RESUMEN

There has been a controversy over the TiO2 photocatalytic oxidation (PCO) mechanism of As(III) for the last several years. The key argument has been whether superoxide (HO2*/O2(-)*) is the main oxidant of As(III) in the UV/TiO2 system. Previously we and other groups have refuted the claim that superoxide plays the main role in the TiO2 PCO of As(III). Nevertheless, thereafter, the superoxide-mediated As(III) oxidation mechanism has been repeatedly claimed, making it difficult to draw a clear conclusion regarding this mechanism. The objective of this study is to draw a unanimous conclusion on the TiO2 PCO mechanism of As(III) and thus finish the controversy regarding this issue. To investigate the correlation between As(III) oxidation and superoxide, both As(V) and H2O2 were measured simultaneously. When excess formic acid (FA) was added as a scavenger of valence band (VB) hole (or *OH) in UV/TiO2 or vacuum-UV lamp irradiation (lambda = 185 + 254 nm), As(III) oxidation was greatly inhibited while H2O2 generation was promoted. Since H2O2 is photochemically produced through the disproportionation of superoxide, this result definitely shows that superoxide has little role in the oxidation of As(III) not only in UV/TiO2 but also in other advanced oxidation processes (AOPs). Interestingly, not only FA (a scavenger of VB hole) but also methanol (a scavenger of adsorbed *OH) showed an inhibitory effect on the TiO2 PCO of As(III). Excess methanol retarded the TiO2 PCO of As(III) moderately but not completely, which indicates that adsorbed *OH also plays a significant role along with VB hole in the TiO2 PCO of As(III). Although the conclusion is not based on the rate constant between As(III) and superoxide but derived from indirect inference from the experimental data, this study provides convincing evidence to support that adsorbed *OH and VB hole are the main oxidants in the TiO2 PCO mechanism of As(III).

Asunto(s)

Arsénico/química , Fotoquímica , Titanio/química , Catálisis , Formiatos/química , Peróxido de Hidrógeno/química , Metanol/química , Oxidación-Reducción

RESUMEN

This study focuses on the enhanced decomposition of pentachlorophenol (PCP) in an electron beam (E-beam) process. To attain this objective, we investigated a synergistic effect of ferric-ethylenediamineacetate (Fe(III)-EDTA) and H(2)O(2) as additives to produce additional hydroxyl radical (*OH) at low dose. In this process, aqueous electron and hydrogen atom rapidly react with O(2) molecules, thereby forming hydroperoxyl/superoxide anion radical (HO2*/O(2)(-)), which reduces the Fe(III)-EDTA into Fe(II)-EDTA. Further *OH is produced by a well-known Fenton-like reaction of Fe(II)-EDTA with H(2)O(2) formed newly in E-beam. The complete decomposition of the initial PCP at 0.1mM was enhanced even at very low dose (<10 kGy) with 20 microM Fe(III)-EDTA and H(2)O(2) less than 1mM. This observation was supported by the increased amount of Cl(-) produced by the decomposition of PCP. Thus, in the presence of Fe(III)-EDTA during E-beam irradiation, the HO2*/O(2)(-)-driven Fenton-like reaction produces much more ()OH, which is significant for the complete degradation of PCP.

Asunto(s)

Compuestos Férricos/química , Pentaclorofenol/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Ácido Edético/química , Electrones , Peróxido de Hidrógeno/química , Oxidación-Reducción

RESUMEN

In this study, vacuum-UV (VUV) lamp irradiation emitting both 185 and 254 nm lights has been investigated as a new oxidation method for As(III). Laboratory scale experiments were conducted with a batch reactor and a commercial VUV lamp. Under the experimental conditions of this study, the employed VUV lamp showed a higher performance for As(III) oxidation compared to other photochemical oxidation methods (UV-C/H(2)O(2), UV-A/Fe(III)/H(2)O(2), and UV-A/TiO2). The VUV lamp oxidized 100 microM As(III) almost completely in 10 min, and the reaction occurred mainly due to OH radicals which were produced by photo-splitting of water (H(2)O+hv (lambda=185 nm)-->OH.+H.). There was a little possibility that photo-generated H(2)O(2) acted as a minor oxidant of As(III) at alkaline pHs. The effects of Fe(III), H(2)O(2), and humic acid (HA) on the As(III) oxidation by VUV lamp irradiation were investigated. While Fe(III) and H(2)O(2) increased the As(III) oxidation efficiency, HA did not cause a significant effect. The employed VUV lamp was effective for oxidizing As(III) not only in a Milli-Q water but also in a real natural water, without significant decrease in the oxidation efficiency. Since the formed As(V) should be removed from water, activated alumina (AA) was added as an adsorbent during the As(III) oxidation by VUV lamp irradiation. The combined use of VUV lamp irradiation and AA was much more effective for the removal of total arsenic (As(tot)=As(III)+As(V)) than the single use of AA. The As(tot) removal seemed to occur as a result of the pre-oxidation of As(III) and the subsequent adsorption of As(V) on AA. Alternatively, the combination of VUV lamp irradiation and coagulation/precipitation with FeCl(3) was also an effective removal strategy for As(tot). This study shows that vacuum-UV (VUV) lamp irradiation emitting both 185 and 254 nm lights is a powerful and environmentally friendly method for As(III) oxidation which does not require additional oxidants or catalysts. The As(III) oxidation by VUV lamp irradiation was tested not only in a batch reactor but also in a flow-through quartz reactor. The As(III) oxidation rate became much faster in the latter reactor.

Asunto(s)

Arsénico/química , Rayos Ultravioleta , Agua/química , Arsénico/aislamiento & purificación , Sustancias Húmicas , Peróxido de Hidrógeno/química , Hierro/química , Oxidación-Reducción/efectos de la radiación , Fotoquímica , Vacio

RESUMEN

An HPLC system was automated for the measurement of gaseous hydroperoxides in the ambient air. In this system, samples collected using a glass coil without a long sampling tube are injected automatically into HPLC. The analytical system is based on the post-column derivatization, which is a reaction of hydroperoxides with p-hydroxyphenyl acetic acid to produce a fluorescent dimer in the presence of horseradish peroxidase as an enzyme catalyst. The detection limits of hydrogen peroxide (H(2)O(2)) were from 0.018 to 0.042 ppbv. The gaseous hydroperoxides were measured in Gwangju during March, May and October 2002, and in Seoul during June 2002. H(2)O(2) concentrations were remarkably low and almost at the detection limit during a period of the yellow sand (Asian dust). These results might be strongly ascribed to the effect of Asian dust particles for heterogeneous loss of peroxides and partly loss of samples due to the storage of sample and analysis. Methyl hydroperoxide (CH(3)OOH) was identified and quantified only in Seoul. The highest concentrations of H(2)O(2) were 0.24, 2.84, and 0.89 ppbv during March, May, October, respectively in Gwangju, and 5.19 ppbv in Seoul. The concentration of CH(3)OOH was as high as 1.1 ppbv and sometimes its concentration was higher than that of H(2)O(2) in the early morning or in the late night. The variability of CH(3)OOH was lower than that of H(2)O(2). H(2)O(2) showed a positive relationship with O(3) (r = 0.54, P < 0.01 level; two-tailed), solar radiation (r = 0.61, P < 0.01 level; two-tailed), temperature (r = 0.66, P < 0.01 level; two-tailed), and a negative relationship with NO( x ) (r = -0.20, P < 0.05 level; two-tailed), and relative humidity (r = -0.58, P < 0.01 level; two-tailed) in Seoul. Thus, photochemical activity is considered an important factor in gaseous H(2)O(2) and CH(3)OOH distribution.

Asunto(s)

Contaminantes Atmosféricos/análisis , Cromatografía Líquida de Alta Presión/métodos , Peróxido de Hidrógeno/análisis , Corea (Geográfico) , Reproducibilidad de los Resultados

RESUMEN

An enhanced dual coil 2,4-dinitrophenylhydrazine (DNPH) derivatization method (dual coil/DNPH) allowed the quantitative determination of formaldehyde (HCHO) in ambient air. In this method, traceable HCHO was collected using a coil sampler connected in series and lacking a long sampling tube. It was then analyzed using liquid chromatography followed by UV detection of the DNPH derivatives. The method is based on the reaction of formaldehyde with DNPH to produce 2,4-dinitrophenylhydrazone. The detection limits (3sigma) were 0.10-0.40 ppbv with a precision ranging from 0.84 to 4.09% RSD. The results of dual coil/DNPH and conventional DNPH cartridge methods were generally well correlated: HCHO (dual coil/DNPH)=0.97 (+/-0.13) vs. HCHO (DNPH Cartridge)+0.33 (+/-0.33), r=0.82. The dual coil/DNPH method was used to measure gaseous HCHO in the atmosphere of Metropolitan Seoul during the summer 2000 and 2001, and in Gwangju during the fall of 2001 and 2002. The daytime mean concentration of HCHO was 4.52 (+/-5.69) and 3.21 (+/-1.27) ppbv in Metropolitan Seoul for 10-12 August 2000 and 29-31 May 2001, respectively, and 1.73 (+/-0.98), 3.04 (+/-2.25), 2.70 (+/-1.70), and 2.01 (+/-2.28) ppbv in Gwangju City during 22-27 September 2001, 17-24 October 2001, 9-13 October 2002, and 28 October to 2 November 2002, respectively. The HCHO in Seoul from 10-12 August 2000 was mainly the result of photochemical processes, while direct emissions from vehicles and long-range transport of air from China contributed during 29-31 May 2001. During 22-27 September 2001, 17-24 October 2001, and 9-13 October 2002 in Gwangju, the HCHO came primarily from photochemical processes, although some air affected by biomass burning admixed in the late afternoon. The increase in the HCHO concentration on 20 October 2001 and from 28 October to 2 November 2002 was attributed mainly to direct emissions from biomass burning in farmland near the measurement site.

Asunto(s)

Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente/instrumentación , Formaldehído/análisis , Monitoreo del Ambiente/métodos , Corea (Geográfico) , Fotoquímica , Emisiones de Vehículos

RESUMEN

Traumatic or inflammatory injury associates with deactivation of monocytes and impaired synthesis of proinflammatory cytokines. We conducted a prospective, observational study to test whether cardiac surgery additionally impaired dendritic and natural killer (NK) cell functions responsible for innate immune production of interleukin (IL)-12-dependent interferon (IFN)-gamma in response to bacteria or toll-like receptor agonists. Blood samples were taken just before induction of anesthesia and 24 h postoperatively. LPS- and fixed Staphylococcus aureus-inducible IFNgamma synthesis in whole blood culture after surgery was reduced to 5% of preoperative values (P < 0.001). Production of IL-12 p70, a critical inducer of IFNgamma in the innate immune response, was reduced to 30% of that produced by preoperative samples (P = 0.013). Circulating CD11c, DR myeloid dendritic cells (DC) that are known sources of IL-12 p70 in normal blood, declined to approximately 25% of presurgical numbers (P = 0.004). Experimental depletion of CD11c, but not CD14, cells from normal peripheral blood mononuclear cell (PBMC) similarly disabled Staphylococcus aureus Cowan 1 (SAC)-induced production of IL-12 p70 and IFNgamma. Consistent with SAC-induced IFNgamma expression in CD56 NK and NK-T cells, CD56 depletion ablated IFNgamma production in normal whole blood. However, repletion of IL-12 p70, IL-18, IL-15, and IL-23 in postoperative blood failed to restore presurgical levels of IFNgamma synthesis (P < 0.05). We conclude that DC cytopenia after major surgery is sufficient to explain postoperative IL-12 p70 and IFNgamma synthetic deficiency. In addition, postoperative blood became hyporesponsive to IFNgamma-inducing cytokines as a further contribution to IFNgamma insufficiency. The novel finding of DC cytopenia after major surgery may portend a lack of other immunologic functions provided by this potent accessory cell population.

Asunto(s)

Células Dendríticas/inmunología , Células Dendríticas/patología , Interferón gamma/deficiencia , Interleucina-12/deficiencia , Cirugía Torácica , Interferón gamma/biosíntesis , Interleucina-10/farmacología , Interleucina-18/farmacología , Interleucina-23 , Interleucinas/farmacología , Pruebas de Neutralización , Complicaciones Posoperatorias/inmunología , Subunidades de Proteína , Proteínas Recombinantes/metabolismo

RESUMEN

Although it is well-known that As(III) is oxidized to As(V) in the UV/TiO2 system, the main oxidant for that reaction is still not clear. Accordingly, the present study aims at reinvestigating the TiO2-photocatalyzed oxidation mechanism of As(III). We performed a series of As(II) oxidation experiments by using UV-C/H2O2 and UV-A/TiO2, focusing on the effects of competing compounds. The experiment with UV-C/H2O2 indicated that HO2*/O2-* is not an effective oxidant of As(III) in the homogeneous phase. The effects of oxalate, formate, and Cu(II) on the photocatalytic oxidation of As(III) contradicted the controversial hypothesis that HO2*/ O2-* is the main oxidant of As(III) in the UV/TiO2 system. The effect of As(III) on the TiO2-photocatalyzed oxidations of benzoate, terephthalate, and formate was also incompatible with the superoxide-based As(II) oxidation mechanism. Instead, the experimental observations implied that OH* and/or the positive hole are largely responsible forthe oxidation of As(III) in the UV/TiO2 system. To determine which species plays a more significant role, the effects of methanol and iodide were tested. Since excess methanol did not retard the oxidation rate of As(III), OH* seems not to be the main oxidant. Therefore, the best rationale regarding the oxidation mechanism of As(III) in the UV/TiO2 system seems to be the direct electron transfer between As(III) and positive holes. Only with this mechanism, it was possible to explain the data of this study. Besides the mechanistic aspect, an application method for this technology was sought. The usage of UV/TiO2 for oxidizing As(II) requires a posttreatment in which both As(V) and TiO2 should be removed from water. For this objective, we applied FeCl3 and AIK(SO4)2 as coagulants, and the result implied that the combined usage of TiO2 and coagulation might be a feasible solution to treat arsenic contamination around the world.

Asunto(s)

Arsénico/química , Oxidantes Fotoquímicos/química , Titanio/química , Rayos Ultravioleta , Purificación del Agua/métodos , Adsorción , Compuestos de Alumbre/química , Catálisis , Cloruros , Compuestos Férricos/química , Peróxido de Hidrógeno/química , Radical Hidroxilo/química , Oxidación-Reducción , Oxígeno/química , Fotoquímica , Factores de Tiempo

RESUMEN

A new kinetic method is developed for the determination of hydroperoxyl radical (HO(2)(*))/superoxide radical (O(2)(*)(-)) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO(2)(*)/O(2)(*)(-) as produced in the UV/H(2)O(2) process. This new method is based on the reduction of Fe(3+)-EDTA into Fe(2+)-EDTA by HO(2)(*)/O(2)(*)(-) and the well-known Fenton-like reaction of H(2)O(2) and Fe(2+)-EDTA to yield the hydroxyl radicals (OH(*)). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (lambda(ex) = 320 nm; lambda(em) = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 x 10(-)(11) M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interferences often found in aqueous phase.

RESUMEN

The sonolytic degradation of methyl tert-butyl ether (MTBE) has been investigated at ultrasonic frequency of 20 kHz. The observed pseudo-first-order rate constant decreased from 1.25 x 10(-4) to 5.32 x 10(-5) s(-1) as the concentration of MTBE increased from 2.84 x 10(-2) to 2.84 x 10(-1) mM. The rate of degradation of MTBE increased with the increase of the power density of ultrasonicator and also with the rise in reactor system temperature. In the presence of oxidising agent, potassium persulphate, the sonolytic rate of degradation of MTBE was accelerated substantially. Tert-butyl formate (TBF) and acetone were found to be the major intermediates of the degradation of MTBE. It is found that the ultrasound/Fe2+/H2O2 method is promising process for the degradation of MTBE. More than 95% degradation of MTBE (2.84 x 10(-2) mM) along with its intermediate products has been achieved during the coupled ultrasound/Fe2+/ H2O2 method. Hence, the coupled ultrasound/Fe2+/H2O2 may be a viable method for the degradation MTBE within a short period of time than the ultrasound irradiation process only. A kinetic model, based on the initial rates of degradation of MTBE and TBF, provides a good agreement with the experimental results.

Asunto(s)

Carcinógenos/química , Éteres Metílicos/química , Modelos Teóricos , Solventes/química , Purificación del Agua/métodos , Peróxido de Hidrógeno/química , Hierro/química , Contaminantes del Suelo , Ultrasonido , Abastecimiento de Agua

RESUMEN

INTRODUCTION: We hypothesized that in humans there is an epicardial fat pad from which parasympathetic ganglia supply the AV node. We also hypothesized that the parasympathetic nerves innervating the AV node also innervate the right atrium, and the greatest density of innervation is near the AV nodal fat pad. METHODS AND RESULTS: An epicardial fat pad near the junction of the left atrium and right inferior pulmonary vein was identified during cardiac surgery in seven patients. A ring electrode was used to stimulate this fat pad intraoperatively during sinus rhythm to produce transient complete heart block. Subsequently, temporary epicardial wire electrodes were sutured in pairs on this epicardial fat pad, the high right atrium, and the right ventricle by direct visualization during coronary artery bypass surgery in seven patients. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness at each catheter site was determined in the presence and absence of parasympathetic nerve stimulation (via the epicardial wires). In all seven patients, an AV nodal fat pad was identified. Fat pad stimulation during and after surgery caused complete heart block but no change in sinus rate. Fat pad stimulation decreased the right atrial effective refractory period at 1 cm (280 +/- 42 msec to 242 +/- 39 msec) and 2 cm (235 +/- 21 msec to 201 +/- 11 msec) from the fat pad (P = 0.04, compared with baseline). No significant change in atrial refractoriness occurred at distances >2 cm. The response to stimulation decreased as the distance from the fat pad increased. CONCLUSION: For the first time in humans, an epicardial fat pad was identified from which parasympathetic nerve fibers selectively innervate the AV node but not the sinoatrial node. Nerves in this fat pad also innervate the surrounding right atrium.

Asunto(s)

Nodo Atrioventricular/inervación , Nodo Atrioventricular/patología , Sistema Nervioso Parasimpático/patología , Tejido Adiposo/efectos de los fármacos , Tejido Adiposo/inervación , Adulto , Anciano , Antiarrítmicos/administración & dosificación , Nodo Atrioventricular/efectos de los fármacos , Atropina/administración & dosificación , Puente de Arteria Coronaria , Enfermedad de la Arteria Coronaria/cirugía , Estimulación Eléctrica , Electrodos Implantados , Técnicas Electrofisiológicas Cardíacas , Femenino , Atrios Cardíacos/efectos de los fármacos , Atrios Cardíacos/inervación , Atrios Cardíacos/patología , Humanos , Inyecciones Intravenosas , Masculino , Persona de Mediana Edad , Ohio , Sistema Nervioso Parasimpático/efectos de los fármacos , Pericardio/efectos de los fármacos , Pericardio/inervación , Resultado del Tratamiento

RESUMEN

A 70-year-old woman with a known chronic dissecting aneurysm of the descending thoracic aorta presented with new-onset back pain and hemoptysis. The hemoptysis was thought to be the result of invasion of the bronchial tree by the aneurysm. During surgical repair, a lesion that appeared to be a pulmonary abscess was discovered to be adhering to the aortic tissue, and the patient underwent a localized pulmonary resection. The pathology report of the surgical specimens revealed squamous cell carcinoma of the lung with infiltration of the aortic wall. The patient died of lung cancer 6 months later. Hemoptysis was an unusual presentation in a case of lung cancer that had invaded a stable chronic aortic aneurysm.

Asunto(s)

Aneurisma de la Aorta Torácica/complicaciones , Disección Aórtica/complicaciones , Carcinoma de Células Escamosas/complicaciones , Hemoptisis/etiología , Neoplasias Pulmonares/complicaciones , Anciano , Disección Aórtica/cirugía , Aneurisma de la Aorta Torácica/cirugía , Carcinoma de Células Escamosas/patología , Resultado Fatal , Femenino , Hemoptisis/cirugía , Humanos , Neoplasias Pulmonares/patología , Invasividad Neoplásica

RESUMEN

OBJECTIVE: To compare outcomes and cost of off-pump coronary artery bypass (OP-CAB) surgery versus cardiopulmonary bypass-assisted coronary artery bypass graft (CABG) surgery. DESIGN: Retrospective review. SETTING: A tertiary care university teaching hospital. PARTICIPANTS: Patients (n = 300) undergoing isolated CABG surgery performed by a single surgeon between July 1998 and February 2000. INTERVENTIONS: Two groups of patients were compared: 150 consecutive patients undergoing OP-CAB surgery and a matched cohort of 150 consecutive patients undergoing conventional CABG surgery. MEASUREMENTS AND MAIN RESULTS: The 2 groups were evenly matched in terms of age and incidence of diabetes, hypertension, peripheral vascular disease, left main disease, prior strokes, congestive heart failure, and recent infarctions. OP-CAB procedures required 3.3 grafts per patient versus 3.8 grafts per patient required for CABG surgery (p = 0.02). Overall mortality was 2.0% (1.3% in the OP-CAB surgery group v 2.7 % in the CABG surgery group; p = NS). Extubation times (6.6 hours v 9.5 hours; p = 0.003), surgical intensive care unit length of stay (39 hours v 49 hours; p = 0.03), and hospital length of stay (6.1 days v 7.0 days; p = 0.04) were all significantly shorter for the OP-CAB surgery group. The combined aggregate endpoints of death and major morbidity were significantly less in the OP-CAB surgery group (5.3% v 12.7%; p = 0.02). CONCLUSION: OP-CAB surgery is associated with low morbidity and mortality and accelerated recovery compared with conventional CABG surgery. OP-CAB surgery may represent the ideal revascularization strategy for patients at high risk for undergoing cardiopulmonary bypass.

Asunto(s)

Puente Cardiopulmonar/efectos adversos , Puente de Arteria Coronaria/efectos adversos , Adulto , Anciano , Anciano de 80 o más Años , Puente Cardiopulmonar/mortalidad , Estudios de Cohortes , Puente de Arteria Coronaria/métodos , Puente de Arteria Coronaria/mortalidad , Femenino , Humanos , Tiempo de Internación , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Tasa de Supervivencia

RESUMEN

INTRODUCTION: Elderly patients undergoing coronary bypass surgery after acute myocardial infarction represent a distinct, high risk subgroup. We sought to identify independent risk factors for mortality in a series of patients operated on in our hospital. METHODS: The case records of 499 consecutive patients greater than 70 years were identified, and 94 of these patients underwent urgent/emergent coronary bypass surgery within 7 days of acute myocardial infarction. Patients received either cold (4°C) or tepid (32°C) cardioplegia for myocardial protection. RESULTS: Mortality for the tepid cardioplegia group was 0/33, and the mortality for the cold cardioplegia group was 12/61 (0% vs. 20%, p equals 0.003). Multivariate analysis demonstrated left ventricular dysfunction and cold blood cardioplegia to be independent predictors of mortality. CONCLUSION: The type of myocardial protection technique is a significant predictor of mortality, and tepid cardioplegia may provide significant advantages to this high risk patient population.