Contactless conductivity detector for microchip capillary electrophoresis

A microfabricated electrophoresis chip with an integrated contactless conductivity detection system is described. The new contactless conductivity microchip detector is based on placing two planar sensing aluminum film electrodes on the outer side of a poly(methyl methacrylate) (PMMA) microchip (without contacting the solution) and measuring the impedance of the solution in the separation channel. The contactless route obviates problems (e.g., fouling, unwanted reactions) associated with the electrode-solution contact, offers isolation of the detection system from high separation fields, does not compromise the separation efficiency, and greatly simplifies the detector fabrication. Relevant experimental variables, such as the frequency and amplitude of the applied ac voltage or the separation voltage, were examined and optimized. The detector performance was illustrated by the separation of potassium, sodium, barium, and lithium cations and the chloride, sulfate, fluoride, acetate, and phosphate anions. The response was linear (over the 20 microM-7 mM range) and reproducible (RSD = 3.4-4.9%; n = 10), with detection limits of 2.8 and 6.4 microM (for potassium and chloride, respectively). The advantages associated with the contactless conductivity detection, along with the low cost of the integrated PMMA chip/detection system, should enhance the power and scope of microfluidic analytical devices.     

Bounds for the Element Distinctness Problem on one-tape Turing machines

We disprove a conjecture of López-Ortiz by showing that the Element Distinctness Problem for n numbers of size O(logn) can be solved in O(n²(logn)^3/2(loglogn)^1/2) steps by a nondeterministic one-tape Turing machine. Further we give a simplified algorithm for solving the problem for shorter numbers in time O(n²logn) on a deterministic one-tape Turing machine and a new proof of the matching lower bound.     

Exact Isosurfaces for Marching Cubes

In this paper we study the exact contours of a piecewise trilinear scalar field. We show how to represent these contours exactly as trimmed surfaces of triangular rational cubic Bézier patches. As part of this, we introduce an extension of the marching cubes algorithm which gives a topologically exact triangular approximation of the contours for any case. Finally, we modify the exact contours to be globally  G¹  continuous without changing their topologies. We test the algorithm on both theoretical and practical data sets.     

Analysis of the electromagnetic forming process

As a result of the mathematical analysis of the electromagnetic forming process, an approximate solution and a more exact numerical solution of a set of differential equations are presented. Both methods permit the investigation of the influence of a variety of parameters of the discharge unit, the forming coil, and of the workpiece on the attainable forming result. Three conditions for an optimum design of the forming machine are derived from the approximate solution, one of them being an expression for the optimum frequency, for which maximum deformation is achieved. The numerical solution was verified by comparison with selected experimental results.     

Lactobacillus effects on cholesterol: in vitro and in vivo results

A double blind investigation was conducted on the influence of a commercially available tablet containing Lactobacillus acidophilus and Lactobacillus bulgaricus (Lactinex Becton Dickinson Microbiology Systems, Cockeysville, MD) on human serum lipoprotein concentrations. Tablets containing about 2 X 10(6) viable bacteria of Lactobacillus mixtures or placebo tablets were ingested by 354 nonfasting informed subjects in a dose of one tablet each, taken four times a day. There was a 3-wk washout period between two 6-wk treatment periods. The number of viable lactobacillus in unused returned tablets was the same at the end of the study as in the beginning. Analysis of paired data using Wilcoxon signed ranks test showed no major effects on lipoprotein concentrations for either the placebo-treated group or the lactobacilli-treated group. There were no statistically significant differences for low density lipoprotein concentrations between the lactobacilli-treated group and the placebo-treated group. The high density lipoprotein concentrations increased 1.8 to 3.0 mg/dl in both groups for both study periods. For total cholesterol the placebo-treated group experienced a statistically significant increase in the first period according to the Wilcoxon signed ranks test (from 208.0 to 215.0 mg/dl, P less than .001) but not according to a two-sample Student t test. Total cholesterol did not change significantly for the Lactobacillus-treated group in either period. Cardiac risk factor (ratio of total cholesterol to high density cholesterol) did not vary during the study. Lipoprotein values increased immediately following vigorous exercise compared with following 15 min of resting without either placebo or treatment. Sample controls for assay and reassay gave virtually identical values (coefficient of variation 1.6%), confirming that assay results were quite reliable. Thus, ingestion of commercially available Lactobacillus tablets, which contain about 2 X 10(6) cfu/tablet of L. acidophilus and L. bulgaricus cells in a dose of four tablets daily did not affect serum lipoprotein concentrations.     

Ectopic adrenocorticotropin (ACTH) and corticotropin-releasing hormone (CRH) production in the adrenal gland: basic and clinical aspects

The hypothalamic-pituitary-adrenal (HPA) axis is integrated in the human stress system and controls the metabolism of many cell systems in the body. Therefore, hypofunction or hyperfunction of the HPA axis potentially threatens the life of the whole organism. Noncontrolled overproduction of its key regulators, CRH and ACTH, causes dysfunction of the stress system. Ectopic secretion of these compounds may be part of extraadrenal paraneoplastic syndromes caused by various benign or malignant tumors. However, ectopic ACTH and CRH may originate from the adrenal itself. A local CRH/ACTH system exists in the normal human adrenal medulla. Overproduction of CRH and ACTH has been documented in pheochromocytomas causing Cushing's syndrome. Finally, ectopic production of ACTH causing Cushing's syndrome has also been demonstrated in adrenocortical cells. This suggests a marked plasticity within the HPA axis and the neuroendocrine cell system.     

Identification and characterization of location decision factors for relocating dairy farms

A survey was conducted to determine the importance of various location factors during the site selection process for relocating dairy farms. The objectives were to identify the importance of location decision factors (LDF) and characterize how importance differs among respondents with different demographic characteristics. Information was collected from sampled populations of Grade A milk producers in the top 35 milk-producing states in the United States and from U.S. agribusiness professionals using a mailed questionnaire. Location decision factors (n = 110) were rated on importance using a numerical scale of 0 to 10, where 0 = not important and 10 = critically important. Demographic data were collected from each respondent. Of 906 respondents, 72.4% identified their primary occupation as dairy producer. The five overall most important LDF were 1) availability of fresh water supplies (9.16 +/- 0.05); 2) availability of land for waste management (8.94 +/- 0.05); 3) average mailbox price of milk (8.79 +/- 0.05); 4) quality of fresh water supply (8.41 +/- 0.06); and 5) complexity of laws governing waste management (8.35 +/- 0.06). Factors pertaining to dairy production activities, such as cost of feeds and milk handling, were prevalent among those LDF in the upper quartile of importance. Region and herd size had significant effects on the overall importance of LDF. The relative importance of factors differed between western and eastern regions of the United States. Observed differences in importance of LDF among subclasses of respondents suggest that characteristics of the geographic regions evaluated and dairy production activities at various scales affect perceived importance of certain LDF.     

On the security of fair non-repudiation protocols

We analyzed two non-repudiation protocols and found some new attacks on the fairness and termination property of these protocols. Our attacks are enabled by several inherent design weaknesses, which also apply to other non-repudiation protocols. To prevent these attacks, we propose generic countermeasures that considerably strengthen the design and implementation of non-repudiation protocols. The application of these countermeasures is finally shown by our construction of a new fair non-repudiation protocol.