Preparation of heparin-glyceryl controlled-pore glass affinity media for the separation of alpha- and beta-lipoproteins.

The preparation of a stable affinity medium with heparin as the affinity ligand has been investigated. Glyceryl controlled-pore glass (CPG) was activated with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate and coupled with heparin. This affinity medium was used to separate some simple proteins, trypsinogen and lysozyme, in a high-performance liquid chromatographic configuration. The heparin-glyceryl-CPG was also used to separate alpha- and beta-lipoproteins in human serum. The effectiveness of the separation is confirmed by radial immunodiffusion and the determination of the cholesterol content of each of the separated fractions.     

Fluoral-P,a member of a selective family of reagents for aldehydes

The compound 4-amino-3-penten-2-one is introduced as a member of a selective family of reagents for aldehydes. The stability, selectivity and reactivity of the reagent are described and its utility in automatic determinations of formaldehyde is demonstrated. It is shown that the condensation reaction between 4-amino-3-penten-2-one (called Fluoral-P) and formaldehyde gives a product detectable by fluorescence. The flow injection system utilizing this reagent can be used to determine formaldehyde in the lower. nanomole range.     

The mechanism of the electrochemical oxidation of thiourea

Cyclic voltammetry and potentiostatic coulometry were used to study the electrochemical oxidation of thiourea in aqueous solutions of nitric acid, nitric acid—ammonium nitrate, and ammonium nitrate—ammonium hydroxide and in acetonitrile. These studies were carried out at glassy carbon and/or platinum working electrodes. In acetonitrile, the cyclic voltammograms show one oxidation peak at + 0.6 V and a reduction peak at —0.1 V. In aqueous solutions up to about pH 6, there is a second oxidation peak at 1.3 V which is irreversible and its height is sensitive to acidity. These experiments have confirmed that in acidic and neutral solutions the oxidation of thiourea proceeds via a slow 1-e transfer reaction producing a radical [(NH₂)₂—C—S]⁺. Further direct oxidation of this radical takes place only at higher potentials (ca. 1.2 V) and involves hydration and protontransfer equilibria. Otherwise, C,C'-dithiodiformamidinium ion is formed by a fast dimerization reaction. Coulometric and chronopotentiometric measurements have shown that in strong acid the second oxidation step involves one electron, while at lower acidities the further oxidation involving three (and possibly five) electrons proceeds in two (or three) steps of very similar potential.     

Room-temperature luminescence of benzo[f]quinoline, p-aminobenzoic acid, phenanthrene, and 4-phenylphenol on a variety of solid surfaces

Analytical figures of merit for the room-temperature luminescence of four model compounds with quite different chemical structures were compared. The compounds were adsorbed on four different surfaces that have been employed recently in solid-surface luminescence analysis. The solid materials investigated were silica gel with a polyacrylate binder, filter paper, 1% polyacrylic acid-NaBr, and 80% α-cyclodextrin-NaCl. The experimental conditions were optimized to give enhanced luminescence signals. In some cases, filter paper and 80% α-cyclodextrin-NaCl gave comparable analytical results. However, filter paper gave the best overall results.     

The high-performance liquid chromatography and detection of phospholipids and triglycerides: Part 2. Comparison of an ultraviolet absorption and post-column reactor detector

A liquid chromatographic ultraviolet absorption detector (at 195 nm) and a novel postcolumn reactor detector are compared for use in the detection of triglyceride and phospholipid molecular species. The detection limit for the u.v. detector depends on the degree of unsaturation of the lipid sample (3 × 10^-6–2 × 10^-8 M in the detector cell for 0–3 double bonds per acyl group). The post-column reactor detector is responsive to equivalents of lipid and has detection limits of 5 × 10^-7 M for triglycerides and 2 × 10^-6 M for phospholipids. The log u.v./post-column reactor detector response ratios are linearly related to the log of the degree of unsaturation of the lipid, indicating the usefulness of both detectors for quantifying triglycerides and phospholipids.     

How often is a polygon bounded by three sides?

LetL _n be the set of lines (no two parallel) determining ann-sided bounded faceF in the Euclidean plane. We show that the number,f(L _n), of triples fromL _n that determine a triangle containingF satisfies and these bounds are best. This result is generalized tod-dimensional Euclidean space (without the claim that the upper bound is attainable).     

Synthesis,crystal structure,and reactivity of alkali and silver salts of sulfonated imidazoles

Both 2-methylimidazole and 2-ethyl-4-methylimidazole were monosulfonated with oleum in the five position. In crystals of the monohydrate of 2-methylimidazole-5-sulfonic acid, hydrogen bonds link the molecules into a 3-dimensional network, while in crystals of 2-ethyl-4-methylimidazole-5-sulfonic acid, corrugated 2-dimensional layers are present. The Li and Ag salts and the bis(trimethylsilyl) derivatives of 2-ethyl-4-methylimidazole-5-sulfonic acid were prepared, and there is evidence for doubly deprotonated imidazolesulfonate in aqueous solution. The monohydrate of the Li salt and the Ag salt also form a 3-dimensional, H-bonded network. Only in the Ag salt does the asymmetric unit consist of more than one basic formula unit. One Ag atom is 2-coordinate and links two nitrogen atoms, while the other Ag atom has distorted tetrahedral coordination and links the sulfonate groups into an infinite chain. Reactions of the silver salt with 1,4-dibromobutane in non-protic solvents such as 1-methyl-2-pyrrolidone were used to link two of the imidazolesulfonic acid units with a 4-carbon chain at the nitrogens.     

A collaboratory for radiation therapy treatment planning optimization research

Intensity modulated radiation therapy treatment planning (IMRTP) is a challenging application of optimization technology. We present software tools to facilitate IMRTP research by computational scientists who may not have convenient access to radiotherapy treatment planning systems. The tools, developed within Matlab and CERR (computational environment for radiotherapy research), allow convenient access, visualization, programmable manipulation, and sharing of patient treatment planning data, as well as convenient generation of dosimetric data needed as input for treatment plan optimization research. CERR/Matlab also provides a common framework for storing, reviewing, sharing, and comparing optimized dose distributions from multiple researchers.     

Bose-Einstein condensation in a circular waveguide

We have produced Bose-Einstein condensates in a ring-shaped magnetic waveguide. The few-millimeter diameter, nonzero-bias ring is formed from a time-averaged quadrupole ring. Condensates that propagate around the ring make several revolutions within the time it takes for them to expand to fill the ring. The ring shape is ideally suited for studies of vorticity in a multiply connected geometry and is promising as a rotation sensor.     

Summing over a network without revealing summands

Consider a network in which each node possesses a secret member of a finite abelian group. In this paper we present a protocol by which the nodes can compute the sums of their secret elements without revealing them to each other. The security against discovery of the secret values as a result of conspiracies among nodes or compromise of channels between nodes is shown to depend on the connectivity of the graph defined by the network. Moreover, we are able to quantify exactly the amount of information revealed as a result of a conspiracy of a given set of nodes or compromise of a given set of channels.