Supercritical water gasification of Eucalyptus grandis and related pyrolysis char: Effect of feedstock composition.

Eucalyptus grandis (E. grandis) wood and char products derived from pyrolysis of E. grandis wood, were gasified in supercritical water at 450°C - with and without the use of a homogeneous (K2CO3) and heterogeneous (Ni/Al2O3-SiO2) catalyst. Gas yields and gasification efficiencies were measured experimentally and compared to calculated thermodynamic equilibrium values, specifically considering the effects of the O/C ratio and volatile matter content of the feed material. Thermodynamically, feed material with lower O/C ratios (0.22) typically resulted in higher CH4 yields (30mol/kgfeed,dry) and gasification efficiencies (188%). However, experimentally, feed material with lower O/C ratios and lower volatile matter resulted in the lowest CH4 yields and gasification efficiencies. Furthermore, a linear relationship between the carbon efficiency (CE) and both the volatile matter content and O/C ratio of the feed material was found to hold true in both catalytic and non-catalytic experiments.

Catalytic supercritical water gasification of primary paper sludge using a homogeneous and heterogeneous catalyst: Experimental vs thermodynamic equilibrium results.

H2, CH4, CO and CO2 yields were measured during supercritical water gasification (SCWG) of primary paper waste sludge (PWS) at 450°C. Comparing these yields with calculated thermodynamic equilibrium values offer an improved understanding of conditions required to produce near-equilibrium yields. Experiments were conducted at different catalyst loads (0-1g/gPWS) and different reaction times (15-120min) in a batch reactor, using either K2CO3 or Ni/Al2O3-SiO2 as catalyst. K2CO3 up to 1g/gPWS increased the H2 yield significantly to 7.5mol/kgPWS. However, these yields and composition were far from equilibrium values, with carbon efficiency (CE) and energy recovery (ER) of only 29% and 20%, respectively. Addition of 0.5-1g/gPWS Ni/Al2O3-SiO2 resulted in high H2 and CH4 yields (6.8 and 14.8mol/kgPWS), CE of 84-90%, ER of 83% and a gas composition relatively close to the equilibrium values (at hold times of 60-120min).

Thermodynamic modelling of supercritical water gasification: investigating the effect of biomass composition to aid in the selection of appropriate feedstock material.

A process model developed in Aspen Plus®, was used for the thermodynamic modelling of supercritical water gasification (SCWG) using a wide variety of biomass materials as feedstock. The influence of the composition of the biomass material (in terms of carbon, hydrogen and oxygen content) on various performance indicators (such as gas yields, cold gas efficiency, calorific value of product gas and heat of reaction), were determined at various temperatures (600, 700 and 800°C) and biomass feed concentrations (5, 15 and 25wt.%). Generalised contour plots, based on the biomass composition, were developed for these performance indicators to provide the thermodynamic limits at various operating conditions. These plots can aid in the selection or screening of potential biomass materials and appropriate operating conditions for SCWG prior to conducting experimental work.

Prevalence of HIV among women entering labor who accepted or declined voluntary counseling and testing.

OBJECTIVE: To assess whether there was a difference in HIV seroprevalence between eligible women who declined and those who agreed to participate in a study of voluntary counseling and testing among women entering labor with unknown HIV status in South Africa. METHODS: Anonymous cord blood specimens were collected-as dried blood spots-from all women approached for participation in a cluster-randomized trial. No patient identifiers were included on the cord blood specimens. The dried blood spots were analyzed for HIV antibody via enzyme immunoassay and western blotting. RESULTS: Of 7238 women screened for study participation, 1041 (14.4%) had undocumented HIV status; of these women, 542 were eligible for inclusion and 343 enrolled. Based on 513 evaluable samples, the overall seroprevalence was 13.3% (95% confidence interval [CI], 10.4-16.5), which was similar to the 13.1% (95% CI, 9.7-17.2) seroprevalence among the 343 enrolled women. CONCLUSION: Seroprevalence among eligible women was similar to that among enrolled women, which indicates that study participation did not select for a group with an HIV seroprevalence substantially different from that among women who declined to enroll.

A randomized trial of catheters of different lengths to achieve right atrium versus superior vena cava placement for continuous renal replacement therapy.

BACKGROUND: The aim was to assess whether inserting a longer soft silicone short-term dialysis catheter targeting tip placement in the right atrium could improve dialyzer circuit life span compared with inserting a shorter dialysis catheter targeting tip placement in the superior vena cava. STUDY DESIGN: Randomized unblinded controlled study. SETTING & PARTICIPANTS: A tertiary multidisciplinary intensive care unit enrolling 100 critically ill patients requiring continuous renal replacement therapy (CRRT). INTERVENTION: Placement of longer (20-24 cm) versus shorter dialysis catheters (15-20 cm) within one of the major thoracic veins for initiation of CRRT. OUTCOMES: The primary study outcome was duration of dialysis circuit life span. Secondary outcomes included delivered daily dialysis dose, incidence and cause of CRRT circuit failure, complications potentially related to the position of the short-term dialysis catheter, mortality, and patient length of stay. RESULTS: Placing the longer dialysis catheters was associated with an increased average dialyzer life span of 6.5 hours (24 hours [25th-75th percentile, 11-32] vs 17.5 hours [25th-75th percentile, 8-23]; P = 0.001), improved delivered daily dialysis dose (91% [25th-75th percentile, 85%-100%] vs 81% [25th-75th percentile, 72%-97%]; P < 0.001), and reduced number of dialyzers clotted (2.3 vs 3.6; P = 0.04) or circuits taken down due to vascular access problem (0.19 vs 0.53; P = 0.04) per patient compared with placing shorter dialysis catheters. The incidence of atrial arrhythmias was similar between groups (28% vs 21%; P = 0.6) and the only mechanical complication was the malposition of one dialysis catheter tip in the longer dialysis catheter group. LIMITATIONS: Single-center study design. CONCLUSIONS: The use of longer soft silicone short-term dialysis catheters targeting right atrial placement appeared to be safe and could improve dialyzer life span and daily dialysis dose of CRRT delivered compared with the use of shorter catheters targeting superior vena cava placement.

Adult bronchopulmonary dysplasia: computed tomography pulmonary findings.

INTRODUCTION: This study aimed to describe the structural pulmonary sequelae of bronchopulmonary dysplasia (BPD) in adulthood. SUBJECTS AND METHODS: Fifty-one adult survivors (36 females and 15 males; median age 20 years) of BPD underwent high-resolution inspiratory and expiratory computed tomography of the chest. The scans were evaluated independently by two thoracic radiologists blinded to the patient's clinical details using a standardised scoring system. RESULTS: Abnormal findings were seen in 50 (98%), the most common of which were subpleural triangular opacities (94%), linear opacities (90%), air trapping (65%) and emphysema (47%). The kappa values were derived by simplifying the score for each finding as present or absent. The kappa values for these findings were 0.65, 0.20, 0.58 and 0.54, respectively. CONCLUSIONS: Common findings were triangular, linear opacities and gas trapping. Emphysema diagnosis was more prevalent than previous studies, which may have been enhanced by improved technical factors.

Rapid intrapartum or postpartum HIV testing at a midwife obstetric unit and a district hospital in South Africa.

OBJECTIVE: To compare the prepartum and postpartum feasibility and acceptance of voluntary counseling and rapid testing (VCT) among women with unknown HIV status in South Africa. METHODS: Eligible women were randomized according to the calendar week of presentation to receive VCT either while in labor or after delivery. RESULTS: Of 7238 women approached, 542 (7.5%) were eligible, 343 (63%) were enrolled, and 45 (13%) were found to be HIV infected. The proportions of eligible women who accepted VCT were 66.8% (161 of 241) in the intrapartum arm and 60.5% (182 of 301) in the postpartum arm, and the difference of 6.3% (95% CI, -1.8% to 14.5%) was not significant. The median times (44 and 45 minutes) required to conduct VCT were also similar in the 2 arms. In the intrapartum arm, all women in true labor received their test results before delivery and all those found to be HIV positive accepted prophylaxis with nevirapine before delivery. CONCLUSIONS: Rapid testing in labor wards for women with an unknown HIV status is feasible and well accepted, and allows for a more timely antiretroviral prophylaxis than postpartum testing.