Cytochrome-c detection

Following a myocardial infarction (MI) cells die or are damaged and their contents leak into the blood circulation, resulting in elevated serum levels of various enzymes, proteins, and organic molecules. Over the past few decades, it has become standard practice to employ the detection of these elevated substances as markers for the confirmation of MIs and to monitor MI patients’ response to treatment. Although it has previously been shown that cytochrome-c, a small respiratory protein, is among those elevated, the lack of a suitable detection system has prevented its routine use in the diagnosis of MIs. We present a preliminary study in which chemiluminescence was employed to detect elevated levels of cytochrome-c in the serum of MI patients. The technique, which is specific for c-type proteins, is approx 30 times more sensitive than the traditional Coomassie blue stain and can detect as little as 0.03 μg of protein. It also has potential for diagnostic use in other diseases that are characterized by mitochondrial damage.     

The hydrogenation of styrenes by hydridocobalt tetracarbonyl

The rates of hydrogenation of several styrene derivatives by stoichiometric hydridocobalt tetracarbonyl [HCo(CO)₄] were measured and compared. The relative rates are discussed in terms of conjugative and steric effects on the geminate radical pair mechanism. An improved method for determining HCo(CO)₄ concentration is described.     

Optimization of scrapping decisions: Theory and applications

Contrary to the variety of models and procedures for optimizing the ordering decision in inventory control theory, no comparable tools exist for the scrapping decision. Thus, the current paper constitutes a step in this direction. Using a simple deterministic model, the basic economics and structure of the problem are introduced first. Then we determine explicitly scrap-optimal turn-around-times as well as the corresponding scrap- and rest-quantities. Accounting for the stochastic nature of demand, the model is generalized and algorithms for determination of optimal scrapping decision are discussed. Finally we compare the results and discuss practical applications.     

The steady boundary value problem for charged incompressible fluids: PNP/Navier–Stokes systems

The initial-boundary value problem for the Poisson–Nernst–Planck/Navier–Stokes model was investigated in [J.W. Jerome, R. Sacco, Global weak solutions for an incompressible charged fluid with multi-scale couplings: initial-boundary-value problem, Nonlinear Anal. 71 (2009) e2487–e2497], where an existence theory was demonstrated, based upon Rothe’s method of horizontal lines. In this article, the steady case is considered, and the existence of a weak solution is established for the boundary-value problem. This solution satisfies a weak maximum principle for the concentrations relative to the boundary values. As noted in the above-mentioned citation, the model assumes significance because of its connection to the electrophysiology of the cell, including neuronal cell monitoring and microfluidic devices in biochip technology. The model has also been used in other applications, including electro-osmosis. The steady model is especially important in ion channel modeling, because the channel remains open for milliseconds, and the transients appear to decay on the scale of tens of nanoseconds.     

Eine empfindliche Methode zur Bestimmung von Beryllium mit Chromazurol-S und 2,2′-Bipyridyl

Zusammenfassung Eine spektralphotometrische Methode zur Bestimmung von Mikrogrammengen Beryllium mittels Chromazurol-S in Anwesenheit von 2,2-Bipyridyl wurde beschrieben. Letzteres steigert die Empfindlichkeit der Methode wesentlich; _=610nm beträgt 5,4 × 10⁴. Die Komplexverbindung gehorcht dem Lambert-Beerschen Gesetz im Konzentrationsbereich von 0,002 bis 0,2 ppm Be. Die maximale Farbintensität wird bei pH 5 sofort erreicht. Das molare Verhältnis BeCHASBip beträgt 121. Die vorgeschlagene Methode ist empfindlich und bei Anwendung von ÄDTA als Maskierungsmittel befriedigend selektiv.

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A sensitive method for assay of beryllium with chromazurol S and 2,2-bipyridyl

Summary A spectrophotometric method of assay for microgram amounts of beryllium by means of chromazurol S in presence of 2,2-bipyridyl was described. The latter appreciably enhances the sensitivity of the method; _=610nm is 5.4 × 10⁴. The complex compound obeys the Lambert-Beer law in the concentration range 0.002 to 0.2 ppm Be. The maximum color intensity is immediately attained at pH 5. The molar ratio BeCHASbip is 121. The suggested method is sensitive and has satisfactory selectivity when EDTA is applied as masking agent.

     

Bayesian Estimation of Discrete Multivariate Latent Structure Models With Structural Zeros

In multivariate categorical data, models based on conditional independence assumptions, such as latent class models, offer efficient estimation of complex dependencies. However, Bayesian versions of latent structure models for categorical data typically do not appropriately handle impossible combinations of variables, also known as structural zeros. Allowing nonzero probability for impossible combinations results in inaccurate estimates of joint and conditional probabilities, even for feasible combinations. We present an approach for estimating posterior distributions in Bayesian latent structure models with potentially many structural zeros. The basic idea is to treat the observed data as a truncated sample from an augmented dataset, thereby allowing us to exploit the conditional independence assumptions for computational expediency. As part of the approach, we develop an algorithm for collapsing a large set of structural zero combinations into a much smaller set of disjoint marginal conditions, which speeds up computation. We apply the approach to sample from a semiparametric version of the latent class model with structural zeros in the context of a key issue faced by national statistical agencies seeking to disseminate confidential data to the public: estimating the number of records in a sample that are unique in the population on a set of publicly available categorical variables. The latent class model offers remarkably accurate estimates of population uniqueness, even in the presence of a large number of structural zeros.     

Rationality, regularity, and -cofiniteness

We demonstrate that, for vertex operator algebras of CFT type, -cofiniteness and rationality is equivalent to regularity. For -cofinite vertex operator algebras, we show that irreducible weak modules are ordinary modules and -cofinite, is -cofinite, and the fusion rules are finite.

     

On the definition of the stress tensor in granular media

This paper investigates the definition of the stress tensor within a granular assembly, when inertial effects are likely to occur. It is shown that the stress tensor can be expressed as a sum of two terms. A first term corresponds to the standard definition of the stress, according to the Love–Weber formula; this term is related to the contact forces existing within adjoining particles. A second term accounts for dynamic effects related to rotation velocities and accelerations of the particles. These results are checked from discrete numerical simulations in order to examine in which context the contribution of inertial effects should not be omitted. With this aim, the simulation of a granular specimen collapse and then a silo discharge is considered.