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The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.
We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band (
), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.
A novel transmission line structure has been developed to facilitate the delivery of both adrenaline and microwave energy to achieve hemostasis. A proximal end impedance transformer and radiative tip have been designed and manufactured to provide good match between the novel hollow transmission line and the microwave source and tissue, respectively. Further consideration of the challenges and problems encountered along with evidence of successful microwave energy delivery at 5.8 GHz into porcine liver model providing a controlled and focused coagulation zone of approximately 5 mm.
Se is an essential element for animals. In man low dietary Se intakes are associated with health disorders including oxidative stress-related conditions, reduced fertility and immune functions and an increased risk of cancers. Although the reference nutrient intakes for adult females and males in the UK are 60 and 75 μg Se/d respectively, dietary Se intakes in the UK have declined from >60 μg Se/d in the 1970s to 35 μg Se/d in the 1990s, with a concomitant decline in human Se status. This decline in Se intake and status has been attributed primarily to the replacement of milling wheat having high levels of grain Se and grown on high-Se soils in North America with UK-sourced wheat having low levels of grain Se and grown on low-Se soils. An immediate solution to low dietary Se intake and status is to enrich UK-grown food crops using Se fertilisers (agronomic biofortification). Such a strategy has been adopted with success in Finland. It may also be possible to enrich food crops in the longer term by selecting or breeding crop varieties with enhanced Se-accumulation characteristics (genetic biofortification). The present paper will review the potential for biofortification of UK food crops with Se.
Dental enamel is the most durable bioceramics produced by a vertebrate as it is designed to perform masticatory functions throughout its lifetime. The understanding of the mechanism of enamel formation and effects of proteins during the biomineralization process are fundamental issues, essential for both potential enamel regeneration and as a base for synthesis, via self-assembly, of biomimetic composites.
The biomineralization process of enamel is carried out by ameloblast cells that line the inner enamel epithelium and secrete an extracellular protein matrix onto a mineralized dentin surface at the dentin-enamel junction (DEJ). A major matrix protein, amelogenin, is believed to regulate the mineralization of hydroxyapatite (HAP) in the enamel tissue. It has been shown to undergo self-assembly in vitro and in vivo to form nanospheres of ∼20nm in diameter. Previous TEM studies have shown that the nanospheres align along the length (c-axis) of hydroxyapatite (HA) crystals. There are two domains, namely A (residues 1-42) and B (residues 157-173), that control the self-assembly behavior of the nanospheres.
The understanding of detailed structures and properties of enamel is essentia for designing new implant materials that faithfully resemble enamel structure or to regenerate enamel through biomimetics using proteins as templates. As part of a greater effort in enamel biomimetics, this work focused on nanostructures and mechanical properties of individual enamel rods using the mause as a test animal.
A mature mouse incisor consists of two layers - dentin and enamel. In order to perform its normal masticatory function, the incisor must have sufficiently high flexural strength, toughness, and wear resistance. Enamel, which is highly mineralized (∼100%) with a knitted micro-architecture, satisfies the mechanical property requirements. It is known that elongated hydroxyapatite (HAP) crystals mineralize in bundles, i.e., enamel rods, and organize in a 3-D cross pattern. [1,2] However the organizations of HAP crystals within and between rods are not well understood.
Enamel, which covers the anatomical crown of the tooth, is the hardest tissue in human body. Supported by a soft but tough dentin structure, the tooth is an advanced nanocomposite that can endure mastication stresses throughout a lifetime. A detail understanding the structure of the tooth, and sepecifically detin-enamel junction (DEJ), not only provides a sound basis for a model for synthetic dental restoration, but also provides lessons from nature on biomimetic regeneration with mechanical integrity. Enamel is a non-growing mineralized tissue and is subjected to most mechanical abuse. Dentin-enamel junction plays a critical role of distributing load between two very dissimilar materials - enamel and dentin. Bulk scale mechanical tests have shown that induced cracks on enamel tend to be arrested DEJ. Furthermore, nanoindentation measurements have also shown that there is a gradual decrease in hardness from enamel to dentin in the DEJ zone suggests a strong mechanical coupling in both deciduous and adult incisors. The objective of this investigation, through microscopical study, is to understand how these two dental hard tissues structurally couple through their junction zone.
Computerized tomographic (CT) imaging provides detailed information on the paranasal sinuses and is now well established as an alternative to standard radiographs. The planning and safety of surgery to the paranasal sinuses is greatly improved by CT imaging. We describe a new CT protocol comprising a limited coronal and axial scan series, based on ourexperience with the previously described ‘CT Mini-series’.
Changes in the concentrations of various metabolites in mammary secretions (organic acids, UDP-hexoses and nucleotides) have been observed at the onset and cessation of lactation. All metabolites, with the exception of galactose, increased dramatically in concentration just before and immediately after parturition. Galactose concentrations decreased with the onset of lactation. After regular milking ceased, the concentrations of these metabolites in milk contained within the udder fell, but the rates of decline varied.
Imipramine and phenelzine were ineffective in the treatment of five primary unipolar depressives with delusions, even when plasma levels of imipramine and desmethylimipramine or activity of platelet monoamine oxidase suggested that an adequate dose of drug had been given. Four patients went on to receive ECT and all responded well. Five non-delusional patients responded satisfactorily to the antidepressant drug given. Nine out of ten subjects were women. Non-delusional patients showed some placebo response.
ECT is considered to be the treatment of choice in the acute phase of delusional depression in women.
Catechol O-methyltransferase of lysed human red blood cells was assayed under optimal conditions, using saturating concentrations of the substrates, S-adenosyl-L-methionine and 3,4-dihydroxybenzoic acid. The mean enzyme activity found in 24 normal subjects was 29.2 nmol/hr/ml RBC. The mean activity in blood of 33 female unipolar depressives was not significantly different from normal. However, higher enzyme activities were observed in the blood of 11 schizophrenic patients (38.9 nmol/hr/ml RBC). Partially purified enzyme preparations from blood of normal and schizophrenic individuals were indistinguishable with respect to substrate specificities, isoelectric pH values, and ratios of the two O-methylated products. Therefore it is unlikely that any defect in O-methylation which may occur in schizophrenia can be attributed to a change in the intrinsic properties of erythrocyte catechol O-methyltransferase.
[Methylene-14C]-L-tryptophan was administered intravenously to five patients suffering from severe depression before and after clinical recovery, and to six control subjects; all subjects were tested while on a standard diet. [14C]-5-Hydroxyindoleacetic acid and [14C]-indoleacetic acid were isolated from urine during the following 48 hours and purified to constant specific radioactivity (SA). From the SA and the determination of the total excretion of the two acids their percentage conversion from labelled tryptophan was estimated. There was no consistent difference found, in patients before and after recovery, or between patients and controls, in the conversion of tryptophan to these indole acids. In another series of 11 depressive patients and 11 controls, plasma total (acid-soluble) tryptophan was measured at frequent intervals up to three hours after intravenous administration of a loading dose (1 g) of L-tryptophan. The height of the curves of plasma tryptophan throughout the three hour period was greater than in the depressive patients, even after they had recovered, than in the controls. It is concluded that the apparent volume of distribution of tryptophan is reduced in depressive individuals. This is consistent with other findings of increased protein-binding of plasma tryptophan and reduced CSF tryptophan levels in depressive patients.
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