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We present a high precision frequency determination method for digitized NMR FID signals. The method employs high precision numerical integration rather than simple summation as in many other techniques. With no independent knowledge of the other parameters of a NMR FID signal (phase ф, amplitude A, and transverse relaxation time T2) this method can determine the signal frequency f0 with a precision of if the observation time T ≫ T2. The method is especially convenient when the detailed shape of the observed FT NMR spectrum is not well defined. When T2 is +∞ and the signal becomes pure sinusoidal, the precision of the method is which is one order more precise than the ±1 count error induced precision of a typical frequency counter. Analysis of this method shows that the integration reduces the noise by bandwidth narrowing as in a lock-in amplifier, and no extra signal filters are needed. For a pure sinusoidal signal we find from numerical simulations that the noise-induced error in this method reaches the Cramer-Rao Lower Band (CRLB) on frequency determination. For the damped sinusoidal case of most interest, the noise-induced error is found to be within a factor of 2 of CRLB when the measurement time T is 2 or 3 times larger than T2. We discuss possible improvements for the precision of this method.
To explore the use of phthalocyanine materials as a solid-state component in an optical limiter, the issues of morphology, film processing and optical limiter activity/stability are investigated. Metal-free and lead phthalocyanine films with glassy morphologies are obtained by chemically functionalizing the ring periphery with an amine-epoxy substitution. Uniform films were obtained by a shearing technique. Comparative optical measurements are made on the amine-epoxy lead phthalocyanine compound as a concentrated solution and as a glassy thin film. Both the solution and film are reverse saturable absorbers at 590 nm. The concentrated solution is a very effective optical limiter. The glassy thin film is susceptible to damage (cavitation caused by the incident beam) and performs comparably only at low incident energies. A liquid matrix may have the benefit of self-healing such damage.
Systematic studies of the nonlinear optical properties of metallo-organic materials have led to the development of promising new phthalocyanine materials for optical limiting. Several heavy metal substituted phthalocyanines exhibit a strong nonlinear absorption that is useful for optical limiters in the visible. In fast optical systems, other mechanisms, such as the thermal refraction, contribute to the limiting. The spectral window for limiting can by modified by altering the molecular structure.
Material technology for future microelectronics will require advances in all facets of materials and processing. Low dielectric constant resins that exhibit facile processing and good thermal and mechanical behavior represent one area of needed research and development. The dielectric constant must be lower than that of amorphous silicon dioxide and possess the right properties for integration with future metallurgies such as copper. Several thermoset resins that were predicted to possess the necessary characteristics have been synthesized and studied. These include a copolymer of 1,3,5-tris(2-allyloxy-hexafluoro-2-propyl) benzene with polymethylhydrosiloxane and several cyanate ester resins. Thermal gravimetric analysis indicated significant degradation between 300 and 400 degrees C depending upon the resin. Dielectric constants were measured up to 40 GHz and ranged from 2.25 to 2.75. Compatibility with copper multilevel processing was addressed. The processability of the dielectric resins was investigated to address the integration issues associated with the fabrication process.
Using gel electrophoresis we demonstrate the attachment of short ssDNAs to a new type of water-soluble gold nanocluster that is encapsulated with ethylene oxide ligands. Initial experiments indicate that these DNA/nanocluster conjugates can subsequently be hybridized to a longer DNA template suggesting a pathway for nanofabrication of multi-cluster assemblies.
The severity of the trypanosomiasis problem in a particular location is traditionally assessed in terms of a challenge index – the product of some measure of tsetse abundance and infection rate – which is assumed to be proportional to the force of infection. However, this index masks variation in the force of infection between herds and among individuals within herds. It is also not comparable between sites since the relative abundance of tsetse to hosts may vary. We have studied spatial distribution of herds of cattle in relation to tsetse in The Gambia and calculated an index of challenge based on the ratio of vectors to hosts over the livestock ranging area. This index is strongly correlated with estimates of the force of infection calculated from the incidence of infection in susceptible zebu; and it provides information on heterogeneity in exposure of different herds to tsetse.
There is a strong prima facie case linking the abuse of psychiatry with difficulties about the concept of mental illness. However, a survey of recent Soviet literature showed that the concept of disease employed in the former USSR (where abuse was for a time widespread) was similar to its counterparts in the UK and USA in being strongly scientific in nature. A number of factors - legal, bureaucratic and professional - are important in abuse becoming widespread. These, however, fail to explain why psychiatry, rather than physical medicine, should be vulnerable to abuse. It is here that the concept of disease could be important. A scientific model of disease suggests that a significant vulnerability factor is the relatively underdeveloped status of psychiatry as a science. This leaves room for poor standards of scientific work in clinical research and practice, factors which are recognised as important in the Soviet case. In addition to the scientific element, there is an evaluative element of meaning in the concept of disease. Hence a second vulnerability factor could be the evaluatively problematic nature of judgements. of mental illness. It is concluded that a failure to recognise this factor greatly increases the vulnerability of psychiatry, not only to gross abuses, but also to inadvertent misuses of involuntary treatment in everyday practice. This conclusion, far from undermining the role of science in psychiatry, is a step towards clarifying its proper role.
Permanent blindness, is a very rare, but devastating complication of simultaneous bilateral neck dissection. Most otolaryngologists/head and neck surgeons are unaware that amaurosis can result from this surgery, and this paper is meant as a poignant reminder of that end. A case report is presented, followed by a discussion of possible aetiology; a management protocol is proposed.
In a Gambian village, the peak collections of females of the complex of Anopheles gambiae Giles occurred three months after the onset of the heaviest rains; 32% of these were A. melas Theobald, and 54% of blood-meals were identified as originating from man. Counts of A. gambiae s.l. in rooms containing permethrin-treated bed nets were compared with those in rooms containing placebo-treated nets. The numbers in the permethrin-treated nets were far lower than in placebo-treated nets. A higher rate of exophily was noted in rooms containing permethrin-treated nets. The numbers of unfed A. gambiae s.l. found inside the rooms with placebo-treated nets were significantly higher than those with permethrin-treated nets. However, the proportion fed and the mortality in the exit traps were not significantly affected by permethrin treatment. Three-minute bioassays conducted on four different fabric types impregnated at the same concentration showed that the toxicity varied between the fabrics. Handwashing severely reduced the toxicity and approximately halved the permethrin content. Bed nets are frequently washed in Gambian villages, and this could be a problem in the application of permethrin impregnation of bed nets for vector control. Methods are discussed to overcome this problem at the village level.
The sex-stimulant contact pheromone present in the cuticle of female tsetse Glossina pallidipes Austen has been extracted with hexane, separated by preparative gas chromatography and identified by mass spectrometry. The aphrodisiac, consisting of 13,17-dimethylpentatriacontane and 15,19-dimethylpentatriacontane, is present in cuticular extracts of 1-week-old females and, in lower amounts, in teneral females but it is almost absent in males of all ages. Full copulatory responses to hexane-washed dead males treated with the two dimethylpentatriacontane isomers were induced in 10–20-day-old adult male G. pallidipes. The practical uses to which this discovery can now be put—towards the mass-rearing and control of G. pallidipes— are discussed in detail.
Entomologists will be interested to learn of the occurrence of a near relative of the Horn Fly, HŒmatobia serrata, in the middle of the great cranberry swamps of Northern Minnesota. These vast low areas extend for hundreds of square miles in the vicinity of the Lake of Woods. They are the favored home of the American moose, and the hope of obtaining some specimens of this animal for the museum of the University of Kansas led Professor L. L. Dyche of that institution to traverse these dangerous marshes. Professor Dyche has recently returned after remaining for over three months in the very centre of the swamps, camping upon the occasional sand ridges which cross the region; and to him I am indebted for specimens of a new HŒmatobia.
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