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T Epstein

Publications and source records attributed to T Epstein.

6 recordsLinked to original sources

Grid states and nonlinear selection in parametrically excited surface waves.

Interacting surface waves, parametrically excited by two commensurate frequencies (Faraday waves), yield a rich family of nonlinear states, which result from a variety of three-wave resonant interactions. By perturbing the system with a third frequency, we selectively favor different nonlinear wave interactions. Where quadratic nonlinearities are dominant, the only observed patterns correspond to "grid" states. Grid states are superlattices in which two corotated sets of critical wave vectors are spanned by a sublattice whose basis states are linearly stable modes. Specific driving phase combinations govern the selection of different grid states.

Journal Article↗

Control of spatiotemporal disorder in parametrically excited surface waves.

Interacting surface waves, parametrically excited by two commensurate frequencies, yield a number of nonlinear states. Near the system's bicritical point, a state, highly disordered in space and time, results from competition between nonlinear states. Experimentally, this disordered state can be rapidly stabilized to a variety of nonlinear states via open-loop control with a small-amplitude third frequency excitation, whose temporal symmetry governs the temporal and the spatial symmetry of the selected nonlinear state. This technique also excites rapid switching between nonlinear states.

Journal Article↗

Mesenteric and portal vein gas: computerized tomography findings and clinical significance.

BACKGROUND: Gas in the mesenteric or portal veins (PVG) is an uncommon entity. It was first described only in patients with mesenteric ischemia and bowel gangrene. Later, several reports described other causes for PVG in which conservative treatment was successful. In the past, the diagnosis was made by vague signs in abdominal plain films. Since the era of computerized tomography (CT) scan the diagnosis became more objective, but nevertheless it is still an elusive entity. Our objective was to relate clinical and CT findings with outcome of patients with PVG, and to determine the indications for surgical treatment. METHODS: Six-year records of patients from one general hospital with CT scan findings of gas in the mesenteric or portal veins were retrospectively studied, together with details of the clinical presentation, hospital course and outcome. RESULTS: Between 1995 and 2000, 12 patients with findings of mesenteric and portal vein gas were identified. In 7 of 12 patients (58%) PVG developed secondary to ischemia of the small or large bowel, with mortality of 86%. Metabolic acidosis was the prominent laboratory finding. Pneumatosis intestinalis was present in all of these patients. Two patients with PVG had inflammatory bowel disease and both recovered with conservative management. Another 2 patients who were treated conservatively died. One patient had severe pancreatitis and died 2 weeks after PVG was diagnosed, from septic complications, while the other patient admitted with septic shock, died of multiorgan failure. In the last patient, PVG was diagnosed in a CT scan performed to investigate fever of unknown origin. She survived with no specific treatment. CONCLUSION: We suggest that patients in whom PVG is found by CT scan should be treated according to their clinical status, and underlying disease. Patients suspected of having an ischemic mesenteric event should be immediately explored.

Adult↗

Bladder cooling reflex in patients with multiple sclerosis.

PURPOSE: We describe the effect of intravesical ice water instillation in patients with multiple sclerosis and without an overactive bladder. MATERIALS AND METHODS: Of 131 consecutive patients with multiple sclerosis who presented with a urinary disorder we selected for study 10 men and 29 women with a mean age plus or minus standard deviation of 50 +/- 9 years who had multiple sclerosis without an overactive bladder. Nonoveractive bladder was defined as no involuntary detrusor contraction up to 400 ml. of maximum fill on routine cystometry. We performed cystometry with saline at 25 to 30C at an infusion rate of 50 and 100 ml. per minute, and with ice water at 0 to 4C at a rate of 100 ml. per minute. Ice water cystometry was considered positive when an involuntary detrusor contraction occurred before 200, and between 200 and 400 ml. of filling. Ice water cystometry was considered negative when there was no involuntary detrusor contraction during ice water filling up to 400 ml. RESULTS: Ice water cystometry enabled us to elicit involuntary detrusor contractions in 21 patients, which remained undetected by warm water cystometry at rates of 50 and 100 ml. per minute. The test was positive before 200, and between 200 and 400 ml. in 10 and 11 cases, respectively. Positive ice water cystometry was significantly associated with irritative signs or significant post-void residual urine volume. CONCLUSIONS: An involuntary detrusor contraction was not elicited by cystometry at 50 or 100 ml. per minute, implying that the afferent mechanoreceptor reflex limb via ADelta fibers is not involved. In contrast, ice water cystometry at 100 ml. per minute elicited an involuntary detrusor contraction, suggesting involvement of an afferent reflex limb via capsaicin sensitive C fibers. These involuntary detrusor contractions revealed by ice water cystometry are probably relevant to an overactive bladder. In urinary disorders such a positive test indicates a spinal lesion. In multiple sclerosis it may have pathophysiological value, indicating a spinal rather than cerebral mechanism of overactive bladder, and diagnostic value, indicating multifocal demyelination.

Cold Temperature↗

[Use of somatostatin analogue for intestinal and pancreatic fistulas].

The hormone somatostatin, a tetra-deca-peptide, was discovered in 1972. It inhibits the central nervous system and the endocrine and exocrine secretions of the gastrointestinal tract. The first clinical use of the hormone was to inhibit hormone-secreting tumors of the CNS. It has also been used to treat hormone-secreting tumors of the pancreas and GI tract. Treatment of small bowel and pancreatic fistulas has also been attempted. A new synthetic analogue of the hormone, SMS 210-995, (Sandostatin) has a long half-life and is highly effective after subcutaneous injection. It was used in the treatment of 3 patients with fistulas of the small bowel and pancreas. In all impressive reduction of fistula secretion was achieved within 24 hours. In 2 there was complete, spontaneous closure of the fistula: in 1 after 10 days and in the other after 15 days of treatment. In the 3rd, there was significant reduction of fistula output. There were no side-effects except for mild pain at the injection site in 1 patient. Previous reports and our own results indicate that this somatostatin analogue may be very useful in the nonsurgical treatment of GI tract fistulas.

Aged↗