Seeding the Electrothermal Instability through a Three-Dimensional, Nonlinear Perturbation

Electrothermal instability plays an important role in applications of current-driven metal, creating striations (which seed the magneto-Rayleigh-Taylor instability) and filaments (which provide a more rapid path to plasma formation). However, the initial formation of both structures is not well understood. Simulations show for the first time how a commonly occurring isolated defect transforms into the larger striation and filament, through a feedback loop connecting current and electrical conductivity. Simulations have been experimentally validated using defect-driven self-emission patterns.

Three-dimensional feedback processes in current-driven metal

Using three-dimensional (3D) magnetohydrodynamic simulations, we study how a pit on a metal surface evolves when driven by intense electrical current density j. Redistribution of j around the pit initiates a feedback loop: j both reacts to and alters the electrical conductivity σ, through Joule heating and hydrodynamic expansion, so that j and σ are constantly in flux. Thus, the pit transforms into larger striation and filament structures predicted by the electrothermal instability theory. Both structures are important in applications of current-driven metal: The striation constitutes a density perturbation that can seed the magneto-Rayleigh-Taylor instability, while the filament provides a more rapid path to plasma formation, through 3D j redistribution. Simulations predict distinctive self-emission patterns, thus allowing for experimental observation and comparison.

Harmonic Generation and Inverse Cascade in the z-Pinch Driven, Preseeded Multimode, Magneto-Rayleigh-Taylor Instability

The magneto-Rayleigh-Taylor instability (MRTI) plays an essential role in astrophysical systems and in magneto-inertial fusion, where it is known to be an important degradation mechanism of confinement and target performance. In this Letter, we show for the first time experimental evidence of mode mixing and the onset of an inverse-cascade process resulting from the nonlinear coupling of two discrete preseeded axial modes (400- and 550-μm wavelengths) on an Al liner that is magnetically imploded using the 20-MA, 100-ns rise-time Z Machine at Sandia National Laboratories. Four radiographs captured the temporal evolution of the MRTI. We introduce a novel unfold technique to analyze the experimental radiographs and compare the results to simulations and to a weakly nonlinear model. We find good quantitative agreement with simulations using the radiation magnetohydrodynamics code hydra. Spectral analysis of the MRTI time evolution obtained from the simulations shows evidence of harmonic generation, mode coupling, and the onset of an inverse-cascade process. The experiments provide a benchmark for future work on the MRTI and motivate the development of new analytical theories to better understand this instability.

Experimental Demonstration of the Stabilizing Effect of Dielectric Coatings on Magnetically Accelerated Imploding Metallic Liners

Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70  μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=Rin,0/Rin(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. The inner-wall radius Rin(z,t) displayed unprecedented uniformity, varying from 95 to 130  μm over the 4.0 mm axial height captured by the radiograph.

Observations of modified three-dimensional instability structure for imploding z-pinch liners that are premagnetized with an axial field

Novel experimental data are reported that reveal helical instability formation on imploding z-pinch liners that are premagnetized with an axial field. Such instabilities differ dramatically from the mostly azimuthally symmetric instabilities that form on unmagnetized liners. The helical structure persists at nearly constant pitch as the liner implodes. This is surprising since, at the liner surface, the azimuthal drive field presumably dwarfs the axial field for all but the earliest stages of the experiment. These fundamentally 3D results provide a unique and challenging test for 3D-magnetohydrodynamics simulations.

Measurements of magneto-Rayleigh-Taylor instability growth during the implosion of initially solid Al tubes driven by the 20-MA, 100-ns Z facility

The first controlled experiments measuring the growth of the magneto-Rayleigh-Taylor instability in fast (∼100  ns) Z-pinch plasmas are reported. Sinusoidal perturbations on the surface of an initially solid Al tube (liner) with wavelengths of 25-400  μm were used to seed the instability. Radiographs with 15  μm resolution captured the evolution of the outer liner surface. Comparisons with numerical radiation magnetohydrodynamic simulations show remarkably good agreement down to 50  μm wavelengths.

Acute anti-emetic withdrawal associated with a hemorrhagic cerebellar arteriovenous malformation

We present a 67-year-old right-handed male with a brachium pontis arteriovenous malformation on continuous anti-emetic therapy who demonstrated acute withdrawal symptoms after the abrupt discontinuation of ondansetron, a 5-HT(3) receptor antagonist. Removal of anti-emetic therapy led to the development of extreme flushing and tremor, but subsequent return of ondansetron resulted in the resolution of these symptoms. This is the first clinical report demonstrating acute withdrawal from an anti-emetic agent and we further highlight the need for future studies evaluating not only arterial supply with pressure gradients and anatomical location, but also the association with periventricular venous drainage, venous drainage stenosis, and mass effect from venous stasis as this may contribute partly to the sensitivity of the serotonergic receptors seen here.

The gender specificity of emotional, situational, and behavioral indicators of binge eating in a diet-seeking obese population

OBJECTIVE

This study investigated the unique gender correlates of binge eating severity in a diet-seeking population.

METHOD

This sample consisted of 288 self-admitted patients enrolled in a residential weight loss program between 1996 and 1997. Subjects were administered several questionnaires including (a) the Binge Eating Scale, (b) the Beck Depression Inventory, (c) the Rosenberg Self-Esteem Scale, (d) 5-point scales of eating related foci, and (e) 7-point scales of subject confidence in controlling their eating under various circumstances. Data were analyzed in terms of stepwise regression analyses.

RESULTS

Regression results revealed that while men and women share some common predictors of binge eating severity, there are also some gender-specific correlates. Men in our sample were prone to binge eat because of negative emotions (i.e., depression and anger), while binge eating severity for women in our sample was most strongly related to diet failure and tests of moderate eating.

DISCUSSION

The strength of the distinctive gender-specific regressions for binge eating severity suggests that the problems of binging in obese males and females are derivatives of differential sex role expectations. This interpretation and clinical implications are the focus of the discussion.

Mutations in the gene encoding starch synthase II profoundly alter amylopectin structure in pea embryos

Mutations at the rug5 (rugosus5) locus have been used to elucidate the role of the major soluble isoform of starch synthase II (SSII) in amylopectin synthesis in the developing pea embryo. The SSII gene maps to the rug5 locus, and the gene in one of three rug5 mutant lines has been shown to carry a base pair substitution that introduces a stop codon into the open reading frame. All three mutant alleles cause a dramatic reduction or loss of the SSII protein. The mutations have pleiotropic effects on the activities of other isoforms of starch synthase but apparently not on those of other enzymes of starch synthesis. These mutations result in abnormal starch granule morphology and amylopectin structure. Amylopectin contains fewer chains of intermediate length (B2 and B3 chains) and more very short and very long chains than does amylopectin from wild-type embryos. The results suggest that SSII may play a specific role in the synthesis of B2 and B3 chains of amylopectin. The extent to which these findings can be extrapolated to other species is discussed.

Mutations in the gene encoding starch synthase II profoundly alter amylopectin structure in pea embryos

Mutations at the rug5 (rugosus5) locus have been used to elucidate the role of the major soluble isoform of starch synthase II (SSII) in amylopectin synthesis in the developing pea embryo. The SSII gene maps to the rug5 locus, and the gene in one of three rug5 mutant lines has been shown to carry a base pair substitution that introduces a stop codon into the open reading frame. All three mutant alleles cause a dramatic reduction or loss of the SSII protein. The mutations have pleiotropic effects on the activities of other isoforms of starch synthase but apparently not on those of other enzymes of starch synthesis. These mutations result in abnormal starch granule morphology and amylopectin structure. Amylopectin contains fewer chains of intermediate length (B2 and B3 chains) and more very short and very long chains than does amylopectin from wild-type embryos. The results suggest that SSII may play a specific role in the synthesis of B2 and B3 chains of amylopectin. The extent to which these findings can be extrapolated to other species is discussed.

Indicators of effective cytological sampling of the uterine cervix

A case-control comparison of adequate and inadequate cervical smears (adequacy being defined as the successful detection of cervical intraepithelial neoplasia and inadequacy as the failure to do so when disease was almost certainly present) was undertaken to determine whether indicators of effective cytological sampling could be identified. The association between inadequate smears and the absence of two types of normal epithelial cells (columnar cells of endocervical origin and immature metaplastic cells) was measured. A significant and substantial association was found between inadequate cervical smears and immature metaplastic cells and between inadequate smears and both types of cell. Endocervical cells alone were less likely to be found in inadequate than in adequate smears, but this association was not statistically significant.

The estimation of dietary protein intake in chronic renal failure

Forty-five adult clinic patients with chronic renal failure each supplied a 4-day weighed dietary record, a 24-h urine collection, and a nocturnal spot urine sample. Total nitrogen (N) losses derived from the urines were corrected for proteinuria and non-urea nitrogen excretion. Individual estimates of N intake were compared by correlation and assessing the level of agreement. Daily urea N excretion derived from the spot sample correlated well with the 24-h collection P less than 0.001, but the degree of agreement was poor, mean difference being +1.62 g with 95% limits of +5.7 to -2.47 g. The correlation between the spot-sample-derived N loss and dietary N intake was poor, r = 0.42; P less than 0.05. For 12 patients taking a low-protein diet, N intake correlated well with 24-h urine derived N losses, P less than 0.001, mean difference being +0.59 g, 95% limits +2.39 to -1.21 g. The correlation and agreement was less satisfactory for the subjects who had not received dietary instruction, due largely to individual variation in day-to-day protein intake. Use of spot urine samples is too inaccurate for routine clinical practice. Single 24-h urine derived estimates of N intake are only of value for assessing patients previously prescribed a low-protein intake.

Markers of the nutritional status in acutely ill elderly patients

We recorded anthropometric and laboratory data in 98 sick old people on admission to a high-dependency unit. The measurement of triceps skinfold thickness and arm muscle area was feasible even in very ill people, while measurement of the body mass index was difficult and sometimes unreliable. Anthropometric measurements indicated that our study group was better nourished than a local population, with just 3 subjects (3%) being fat depleted and a further 4 (5%) being protein depleted. Serum albumin was the laboratory variable that correlated best with anthropometric parameters. However, it was low in 47% of the subjects, indicating that its lower reference value needs to be redefined in this select group.

Significance of single serum urate estimations in acutely hospitalized elderly patients

Clinical, pharmacological and biochemical correlates of hyperuricaemia were studied in 399 consecutive patients aged over 70 years admitted to hospital with acute medical illness. Hyperuricaemia was significantly related to renal impairment and to the use of diuretics, but to no other recognized associations of gout, including typical or atypical joint symptoms. 'Routine' measurement of serum uric acid alone or as a component of biochemical profiles in acute illness in the elderly appears unjustified, particularly since raised levels may encourage inappropriate use of urate-lowering therapy.

Proteinuria in autoimmune thyroid disease

We have investigated the prevalence of proteinuria in patients with Graves' disease and chronic autoimmune thyroiditis attending a routine thyroid clinic. Using the urine protein creatinine index, proteinuria was found in 29.8% of patients with autoimmune thyroid disease and in 9.5% of patients attending the same clinic but without these conditions. When patients with Graves' disease were treated with 131I, proteinuria measured by 24 h collections developed in 9 of 14 patients without pre-existing proteinuria and appeared to diminish in 4 patients in whom proteinuria had been present before treatment. The prevalence and fluctuation of proteinuria was independent of thyroglobulin and microsomal antibody levels. We were unable to confirm previous reports of a high prevalence of circulating immune complexes in autoimmune thyroid disease; complexes were detected in only 7.9% of patients and did not correlate with proteinuria. The causes of mild proteinuria in autoimmune thyroid disease are not apparent, but previous case reports suggesting that membranous glomerulonephritis is associated with Graves' disease, albeit rarely, indicate that immunological mechanisms may be implicated.

Morphological changes and pathology of mouse glomeruli infected with a streptococcal L-form or exposed to lipoteichoic acid

The morphology and pathology of cultured mouse glomeruli were examined at the cellular and subcellular levels after infection with a physiological isotonic L-form of Streptococcus pyogenes type 12 or exposure to streptococcal lipoteichoic acid. These changes, as viewed by light microscopy, were identical regardless of the method used to induce glomerular cytotoxicity. They were characterized by an initial reduction in the outgrowth of cells, some cellular granulation, and later, destruction of the confluent monolayer. Once initiated, cytotoxicity could not be reversed by refeedings, and complete glomerular destruction resulted after 2 weeks. Electron microscope studies revealed that the basement membrane of intact glomeruli exposed to streptococcal lipoteichoic acid had become greatly thickened (two- to fourfold) and electron dense. Our recent biochemical findings have shown that streptococcal lipoteichoic acid increases the amount of collagen formed and retained by mouse fibroblasts in tissue culture as well as causing a reduction in the hydroxylation of proline in both intracellular and secreted collagenous material (Leon and Panos, Infect. Immun. 40:785-794, 1983). These results, together with the present findings, suggest that the thickening of the glomerular basement membrane may be due to defective collagen biosynthesis as a result of streptococcal lipoteichoic acid. The use of cultured glomeruli as a model system for studying the earliest basement membrane alterations in the absence of an immune response as a result of streptococcal lipoteichoic acid is suggested.