Degradation of 2,4,5-trichlorophenoxyacetic acid by a novel Electro-Fe(II)/Oxone process using iron sheet as the sacrificial anode

A novel electrochemically enhanced advanced oxidation process for the destruction of organic contaminants in aqueous solution is reported in this study. The process involves the use of an iron (Fe) sheet as sacrificial anode and a graphite bar as cathode. In the oxidation process, once an electric current is applied between the anode and the cathode, a predetermined amount of Oxone is added to the reactor. Ferrous ions generated from the sacrificed Fe anode mediate the generation of highly powerful radicals (SO(4)(•-)) through the decomposition of Oxone. The coupled process of Fe(II)/Oxone and electrochemical treatment (Electro-Fe(II)/Oxone) was evaluated in terms of 2,4,5-Trichlorophenoxyacetic acid degradation in aqueous solution. Various parameters were investigated to optimize the process, including applied current, electrolyte and Oxone concentration. In addition, low solution pH facilitates the system performance due to the dual effects of weak Fenton reagent generation and persulfate ions generation, whereas the system performance was inhibited at basic pH levels through non-radical self-dissociation of Oxone and the formation of ferric hydroxide precipitates. Furthermore, the active radicals involved in the Electro-Fe(II)/Oxone process were also identified. The Electro-Fe(II)/Oxone process demonstrates a very high 2,4,5-T degradation efficiency (over 90% decay within 10 min), which justifies the novel Electro-Fe(II)/Oxone a promising treatment process for herbicide removal in water.

Degradation of a xanthene dye by Fe(II)-mediated activation of Oxone process

A powerful oxidation process using sulfate radicals activated by transition metal mediated Oxone process has been evaluated in depth by monitoring the degradation of a xanthene dye Rhodamine B (RhB) in aqueous solution. Ferrous ion was chosen as the transition metal due to its potential catalytic effect and wide availability in dyeing industrial effluent. The effects of parameters including reactant dosing sequence, Fe(II)/Oxone molar ratio and concentration, solution pH, and inorganic salts on the process performance have been investigated. Total RhB removal was obtained within 90 min under an optimal Fe(II)/Oxone molar ratio of 1:1. The RhB degradation was found to be a two-stage kinetics, consisting of a rapid initial decay and followed by a retarded stage. Additionally, experimental results indicated that the presence of certain anions had either a positive or negative effect on the process. The inhibitory effect in the presence of SO(4)(2-) was elucidated by a proposed formula using Nernst equation. Furthermore, dye mineralization in terms of TOC removal indicates that stepwise addition of Fe(II) and Oxone can significantly improve the process performance by about 20%, and the retention time required can be greatly reduced comparing with the conventional one-off dosing method.

Mask Technology For X-Ray Nanolithography

In this report we describe a system of technologies we have developed for fabricating, patterning, and replicating x-ray masks with linewidths as fine as 50 nm (0.05 μm). This effort has evolved into a fairly routine service supporting a growing community of researchers at MIT interested in fabricating sub-micron and nanometer scale structures and devices. Strong, transparent, silicon-rich nitride (SiN) membranes bonded to optically-flat Pyrex rings and patterned with gold absorbers form the basic x-ray mask structure. We have recently completed the installation of a vertical thermal reactor (VTR) for the deposition of SiN coatings. Results indicate superb film uniformity, decreased defect counts, and increased strength over previously available nitrides. Patterning of the masks is performed at an off-site location by electron-beam lithography followed by development and gold electroplating at MIT. We describe a new fountain plating bath and mask chuck which allows us to obtain clean, uniform gold films of low stress. Once completed, the so-called “master” masks are replicated onto new x-ray mask substrates which are then processed into “daughter” masks. The resulting polarity-reversed patterns are required in order to achieve the desired pattern in positive resist when printed onto substrates. We will describe our in-house built x-ray aligner which features a high-power electron bombardment source and SiN vacuum isolation window to achieve exposures in a helium environment.

Degradation of linuron by UV, ozonation, and UV/O(3) processes--effect of anions and reaction mechanism

A comprehensive study of the degradation of linuron, one of the phenylurea herbicides, was conducted by using different treatment processes including UV, ozonation and UV/O(3). The effect of various anions on the performance of ozonation has been examined. N-terminus demethoxylation, photohydrolysis with or without dechlorination, and N-terminus demethylation have been found to be the major mechanisms in the linuron decay under the irradiation of UV at 254 nm while N-terminus demethoxylation, dechlorination and hydroxylation on benzene ring was observed to be involved in the ozonation process. Eight new intermediates were identified in UV process in this study compared with previous studies. Different decay pathways were proposed based on the identified intermediates in the three studied processes. UV/O(3) has demonstrated the best performance among these three processes in terms of LNR decay, mineralization, dechlorination and de-nitrogenation.

Heterogeneous lollipop-like V2O5/ZnO array: a promising composite nanostructure for visible light photocatalysis

ZnO/V(2)O(5) core-shell nanostructures have been prepared by a two-step synthesis route through combined hydrothermal growth and magnetron sputtering. After annealing under oxygen ambience, a ZnO/V(2)O(5) heterogeneous lollipop-like nanoarray formed. The microstructure and crystal orientation of those nanolollipops were investigated by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), which show single crystal structure. The optical properties were characterized by UV-vis spectroscopy and showed quite different absorption curves for the as-deposited and annealed samples. The ZnO/V(2)O(5) nanolollipops demonstrated excellent photocatalytic activity in terms of decomposing 2,6-dichlorophenol (2,6-DCP) under visible light, indicating their promising potential as catalysts for industrial wastewater and soil pollution treatments.

Reactor model development: the removal performance of ferrous-catalysed photo-oxidation process by examining the reaction parameters

The removal performance of the ferrous catalysed photo-oxidation process was investigated through the examination of major process parameters including pH levels and dosages of ferrous (Fe(2+)) and hydrogen peroxide (H(2)O(2)). A common used herbicide, alachlor, was used as a target compound in the degradation process. In the study, alachlor was found to be effectively degraded by hydroxyl radicals (HO) which were generated by UV/Fe(2+)/H(2)O(2) in the oxidation process. It was interesting to find that the pattern of reaction kinetics of alachlor varied depending on the initial concentrations of Fe(2+) and H(2)O(2). An optimum H(2)O(2) dosage was determined. This was practically useful because the overdose of H(2)O(2) would cause the process retardation. The conventional pseudo-first-order kinetics and two-stage first-order kinetics were observed at lower and higher Fe(2+) concentrations, respectively. Models were proposed and used to stimulate the kinetic process. Thus, design charts were established for determining the reaction time (i.e., reactor sizing) required for predetermined removal performance of alachlor under different concentrations of H(2)O(2) and Fe(2+).

Reaction mechanism of linuron degradation in TiO2 suspension under visible light irradiation with the assistance of H2O2

The application of TiO2/H2O/Vis (visible light) process for the aqueous degradation of linuron (LNR) has been investigated. The performance of TiO/H2O2/Vis process has been compared with other processes such as TiO2/H2O2 in the dark, TiO2/Vis, and H2O2 is in terms of LNR decay. The result showed that more than 70% LNR could be decomposed in the TiO2/H2O2/Vis. The degradation mechanism of LNR by TiO2/H2O2/Vis process has been verified through investigation of the effects of various radical scavengers on the performance of this system, monitoring the generation of photocurrent, and comparing the intermediates and decay pathways of LNR by UV-TiO2 and TiO2/ H2O2/Vis processes with 16 and 17 intermediates identified, respectively. It has been revealed that demethoxylation and demethylation through alkylic-oxidation is the major mechanism of LNR degradation while dechlorination (hydroxylation at the chlorine site) and direct hydroxylation on the benzene ring is minor in both processes. Mineralization and release of chlorine and nitrogen have been also studied.

Challenges in phenotype definition in the whole-genome era: multivariate models of memory and intelligence

Refining phenotypes for the study of neuropsychiatric disorders is of paramount importance in neuroscience. Poor phenotype definition provides the greatest obstacle for making progress in disorders like schizophrenia, bipolar disorder, Attention Deficit/Hyperactivity Disorder (ADHD), and autism. Using freely available informatics tools developed by the Consortium for Neuropsychiatric Phenomics (CNP), we provide a framework for defining and refining latent constructs used in neuroscience research and then apply this strategy to review known genetic contributions to memory and intelligence in healthy individuals. This approach can help us begin to build multi-level phenotype models that express the interactions between constructs necessary to understand complex neuropsychiatric diseases. These results are available online through the http://www.phenowiki.org database. Further work needs to be done in order to provide consensus-building applications for the broadly defined constructs used in neuroscience research.

Degradation of atrazine by cobalt-mediated activation of peroxymonosulfate: Different cobalt counteranions in homogenous process and cobalt oxide catalysts in photolytic heterogeneous process

The degradation of atrazine (ATZ) by cobalt-mediated activation of peroxymonosulfate (PMS) has been studied in this work. For the homogenous process, different cobalt counteranions: cobalt(II) nitrate Co(NO(3))(2), cobalt(II) sulfate CoSO(4), cobalt(II) chloride CoCl(2), and cobalt(II) acetate Co(CH(3)COO)(2), have been examined. The inhibitory effect was observed in the process initiated by CoCl(2). For the pH test, wide range of pH level (2-10) has been investigated. It was found that the higher rates were obtained in the normal pH levels. At extreme pH levels, the process was impeded by inactivation of PMS at acidic pH and prohibited by precipitation at basic pH. On the other hand, the recycling capability of cobalt oxide and the oxidative potential of cobalt-immobilized titanium dioxide Co-TiO(2) catalyst were analyzed in the heterogeneous process. It was found that the higher the cobalt content in the catalyst, the better the removal performance was resulted. At last, the Co-TiO(2) catalyst synthesized in this work was found to be very effective in transforming ATZ as well as its intermediate in the presence of UV-vis irradiation.

A new approach to quantify the degradation kinetics of linuron with UV, ozonation and UV/O3 processes

The degradation of linuron, one of phenylurea herbicides, was investigated for its reaction kinetics by different treatment processes including ultraviolet irradiation (UV), ozonation (O3), and UV/O3. The decay rate of linuron by UV/O3 process was found to be around 3.5 times and 2.5 times faster than sole-UV and ozone-alone, respectively. Experimental results also indicate overall rate constants increased exponentially with pH above 9.0 while the increase of rate constants with pH below 9 is insignificant in O3 system. All dominant parameters involved in the three processes were determined in the assistant of proposed linear models in this study. The approach was found useful in predicting the process performances through the quantification of quantum yield (Phi(LNR)) (rate constant for the formation of free radical HOO(.-) from ozone decomposition at high pH), rate constant of linuron with ozone ((k(O3,LNR)), rate constant of linuron with hydroxyl radical (k(OH,LNR)), and alpha (the ratio of the production rate of OH() and the decay rate of ozone in UV/O3 system).

The photodegradation and modeling of a typical NAPL trichloroethene, by monochromatic UV irradiations

In this study, the photodegradation of a typical nonaqueous phase liquid (NAPL)-trichloroethene (TCE) by ultraviolet irradiation was investigated. The decay of NAPL-TCE was studied in a RPR-200 Rayonet photochemical reactor, at three different monochromatic UV lamps (254, 300, and 350 nm). Among the three UV wavelengths used, the highest photodecay rate was obtained at 254 nm. The effect of the initial NAPL dosage was also analyzed to determine the photodecay of NAPL-TCE in batch experiments by ultraviolet irradiation at preselected wavelengths. The direct photolysis of NAPL-TCE followed two-stage pseudo first-order decay kinetics. The photodegradation rates of TCE were found to decrease with the increment of NAPL dosage. It is interesting to find that the NAPL dosage is critical to determine the process performance due to the NAPL size or cage effect, which will control the diffusion of TCE/intermediates between NAPL and aqueous phases and therefore the overall reaction rates. Mathematical models were developed for the prediction of the two-stage photodegradation, in which the remaining fraction of TCE (C/C0) in the system becomes predictable.

The photodegradation of trichloroethylene with or without the NAPL by UV irradiation in surfactant solutions

The photodegradation of trichloroethene (TCE) with or without nonaqueous phase liquids (NAPL) by ultraviolet irradiation in surfactant solutions was examined in this study. The photodecay of TCE was studied at monochromatic 254nm UV lamps. The effects of the type of surfactants, initial surfactant concentrations, pH levels and NAPL concentrations were examined to explore the photodecay of TCE. All the photodegradation of TCE followed pseudo-first-order decay kinetics at various conditions. It was found that Brij 35 overdose and higher initial pH levels may retard or inhibit the photodecay of TCE, mainly due to protons, intermediate generation and change of surfactant structure in the processes. The optimal condition for TCE photodecay was suggested based on the analysis of kinetics data, from which the reaction mechanism of TCE in the presence of NAPL form was also studied. In general, the reactions of TCE in micellar solution and NAPL pool can be considered as independent pathways due to the low molecule diffusion between the two phases.

Antenatal ovarian torsion: a "free-floating" cyst

This case report documents the unusual presentation of an antenatal ovarian torsion followed by auto-amputation of the ovarian tube complex, finally resulting in a free floating abdominal cyst. The differential diagnosis of antenatally diagnosed abdominal cysts is discussed and the surgical management outlined.

Removal of phenylurea herbicide monuron via riboflavin-mediated photosensitization

Photodegradation of the phenylurea herbicide monuron by using riboflavin (Rf), a sensitizer, was investigated by varying the doses of monuron and Rf in this work. An enhanced photochemical effect was observed in the process compared with the direct photolysis by using UV irradiation only. The reaction time was greatly shortened from more than 60 min (direct photolysis) to 8-30 min depending on the doses of initial concentration of monuron ([M]0) and Rf. A modified hyperbola model was found to be useful to determine the reaction kinetics and thereafter the performance on the photodegradation of monuron sensitized by Rf. Two measurable characteristic constants (initial decay rate and total removal index) were used to quantify the reaction. The maximum removal difference compared with the direct photolysis and Rf-sensitization was investigated. It was found that the improvement of the process depended on both the [M]0 and the doses of Rf.

Selection of supported cobalt substrates in the presence of oxone for the oxidation of monuron

The immobilization of cobalt ion on different media to catalyze oxone has been investigated. A probe herbicide, Monuron, was effectively degraded by using Co2+/oxone systems. For Co2+ supported on zeolite, 100% of Monuron could be removed within a 10 min reaction time. However, the recycling of the spent Co-zeolite catalyst using various posttreatments did not give a promising result. This is likely because the zeolite particles in solution have blocked and significantly attenuated the incident UV light from reducing Co3+ to Co2+. On the contrary, the use of cationic resin has minimized these problems. In the process of Co-resin/oxone/UV, faster Monuron decay could be achieved than that in the dark reaction. In the presence of UV, a significant drop of total organic carbon (TOC) was also observed in this approach suggesting an effective and clean process for Monuron mineralization.

Fetoscopy under gas amniodistension: pressure-dependent influence of helium vs nitrous oxide on fetal goats

PURPOSE

Recently, gas amniodistension has been advocated for fetoscopic surgery to employ ergonomics similar to laparoscopy. However, neither the optimal type of gas nor its physiological influence on the fetus have been clearly outlined yet. This study investigates the impact of helium (HE) vs nitrous oxide (N2O) on fetal goats during fetoscopy.

METHODS

We insufflated either HE or N2O in 12 pregnant goats (15 fetuses; HE = 7, N2O = 8), then increased the pressures from 0, 4, 7, to 10 mm Hg in 30-minute intervals and recorded the fetal and maternal vital parameters. Finally, whole-body computed tomography to asses for intracorporeal gas was performed.

RESULTS

All fetuses survived. Mean fetal vital signs showed no significant differences between HE or N2O at specific pressure levels. In detail, HE/N2O at 0 vs 10 mm Hg caused a fetal temperature decrease (32.9 degrees C/33.2 degrees C vs 32 degrees C/32.5 degrees C), heart rate increase in the N2O group (100/102 vs 102/121 beats per minute), and no significant change in arterial pressure (45.8/48.3 vs 53.7/46.7 mm Hg). The PO2 was adequate (3.7/3.3 vs 3.7/2.9 kPa), whereas the pH remained unchanged (7.4/7.3 vs 7.3/7.3). However, fetal pCO2 was elevated in the N2O group before insufflation (5.5/7.2 vs 6.8/8.0 kPa) owing to maternal hypoventilation (maternal PCO2: 4.9/5.8 vs 5.0/5.4 kPa), correction of which was slower in the fetus than in the maternal animal. Computed tomography ruled out intracorporeal gas accumulation.

CONCLUSION

Neither HE nor N2O impose significant physiological harm for the fetus. Heating of the gas and maternal anesthesia seem essential. Considering the potential teratogenicity of N2O, however, HE could be the favorable environment for fetoscopic procedures under gas amniodistension.

Ozonation of endocrine disrupting chemical BHA under the suppression effect by salt additive--with and without H(2)O(2)

The oxidation of fresh and saline wastewater containing an endocrine disrupting chemical (butylated hydroxyanisole, BHA) under different reaction conditions by ozonation and O(3)/H(2)O(2) was investigated at various pH levels. The observed pseudo-first-order reaction kinetics was justified through a combined direct ozone and indirect radical oxidation approach for the ozonation process. The BHA decay rates increased with the increase of the solution pH, but decreased as the NaCl concentration increased because of the consumption of ozone by chloride. A kinetic model was therefore derived for predicting BHA degradation at various initial pH levels and NaCl concentrations. For the O(3)/H(2)O(2) and O(3)/H(2)O(2)/Cl(-) processes, the rate of BHA removal was investigated at hydrogen peroxide concentration ranged from 0.5 to 5mM at pH 7. Different optimal H(2)O(2) dosages and decay rates were found for both processes due to the participation of reactions among O(3), H(2)O(2), OH* and Cl(-) as discussed in the paper.

The role of organic ligands in ferrous-induced photochemical degradation of 2,4-dichlorophenoxyacetic acid

Recent studies have shown that hydrogen peroxide is generated in a ferrioxalate-induced photoreductive reaction, but information about the effect of organic ligands on the photochemical behaviour of ferrous species is limited. The degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) by a ferrous-catalyzed oxidation in the presence of various ligands such as formate, citrate, malelate, oxalate, and ethylenediaminetetra-acetic acid (EDTA) was studied. The experiments were conducted under either dark or irradiated (350n m) conditions. Forty-two percent and 34% of 2,4-D were removed by the Fe(2+)/oxalate/UV and Fe(2+)/citrate/UV processes, respectively, after 30 min of reaction and oxidative intermediates were obtained in both cases. The presence of hydroxylated intermediates suggests that 2,4-D may be attacked by hydroxyl radicals, which are the products of the photo-Fenton-like reaction. As such, hydrogen peroxide was produced by the photolysis of ferrous oxalate or ferrous citrate, referred to hereafter as photogenerated H(2)O(2). As expected, the total removal percentage of 2,4-D jumped to 97% when 1mM of hydrogen peroxide (so-called spiked H(2)O(2)) was externally added to the reaction vessel to initiate the Fe(2+)/oxalate/UV process. Therefore, the treatment of 2,4-D by the Fe(2+)/oxalate/H(2)O(2)/UV system can be operated in two steps: the photolysis of ferrous oxalate first, followed by adding the spiked H(2)O(2) sometime after the commencement of the reaction. A two-phase model has been developed to describe this tandem ferrous-catalyzed photooxidation, which would help to achieve the mineralization of 2,4-D.

The effect of solution pH and peroxide in the TiO2-induced photocatalysis of chlorinated aniline

Chlorinated anilines are frequently used in the industry as starting materials for chemical synthesis. This type of compounds can end up as pollutants in wastewater. 2-Chloroaniline (2-ClA) was selected irradiating under monochromatic UV light at 300nm. The reaction rate could be enhanced by introducing low level of H(2)O(2) into the UV/TiO(2) system. Excess H(2)O(2) could not increase the HO* generation but retarded the reaction rate. The pH effect was also investigated in UV/TiO(2) and UV/TiO(2)/H(2)O(2) systems. All the experimental results show that pH is a sensitive parameter to the rate of degradation. Low reaction rate at acidic pH could be accounted by the dark adsorption test which has also proven the photocatalysis of TiO(2) may contribute to a two-step process: (1) 2-ClA pre-adsorbed onto TiO(2) and (2) photoexcitation of TiO(2). At high pH, rate enhancement could be observed at UV/TiO(2) system because of the increase generation of HO*. However, the introduction of H(2)O(2) slowdown the decay rate at such alkaline medium.

Degradation of atrazine by modified stepwise-Fenton's processes

The removal of atrazine (ATZ) by stepwise Fenton's processes (stepwise-FP) was studied and the system models were developed through the examination of reaction kinetics. The study compared the performance of the removal of ATZ by conventional FP with stepwise-FP, where the total dose of H(2)O(2) was split and inputted into the system at different times and/or quantities. The performance of stepwise-FP was found to be better than that of conventional FP. This was probably due to the minimization of the peak concentration of H(2)O(2) in the solution, which reduced the probability that valuable H(2)O(2) and hydroxyl radicals would be consumed in forming weaker radicals. The reaction kinetics of the decay of ATZ in stepwise-FP was found to be a two-stage process; and in each stage, fast decay followed by stagnant decay was observed. Two characterized constants (the initial decay rate and the oxidative capacity) were introduced and were found to be useful in quantifying the stepwise-FP. The models for predicting stepwise-FP with respect to different dosing times and/or asymmetrical doses were developed, and were found to be very useful for evaluating the system performance and/or for process design.

An image-based approach to measure the ferric ion diffusion coefficient in fricke gel dosimetry

A numerical method was adopted to solve the diffusion equation to determine ferric ion diffusion coefficient in Fricke-agarose gels. A fast MR acquisition technique was employed to avoid smearing of acquired data due to diffusion over an extended time period. Our results show that for a Fricke gel contained 1 mM ammonium ferrous sulfate, 1% agarose, 1 mM sodium chloride and 50 mM sulfuric acid, its ferric ion diffusion coefficient is 1.73 10^-2cm²h^-1in room temperature. This value is consistent with the 1 ~ 2 10^-2cm²h^-1range obtained by previous studies under varying concentrations of gel ingredients.

Reaction pathways and kinetics of butylated hydroxyanisole with UV, ozonation, and UV/O(3) processes

The chemical degradation of the endocrine disrupting chemical, butylated hydroxyanisole (BHA), was investigated by different treatment processes including ultraviolet (UV) irradiation, ozonation (O(3)), and UV/O(3). O demethylation, dimerization, and oxidation have been found to be the main degradation mechanisms. A systematic decay pathway was proposed based on ten identified intermediates in the studied processes, including a unique pathway leading to the formation of precipitates in the ozonation process. An unconventional minimum-type variation of BHA decay rate constants from acidic to caustic range has been found for both ozonation and UV/O(3) processes. The precipitates formed during ozonation can be removed during the process to optimize the treatment, while the UV/O(3) process can offer a relatively fast and clean process to degrade BHA and its associated intermediates.

The use of oxyhalogen in photocatalytic reaction to remove o-chloroaniline in TiO2 dispersion

Photodecay of o-chloroaniline (o-ClA) in various combinations of UV sources, TiO2, and oxyhalogens was investigated. To improve the conventional photocatalytic process by using UV/TiO2, the addition of oxyhalogens (ClO3(-), BrO3(-) and IO3(-)) into UV/TiO2 system was studied and the effect in such addition is very encouraging for all the selected additives. Oxyhalogens are capable of deferring the electron-hole recombination of TiO2 which significantly improved its catalytic performance. The presence of IO3(-) in UV/TiO2 resulted in the fastest o-ClA decay among three oxhalogens at the same dosage. The decay of o-ClA in UV/TiO2/oxyhalogen process is characterized by a two-stage pseudo-kinetics, where a faster initial decay was followed by a retardation state. A mathematics model was successfully established for the prediction of the two-stage decay of o-ClA in UV/TiO2/IO3(-) with any designed [IO3(-)] concentration.

Degradation of the endocrine disruptor carbofuran by UV, O3 and O3/UV

The photodegradation of a carbamate insecticide, Carbofuran (CBF), which has been recognised as a potential endocrine disrupting chemical, was studied via different wastewater treatment processes. This study has shown the efficiency of advanced oxidation process, AOP (UV/O3) than those of the direct UV photolysis and ozonation process, by completely removing 0.2 mM CBF and achieving 24% mineralisation within 30min. The initial decay of CBF by UV/O3 accelerated from 0.05 to 0.16 min(-1) as the initial pH increasing from 3.0 to 11.3. The pH-dependency of CBF has also been shown in both ozonation and UV/O3 process. A linear relationship could be found for the latter process in all pH, while for the former process, two stages of reactions (steady and accelerating) were found in the acidic and alkaline pH condition, respectively.

Tuberculosis intestinal perforation during anti-tuberculosis treatment

Intestinal perforation is an uncommon but potentially fatal complication of intestinal tuberculosis. We report on a 63-year-old HIV-negative man who developed terminal ileal perforation approximately 3.5 months following initiation of anti-tuberculous treatment for pulmonary tuberculosis and a concomitant tuberculous perianal abscess. Clinical and radiological improvements were initially evident following commencement of anti-tuberculous treatment, and the paradoxical response phenomenon was suspected. The patient subsequently underwent surgical resection of the affected bowel segment with primary anastomosis, and made an uneventful recovery. Anti-tuberculous medication was continued for another 12 months, and after a further 12 months there was no evidence of recurrent tuberculosis. This case illustrates that tuberculous intestinal perforation can develop during chemotherapy for tuberculosis. Prompt diagnosis and appropriate surgical treatment are essential to avoid morbidity and mortality.

Enhancement of ozone oxidation and its associated processes in the presence of surfactant: degradation of atrazine

In this study, the degradation of atrazine (ATZ) by ozone (O3) oxidation and its associated processes (i.e. UV, UV/O3) in the presence and absence of surfactant was investigated and compared. A non-ionic surfactant, Brij 35, was selected. It was found that the presence of a low concentration of surfactant could improve the removal of ATZ by increasing the dissolution of ozone and the indirect generation of hydroxyl radicals. The saturated ozone level and the reaction rate constants were increased with increasing the concentration of surfactant and then decreased at higher surfactant doses at pH level of 2.5. A similar trend was observed at pH level of 7.0 in the presence of bicarbonate ion, because it is capable of deactivating the hydroxyl radicals generating at higher pH level. However, when the radical reactions become dominant in the ozonation (at pH 7.0 without bicarbonate), the saturated ozone level was higher than that with bicarbonate and the kinetic rate constants were increased first and levelled off with increasing of the dose of surfactant. Through the examining of a proposed unit performance index, the low concentration of surfactant is surely beneficial to the ozonation process. Besides, the direct photolysis and photo-assisted ozonation were compared to the ozonation. A significant enhancement on the decay rate of ATZ was resulted exclusively by adding the surfactant. An enhancement index for quantifying the improvement of the various processes was developed.

The partitioning and modelling of pesticide parathion in a surfactant-assisted soil-washing system

Soil sorption of organic pollutants has long been a problematic in the soil washing process because of its durability and low water solubility. This paper discussed the soil washing phenomena over a wide range of parathion concentrations and several soil samples at various fractions of organic content (foc) levels. When parathion dosage is set below the water solubility, washing performance is stable for surfactant concentrations above critical micelle concentration (cmc) and it is observed that more than 90% of parathion can be washed out when dosage is five times lower than the solubility limit. However, such trends change when non-aqueous phase liquids (NAPL) is present in the system. Parathion extraction depends very much on the surfactant dosage but is not affected by the levels of foc in the system. In between the extreme parathion dosage, a two-stage pattern is observed in these boundary regions. Washing performance is first increased with additional surfactant, but the increase slows down gradually since the sorption sites are believed to be saturated by the huge amount of surfactant in the system. A mathematical model has included foc to demonstrate such behavior and this can be used as a prediction for extraction.

Longer term follow up of aerobic capacity in children affected by severe acute respiratory syndrome (SARS)

BACKGROUND

A study was undertaken to investigate the aerobic capacity and pulmonary function of children 6 and 15 months after the diagnosis of severe acute respiratory syndrome (SARS).

METHODS

Thirty four patients of mean age 14.7 years completed both pulmonary function and maximal aerobic capacity tests at 6 months. All had normal clinical examination and were asymptomatic. Their exercise responses were compared with a group of healthy controls. Complete data were collected on 27 of the original 34 cases at 15 months.

RESULTS

Compared with normal controls, the patient group had significantly lower absolute and mass related peak oxygen consumption (peak V o(2) (p<0.01)), higher ventilatory equivalent for oxygen (p<0.01), lower oxygen pulse (p<0.01), and a lower oxygen uptake efficiency slope (p<0.01) at 6 months. This impairment was unexpected and out of proportion with the degree of lung function abnormality. Residual high resolution computed tomography of thorax (HRCT) abnormalities were present in 14 patients. Those with abnormal HRCT findings had significantly lower mass related peak V o(2) than subjects with normal radiology (p<0.01). Absolute and mass related peak V o(2) in the patient group remained impaired at 15 months despite normalisation of lung function in all patients.

CONCLUSIONS

The mechanism for the reduced aerobic capacity in children following SARS is not fully understood, but it is probably a consequence of impaired perfusion to the lungs at peak exercise and deconditioning.