Very High Research Articles

Cellular automata model for transitions to improved confinement regimes in fusion plasma

In magnetically confined plasmas, the second derivative of the density is known to be related to the E × B velocity shear that rules the transitions to improved confinement regimes. In this work we present a cellular automata model for transport that includes diffusion and avalanche-like mechanisms controlled by critical parameters. Assuming the hypothesis that a strong negative value of the second derivative of the density reduces the strength of avalanches, the model shows the emergence of different confinement regimes that are found to be analogue to low (L), high (H) and very high (VH) confinement modes in real plasma. Transitions between such regimes can be controlled by the parameter representing the fuelling intensity. In particular, the model reproduces the formation of a pedestal during the transition from L to H confinement regimes, and shows hysteresis phenomena.

A GIS based SINTACS model for assesing aquifer vulnerability

Assessing aquifer vulnerability is very important because of optimization of restrictive measures in watershed protection area. This paper describes the procedure of aquifer vulnerability estimation and compilation of groundwater vulnerability map of Selniška Dobrava porous aquifer. The map presents areas of greatest potential for groundwater contamination on the basis of hydrogeological conditions and human impacts. Ali major geological and hydrological factors that affect and control groundwater movement (in unsaturated and saturated zone) were incorporated into SINTACS model of vulnerability map. A Geographical Information System (GIS) was used to create a groundwater vulnerability map by overlaying the available hydrogeological data. The resulting vulnerability map was then integrated with a map of land use as an additional parameter in the SINTACS model to assess the potential risk of groundwater pollution (Civita & De Maio 1997). Aquifer vulnerability was classified in six classes by interval values of SINTACS index from low (I) to very high (VI) vulnerability. The north part of Selniška Dobrava area is classified into low to moderate class (II, III). The south and west part, where the main aquifer is located, are classified into high aquifer vulnerability class (IV, V).

The impact of microalbuminuria measured by qualitative or quantitative methods on risk evaluation in hypertensive patients: Results from ICEBERG study

Although microalbuminuria determined by quantitative methods seems to be more accurate, using dipstick is simpler and cheaper, thus making this qualitative method more suitable for screening in primary healthcare settings for hypertensive patients. The primary purpose of Intensive / Initial Cardiovascular Examination regarding Blood pressure levels: Evaluation of Risk Groups (ICEBERG) study protocol is to determine the impact of different laboratory tests on cardiovascular risk stratification of subjects with BP levels ≥130/85 mmHg. This report focuses on the comparison of the impact of quantitative and qualitative microalbuminuria detection on the risk evaluation. ICEBERG is a healthcare organization-based epidemiological study, conducted at 217 centers (20 cardiology -1- and 197 primary healthcare centers -2-). In group 1, microalbuminuria was calculated as urinary albumin/creatinine ratio in random urine samples (quantitative method) and in group 2, urine strips (Micral-test Microalbuminuria®, Roche Diagnostics GmBh) were used (qualitative method). 9268 patients were included in the analysis (765 and 8496 in groups 1 and 2, respectively). Initial risk assessment was performed according to ESC-ESH 2003 guidelines and reassessment was done by using quantitative and qualitative methods. The study patients were 58.4±11.3 years old (female 65.3%). 53.8% and 54.5% of the patients were classified into high (H) or very high (VH) added risk group with baseline evaluation, in groups 1 and 2, respectively. Switching upwards to H/VH risk group was 6.2% and 6.6%, when quantitative and qualitative microalbuminuria tests were taken into account, respectively. Risk group switching upwards were found to be similar in both quantitative and qualitative microalbuminuria groups, thus demonstrating that dipstick microalbuminuria detection has almost the same effectiveness when compared with quantitative.

The X-Ray Properties of the Nearby Star-forming Galaxy IC 342: TheXMM-NewtonView

We present results on the X-ray properties of IC 342 using a 10 ks XMM-Newton observation. Thirty-five sources are detected coincident with the disk of IC 342 (more than tripling the number known), of which ?31 are likely to be intrinsic to IC 342. This point-source population exhibits a diverse range of spectral properties and has an X-ray luminosity function slope and infrared luminosity comparable to that of starburst galaxies such as M82 and the Antennae, while its relative lack of extended X-ray emission is similar to the properties of quiescent spirals. Although we find no evidence of short-term variability in any of the X-ray sources, we do detect long-term variability between this observation and the 1991 ROSAT and 1993/2000 ASCA observations for five sources. Notably, the second most luminous source in IC 342 (X-2) is found to have an absorption-corrected 0.5?10 keV luminosity of 5.75 ? 1039 ergs s-1 and a spectrum best fitted by an absorbed multicolor accretion disk model with Tin = 2.17 keV and NH = 15.3 ? 1021 cm-2. This is the lowest luminosity state observed for X-2 to date, although the slope of the spectrum is intermediate between the previously observed low/hard and high/soft states. IC 342 X-1, on the other hand, is found to be in an identical state to that observed in 2000 with ASCA. Assuming X-1 is in an anomalous very high (VH) state, then either (1) X-1 has remained in this state between 2000 and 2002 and is therefore the longest duration VH-state binary ever observed, or (2) it was simply caught in a VH state by chance in both the 2000 ASCA and 2002 XMM-Newton observations. We have also confirmed the ROSAT HRI result that the nucleus of IC 342 is made up of both pointlike and extended emission, with the extended emission contributing ?55% and ?35% in the 0.3?2.0 keV and 2.0?10.0 keV bands, respectively. The spectrum of the nucleus is best fitted by an absorbed two-component model consisting of a thermal plasma with a temperature of kT ? 0.3 and a power law with a photon index of ? ? 2.53. The relative fluxes of the two spectral components suggest that the nucleus is complex, with a soft extended component contributing approximately half of the total luminosity.

Characterization of amino acid transport in the dairy strain Leuconostoc mesenteroides subsp. mesenteroides CNRZ 1273.

To identify and characterize amino acid transport in Leuconostoc mesenteroides. The transport of labelled amino acids was measured in whole cells of Leuc. mesenteroides CNRZ 1273. Systems were operative under physiological conditions of growth, energy dependent and differed from peptide transport. Some of the systems were shared by several amino acids. Kinetic analysis indicated the presence of three transport systems with very high (VH), high (H) and low affinity (H) for the 11 amino acids studied. The K(t) values (micromol l(-1)) ranged from 0.088 to 0.815 (VH), 6-390 (H) and 320-4500 (L) and the V(max) values [nmol s(-1) (g dry weight)(-1)] from 0.015 to 0.8 (VH), 15-95 (H) and 90-470 (L). The study showed the presence of three transport systems in Leuc. mesenteroides for all amino acids tested, some of them being shared by several amino acids. The findings are discussed with reference to the growth of Leuc. mesenteroides in milk as pure or in mixed-strain culture with Lactococcus lactis.

Risk assessment and prediction of rebleeding in bleeding gastroduodenal ulcer.

The aims of this study were to identify risk factors for recurrence of hemorrhage in bleeding gastroduodenal ulcers after endoscopic injection therapy, and to develop a simple and relevant prognostic score which could be used to assess the early risk of recurrence and the residual risk of rebleeding. A prospective study was conducted from January 1995 to December 1998, in 738 patients who were admitted to our department for acute bleeding peptic ulcer and who underwent endoscopic examination. Ulcers with active bleeding or signs of recent bleeding were treated with injection therapy using epinephrine (1/10,000) and 1% polidocanol. Multivariate analysis revealed that liver cirrhosis, recent surgery, systolic blood pressure below 100 mmHg, hematemesis, Forrest classification, and ulcer size and site were significantly predictive variables for the recurrence of hemorrhage. Among these, Forrest classification was the most important. The overall accuracy of the predictive model was 71% (95% CI = 63 - 79%). The model showed a better sensitivity of 90% for early rebleeding (< 48 hours) than for late rebleeding (> or = 48 hours) where the sensitivity was 65 %. A prognostic score was obtained and patients were classified into four risk classes: very low (VL), low (L), high (H), and very high (VH). The rebleeding rates for the four classes were 0%, 7.9%, 31.8% and 67.9%, and the mortality rates were 5.9%, 8.6%, 13.9% and 35.7%, respectively. The residual risk of rebleeding after 48 hours was 0%, 3.3%, 10.4%, and 14.3% in the VL, L, H and VH classes, respectively. After 5 days the residual risk was under 4% in all classes. This study demonstrates that the proposed prognostic score, which is easily obtained after emergency endoscopy, is useful in clinical practice because it can identify patients with different levels of rebleeding risk. It can be helpful in patient management and decision making for discharge.

Bone marrow transplantation versus chemotherapy in the treatment of very high–risk childhood acute lymphoblastic leukemia in first remission: results from Medical Research Council UKALL X and XI

The role of bone marrow transplantation (BMT) in first remission of children with high-risk acute lymphoblastic leukemia (ALL) remains unclear. There were 3676 patients (aged 1 to 15 years) entered into the United Kingdom (UK) Medical Research Council (MRC) trials UKALL X and XI from 1985 to 1997. Of these patients, 473 patients (13%) were classified as very high (VH) risk and were eligible for a transplantation from a matched histocompatible sibling donor (MSD). We tissue-typed 286 patients; 99 patients had a matched related donor, and 76 patients received transplantations. Additionally, 25 children received transplantations from a matched unrelated donor (MUD) despite trial guidelines for MSD transplantations only. The median time to transplantation was 5 months (range, 2 to 19 months), and the median follow-up was 8 years. The 10-year event-free survival (EFS) adjusted for the time to transplantation, diagnostic white blood cell (WBC) count, Ph chromosome status, and ploidy was 6.0% higher (95% confidence interval (CI), −10.5% to 22.5%) for 101 patients who received a first-remission transplantation (MSD and MUD) than for the 351 patients treated with chemotherapy (transplantation, 45.3%, vs chemotherapy, 39.3%). The transplantation group had fewer relapses (31%) compared to relapses in the chemotherapy group (55%); however, the transplantation group had more remission deaths (18%) compared to remission deaths in the chemotherapy group (3%). In contrast the adjusted 10-year EFS was 10.7% higher (95% CI, −2.6% to 24.0%) for patients without a human leukocyte antigen (HLA)–matched donor than for those patients with a donor (no donor, 50.4%, vs donor, 39.7%). In conclusion, for the majority of children with VH-risk ALL, the first-remission transplantation has not improved EFS.

Bone marrow transplantation versus chemotherapy in the treatment of very high–risk childhood acute lymphoblastic leukemia in first remission: results from Medical Research Council UKALL X and XI

AbstractThe role of bone marrow transplantation (BMT) in first remission of children with high-risk acute lymphoblastic leukemia (ALL) remains unclear. There were 3676 patients (aged 1 to 15 years) entered into the United Kingdom (UK) Medical Research Council (MRC) trials UKALL X and XI from 1985 to 1997. Of these patients, 473 patients (13%) were classified as very high (VH) risk and were eligible for a transplantation from a matched histocompatible sibling donor (MSD). We tissue-typed 286 patients; 99 patients had a matched related donor, and 76 patients received transplantations. Additionally, 25 children received transplantations from a matched unrelated donor (MUD) despite trial guidelines for MSD transplantations only. The median time to transplantation was 5 months (range, 2 to 19 months), and the median follow-up was 8 years. The 10-year event-free survival (EFS) adjusted for the time to transplantation, diagnostic white blood cell (WBC) count, Ph chromosome status, and ploidy was 6.0% higher (95% confidence interval (CI), −10.5% to 22.5%) for 101 patients who received a first-remission transplantation (MSD and MUD) than for the 351 patients treated with chemotherapy (transplantation, 45.3%, vs chemotherapy, 39.3%). The transplantation group had fewer relapses (31%) compared to relapses in the chemotherapy group (55%); however, the transplantation group had more remission deaths (18%) compared to remission deaths in the chemotherapy group (3%). In contrast the adjusted 10-year EFS was 10.7% higher (95% CI, −2.6% to 24.0%) for patients without a human leukocyte antigen (HLA)–matched donor than for those patients with a donor (no donor, 50.4%, vs donor, 39.7%). In conclusion, for the majority of children with VH-risk ALL, the first-remission transplantation has not improved EFS.

Reduction of threading dislocations in GaAs on Si by the use of intermediate GaAs buffer layers prepared under high V–III ratios

We have shown that the insertion of a GaAs layer prepared by organometallic vapor phase epitaxy under very high (VH) V–III ratios into a GaAs/Si epitaxial structure improves its crystallinity after thermal cycle annealing (TCA). The PL intensity of the upper GaAs epilayer with the VH-V/III GaAs intermediate buffer layer is found to be larger than that with a normal GaAs layer. It is also observed in cross-sectional TEM that the number of through dislocations is smaller for the sample with this novel buffer layer and most threading dislocations are confined to below the buffer layer after TCA, which is in good agreement with the PL result. We tentatively attribute the origin of this improvement of the GaAs/Si epilayer to an increased concentration of Ga vacancies which will migrate and relieve the tensile stress.

DO HEMODYNAMIC ABNORMALITIES INFLUENCE MORTALITY AND LENGTH OF STAY IN NONCARDIAC SURGERY?

S98 INTRODUCTION: Although blood pressure and heart rate are closely monitored during surgery, relatively little is known about the influence of abnormalities of heart rate and blood pressure upon outcome indicators, such as mortality and length of stay. METHODS: Subjects were drawn from a group of patients undergoing an IRB-approved anesthesia outcome study. For 931 patients undergoing noncardiac surgery, the computerized anesthesia record was retrieved and intraoperative heart rate (HR), mean arterial pressure (MAP), and systolic arterial pressure (SAP) were obtained. For every five minute epoch during the surgery, HR, MAP, and SAP were classified as very low (VL), low (L), normal (N), high (H), and very high (VH), according to criteria derived from the results of a survey of 39 anesthesiologists. For the length of stay analysis, the study cohort was evenly divided into short and long surgery groups using the median number of total epochs (43) as the cutoff point. Chi-square tables were used to test for associations among hemodynamic abnormalities, mortality, and length of stay. RESULTS: There were no significant associations between hemodynamic abnormalities in shorter cases and length of stay. In longer cases, we found a statistically significant difference in length of stay in those patients with very high MAP (p=0.00001), very low SAP (p=0.04), and very high SAP (p=0.002). The results of the analysis of hospital mortality are shown in Table 1.Table 1: P-values for chi-square tests of association between hemodynamic abnormalities and hospital mortalityDISCUSSION: Extremes of blood pressure are associated with increased length of stay in longer (more complex) surgery. In addition, high heart rates and hypotension are associated with hospital mortality independent of the duration of the surgery. A multivariate analysis is being conducted to determine whether these findings are independent of known perioperative risk factors.

Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices

One of the scientific success stories of fusion research over the past decade is the development of the E×B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high) mode to VH (very high) mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with E×B velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of E×B shear on the growth, radial extent, and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number of ways to change the radial electric field Er. An important theme in this area is the synergistic effect of E×B velocity shear and magnetic shear. Although the E×B velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of E×B velocity shear and facilitate turbulence stabilization. Considerable experimental work has been done to test this picture of E×B velocity shear effects on turbulence; the experimental results are generally consistent with the basic theoretical models.

Theory of drift waves in the presence of parallel and perpendicular flow curvature. I. Slab model

It has recently [S. Sen and M. G. Rusbridge, Phys. Plasmas 2, 2705 (1995)] been shown that, contrary to the usual belief, parallel flow curvature (V∥″) can stabilize drift-like microinstabilities. Here the earlier work is extended to include the effect of the perpendicular flow curvature (V⊥″), which is known to have a stabilizing role on the drift-like microinstabilities. The full analytic stability analysis shows that the ratio of the stabilizing influences of the perpendicular to the parallel flow curvature scales as Ls/2Ln, where Ls and Ln are the magnetic shear and the density variation scale length, respectively. Thus, at the plasma edge (since Ls≫Ln) the perpendicular flow may play a crucial role in stabilizing microinstabilities and turbulence in the improved regimes of confinement [like the high (H) modes]. However, in the core confinement improvement [like the very high (VH) mode] both the parallel and the perpendicular flow curvatures are important, since Ls∼2Ln. Furthermore, as the confinement improvement in the core is usually related to the toroidal velocity and since V∥ coming from the toroidal flow is much more than V⊥ (V⊥∼εV∥, here ε is the inverse aspect ratio), this implies that it is the parallel component of the toroidal flow and not the perpendicular component, as is usually thought, which is responsible for the core confinement improvement.

Flow shear induced fluctuation suppression in finite aspect ratio shaped tokamak plasma

The suppression of turbulence by the E×B flow shear and parallel flow shear is studied in an arbitrary shape finite aspect ratio tokamak plasma using the two point nonlinear analysis previously utilized in a high aspect ratio tokamak plasma [Phys. Plasmas 1, 2940 (1994)]. The result shows that only the E×B flow shear is responsible for the suppression of flute-like fluctuations. This suppression occurs regardless of the plasma rotation direction and is, therefore, relevant for the very high (VH) mode plasma core as well as for the high (H) mode plasma edge. Experimentally observed in–out asymmetry of fluctuation reduction behavior can be addressed in the context of flux expansion and magnetic field pitch variation on a given flux surface. The adverse effect of neutral particles on confinement improvement is also discussed in the context of the charge exchange induced parallel momentum damping.

Recent results from the DIII-D tokamak and implications for future devices

Abstract Improvements to the DIII-D tokamak have led to significant new research results and enhanced performance of the tokamak systems. These results provide important inputs to the design of next-generation divertor systems including the upgrade of the DIII-D divertor. Key results have been obtained in understanding the divertor configuration and developing effective configurations for new devices. The use of graphite for the plasma facing components and careful wall preparation has enabled the routine achievement of regimes of enhanced energy confinement. In elongated discharges, triangularity has been found to be important in attaining good discharge performance as measured by the product of the normalized plasma pressure and the energy confinement time βτ E . This constrains the design of the divertor configuration (X-point location). Active pumping of the divertor region using an in-situ toroidal cryogenic pump has demonstrated control of the plasma density in H-mode discharges and allowed the dependence of confinement on plasma density and current to be separately determined. Helium removal from the plasma edge sufficient to achieve effective ash removal in reactor discharges has also been demonstrated using this pumping configuration. The reduction of the heat flux to the divertor plates has been demonstrated using two different techniques to increase the radiation in the boundary regions of the plasma and thus to reduce the heat flux to the divertor plates; deuterium gas injection has been used to create a strongly radiating localized zone near the X point, and impurity (neon) injection to enhance the radiation from the plasma mantle. Precise shaping of the plasma current profile has been found to be important in achieving enhanced tokamak performance. Transiently shaped current profiles have been used to demonstrate regimes of plasmas with high β and good confinement. Control of the current profile also is important to sustaining the plasma in the very high (VH) mode of energy confinement. Ongoing and planned enhancements to the DIII-D tokamak systems will allow us to exploit these gains further. The recent upgrade of the ICRF system to 6 MW should allow sufficient current drive to begin independent control of the plasma current. Work is beginning on a radiative divertor modification to the vessel interior which will combine the desirable features of highly triangular plasma shape with strong pumping and baffling to minimize the back-streaming of gas and impurities.

Erratum: ‘‘Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIII-D tokamak’’ [Phys. Plasmas 1, 1536 (1994)

Erratum: ‘‘Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIII-D tokamak’’ [Phys. Plasmas <b>1</b>, 1536 (1994)

Overview of high performance H-modes in JET

An account is given of the high performance plasmas established by development of the H-mode regime in JET in the experimental campaigns up to 1992. High performance in this case is measured in terms of the confinement enhancement achieved over the L-mode scaling as measured using the plasma diamagnetism. Three JET H-mode regimes have achieved enhancement factors (HGDIA) over Goldston L-mode scaling of 2.5<HGDIA<4.0. These are the Pellet Enhanced Performance (PEP) H-mode, the high bootstrap fraction (high beta POL) H-mode and the Hot Ion (HI) H-mode. The phenomenology of these three regimes is reviewed and contrasts and common threads are elucidated. All the regimes are transient (on a resistive diffusion timescale) and the mechanisms terminating the period of enhanced confinement are discussed. Common features between the high beta POL and HI regimes are identified which suggest that they are effectively two aspects of a unified Very High (VH) confinement regime. The experimental conditions for accessing this regime are reviewed.

Role of the radial electric field in the transition from L (low) mode to H (high) mode to VH (very high) mode in the DIII-D tokamak*

The hypothesis of stabilization of turbulence by shear in the E×B drift speed successfully predicts the observed turbulence reduction and confinement improvement seen at the L (low)–H (high) transition; in addition, the observed levels of E×B shear significantly exceed the value theoretically required to stabilize turbulence. Furthermore, this same hypothesis is the best explanation to date for the further confinement improvement seen in the plasma core when the plasma goes from the H mode to the VH (very high) mode. Consequently, the most fundamental question for H-mode studies now is: How is the electric field Er formed? The radial force balance equation relates Er to the main ion pressure gradient ∇Pi, poloidal rotation vθi, and toroidal rotation vφi. In the plasma edge, observations show ∇Pi and vθi are the important terms at the L–H transition, with ∇Pi being the dominant, negative term throughout most of the H mode. In the plasma core, Er is primarily related to vφi. There is a clear temporal and spatial correlation between the change in E×B shear and the region of local confinement improvement when the plasma goes from the H mode to the VH mode. Direct manipulation of the vφi and E×B shear using the drag produced by a nonaxisymmetric magnetic perturbation has produced clear changes in local transport, consistent with the E×B shear stabilization hypothesis. The implications of these results for theories of the L–H and H–VH transitions will be discussed.

Feeding value for finishing pigs of silage effluent with a high initial pH

SUMMARYSilage effluents with pH values of 4·1, 4·7 and 5·1 (normal (N), high (H) and very high (VH), respectively) were treated with hydrochloric acid to bring the pH of each effluent to 40. The effluents were offered to finishing pigs in a randomized block experiment (November 1983 to February 1984 at the Agricultural Research Institute of Northern Ireland) with dietary treatments which comprised a control diet in which meal was given to a standard scale of feeding, or effluent diets N, H and VH, in which the effluent was substituted on a dry matter basis for 150g/kg of the standard scale of feeding. In a negative control diet, meal was offered at 850 g/kg of the control diet. Water or effluent as appropriate was given on the meal, and water was also available ad libitum. A total of 60 pigs was used with mean initial and final live weights (LW) of 37·1 and 86·4 kg, respectively.Effluents H and VH had higher ammonia N: total N and lower amino acid N: total N and lactic acid contents than effluent N. The rates of LW gain, feed conversion ratios, backfat thicknesses and the proportions of lean and fat in the ham joint were similar for the control diet and effluent diets N and H, indicating a similar nutritive value for all three. Effluent diet VH gave a significantly (P &lt; 0·01) reduced rate of LW gain and poorer feed conversion ratio than diets N and H. While diet VH was consumed reluctantly with widespread refusals (mean refusal 28 g DM/kg DM offered), the feed refusals together with the lower lysine and threonine contents of the effluent would not have produced the observed degree of deterioration in growth and feed conversion. Possible reasons for the lower nutritive value are undetectable wastage of feed or the presence of an antinutritional factor in effluent VHG, or a combination of both factors.

Some further observations upon the effects of varying the plane of feeding for pigs between weaning and bacon weight

Some further observations upon the effects of varying the plane of feeding for pigs between weaning and bacon weight