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1.
Am J Gastroenterol ; 2024 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-39016385

RESUMEN

INTRODUCTION: The prevalence of metabolic dysfunction-associated fatty liver disease (MAFLD) and its complication, MAFLD-related acute-on-chronic liver failure (MAFLD-ACLF), is rising. Yet, factors determining patient outcomes in MAFLD-ACLF remain understudied. METHODS: Patients with MAFLD-ACLF were recruited from the Asian Pacific Association for the Study of the Liver-ACLF Research Consortium (AARC registry). The diagnosis of MAFLD-ACLF was made when the treating unit had identified the etiology of chronic liver disease as MAFLD (or previous nomenclature such as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, or non-alcoholic steatohepatitis-cirrhosis). Patients with coexisting other etiologies of chronic liver disease (such as alcohol, hepatitis B virus, hepatitis C virus, etc.) were excluded. Data were randomly split into derivation (n = 258) and validation (n = 111) cohorts at a 70:30 ratio. The primary outcome was 90-day mortality. Only the baseline clinical, laboratory features and severity scores were considered. RESULTS: The derivation group had 258 patients; 60% were male, with a mean age of 53. Diabetes was noted in 27% and hypertension in 29%. The dominant precipitants included viral hepatitis (hepatitis A virus and hepatitis E virus, 32%), drug-induced injury (drug-induced liver injury, 29%), and sepsis (23%). Model for End-Stage Liver Disease-Sodium (MELD-Na) and AARC scores on admission averaged 32 ± 6 and 10.4 ± 1.9. At 90 days, 51% survived. Nonviral precipitant, diabetes, bilirubin, international normalized ratio, and encephalopathy were independent factors influencing mortality. Adding diabetes and precipitant to MELD-Na and AARC scores, the novel MAFLD-MELD-Na score (+12 for diabetes, +12 for nonviral precipitant), and MAFLD-AARC score (+5 for each) were formed. These outperformed the standard scores in both cohorts. DISCUSSION: Almost half of patients with MAFLD-ACLF die within 90 days. Diabetes and nonviral precipitants such as drug-induced liver injury and sepsis lead to adverse outcomes. The new MAFLD-MELD-Na and MAFLD-AARC scores provide reliable 90-day mortality predictions for patients with MAFLD-ACLF.

2.
Liver Int ; 43(1): 77-89, 2023 01.
Artículo en Inglés | MEDLINE | ID: mdl-36300646

RESUMEN

BACKGROUND/AIMS: Novel agents acting against hepatitis B virus (HBV) are needed to improve HBsAg seroclearance or termed as 'functional cure'. Inarigivir (retinoic acid-inducible gene I agonist) has immunomodulatory and direct antiviral actions against HBV. We aimed to determine the safety and efficacy of Inarigivir for the treatment of HBV infection. PATIENTS/METHODS: 80 treatment-naïve patients were randomized in 4 ascending dose cohorts to receive 12 weeks of Inarigivir 25, 50, 100, 200 mg or placebo in a ratio of 4:1. All patients were then given tenofovir for another 12 weeks. RESULTS: Least squares (LS) mean reductions in HBV DNA from baseline increased with higher doses of Inarigivir (0.6116 in 25 mg and 1.5774 in 200 mg groups vs. 0.0352 in placebo group) (95% CI 0.9518-0.2011 and 1.921-1.1634 respectively). LS mean changes in HBV RNA and HBsAg from baseline ranged from -0.3856 to -0.5794 versus -0.1474 and -0.0956 to -0.1818 versus +0.0026 in Inarigivir-treated versus placebo groups respectively. During the tenofovir-treated period, LS mean reductions in HBsAg in the Inarigivir-treated groups ranged from 0.1709 to 0.3529 versus 0.1984 in the placebo group. Inarigivir-treated groups showed mean reductions in ALT from baseline between 23.3 and 33.8 versus 0.7 U/L in the placebo group. Treatment-emergent adverse events related to Inarigivir and placebo occurred in 4.7% and 6.3% patients respectively. CONCLUSIONS: Twelve-week Inarigivir up to 200 mg dose was associated with a reduction of HBV DNA, HBV RNA and antigen levels. A trend for greater HBsAg reduction was observed in Inarigivir pre-treated patients after switching to tenofovir.


Asunto(s)
Hepatitis B Crónica , Hepatitis B , Humanos , Antígenos de Superficie de la Hepatitis B , ADN Viral , Tenofovir/uso terapéutico , Antivirales/efectos adversos , Hepatitis B/tratamiento farmacológico , Virus de la Hepatitis B/genética , Antígenos e de la Hepatitis B , ARN , Resultado del Tratamiento
3.
J Cardiovasc Surg (Torino) ; 63(1): 37-43, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34014056

RESUMEN

BACKGROUND: This study aimed to investigate the impact of segmental artery reimplantation and its patency on spinal cord ischemia (SCI) in thoracoabdominal aorta replacement. METHODS: For 193 patients who underwent early postoperative computed tomographic (CT) angiography after thoracoabdominal aorta replacement, the technique of segmental artery reimplantation, their patency, and postoperative SCI were retrospectively investigated. RESULTS: The early patency rate of reimplanted segmental artery was 83.3% (210 of 252), as 13 were taken down intraoperatively and 42 were not visualized in the postoperative CT angiography. The patency rate differed according to the reimplantation technique: 93.6% (131/140) for en bloc patch, 95.6% (43/45) for small individual patch, and 53.7% (36/67) for graft interposition. SCI occurred in 13 (6.3%) patients, 4 of whom (2.0%) remained paraplegic permanently. SCI was significantly more frequent (P=0.044) in the patients in whom segmental artery reimplantation was not successful (take-down or occlusion, 6/37=16.2%) than in those who had all segmental arteries sacrificed intentionally (2/64=3.1%) and those who showed patency of all reimplanted segmental arteries (5/92=5.4%). Especially, there was no permanent paraplegia in the last group. Failure of intended segmental artery reimplantation was a significant risk factor of postoperative SCI in logistic regression analysis (P=0.012; odds ratio 4.65, 95% confidence interval 1.41-15.36). CONCLUSIONS: During thoracoabdominal aorta replacement, attention should be paid to the segmental artery reimplantation technique, which affects the risk of occlusion or intraoperative take-down and thereby may have impact on postoperative SCI.


Asunto(s)
Aorta Abdominal/cirugía , Aorta Torácica/cirugía , Implantación de Prótesis Vascular/efectos adversos , Isquemia de la Médula Espinal/epidemiología , Grado de Desobstrucción Vascular , Aorta Abdominal/diagnóstico por imagen , Aorta Abdominal/fisiopatología , Aorta Torácica/diagnóstico por imagen , Aorta Torácica/fisiopatología , Aortografía , Angiografía por Tomografía Computarizada , Humanos , Incidencia , Reimplantación , Estudios Retrospectivos , Medición de Riesgo , Factores de Riesgo , Isquemia de la Médula Espinal/diagnóstico por imagen , Isquemia de la Médula Espinal/fisiopatología , Factores de Tiempo , Resultado del Tratamiento
5.
Medicine (Baltimore) ; 97(25): e11253, 2018 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-29924056

RESUMEN

BACKGROUND: Endoscopic inspection of colonic mucosa is disturbed by colonic folds and peristalsis, which may result in missed polyps. Cimetropium bromide, an antispasmodic agent, inhibits peristalsis and colonic spasms, which may improve polyp detection. The purpose of this randomized, double-blind, placebo-controlled study was to investigate whether cimetropium bromide could improve polyp and adenoma detection in the colorectum and right colon. METHODS: Patients undergoing screening or diagnostic colonoscopy were randomized to receive intravenous cimetropium bromide (5 mg) or placebo after cecal intubation. The primary outcomes were the number of polyps per patient (PPP) and adenomas per patient (APP); secondary outcomes were the polyp detection rate (PDR), adenoma detection rate (ADR), and advanced neoplasm detection rate (ANDR). RESULTS: A total of 181 patients were analyzed; 91 patients received cimetropium bromide and 90 patients received placebo. Cimetropium bromide and placebo groups did not significantly differ in the PPP and APP for the colorectum (1.38 ±â€Š1.58 vs 1.69 ±â€Š2.28, P = .298; 0.96 ±â€Š1.27 vs 1.11 ±â€Š1.89, P = .517, respectively) and right colon (0.70 ±â€Š0.95 vs 0.78 ±â€Š1.21, P = .645; 0.47 ±â€Š0.81 vs 0.51 ±â€Š0.81, P = .757, respectively). Two groups also did not significantly differ in the PDR, ADR, and ANDR for the colorectum and right colon. Furthermore, there were no difference between groups in the PPP, APP, PDR, ADR, and ADNR in a sub-analysis of expert and non-expert endoscopists. CONCLUSIONS: Cimetropium bromide did not improve polyp and adenoma detection in the colorectum and right colon during colonoscope withdrawal, regardless of the expertness of the endoscopist. However, its use may be helpful in patients with active peristalsis or for beginning endoscopists during standard colonoscopy without a transparent cap.


Asunto(s)
Adenoma/diagnóstico , Pólipos del Colon/diagnóstico , Colonoscopios/estadística & datos numéricos , Neoplasias Colorrectales/diagnóstico , Derivados de Escopolamina/administración & dosificación , Adenoma/patología , Administración Intravenosa , Anciano , Pólipos del Colon/patología , Colonoscopía/métodos , Neoplasias Colorrectales/patología , Detección Precoz del Cáncer/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Evaluación de Resultado en la Atención de Salud , Parasimpatolíticos/administración & dosificación , Peristaltismo/efectos de los fármacos
6.
J Gastroenterol Hepatol ; 32(12): 1989-1997, 2017 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28374414

RESUMEN

BACKGROUND AND AIM: Systemic inflammatory response syndrome (SIRS) is an early marker of sepsis and ongoing inflammation and has been reported in large proportion of acute-on-chronic liver failure (ACLF) patients. Whether sepsis is the cause or the result of liver failure is unclear and is vital to know. To address this, the study investigated the course and outcome of ACLF patients without SIRS/sepsis. METHODS: Consecutive ACLF patients were monitored for the development of SIRS/sepsis and associated complications and followed till 90 days, liver transplant or death. RESULTS: Of 561 patients, 201 (35.8%) had no SIRS and 360 (64.2%) had SIRS with or without infection. New onset SIRS and sepsis developed in 74.6% and 8% respectively in a median of 7 (range 4-15) days, at a rate of 11% per day. The cumulative incidence of new SIRS was 29%, 92.8%, and 100% by days 4, 7, and 15. Liver failure, that is, bilirubin > 12 mg/dL (odds ratio [OR] = 2.5 [95% confidence interval {CI} = 1.05-6.19], P = 0.04) at days 0 and 4, and renal failure at day 4 (OR = 6.74 [95%CI = 1.50-13.29], P = 0.01), independently predicted new onset SIRS. Absence of SIRS in the first week was associated with reduced incidence of organ failure (20% vs 39.4%, P = 0.003), as was the 28-day (17.6% vs 36%, P = 0.02) and 90-day (27.5% vs 51%,P = 0.002) mortality. The 90-day mortality was 61.6% in the total cohort and that for those having no SIRS and SIRS at presentation were 42.8% and 65%, respectively (P < 0.001). CONCLUSION: Liver failure predicts the development of SIRS. New onset SIRS in the first week is an important determinant of early sepsis, organ failure, and survival. Prompt interventions in this 'golden window' before development of sepsis may improve the outcome of ACLF.


Asunto(s)
Insuficiencia Hepática Crónica Agudizada/complicaciones , Insuficiencia Hepática Crónica Agudizada/terapia , Síndrome de Respuesta Inflamatoria Sistémica/etiología , Insuficiencia Hepática Crónica Agudizada/diagnóstico , Insuficiencia Hepática Crónica Agudizada/mortalidad , Adulto , Femenino , Humanos , Trasplante de Hígado , Masculino , Persona de Mediana Edad , Insuficiencia Multiorgánica/etiología , Insuficiencia Multiorgánica/prevención & control , Estudios Prospectivos , Sepsis/etiología , Sepsis/prevención & control , Tasa de Supervivencia , Síndrome de Respuesta Inflamatoria Sistémica/prevención & control , Factores de Tiempo
7.
Am J Gastroenterol ; 111(11): 1582-1590, 2016 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-27575713

RESUMEN

OBJECTIVES: Propranolol has been used as prophylaxis for variceal bleeding in patients with cirrhosis. More recent data suggest that carvedilol may be more effective for reducing the hepatic venous pressure gradient (HVPG) than propranolol. The primary aim of this study was to evaluate the hemodynamic response to carvedilol compared with propranolol. METHODS: A total of 110 patients with a baseline HVPG value >12 mm Hg were allocated randomly to receive either carvedilol or propranolol. The HVPG measurement was repeated after 6 weeks of daily medication. The primary end point was a ≥20% fall in HVPG compared with baseline or <12 mm Hg. RESULTS: The difference in the proportion of responders in the carvedilol (49.1%) vs. propranolol (30.9%) groups did not reach statistical significance in the intention-to-treat analysis (P=0.08). However, among patients with a model for end-stage liver disease (MELD) score ≥15, carvedilol resulted in a significantly greater response than that of propranolol (7/12, 58.3% vs. 0/10, 0%; P=0.005). Similarly, carvedilol was superior to propranolol in patients with Child-Pugh score ≥9 (46.2 vs. 0%; P=0.046). The presence of ascites also had a significant influence on the response rate (51.5 vs. 24.2%; P=0.042). A MELD score ≥15 was the only significant predictor of response among these post hoc groups after adjusting for multiple comparisons (P=0.005). Severe adverse events were higher in the carvedilol group although drug-associated adverse events were not different. CONCLUSIONS: Overall, carvedilol offered no clear advantage over propranolol but it may be more effective in advanced cirrhotic patients with a MELD score≥15 in reducing the portal pressure gradient. However, this potential benefit may come with a cost of increased risk of side-effects and outcome data over a longer term is needed to understand the relative risk benefit.


Asunto(s)
Antihipertensivos/uso terapéutico , Carbazoles/uso terapéutico , Hipertensión Portal/tratamiento farmacológico , Presión Portal , Propanolaminas/uso terapéutico , Propranolol/uso terapéutico , Adulto , Ascitis/etiología , Carvedilol , Enfermedad Hepática en Estado Terminal , Várices Esofágicas y Gástricas/complicaciones , Femenino , Hemorragia Gastrointestinal/etiología , Hemorragia Gastrointestinal/prevención & control , Hemodinámica , Venas Hepáticas , Humanos , Hipertensión Portal/etiología , Cirrosis Hepática/complicaciones , Modelos Logísticos , Masculino , Persona de Mediana Edad , Análisis Multivariante , Oportunidad Relativa , Índice de Severidad de la Enfermedad , Resultado del Tratamiento
8.
Eur J Phys Rehabil Med ; 52(1): 28-35, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26334362

RESUMEN

BACKGROUND: In patients with neuromuscular disease and a forced vital capacity (FVC) of <30% of the predictive value, scoliosis correction operation was not recommended because of the possibility of subsequent complications. However, recent reports suggest that the operation can be performed safelyeven in these patients. AIM: This study aimed to determine the usefulness of pulmonary rehabilitation for scoliosis operation, in cases of patients with a low FVC. DESIGN: A retrospective study of a clinical case series SETTING: Inpatients of a university hospital POPULATION: Neuromuscular patients with a low FVC who received mechanical correction of scoliosis (N.=24). METHODS: End-tidal or transcutaneous carbon dioxide was monitored and noninvasive intermittent positive pressure ventilation was applied as needed to maintain normal carbon dioxide concentration. Air stacking, manually assisted coughing and mechanical insufflation-exsufflation were used to maintain normal oxygen saturation. RESULTS: A total of 24 patients of neuromuscular disease (mean age: 15.2 years; average FVC: 19.2%) were included Noninvasive intermittent positive pressure ventilator (NIPPV) was applied in 22 of the 24 patients. The endotracheal tubes of all except two patients were removed within 3 days after the operation, and they were transferred to the general ward within 3 days of extubation. Eight patients had complications, such as pneumonia, wound infection, heart failure, and debility, which were controlled easily with medical management, there were neither life-threatening complications nor a need for an invasiverespiratory intervention. CONCLUSION: Through pulmonary rehabilitation, scoliosis correction surgery could be performed safely even in patients with a neuromuscular disease and a low FVC. CLINICAL REHABILITATION IMPACT: The findings of this study can be used as a basis for practical guidelines for successful and safe mechanical correction of neuromuscular scoliosis.


Asunto(s)
Enfermedades Neuromusculares/complicaciones , Terapia Respiratoria , Escoliosis/rehabilitación , Escoliosis/cirugía , Fusión Vertebral/efectos adversos , Fusión Vertebral/rehabilitación , Adolescente , Análisis de los Gases de la Sangre , Femenino , Humanos , Masculino , Enfermedades Neuromusculares/rehabilitación , Enfermedades Neuromusculares/cirugía , Recuperación de la Función , Estudios Retrospectivos , Resultado del Tratamiento , Capacidad Vital
9.
Artículo en Inglés | MEDLINE | ID: mdl-24117088

RESUMEN

A comparative study was undertaken using indigenous sulfur-oxidizing microorganisms and iron-oxidizing microorganisms in separate 12 litre continuous stirred tank reactors (CSTRs) for solubilization of heavy metals from anaerobically digested sewage sludge. The CSTRs were operated at hydraulic retention times (HRTs) ranging from 4 to 10 days using sewage sludge feed having near neutral pH. The pH, oxidation-reduction potential (ORP) and solubilization efficiency of metals were found to be highly dependent on HRT and an increase in HRT led to higher solubilization of metals in both the CSTRs. In both the CSTRs, the CSTR operated with sulfur-oxidizing microorganisms at an HRT of 8 days was found to be optimum in solubilizing 58% Cu, 52% Ni, 72% Zn and 43% Cu from the sludge. The nutrient value, nitrogen and phosphorus of bioleached sludge was also conserved (<20% loss) at 8 days HRT. The metals fractionation study conducted using BCR sequential extraction procedure suggested that most of the metals remaining in the bioleached sludge were in the more stable fractions (F3 and F4) and, therefore, can be safely apply as a fertilizer on land.


Asunto(s)
Bacterias/metabolismo , Reactores Biológicos/microbiología , Hierro/metabolismo , Metales Pesados/metabolismo , Aguas del Alcantarillado/química , Aguas del Alcantarillado/microbiología , Azufre/metabolismo , Microbiología del Suelo
10.
Liver Int ; 31(9): 1352-8, 2011 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21745311

RESUMEN

BACKGROUND: Reports on the usefulness of serum markers for predicting liver necroinflammation are limited. The aim of this study was to determine the serum markers that predict significant inflammation in patients with chronic hepatitis B (CHB) and C (CHC) and normal or mildly elevated serum aminotransferase levels. METHODS: Two hundred twenty-seven patients with CHB or CHC with normal or mildly elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels (≤60 IU/L) were enrolled in this study. Significant inflammation was defined as inflammatory grade ≥3 activities using the Batt-Ludwig scoring system. The correlation between liver histology and serum markers of liver inflammation was analysed. RESULTS: Forty-eight (21.1%) and eight patients (3.5%) had grade 3 and 4 inflammation respectively. Univariate analysis revealed that age, platelet coun, and AST, ALT, γ-glutamyl transpeptidase, alkaline phosphatase, hyaluronic acid, haptoglobin, apolipoprotein A1 and procollagen III N-terminal peptide levels were significantly different between the patients with and without significant inflammation. There were no significant differences in the cytokeratin-18 fragment levels between the two groups. On the basis of multivariate analysis, the AST and apolipoprotein A1 levels and stage of fibrosis were highly predictive of significant inflammation. Using AST and apolipoprotein cut-off values ≥44 IU/L and ≤100 ng/ml, respectively, the presence of significant inflammation was predicted with high specificity (96.5%) and with a negative predictive value of 76.3%. CONCLUSION: The AST and apolipoprotein A1 levels were shown to be independent predictors of significant inflammatory activities in patients with CHB and CHC and normal or mildly elevated aminotransferase levels.


Asunto(s)
Alanina Transaminasa/sangre , Aspartato Aminotransferasas/sangre , Pruebas Enzimáticas Clínicas , Hepatitis B Crónica/diagnóstico , Hepatitis C Crónica/diagnóstico , Mediadores de Inflamación/sangre , Hígado/enzimología , Adolescente , Adulto , Anciano , Apolipoproteína A-I/sangre , Biomarcadores/sangre , Biopsia , Distribución de Chi-Cuadrado , Femenino , Hepatitis B Crónica/sangre , Hepatitis B Crónica/inmunología , Hepatitis B Crónica/patología , Hepatitis C Crónica/sangre , Hepatitis C Crónica/inmunología , Hepatitis C Crónica/patología , Humanos , Hígado/inmunología , Hígado/patología , Modelos Logísticos , Masculino , Persona de Mediana Edad , Necrosis , Valor Predictivo de las Pruebas , Estudios Prospectivos , República de Corea , Medición de Riesgo , Factores de Riesgo , Índice de Severidad de la Enfermedad , Regulación hacia Arriba , Adulto Joven
11.
Artículo en Inglés | MEDLINE | ID: mdl-20390893

RESUMEN

Bioleaching studies of spent petroleum catalyst containing Ni, V and Mo were carried out using iron oxidizing bacteria. Various leaching parameters such as Fe(II) concentration, pulp density, pH, temperature and particle size were studied to evaluate their effects on the leaching efficiency as well as the kinetics of dissolution. The percentage of leaching of Ni and V were higher than Mo. The leaching process followed a diffusion controlled model and the product layer was observed to be impervious due to formation of ammonium jarosite (NH(4))Fe(3)(SO(4))(2)(OH)(6). Apart from this, the lower leaching efficiency of Mo was due to a hydrophobic coating of elemental sulfur over Mo matrix in the spent catalyst. The diffusivities of the attacking species for Ni, V and Mo were also calculated.


Asunto(s)
Bacterias/metabolismo , Hierro/metabolismo , Molibdeno/metabolismo , Níquel/metabolismo , Petróleo/metabolismo , Vanadio/metabolismo , Catálisis , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Solubilidad , Temperatura
12.
J Hazard Mater ; 175(1-3): 267-73, 2010 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-19879686

RESUMEN

Bioleaching studies were conducted to evaluate the recovery of metal values from waste petroleum catalyst using two different acidophilic microorganisms, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Various leaching parameters such as contact time, pH, oxidant concentration, pulp densities, particle size, and temperature were studied in detail. Activation energy was evaluated from Arrhenius equation and values for Ni, V and Mo were calculated in case of both the acidophiles. In both cases, the dissolution kinetics of Mo was lower than those of V and Ni. The lower dissolution kinetics may have been due to the formation of a sulfur product layer, refractoriness of MoS(2) or both. Multivariate statistical data were presented to interpret the leaching data in the present case. The significance of the leaching parameters was derived through principle component analysis and multi linear regression analyses for both iron and sulfur oxidizing bacteria.


Asunto(s)
Petróleo/análisis , Purificación del Agua/métodos , Acidithiobacillus/metabolismo , Catálisis , Concentración de Iones de Hidrógeno , Hierro/química , Cinética , Modelos Lineales , Metales/química , Molibdeno/química , Análisis Multivariante , Níquel/química , Oxidantes/química , Análisis de Componente Principal , Vanadio/química
13.
J Hazard Mater ; 167(1-3): 1231-6, 2009 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-19286311

RESUMEN

Bioleaching studies of spent petroleum catalyst were carried out using sulfur oxidizing, Acidithiobacillus species. Leaching studies were carried out in two-stage, in the first stage bacteria were grown and culture filtrate was used in the second stage for leaching purpose. XRD analysis of spent petroleum catalyst showed oxides of V, Fe and Al and sulfides of Mo and Ni. The leaching kinetics followed dual rate, initial faster followed by slower rate and equilibrium could be achieved within 7 days. The leaching rate of Ni and V were high compared to Mo. The low Mo leaching rate may be either due to formation of impervious sulfur layer or refractoriness of sulfides or both. The leaching kinetics followed 1st order rate. Using leaching kinetics, rate equations for dissolution process for different metal ions were evaluated. The rate determining step observed to be pore diffusion controlled.


Asunto(s)
Acidithiobacillus/metabolismo , Biodegradación Ambiental , Petróleo , Azufre/metabolismo , Catálisis , Cinética , Metales Pesados , Contaminantes Químicos del Agua/metabolismo
14.
Artículo en Inglés | MEDLINE | ID: mdl-20183517

RESUMEN

A novel process was developed using sulfur-oxidizing bacteria to extract metal values like Ni, V and Mo from spent petroleum catalyst. Bacteria were grown in elemental sulfur media for five day and after filtering, the filtrate was used for leaching purpose. Effect of different parameters such as contact time, particle size, pulp density and lixiviant composition were studied to find out the extent of metal leaching during the leaching process. XRD analysis proved the existence of V in oxide form, Ni in sulfide form, Mo both in oxide as well as sulfide forms, and sulfur in elemental state only. In all the cases studied Ni and V showed higher leaching efficiency compared to Mo. The low Mo leaching rate may be either due to formation of impervious sulfur layer or refractoriness of sulfides or both. Leaching kinetics followed dual rate, initial faster followed by slower. Dissolution mechanism was explained on the basis of both surface and pore diffusion rate. The leaching kinetics followed 1st order reaction rate. Finally, multiple linear regression analysis was carried out to compare the observed and calculated leaching percentage values for three metals.


Asunto(s)
Acidithiobacillus thiooxidans/metabolismo , Contaminación Ambiental/prevención & control , Metales Pesados/aislamiento & purificación , Petróleo/análisis , Residuos/análisis , Industria Química , Cinética , Corea (Geográfico) , Modelos Lineales , Metales Pesados/química , Oxidación-Reducción , Azufre/metabolismo , Difracción de Rayos X
15.
J Hazard Mater ; 152(3): 1082-91, 2008 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-17825485

RESUMEN

Bioleaching of metals from hazardous spent hydro-processing catalysts was attempted in the second stage after growing the bacteria with sulfur in the first stage. The first stage involved transformation of elemental sulfur particles to sulfuric acid through an oxidation process by acidophilic bacteria. In the second stage, the acidic medium was utilized for the leaching process. Nickel, vanadium and molybdenum contained within spent catalyst were leached from the solid materials to liquid medium by the action of sulfuric acid that was produced by acidophilic leaching bacteria. Experiments were conducted varying the reaction time, amount of spent catalysts, amount of elemental sulfur and temperature. At 50 g/L spent catalyst concentration and 20 g/L elemental sulfur, 88.3% Ni, 46.3% Mo, and 94.8% V were recovered after 7 days. Chemical leaching with commercial sulfuric acid of the similar amount that produced by bacteria was compared. Thermodynamic parameters were calculated and the nature of reaction was found to be exothermic. Leaching kinetics of the metals was represented by different reaction kinetic equations, however, only diffusion controlled model showed the best correlation here. During the whole process Mo showed low dissolution because of substantiate precipitation with leach residues as MoO3. Bioleach residues were characterized by EDX and XRD.


Asunto(s)
Acidithiobacillus thiooxidans/metabolismo , Catálisis , Cinética , Temperatura , Termodinámica , Difracción de Rayos X
16.
Int J Dev Neurosci ; 25(6): 409-14, 2007 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-17964752

RESUMEN

Previous studies have shown that maturation of the white matter in terms of its relative signal intensity changes on MRI is almost complete at 2-3 years of age. We hypothesized that quantitative analysis may show maturation of the white matter during childhood and adolescence. In the present study we performed multi-echo T2 relaxometry in 33 healthy subjects (girls, 15; boys, 18) aged 3-15 years. T2 relaxation times of the genu and splenium were measured. In healthy subjects, the T2 relaxation times were significantly correlated with age in both girls (r=0.611, p=.016) and boys (r=0.721, p=.001) in the splenium, but not in the genu (p>.05). To further confirm genu-to-splenium signal intensity ratio changes, a total of 389 brain MRIs were retrospectively selected from the patients who had normal results (189 girls/women, 200 boys/men; age range, 3-20 years). The genu-to-splenium signal intensity ratio was obtained from the T2-weighted images. In patients with normal MRI, the genu-to-splenium signal intensity ratio was significantly decreased with age (p<.001) by 16 years. The T2 relaxation times gradually increase in the splenium during childhood and adolescence, suggestive of maturation.


Asunto(s)
Envejecimiento/fisiología , Corteza Cerebral/crecimiento & desarrollo , Cuerpo Calloso/crecimiento & desarrollo , Imagen por Resonancia Magnética/métodos , Adolescente , Adulto , Antropometría/métodos , Corteza Cerebral/anatomía & histología , Niño , Preescolar , Cuerpo Calloso/anatomía & histología , Femenino , Humanos , Masculino , Fibras Nerviosas Mielínicas/fisiología , Vías Nerviosas/anatomía & histología , Vías Nerviosas/crecimiento & desarrollo , Estudios Retrospectivos , Caracteres Sexuales
17.
J Comput Chem ; 28(3): 625-31, 2007 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-17195161

RESUMEN

In this study, we examined the gas-phase pyrolysis of ethyl N,N-dimethylcarbamate theoretically at various theoretical levels. The reaction consists of a two-step mechanism, with N,N-dimethylcarbamic acid and ethylene as reaction intermediates. In the first step, the reaction proceeds via a six-membered cyclic transition state (TS), which is more favorable than that via a four-membered cyclic TS. Here, the contribution of entropy to the overall potential energy surface was found to play an important role in determining the rate-limiting step, which was found to be the second step when viewed in terms of the enthalpy of activation (DeltaH(not equal)), but the first step when entropy changes (-TDeltaS(not equal)) were considered. These results are consistent with experimental findings. Moreover, the experimental activation entropy can be reproduced by using the hindered rotor approximation, which converts some low vibration frequencies that correspond to internal rotational modes into hindered rotors.


Asunto(s)
Entropía , Termodinámica
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