A method for sampling and electrophoretic analysis of aqueous plugs segmented in a stream of immiscible oil is described. In the method, an aqueous buffer and oil stream flow parallel to each other ...to form a stable virtual wall in a microfabricated K-shaped fluidic element. As aqueous sample plugs in the oil stream make contact with the virtual wall, coalescence occurs and sample is electrokinetically transferred to the aqueous stream. Using this virtual wall, two methods of injection for channel electrophoresis were developed. In the first, discrete sample zones flow past the inlet of an electrophoresis channel and a portion is injected by electroosmotic flow, termed the “discrete injector”. With this approach at least 800 plugs could be injected without interruption from a continuous segmented stream with 5.1% RSD in peak area. This method generated up to 1,050 theoretical plates, although analysis of the injector suggested that improvements may be possible. In a second method, aqueous plugs are sampled in a way that allows them to form a continuous stream that is directed to a microfluidic cross-style injector, termed the “desegmenting injector”. This method does not analyze each individual plug but instead allows periodic sampling of a high-frequency stream of plugs. Using this system at least 1000 injections could be performed sequentially with 5.8% RSD in peak area and 53,500 theoretical plates. This method was demonstrated to be useful for monitoring concentration changes from a sampling device with 10 s temporal resolution. Aqueous plugs in segmented flows have been applied to many different chemical manipulations including synthesis, assays, sampling processing and sampling. Nearly all such studies have used optical methods to analyze plug contents. This method offers a new way to analyze such samples and should enable new applications of segmented flow systems.
Conjugated linoleic acids (CLA) are conjugated isomers of linoleic acid, which may promote health with regard to cancer, heart disease, diabetes, bone formation, growth modulation and immunity. The ...c9,t11 isomer of CLA, rumenic acid (RA), is the major isomer present in the diet. However, dietary intakes of CLA and RA by humans have not been examined rigorously, nor has the relationship between dietary CLA or RA and health (e.g., body composition). Three-day dietary records (DR) were collected from adult men (n = 46) and women (n = 47) and analyzed using a nutrient database modified to contain total CLA and RA. Simultaneously, 3-d food duplicates (FD) were collected to determine analytically individual fatty acid intakes, including those of total CLA and RA. Chronic total CLA and RA intakes were estimated using a semiquantitative food-frequency questionnaire (FFQ). Body composition was estimated using body mass index and percentage of body fat. Total CLA intake was estimated from FD to be 212 ± 14 and 151 ± 14 mg/d (mean ± SEM) for men and women, respectively; RA intake was estimated to be 193 ± 13 and 140 ± 14 mg/d for men and women, respectively. In general, CLA and RA intakes estimated by DR and FFQ were significantly lower than those estimated by FD. Body composition was not significantly related to dietary total CLA or RA intake. In conclusion, results suggest that DR and FFQ methodologies are not reliable estimators of individual total CLA and RA intakes and may underestimate total CLA and RA intakes of groups. Intake of total CLA and RA was found to be significantly lower than that suggested previously by others.
Isomers of conjugated linoleic acid (CLA) decreased milk fat, altered immunity, and reduced the risk for cardiovascular disease (CVD) in some animals. The major form of CLA in the human diet is ...c9,t11-18:2 (rumenic acid; RA). We studied the effects of high RA consumption on plasma and milk RA concentration, milk composition, immunity, and CVD risk factors in lactating women (n = 36) assigned to 1 of 3 treatments: control, low CLA cheese (LCLA; 160 mg RA/d), or high CLA cheese (HCLA; 346 mg RA/d). The increase in plasma RA concentration between baseline and 8 wk in women consuming HCLA cheese was significantly greater than that of controls. At study completion (8 wk), milk RA concentration among women consuming HCLA cheese was greater (P < 0.05) than that of controls (0.37 vs. 0.26% of fatty acids). Treatment did not affect milk fat, protein, or lactose concentrations, immune indices (e.g., plasma T-helper cells and interleukin-2), or measured risk factors for CVD (e.g., plasma triacylglyceride and cholesterol). In summary, consumption of a RA-enriched cheese modestly increased plasma and milk RA concentrations without affecting total milk fat, plasma and milk indices of immunity, or selected risk factors for CVD.
Objective— To determine the sensitivity and specificity with which acetabular component angles of inclination and version could be used, alone or in combination, to predict luxation of cemented total ...hip arthroplasties (THA).
Study Design— Comparison of retrospectively selected cases and controls
Sample Population— All THA performed at the University of Florida between 1991 and 1998 with the BioMedtrix system and for which at least 2 months of radiographic follow‐up were available. All THA performed at the University of Georgia with the BioMedtrix system which subsequently luxated.
Methods— Acetabular component inclination angle (IA) and acetabular version angle (VA) were determined for each THA. Data were grouped according to outcome—luxation or no luxation— with the luxated cases from the 2 institutions pooled. Receiver operator characteristic (ROC) analysis was used to evaluate decision rules for using IA and VA as tests for detecting postoperative luxation. Sensitivity and specificity for luxation and 95% confidence bounds were computed with selected values of IA and VA as cut‐points.
Results— The nonluxation group consisted of 68 THA with a median follow‐up time of 5 months (range, 2–60 months). The luxation group consisted of 12 THA with a mean time to luxation of 36 days. The nonluxation group had a mean ± standard deviation (SD) IA and VA of 40.3°± 8.9° and 71.1°± 13.6°, respectively, whereas the luxation group had a mean ± SD IA and VA of 34.7°± 12.6° and 72.9°± 16.6°, respectively. An IA cut‐point of 37.8° achieved 58.3% sensitivity and 57.4% specificity. A VA cut‐point of 73° achieved 75.0% sensitivity and 51.5% specificity. IA and VA considered simultaneously achieved a 50.0% sensitivity and 88.2% specificity.
Conclusions and Clinical Relevance— ROC analysis indicated that both IA and VA considered individually or simultaneously were poor indicators of luxation. Although extreme values of IA may predict luxation with high specificity, the potential for luxation cannot be excluded based on apparently appropriate values of IA and VA. The results of this study also indicate that a successful outcome is possible with a wide range of acetabular component positions.
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