Application of radioactive tracer technique to study the kinetics and mechanism of reversible ion-isotope exchange with strongly basic anion-exchange resin Indion-850

The kinetics of reversible bromide ion-isotope exchange with Indion-850 resin was studied in the concentrations range from 0.0025 to 0.100 M and the temperature varied from 27.0 to 48.0°C. Two sets of experiments were performed: exchange of the inactive resin in the bromide form with the bromide solution spiked with ⁸²Br tracer and exchange of the labeled resin with an inactive bromide solution. For both forward and reverse bromide ion-isotope exchange reactions, the rate constants, amount of bromide ions exchanged, and initial rate of bromide ion exchange were calculated. The rate constants of the forward and reverse reactions are essentially equal. In both cases, the amount of bromide ion exchanged and the initial rate of bromide ion exchange increase with temperature. Published in Russian in Radiokhimiya, 2008, Vol. 50, No. 6, pp. 555–557. The test was submitted by the authors in English.     

Ionizing radiation and marketing simulation on bioactive compounds and quality of grapefruit (Citrus paradisi c.v. Rio Red)

Bioactive compounds in citrus fruits have been shown to be protective against chronic diseases such as cancer and heart disease, but their levels may be affected by postharvest treatments such as storage and irradiation. In this study, grapefruits were exposed to gamma irradiation at 0, 150 and 300 Gy and then stored at 10 °C for 36 d, followed by an additional 20 d at 20 °C. Flavonoid content, terpenoid content, quality (acidity and total soluble solids) and phenylalanine ammonia-lyase (PAL) activity were evaluated at regular intervals during storage. Irradiation and storage affected (P ? 0.05) the levels of bioactive compounds in grapefruit; however, the effect of storage was prominent. Irradiation differentially affected the flavonoid content of pulp and peel. Fruits exposed to 300 Gy had higher (P ? 0.01) narirutin content in peel compared to control fruits at 12 and 56 d after storage. While storage increased the d-limonene and myrcene content in all treatments, control fruit had higher terpenoid content at the end of the storage. PAL activity was found to be in traces in the peel. In general, irradiation or storage had no considerable effect on total soluble solids; however, acidity decreased (P ? 0.05) with storage.     

Review of the process development aspects of electrochemical dyeing: its impact and commercial applications

This review discusses the recent progress made in both direct and indirect electrochemical dyeing processes and the parameters that control the dyeing process.     

Sensitized monomer fluorescence and excitation energy transfer in perylene-doped phenanthrene in crystalline and in polymer matrix

Sensitized monomer fluorescence and excitation energy transfer in crystalline and spin cast polymer films was investigated at room temperature. The fluorescence spectra of perylene doped phenanthrene reveals the characteristic monomeric emission of perylene and partial quenching of phenanthrene emission. The excimer formation of perylene is not observed in mixed crystalline luminophors and in spin cast films of the phenanthrene luminophors. The observed quenching of phenanthrene emission indicates the excitation energy transfer from phenanthrene to perylene in crystalline as well as in polymer matrix. Energy transfer is not observed in the experiments when phenanthrene and perylene were physically mixed where the components exist separately. The overlap between the excitation spectrum of perylene and emission spectrum of the phenanthrene supports the fact that the perylene molecules accept the excitation energy from phenanthrene. The energy transfer was found to depend upon the perylene concentration.     

Influence of pre- and post-harvest factors and processing on the levels of furocoumarins in grapefruits (Citrus paradisi Macfed.)

The changes in the levels of three furocoumarins such as dihydroxybergamottin (DHB), paradisin A and bergamottin in Rio Red and Marsh White cultivars of grapefruits were monitored from November to May. The levels of DHB and bergamottin in both varieties of grapefruits decreased as the season progressed except for the bergamottin in Marsh White grapefruit. Influence of growing location, processing and storage on the levels of these compounds were also evaluated. Among the varieties the highest levels of DHB (2.266 μg/ml) and bergamottin (2.411 μg/ml) were found in Flame grapefruit grown in Florida. The highest level of paradisin A was found in Rio Red grapefruit grown in California and the lowest levels were observed in Rio Red grapefruit grown organically in Texas. Hand squeezed juice contained 1.98, 1.06 and 3.03-fold more DHB, paradisin A and bergamottin, respectively as compared to processed juice. The levels of furocoumarins showed a decreasing trend in all the juices with progress of storage. Levels of furocoumarins were more in cartons container than the cans and cardboard container juices.     

Variation of bioactive furocoumarins and flavonoids in different varieties of grapefruits and pummelo

Grapefruit juice has been shown to increase the oral bioavailability of many therapeutic drugs. Certain citrus bioactive compounds such as furocoumarins and flavonoids have potent inhibitory effects on cytochrome P450 3A4 (CYP 3A4) enzyme and P-glycoprotein. The levels of these bioactive compounds in the grapefruit juice may affect the magnitude and mechanism of grapefruit juice-induced drug interaction. The levels of three furocoumarins such as dihydroxybergamottin (DHB), paradisin A and bergamottin and flavonoids have been separated and quantified using high-performance liquid chromatography (HPLC) in seven varieties of grapefruits and its parent pummelo. Considerable differences were observed in the levels of these bioactive compounds in different grapefruit varieties. Ray Red showed the lowest (0.492 ± 0.027 DHB μg/ml, 0.059 ± 0.001 μg/ml paradisin A and 0.344 ± 0.030 μg/ml bergamottin) levels of all three furocoumarins and Duncan contain the highest amount of DHB (2.587 ± 0.432 μg/ml) and bergamottin (1.004 ± 0.068 μg/ml), where as Star Ruby contain the highest levels of paradisin A. Pummelo contain the highest levels of naringin (4.587 ± 0.061 mg/ml), while Rio Red showed the lowest level (1.986 ± 0.145 mg/ml) of naringin.     

Reducing feedback for opportunistic scheduling in wireless systems

We study reducing feedback overhead of users' channel state information required for opportunistic scheduling at a base station while minimizing the throughput penalty incurred due to reduced feedback. We first propose a simple contention based scheme known as 'static splitting' for best effort traffic. The idea is to divide users into static groups, with users that belong to a group, and have their currently supported rate above a threshold, contending to send their current feedback to the base station. This is combined with maximum quantile scheduling -scheduling a user whose current rate is high relative to its distribution, to obtain thresholds that are independent of users' rate distributions even when they are heterogeneous, allowing off-line optimization of thresholds. Next we develop the insight that for a traffic mixture of best effort and real-time traffic one has to combine contention and polling to reduce feedback while providing quality of service. We propose a scheme based on this insight. Under this scheme we prove a lower bound on the service seen by a real-time when users' channel capacities are fast fading. Furthermore, we propose a heuristic modification that is able to exploit a larger fraction of opportunism. Simulation results illustrate the performance advantage of the proposed schemes.     

Quantitative Analysis of PMLA Nanoconjugate Components after Backbone Cleavage

Multifunctional polymer nanoconjugates containing multiple components show great promise in cancer therapy, but in most cases complete analysis of each component is difficult. Polymalic acid (PMLA) based nanoconjugates have demonstrated successful brain and breast cancer treatment. They consist of multiple components including targeting antibodies, Morpholino antisense oligonucleotides (AONs), and endosome escape moieties. The component analysis of PMLA nanoconjugates is extremely difficult using conventional spectrometry and HPLC method. Taking advantage of the nature of polyester of PMLA, which can be cleaved by ammonium hydroxide, we describe a method to analyze the content of antibody and AON within nanoconjugates simultaneously using SEC-HPLC by selectively cleaving the PMLA backbone. The selected cleavage conditions only degrade PMLA without affecting the integrity and biological activity of the antibody. Although the amount of antibody could also be determined using the bicinchoninic acid (BCA) method, our selective cleavage method gives more reliable results and is more powerful. Our approach provides a new direction for the component analysis of polymer nanoconjugates and nanoparticles.