Evolution of a collapsing and exploding Bose-Einstein condensate in different trap symmetries

Based on the time-dependent Gross-Pitaevskii equation we study the evolution of a collapsing and exploding Bose-Einstein condensate in different trap symmetries to see the effect of confinement on collapse and subsequent explosion, which can be verified in future experiments. We make a prediction for the evolution of the shape of the condensate and the number of atoms in it for different trap symmetries (cigar to pancake) as well as in the presence of an optical lattice potential. We also make a prediction for the jet formation in different cases when the collapse is suddenly terminated by changing the scattering length to zero via a Feshbach resonance. In addition to the usual global collapse to the center of the condensate, in the presence of an optical-lattice potential one could also have in certain cases independent collapse of parts of the condensate to local centers, which could be verified in experiments.

Dynamics of collapsing and exploding Bose-Einstein condensate

Recently, Donley et al. performed an experiment on the dynamics of collapsing and exploding Bose-Einstein condensates by suddenly changing the scattering length of atomic interaction to a large negative value on a preformed repulsive condensate of Rb-85 atoms in an axially symmetric trap. Consequently, the condensate collapses and ejects atoms via explosions, We show that the accurate numerical solution of the time-dependent Gross-Pitaevskii equation with axial symmetry can explain some aspects of the dynamics of the collapsing condensate. (C) 2002 Published by Elsevier B.V. B.V.

Chaos in collapsing Bose-condensed gas

We reinvestigate the dynamics of the grow and collapse of Bose-Einstein condensates in a system of trapped ultracold atoms with negative scattering lengths, and found a new behavior in the long time scale evolution: the number of atoms can go far beyond the static stability limit. The condensed state is described by the solution of the time-dependent nonlinear Schrödinger equation, in a model that includes atomic feeding and three-body dissipation. Our results for the model show that, by changing the feeding parameter and when a substantial depletion of the ground-state exists, a chaotic behavior is found. We consider a criterion proposed by Deissler and Kaneko [Phys. Lett. A 119, 397 (1987)] to diagnose spatiotemporal chaos. ©2000 The American Physical Society.

Mean-field description of collapsing and exploding Bose-Einstein condensates

Numerical simulations based on the time-dependent mean-field Gross-Pitaevskii equation was performed to explain the dynamics of collapsing and exploding Bose-Einstein condensates (BEC) of 85Rb atoms. The atomic interaction was manipulated by an external magnetic field via a Feshbach resonance. On changing the scattering length of atomic interaction from a positive to a large negative value, the condensate collapsed and ejected atoms via explosion.

Dynamics of a collapsing and exploding Bose-Einstein condensed vortex state

The dynamics of small repulsive Bose-Einstein condensed vortex states of 85Rb atoms in a cylindrical traps with low angular momentum was studied. The time-dependent mean-field Gross-Pitaevskii equation was used for the study. The condensates collapsed and atoms ejected via explosion and a remnant condensate with a smaller number of atoms emerges that survived for a long time.

Mean-field model of jet formation in a collapsing Bose-Einstein condensate

We perform a systematic numerical study, based on the time-dependent Gross-Pitaevskii equation, of jet formation in collapsing and exploding Bose-Einstein condensates as in the experiment by Donley et al (2001 Nature 412 295). In the actual experiment, via a Feshbach resonance, the scattering length of atomic interaction was suddenly changed from positive to negative on a pre-formed condensate. Consequently, the condensate collapsed and ejected atoms via explosion. On disruption of the collapse by suddenly changing the scattering length to zero, a radial jet of atoms was formed in the experiment. We present a satisfactory account of jet formation under the experimental conditions and also make predictions beyond experimental conditions which can be verified in future experiments.

Schwarzschild generalized black hole horizon and the embedding space

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dynamics of Bose-Einstein condensates with atomic pumping and dissipative processes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spherical collapse in chameleon models

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alterações morfológicas e funcionais dos rins de cães com insuficiência renal crônica

Alterações morfológicas de 11 casos de cães com insuficiência renal foram caracterizadas e classificadas de acordo com os padrões estabelecidos pela Organização Mundial de Saúde para seres humanos. Glomerulonefrite esclerosante difusa foi diagnosticada em 82,0% dos animais e nefrite intersticial crônica nos 18,0% restantes. Os tipos e freqüência das lesões identificadas foram similares às encontradas na literatura para a insuficiência renal crônica.

Effect of long-term treatment with insulin and/or acarbose on glomerular basement membrane thickening in alloxan-diabetic rats

Acarbose is a competitive inhibitor of the intestinal alpha-glycosidases, that can delay absorption of intestinal carbohydrates causing their malabsorption. In the present paper we studied the effects of insulin, acarbose and their association on glomerular basement membrane thickening in alloxan-diabetic rats. Twenty-five male and female Wistar rats, approximately 3 months old at the beginning of the experiment, were assigned randomly to each of five experimental groups: normal control rats, alloxan-diabetic control rats, alloxan-diabetic rats treated with acarbose, alloxan-diabetic rats treated with insulin, and alloxan-diabetic rats treated with insulin plus acarbose. Alloxan was administered in a single iv dose of 42 mg/kg body weight. Insulin was given subcutaneously at doses of 18 to 30 IU/kg corrected daily on the basis of glycosuria and ketonuria. Acarbose was given mixed with rat chow in a dose of 50 mg/100 g chow. Body weight, water and food intake and diuresis, as well as blood and urine glucose were determined after 1, 3, 6, 9, and 12 months of treatment. Glomerular basement membrane (GBM) thickening was determined by electron microscopy at the same times. Clear clinical and laboratory signs of severe diabetes, with blood glucose levels above 200 mg/dl and urine glucose above 3000 mg/dl, were observed in all alloxan-diabetic control rats, in all periods of follow-up, whereas administration of insulin or acarbose reduced the blood glucose levels of treated groups. The most satisfactory control of blood and urine glucose was observed in animals treated with both insulin and acarbose. However, diarrhea was observed in diabetic rats treated with acarbose associated or not with insulin. GBM thickening was correlated with age in all groups. Beginning at six months after diabetes induction, the GBM of untreated diabetic rats was significantly thicker (mean +/- SEM, 4.446 +/- 0.45 mm) than that of normal rats (2.977 +/- 0.63 mm). Both insulin and acarbose prevented GBM thickening and their combination induced thickening similar to the age-dependent thickening observed for normal rats of the same age. We conclude that acarbose when combined with insulin may be a good option in the control of diabetes and its renal complications.

Paulista registry of glomerulonephritis: 5-year data report

Background. The Paulista Registry of Glomerulopathies was created in May 1999 and comprises several centres of São Paulo, the most populous Brazilian State, that concentrates people from all regions of the country who look for health care.Methods. This report includes data from 2086 patients from Brazil submitted to renal biopsy due to the presumed diagnosis of glomerular diseases, registered prospectively since May 1999 until January 2005. Data were collected by the integrants of the 11 centres involved, utilizing a standardized questionnaire.Results. The mean age of the patients was 34.5 +/- 14.6 years. Primary glomerular diseases were more frequent in males (55.1%) than in females; on the other hand, secondary glomerular diseases were more frequent in females (71.8%). The most common clinical presentation was nephrotic syndrome and the frequency of hypertension, at this time, was 55.5%. There was a predominance of indication of biopsies in the third, fourth and fifth decades of life. The most common primary glomerular diseases were focal and segmental glomerulosclerosis (29.7%), followed by membranous nephropathy (20.7%), IgA nephropathy (17.8%), minimal change disease (9.1%), membranoproliferative glomerulonephritis (7%), crescentic glomerulonephritis (4.1%), advanced chronic glomerulopathy (4%), non-IgA mesangial glomerulonephritis (3.8%), diffuse proliferative glomerulonephritis (2.5%), focal segmental proliferative glomerulonephritis (1%) and others (0.3%). The most frequent secondary glomerular disease was lupus nephritis, corresponding to 66.2% of the cases, followed by post-infectious glomerulonephritis (12.5%), diabetic nephropathy (6.2%), diseases associated to paraproteinaemia (4.9%), hereditary diseases (4.6%), vasculitis (3.2%), malignancies (0.9.%), secondary focal segmental glomerulosclerosis (0.6%) and others (0.9%).Conclusion. Focal segmental glomerulosclerosis was the most frequent primary glomerular disease, followed by membranous nephropathy and IgA nephropathy. Lupus nephritis predominated over all the other secondary glomerular diseases.

Radiating cylindrical collapse

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo comparativo das complicações terapêuticas no Lúpus Eritematoso Sistêmico e nas glomerulopatias idiopáticas.

PURPOSE: To evaluate the therapeutic complications due to the use of immunosupressors in patients with nephropathy. METHODS: 76 patients who had used steroids and cyclophosphamide were retrospectively studied. The cases were divided into three groups: G1= 15 patients with Systemic Lupus Erythematosus without renal lesion; G2= 33 patients with lupus nephritis and G3= 28 patients with nephrotic syndrome owing to idiopathic glomerulopathy. RESULTS: There were no differences related to time of follow up (G1= 42.4 +/- 51, G2= 52.3 +/- 51, G3= 41.8 +/- 47.8 months), total used dosage of steroids (G1= 20, G2= 28, G3= 16 grams) and time of drug use (G1= 20, G2= 26, G3= 14.5 months). About cyclophosphamide use, there was no difference in the percentage of patients who used it (13% in G1, 51% in G2, 28% in G3), but the patients from G1 received lower total dosage than those from G2 (p<0.05). Cushingoid appearance, epigastric distress, psychiatric disorders, diabetes mellitus and ocular alterations occurred in all the three groups, with no statistically significant differences. The infections complications, those considered more severe clinically, were more frequent in G2 (G1= 6%, G2= 15%, G3= 0% - p<0.05), the same occurring with the deaths (7% in G1, 30% in G2, 0% in G3 - p<0.05). CONCLUSION: In patients with lupus nephritis there were more infections complications owing to prolonged immunosuppresion what may indicate a severity marker of this type of lesion.