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Carotid endarterectomy has been done for 35 years but remains a contentious operation. Patients who have experienced transitory partial blindness or brief weakness in a limb may undergo the operation [...]

OVERVIEW The integration of low-k dielectric materials has proven to be a significant challenge for semiconductor manufacturers. Progress has been made, though, in etching materials. Results with a variety of […]

Did Jeopardy or your Roundup section (see 'The Kid in Jeopardy' on P. 11 of the February 2013 issue of Wild West) err in calling Mark Lee Gardner's book To [...]

An integrated wearable 3-D printable microfluidic pump was developed, which uses a novel actuation process. Fused deposition manufacture 3-D printing was used as a means to accurately produce this device. This resulted in the fabrication of high precision integrated parts made from poly-lactic-acid bioplastic. By integrating an electro-magnetically actuated closed diffuser nozzle pump configuration a micro-fabricated microfluidic pump has been produced. Biofluids have been driven through the device by actuating a composite polydimethylsiloxane diaphragm actuated polymeric microstructure diaphragm membrane using electromagnetic force. This composite diaphragm was made by suspending 10μm iron particles in the polydimethylsiloxane at concentrations of 30%, 40% and 50%. It is shown that this device acts as an effective electromagnetic force actuated a pump. It is successfully demonstrated that a square wave electromagnetic signal is effective for generating a 2.2μL/min flow rate of biofluid. The integration of 3D printed devices to form a micropump is proven through practical testing which demonstrate a controllable flow rate was generated.

► The mechanisms behind the formation of notch cavities during the AWJ cutting process are understood. ► The mechanisms notion that connect surface and internal features have been further developed. ► The effect of the AWJ jet on the microstructural properties of steel has been established.

Background:Haemodialysis may cause neurological symptoms ranging from inconvenient feelings of disequilibrium to life-threatening neurological complications. There are animal data to suggest cerebral swelling may accompany haemodialysis and contribute symptomatically to dialysis disequilibrium. However, MR images acquired following haemodialysis often fail to demonstrate evidence of cerebral oedema. We wished to quantify any potential cerebral volume change which is caused by haemodialysis treatment. Method:Five renal patients and 5 control subjects had a two volumetric T1-weighted MRI scans on the same day. The patients were imaged immediately before and after haemodialysis. None were taking steroids. Precise positional matching (registration) was used to quantify cerebral volume change. Results:Patients had an increase in cerebral volume following dialysis which averaged 32.8 ml (SE 7.4 ml, 3% brain volume). The change in the controls was 1.4 ml (SE 0.6 ml), p < 0.001. No patient had significant neurological symptoms. Conclusion:Cerebral oedema developed in the patients following dialysis. There is a good biological model for these observations. Modifications to dialysis may help. Common problems which increase cerebral volume, e.g. acute stroke, require careful appraisal in these patients. These observations need consideration when quantifying atrophy in dialysis patients.

Composite laminates are engineered to exhibit tendencies toward gradual (or progressive) failure as opposed to the less desirable catastrophic failure. Localized fail ures begin to occur early in the loading history of a laminate, but due to the laminate's abil ity to redistribute its load internally, the laminate as a whole remains unfailed and contin ues to perform its load-carrying function. In trying to model laminate failure, it is important to recognize the progressive nature of the failure process in order to obtain a correct strength prediction. Localized failures can generally be categorized into various modes: transverse matrix cracking (through-the-thickness cracks running parallel to the fiber direction), periodic matrix cracks (cracks running perpendicular to the fiber direc tion and bridged by the fibers), fiber failure (cracking or splitting), and delamination. The onset of transverse matrix cracking has been found to be a key occurrence in the laminate failure process, and as a result much research has been devoted to its modeling. Con tinuum damage models as well as many shear-lag approaches have been proposed for ana lyzing cross-ply laminates. In this paper, we extend the shear-lag analysis for modeling transverse matrix cracking to a general symmetric multilayer system. The elasticity prob lem for the region of the laminate between two parallel matrix cracks having a general off- axis orientation is set up from equilibrium considerations in terms of the average (through- the-thickness) stresses and solved using the generalized shear-lag relation and the appropriate boundary conditions. This model is then included in a computer program designed for probabilistic laminate analysis, and the results are compared to those deter mined using the ply drop-off technique.

The nuclei of apoptotic thymocytes can be identified by flow cytometry as a subpopulation exhibiting reduced DNA content. We observed that rat thymocyte cultures exposed to 1.0-2.5 μM tri-n-butyltin methoxide (TBT) exhibited a rapid time- and concentration-dependent induction of apoptosis, with > 85% of cells exhibiting reduced DNA content within 1 hr after exposure to 2.0-2.5 μM TBT. In contrast, exposure to 1.0 μM dexamethasone phosphate (DEX) resulted in a gradual time-dependent increase to ∼45% induction of apoptosis by 6 hr versus ∼15% spontaneous induction in controls. However, simultaneous exposure to TBT and DEX resulted in a decreased response: although TBT concentrations between 0.1 and 0.5 μM did not induce apoptosis, they reduced the ability of DEX to initiate apoptosis; while at TBT concentrations ≥ 1.0 μM, simultaneous exposure to DEX substantially decreased the extent of TBT-induced apoptosis and cytotoxicity. Furthermore, while treatment with the protein synthesis inhibitor cycloheximide or the protein kinase C inhibitor H-7 completely blocked DEX-induced apoptosis, neither significantly reduced induction of apoptosis by TBT. Taken together, the toxicant-specific differences in the timing and extent of apoptotic induction and the dissimilar responses to CHX and H-7 suggest that TBT and DEX initiate endonuclease-mediated apoptotic cell death through different mechanisms. Moreover, the ability of each agent to retard the action of the other suggests that these mechanisms are directly or indirectly antagonistic.

The time course and extent of methylation of 1 μM arsenite (iAsIII), arsenate (iAsV), methylarsenite (MeAsIII), methylarsenate (MeAsV), and MeAsIII-diglutathione complex (MeAsIII(GS)2) were examined in an in vitroassay system that contained rat liver cytosol. Precursor arsenicals and methylated metabolites were analyzed by thin-layer chromatography (TLC) or by hydride generation-atomic absorption spectrophotometry (HG-AAS). More than 90% of iAsIIIwas converted to a dimethylated species (Me2As) during a 90-min incubation at 37°C; the amount of monomethylated metabolite was maximal at 15 min. In contrast, only 40% of iAsVwas dimethylated during a 90-min incubation. Comparison of the yields of methylated species in the whole in vitroassay system as determined by HG-AAS and in an ultrafiltrate prepared from the in vitroassay system as determined by TLC indicated that nearly 70% of the dimethylated metabolite (possibly Me2AsIII) that was produced during a 90-min incubation was bound to proteins (>10 kDa). The percentage of protein-bound arsenic in the assay system incubated at 0°C with trivalent arsenicals was three-to fivefold greater than the binding of corresponding pentavalent species. This indicated that both iAsIIIand trivalent organoarsenicals interact avidly with proteins. Both MeAsIIIprepared by metabisulfte-thiossulfate reduction of MeAsVand a MeAsIII(GS)2were quantitatively converted to Me2As during 90-min incubation. In contrast, only 3% of MeAsVwas dimethylated during this interval. These results suggest that trivalent arsenicals are preferred substrates for methylation reactions and that the reduction of As from pentavalent to trivalent states may be a critical step in the control of the rate of metabolism of As.

Thirty-seven patients with infected total hip replacements, treated by either exchange hip replacement with antibiotic loaded acrylic cement, or excision arthroplasty, were assessed after an average of five years. Recurrence of infection was comparable in both groups but exchange arthoplasty gave superior functional results. The success of exchange arthroplasty in the hands of general orthopaedic surgeons was similar to that of tertiary referral centres specialising in hip surgery. When technically possible, exchange seems to be preferable to excision arthroplasty in infected hip replacement.

A 3He sandwich spectrometer incorporating two semiconductor detectors and a proportional counter region has been designed and constructed to perform high resolution measurements of neutron energy spectra in the energy range 100 keV to 15 MeV. The efficiency of the spectrometer was determined experimentally, using a 252Cf spontaneous fission source, in the low-scatter facility of the National Physical Laboratory. The Monte Carlo technique was also used to determine the efficiency and these calculated values were used to extrapolate the measured efficiency to higher energies. The neutron energy spectra from two different sized AmBe neutron sources and an AmB neutron source were measured. Although these spectra have been measured previously, the present work represents an improvement in the energy resolution and extends the energy range. Average values for dose equivalent quantities for neutrons from these sources are also presented. The spectral data is available from the authors, as a printed table or on a computer diskette, on request.

The hydrolysis of 3 distinct substrates by cathepsin E from human red blood cells and gastric mucosa was measured in the presence and absence of physiologically relevant concentrations of ATP. At pH values below about 5.0, the nucleotide was without effect. However, at pH 5.8, whereas cathepsin E was virtually inactive by itself, it was restored to full activity (kcat) by ATP and the non-hydrolysable methylene-ATP analogue. At still higher pH values, kcatprogressively diminished but significant levels of cathepsin E activity were readily detectable at pH 7.0. The specificity of this stabilisation effect was examined.

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The nuclear factor of activated T cells (NFAT) is a transcription factor complex involved in the activation of cytokines and cell surface molecules associated with coordinating the actions of different cells required for an immune response. Two different genes have recently been cloned that encode proteins capable of functioning as the pre-existing (p) and cytosolic (c) component of the NFAT transcription complex, NFATc of human and NFATp of murine origin (Northrop et al., 1994; McCaffrey et al., 1993b). We report here the partial cDNA cloning of the murine homolog of NFATc and the human homolog of NFATp, and the chromosomal localization of both genes in both species to conserved syntenic regions. Through the use of mapping panels of human × Chinese hamster and mouse × rodent cells hybrids, the NFATc genes were mapped to human and mouse chromosomes 18. By analyzing a chromosome 18 radiation hybrid panel, the human NFATc gene was localized to the q terminus, closely linked to STS marker D18S497. The murine Nfatc gene was sublocalized to chromosome band 18E4 by FISH. The NFATp genes were mapped by somatic cell hybrid analysis to human chromosome 20 and mouse chromosome 2. Human NFATp was assigned to chromosome region 20ql3.2→ql3.3 by FISH. Based on the conserved syntenic region on human chromosome 20 and mouse chromosome 2, murine Nfatp is predicted to reside in the vicinity of a mutant locus wasted. Homozygous wst/wst mice display a phenotype reminiscent of severe combined immune deficiency or ataxia telangiectasia, disorders that could therefore be considered candidates for NFATp mutations.

Cerebral blood-flow (C.B.F.) was measured in 38 patients with hæmatocrit values (Hct) in the range 0·47-0·53 and was found to be significantly lower than in 43 patients with Hct in a lower range (0·36-0·46). After reduction of Hct in the higher Hct group by venesection, flow increased by a mean of 50%. This improvement in flow was largely due to a reduction in viscosity. Hct around the generally accepted upper limit of normal may be an important factor in the causation of occlusive vascular disease.

Patients with high-normal or above-normal hæmatocrit were found to have impaired alertness when compared with a control group matched for age and occupation. On retesting the controls had improved alertness scores attributable to a practice effect; but the patients, when retested after reduction of hæmatocrit by venesection, had improved significantly more than the controls. Improvement in alertness correlated very well with the increase in cerebral blood flow which followed venesection. Levels of venous hæmatocrit that are generally accepted as normal may not necessarily be optimum.

Two patients are described with an organic brain syndrome thought to be due to bismuth (Bi) absorbed from a skin cream. Both patients had intellectual impairment and memory loss punctuated by periods of confusion, tremulousness, clumsiness, difficulty in walking, and myoclonic jerks. A similar clinical picture has been reported from Australia and France in patients taking insoluble bismuth salts by mouth. Bi was found in cerebral venous blood in both patients and in the cerebrospinal fluid in one. It is suggested that bismuth can cross the blood/brain barrier and disturb oxidative cerebral metabolism, because increased lactate production was found with decreased consumption of oxygen and glucose and lowered cerebral blood-flow.

SummaryThe ice pack test may be helpful in establishing that ptosis is due to ocular myasthenia gravis, since cold improves neuromuscular transmission. However, the role of the test in determining whether diplopia is of myasthenic origin has yet to be established.

A review is presented of the technical feasibility and/or the availability of active neutron personal dosemeters, and the potential for development of such a dosemeter. The review consists of four parts. The first part is an introduction which considers the operational needs for an active neutron personal dosemeter. There does appear to be a need for an electronic neutron personal dosemeter, although it is not established that the demand for such a device is great. The relative magnitude of photon and neutron doses and dose rates in the nuclear industry has changed owing to the increased shielding of the photon component. Changes in fuel burnup and new fuel types have increased neutron exposure. Work on plant refurbishment of decommissioning will also increase neutron dose rates, and for these workplaces there may be sudden dose rate fluctuations in space or time. However, in the UK in 1996 for example, of 12,000 classified workers monitored for neutrons, there were only 100 recorded neutron doses of greater than 1 mSv. In the second part, the physics of personal neutron dosemeters is outlined and summaries are given of detection techniques. It is clear that the development of a practical electronic neutron dosemeter is difficult. Effort has been devoted by many research and development groups over several decades without complete success. The basic difficulty is the requirement to measure very small depositions of energy from neutron radiation which have to be recognised in the presence of photon and electron radiation. This basic difficulty is compounded by the present need to determine lower doses than hitherto. Brief summaries are given of techniques which are being applied to the development of an active neutron personal dosemeter, or are thought to be possible options for the future. The techniques considered are: low pressure (tissue-equivalent) proportional counters, thin semiconductors with event size analysis; two diode devices; multi-diode 'spectrometers'; detector arrays such as charge coupled detector devices; 6Li or 10B sandwich spectrometers; radfets (field effect transistors); direct ion storage devices; memory devices; organic semiconductors; light pipes; GM tubes; organic films; advanced gas detectors; advanced silicon devices; and bubble detectors. Published papers up to mid-1998 have been considered. The third part summarises the performance and metrological requirements which have been proposed for neutron dosemeters by national and international standards and/or regulatory authorities. The fourth part of the review draws conclusions and suggests future action. Of devices presently being studied, it is considered that the more likely candidates for a successful outcome are, in the short term, direct ion storage or bubble detectors, and in the longer term, charge coupled detectors, memory devices or optical fibres.

In a joint PTB/NPL/GSF experimental programme the responses of four sets of Bonner Spheres were determined experimentally using monoenergetic neutrons in the range from 8 keV to 2.5 MeV. The measurements showed effects which can be understood qualitatively, but there are discrepancies with calculated values. It is questionable if these discrepancies can be explained by differences in the polyethylene density and detector characteristics employed in this experiment and those assumed in the calculations.

Measurements of the energy spectra and angle distributions have been carried out at five locations in a fuel reprocessing installation and at two locations at a Magnox reactor. The energy spectral distributions were determined using multispheres with either passive or active thermal neutron detection. Directional information was derived from the response of personal dosemeters mounted on phantoms. These evaluations enabled the estimation for the seven locations of the energy and angle weighted values of HE,H'(10) and personal dosemeter response, as well as of the isotropic quantity H*(10) and of the responses of NM2 and 0949 type rem meters. The results are analysed and discussed in terms of the relationships between primary and operational quantities, and between primary quantities and instrument and dosemeter responses. It is concluded that, in general, the operational quantity HP(10) will give a reasonable estimate of HE, and that a PADC etched track personal dosemeter measuring thermal, epithermal and fast neutrons is suitable for use in the neutron radiation fields surveyed. Some estimates of the proposed new quantity, effective dose, are included.

A Bonner sphere spectrometry system and a microdosimetric counter have been used to make measurements in the fields from three different neutron sources located in the working environment of a neutron source fabrication plant. Both the neutron spectra and the corresponding microdosimetric spectra are presented, quality factors are derived, and the measured dose equivalent values are compared with results from two different area survey instruments.

The spectral fluence response of practicable neutron dosemeters for routine use generally does not match the spectral fluence response of radiation protection quantities such as the ambient dose equivalent H*(10). A knowledge of the prevalent spectral fluence is required to provide appropriate calibration factors for operational dosemeters. A program package was developed which assists the collection, archiving and interpretation of neutron spectra relevant for working environments. The features of this program package are briefly outlined and examples for dosimetric applications are given.

Continuing a joint PTB/NPL/GSF programme, the experimental determination of the responses of four sets of Bonner sphere has been extended to twelve monoenergetic neutron energies in the range from 1.17 keV to 14.8 MeV. Comparison of the measured responses with calculated ones revealed significant discrepancies. A renormalisation of the calculated responses by factors which strongly depend on the sphere diameter was necessary in order to fit the experimental data.

This paper discusses the effects of changing from the old to new (ICRP 60 and ICRU 47) dosimetric quantities, and the relationship between quantities, as a function of the energy and angular distribution, for practical radiation fields. It considers: X rays, gamma rays, neutrons and beta rays; reviews the limited data on practical energy and angular distributions for photons and neutrons in the workplace; and calculates relevant dosimetric quantities based on realistic assumptions. The results are used to illustrate how the relationship between quantities might vary in practical fields and to draw conclusions about the implications of recent ICRP and ICRU publications.

In order to provide quantitative information on the quality of fast neutron dosimetry services in the UK, the NPL has carried out a performance test of these services. A summary is given of the dosemeters tested, and the irradiation methods are described. Neutrons from both an 241Am-Be and a 252Cf source were used to deliver dose equivalents in the range 0.5 mSv to 170 mSv. The data have been analysed in terms of the bias and standard deviation in the ratios of reported to reference dose equivalent. There was a tendency for dosemeters to over-respond at the lower dose equivalent values and under-respond at higher values. The spread in individual readings was high for the lowest dose equivalents, but decreased as the dose equivalent became larger.

An intercomparison of computer calculations to determine the response function of a multisphere neutron spectrometry system has been undertaken by EURADOS-CENDOS Working Committee IV. For this purpose, a standard multisphere spectrometer was adopted. This consisted of four polyethylene spheres, radii 38.1, 63.5, 101.6 and 152.4 mm with a central 3He detector, diameter 32 mm, having an atomic density of 4.25 x 1019 atoms.cm-3 (pressure, 172 kPa). The calculations were made for two polyethylene densities (0.92 and 0.95 g.cm-3). The Monte Carlo computer codes MCNP and BOKU (developed at PTB specifically for these calculations) and the discrete ordinates code ANISN were used to calculate the response of the detector for a variety of monoenergetic incident neutrons. Preliminary results for the 38.1 and 63.5 mm radii spheres are presented to compare these codes and their application at different laboratories. Discrepancies are discussed. In addition, further calculations were undertaken to compare the effects of various factors on the response functions, including: the effect of using cross sections without taking into account the binding of the carbon and hydrogen in the polyethylene; the effect of the steel walls of the 3He detector; and the effect of the stem of the counter.

Continuing a joint PTB/NPL/GSF programme the experimental determination of the responses of four Bonner sphere sets has been extended into the thermal neutron region. The results are presented and compared with calculated responses where available. The results highlight the importance of experimentally validating Bonner sphere response function calculations wherever possible.

The International Organisation for Standardisation (ISO) TC85/SC2/WG2 has convened a working group to develop a standard dealing with the production, characterisation and use of reference neutron radiation fields simulating those found in the workplace. This standard is being developed to provide guidance to the laboratories developing simulated practical reference neutron fields, and to the users of these fields. The ISO currently recommends four reference neutron spectra for the calibration of radiation protection instruments and dosemeters. However, due to the energy dependence in the dose equivalent responses of these devices, it is useful to develop additional neutron spectra for calibration purposes. This standard will describe the methods of production and the expected characteristics of simulated practical neutron fields. The types of facilities considered include those using radionuclide neutron sources, accelerators and reactors. Facilities producing high energy neutrons for the calibration of instruments, and dosemeters used at accelerator laboratories and in aircraft for in-flight monitoring are also considered. The status of this standard is being presented now in order to provide a progress report and to elicit comments and suggestions before the standard is finalised.

Eurados Working Group 7 recently organised a large-scale comparison of neutron spectrometry and dosimetry measurements at the IPSN/SDOS laboratory of the CEA Cadarache Research Centre in France. A large number of participants took part with a range of instruments including spectrometers, tissue-equivalent proportional counters, personal dosemeters, and survey instruments. The neutron field used for the exercise was a primarily low energy neutron spectrum similar to those which have been measured recently around nuclear facilities. This paper presents the results of the measurements and attempts to draw conclusions about the accuracy attainable with the various devices, their advantages drawbacks, and potential problems.

The response of practicable neutron dosemeters for routine use generally does not match the conversion function from fluence for radiation protection quantities such as the ambient dose equivalent. As a consequence, significant errors may be encountered when monitoring in a neutron energy spectrum different from that in which the dosemeter was calibrated, which is almost inevitably the case. A database of neutron energy spectra, detector response functions, and dosimetric conversion factors has been developed, and has been used to investigate the extent of this problem. The paper examines various ways of improving dosemeter response by 'ranking' spectra and deriving correction factors based upon this ordering. In this case of area monitoring, a combination of two responses (e.g. a rem meter and TEPC) may serve to improve the measurement of dose equivalent.

A Monte Carlo facility has been developed for modelling the response of semiconductor devices to mixed neutron-photon fields. This utilises the code MCNP for neutron and photon transport and a new code, STRUGGLE, which has been developed to model the secondary charged particle transport. It is thus possible to predict the pulse height distribution expected from prototype electronic personal detectors, given the detector efficiency factor. Initial calculations have been performed on a simple passivated implanted planar silicon detector. This device has also been irradiated in neutron, gamma and X ray fields to verify the accuracy of the predictions. Good agreement was found between experiment and calculation.