Controlling an oscillating Jackson-type network having state-dependent service rates

We consider a Jackson-type network comprised of two queues having state-dependent service rates, in which the queue lengths evolve periodically, exhibiting noisy cycles. To reduce this noise a certain heuristic, utilizing regions in the phase space in which the system behaves almost deterministically, is applied. Using this heuristic, we show that in order to decrease the probability of a customers overflow in one of the queues in the network, the server in that same queue – contrary to intuition – should be shut down for a short period of time. Further noise reduction is obtained if the server in the second queue is briefly shut down as well, when certain conditions hold.     

Fluorescence-dip infrared spectroscopy and predissociation dynamics of OH A 2Sigma+ (v = 4) radicals

Fluorescence-dip infrared spectroscopy, an UV-IR double-resonance technique, is employed to characterize the line positions, linewidths, and corresponding lifetimes of highly predissociative rovibrational levels of the excited A (2)Sigma(+) electronic state of the OH radical. Various lines of the 4 <--2 overtone transition in the excited A (2)Sigma(+) state are observed, from which the rotational, centrifugal distortion, and spin-rotation constants for the A (2)Sigma(+) (v = 4) state are determined, along with the vibrational frequency for the overtone transition. Homogeneous linewidths of 0.23-0.31 cm(-1) full width at half maximum are extracted from the line profiles, demonstrating that the N = 0 to 7 rotational levels of the OH A (2)Sigma(+) (v = 4) state undergo rapid predissociation with lifetimes of < or =23 ps. The experimental linewidths are in near quantitative agreement with first-principles theoretical predictions.     

Dynamics of curved DNA molecules: prediction and experiment

We have developed a quantitative predictive model capable of describing the dynamics of migration of intrinsically curved DNA fragments on polyacrylamide gels. The model takes into account structural features of DNA, end-to-end distance, screening of hydrodynamic interactions, ionic strength of buffer, electrostatic persistence length, structural fluctuations of the macromolecule, counter condensation, and variation of dielectric constant and viscosity of water with MPD. In doing so, we have also addressed a decade old issue on the effect of the organic solvent 2-methyl-2,4-pentanediol on gel migration of phased A-tracts. We show here that A-tract-solvent interactions are less favored compared with A-tract-A-tract and solvent-solvent interactions.     

Interfacial reciprocal grafting by free radical reactions in polymer blends

Recent developments in the field of reactive compatibilization of polymer blends prepared by melt processing focus on the addition of low molecular weight compounds. This work deals with in situ compatibilization through the formation of graft or crosslinked copolymers at the interface. Mixtures of semicrystalline hydrocarbon polymers have been subjected to free radical reactivity, in a co-rotating twin screw extruder (ZSK 30) in a single step. The particular system, high density polyethylene and polyamide 6, was blended in the presence of a peroxide and a reactive bifunctional monomer, maleic anhydride. Because of a combined effect, the reaction appears to occur mainly at the interface, where the resulting grafted copolymer acts as an anchor for the final stabilization of the biphasic system. Different analytical techniques, such as differential scanning calorimetry, scanning electron microscopy and tensile testing, helped in characterizing the resulting blends and confirmed the high level of interfacial grafting and the expected improvement in mechanical properties.     

The Hydrazine–O2 Redox Couple as a Platform for Organocatalytic Oxidation: Benzo[c]cinnoline‐Catalyzed Oxidation of Alkyl Halides to Aldehydes

An organocatalytic oxidation platform that capitalizes on the capacity of hydrazines to undergo rapid autoxidation to diazenes is described. Commercially available benzo[c]cinnoline is shown to catalyze the oxidation of alkyl halides to aldehydes in a novel mechanistic paradigm involving nucleophilic attack, prototropic shift, and hydrolysis. The hydrolysis and reoxidation events occur readily with only adventitious oxygen and water. A survey of the scope of viable substrates is shown along with mechanistic and computational studies that give insight into this mode of catalysis.     

Free Glycine Accelerates the Autoproteolytic Activation of Human Asparaginase

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Highlights? Increased expression of hASNase3 was observed in several tumors, but the relevance is unclear ? Cancer cells have increased glycolytic flux and thus have more glycine but less aspartate ? Glycine activates the asparaginase activity of hASNase3 by promoting self-cleavage ? Thus, glycine may act as a sensor that regulates cellular aspartate concentrations     

The sonochemical coating of cotton withstands 65 washing cycles at hospital washing standards and retains its antibacterial properties

Hospital-acquired nosocomial infections are a major health, and consequently financial issue, in the world healthcare system. The problem of bacterial infections in general, and in hospitals in particular, has led to extensive scientific and industrial efforts to fabricate antibacterial textiles. A sonochemical coating machine was developed and built and its ability to coat antibacterial nanoparticles (NPs) onto 40–50 meter length of materials on a roll to roll basis at a speed of 22 cm/min. Cotton coated sonochemically with copper oxide nanoparticles (CuO NPs) was found to maintain its antibacterial properties even after 65 cycles of washings according to hospital protocols of hygienic washing (75 °C). This demonstrates the good quality and high stability of this sonochemically produced NPs coating on textiles. Durable antibacterial textiles such as these may be suitable for wide spread use in future hospital environments where hygiene control is of paramount importance.     

Theoretical and Experimental Analysis of Protoporphyrin IX Photodegradation Using Multi-Wavelength Light Sources

Photodynamic procedures have been used in many applications, ranging from cancer treatment to microorganism inactivation. Photodynamic reactions start with the activation of a photosensitizing molecule with light, leading to the production of cytotoxic molecules that promote cell death. However, establishing the correct light and photosensitizer dosimetry for a broadband light source remains challenging. In this study, we proposed a theoretical mathematical model for the photodegradation of protoporphyrin IX (PpIX), when irradiated by multi-wavelength light sources. The theoretical model predicts the experimental photobleaching (temporal change in PpIX concentration) of PpIX for different light sources. We showed that photobleaching occurs independently of the light source wavelengths but instead depends only on the number of absorbed photons. The model presented here can be used as an important mathematical approach to better understand current photodynamic therapy protocols and help achieve optimization of the doses delivered.     

Dynamic proton magnetic resonance studies on complex spin systems. Non-mutual three-spin exchange in N-(trideuteriomethyl)-2-cyanoaziridine

At room temperature and below, the proton NMR spectrum of N-(trideuteriomethyl)-2-cyanoaziridine consists of two superimposed ABC patterns assignable to two N-invertomers; a single time-averaged ABC pattern is observed at 158.9°C. The static parameters extracted from the spectra in the temperature range from –40.3 to 23.2°C and from the high-temperature spectrum permit the calculation of the thermodynamic quantities ΔH⁰ = ?475±20 cal mol^?1 (?1.987 ± 0.084 kJ mol^?1) and ΔS⁰ = 0.43±0.08 cal mol^?1 K^?1 (1.80±0.33 J mol^?1 K^?1) for the cis ? trans equilibrium. Bandshape analysis of the spectra broadened by non-mutual three-spin exchange in the temperature range from 39.4–137.8°C yields the activation parameters ΔH_tc^≠ = 17.52±0.18 kcal mol^?1 (73.30±0.75 kJ mol^?1), ΔS_tc^≠ = ?2.08±0.50 cal mol^?1 K^?1 (?8.70±2.09 J mol^?1 K^?1) and ΔG_tc^≠ (300 K) = 18.14±0.03 kcal mol^?1 (75.90±0.13 kJ mol^?1) for the trans → cis isomerization. An attempt is made to rationalize the observed entropy data in terms of the principles of statistical thermodynamics.