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PubMed2001

Cleaning strategies for flux recovery of an ultrafiltration membrane fouled by natural organic matter.

One of the most common problems encountered in water treatment applications of membranes is fouling. Natural organic matter (NOM) represents a particularly problematic foulant. Membranes may be fouled by relatively hydrophilic and/or hydrophobic NOM components, depending on NOM characteristics, membrane properties, and operating conditions. To maximize flux recovery for an NOM-fouled ultrafiltration membrane (NTR 7410), chemical cleaning and hydraulic rinsing with a relatively high cross-flow velocity were investigated as cleaning strategies. The modification of the membrane surface with either an anionic or a cationic surfactant was also evaluated to minimize membrane fouling and to enhance NOM rejection. Foulants from a hydrophobic NOM source (Orange County ground water (OC-GW)) were cleaned more effectively in terms of permeate flux by acid and caustic cleanings than foulants from a relatively hydrophilic NOM source (Horsetooth surface water (HT-SW)). An anionic surfactant (sodium dodecyl sulfate (SDS)) was not effective as a cleaning agent for foulants from either hydrophobic or hydrophilic NOM sources. High ionic strength cleaning with 0.1 M NaCl was comparatively effective in providing flux recovery for NOM-fouled membranes compared to other chemical cleaning agents. Increased cross-flow velocity and longer cleaning time influenced the efficiency of caustic cleaning, but not high ionic strength cleaning. The membrane was successfully modified only with the cationic surfactant; however, enhanced NOM rejection was accompanied by a significant flux reduction.

Acids↗
PubMed1980

Toxicity of alkaline solutions.

We examined the question of what determines the toxicity of alkaline solutions--pH, viscosity, or other factors. Our experiments have identified pH measurement as the simplest and most easily measured parameter for determining initial management of caustic ingestions. Viscosity is not a clinically useful measurement. The closer to 14 the pH measures, the more destructive the caustic. Non-lye solutions known to cause esophageal ulceration have a pH of 12.5 to 13.5. Most cases of deep ulceration going on to stricture formation involve lye solutions of pH 14. The critical pH that causes esophageal ulceration is 12.5, and thus a patient ingesting a substance with a pH greater than 12 should be followed closely for the possibility of esophageal ulceration.

Alkalies↗
PubMed2001

A study of iron mineral transformation to reduce red mud tailings.

This study examines the effects of iron mineral transformation in an aluminum extraction process on the settling behavior, and the physical and chemical properties of the resulting red mud slurry that must be disposed of. By producing a red mud with a higher solid content, the total volume of mud slurry will also be reduced for a given alumina production rate and more caustic soda will be recovered. The settling behavior and the mineralogical, physical, and physico-chemical properties of one bauxite and three red muds processed under varying conditions were analyzed based on examination of the iron mineral transformations. The properties of red muds derived from the same bauxite can differ markedly due to variations in operating conditions of the Bayer process, such as temperature and the addition of a reducing agent. The settling of red mud can be improved by converting goethite into hematite and/or magnetite to produce a mud of larger particle size, smaller specific surface area, and larger specific gravity, characteristics which reduce the total volume of mud slurry to be disposed of and which allow for less potential contamination from caustic soda. This study also found that the by-product--Bayer sodalite--has the high exchange capacity for Na+ that might contribute to the long-term environmental problems.

Aluminum Oxide↗
PubMed1991

Burns of the oral mucosa. Report of 6 cases.

Burns of the oral cavity may be caused by prolonged use of certain drugs by the patient or by incorrect use of caustics by the dentist. Unwillingly-acquired self-inflicted injuries are also encountered, such as caustic ingestion (out of curiosity or by accident), excessive consumption of fresh fruit and fresh fruit juice, and wrong oral hygiene practice. Our experience with six infrequent and unfamiliar types of oral burns, caused by various components and material, is described and discussed.

Adult↗
PubMed2002

Late complications of coloesophagoplasty and long-term features of adaptation.

OBJECTIVES: Revisional surgery of late complications after 141 substernal by-pass operations (1962-1990), except three cases with isoperistaltic (except seven with anisoperistaltic) transverse colon grafts for caustic esophageal strictures, are presented. Long-term adaptation of the grafts was investigated with cineradiographical and histochemical methods. METHODS: Correction of the "pseudodiverticulum" of the proximal anastomosis as a complication of the standard by-pass procedure (in five patients) was achieved by closure of the esophagus below the anastomosis or by end-to-end reanastomosis. Cervical anastomosis stricture (in seven) was solved either by plasty or resection and a similar reanastomosis. Delayed passage due to an intra-abdominal redundant graft (in five) was managed by abdominal shortening coloplication or by side-to-side gastrocolostomy. Late pyloric obstruction as a cause of gastrocolic reflux required pyloroplasty in two instances. Mixed barium-bread bolus for a cineradiographical transit study and periodic acid Schiff reaction plus Alcian Blue staining for a mucopolysaccharide search were used 8 years after the operations. RESULTS: In all but one case, redo surgery was successful. Characteristic coordinated multihaustral propulsive movement developed in the distal colonic segment, playing a secondary but active role in the final phase of swallowing in isoperistaltic substitution. These grafts were free from gastrocolic reflux. Augmentation of neutral mucopolysaccharide was observed on the surface and in the Lieberkühn glands of colonic mucosa. CONCLUSIONS: This experience attests that the majority of late complications following colonic esophageal substitution may be corrected by revisional surgery. The predominantly automatic propulsive movements of the isoperistaltically interposed grafts seem to provide an effective antireflux barrier against the gastrocolic reflux if some technical requirements (high gastric anastomosis, good gastric drainage, etc.) are respected. The graft mucosa showed signs of a positive adaptation. The best functional results were achieved by isoperistaltically interposed left colic transplants, which may be considered as an ideal graft (both technically and functionally) in extensive caustic strictures.

Anastomosis, Surgical↗
PubMed1987

Chemical burns of the oesophagus.

Chemical burns of the oesophagus caused by ingestion of corrosives present a difficult and potentially dangerous problem of management. Initial failure to recognize the seriousness of the injury and inexperience in the handling of the severer burn may result in consequences which are both life-threatening and life-long. Analysis of 95 patients who had ingested caustic substances is presented. Ninty-one sustained burns of the mouth, 39 of the hypopharynx or oesophagus, and 31 had laryngeal burns. Sixty-three were children of 15 years and under. Caustic soda, especially in children, was the most common substance ingested. Severe oesophageal strictures developed early in 17 patients and in a further 21 oesophageal stricturing occurred late. A protocol for the management of these patients is discussed.

Adolescent↗
PubMed2006

Inactivation of biological agents using neutral oxone-chloride solutions.

Bleach solutions containing the active ingredient hypochlorite (OCl-) serve as powerful biological disinfectants but are highly caustic and present a significant compatibility issue when applied to contaminated equipment or terrain. A neutral, bicarbonate-buffered aqueous solution of Oxone (2K2HSO5.KHSO4.K2SO4) and sodium chloride that rapidly generates hypochlorite and hypochlorous acid (HOCl) in situ was evaluated as a new alternative to bleach for the inactivation of biological agents. The solution produced a free chlorine (HOCl + OCl-) concentration of 3.3 g/L and achieved > or =5.8-log inactivation of spores of Bacillus atrophaeus, Bacillus thuringiensis, Aspergillus niger, and Escherichia coli vegetative cells in 1 min at 22 degrees C. Seawaterwas an effective substitute for solid sodium chloride and inactivated 5 to 8 logs of each organism in 10 min over temperatures ranging from -5 degrees C to 55 degrees C. Sporicidal effectiveness increased as free chlorine concentrations shifted from OCl- to HOCl. Neutrally buffered Oxone-chloride and Oxone-seawater solutions are mitigation alternatives for biologically contaminated equipment and environments that would otherwise be decontaminated using caustic bleach solutions.

Anti-Infective Agents↗
PubMed2002

Biological reduction of perchlorate in ion exchange regenerant solutions containing high salinity and ammonium levels.

The most promising technologies to remove perchlorate from water are ion exchange and biological reduction. Although successful, ion exchange only separates perchlorate from water; it does not eliminate it from the environment. The waste streams from these systems contain the caustic or saline regenerant solutions used in the process as well as high levels of perchlorate. Biological reduction could be used to treat the regenerant waste solutions from the ion exchange process. A treatment scheme, combining ion exchange and biodegradation, is proposed to completely remove perchlorate from the environment. Perchlorate-laden resins generate brines containing salt concentrations up to 6% or caustic solutions containing up to 0.5% ammonium. Both, high salt and ammonium hydroxide concentrations are potentially toxic to microorganisms. Therefore, the challenge of the proposed system is to find perchlorate reducing microorganisms that are effective under such stressful conditions. Preliminary results have shown that salt concentrations as low as 0.5% reduced the perchlorate biodegradation rate by 30%; salt concentrations greater than 1% decreased this rate to 40%. Although biodegradation was seen in ammonium levels of 0.4%, 0.6% and 1%, the perchlorate biodegradation rate was 90% of that at 0% ammonium hydroxide. Further research will focus on the isolation and/or acclimation of microorganisms that are able to biodegrade perchlorate under these stressful conditions.

Ammonium Hydroxide↗
PubMed2003

Interaction of inhalational anaesthetics with CO2 absorbents.

We review the currently available carbon dioxide absorbents: sodium hydroxide lime (=soda lime), barium hydroxide lime, potassium-hydroxide-free soda lime, calcium hydroxide lime and non-caustic lime. In general, all of these carbon dioxide absorbents are liable to react with inhalational anaesthetics. However, there is a decreasing reactivity of the different absorbents with inhalational anaesthetics: barium hydroxide lime >> soda lime > potassium-hydroxide-free soda lime > calcium hydroxide lime and non-caustic lime. Gaseous compounds generated by the reaction of the anaesthetics with desiccated absorbents are those that threaten patients. All measures are comprehensively described to--as far as possible--prevent any accidental drying out of the absorbent. Whether or not compound A, a gaseous compound formed by the reaction of sevoflurane with normally hydrated absorbents, is still a matter of concern is discussed. Even after very high loading with this compound, during long-lasting low-flow sevoflurane anaesthesias, no clinical or laboratory signs of renal impairment were observed in any of the surgical patients. Finally, guidelines for the judicious use of different absorbents are given.

Absorption↗
PubMed2006

Mitomycin C: an alternative conservative treatment for refractory esophageal stricture in children?

BACKGROUND AND STUDY AIMS: Mitomycin C is an antiproliferative agent that has been used successfully as an adjunct treatment in ophthalmological procedures, in the management of laryngeal and tracheal stenosis, and more recently to prevent the recurrence of caustic esophageal strictures in children. The aim of this study was to assess the efficacy and safety of local application of mitomycin C to refractory esophageal strictures in children. PATIENTS AND METHODS: We performed a preliminary prospective study of local application of mitomycin C in four children, aged between 1 year and 6 years, who had refractory esophageal strictures. Two of the children presented with strictures caused by caustic ingestion and the other two children had anastomotic strictures following surgical repair of congenital esophageal atresia. The patients had required between four and ten esophageal dilations over a 5-24-month period before mitomycin C application. After an endoscopic dilation, mitomycin C was applied onto the dilation wound using a rigid endoscope. RESULTS: No complications were observed after the procedure. One child required a second application of mitomycin C 2 weeks after the first application because of recurrence of dysphagia. All the children remained asymptomatic and none of them required further dilation over a mean follow-up period of 24 months. Radiological control examinations revealed that there was no recurrence of the esophageal strictures and esophageal biopsies performed during follow-up showed no signs of dysplasia. CONCLUSIONS: Local application of mitomycin C is a potential alternative to iterative dilations, surgery, or stent placement for the treatment of refractory esophageal strictures in children. However, prospective, long-term assessment of outcomes is needed before any definitive conclusion can be drawn about the usefulness of mitomycin C in these patients.

Administration, Topical↗
PubMed1985

[Colliquation necrosis of the skin caused by a cardiac pacemaker].

In two patients with cardiac infarction of a medical intensive care unit blisters developing into deep necroses were observed on the upper extremities and adjoining regions of the trunk within the first days of treatment. Clinical findings and histology indicated extensive caustic artefacts. The cause for the initially mysterious event was found to be a defect in the extracorporeal cardiac pacemaker. Defective isolation had lead to a continuous current potential between pacemaker cover and electrode. The resulting electrolysis caused a dramatic increase of pH on the moist body surface underneath the pacemaker. As a result of the pH shift caustic damage with extensive dermal necroses was observed.

Aged↗
PubMed2000

Evaluation of the smoothed interference pattern under conditions of ray chaos.

A ray-based approach has been considered for evaluation of the coarse-grained Wigner function. From the viewpoint of wave propagation theory this function represents the local spectrum of the wave field smoothed over some spatial and angular scales. A very simple formula has been considered which expresses the smoothed Wigner function through parameters of ray trajectories. Although the formula is ray-based, it nevertheless has no singularities at caustics and its numerical implementation does not require looking for eigenrays. These advantages are especially important under conditions of ray chaos when fast growing numbers of eigenrays and caustics are the important factors spoiling applicability of standard semiclassical approaches already at short ranges. Similar factors restrict applicability of some semiclassical predictions in quantum mechanics at times exceeding the so-called "logarithm break time." Numerical calculations have been carried out for a particular model of range-dependent waveguide where ray trajectories exhibit chaotic motion. These calculations have confirmed our conjecture that by choosing large enough smoothing scales, i.e., by sacrificing small details of the interference pattern, one can substantially enhance the validity region of ray theory. (c) 2000 American Institute of Physics.

Journal Article↗
PubMed2006

A coherent state approach to semiclassical nonadiabatic dynamics.

A semiclassical (SC) approximation to the quantum mechanical propagator for nonadiabatic systems is derived. Our derivation starts with an exact path integral expression that uses canonical coherent states for the nuclear degrees of freedom and spin coherent states for the electronic degrees of freedom. A stationary path approximation (SPA) is then applied to the path integral to obtain the SC approximation. The SPA results in complex classical trajectories of both nuclear and electronic degrees of freedom and a double ended boundary condition. The root search problem is solved using the previously proposed "real trajectory local search" algorithm. The SC approximation is tested on three simple one dimensional two-state systems proposed by Tully [J. Chem. Phys. 93, 1061 (1990)], and the SC results are compared to Ehrenfest and surface hopping predictions. Excellent agreement with quantum results is reached when the SC trajectory is far away from caustics. We discuss the origin of caustics in this SC formalism and the strengths and weaknesses of this approach.

Journal Article↗
PubMedDate not supplied

Occupation-related burn injuries.

Unlike household burn injuries, the characteristics of burn injuries in the workplace have not been well described. In an effort to understand the causes and effects of occupation-related burn injuries and to aid in prevention, we sought to describe work-related burn injuries by frequency, burn type, age of the patients, body parts burned, and occupation of the patients. This was a statewide, cross-sectional study of all burns that occurred in the workplace during 1994. Data on fatal injuries were obtained from the National Census of Fatal Occupational Injuries. Survey data from the North Carolina Department of Labor were used for nonfatal injuries. Burns caused 34 deaths (15.3%) and 1720 injuries in the workplace in 1994. Of the nonfatal injuries, 1363 (79.2%) were caused by exposure to caustic substances or hot objects or substances. The head and upper extremities were the most frequently injured body parts (936 injuries; 57.6%). The average age of those burned was 30.7 years; most of the patients ranged from 25 to 35 years old. High-risk occupations included vehicle and equipment cleaners, food service personnel, and millwrights (11.3%, 5.3%, and 5.2% of burn injuries, respectively). Unlike the flame burns that occur in homes, exposure to caustics and hot objects and substances caused the majority of on-the-job burn injuries. Protective gear for the head and upper extremities may prevent a significant number of burns. Education and prevention programs may best be directed at workers with high-risk occupations and workers in the 25- to 35-year age range.

Accidents, Occupational↗
PubMed2005

[Study of the metal precipitation from decontamination leachates of municipal wastes fly ash incinerators].

This research work focuses on the development of a new process for the decontamination of municipal wastes incinerators fly ashes. The objective of this study was to evaluate different total and selective precipitation methods for metals removal from ash decontamination leachates. The tested options include 1) use of hydrated lime and caustic soda for selective (pH 5.0) and total (pH 8.5) metal precipitation; 2) addition of different chemicals (H3PO4, Na2S and FeCl3) in a pH range from 6.0 to 9.0. Fly ash decontamination assays using alkaline and acid washing steps were initially performed using optimal conditions previously established. Treated fly ashes respected the standards based on the TCLP leaching test for all studied metals and SPLP. Total metal precipitation tests carried out at pH 8.5 achieve removal yields for all metals > or = 90% using hydrated lime and > or = 83% using caustic soda. Selective precipitation tests alone at pH 5.0 show removal yields > or = 97% for Cr and between 75 and 87% for Al and Pb. Moreover, assays carried out using a stoechiometric addition of Na2S have allowed the separation of Cd (> or = 99%) and Zn (> or = 71%) as metal sulphides (CdS and ZnS). From an economical point of view, the most interesting option seems to be the leachates neutralization at pH 7.0 using Ca(OH)2 combined with the reuse of the treated leachates in the fly ash leaching steps. Metal precipitation cost at pH 7.0 has been estimated to be 22.7 CAN dollars tct-1 using Ca(OH)2, and 26.7 CAN dollars tct-1 using NaOH.

Carbon↗
PubMed1989

Skin and perivascular toxicity induced experimentally by doxorubicin.

Extravasation of antitumor drugs and particularly doxorubicin (DXR) can be followed by skin ulceration and slowly evolving perivascular necrosis. DXR lesions have some characteristics in common with those induced by ionizing radiation and, with respect to gross morphology, are reminiscent of skin lesions induced by necrotizing agents. Time course and histopathology of toxic phenomena induced by intradermal or perivascular injection of various doses of either DXR or caustic chemicals have been studied in hairy outbred and hairless inbred (MF1 hr/hr) mice. The latter strain has been found to be intrinsically more sensitive to DXR induced toxic effects, particularly as far as perivascular administration is concerned. Long lasting lesions and, in a few cases, systemic involvement have been observed. On the contrary, necrotic foci induced by caustic chemicals rapidly regressed in both strains. The perivascular administration model, which has not been previously investigated, appears to be representative of what happens in clinical conditions and can be of use for assessing either skin toxicity of antitumor compound or the protective effect of candidate antidotes.

Animals↗
PubMed2003

Endoscopy-guided balloon dilatation of oesophageal strictures in children.

The aim of the study is to evaluate the indications, safety, and efficacy of endoscopy guided balloon dilatation (EGBD) in the treatment of strictures of the oesophagus in children. Between 1998 and 2002, 12 infants and children with oesophageal strictures were treated with EGBD in our institute. Median age was 4.1 years (range, 2 months-11 years). Of 12 patients, four had oesophageal strictures, following repair of oesophageal atresia; six had short-segment caustic strictures; and two had anastomotic strictures after oesophageal replacement (colon, 1; stomach, 1). All patients had previously failed to respond to conventional bouginage (mean, 6 sessions; range 2-14). All patients underwent contrast studies before EGBD. EGBD was performed using flexible endoscopy and fluoroscopic screening under general anaesthesia. The mean number of EGBD procedures per patient was six (range 4-10). The functional results were complete in ten and temporary in two patients. There has been no morbidity or mortality. EGBD is safe and effective for treating oesophageal anastomotic and short-segment caustic strictures.

Journal Article↗
PubMed2003

Oral burn contractures in children.

Oral burn contractures in children present major reconstructive problem. Only few reports in literature discussed oral burns in children. Electrical, chemical, and thermal agents are the main causative agents for oral burns. Oral contractures can be classified into anterior, posterior, and total. Anterior contractures are usually caused by electrical burns and involve the oral commissure, lips, anterior buccal sulcus and surrounding mucosa, and anterior tongue. Posterior oral contractures are caused by caustic ingestion and involve the posterior buccal mucosa, posterior tongue, retro-molar area and oro-pharynx. Total oral contractures involve the lips, tongue, oral cavity, and oro-pharyngeal mucosa and are caused by lye caustic ingestion. This report reviews three children; one with posterior, two with total oral cavity contracture. All cases were managed by linear release of scar contracture and skin grafting followed by a prolonged intra-oral splinting with a fixed mouth-block and commissural splint. A successful outcome was observed in all cases.

Burns↗