Differing field methods and site conditions lead to varying bias in suspended sediment concentrations in the Lower Mississippi and Atchafalaya Rivers

At sites that have been sampled for decades, changes in field and laboratory methods happen over time as instrumentation and protocols improve. Here, we compare the influence of depth- and point-integrated sampling on total, fine (< 0.0625 mm), and coarse (≥ 0.0625 mm) suspended sediment (SS) concentrations in the Lower Mississippi and Atchafalaya Rivers. Using historical field method information, we identified seven sites to test such differences. We found SS samples collected using point-integration tended to have higher concentrations than those collected using depth-integration. However, the presence and magnitude of the bias were inconsistent across sites. Bias was present at the site with less-than-ideal conditions (i.e., non-trapezoidal channel, non-uniform flow) and non-existent at the ideal site location, indicating the bias between sampling methods depends on site sampling conditions. When present, the bias is greater at higher concentrations and at moderate to high flows. At the less-than-ideal site, point-integrated samples can have 16% (total) and 34% (coarse) higher concentrations than depth-integrated samples. When flow effects are removed, this translates to a bias of 19, 9, and 8 mg per liter for total, fine, and coarse SS. When a change in field methods occurs, comparison samples and a rigorous evaluation of those samples are warranted to determine the proper course of action for a particular site. Often, the effect and solution will not be known until several years of comparison samples have been collected under a variety of hydrologic conditions.

Development and validation of a case ascertainment tool for ankylosing spondylitis

OBJECTIVE

Ankylosing spondylitis (AS) diagnosis is often delayed. The availability of effective biologic agents for treating AS has increased the importance of early diagnosis. We tested questions derived from a comprehensive literature review and an advisory board in a case-control study designed to identify patients with AS from among patients with chronic back pain (CBP).

METHODS

Question items were cognitively tested among patients with AS, and then in case-control studies for validation and creation of a scoring algorithm and question item reduction. AS cases were recruited from a known database, and CBP subjects (controls) were recruited from clinics, employers, and from the SpineUniverse Web site. We used individual question items in a multivariate framework to discriminate between people with and without AS.

RESULTS

Forty-three questions yielded 24 items for analyses; 12 of these were entered into a multivariate regression model. Individual items yielded odds ratios ranging from 0.07 to 30.31. Question items with a significant positive relationship to AS included male sex, neck or hip pain/stiffness, longer pain duration, decreased pain/stiffness with daily physical activity, pain relief within 48 hours of nonsteroidal antiinflammatory drugs, and diagnosis of iritis. The tool demonstrated a sensitivity of 67.4 and a specificity of 94.6. The tool was developed from clinically and radiologically diagnosed AS cases and therefore is designed to distinguish AS cases among CBP subjects. In addition, approximately 54% of the AS cases in the study were treated with biologic agents, which may impact questionnaire responses.

CONCLUSION

This tool can identify undiagnosed patients with AS and, potentially, those at an earlier stage in their disease course.

Quality measures in applications of image restoration

We describe a new method for the estimation of image quality in image restoration applications. We demonstrate this technique on a simulated data set of fluorescent beads, in comparison with restoration by three different deconvolution methods. Both the number of iterations and a regularisation factor are varied to enforce changes in the resulting image quality. First, the data sets are directly compared by an accuracy measure. These values serve to validate the image quality descriptor, which is developed on the basis of optical information theory. This most general measure takes into account the spectral energies and the noise, weighted in a logarithmic fashion. It is demonstrated that this method is particularly helpful as a user-oriented method to control the output of iterative image restorations and to eliminate the guesswork in choosing a suitable number of iterations.

Carcinoma of the extrahepatic bile duct

We present a case of a 70-year old American Indian who had a previous cholecystectomy for symptomatic cholelithiasis and who presented, one year later, with progressive painless jaundice and a dilated common bile duct. Work-up revealed an adenocarcinoma of the extrahepatic bile duct. In this article we discuss the common presentation, work-up, and treatment of carcinoma of the bile ducts.

Tuberculous peritonitis: a case report and literature review

We present a case of tuberculous peritonitis in the setting of alcoholic cirrhosis with ascites. A young American Indian male with alcoholic cirrhosis and ascites presented with low grade fever and weight loss. A diagnosis of tuberculous peritonitis was made by laparoscopic guided peritoneal biopsy. He was treated successfully with isoniazid and ethambutol for 24 months. The diagnosis of tuberculous peritonitis should be entertained in high risk populations such as American Indians, Asians, alcoholics, chronic ambulatory peritoneal dialysis patients and AIDS patients in the appropriate clinical setting. Definitive diagnosis can usually be made by laparoscopic guided peritoneal biopsy.

Two-photon excited LIF determination of H-atom concentrations near a heated filament in a low pressure H(2)environment

With respect to the investigation of low pressure filament-assisted chemical vapor deposition processes for diamond formation, absolute concentrations of atomic hydrogen were determined by two-photon laserinduced fluorescence in the vicinity of a heated filament in an environment containing H(2) or mixtures of H(2)and CH(4). Radial H concentration profiles were obtained for different pressures and filament temperatures, diameters, and materials. The influence of the addition of various amounts of methane on the H atom concentrations was examined.

Comparison of oxygen consumption, carbon dioxide production, and resting energy expenditure in premature and full-term infants

A newly developed closed circuit water-sealed infant calorimeter has been used to measure oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and resting energy expenditure (REE) in 31 infants. There were 17 full-term and 14 premature infants. VO2 was measured volumetrically, keeping the inspired oxygen concentration constant. VCO2 was determined by infrared analysis of the mixed expired gases. Values for REE and RQ were calculated from measurements of VO2 and VCO2. All values were normalized for the infants body weight. Our findings demonstrate significant differences in VO2, VCO2, and REE associated with weight, gestational age, postnatal age, activity, feeding, and sex. In addition, VO2, VCO2, and REE were significantly higher for the premature infants. The water-sealed indirect calorimetry system: (a) is safe and noninvasive, (b) does not interfere with infant tube feeding or IV infusion, (c) permits long-term monitoring of metabolic activity, and (d) allows a more exact matching of oral and intravenous feedings to actual energy expenditure. We are finding that indirect calorimetry removes the guess work from writing daily caloric regimens, with potential advantage for the treatment of sick infants.