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At least 289 records · Page 16Linked to original sources
PubMed2003

Experimental simulation of supersonic superboom in a water tank: nonlinear focusing of weak shock waves at a fold caustic.

An accelerating supersonic aircraft produces noisy superboom due to acoustical shock wave focusing at a fold caustic. This phenomenon is modeled by the mixed-type nonlinear Tricomi equation. An innovative experimental simulation in a water tank has been carried out, with perfect similitude to sonic boom in air. In the linear regime, the canonical Airy function is reproduced using the inverse filter technique. In the nonlinear regime (weak shock waves), the experiment demonstrates the key role of nonlinear effects: they limit the field amplitude, distort the sonic line, and strongly alter the phase of the signal, in agreement with numerical simulations.

Journal Article↗
PubMed1995

Prediction of complications following caustic ingestion in adults.

The records of 86 adults admitted to hospital following caustic ingestion were reviewed. Eighteen patients (21%) developed complications; of these, six were fatal. Patients without symptoms or signs did not develop complications. Complications occurred only following lye ingestion, or intentional ingestion of hydrochloric acid or ammonia water. Of patients with such ingestion, and two signs or symptoms or more, 70% developed complications. Oesophagoscopy did not significantly improve the prediction of complications. There was a strong trend, however, for more severe complications with more severe submucosal, circumferential oesophageal injuries (P = 0.003). The study suggests that only adults with symptoms or signs following strong alkali or strong acid ingestion are at risk of complications. In adults who are symptomatic following ingestion of strong acid or alkali, oesophagoscopy is important to identify the potentially fatal transmural injuries.

Administration, Oral↗
PubMed2006

Evaluation of systemic oxidative status and mononuclear leukocytes DNA damage in children with caustic esophageal stricture.

Esophageal stricture (ES) due to accidentally caustic digestions is a common problem in children. Mucosal damage and repeated dilatations lead to chronic inflammation and finally ES. We investigated the oxidative status and DNA damage of children with ES. Five children with ES were compared with the same age- and sex-matched healthy subjects. Oxidative status of plasma was evaluated by measuring myeloperoxidase (MPO) activity, and total peroxide (TP) level. Anti-oxidative status of the plasma was evaluated by measuring catalase (CAT) activity, and total antioxidant response (TAR). We used the Single Cell Gel Electrophoresis (also called Comet Assay) to measure DNA strand break in peripheral blood mononuclear leukocytes. Mean MPO activity and TP levels in the ES group were significantly higher than the control group (0.83 +/- 0.35, 0.09 +/- 0.03 and 0.98 +/- 0.38, 0.34 +/- 0.20, P = 0.009 and P = 0.047 respectively). There was no significant difference in CAT activity and TAR levels between the two groups (P = 0.347). DNA damage in patients with ES was increased compared to control subjects (108.8 +/- 51.2 and 57.6 +/- 31.2 arbitrary units, respectively), but this difference was not significant statistically (P= 0.09). This study shows that systemic oxidative stress and alteration at the nuclear level occur in patients with ES, as a result of multiple dilatations and tissue injury. On the other hand, these results support that patients with ES may benefit from antioxidant treatment.

Burns, Chemical↗
PubMed1998

Acute colitis caused by caustic products.

We report two cases of acute proctocolitis caused by rectal application of caustic products of domestic use. One 61-yr-old woman applied an ammonia solution enema; the other patient, a 63-yr-old woman, accidentally applied an enema containing lye. Both patients presented with intense anal pain, but the first patient also had abdominal pain with guarding, hematochezia, and leucocytosis. An acute proctocolitis was found at sigmoidoscopy in both patients. Only conservative and symptomatic measures were prescribed in both cases, and a clinical and endoscopic recovery was seen. In spite of persistent fibrosis in the lamina propria, no signs of stenosis were found.

Accidents, Home↗
PubMed2003

Numerical simulation of shock wave focusing at fold caustics, with application to sonic boom.

Weak shock wave focusing at fold caustics is described by the mixed type elliptic/hyperbolic nonlinear Tricomi equation. This paper presents a new and original numerical method for solving this equation, using a potential formulation and an "exact" numerical solver for handling nonlinearities. Validation tests demonstrate quantitatively the efficiency of the algorithm, which is able to handle complex waveforms as may come out from "optimized" aircraft designed to minimize sonic booms. It provides a real alternative to the approximate method of the hodograph transform. This motivated the application to evaluate the ground track focusing of sonic boom for an accelerating aircraft, by coupling CFD Euler simulations performed around the mock-up on an adaptated mesh grid, atmospheric propagation modeling, and the Tricomi algorithm. The chosen configuration is the European Eurosup mock-up. Convergence of the focused boom at the ground level as a function of the matching distance is investigated to demonstrate the efficiency of the numerical process. As a conclusion, it is indicated how the present work may pave the way towards a study on sonic superboom (focused boom) mitigation.

Journal Article↗
PubMed2005

Nonlinear focusing of acoustic shock waves at a caustic cusp.

The present study investigates the focusing of acoustical weak shock waves incoming on a cusped caustic. The theoretical model is based on the Khokhlov-Zabolotskaya equation and its specific boundary conditions. Based on the so-called Guiraud's similitude law for a step shock, a new explanation about the wavefront unfolding due to nonlinear self-refraction is proposed. This effect is shown to be associated not only to nonlinearities, as expected by previous authors, but also to the nonlocal geometry of the wavefront. Numerical simulations confirm the sensitivity of the process to wavefront geometry. Theoretical modeling and numerical simulations are substantiated by an original experiment. This one is carried out in two steps. First, the canonical Pearcey function is synthesized in linear regime by the inverse filter technique. In the second step, the same wavefront is emitted but with a high amplitude to generate shock waves during the propagation. The experimental results are compared with remarkable agreement to the numerical ones. Finally, applications to sonic boom are briefly discussed.

Journal Article↗
PubMed1994

Composite reconstruction of the esophagus and hypopharynx after severe caustic injury.

The ingestion of caustic materials may cause burns and subsequent strictures of the esophagus. Depending on the extent of the injury, the stricture may require dilation, excision, or bypass with an esophageal replacement. There is also a risk of esophageal dysfunction, perforation, and malignancy. Here is presented a case of a burn so severe that the hypopharynx was deformed and the esophagus destroyed. Composite techniques restored complete gastrointestinal continuity while maintaining excellent swallowing function.

Adrenal Cortex Hormones↗
PubMed1985

Brain abscess after esophageal dilation for caustic stricture: report of three cases.

Of 127 patients with intracranial suppuration (brain abscess and subdural empyema) treated from 1971 to 1984, 3 were children with brain abscesses who previously had developed esophageal stricture from the ingestion of caustic substances. Each child had undergone esophageal dilation on several occasions before the development of focal neurological findings. Surgical resection of the abscess resulted in good to excellent neurological recovery in all 3 patients. Two of the patients have been followed for long periods and have developed other severe illnesses, suggesting a defective immune status. Review of the English literature provides 8 other cases of this complication of esophageal stricture, with which the reported cases are compared.

Adolescent↗
PubMed2006

Minimizing bend loss by removing material inside the caustic in bent single-mode fibers.

By removing the cladding on the outside of a bent single-mode optical fiber and exposing a surface at a radius smaller than that of the radiation caustic, the leaky nature of the propagating mode is almost suppressed, and bend loss is effectively eliminated. The practical realization of this effect is described, and a loop with a bend radius of 0.50 mm on standard telecommunications fiber is demonstrated with negligible loss.

Journal Article↗
PubMedDate not supplied

[Lesions of the gastroesophageal mucosa in patients with acute oral poisoning by non-caustic chemicals].

Pathological changes in the gastroesophageal mucosa are described, causing gastrointestinal hemorrhages in patients with acute oral poisonings with non-caustic chemicals: the Mallory-Weiss syndrome, traumatic and erosive involvement of the gastroesophageal mucosa. Analysis of esophagogastroduodenoscopy findings showed the Mallory-Weiss syndrome to be the most incident (46.9%).

Acute Disease↗
PubMed1999

Retrograde esophageal balloon dilatation for caustic stricture in an outpatient clinic setting.

Caustic injury to the esophagus, with resultant esophageal stricture, is a challenge for the surgeon. These strictures require multiple esophageal dilatations, which are usually performed under general anesthesia and frequently under fluoroscopic control. Because of the risks of multiple general anesthetics and frequent radiation, a technique is described for retrograde esophageal balloon dilatation in an outpatient clinic setting without a general anesthetic or fluoroscopic control.

Ambulatory Care↗
PubMed1976

[Large esophagogastric caustic burns in the adult].

The authors treated, as an emergency, severe caustic burns in adults. They present 13 cases and discuss four deaths. Critical analysis of these observations,compared with the findings of pathology and in the literature, permit one to consider the therapeutic indications. The place of often major surgical operations is discussed in relation to further specialist investigations or the appearance of complications. The results are assessed in 8 patients who were followed up for a long period.

Adolescent↗
PubMed1978

[Long term results of dilatation using the tube-bougie method in stenosis following caustic oesophagitis (author's transl)].

The tube-bougie methode suggested by the authors ten years ago for dilatation of oesophageal stenosis is based upon the fact that the instrument dilates only in the oesophagus itself and that it consists, on the one hand at the level of the stomach and secondly at the level of the nose and pharynx of a tube a small calibre which makes it possible to leave the dilating instrument in place for far longer periods (24 to 48 hours) than conventional bougies, increasing the interval between dilatation sessions. This technique has been used several hundred times for various indications, but only 6 cases of caustic oesophagitis (with a total of 440 dilatations) each patient being followed up for more than three and a half years, have been studied in order to determine the effectiveness of the method. Amongst the causes of recurrent stenosis or of an imperfect long term result, the authors stress the role of the reflux of gastric fluid and above all of progressive fibroinflammatory mediastinitis.

Adult↗
PubMed1975

[Scanning electronmicroscopic studies on the behavior of so-called caustic-adhesive composite resins].

Two new caustic-adhesive composite resins (Concise-Enamel-Bond and Nuva-Seal/Nuva-Fil) were tested in experimentally prepared flat cavities in extracted human teeth under the scanning electron microscope. On the basis of the findings, possible failures with this filling technique resulting from insufficient adhesion of the "sealer" at the enamel are discussed, and practical proposals worked out (utilization of rubber dam, final coating with the sealer to improve surface quality and prevent marginal gaps).

Composite Resins↗
PubMedDate not supplied

Pancreaticoduodenal necrosis due to caustic burns.

BACKGROUND AND METHODS: Fourteen patients with caustic necrosis of the digestive tract extending beyond the pylorus were included in a multicenter retrospective study to define a surgical strategy. Twelve patients underwent esophagogastrectomy. Two patients had total gastrectomy without esophagectomy. In addition, all patients underwent duodenal stripping (n = 7) or pancreaticoduodenectomy (n = 7). Immediate biliopancreatic reconnection was performed in ten patients. Four patients had biliary diversion and/or pancreatic duct ligation. RESULTS: Seven in-hospital deaths occurred after a mean delay of 27 days (range 16-45 days). There were two late deaths occurring 6 and 12 months postoperatively. Morbidity was noted in 86% of survivors. Acute or chronic airway tract injuries were incurred by 57% of patients. Among the five long-term survivors two were able to feed orally and had preserved voice function. One long-term survivor could resume oral feeding only, another was considered psychologically unfit for digestive reconstruction but had normal voice function and the last patient was deprived of oral feeding and phonation. CONCLUSIONS: Early radical debridement is capable of saving patients with gastrointestinal necrosis extending beyond the pylorus. Necrosis of the duodenum can be managed by pancreaticoduodenectomy or by duodenal stripping, with similar results. Immediate reconnection of the bile and pancreatic ducts to a small bowel Roux-en-Y loop appears preferable to biliary diversion and pancreatic duct ligation. Normal oral feeding and the preservation of voice function can sometimes be achieved but depends on late scarring of the airway-alimentary tract junction. Quality of life is often compromised by prolonged hospital stays, staged surgical procedures and the handicap of a feeding jejunostomy and tracheal tube.

Adult↗
PubMedDate not supplied

[Surgical treatment of redundant colon after retrosternal esophagocolonoplasty for caustic esophageal stenosis].

The Authors report two cases of transposed colon redundancy occurring after surgical treatment in 37 patients with caustic oesophageal strictures by retrosternal oesophagoplasty. Surgical management was required because of persistent dysphagia and weight loss in both patients. The technique performed was a resection of the redundant loop with a termino-terminal colo-colonic anastomosis via a right thoracic approach.

Adult↗
PubMed2001

[Consequences of caustic damage of the esophagus].

Following ingestion of a highly concentrated acetic acid solution, three women aged 29, 23 and 25 years old, suffered damage to the oesophagus and the stomach, respiratory and renal insufficiency and haemolysis. After intensive treatment, gastric tube reconstruction was carried out in 2 of these patients, and the third woman required repeated dilatations of the oesophageal stricture from 6 weeks after ingestion onwards. This resulted in a normal passage of solid food in all women. A 58-year-old man who had ingested caustic soda at 4 years of age, presented with increasing problems associated with swallowing food. A squamous cell carcinoma was diagnosed and treated with chemotherapy, oesophagus-cardia resection and gastric tube reconstruction. After 2 years the tumour has not recurred. Ingestion of corrosive substances can lead to serious damage of the gastrointestinal tract. Early endoscopy is important in establishing the extent of the injury. During the acute phase, intensive care admittance is often necessary and resection of the oesophagus is also necessary in some cases. Subsequent treatment can vary from endoscopic dilations to gastric tube reconstruction following resection of the oesophagus.

Acetic Acid↗
PubMedDate not supplied

[Occupational estimation of the levels of mercury in workers engaged in electrochemical manufacture of caustic soda].

Plasmaless atomic absorption was used to study biosubstrates from the workers engaged in the production of caustic soda for the levels of mercury. In 63% of the examinees, the urinary concentrations of mercury exceeded the critical value and substantially increased after administration of a detoxifying agent. The content of mercury in the hair was also higher than the physiologically allowable normal value. The cause of chronic mercury intoxication was the intensive contamination of the industrial environment with mercury vapours.

Chemical Industry↗