bluuebunny/crossref_metadata_2025 huggingface dataset:
Causes of re-recurrence after polytetrafluoroethylene patch saphenoplasty for recurrent varicose veins
Authors: Bhatti T S , Whitman B , Harradine K , Cooke S G , Heather B P , Earnshaw J J
Published: July 2002

Background

The aim of this study was to determine whether a polytetrafluoroethylene (PTFE) patch sutured over the religated saphenofemoral junction could reduce the rate of recurrence after operation for recurrent varicose veins.

Methods

Fifty patients who had surgery for recurrent long saphenous incompetence (81 legs had a small PTFE patch sutured over the religated saphenofemoral junction. There were no major complications following surgery. Three patients had a wound infection or delayed healing. All patients were invited for clinical examination and duplex imaging at a median of 19 (range 6–39) months after operation.

Results

Some 38 of 43 patients (70 legs) remained satisfied with the results of surgery; 16 (23 per cent) of 70 legs had visible veins on inspection and eight of these (11 per cent) involved symptomatic recurrence. Duplex imaging showed that recurrence was due to saphenofemoral junction incompetence in ten legs; two appeared to have a major groin connection but the other eight appeared to have neovascularization. Other causes were thigh perforator reflux (three legs) and cross-groin collaterals (three). Eleven of the 16 legs with recurrence had varicography but in two the procedure was a technical failure. Two legs had evidence of a significant connection (more than 3 mm) and two a minor connection (less than 3 mm) to the femoral vein at the level of the PTFE patch, but in the remainder recurrence was due to upper thigh perforating veins. There was good concordance between duplex imaging and varicography.

Conclusion

PTFE patch saphenoplasty appears to be safe. Although these are early results, the technique seems potentially as effective as other barrier methods that have been investigated; in ten legs (12 per cent) recurrence was attributed to failure at the level of the PTFE patch.
Randomized clinical trial of sutured versus stapled closed haemorrhoidectomy
Authors: Khalil K H , O'Bichere A , Sellu D
Published: July 2002

Background

Stapled haemorrhoidectomy does not involve dissection, with its attendant potential morbidity, required to perform closed haemorrhoidectomy. This study compared haemorrhoidectomy with (sutured) and without (stapled) preliminary dissection.

Methods

Forty patients with prolapsed symptomatic haemorrhoids were randomly assigned to sutured (n = 20) or stapled (n = 20) haemorrhoidectomy. Preoperative assessment was by proctoscopy, sigmoidoscopy and anal manometry. Stapled and diathermy haemorrhoidectomies with wound suture were performed, and excised tissue was examined histologically. Pain scores, complications, wound healing and patient satisfaction were recorded. Follow-up was weekly for 4 weeks, and at 3 and 6 months; anal manometry was repeated at the last two visits.

Results

Postoperative resting and squeeze pressures were reduced by the stapled method at 3 months (P = 0·02 and P = 0·03 respectively), returning to baseline by 6 months. Stapled haemorrhoidectomy was quicker but initial access into the anus was hampered by the bulky stapler. Isolated muscle fibres were identified equally in both groups, but incontinence did not occur. The stapled technique resulted in less postoperative pain (P = 0·04), a greater degree of satisfaction (P = 0·01) and faster wound healing (P < 0·001), but was more expensive. There was no significant difference in complications.

Conclusion

Despite the higher cost and difficult access, stapled haemorhoidectomy results in less postoperative pain, faster wound healing and greater patient satisfaction than the sutured technique.
Short-term results of femoropopliteal subintimal angioplasty
Authors: McCarthy R J , Neary W , Roobottom C , Tottle A , Ashley S
Published: July 2002

Background

Subintimal angioplasty may be more successful than conventional (intraluminal) angioplasty for treatment of long femoropopliteal occlusions. This study assessed the clinical and haemodynamic outcome of subintimal angioplasty.

Methods

All patients with femoropopliteal occlusions treated by subintimal angioplasty over a 3-year period at two centres were reviewed. Clinical assessment and colour duplex imaging were carried out.

Results

Sixty-nine procedures were performed in 33 men and 33 women of median age 74 (range 47–92) years. Indications for treatment were intermittent claudication in 26 (38 per cent) and critical limb ischaemia in 43 (62 per cent). Median occlusion length was 10 (range 2–50) cm. Primary technical success was achieved in 51 occlusions (74 per cent). There were 11 complications (16 per cent); the majority were minor but surgical intervention was required in two patients (3 per cent). At 6 months the cumulative symptomatic and haemodynamic primary patency rates were 60 and 51 per cent respectively, analysed on an intention-to-treat basis. The symptomatic and haemodynamic patency rates for technically successful procedures were 80 and 77 per cent respectively.

Conclusion

In this series the short-term clinical success of subintimal angioplasty was poor because of a high incidence of reocclusion and restenosis, despite a relatively high initial technical success rate.
Chronic dysphagia following laparoscopic fundoplication
Authors: Bessell J R , Finch R , Gotley D C , Smithers B M , Nathanson L , Menzies B
Published: July 2002

Background

Many surgeons practise tailored laparoscopic antireflux surgery in an attempt to prevent postoperative dysphagia. The aim of this study was to determine the effect of 360° fundoplication (Nissen) or 270° fundoplication (Toupet), and the influence of abnormal oesophageal peristalsis, upon postoperative dysphagia.

Methods

This was a cohort study from three tertiary referral centres, using dysphagia before laparoscopic fundoplication and 1 year after operation as the main outcome variable. Preoperative oesophageal manometry was performed on all patients.

Results

Some 761 patients underwent Nissen and 85 underwent Toupet fundoplication. Only 2 per cent reported severe postoperative dysphagia. There was a significant selection bias towards the Toupet operation for patients with abnormal oesophageal motility (P < 0·001). For patients whose oesophageal manometric findings were normal there was a significant improvement in dysphagia after Nissen fundoplication (P = 0·02), and no significant change following Toupet fundoplication. There was no significant change in the rate of dysphagia following either method of fundoplication amongst other subgroups in which oesophageal manometry was stratified as non-specific motor disorder, low-amplitude peristalsis, or aperistalsis.

Conclusion

A tailored approach to the degree of fundoplication is unnecessary as patients with dysmotility suffer no more dysphagia after full laparoscopic Nissen fundoplication than those who have a partial Toupet wrap.
Cost–utility analysis of open versus laparoscopic groin hernia repair: results from a multicentre randomized clinical trial
Authors:   Medical Research Council Laparoscopic Groin Hernia Trial Group, McIntosh E
Published: July 2002

Background

This study was a pragmatic economic evaluation carried out alongside a multicentre randomized controlled trial comparing laparoscopic with open groin hernia repair. The primary economic evaluation framework employed was a cost–utility analysis.

Methods

At 26 hospitals in the UK and Ireland, 928 patients with a groin hernia were assigned randomly to laparoscopic or open repair. Cost data were identified and measured both within and outwith the trial. Cost data were combined with quality-adjusted life years (QALYs) from the EQ-5D questionnaire to obtain cost-per-QALY ratios.

Results

The mean cost of laparoscopic hernia repair was £1112·64, compared with £788·79 for the open operation. The extra cost of £323·85 in the laparoscopic group was mainly due to additional theatre time and increased equipment and sterilization costs. The estimated incremental cost per QALY of the laparoscopic over the open method was £55 548·00 (95 per cent confidence interval £47 216·00–£63 885·00).

Conclusion

While the results show that a high cost was incurred to produce an additional QALY by using laparoscopic over open hernia repair, sensitivity analyses show that there are specific situations in which laparoscopic repair may be a viable alternative, such as when reusable equipment is employed.
The effects of nymphaeid (Nuphar lutea) density and predation by perch (Perca fluviatilis) on the zooplankton communities in a shallow lake
Authors: MOSS Brian ,   RYSZARD KORNIJOW,   And G. J. MEASEY
Published: July 2002

1. The effects of addition of juvenile perch (Perca fluviatilis) on the microcrustacean and rotifer communities associated with nymphaeid beds were studied, at three different plant densities [high (normal), medium (reduced by a half) and low (reduced to a third of normal)], in eighteen 2 m × 1 m enclosures in a shallow lake.

2. At the low and medium densities of lilies, Daphnia densities were high in the absence of perch but very low in the presence of perch. They increased, even in the presence of perch, to high densities (comparable with those in the absence of perch) at the highest plant density. Body sizes of Daphnia hyalina were consistent with high predation by perch at low and medium plant densities but reduced predation at high plant densities. Patterns of chlorophyll a concentration, in the presence of perch, inversely reflected those of D. hyalina density.

3. At naturally high densities but not at reduced densities, the plants appeared to act as refuges against predation for the Daphnia. Reductions in oxygen concentrations in the plant beds were not responsible for the refuge effect, nor could there be avoidance of the beds by the fish. The mechanism of the refuge effect must therefore lie in frustration of the process of capture of the Daphnia by the fish.

4. Numbers of other small Crustacea and rotifers were mostly unaffected by fish predation. Numbers of Asplanchna sp., Chydorus sphaericus and copepodites were higher in the presence of fish and, although there was no main effect of fish on numbers of Diaphanosoma brachyurum, there was a plant–fish interaction, with this species being less abundant in the presence of fish at low plant densities but more abundant in the presence of fish at medium and high plant densities. Main effects of plants were few, with only Asplanchna sp. and Keratella sp. decreasing in numbers with increasing plant density. Most taxa changed in numbers with time but interaction effects between time and plants, and fish and plants, were few.
A method for the estimation of the global population sizes of plant species – the Area‐abundance‐index
Authors: Hoffmann Matthias H. , Welk Erik
Published: July 2002

The aim of this study is to establish a practical index that considers both the size of the global range, and the mean relative abundance of species within their range. Detailed general distribution maps provide the basis for a classification of ranges into nine size categories. The abundance data are arranged into five categories, ranging from very rare to very common. These categories are derived directly from floristic literature. The Area‐abundance‐index is calculated using an empirical formula, i.e. by the addition of the mean relative global abundance and the range size category number. Values of the index range from 2 (very rare and range ≤10 km2) to 13 (very common throughout and range > 107 km2). The main advantage of the index is that species become comparable in terms of their global population sizes. Frequently, regional Red Lists contain species that are common elsewhere and occupy wide areas, or may not include locally abundant species that occupy only very small geographical ranges. The application of the Area‐abundance‐index for the prioritizing of species within Red List categories and, hence, a varying assignment of conservational efforts, is discussed. Furthermore, the application of the index on a local scale, and the regional responsibility for species conservation or monitoring are discussed.
Measuring the Quality of Supervision and the Training Experience in Psychiatry
Authors: Clarke David M.
Published: July 2002

Objective: The aim of this study was to develop and trial a method of trainee evaluation of the supervision and training experience.

Method: A questionnaire was developed and applied at the end of each of four 6-month clinical rotations.

Results: The evaluation demonstrated areas of strength (punctuality and reliability, encouragement, educational value, clinical guidance) and weakness (journal club, clinical meetings). Many supervisors were not observing diagnostic or management interviews of trainees. Psychotherapy supervision received the highest ratings.

Conclusions: Because of the privacy of supervision and the occasional nature of evaluations, reliability of scores cannot be demonstrated. However, within the context of a model of quality improvement, and supplemented by the education and supervision of supervisors, trainee evaluations can be useful in targeting specific areas of deficiency in training and supervision.
Classifications in Psychiatry: A Conceptual History
Authors: Berrios German E.
Published: July 2002

Background: Historical accounts of psychiatric classifications have hitherto been written in terms of a ‘received view’. This contains two assumptions, that: (i) the activity of classifying is inherent to the human mind; and (ii) psychiatric ‘phenomena’ are stable natural objects.

Objectives: The aim of this article is to provide an outline of the evolution of psychiatric classifications from the perspective of conceptual history. This is defined as a theoretical and empirical inquiry into the principles, sortal techniques and contexts in which alienists carried out their task. It assumes that all psychiatric classifications are cultural products, and endeavours to answer the question of whether classificatory models imported from the natural sciences can be applied to man-made constructs (such as mental illness) definitionally based on ‘personalised semantics’. Methods: Exemplars of classificatory activity are first mapped and contextualised. Then, it is suggested that in each historical period crafting classifications has been like playing a game of chess with each move being governed by rules. This is illustrated by offering an analysis of the 1860–1861 French debate on classification. Results and Conclusions: (1) Medicine is not a contemplative but a modificatory activity and hence classifications are only valuable if they can release new information about the object classified. (2) It should not be inferred from the fact that psychiatric classifications are not working well (i.e. that they only behave as actuarial devices) that they must be given up. Conceptual work needs to continue to identify ‘invariants’ (i.e. stable elements that anchor classifications to ‘nature’. (3) Because mental disorders are more than unstable behavioural epiphenomena wrapped around stable molecular changes, ‘neurobiological’ invariants may not do. Stability depends upon time frames. Furthermore, it is unlikely that gene-based classifications will ever be considered as classifications of mental disorders. For once, they would have low predictive power because of their lack of information about the defining codes of mental illness. ‘Social’ and ‘psychological’ invariants have problems of their own.
Brain Imaging Technologies: How, What, When and Why?
Authors: Gordon Evian
Published: July 2002

Objective: Innovations in physics and computing technology over the past two decades have provided a powerful means of exploring the overall structure and function of the brain using a range of computerised brain imaging technologies (BITs). These technologies offer the means to elucidate the patterns of pathophysiology underlying mental illness. The aim of this paper is to explore the current status and some of the future directions in the application of BITs to psychiatry.

Method: Brain imaging technologies provide unambiguous measures of brain structure (computerised tomography and magnetic resonance imaging [MRI]) and also index complementary measures of when (electroencephalography, event related potentials, magnetoencephalography) and where (functional MRI, single photon emission computed tomography, positron emission tomography) aspects of brain activity occur.

Results: The structural technologies are primarily used to exclude a biological cause in cases of a suspected psychiatric disorder. The functional technologies show considerable potential to delineate subgroups of patients (that may have different treatment outcomes), and evaluate objectively the effects of treatment on the brain as a system. What is seldom emphasised in the literature are the numerous inconsistencies, the lack of specificity of findings and the simplistic interpretation of much of the data.

Conclusion: Brain imaging technologies show considerable utility, but we are barely scratching the surface of this potential. Simplistic over-interpretation of results can be minimised by: replication of BIT findings, judicious combination of complementary methodologies, use of appropriate activation tasks, analysis with respect to large normative databases, control for performance, examining the data ‘beyond averaging’, delineating clinical subtypes, exploring the severity of symptoms, specificity of findings and effects of treatment in the same patients. The technological innovation of BITs still far outstrips the sophistication of their use; it is essential that the meaning and mechanisms underlying BITmeasures are always evaluated with respect to prevailing models of brain function across disciplines.
Hubris and Humility in the Life of the Schizophrenia Researcher
Authors: Copolov David
Published: July 2002

Objective: The goal of this paper is to provide a personal view of the challenges and satisfactions associated with schizophrenia research in the late 1990s.

Method: Consideration is given to the successes and frustrations associated with several important discoveries relevant to psychiatry in the context of personal reflections on the ‘maturity’ of schizophrenia research as a field of scientific endeavour.

Conclusion: Schizophrenia research provides many opportunities for its practitioners to experience and exercise their modesty. Despite impressive advances in the disciplines which are germane to it, our field is, for example, still far from identifying specific aetiological factors which operate in even a substantial minority of our patients. Historical examples illustrate how important it may be to maintain an attitude of single-mindedness, especially in the early phases of research in which seemingly bold but ultimately correct conjectures are unaccompanied by data that are sufficiently compelling to convince the wider scientific community. Considerable hubris is required in order to believe that one's conjectures are likely to be as correct as those that have led to substantive advances in our field.
Reflections on the College by the Recipient of the 1999 College Medal of Honour
Authors: Lawrence Joan AM
Published: July 2002

The award of the College Medal of Honour is a source of immense pride and satisfaction to me. That I am the first woman, and only the fourth person, to receive the medal adds a special significance to the award.
A randomized, double‐blind, placebo‐controlled study of itraconazole capsules for the prevention of deep fungal infections in immunodeficient patients with HIV infection
Authors: Smith DE , Bell J , Johnson M , Youle M , Gazzard B , Tchamouroff S , Frechette G , Schlech W , Miller S , Spencer D , Seifert W , Peeters M , De Beule K ,   for the Itraconazole Prophylaxis Study Group
Published: July 2002

Objectives  To determine whether systemic or deep fungal infections can be prevented, a double‐blind, placebo‐controlled, phase III trial of itraconazole prophylaxis was undertaken in HIV‐infected patients.

Methods  HIV‐1 infected patients with CD4 counts < 300 cells/μL were treated with itraconazole (200 mg per day) or matching placebo and followed for 2 years. Development of deep fungal infections, episodes of mucocutaneous candidiasis, change in CD4 count, survival and safety data were collected at each study visit.

Results  Three hundred and seventy‐four patients received study medication, 187 were given itraconazole and 187 matching placebo. Time to development of deep fungal infection did not differ between groups, in an intention to treat analysis. Low CD4 cell count and prior use of Pneumocystis carinii pneumonia (PCP) prophylaxis were significantly associated with a more rapid development of deep fungal infection (P = 0.044 and 0.017, respectively). Itraconazole treatment significantly reduced the incidence of oral candidosis (25% vs. 48% P < 0.001) and time to development of oral candidosis (508 vs. 413 days, P < 0.001) but not the number of deep fungal infections (11 vs. 13). Survival did not differ significantly between groups (nine vs. 14 deaths). CD4 counts decreased significantly over time in both study arms. Adverse events did not differ between groups; 20% vs. 23% stopped study medication due to an adverse experience.

Conclusions  Although itraconazole prophylaxis significantly reduced the number and time to development of oral candidosis, too few episodes of deep fungal infection were noted to determine whether itraconazole prophylaxis was effective for this condition. Chronic itraconazole treatment is well tolerated in HIV‐infected patients with marked immunodeficiency.
ULNAR NEUROPATHY AT ELBOW (UNE): ITALIAN MULTICENTRE STUDY DESIGN AND PRELIMINARY DATA
Authors: Giannini F. , Mondelli M. , Bibbò G. , Padua R. , Padua L. ,   Italian CTS study group
Published: July 2002

The clinical picture of UNE, its relationship with neurophysiological impairment and natural history of the disease are yet undefined. The main objectives of Italian Multicentre Study are: 1) to better assess historical, physical and neurophysiological features using a multiperspective evaluation; 2) to evaluate the sensitivity of an electrodiagnostic protocol in a wide population of patients; 3) to develop a disease‐specific self‐administered questionnaire; 4) to assess the natural time course of clinical and electrophysiological parameters. Case recognition is based on clinical ground: symptoms and/or signs suggestive of ulnar nerve impairment. Personal and clinical data of each patient are properly scheduled with particular regard to duration, trend and anatomic distribution of symptoms, associated diseases, work and hobby related manual activities. A patient‐oriented evaluation is performed through three self‐administered questionnaires: the first one validated for unspecified upper limb diseases, a second validated for CTS and the third, newly proposed, specific for ulnar symptoms. Clinical severity is assessed with a 3‐stage scale proposed by Antoniadis et al. (1997) and a 4‐stage scale proposed by Giannini et al. (2001). Electrophysiological study is performed according to practice recommendations of AAEM/AAN (1999). Although minimal criteria for diagnosis are based on motor ulnar conduction abnormalities across the elbow, other motor and sensory conduction parameters of ulnar, radial and median nerves are measured to correctly detect most common co‐morbidities such as carpal tunnel syndrome. The electrophysiological impairment is quantified using a 5‐step neurophysiological classification proposed by Padua et al. (2001) and a 13‐point global severity score proposed by Mondelli et al. (2000) based on abnormalities of ulnar motor and sensory neural conduction and amplitude and EMG of ulnar‐supplied muscles. Each patient suffering from UNE, neurophysiologically confirmed, will be again assessed by the same protocol at one and six months after the first diagnosis. About 30 centres, widely distributed in the national country and consisting of an EMG‐Lab with proper medical staff and instrumental equipment, have joined the study and are enrolling consecutive UNE cases starting from November 1st, 2001. Data are being collected in Siena centre for statistical analysis.
Laser bilayer etching of GaAs surfaces
Authors: Maki P. A. , Ehrlich D. J.
Published: July 2002

An excimer-laser-stimulated etching technique is described for controlled pulse-by-pulse stripping of molecular bilayers from GaAs surfaces. The process is carried out in a molecular beam epitaxy (MBE) system equipped with an auxiliary low-pressure Cl2 chamber. 193 nm ArF laser light is used to pattern surfaces via projection optical imaging with high processing speed and without exposure to air between etching and MBE steps. A laser stroboscopic method has permitted temporal reaction mapping of the etching mechanisms involved.
Photorefractivity at 1.5 μm in CdTe:V
Authors: Partovi Afshin , Millerd James , Garmire Elsa M. , Ziari Mehrdad , Steier William H. , Trivedi Sudhir B. , Klein Marvin B.
Published: July 2002

We have for the first time demonstrated two-beam coupling energy transfer at a wavelength of 1.5 μm. Beam coupling gain coefficients of 0.6 cm−1 have been obtained in vanadium -doped CdTe with only 5 mW/cm2 incident intensity. These gain coefficients exceed typical gain coefficients in GaAs at 1.06 μm wavelength by 50%. In preliminary measurements using the moving grating technique, we have measured a gain coefficient of 2.4 cm−1. Through adjustment of the doping level, CdTe:V can be used as a sensitive photorefractive material through the 0.9–1.5 μm spectral range.
Hydrolyzation oxidation of AlxGa1−xAs-AlAs-GaAs quantum well heterostructures and superlattices
Authors: Dallesasse J. M. , Holonyak N. , Sugg A. R. , Richard T. A. , El-Zein N.
Published: July 2002

Data are presented on the conversion (selective conversion) of high-composition (AlAs)x(GaAs)1−x layers, e.g., in AlxGa1−xAs-AlAs-GaAs quantum well heterostructures and superlattices (SLs), into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C). Hydrolyzation oxidation of a fine-scale AlAs(LB)-GaAs(Lz) SL (LB +Lz≲100 Å), or random alloy AlxGa1−xAs (x≳0.7), is observed to proceed more slowly and uniformly than a coarse-scale ‘‘alloy’’ such as an AlAs-GaAs superlattice with LB + Lz≳200 Å.
Monte Carlo-fluid hybrid model of the accumulation of dust particles at sheath edges in radio-frequency discharges
Authors: Sommerer Timothy J. , Barnes Michael S. , Keller John H. , McCaughey Michael J. , Kushner Mark J.
Published: July 2002

Particulate contamination (dust) has been observed to accumulate near the sheath-plasma boundary in both radio-frequency (rf) and direct-current (dc) discharges. We have developed and applied a hybrid Monte Carlo-fluid simulation of electron, ion, and charged dust transport in rf discharges to investigate the dynamics of particulate contamination. The processes governing the transport of charged dust in the model are drift of partially shielded particles in the electric field, collisions with the fill gases, and viscous ion drag arising from Coulomb interactions of particles with ions drifting and diffusing in the plasma. We find that negatively charged dust particles accumulate near the sheath-plasma boundary, and that transport of the particles is dominated by ion drag.
Microsecond lifetimes and low interface recombination velocities in moderately doped n-GaAs thin films
Authors: Lush G. B. , Melloch M. R. , Lundstrom M. S. , Levi D. H. , Ahrenkiel R. K. , MacMillan H. F.
Published: July 2002

We have observed lifetimes greater than 1 μs in moderately doped, thin film, n-GaAs/Al0.3Ga0.7As double heterostructure membranes formed by etching away the substrate. We attribute these ultralong lifetimes to enhanced photon recycling caused by the removal of the substrate. Nonradiative recombination in the bulk and at the interfaces is very low; the upper limit of the interface recombination velocity is 25 cm/s. Such long lifetimes in GaAs doped at ND=1.3×1017 cm−3 suggest that thin-film solar cells offer a potential option for achieving very high efficiencies.
Elastic properties of 5-mol % MgO doped LiNbO3 crystals measured by line focus beam acoustic microscopy
Authors: Kushibiki J. , Kobayashi T. , Ishiji H. , Chubachi N.
Published: July 2002

An ultrasonic method of line focus beam (LFB) acoustic microscopy is applied to quantitative characterization of LiNbO3 wafers destined for optical use. Commercial Z-cut wafers obtained from two optical grade LiNbO3 crystals, with and without 5-mol % MgO doping, are evaluated by measuring the leaky surface acoustic wave (LSAW) velocities. Doping of 5-mol % MgO to LiNbO3 results in an increase of about 1% in the LSAW velocities and in a decrease of about 0.1% in density. Fewer elastic inhomogeneities are observed in the undoped wafer than in the MgO doped wafer. The measured LSAW velocities are compared with the chemical and physical properties, chemical composition, density, lattice constant, refractive index, and Curie temperature. It is shown that the LFB system has a much greater sensitivity and resolution in the determination of these properties than do other analytical methods. It is suggested that this method should be adopted as a new analytical technique for establishment of the crystal growth conditions and for evaluation of optical grade LiNbO3 wafers.
Annealing of low-temperature GaAs studied using a variable energy positron beam
Authors: Keeble D. J. , Umlor M. T. , Asoka-Kumar P. , Lynn K. G. , Cooke P. W.
Published: July 2002

The annihilation characteristics of monoenergetic positrons implanted in a molecular beam epitaxy layer of low-temperature (LT) GaAs annealed at temperatures from 300 to 600 °C were measured. A gallium vacancy concentration of approximately 3×1017 cm−3 is inferred for the as-grown material. The S parameter increased significantly upon anneal to 500 °C. The dominant positron traps in samples annealed at and below 400 °C are distinct from those acting for samples annealed to 500 or 600 °C. The change in S parameter for the 600 °C annealed sample compared to the GaAs substrate, SLT,600=1.047Ssub, is consistent with divacancies or larger open volume defects.
Impurity monitoring by laser-induced fluorescence techniques (invited)
Authors: Gelbwachs Jerry A.
Published: July 2002

Laser-induced fluorescence spectroscopy can provide a highly sensitive and selective means of atomic and ionic impurity detection. Because the photodetector can be physically isolated from the laser-excited region, these techniques can be applied to monitoring in hostile environments. The basic concepts behind fluorescence detection are reviewed. Saturated optical excitation is shown to maximize impurity atom emission yield while mitigating effects of laser intensity fluctuations upon absolute density calibration. A comparison of monitoring in high- and low-pressure monitoring environments is given. Methods to improve detection sensitivity by luminescence background suppression are presented.
Fast, variable apertures in count-rate optimized x-ray and particle diagnostic instruments for fusion
Authors: Munch J. , Hill D. , Higgins L. , Kirkwood R.
Published: July 2002

We are incorporating a system of fast, variable apertures in our designs for the x-ray, neutral, and ion spectrometers for plasma diagnostics on Mirror Fusion Test Facility B (MFTF-B). The purpose of these apertures is to maintain optimized count rates, and thus optimized measurement statistics during an experimental shot, where flux variations as large as 104–105 may occur in periods as short as 0.1 s. We shall discuss the application of the fast apertures to the x-ray spectrometer in particular, and to the other diagnostic instruments in general. The particular design requirements for the optimized aperture system will be discussed, as will be the influence the system has on the data-handling process. We have performed experiments to test this new concept and shall present the results, including the details of the closed-loop feedback circuit controlling the apertures, optimization of the loop gain, and the engineering issues of the system, such as the effect of vacuum feedthrough, position sensitivity, and alignment criteria.
Hydrogen cyanide laser interferometer of the JFT-2M tokamak and feedback stabilization of the beat frequency using a microcomputer
Authors: Uesugi Y. , Matoba T. , Ochiai I. , Mizuno K.
Published: July 2002

A hydrogen cyanide laser interferometer with three vertical chords was installed in the JFT-2M tokamak for electron density measurement. The optical arrangment of the interferometer is a Mach–Zehnder type and its structure is mechanically independent of the JFT-2M machine in order to suppress the mechanical vibration. Two HCN lasers are employed for direct reading of the chord averaged electron density by means of beat modulation method. The beat frequency between two HCN lasers is stabilized at a constant frequency by a feedback circuit using a microcomputer. A combination of short dielectric waveguides and TPX lenses is employed to compensate the refraction and divergence of the laser beam. It was shown experimentally that the interferometric measurement of the electron density was scarcely affected by the mechanical vibration of the interferometer and the refraction of the probing laser beam up to n̄e=6×1019 m−3.
Binary-coded decimal to binary digital input modification of a popular digital delay module
Authors: Bialkowski Stephen E.
Published: July 2002

A simple modification is described for converting the digital program code format of an Evans Associates model 4145 programmable time delay module from binary-coded decimal to binary. The modification results in a delay module which is more easily interfaced to a computer, has a greater programmable delay range with equivalent temporal resolution, and requires less power. Similar modifications are expected to have the same results on the models 4145-1 and 4146 modules.
Safer way to start a microwave discharge
Authors: Jones Mark E. , Ellison G. B.
Published: July 2002

A commercially available piezoelectric device has been shown capable of starting a microwave discharge. This device can be used in place of a Tesla coil, reducing the chance of damaging nearby electronics.
Opto-electronic system for displacement and vibration measurements
Authors: Francini F. , Macchiarulo M. , Tiribilli B. , Buah-Bassuah P. K.
Published: July 2002

A device capable of measuring small displacements and vibrations of a moving body is presented. A small mirror, firmly attached to the object under investigation, deflects a pair of laser beams onto two distinct photodetectors. From the examination of the output signals, it is possible to have separate information on the rotational and translational movements of a surface.
Microprocessor-based boxcar signal averager
Authors: Bano S. S. , Reddy P. N. , Reddy B. P. N. , Eswara Reddy N. C.
Published: July 2002

A boxcar signal averager using Intel 8085AH, an 8-bit microprocessor developed for processing free-induction decay (FID) signals from a pulsed nuclear-magnetic-resonance (NMR) spectrometer, is described. The boxcar signal averager works either in single-point mode or in scan mode. In addition to the software developed, the constructional features, circuit details, and the operation of the boxcar are discussed in detail.
Method to fabricate split coaxial line uhf probes for high-resolution NMR experiments
Authors: Kan S. , Ruaud J-P.
Published: July 2002

A conventional Helmholtz coil used in a uhf high-resolution NMR probe is usually constructed from copper or silver bands instead of thin wires. This paper proposes a novel probe fabrication process by which the entire tank circuit of the probe can be etched or cut out from a piece of copper foil. A balanced structure with split coaxial line as rf feeders is illustrated.
Absolute scanning [NF(a1Δ)] and [NF(b1Σ)] diagnostic method for the N2F4+H2 system
Authors: Jones Y. D.
Published: July 2002

The N2F4+H2 system is of interest for production of NF(a1Δ) as an energy-transfer species. Past studies have been plagued with the difficult NF(a1Δ) quantitative measurement due to interferences from the close-lying N2(B) and HF peaks. This paper deals with the development of a scanning diagnostic method to determine concentrations of NF(a1Δ) and NF(b1Σ) in the N2F4+H2 system and quantitative measurement of interferences with the diagnostic signal. The diagnostic method has been applied to a functioning high-pressure, high-temperature system.
Instrument for simultaneous measurement of density and viscosity
Authors: Kim Jin O. , Bau Haim H.
Published: July 2002

The speed of torsional stress waves transmitted in solid waveguides submerged in a liquid depends, among other things, on the liquid’s density and viscosity and the waveguides’ cross-sectional geometry. By measuring the speed of torsional stress waves in two waveguides of different cross-sectional geometries, one can obtain both the liquid’s density and viscosity. An on-line, real-time sensor for the simultaneous measurement of density and viscosity is described. The article details the sensor’s principles of operation and reports experimental results conducted using viscosity standard calibration liquids with well-known thermophysical properties. For fluids with density ρf >1×103 kg/m3, it is estimated that the instrument can measure density with a precision better than 0.5%. For fluids with the product shear viscosity (μ) and density, ρfμ>100 kg2/(m4 s), it can measure the shear viscosity with a precision better than 1%.
150-MeV racetrack microtron—injector of AURORA (abstract)
Authors: Sugitani M. ,   SHI Accelerator Research Group
Published: July 2002

A 150-MeV pulsed-racetrack microtron (RTM)1 is being developed as an injector for a 650-MeV SR ring by Sumitomo Heavy Industries, (SHI). The ring has a superconducting weak-focusing single-body magnet with an orbital diameter of 1.0 m. This light-source system, named AURORA,2 is designed for industrial use, especially for x-ray lithography with a critical wavelength of 1.02 nm. A unit of AURORA consists of the RTM injector, the compact storage ring, and sixteen SR light beamlines at the maximum. The RTM, which is 1.5 m in width, 3.7 m in length, and 1.5 m in height, is mainly composed of an injection system, a 6-MeV accelerating column, two main magnets with reverse field magnets, beam focusing, and correction elements. The injection system boosts a 20-keV electron beam from a gun up to an energy of 120 keV, using a single-gap cavity. This system, about 1.7 m in length, also bunches the beam with two re-entrant type bunchers in order to increase the acceleration efficiency of the RTM. The accelerating column, the resonant frequency of which is 2856 MHz, is of the conventional side-coupled standing-wave type. The rf power supplied by a pulsed 5.5-MW klystron is delivered not only to the accelerating column but also to the single-gap cavity and the two bunchers. The main magnets are characterized by slightly inclined poles in order to obtain a vertical focusing strength. The mean value of the magnetic field in the main magnets is 1.2 T. The reverse field magnets act as horizontal steerers as well as for turning back the first accelerated 6-MeV beam to the accelerating column. The focusing and correction elements include many permanent quadrupole magnets and some vertical steerers.

The specifications of the extracted beam are as follows. The pulse width is variable from 0.5 to 2 μs, and the repetition rate is up to 180 Hz. Emittances are to be 1π mm mrad in both the horizontal and vertical directions, and the energy spread is to be less than 0.1%. More than 5-mA peak current is expected after 25 turns with 6-MeV energy gain per each. All of the components have been manufactured and successfully tested.3 The assembly of the microtron has been completed and installed at SHI Tanashi Works, Tokyo. The test operation has started and the first 6-MeV electrons have been already observed. Further acceleration is being developed.
Measurement of permittivity at elevated temperatures using cavity perturbation and CO2 laser irradiation
Authors: Garner H. R. , Kaae J. L. , Stephens R. B. , Lewis A. C. , Lieber A. J. , DeHope W. J.
Published: July 2002

The complex permittivity of various ceramics has been measured at elevated temperatures. The permittivity measurements were made using the cavity perturbation technique at a fixed frequency of 10.1 GHz. The temperature of the sample was varied from 800 to 1000 °C by independently heating the samples using a CO2 laser (up to 27 W) directed into the cavity. The samples were mounted in quartz micropipettes and illuminated through the quartz. The sample temperature was measured using an optical pyrometer. This method is valuable for measuring the microwave properties of solids that normally are exposed to microwave radiation at elevated temperatures such as high-power microwave sources, components, and windows.
A high open-loop gain controller
Authors: Seppä Heikki , Sipola Hannu
Published: July 2002

A new controller, especially suited for phase-locked loops, is discussed. The controller, composed of RC-circuit electronics, has a gain with a slope of −30 dB/decade over a wide bandwidth. It is shown that in certain systems the present controller (PI3/2 controller) provides a much higher feedback gain than an ordinary proportional-integrator controller (PI controller). As applications, the superconducting quantum interference device (SQUID) and an electrically adjustable point contact used in surface microscopy or spectroscopy are discussed in some detail. The operation of the controller in a piezo-driven point contact was studied experimentally.
Proportional liquid-nitrogen valve and control system
Authors: Christman S. B.
Published: July 2002

A proportional magnetic valve has been developed that permits continuous flow of cryogenic fluids and gases. The proportional valve (PV) may be electrically controlled in the manual mode (open loop current drive) or in the automatic mode (closed loop current drive). A complete control system for liquid-nitrogen (LN) flow control applications is described. The system includes alarm and automatic supply tank switching features.
Noncontacting microstrip monitor for liquid film thickness
Authors: Hurley R. B. , Kaufman I. , Roy R. P.
Published: July 2002

A UHF/microwave technique that measures the wave propagation velocity along a modified microstrip line to determine the thickness of an adjacent film of water (up to about 1 mm) on a metallic surface is described. The technique may be extendable to the measurement of the thickness of coatings on both metallic and nonmetallic surfaces.
Very-low-temperature X-band electron-spin-resonance spectroscopy with small slow-wave resonant structures
Authors: Taleb S. , Hijmans T. W. , Clark W. G.
Published: July 2002

An easy to operate X-band electron-spin-resonance (ESR) spectrometer capable of operation down to temperatures as low as 0.4 K is described. In contrast to the usual waveguide and cavity setup, a nonmagnetic semirigid coaxial cable and a small loop are used to bring the microwave power down to the 3 He cryostat where a small-helix resonator encloses the sample. The use of a high-gain (18 dB min) and low-noise figure (3.5 dB max) X-band (8–12 GHz) microwave preamplifier in this apparatus permits the detection of a minimum of 1.5×109 spins/G at very low temperature (≂ 0.4 K), very low microwave power (≂0.25 mW), and low modulation frequency (530 Hz). Typical spectra recorded with this spectrometer are also given.
A simple high-speed calorimeter
Authors: Fröchte B. , Khan Y. , Kneller E.
Published: July 2002

A calorimeter is described to measure the increase in enthalpy, ΔH(T)=H(T)−H(T0), of metallic materials from room temperature (T0=300 K) to at least the melting temperature Tm, with Tm up to 2500 K. Heating rates are φ=dT/dt between about 105 and 107 K/s; accuracies are better than 2% in ΔH, and better than 5% in T.
In-vessel calibration of the JET neutron monitors using a 252Cf neutron source: Difficulties experienced
Authors: Jarvis O. N. , Sadler G. , van Belle P. , Elevant T.
Published: July 2002

The most direct method of obtaining an absolute calibration of the set of fission chambers used at JET for the measurement of the time-resolved neutron yield is by means of a standardized 252Cf radio-isotope neutron source which is moved around the vacuum vessel to map out the volume occupied by the plasma. The accuracy of this procedure can approach 10%. However, its applicability depends on the geometry of the tokamak and the location of the fission chambers. At JET, most of the neutrons reach the detectors by passing through the main diagnostic ports. Now that these ports have become surrounded by massive items of hardware, it is found that this equipment moderates and absorbs the 252Cf neutrons more strongly than 2.5 MeV neutrons. This paper examines the magnitude of the errors on the absolute calibration of the fission chambers introduced by this effect.
Bremsstrahlung isochromat spectroscopy with spin-polarized electrons
Authors: Borsje H. R. , Jongbloets H. W. H. M. , Kappert R. J. H. , Fuggle J. C. , Alvarado S. F. , Rochow R. , Campagna M.
Published: July 2002

We describe the construction and operation of a UHV system for bremsstrahlung isochromat spectroscopy in the x-ray regime (1463 eV) with spin-polarized electrons. The performance of the system is illustrated with measurements on Ni(110). The implications of this new technique to study magnetic properties through the spin-resolved electronic structure of the (near) surface are discussed.
New vapor phase spontaneous Raman spectrometer
Authors: Robinson J. C. , Fink M. , Mihill A.
Published: July 2002

A highly sensitive, spontaneous Raman spectrometer designed for the study of vapors and other low-density samples is discussed. The high sensitivity is achieved by means of the novel combination of a multipass light cell and a high-temperature gasdynamic focusing system. A complete description of the apparatus is given, along with the results of a sensitivity test in ambient air, as well as results demonstrating gasdynamic focusing of a vapor and Raman transitions in such a sample.
Magnetohydrodynamic velocimetry of a low-pressure plasma jet
Authors: Tardy P. , Dudeck M. A.
Published: July 2002

The velocity of a steady, low-pressure (≊0.1 Torr) plasma jet is measured by analyzing the local response of the medium to the action of an external magnetic field set up by two Helmholtz coils placed at the edge of the jet, yielding a field of 0.92 G/A. The induced electric field is measured by two floating-potential electrostatic probes. The mean velocity of the electrons (between 1000 and 5000 m s−1) is found from the generalized Ohm’s law.
Modeling and construction of a novel electron energy analyzer for rapid x-ray photoelectron spectroscopy spectra acquisition
Authors: Tepermeister I. , Sawin H. H.
Published: July 2002

A novel electron analyzer for rapid x-ray photoelectron spectroscopy (XPS) spectra acquisition and operation at 10−5 Torr pressure was modeled, constructed, and tested. The electron energy analyzer uses spherical retarding grids in conjunction with a post-monochromator to achieve bandpass operation, while maintaining the large transmission of a conventional retarding grid analyzer. The goal of modeling was to investigate the interaction between the retarding grids and the post-monochromator on the analyzer transmission and resolution. Both electron scattering at the retarding grids and fringe electric fields were found to be key factors in the overall analyzer performance. Based on the modeling results, an electron energy analyzer was constructed and tested using both gold samples and thin polystyrene films. 20-eV-wide scans could be obtained in 100–200 s with analyzer resolution of 1.0 eV. Monitoring of the polystyrene surfaces during and after exposure to molecular and atomic fluorine, indicated that the analyzer is useful for the collection of rapid, medium resolution XPS scans during the exposure of surfaces to reactive beams at background pressures as high as 10−5 Torr.