Mid-ultraviolet light-emitting diode detects dipicolinic acid

Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA (lambda(max) doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.     

The Poincaré Center Problem

We present two examples of real planar polynomial vector fields with an orbitally linearizable saddle point such that they are neither rationally reversible nor Liouvillian integrable. We show that vector fields from one of these examples form an isolated component of the so-called integrable saddle variety. Next, we discuss the problem of partial duality between real centers and real integrable saddles and the problem of continuous moduli for the center variety. The first author is supported by the Polish MNiSzW Grant No. 1 P03A 015 29, and the second by a MCYT/FEDER grant number MTM2005–06098–C02–01 and by a CIRIT grant number 2005SGR 00550.     

Effect of amaranth seeds in diet on oxidative status in plasma and selected tissues of high fructose-fed rats

The aim of this study was to assess the influence of amaranth seeds in different doses, under conditions of oxidative stress induced by dietary fructose, on antioxidant status of selected rat tissues, erythrocytes and plasma. Fructose administration caused oxidative stress that was manifested by the increase in plasma malondialdehyde and by the decrease in the enzymatic antioxidant activity. Co-administration of amaranth seeds influenced the oxidative stress, as was evidenced by decreasing malondialdehyde in plasma and changing the activities of antioxidant enzymes (erythrocyte superoxide dismutase, catalase, and plasma glutathione peroxidase). Our findings demonstrate that amaranth seeds can act as a moderate protective agent against fructose-induced changes. Our results suggest that the antioxidative system of plasma, heart and lungs is more efficient when amaranth seeds are present in the diet.     

Comparative investigations of the condensation of R134a and R404A refrigerants in pipe minichannels

The present paper describes the results of experimental investigations of heat transfer and pressure drop during the condensation of the R134a and R404A refrigerants in pipe minichannels with internal diameters d = 0.31–3.30 mm. The results concern investigations of the local heat transfer coefficient and a pressure drop in single mini-channels. The results were compared with calculations according to the correlations proposed by other authors. Within the range of the examined parameters of the condensation process in mini-channels produced from stainless steel, it was established that the values of the heat transfer coefficient may be described with Akers et al. and Shah correlations within a limited range of the mass flux density of the refrigerant and the mini-channel diameter. A pressure drop during the condensation of these refrigerants is described in a satisfactory manner with Friedel and Garimella correlations. On the basis of the experimental investigations, the authors proposed their own correlation for the calculation of local heat transfer coefficient α_x.     

A reinterpretation of measurements in developing annular two-phase flow

Measurements of developing films in adiabatic high pressure steam-water flow in annular geometry have been reanalyzed and compared to a linearized film-flow model. The development rate of the outer film could be determined with good accuracy in four cases. In one case it was also possible to conclude that the inner film develops faster than the outer one. When compared to the linearized model, these observations show that the deposition rate has to be almost independent of the drop concentration at the investigated conditions. Furthermore, any significant deposition by direct impaction of drops can be excluded as it would couple the development of the two films. These conclusions are quite general and do not depend on the use of any particular correlation for the deposition or entrainment rates. Finally, a rough estimate of the deposition rate was possible, confirming that deposition rates are considerably lower at high pressure steam-water flows than in air-water flows.     

Action of γ-irradiated patulin onSaccharomyces cerevisiae

Summary The action of-irradiated patulin onSaccharomyces cerevisiae OCK 2144 in liquid culture was studied. Patulin irradiated in an aqueous solution with doses ranging over 0.34–1.36 kGy inhibited the yeast growth in a proportion to the concentration of undestroyed toxin. Patulin disappearance in the growth medium occurred between 12–72 h of incubation at 30° C. The patulin content did not essentially change in the period of log phase of yeast growth which is accompanied by rapid glucose uptake.

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Einfluß des -bestrahlten Patulins aufSaccharomyces cerevisiae

Zusammenfassung Es wurde die Wirkung von-bestrahltem Patulin aufSaccharomyces cerevisiae OCK 2144 in Flüssigkultur untersucht. Patulin beeinflußte nach der Bestrahlung in wäßrigen Lösungen mit Dosen von 0,34 bis 1,36 kGy das Hefewachstum entsprechend dem Toxininhalt. Der Patulinabbau im Zuchtmedium erfolgte zwischen 12 und 72 h der Inkubation bei 30 °C. Der Patulingehalt veränderte sich nicht in der logarithmischen Phase des Hefewachstums, in dem der schnelle Glucoseverbrauch erfolgte.

     

Limit Cycles for Multidimensional Vector Fields. The Elliptic Case

We consider polynomial vector fields of the form and their polynomial perturbations of degree n. We present a sufficient condition that the perturbed system has an invariant surface close to the plane z = 0. We study limit cycles which appear on this surface. The linearized condition for limit cycles, bifurcating from the curves y ² – x ³ + 3x = h, leads to a certain 2- dimensional integral (which generalizes the elliptic integrals). We show that this integral has a representation R ₁(h)I ₁ + + R _e(h)I _e, where R _j (h) are rational functions with degrees of numerators and denominators bounded by O(n). In the case of constant and one-dimensional matrix A(x,y) we estimate the number of zeros of the integral by const n.