Determination of limiter design and material composition of MT-II spherical tokamak

MT-II is a spherical tokamak with a major radius of 0.15 m and a minor radius of 0.09 m, currently under development at the Pakistan Tokamak Plasma Research Institute. It is designed with a higher elongation of 2.67. This paper presents the design and material analysis of the limiter configuration for the MT-II tokamak, which is being carried out in two phases. In the first phase, theoretical studies and calculations are performed to estimate the plasma edge temperature, density, particle velocity, input power, heat flux, heat load and surface temperature on the limiter tile. In the second phase, computational techniques are applied to analyses the material properties, the maximum/minimum surface temperature rise (∆T °C) at stable heat load and power deposition based on theoretical calculations that will help optimize the design parameters of the limiter. The type of material and the surface temperature of the limiter as well as the general design parameters of MT-II are included in the proposed poloidal limiter. The results suggest that crystalline vein graphite is a suitable candidate for the proposed poloidal limiter. A combination of mechanical and electrical feedthrough techniques are used to improve the performance of the limiter. The proposed limiter is able to meet the requirements of MT-II.

Reactive oxygen species mediate a cellular 'memory' of high glucose stress signalling

AIMS/HYPOTHESIS

A long-term 'memory' of hyperglycaemic stress, even when glycaemia is normalised, has been previously reported in endothelial cells. In this report we sought to duplicate and extend this finding.

MATERIALS AND METHODS

HUVECs and ARPE-19 retinal cells were incubated in 5 or in 30 mmol/l glucose for 3 weeks or subjected to 1 week of normal glucose after being exposed for 2 weeks to continuous high glucose. HUVECs were also treated in this last condition with several antioxidants. Similarly, four groups of rats were studied for 3 weeks: (1) normal rats; (2) diabetic rats not treated with insulin; (3) diabetic rats treated with insulin during the last week; and (4) diabetic rats treated with insulin plus alpha-lipoic acid in the last week.

RESULTS

In human endothelial cells and ARPE-19 retinal cells in culture, as well as in the retina of diabetic rats, levels of the following markers of high glucose stress remained induced for 1 week after levels of glucose had normalised: protein kinase C-beta, NAD(P)H oxidase subunit p47phox, BCL-2-associated X protein, 3-nitrotyrosine, fibronectin, poly(ADP-ribose) Blockade of reactive species using different approaches, i.e. the mitochondrial antioxidant alpha-lipoic acid, overexpression of uncoupling protein 2, oxypurinol, apocynin and the poly(ADP-ribose) polymerase inhibitor PJ34, interrupted the induction both of high glucose stress markers and of the fluorescent reactive oxygen species (ROS) probe CM-H(2)DCFDA in human endothelial cells. Similar results were obtained in the retina of diabetic rats with alpha-lipoic acid added to the last week of normalised glucose.

CONCLUSIONS/INTERPRETATION

These results provide proof-of-principle of a ROS-mediated cellular persistence of vascular stress after glucose normalisation.

Safety profile of repaglinide as used in general practice in England: results of a prescription-event monitoring study

Repaglinide is a prandial glucose regulator indicated for management of type 2 diabetes. This post-marketing study used the observational cohort technique of prescription-event monitoring (PEM) to monitor safety of repaglinide prescribed in primary care in England. Patients were identified from dispensed prescriptions issued by general practitioners (GPs) between December 1998 and January 2001. Demographic and clinical event data were collected from questionnaires posted to GPs at least six months after the date of first prescription for each patient. The cohort consisted of 5731 patients [median age 60 (IQR 51-68), 49.9% male]. Event incidence densities (IDs) [no. 1st reports/1000 patient-months of exposure] were calculated for all events reported. The most frequently recorded clinical events in the first month were diarrhoea (ID(1) 10.3), malaise/lassitude (ID(1) 8.1) and nausea/vomiting (ID(1) 7.9). The most frequently reported reason for stopping was 'not effective' (647), with the most common clinical reasons being diarrhoea (60), malaise/lassitude (55) and intolerance (54). One hundred and thirteen adverse drug reactions (ADRs) were reported, with the most frequently specified being diarrhoea (10), abdominal pain (10) and nausea/vomiting (9). We concluded that repaglinide is generally well tolerated when used in general practice in England and did not identify any serious unrecognised adverse events.

Age- and gender-specific asthma death rates in patients taking long-acting beta2-agonists: prescription event monitoring pharmacosurveillance studies

OBJECTIVE

Prescription event monitoring is a national drug safety surveillance scheme in which prescribers are prompted to report events and deaths following prescription of newly marketed drugs. This paper presents age- and gender-specific asthma death rates in patients prescribed the long-acting beta2-agonists salmeterol and bambuterol.

DESIGN AND SETTING

Pharmacosurveillance cohort study of general practice patients in England.

PATIENTS AND PARTICIPANTS

15 406 patients prescribed salmeterol between December 1990 and May 1991, and 8098 patients prescribed bambuterol between February 1993 and December 1995.

METHODS

Patients prescribed these drugs by general practitioners in England were identified using the national pharmacovigilance system of prescription event monitoring, in which details of all dispensed prescriptions were provided in confidence by the Prescription Pricing Authority. Questionnaires were sent to the prescriber asking for details of events occurring after the first prescription. In each study an attempt was made to establish the cause of all deaths reported on the questionnaires, via retrieval of the patients' medical notes or examination of death certificates.

OUTCOME MEASURES AND RESULTS

There was little evidence of heterogeneity in the drug-specific death rates and we therefore present the combined age- and gender-specific death rates for the 2 cohorts. Overall, there were 85 asthma deaths among people taking the long-acting beta2-agonists studied (bambuterol and salmeterol cohorts combined). The overall death rate was 2.33 [95% confidence interval (CI) 1.84 to 2.84] per 10000 months of observation. There were 37 asthma deaths among male patients (rate 2.40 per 10000 months of observation; 95% CI 1.74 to 3.40) and 48 asthma deaths among female patients (rate 3.08 per 10000 months of observation; 95% CI 2.21 to 3.98). There was no difference in death rates when male and female patients were compared (rate ratio 0.78; 95% CI 0.49 to 1.22; p = 0.26).

CONCLUSION

Prescription event monitoring is a form of prompted surveillance allowing rapid, uniform, national and practical assessment of newly marketed drugs on large cohorts of patients in England. These data provide benchmark rates from which to assess the performance of newly prescribed anti-asthma drugs and generate hypotheses for later analytical investigation in which confounding by indication and asthma severity can be controlled for. Any differences in these rates should be considered as a source of signal generation within the context of a surveillance programme, rather than as robust evidence of any mortality differential between drugs.

Finasteride and tamsulosin used in benign prostatic hypertrophy: a review of the prescription-event monitoring data

OBJECTIVE

To review the results of non-interventional observational cohort studies of 14 772 patients treated with finasteride and 12 484 patients treated with tamsulosin, both studies being of national proportions and undertaken in general medical practice in England.

METHODS

Both studies were undertaken by prescription-event monitoring (PEM), whereby the exposure data are derived from information provided in strict confidence by the Prescription Pricing Authority of the National Health Service. The outcome data are derived from 'green form' questionnaires completed by the prescribing general practitioners (GPs). Additional data are obtained by medical follow-up with the attending practitioners. Adverse experience was measured in three ways; as reports of events which the doctors considered to represent adverse drug reactions; as reports of reasons for stopping the drug; and by studying the incidence density of each reported event. For these purposes a computerized dictionary containing 1430 higher level terms was used. The duration of exposure in the finasteride study was approximately 1 year and was approximately 6 months in the tamsulosin study.

RESULTS

The outcome data on the 14 772 and 12 484 patients treated in the finasteride and tamsulosin studies were derived from the 63% and 57.4% of the green forms sent out and returned, respectively. The finasteride cohort included two women and the tamsulosin cohort 70 women. The mean (SD) age of the men in the two cohorts was, respectively, 69.0 (9.2) and 66.2 (11.7) years. Both drugs were well tolerated on long-term therapy and 69.6% (10 274 patients) of the total finasteride and 62.0% (7739 patients) of the total tamsulosin cohort were still receiving the drug at the end of 6 months. In the finasteride study, impotence or ejaculatory failure was reported in 2.0% of the patients still receiving the drug; there were reports of decreased libido in 1.0% and gynaecomastia was reported whilst the drug was still being prescribed in 39 patients (0.3% of the cohort). With tamsulosin, uncommon cases of dizziness, headache, malaise and hypotension (89 reports in 12 484 patients, i.e. 0.7% of the cohort) were common to the findings of reported adverse reactions, reasons for stopping the drug and events of highest incidence density. None of the deaths which occurred in either of these large cohorts was attributed by either the reporting GPs or the PEM medical staff to the drugs examined. Conclusion The GPs rated the drugs effective in most patients; tolerance and adverse experience was consistent with the known pharmacology of the two drugs. No serious, unexpected adverse effects were identified.

The rates of common adverse events reported during treatment with proton pump inhibitors used in general practice in England: cohort studies

AIMS

To estimate the rates of common adverse events in patients treated with the proton pump inhibitors omeprazole, lansoprazole and pantoprazole in general practice in England.

METHODS

In prescription-event monitoring cohort studies, data on dispensed prescriptions prescribed by general practitioners in England soon after each drug was launched were linked to subsequent clinical events recorded by the prescriber. 16 205 patients prescribed omeprazole between June 1989 and June 1990, 17 329 patients prescribed lansoprazole between May and November 1994, and 11 541 patients prescribed pantoprazole between December 1996 and June 1997 were studied.

RESULTS

The commonest adverse events in the omeprazole, lansoprazole and pantoprazole cohorts were diarrhoea (incidence: 0. 18, 0.39 and 0.23 per 1000 days of exposure, respectively); nausea/vomiting (incidence: 0.16, 0.22 and 0.18 per 1000 days of exposure, respectively); abdominal pain (incidence: 0.17, 0.21 and 0. 17 per 1000 days of exposure, respectively); and headache (incidence rates: 0.10, 0.17 and 0.15 per 1000 days of exposure, respectively). The remaining adverse events occurred at rates of less than 0.11 per 1000 days of exposure. There were little absolute differences in the rates of most events between the three proton pump inhibitors. However, diarrhoea was more commonly associated with lansoprazole compared with omeprazole (rate difference: 0.21 per 1000 days of exposure; 95% CI 0.17, 0.25; rate ratio: 2.11; 1.78, 2.51), and there was a clear age-response relationship.

CONCLUSIONS

Adverse events occurred relatively infrequently in all three cohorts. There were only small absolute differences in event rates between the three drugs, although these data suggest the hypothesis that lansoprazole is associated with more frequent occurrence of diarrhoea, particularly in the elderly.

Sedation with "non-sedating" antihistamines: four prescription-event monitoring studies in general practice

OBJECTIVES

To investigate the frequency with which sedation was reported in post-marketing surveillance studies of four second generation antihistamines: loratadine, cetirizine, fexofenadine, and acrivastine.

DESIGN

Prescription-event monitoring studies.

SETTING

Prescriptions were obtained for each cohort in the immediate post-marketing period.

SUBJECTS

Event data were obtained for a total of 43 363 patients.

MAIN OUTCOME MEASURES

Reporting of sedation or drowsiness.

RESULTS

The odds ratios (adjusted for age and sex) for the incidence of sedation were 0.63 (95% confidence interval 0.36 to 1.11; P=0.1) for fexofenadine; 2.79 (1.69 to 4.58; P<0.0001) for acrivastine, and 3.53 (2.07 to 5.42; P<0.0001) for cetirizine compared with loratadine. No increased risk of accident or injury was evident with any of the four drugs.

CONCLUSIONS

Although the risk of sedation was low with all four drugs, fexofenadine and loratadine may be more appropriate for people working in safety critical jobs.

Inhibition of antigen-induced airway hyperresponsiveness by ultralow molecular-weight heparin

Unfractionated heparin (UF-heparin) has been shown to prevent antigen-induced airway hyperresponsiveness (AHR), but it is ineffective when administered after the antigen challenge. We hypothesized that the failure of UF-heparin to modify postantigen AHR might depend on molecular weight. We therefore studied the effects of UF-heparin and three low-molecular-weight heparin fractions (medium-molecular-weight heparin [MMWH]; low-molecular-weight heparin [LMWH]; and ultralow-molecular-weight heparin [ULMWH]) on antigen-induced AHR and histamine release in bronchoalveolar lavage fluid (BALF). Specific lung resistance (SRL) was measured in 20 allergic sheep before, immediately after, and up to 2 h after challenge with Ascaris suum antigen. Airway responsiveness was expressed as the cumulative provocative dose of carbachol, in breath units, that increased SRL by 400% (PD400). PD400 was determined before and 2 h after antigen, both without and after treatment with aerosolized UF-heparin (1,000 U/kg) and various heparin fractions (0.04 mg/kg to 5 mg/kg) administered after the antigen challenge. Inhaled UF-heparin (n = 4), MMWH (n = 4), and LMWH (n = 6) failed to modify postantigen AHR when administered after the challenge. Only ULMWH (n = 6) inhibited postantigen AHR in a dose-dependent manner (percent protection ranged from 31% to 139%). In eight additional sheep, histamine in BALF was measured with a radioimmunoassay (RIA) before and after the segmental antigen challenge, without and after pretreatment with inhaled UF-heparin, LMWH, or ULMWH. Inhaled UF-heparin and LMWH inhibited antigen-induced histamine release as measured in BALF by 81% and 75%, respectively; whereas ULMWH was ineffective in this respect. We conclude that: (1) modification of antigen-induced AHR by fractionated heparins is molecular-weight dependent; and (2) only ULMWH attenuates AHR when administered after antigen challenge, via an unknown mast-cell-independent action.

Heterogeneity of allergic airway responses in sheep: differences in signal transduction?

In preliminary studies we have observed that inhaled heparin blocks antigen-induced airway responses in sheep that develop only acute responses to inhaled antigen (acute responders), but not in sheep that develop both acute and later responses (dual responders). Because heparin is an antagonist of inositol triphosphate (IP3) (one of the pathways involved in stimulus-secretion-coupling in mast cells), the differential effect of inhaled heparin in acute responders and dual responders might indicate the involvement of different signaling pathways during IgE-mediated mast cell reactions. Therefore, in this study we compared the effects of heparin on antigen-induced bronchconstriction, allergic cutaneous reaction, and histamine release into bronchoalveolar lavage fluid (BAL) in sheep that develop only acute responses or dual responses to inhaled Ascaris suum antigen. Specific lung resistance (SRL) was measured in 21 sheep (eight acute responders; 13 dual responders) before and after inhalation challenge with antigen, without and after pretreatment with inhaled heparin (1,000 units/kg). Histamine in BAL was measured by RIA before and after segmental antigen challenge, without and after pretreatment with inhaled heparin (eight acute responders; eight dual responders). In acute responders, mean +/- SE SRL increased by 197 +/- 21% with antigen; this was prevented by inhaled heparin (deltaSRL = 15 +/- 7%; p < 0.05). In dual responders, inhaled heparin had no effect on antigen-induced early (deltaSRL = 328 +/- 51% versus 305 +/- 76%) or late (deltaSRL = 201 +/- 33% versus 163 +/- 15%) responses. After segmental antigen challenge, BAL mean +/- SE histamine increased from 2.09 +/- 0.8 nM to 75.4 +/- 21.1 nM in acute responders and 1.58 +/- 0.7 nM to 66.8 +/- 27.3 nM in dual responders (p < 0.01). Inhaled heparin inhibited the increase in BAL histamine by 81% in acute responders (p < 0.05) and by only 19% in dual responders (p = NS). As was seen in the airways, heparin attenuated the allergic cutaneous reaction in acute responders by 46% (p < 0.05), but it was ineffective in dual responders. In contrast, H-7, a nonspecific protein kinase C inhibitor, attenuated the cutaneous reaction in dual responders by 28% (p < 0.05), but it was ineffective in acute responders. These data suggest that heterogeneity of allergic airway response is related to difference in mast cell signal transduction; IP3 is the predominant second messenger in acute responders, whereas non-IP3 pathways may be involved in dual responders.

Electro-Rheological-Fluid-Based Articulating Robotic Systems

The limitations of the current generation of robotic systems has triggered a new research thrust for predicting the elastodynamic response of assemblages of articulating flexible-bodied systems. This research thrust is extended herein by proposing the fabrication of robotic systems in either monolithic or ultra-advanced composite laminated high-strength, high-stiffness materials in which are incorporated electro-rheological fluids. These multiphase fluid systems, which change their rheological behavior instantaneously when subjected to an externally applied electrical field, provide a potential for tailoring the vibrational characteristics of these hybrid materials from which the structural members of the proposed robotic systems are fabricated. This paper is focused on developing the necessary design tools for predicting the vibrational response of flexible multibodied articulating systems fabricated with this new class of advanced materials. A variational theorem is developed herein as a basis for finite element formulations which can be employed to predict the elastodynamic response of these systems. A coherent combination of experimental and theoretical work on cantilevered beams is presented to demonstrate the viability of the proposed design methodology. In addition, computer simulation results are presented to demonstrate the potential payoffs in terms of superior performance characteristics of a new generation of robotic systems capitalizing on this innovative and revolutionary design philosophy.

Effect of inhaled leukotriene C4 on cardiopulmonary function

The changes in transcutaneous oxygen saturation (SaO2%) and airway responses to inhaled histamine and leukotriene C4 (LTC4) were examined in 10 asthmatic patients, and the effect of inhaled LTC4 (16 nmol) on cardiopulmonary hemodynamics was examined in seven nonasthmatic patients undergoing diagnostic cardiac catheterization. In asthmatic patients, LTC4 produced oxygen desaturation on two occasions. At a lower dose (2.0 nmol) LTC4 produced a marked fall in SaO2% that lasted less than 15 min and occurred in the absence of significant bronchoconstriction as measured by changes in FEV1, FEF25-75, and SGaw. At a higher cumulative dose (7 nmol), LTC4 caused prolonged oxygen desaturation with slow recovery and this was associated with significant bronchoconstriction. In contrast, histamine inhalation produced a single response with a fall in both FEV1 and SaO2% of short duration. The dose-response characteristics of LTC4 and histamine on oxygen desaturation in asthmatic patients appear to differ significantly and probably are dependent on relative sensitivities of pulmonary vascular and bronchial smooth muscle to these agonists. A single inhaled dose of LTC4 in nonasthmatic subjects produced a marked drop in PaO2 with significant increase in AaPO2, and this was associated with a mean (SEM) decrease in FEV1 of 14% (2.5) from the baseline. The mean cardiac output fell by 15% (3.4) without significant changes in blood pressure and heart rate. There was no electrocardiographic evidence of myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Approximate theory of Stokes amplification and conversion valid at large gain

We predict Stokes-beam divergence, origin, and gain for large-gain Raman amplifiers as functions of pump-beam divergence and pump power in terms of simple analytical expressions. Stokes divergence is found to peak at a pump power twice above threshold. Results are in excellent agreement with exact computer solutions and explain recent experimental observations.