Irradiance dependence of the He-Ne laser-induced protection against UVC radiation in E. coli strains

He-Ne laser pre-irradiation-induced protection against UVC damage was investigated in wild-type E. coli K12 strain AB1157 and its isogenic DNA repair mutant strains. At a dose of 7 kJ/m(2), pre-irradiation was observed to induce protection in recA proficient strains (AB1157 and uvrA(-) AB1886) at both the irradiances investigated (2 and 100 W/m(2)). However, at the same dose (7 kJ/m(2)), while no protection was observed at 100 W/m(2) in the recA(-) strain, some protection appeared to be there at 2 W/m(2). Mechanistic studies carried out on these strains at the two irradiances suggest that, whereas the protection observed at 100 W/m(2) is mediated by singlet oxygen, that observed at 2 W/m(2) is not. Further, the fact that protection at 100 W/m(2) was observed only in recA proficient strains suggests that it may arise due to the induction of DNA repair processes controlled by the recA gene. The latter may arise due to the oxidative stress produced by singlet oxygen generated by He-Ne laser irradiation. In contrast, the protection observed at 2 W/m(2) appears to be independent of the DNA repair proficiency of the strain.     

Carbohydrates as building blocks of privileged ligands

“Privileged ligands” are chiral auxiliaries of wide applicability in asymmetric catalysis. In the previous decades, their effective three-dimensional structures have often been reproduced by using building blocks from a “chiral pool”, such as the carbohydrates. This strategy has provided unique ligand moieties which combine the performance of “privileged ligands” with increased flexibility and accessibility. This review gives an overview of the research within this field, giving emphasis to the best results obtained with each ligand type.     

Dynamic evolution of topological defects around drops and bubbles rising in a nematic liquid crystal

We report observations of topological defects around drops and bubbles that rise through a vertically aligned nematic liquid crystal. We provide direct evidence for downstream convection of the Saturn-ring defect and its transformation to a hyperbolic point defect. The point defect is convected further in the wake of the drop or bubble as the rising velocity increases. In equilibrium, both defect configurations may persist for long times in the narrow cell. But the point defect sometimes spontaneously opens into a Saturn ring, indicating the latter as the globally stable configuration in the presence of tight wall confinement.     

Exploiting damped techniques for nonlinear conjugate gradient methods

In this paper we propose the use of damped techniques within Nonlinear Conjugate Gradient (NCG) methods. Damped techniques were introduced by Powell and recently reproposed by Al-Baali and till now, only applied in the framework of quasi-Newton methods. We extend their use to NCG methods in large scale unconstrained optimization, aiming at possibly improving the efficiency and the robustness of the latter methods, especially when solving difficult problems. We consider both unpreconditioned and Preconditioned NCG. In the latter case, we embed damped techniques within a class of preconditioners based on quasi-Newton updates. Our purpose is to possibly provide efficient preconditioners which approximate, in some sense, the inverse of the Hessian matrix, while still preserving information provided by the secant equation or some of its modifications. The results of an extensive numerical experience highlights that the proposed approach is quite promising.     

Multinuclear solid state NMR investigation of two polymorphic forms of ciprofloxacin-saccharinate

Two polymorphic forms of a novel pharmaceutical compound, ciprofloxacin-saccharinate (CIP-SAC), are analyzed using one dimensional (1D) and two dimensional (2D) (1)H nuclear magnetic resonance (NMR) at fast magic angle spinning (MAS). Additionally (15)N spectroscopy and (1)H-(13)C correlation experiments were performed to complement our conclusions. The 1D (1)H NMR spectra of CIP and complexes reveal valuable information about the ionic bonding between ciprofloxacin and saccharine. Additionally, these spectra allow us to perform a clear characterization of each solid form, giving the number of molecules per unit cell in one of the polymorphs. From 2D (1)H-(1)H spectra obtained through double quantum correlations we can arrive at important conclusions about the hydrogen bonding, conformation, and intra and inter-molecular interactions present in these compounds. Comparing and contrasting the (1)H-(1)H correlation data obtained for both polymorphic forms and taking into account the single crystal structure data existing for the solid form CIP-SAC (II) was possible to extract some conclusions on the polymorph CIP-SAC (I) where no single crystal information is available. (1)H MAS NMR is shown to be an important tool in the field of polymorphism and for the characterization of multicomponent pharmaceutical compounds.     

On mixed joint discrete universality for a class of zeta-functions. II

We investigate the mixed joint discrete value distribution and the mixed joint discrete universality for the pair consisting of a rather general form of zeta-function with an Euler product and a periodic Hurwitz zeta-function with transcendental parameter. The common differences of relevant arithmetic progressions are not necessarily the same. Also some generalizations are given. For this purpose, certain arithmetic conditions on the common differences are used.

     

An adaptive truncation criterion,for linesearch-based truncated Newton methods in large scale nonconvex optimization

Starting from the paper by Nash and Sofer (1990), we propose a heuristic adaptive truncation criterion for the inner iterations within linesearch-based truncated Newton methods. Our aim is to possibly avoid “over-solving” of the Newton equation, based on a comparison between the predicted reduction of the objective function and the actual reduction obtained. A numerical experience on unconstrained optimization problems highlights a satisfactory effectiveness and robustness of the adaptive criterion proposed, when a residual-based truncation criterion is selected.     

Numerical Experiences with New Truncated Newton Methods in Large Scale Unconstrained Optimization

Recently, in [12] a very general class oftruncated Newton methods has been proposed for solving large scale unconstrained optimization problems. In this work we present the results of an extensive numericalexperience obtained by different algorithms which belong to the preceding class. This numerical study, besides investigating which arethe best algorithmic choices of the proposed approach, clarifies some significant points which underlies every truncated Newton based algorithm.     

Micromachined bulk PZT tissue contrast sensor for fine needle aspiration biopsy

This paper describes a micromachined piezoelectric sensor, integrated into a cavity at the tip of a biopsy needle, and preliminary experiments to determine if such a device can be used for real-time tissue differentiation, which is needed for needle positioning guidance during fine needle aspiration (FNA) biopsy. The sensor is fabricated from bulk lead zirconate titanate (PZT), using a customized process in which micro electro-discharge machining is used to form a steel tool that is subsequently used for batch-mode ultrasonic micromachining of bulk PZT ceramic. The resulting sensor is 50 microm thick and 200 microm in diameter. It is placed in the biopsy needle cavity, against a steel diaphragm which is 300 microm diameter and has an average thickness of 23 microm. Devices were tested in materials that mimic the ultrasound characteristics of human tissue, used in the training of physicians, and with porcine fat and muscle tissue. In both schemes, the magnitude and frequency of an electrical impedance resonance peak showed tissue-specific characteristics as the needle was inserted. For example, in the porcine tissue, the impedance peak frequency changed approximately 13 MHz from the initial 163 MHz, and the magnitude changed approximately 1600 Omega from the initial 2100 Omega, as the needle moved from fat to muscle. Samples including oils and saline solution were tested for calibration, and an empirical tissue contrast model shows an approximately proportional relationship between measured frequency shift and sample acoustic impedance. These results suggest that the device can complement existing methods for guidance during biopsies.     

On the value distribution of the Matsumoto zeta-function

The Matsumoto zeta-function is defined by a polynomial Euler product and is a generalization of classical zeta-functions. In the paper a discrete limit theorem in the sense of the weak convergence of probability measures on the complex plane for the Matsumoto zeta-function is proved.