A Probabilistic Exclusion Principle for Tracking Multiple Objects

Tracking multiple targets is a challenging problem, especially when the targets are identical, in the sense that the same model is used to describe each target. In this case, simply instantiating several independent 1-body trackers is not an adequate solution, because the independent trackers tend to coalesce onto the best-fitting target. This paper presents an observation density for tracking which solves this problem by exhibiting a probabilistic exclusion principle. Exclusion arises naturally from a systematic derivation of the observation density, without relying on heuristics. Another important contribution of the paper is the presentation of partitioned sampling, a new sampling method for multiple object tracking. Partitioned sampling avoids the high computational load associated with fully coupled trackers, while retaining the desirable properties of coupling.     

Automated detection of anti-double-stranded DNA antibody in systemic lupus erythematosus serum by flow immunoassay

We describe a novel automated flow immunoassay system for quantification of anti-double-stranded (ds) DNA autoimmune antibodies in the serum of patients suffering from systemic lupus erythematosus. dsDNA (360 bp) was covalently coupled with alkaline phosphatase (ALP) to form a novel analytical reagent (ALP-DNA). After immunoreaction, antibody-antigen complexes between ALP-DNA and anti-dsDNA monoclonal antibody were separated from unreacted ALP-DNA by an ion-exchange column on the basis of the difference in isoelectric point. Antibody-antigen complexes were subsequently quantified by luminescence following addition of 3-(2'-spiroadamantane)-4-methoxy-4-(3"-phosphoryloxy)phenyl- 1,2-dioxetane. The assay yielded a linear relationship between signal and concentration of anti-dsDNA monoclonal antibody in the range of 0-300 micrograms/mL. This simple technique permits the assay of anti-dsDNA autoimmune antibodies within 25 min. The ion-exchange column was simply regenerated by occasional elution with eluent (20 mM N-methylpiperazine, pH 5.5) supplemented with 0.5 M NaCl, to remove unreacted ALP-DNA.     

Biochemical basis for a cholesterol-lowering activity of 2-[2"-(1",3"-dioxolane)]-2-methyl-4-(2'-oxo-1'-pyrrolidinyl)-6- nitro-2H-1-benzopyran (SKP-450), a novel antihypertensive agent

Administration (p.o.) of SKP-450, 2-[2"-(1",3"-dioxolane)]-2-methyl-4-(2'-oxo-1'-pyrrolidinyl)-6-nitro-2H- 1-benzopyran, a novel antihypertensive agent, to hypercholesterolemic Syrian hamsters led to a significant reduction in plasma lipids in a dose-dependent manner, i.e., a 10.8% to 29% reduction in low-density lipoprotein cholesterol at doses of 0.3 to 10 mg/kg of SKP-450. SKP-450 was found to specifically inhibit the hepatic microsomal lanosterol 14alpha-methyl demethylase (14alpha-DM) in a competitive manner (Ki:2.65 microM). Furthermore, a dose-dependent decrease in the 14alpha-DM activity by SKP-450 parallelled the cholesterol synthetic rate in vitro in both the rat hepatic S10 fractions (supernatants at 10,000 g; IC50:20 microM) and Chinese hamster ovary cells (IC50:23 microM). However, this phenomenon was not seen in AR45 cells, which are deficient in 14alpha-DM, suggesting that 14alpha-DM is the major target for the inhibitory action of SKP-450 in regard to cholesterol biosynthesis.     

Relative dissociation energies of protonated peptides by electrospray ionization/surface-induced dissociation

Relative dissociation energies (RDEs) are obtained for the major fragment ions produced by electrospray ionization/surface-induced dissociation of singly protonated triglycine, tetraglycine, leucine enkephalin, and leucine enkephalin arginine. A previously described data analysis method (Lim, H.; et al. J. Phys. Chem. B 1998, 102, 4753) is employed to analyze the energy-resolved mass spectra by subtracting out the distribution of energy transferred to the surface, integrating over the distribution of the incident ion energy, and taking into account the precursor ion initial internal energy and kinetic energy distributions. These variables are optimized by anchoring the RDE for the lowest energy fragment of a given precursor ion to its literature values and then using these optimized parameters to obtain the other RDEs. The RDEs of the four major fragments of triglycine vary from 2.4 eV for the b(2) fragment ion to 6.0 eV for the a(2) ion. The RDEs of the four major fragments of tetraglycine vary from 3.2 eV for the y(2) ion to 5.7 eV for the a(2) ion. The leucine enkephalin RDEs range from 1.1 eV for the b(4) ion to 2.1 eV for the b(2) ion. The leucine enkephalin arginine RDEs all lay between 2.5 and 3.5 eV. The overall trend of fragmentation order for all peptides is (y(n), b(n)) < a(n) and is consistent with the results from other experiments. The peptide RDEs presented here are only as accurate as the literature values to which they are anchored. Determination of absolute dissociation energies from SID data will require further refinement of the data analysis method.     

Quantification of surface damage of tool steels after EDM

The surface transformation and damage in AISI O1, A2, D2 and D6 tool steels after EDM were investigated. The results show that the recast layer is composed of two distinct layers: a topmost layer solidifying inwards from the specimen surface and an intermediate layer solidifying outwards from the base of the molten metal. The depth of surface cracks is found to correlate well with the thickness of the white layer, the latter being a layer of rapidly solidified material which, depending on the tool steel material, may consist either primarily of the topmost recast layer, or both the topmost and a large part of the intermediate recast layer. The density of surface cracks, however, correlates better with the thickness of the overall recast layer.

Attempts were made to quantify the depth of white (or damaged) layer with respect to the process parameters and surface roughness after EDM. It is found that with a fixed dielectric and flushing condition, the damaged layer correlates well with the pulse energy irrespective of thetool steel material. On the other hand, even though the thickness of the white layer increases with the surface roughness, the result shows considerably more scatter. Based on the present findings, ways of estimating the depth of the damaged layer produced by EDM are proposed.     

cDNA cloning and functional characterization of the mouse Ca2+-gated K+ channel, mIK1. Roles in regulatory volume decrease and erythroid differentiation

We have cloned from murine erythroleukemia (MEL) cells, thymus, and stomach the cDNA encoding the Ca2+-gated K+ (KCa) channel, mIK1, the mouse homolog of hIK1 (Ishii, T. M., Silvia, C., Hirschberg, B., Bond, C. T., Adelman, J. P., and Maylie, J. (1997) Proc. Natl. Acad. Sci.(U. S. A. 94, 11651-11656). mIK1 mRNA was detected at varied levels in many tissue types. mIK1 KCa channel activity expressed in Xenopus oocytes closely resembled the Kca of red cells (Gardos channel) and MEL cells in its single channel conductance, lack of voltage-sensitivity of activation, inward rectification, and Ca2+ concentration dependence. mIK1 also resembled the erythroid channel in its pharmacological properties, mediating whole cell and unitary currents sensitive to low nM concentrations of both clotrimazole (CLT) and its des-imidazolyl metabolite, 2-chlorophenyl-bisphenyl-methanol, and to low nM concentrations of iodocharybdotoxin. Whereas control oocytes subjected to hypotonic swelling remained swollen, mIK1 expression conferred on oocytes a novel, Ca2+-dependent, CLT-sensitive regulatory volume decrease response. Hypotonic swelling of voltage-clamped mIK1-expressing oocytes increased outward currents that were Ca2+-dependent, CLT-sensitive, and reversed near the K+ equilibrium potential. mIK1 mRNA levels in ES cells increased steadily during erythroid differentiation in culture, in contrast to other KCa mRNAs examined. Low nanomolar concentrations of CLT inhibited proliferation and erythroid differentiation of peripheral blood stem cells in liquid culture.