Probing the plasma near high power wave launchers in fusion devices for static and dynamic electric fields (invited).

An exploratory study was carried out in the long-pulse tokamak Tore Supra, to determine if electric fields in the plasma around high-power, RF wave launchers could be measured with non-intrusive, passive, optical emission spectroscopy. The focus was in particular on the use of the external electric field Stark effect. The feasibility was found to be strongly dependent on the spatial extent of the electric fields and overlap between regions of strong (>∼1 kV/cm) electric fields and regions of plasma particle recycling and plasma-induced, spectral line emission. Most amenable to the measurement was the RF electric field in edge plasma, in front of a lower hybrid heating and current drive launcher. Electric field strengths and direction, derived from fitting the acquired spectra to a model including time-dependent Stark effect and the tokamak-range magnetic field Zeeman-effect, were found to be in good agreement with full-wave modeling of the observed launcher.

High-harmonic fast-wave power flow along magnetic field lines in the scrape-off layer of NSTX.

A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost to the scrape-off layer (SOL) and deposited in bright and hot spirals on the divertor rather than in the core plasma. We show that the HHFW power flows to these spirals along magnetic field lines passing through the SOL in front of the antenna, implying that the HHFW power couples across the entire width of the SOL rather than mostly at the antenna face. This result will help guide future efforts to understand and minimize these edge losses in order to maximize fast-wave heating and current drive.

Predicting high harmonic ion cyclotron heating efficiency in Tokamak plasmas.

Observations of improved radio frequency (rf) heating efficiency in ITER relevant high-confinement (H-)mode plasmas on the National Spherical Tokamak Experiment are investigated by whole-device linear simulation. The steady-state rf electric field is calculated for various antenna spectra and the results examined for characteristics that correlate with observations of improved or reduced rf heating efficiency. We find that launching toroidal wave numbers that give fast-wave propagation in the scrape-off plasma excites large amplitude (∼kV m(-1)) coaxial standing modes between the confined plasma density pedestal and conducting vessel wall. Qualitative comparison with measurements of the stored plasma energy suggests that these modes are a probable cause of degraded heating efficiency.

Size, volume fraction, and nucleation of Stober silica nanoparticles.

29Si NMR, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) are used to monitor the synthesis of silica nanoparticles from the base-catalyzed hydrolysis of TEOS in methanol and ethanol. The reactions are conducted at a [TEOS] =0.5 M, low concentrations of ammonia ([NH(3)] =0.01-0.1 M), and [H(2)O] =1.1-4.4 M to resolve the initial size of the first nuclei and to follow their structural evolution. It is found that after an induction period where there is a buildup of singly hydrolyzed monomer, the first nuclei are fractal and open in structure. Interestingly, the nuclei are twice as large in ethanol (R(g) approximately 8 nm) as those in methanol (R(g) approximately 4 nm). The data suggest that the difference in primary particle size is possibly caused by a higher supersaturation ratio of the singly hydrolyzed monomer in methanol than in ethanol if it is assumed that the surface energy of the first nuclei is the same in methanol and ethanol. The particle number concentration and the volume fraction of the silica particles are calculated independently from the SAXS, DLS, and 29Si NMR results. Finally, the rate of nucleation is obtained from the particle number concentrations.

Sexual network structure as an indicator of epidemic phase.

Ascertaining epidemic phase for a sexually transmitted disease (STD) has depended on secular trend data which often contain significant artefacts. The usefulness of sexual network structure as an indicator of STD epidemic phase is explored in an analysis of community wide genital chlamydia reports, with network analysis of interviewed cases and linked sexual partners, in Colorado Springs, USA, 1996 to 1999. In this period, the chlamydia case rate per 100,000 increased by 46%. Three quarters of cases (n=4953) were interviewed, nominating 7365 partners; these, combined with index cases, made up the 9114 persons in the network. Epidemiologic analysis of cases suggests that secular trend increases are artefactual. Network analysis supports this view: overall network structure is fragmented and dendritic, notably lacking the cyclic (closed loops) structures associated with network cohesion and thus with efficient STD transmission. Comparison of network structure with that of an intense STD outbreak (characterised by numerous cyclic structures) suggests low level or declining endemic rather than epidemic chlamydia transmission during the study interval. These observations accord with intuitive and stochastic predictions.

CB1 receptor mediated analgesia from the Nucleus Reticularis Gigantocellularis pars alpha is activated in an animal model of neuropathic pain.

Cannabinoids are known to suppress responses to noxious stimulation in animals and man. Recent research has suggested a role for endogenous cannabinoids in the descending inhibition of dorsal horn cells via a supraspinal site of action. We have recently demonstrated [J. Physiol. 506(2) (1998) 459] that the nucleus reticularis gigantocellularis pars alpha (GiA) is a major source of such descending modulation, and importantly, that this system is activated in response to noxious stimulation. We have therefore investigated the role of CB1 receptor activation in mediating the antinociceptive effects of activation of GiA in models of acute and chronic pain. Microinjections (0.5 microl 60% DMSO) of either WIN 55,212-2 (5 microg, selective CB1 agonist), SR141716A (50 microg, competitive CB1 antagonist), both compounds together, or vehicle alone into GiA were performed prior to these tests in a randomised, blind manner. In control animals, WIN 55,212-2 markedly increased withdrawal latencies in the tail flick test and reduced responses to subcutaneous formalin. These effects were blocked by co-administration of SR141716A. These data suggest that activation of cannabinoid CB1 receptor subtypes in GiA leads to behavioural analgesia. In animals with partial sciatic nerve ligation, microinjection of drugs and injection of formalin were performed contralaterally to the site of ligation. Partial sciatic nerve ligation significantly reduced behavioural responses to contralaterally applied formalin. Microinjection of SR141716A to GiA reversed this inhibition of responses to formalin in animals with partial sciatic nerve ligation. These data provide evidence that endogenous CB1 receptor ligands are involved in GiA mediated antinociception, and that this system is important for the modulation of nociceptive transmission in an animal model of chronic neuropathic pain.

The behavioural importance of dynamically activated descending inhibition from the nucleus reticularis gigantocellularis pars alpha.

We have recently demonstrated (J Physiol 506 (1998) 459) that the dynamic activation of descending inhibition of the nociceptive response of spinal multireceptive cells occurs in the nucleus reticularis gigantocellularis pars alpha (GiA). In the same paper we have shown that Lamina I dorsal horn cells are responsible for activating this inhibition via a pathway which runs in the contralateral dorsolateral funiculus. The effects of dynamically activating this system by noxious stimulation on behavioural responses to noxious stimuli have not been established. Here we demonstrate the effects of GiA on the behavioural response during application of standardized noxious stimuli. As this system is activated in response to noxious stimulation (J Physiol 506 (1998) 459), it is possible that chronic pain states may also activate GiA. We have therefore investigated this possibility in animals following partial sciatic nerve ligation (an animal model of chronic pain; Pain 43 (1990) 205). Male Wistar rats (280-310 g) were anaesthetized with halothane (0.5-2% in O(2)). Guide cannulae for microinjections were stereotaxically placed above GiA. In one group of animals the sciatic nerve was partially ligated. Animals were allowed to recover for 4-6 days. The responses of each animal during the formalin test (Pain 4 (1977) 161) and the tail flick test (Pain 12 (1982) 229) were recorded on different days. Microinjections (0.5 microl) of either gamma-aminobutyric acid (GABA, 200 mM), D-L homocysteic acid (DLH, 25 mM) or 0.9% saline (as control) into GiA were performed during these tests in a randomized, blind manner. In animals without sciatic nerve ligation, microinjection of GABA to GiA did not significantly affect the animal's response during the tail flick test. However microinjection of DLH significantly increased the latency of tail flick from 6.2 +/- 0.8 to 8.4 +/- 0.5 s for up to 15 min (n = 7, P < 0.01, Mann-Whitney U-test). Microinjection of GABA to GiA increased the behavioural response to formalin between 10 and 20 min post-injection, while microinjection of DLH reduced this response at all time points except 10 min post-injection (n = 8, P < 0.05, Mann-Whitney U-test). In animals with sciatic nerve ligation, microinjections (0.5 microl) of either GABA (200 mM), or saline (as control) into GiA contralateral to the partial sciatic ligation were performed during these tests in a randomized, blind manner. Partial sciatic ligation significantly reduced the behavioural response to contralaterally applied formalin from 15 min post-injection onwards, compared to controls without sciatic nerve ligation. Microinjection of GABA to GiA significantly increased the behavioural response to formalin from 20 to 50 min post-injection. The inactivation of GiA only causes behavioural effects in nociceptive tests of a long enough duration to activate the system (i.e. the formalin test but not the tail flick test). Chemical activation of the system affects both tests. These data strongly support the concept of an important analgesic system which is activated in response to noxious stimulation, and subsequently acts to reduce behavioural responses to noxious stimuli.

Pain management in the special operations environment: regional anesthetics.

Pain relief is an essential component of combat casualty care. For the injured soldier, analgesia is not only a matter of comfort. Alleviating pain may allow the soldier to remain quiet when noise discipline is at a premium. It may also allow that person to continue to move, thus avoiding detection and potentially permitting the mission to carry on. Regional anesthetics provide an alternative to systemic medications and thus may avoid a clouded sensorium, limit narcotic administration, and provide superior pain relief. Standard local anesthetics and newer agents with potential field applicability are discussed along with their side effect profiles. Simple nerve block techniques that can be used by Army Special Forces medics, Navy SEAL and Reconnaissance corpsmen, and Air Force pararescuemen in the far forward environment are described step by step. The advantages of these regional anesthetic methods should make their use a must for every special operations medical care provider.

Periaqueductal grey mediated inhibition of responses to noxious stimulation is dynamically activated in a rat model of neuropathic pain.

The periaqueductal grey (PAG) has been shown to be a major source of descending inhibition of dorsal horn cells (Textbook of Pain (1999) 309). However, few studies have demonstrated alterations in behavioural responses to noxious stimulation following inactivation of this nucleus. Many behavioural studies have looked for effects on nociceptive withdrawal thresholds in acute nociceptive tests. These tests would not reveal the presence of inhibition which is activated in response to noxious input. We have therefore investigated this possibility by studying behavioural responses to subcutaneous formalin injection in control animals, and in animals following partial sciatic nerve ligation (an animal model of neuropathic pain (Pain 43(2) (1990) 205). In control animals, microinjection of gamma-aminobutyric acid (GABA) to PAG did not significantly alter behavioural responses to formalin, while microinjection of D,L-homocysteic acid (DLH) reduced these responses. Responses to contralaterally applied formalin were significantly reduced in animals with partial sciatic ligation. Microinjection of GABA to PAG significantly increased these behavioural responses to formalin. We conclude that a component of PAG mediated inhibition of nociception is inactive under normal conditions. This inhibition may be activated by persistent nociceptive input, and possibly reflects long term changes in nociceptive circuitry which occur in neuropathic pain states.

Chlamydia transmission: concurrency, reproduction number, and the epidemic trajectory.

To identify factors that influence individual and group transmission of Chlamydia, the authors conducted community-wide contact tracing of chlamydia cases in Colorado Springs, Colorado, from mid-1996 to mid-1997. Case patients identified persons with whom they had had contact during the 6 months preceding diagnosis; contacts were actively sought and offered DNA amplification testing. Sexual contact networks were used to identify "source cases" and "spread cases," permitting estimation of the basic reproduction number (R0) for individuals and groups. Network and epidemiologic factors influencing R0 were assessed using univariate and multivariate procedures. Of 1,309 case patients, 1,131 (86%) were interviewed, and 2,409 contacts were identified. The 1,131 interviewed cases yielded 623.9 computed spread cases, for an overall R0 of 0.55. Few subgroups analyzed yielded a mean R0 exceeding unity-an observation in keeping with routine surveillance information which suggests that chlamydia incidence is declining in Colorado Springs. Concurrency, a network measure of simultaneous partnerships, was the most powerful predictor of transmission. Direct estimation of basic reproduction numbers for chlamydia using contact tracing techniques is feasible and can produce useful data with which to prioritize control efforts, evaluate interventions, and gauge the place of chlamydia on the epidemic continuum.

Establishing efficient partner notification periods for patients with chlamydia.

OBJECTIVES: To delineate chlamydia partner notification periods with high proportions of infected, untreated sexual partners, and to evaluate relevant Centers for Disease Control (CDC) recommendations. METHODS: Disease Intervention Specialists (DIS) offered contact tracing services to all chlamydia patients (N = 1,309) reported in Colorado Springs between July 1996 and June 1997. Patients were asked to identify sexual partners during the 180 days preceding treatment. Partners were actively sought by DIS and offered DNA amplification testing. RESULTS: Of 1,309 patients, 1,109 were interviewed, resulting in 2,293 named partners. Two fifths of eligible partners were located; inability to examine partners was related to time of last exposure and to frequency of sexual exposure. Of located partners, 95% were tested with DNA amplification technology. Adherence to CDC criteria identified 88% of infected, untreated partners; the other 12% consisted mainly of epidemiologically important asymptomatic men whose infection is seldom identified by current public health interventions. CONCLUSIONS: The chlamydia partner notification recommendations of the CDC are adequate, but miss men with long-standing infection. These men contribute to entrenched chlamydia endemicity; targeted programs to screen high-risk men merit serious consideration.

Detection of Clostridium difficile toxins from the small intestine and cecum of rabbits with naturally acquired enterotoxemia.

Four specific-pathogen-free rabbits with anorexia died peracutely; decreased fecal output, nasal exudate, and labored breathing were the only other clinical abnormalities observed in two of the rabbits before death. The animals, three juveniles and one adult, were on a standard polyclonal antibody production regimen and had received immunizations approximately 2 weeks before presentation. External examination revealed distended abdomen and perineal fecal staining. At necropsy the small intestine was distended with fluid, and the cecum was distended with chyme. The small intestines and cecum had marked serosal hyperemia. Anaerobic bacterial culture techniques were used to isolate Clostridium difficile from the small intestine (3/4) and cecum (2/4). In all cases C. difficile toxin B was detected at high titers (10(2) to > 10(5)) in the small intestine by cytotoxicity assay with HeLa 229 cell culture. In two of the four rabbits C. difficile was isolated, and cytotoxin titers were detected at 10(1) and 10(4) in the cecum of affected rabbits. Toxin B was neutralized with C. sordellii antiserum but not C. spiroforme antiserum. In addition, toxin A was detected in each of the cytotoxin B-positive samples by a commercial toxin A enzyme immunosorbent assay. In vitro production of toxins A and B was detected from each culture isolate after incubation in chopped meat broth. These cases are noteworthy because spontaneous (nonantibiotic-associated) C. difficile enterotoxemia has not been previously reported in rabbits. Also the toxins of clostridial organisms are usually documented in the cecum, not the small intestine, of rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

High school student employment in social context: adolescents' perceptions of the role of part-time work.

The majority of middle-class high school students now work at part-time jobs during the academic year. During in-depth interviews, 35 seniors at a predominantly middle-class high school were asked to relate their jobs, or their decisions not to work, to the social contexts of employment. Attitudes toward the workplace and interpretations of the work ethic were analyzed within these contexts in order to examine the role of part-time employment in their lives. The findings of this study suggest that a negative stereotype of the high school student-worker is not justified. Instead, part-time work upholds a variety of interpretations of the work ethic within the framework of normative middle-class values. Future studies are needed to relate part-time work among adolescents to social and economic as well as developmental perspectives.

Financial modeling for hospital materials managers.

In this issue, HMM Editorial Board member Dennis Green concludes his discussion of five types of financial analysis materials managers are increasingly expected to perform. The final two models, extrapolated cash flow and negotiation models are best run with a personal computer. These models often have many variables and/or time periods, which frequently change as terms become clarified and negotiated. With a computer, recalculations are simplified.

Financial modeling for hospital materials managers.

During the 10 years preceding the era of prospective payment, hospital materials managers (in response to pressure from clinical areas) bought more and more disposables to replace items that once were assembled by the central supply department. As a consequence, nearly 60% of the output of today's typical central supply department consists of distributing prepackaged disposables with the only "value-added" being the attachment of a patient charge sticker for reimbursement from the patient's insurance company.

Financial modeling for hospital materials managers. Part I.

Beginning in this issue, HMM Editorial Board member Dennis Green will explore five types of financial analysis materials managers are increasingly expected to perform. By the end of this series, HMM readers equipped with a personal computer and/or a financial calculator will have learned to make the following types of financial decisions: Whether to take advantage of a "sale"; Whether to make or buy; How to analyze the "reagent rental" alternative to purchase: How to extrapolate a series of cashflows in present value; and How to create negotiation models for cash acquisitions. As always, HMM welcomes your comments and suggestions.

Managing production conversions.

The ability to "move business" from one vendor to another has been one of the historical strengths of the centralized hospital materials management function. It continues to be one of the most effective economic motivators in the discounting of hospital supplies. Conversion to standardized products is a proven way of moving business, but is it only effective where it is accompanied by good planning and the disciplined willingness to see the process through. This applies whether hospitals are using independent supply contracts, group purchasing contracts, prime vendor agreements, or stockless purchasing affiliations. It also applies to hospitals with active value analysis/product standardization committees and those without them.

Biplane radiographic measurements of reversible displacement (including clinical loosening) and migration of total joint replacements.

UNLABELLED: We studied nineteen total knee replacements and thirty-three total hip replacements with simultaneous biplane radiography to measure in vivo micromotion at the cement-bone interface. Spherical cobalt-chromium markers were embedded in the cement and cortical bone. Relative motion of the cement-markers was measured with respect to the markers in the cortical bone. Reversible displacement (relative motion during a change from non-weight-bearing to weight-bearing) and migration (relative motion over time from one non-weight-bearing study to another) were calculated. The resolution of the measuring system was 0.2 millimeter. The range for symptomatic reversible displacement was 0.4 to 4.5 millimeters, while that for asymptomatic reversible displacement was 0.3 to 1.9 millimeters. All reversible displacement of less than 0.4 millimeter was asymptomatic. Migration of as much as 2.1 millimeters occurred without concomitant reversible displacement. All radiolucent lines correlated with measured reversible displacement. Half of the patients who were evaluated two weeks postoperatively had measurable reversible displacement. CLINICAL RELEVANCE: Our findings were based on a small series from a selected population. The incidence of measured reversible displacement (75 per cent) was based on in vivo techniques and included symptomatic and asymptomatic reversible displacement; therefore, it was higher than the incidence of clinical loosening (9.6 per cent in our series). Simultaneous biplane radiography may become an important adjunct in the postoperative management of patients with a total joint replacement.