Oligolysine‐Conjugated Zinc(II) Phthalocyanines as Efficient Photosensitizers for Antimicrobial Photodynamic Therapy

A series of zinc(II) phthalocyanines conjugated with an oligolysine chain (n=2, 4, and 8) were synthesized and characterized by using various spectroscopic methods. As shown by using UV/Vis and fluorescence spectroscopic methods, these compounds were nonaggregated in N,N‐dimethylformamide, and gave a weak fluorescence emission and high singlet oxygen quantum yield (Φ_Δ=0.86–0.89) as a result of their di‐α‐substitution. They became slightly aggregated in water with 0.05 % Cremophor EL, but they could still generate singlet oxygen effectively. The antimicrobial photodynamic activities of these compounds were then examined against various bacterial strains, including the Gram‐positive methicillin‐sensitive Staphylococcus aureus ATCC 25923 and methicillin‐resistant Staphylococcus aureus ATCC BAA‐43, and the Gram‐negative Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853. Generally, the dyes were much more potent toward the Gram‐positive bacteria. Only 15 to 90 nM of these photosensitizers was required to induce a 4 log reduction in the cell viability of the strains. For Escherichia coli, the photocytotoxicity increased with the length of the oligolysine chain. The octalysine derivative showed the highest potency with a 4 log reduction concentration of 0.8 μM . Pseudomonas aeruginosa was most resistant to the photodynamic treatment. The potency of the tetralysine derivative toward a series of clinical strains of Staphylococcus aureus was also examined and found to be comparable with that toward the nonclinical counterparts. Moreover, the efficacy of these compounds in photodynamic inactivation of viruses was also examined. They were highly photocytotoxic against the enveloped viruses influenza A virus (H1N1) and herpes simplex virus type 1 (HSV1), but exhibited no significant cytotoxicity against the nonenveloped viruses adenovirus type 3 (Ad3) or coxsackievirus (Cox B1). The octalysine derivative also showed the highest potency with an IC₅₀ value of 0.05 nM for the two enveloped viruses.     

Bayesian uncertainty quantification of recent shock tube determinations of the rate coefficient of reaction H + O2→ OH + O

We analyze the ignition delay in hydrogen–oxygen combustion and the important chain ‐branching reaction H + O₂→ OH + O that occurs behind the shock waves in shock tube experiments. We apply a stochastic Bayesian approach to quantify uncertainties in the theoretical model and experimental data. The approach involves a statistical inverse problem, which has four “components” as input information: (a) model, (b) prior joint probability density function (PDF) of the uncertain parameters, (c) experimental data, and (d) uncertainties in the scenario parameters. The solution of this statistical inverse problem is a posterior joint PDF of the uncertain parameters from which we can easily extract statistical information. We first perform a parametric study to investigate how the level of the total uncertainty (which we define as the sum of model uncertainty and experimental uncertainty) affects the uncertainty in the rate coefficient k₁ of the reaction H + O₂→ OH + O, which is “most likely” expressed by k₁=1.73×10²³T^?2.5exp(?11550/T) cm³ mol^?1 s^?1 over the experimental temperature range 1100–1472 K. We also introduce the idea of “irreducible” uncertainty when considering other parameters in the system. After statistically calibrating the parameters modeling the rate coefficient k₁, we predict its 95% confidence interval (CI) for different temperature regimes and compare the CI against the values of k₁ obtained deterministically. Our results show that a small uncertainty in gas temperature (±5 K) introduces appreciable uncertainty in k₁. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 586–597, 2012     

Double-action dark matter,PAMELA and ATIC

Motivated by a two-bump (or 1-peak plus 1-hump) structure in the ATIC data, we perform a statistical analysis fitting the PAMELA and ATIC data to a dark matter model, in which the dark matter particle can undergo both annihilation and decay. Using a chi-square analysis we show that both data can be simultaneously fitted better with such a double-action dark matter particle. We use an existing neutrino mass model in literature to illustrate the idea.     

Selective processing of semiconductor nanowires by polarized visible radiation

Semiconductor nanowires have attracted intense interest due to potential applications in electronics, sensors and photonics. Introduction of dopants and their subsequent activation are essential for exploiting the electronic properties of semiconductor materials. In this work, we demonstrate pulsed laser annealing of silicon nanowires by visible radiation to be an efficient way for activating incorporated dopants and repairing implantation damage in a process that is compatible with sensitive flexible substrates. In situ electrical monitoring was used to study the laser annealing process. The absorption of laser light in SiNWs was shown to be strongly dependent on the light polarization and nanowire diameter based on finite difference time domain simulations. PACS 42.62.-b; 64.70.Nd; 78.67.n; 81.16.c     

Insensitive bounds for the moments of the sojourn time distribution in the M/G/1 processor-sharing queue

This paper studies the M/G/1 processor-sharing (PS) queue, in particular the sojourn time distribution conditioned on the initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are not suitable for computational purposes. This paper derives readily applicable insensitive bounds for all moments of the conditional sojourn time distribution. The instantaneous sojourn time, i.e., the sojourn time of an infinitesimally small job, leads to insensitive upper bounds requiring only knowledge of the traffic intensity and the initial job size. Interestingly, the upper bounds involve polynomials with so-called Eulerian numbers as coefficients. In addition, stochastic ordering and moment ordering results for the sojourn time distribution are obtained. AMS Subject Classification: 60K25, 60E15 This work has been partially funded by the Dutch Ministry of Economic Affairs under the program ‘Technologische Samenwerking ICT-doorbraakprojecten’, project TSIT1025 BEYOND 3G.     

Opial-type inequalities for differential operators

Some continuous and discrete versions of Opial-type inequalities which are readily applicable to differential and difference operators are established. These generalize earlier results of Anastassiou and Pe?ari?, and of Koliha and Pe?ari?.     

Intra-cavity second-harmonic and sum-frequency generation in a diode-pumped broadband Yb-doped fibre laser

Intra-cavity nonlinear frequency mixing in a diode-pumped, broadband Yb-doped fibre laser has been investigated. Second-harmonic generation of the fibre output, second-harmonic generation of the residual pump beam and sum frequency mixing between the two was achieved simultaneously, resulting in three colour operation in the blue-green region. Including the nonlinear crystal inside the cavity is also shown to be effective in reducing fluctuations in the output power.