Effect of bubble-induced surface turbulence on gas-liquid mass transfer in diffused aeration systems.

Models that predict volatilization of organic compounds from wastewater treatment basins may underestimate emission rates if the surfaces are considered as quiescent. In reality, the water surface may be agitated by subsurface aeration, increasing mass transfer across the tank surface air-water interface. This study investigated the effect of turbulence, induced by diffused bubble aeration, on mass transfer at the water surface of a pilot aeration basin. The mass transfer of ammonia from an enclosed headspace over the basin to acidified water was measured when different diffuser types and airflow rates were applied. Oxygen-transfer tests were conducted immediately following each ammonia-transfer test. Increasing airflow rates through fine- and coarse-bubble diffusers had a significant effect on the ammonia mass-transfer rate. Experimental mass-transfer parameters (K(L)a's) for surface volatilization derived with aeration present were up to 48% higher than the K(L)a values for quiescent conditions over the range of conditions tested. No effect of diffuser type on ammonia transfer could be determined. The study results infer an effect on oxygen transfer into the water at the surface and potential transfer of volatile organic compounds, if present, from the water. The results of the ammonia mass-transfer experiments suggest that adjustments to the existing mass transfer correlations for surface volatilization from aeration basins may be in order. Such adjustments will have the greatest effect on predictions for the less volatile compounds, under conditions of low airflow rates.

Neuropsychological predictors of the attainment of treatment objectives in substance abuse patients.

This study examined the contribution of neuropsychological functioning to the attainment of treatment objectives in substance abuse patients. Subjects were 85 patients enrolled in comprehensive, inpatient and outpatient substance abuse treatment at a VA Medical Center. Most subjects were diagnosed with Alcohol Dependence or Abuse, and nearly half were seeking treatment for Cocaine Dependence or Abuse. After acute detoxification, but before beginning individualized treatment, subjects were administered a neuropsychological screening battery to assess cognitive functioning and affective status. They then attended a variety of daily group therapies. Each therapy group had its own set of specific treatment objectives; on each treatment day, group therapists rated each patient's attainment of the specific objectives for their group. Groups included Assertiveness Training (Levels I and II), Stress Management (Levels I and II), Social Skills Training, Job Skills, Relapse Prevention (Levels I and II), Leisure Planning, Leisure Skills, Occupational Therapy, and 12-Step Study. Stepwise multiple regression indicated that the best predictors of overall objective attainment were better attention (WMS-R Digits Backwards) and less depressive symptomatology (Beck Depression Inventory). These results suggest that attention and mood have a modest yet significant impact on the success of treatment interventions for substance abuse patients. Thus, evaluation of cognitive as well as affective factors in substance abuse patients might be helpful in designing and implementing specialized interventions to maximize the likelihood of treatment success.

Accuracy of CT angiography versus pulmonary angiography in the diagnosis of acute pulmonary embolism: evaluation of the literature with summary ROC curve analysis.

RATIONALE AND OBJECTIVES: The authors performed this study to estimate, by using published data, the sensitivity and specificity of computed tomographic (CT) angiography in the evaluation of suspected acute pulmonary embolism (PE). MATERIALS AND METHODS: Summary receiver operating characteristic (ROC) curve analysis was used to determine the sensitivity and specificity of CT angiography in the diagnosis of acute PE. Pulmonary angiography was used as the diagnostic standard of reference. The authors reviewed the results of 11 independent studies published in the English-language literature between January 1992 and June 1999. RESULTS: The sensitivity of CT angiography in the diagnosis or exclusion of PE in the central pulmonary arteries (to the level of the segmental pulmonary arteries) ranged from 0.74 to 0.81 on the basis of specificities of 0.89-0.91. The sensitivity of CT angiography in the diagnosis or exclusion of PE in all pulmonary arteries (to the level of the subsegmental pulmonary arteries) was 0.68 on the basis of a specificity of 0.91. CONCLUSION: On the basis of the studies in the current literature, most of which used 5.0-mm collimation and single-detector CT, CT angiography may be less accurate in the diagnosis of PE than previously reported. With improvements in data acquisition, particularly the use of thinner section collimation and multidetector CT, and in the increased use of workstations for data analysis, the accuracy and utility of CT angiography will require continued investigation.

Acute biliary disease: initial CT and follow-up US versus initial US and follow-up CT.

PURPOSE: To evaluate the utility of ultrasonography (US) versus that of computed tomography (CT) for assessment of acute biliary disease. MATERIALS AND METHODS: Radiologic reports and clinical charts were reviewed in all patients who underwent US and CT within 48 hours of each other for evaluation of acute right upper quadrant pain. Radiologic findings and clinical outcome were correlated. RESULTS: CT was the initial imaging study in 57 patients, and CT findings resulted in underdiagnosis or misdiagnosis of acute biliary disease in eight of 11 patients. Follow-up US results were suggestive of the correct diagnosis and provided additional clinical information in seven of these eight patients. US findings resulted in altered clinical treatment in six of 11 patients with acute biliary disease. US was the initial study in 66 patients, and US findings were suggestive of biliary disease or the correct diagnosis in seven of seven patients with acute biliary disease. Follow-up CT did not result in changes in clinical treatment in any patient with acute biliary disease. CONCLUSION: Initial US is better than initial CT in patients suspected of having acute biliary disease. Follow-up CT provides no additional information regarding the biliary system, and its use should be limited to those patients with a wider differential diagnosis or with confusing clinical symptoms and signs.

Hypertrophied antral-pyloric fold: reassessment of radiographic findings in 40 patients.

PURPOSE: To reassess the findings of a hypertrophied antral-pyloric fold on double-contrast barium studies. MATERIALS AND METHODS: A search of radiologic files resulted in recovery of records of 1,796 patients with findings of antral gastritis on double-contrast upper gastrointestinal studies. According to radiologic reports, 40 patients had a hypertrophied antral-pyloric fold. The radiographs were reviewed retrospectively to determine the size, location, and morphologic features of the folds. Clinical, radiologic, and/or endoscopic follow-up data were obtained in 22 patients. RESULTS: All but two patients were symptomatic, and all but one responded to medical treatment. The hypertrophied antral-pyloric fold was located on the lesser curvature of the distal antrum in all patients and extended to the pylorus in 25 (62%) and into the base of the duodenal bulb in 15 (38%). The fold appeared as a smooth or slightly lobulated submucosal mass in 37 (92%) patients and as a plaquelike lesion in three (8%). Other radiographic findings of antral gastritis were present in 26 (65%) patients. In nine patients who underwent endoscopy, endoscopic and/or histologic findings of antral gastritis were present in five, but none had evidence of tumor. CONCLUSION: A hypertrophied antral-pyloric fold may be a sign of antral gastritis that is associated with characteristic radiographic findings. Endoscopy and biopsy may not be warranted when lesions with features typical of a hypertrophied antral-pyloric fold are seen on double-contrast barium studies.

The hypertrophied antral-pyloric fold: CT appearance.

We report a patient found to have a hypertrophied antral-pyloric fold on barium study, in whom CT demonstrated a smooth soft tissue mass on the anterior wall of the pre-pyloric antrum. When this finding is encountered on CT, a double-contrast upper GI study should be performed as the next diagnostic test. Endoscopy can probably be avoided if the barium study shows the typical findings of a hypertrophied antral-pyloric fold.

Self-report and objective measures of cognitive deficit in patients entering substance abuse treatment.

The relationship between self-reported cognitive deficits and objectively measured cognitive performance was examined in 86 patients entering substance abuse treatment. Self-ratings of cognitive impairment were strongly correlated with indices of depression and vulnerability to stress, but not with objective cognitive performance. Confirming the lack of relationship between self-report and objective cognitive measures, cognitive performance did not differ between patients at the extremes of the cognitive-complaint distribution; and cognitively impaired patients did not differ from cognitively intact patients in their self-ratings of impairment.

Impact of screening MR angiography on referrals for percutaneous intervention in renovascular disease.

PURPOSE: Concern about contrast- and catheter-induced complications inhibits liberal use of catheter angiography to screen for renal artery stenosis. The authors evaluated the impact on interventional practice growth of offering magnetic resonance angiography (MRA) as an alternative screening test for renovascular disease. MATERIALS AND METHODS: A retrospective analysis of 339 patients with renovascular disease identified with MRA from January 1, 1993 through December 31, 1997, and the subsequent utilization of follow-up catheter angiography and/or intervention was performed. The number of patients treated per year with percutaneous techniques for renovascular disease was recorded, and was correlated with screening MRA. The impact of screening MRA on percutaneous management of renovascular disease was evaluated through comparisons of the number of percutaneous procedures performed among the individual years during the 5-year period, and with the number of procedures performed during the 5-year period (1988-1992) immediately preceding 1993, prior to the use of screening MRA. RESULTS: The number of annual screening MRA examinations increased six-fold during the 5-year period, from 17 per year initially to approximately 100 per year for each of the last 3 years. One hundred thirty-five (40%) of screening MRA examinations were positive for renal artery stenosis or occlusion, and 111 (33%) patients had anatomy potentially suitable for percutaneous intervention. Fifty-two patients with positive screening MR angiograms underwent arteriography: 34 underwent renal angioplasty or stent placement, seven had surgery, seven with stenosis determined with MRA had occlusion on catheter angiography, and four had false-positive results of MRA (<50% stenosis). Three additional patients with negative screening MR angiograms were also referred for arteriography, which confirmed the MRA findings. The percentage of positive catheter angiograms was 50% greater among patients with a screening MRA, and the number of renal artery angioplasties performed annually doubled. Moreover, comparison with the 5-year period from 1988 to 1992 (immediately prior to the use of MRA as a screening tool), demonstrates that the average number of renal artery percutaneous procedures performed per year increased nearly 350% from an average of three per year to 15 per year. These findings are entirely attributable to referrals from screening MRA. CONCLUSIONS: Marketing of renal artery MRA as a safe, noninvasive outpatient screening technique can lead to improved utilization of catheter angiography in evaluation of renovascular disease, and can secondarily increase the volume of renal artery angioplasty and stent placement procedures for treatment of renovascular disease.