiments using legumes which are equally preferred by cattle. Yearling heifers, in groups of three, grazed plots formed by alternate 2·4 m wide strips of a mixture of birdsfoot trefoil (Lotus corniculatus L.) and white clover (Trifolium repens L.) (BW) and strips of red clover (Trifolium pratense L.) (RC). The treatments comprised four combinations of each of the two swards at two contrasting levels of maturity/height replicated over four successive 3-day periods, in an order which balanced the effect of previous treatments. Observations of the distribution of grazing activity and biting rate were made over 3-hour periods each evening and in the morning of Day 2.
Rate of biting was generally greater on immature than mature swards, and on BW than on RC, with little evidence of interactions between these effects. The animals demonstrated partial preference throughout the two studies, the proportion of grazing time devoted to BW being 0·40±0·010 in Expt 1 and 0·47±0·017 in Expt 2. The distribution of grazing time between sward type and maturity combinations was influenced progressively by herbage mass and height contrasts as strips were grazed down. An overall analysis using the results from these studies and a companion experiment indicated differences between studies in partial preference for BW and RC which appeared to be related to variations in sward morphology.
A technology platform is described for the integration of low-loss inductors, capacitors, and MEMS capacitors on a high-resistivity Si substrate. Using this platform the board space area taken up by e.g. a DCS PA output impedance matching circuit can be reduced by 50%. The losses of passive components that are induced by the semi-conducting Si substrate can effectively be suppressed using a combination of surface amorphisation and the use of poly crystalline Si substrates. A MEM switchable capacitor with a capacitance switching factor of 40 and an actuation voltage of 5V is demonstrated. A continuous tuneable dual-gap capacitor is demonstrated with a tuning ratio of 9 using actuation voltages below 15V.
ULTRASOUND PHYSICS, TECHNOLOGY AND HEMODYNAMICS
Arnold P. G. Hoeks, Departments of Biophysics and Physiology, Cardiovascular Research Institute Maastricht, The Netherlands,
Robert S. Reneman, Departments of Biophysics and Physiology, Cardiovascular Research Institute Maastricht, The Netherlands
Since 1990 a growing interest has developed for the dimensions, composition and structure of the arterial wall, specifically of such elastic arteries as the ascending and descending aorta and the carotid arteries. Functionally, the elastic arteries dampen the pressure pulse associated with a given volume pulse as ejected by the heart by an increase in cross-sectional area, thereby absorbing temporarily the volume pulse. The arterial wall will respond to a chronically elevated blood pressure by an increase in wall thickness to maintain wall stress at the same level. To what extent the increase in wall thickness is associated with a change in wall structure and composition, or can be regarded as a prelude to pathophysiological changes, like atherosclerosis, is still subject to debate. To be able to shed light on these relations, if any, direct and local information, among others, about the end-diastolic artery diameter and its change during the cardiac cycle, wall thickness and local blood pressure are required. These data allow the computation of the Young's modulus, a measure of elasticity, which characterizes the mechanical properties of the wall independent of wall mass, as well as the compliance, a measure of blood volume storage capacity which is of relevance for the hemodynamics.
The dimensions, mass and composition of the arterial wall do not only change in response to the transmural (pulsatile) pressure, but also in relation to the prevailing wall shear stress, i.e. the drag exerted by the flowing blood on the wall.
Various silicate glasses (fused silica, soda-lime, Na- and K-borosilicates, lithia-alumina silicate, and Pyrex®) were implanted with 8 x 1015 285 keV Au/cm2. Colloid growth was monitored as a function of annealing and N implantation (2 x 1017 35 keV N/cm2). Annealing to 1040 °C for fused silica and to 600 °C for the other glasses resulted in Au aggregation and optical absorption. Radiation damage removal is associated with the fused silica annealing; the aggregation of Au at lower temperatures for the other glasses is expected because of the lower glass transition temperature. Phase-seption in the alkali-borosilicates may be important because of grain-boundary diffusion. N implantation did not significantly affect nanocluster growth.
The construction of a prototype telescope is now reaching the stage of mirror polishing and building the active cell. Three blanks have already been produced. Two polishing methods are tested, utilizing the stressing technics, or involving excentered polishing strokes. A working model of one leg of the telescope translator has been built.
The pattern of food intake can affect the regulation of body weight and lipogenesis. We studied the effect of meal frequency on human energy expenditure (EE) and its components. During 1 week ten male adults (age 25–61 years, body mass index 20·7–30·4 kg/m2) were fed to energy balance at two meals/d (gorging pattern) and during another week at seven meals/d (nibbling pattern). For the first 6 d of each week the food was provided at home, followed by a 36 h stay in a respiration chamber. O2 consumption and CO2 production (and hence EE) were calculated over 24 h. EE in free-living conditions was measured over the 2 weeks with doubly-labelled water (average daily metabolic rate, ADMR). The three major components of ADMR are basal metabolic rate (BMR), diet-induced thermogenesis (DIT) and EE for physical activity (ACT). There was no significant effect of meal frequency on 24 h EE or ADMR. Furthermore, BMR and ACT did not differ between the two patterns. DIT was significantly elevated in the gorging pattern, but this effect was neutralized by correction for the relevant time interval. With the method used for determination of DIT no significant effect of meal frequency on the contribution of DIT to ADMR could be demonstrated.
Damage depths for Ar-implanted fused silica have been examined by Rutherford backscattering (RBS) and elastic recoil detection (ERD) ion-beam analysis. H incursion (6 at. %) from ambient atmospheres to twice TRIM values was found for damage depths which intersected the surface. H implants were used to decorate Ar damage for deeper Ar implants. The incursion of H for high-fluence implants is important for optoelectronic applications.
Results from two studies involving challenge with respiratory syncytial viruses showed that volunteers who developed colds were more sensitive to a visually distracting pattern presented prior to virus challenge than were volunteers who did not get a cold. Volunteers with sub-clinical infections reported more illusions after virus challenge than they had done before, whereas uninfected volunteers and those with colds tended to report fewer illusions on the second test. These effects did not occur when volunteers were challenged with either a coronavirus or rhinovirus. Overall, the results confirm that behavioural measures may be related to susceptibility to subsequent illness, and that viral infections may influence visual perception. They also show that the effects vary according to the nature of the infecting agent, which agrees with results from studies looking at other aspects of behaviour.
Metal colloids in glasses can yield an enhanced (χ((3)) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped phosphate glass as a function of N and H implantation. Some preliminary results for Cu-implanted glasses are presented.
Many properties of implanted fused silica (e.g., surface stress, hardness) exhibit maximum implantation-induced changes for collisional energy deposition values of ∼1020 keV/cm3. We have observed a second critical energy deposition threshold value of about 1022 keV/cm3 in stress and hardness measurements as well as in many other experiments on silicate glasses (leaching, alkali depletion, etching rate, gaseous implant redistribution). The latter show evidence for damage depths exceeding TRIM ranges by about a factor of 2. For crystalline quartz, a similar threshold value value has been found for extended damage depths (greater than TRIM) for 250 kev ions (H-Au) as measured by RBS and interference fringes. This phenomenon at high damage deposition energy may involve the large stress gradients between damaged and undamaged regions and the much increased diffusion coefficient for defect transport.