Electron in an Ultrashort Laser Pulse

After the classical approach to acceleration of a charged particle by -form impulsive force, we consider the corresponding quantum theory based on the Volkov solution of the Dirac equation. We determine the modified Compton formula for frequency of photons generated by the scattering of the -form laser pulse on the electron in a rest frame.     

Dynamic Mechanical and Dielectric Properties of Ethylene Vinyl Acetate/Carbon Nanotube Composites

A comparative study of the dielectric and mechanical properties of ethylene vinyl acetate copolymer (EVA) filled with various concentrations of pristine and modified carbon nanotubes is reported. The surface of the carbon nanotubes was modified with 4-(2-(cholesteryloxycarboxy)ethyl) phenyl to improve the interaction of the filler with the block copolymer matrix. The improved interaction and the better dispersion of the modified carbon nanotubes (mMWCNTs) were demonstrated by a detailed study of the EVA molecular mobility through dynamic mechanical analysis and broadband dielectric relaxation spectroscopy. The storage modulus of the nanocomposite with 6 wt.% of mMWCNTs at ?50°C was enhanced by 103%, whereas for the nanocomposite with the same amount of unmodified filler, the storage modulus was only enhanced by 76% compared to the pure elastomeric matrix. This difference is more pronounced in the rubbery region in which the storage moduli were increased by 117% and 48% for the composite with the modified and unmodified fillers, respectively. The morphologies of the nanocomposites were studied with scanning and transmission electron microscopies to demonstrate the dispersion of the mMWCNTs within the EVA matrix.     

Lacunary series in weighted spaces of analytic functions

We improve a recent result of Yang and Xu (Arch. Math. 96 (2011), 151–160) by proving that if ψ is a normal function on [1, ∞) and \({f(z)=\sum_{n=0}^\infty a_n z^{k_n}}\) (|z| < 1) is an analytic function with Hadamard gaps, then

$\frac 1C \sup_{n\ge 0} \frac{|a_n|}{\psi(k_n)} \le \sup_{0 < r < 1} \frac{|f(r\zeta)|}{\psi(1/(1-r))} \le C\sup_{n\ge 0}\frac{|a_n|}{\psi(k_n)}, \quad |\zeta|=1,$

where C is a constant independent of ζ and {a _n }.

     

Growth and characterization of pulsed laser deposited ZnO thin films

One of the most important and promising materials from metal oxides is ZnO with specific properties for near UV emission and absorption optical devices. The properties of ZnO thin films strongly depend on the deposition method. Among them, pulsed laser deposition (PLD) plays an important role for preparing various kinds of ZnO films, e.g. doped, undoped, monocrystalline, and polycrystalline. Different approaches — ablation of sintered ZnO pellets or pure metallic Zn as target material are described. This contribution is comparing properties of ZnO thin films deposited from pure Zn target in oxygen atmosphere and those deposited from sintered ZnO target. There is a close connection between final thin film properties and PLD conditions. The surface properties of differently grown ZnO thin films are measured by secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Furthermore, different approaches — ablation of sintered ZnO pellet or pure metallic Zn as target materials are described. The main results characterize typical properties of ZnO films versus technological parameters are presented. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia     

Dynamic stability of fcc crystals under isotropic loading from first principles

Lattice dynamics and stability of four fcc crystals (Al, Ir, Pt and Au) under isotropic (hydrostatic) tensile loading are studied from first principles using the linear response method and the harmonic approximation. The results reveal that, contrary to former expectations, strengths of all the studied crystals are limited by instabilities related to soft phonons with finite or vanishing wavevectors. The critical strains associated with such instabilities are remarkably lower than those related to the volumetric instability. On the other hand, the corresponding reduction of the tensile strength is by 20% at the most. An analysis of elastic stability conditions is also performed and the results obtained by means of both approaches are compared.     

Acridine Based N-Acylhydrazone Derivatives as Potential Anticancer Agents: Synthesis,Characterization and ctDNA/HSA Spectroscopic Binding Properties

A series of novel acridine N-acylhydrazone derivatives have been synthesized as potential topoisomerase I/II inhibitors, and their binding (calf thymus DNA—ctDNA and human serum albumin—HSA) and biological activities as potential anticancer agents on proliferation of A549 and CCD-18Co have been evaluated. The acridine-DNA complex 3b (-F) displayed the highest K_b value (K_b = 3.18 × 10³ M⁻¹). The HSA-derivatives interactions were studied by fluorescence quenching spectra. This method was used for the calculation of characteristic binding parameters. In the presence of warfarin, the binding constant values were found to decrease (K_SV = 2.26 M⁻¹, K_b = 2.54 M⁻¹), suggesting that derivative 3a could bind to HSA at Sudlow site I. The effect of tested derivatives on metabolic activity of A549 cells evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or MTT assay decreased as follows 3b(-F) > 3a(-H) > 3c(-Cl) > 3d(-Br). The derivatives 3c and 3d in vitro act as potential dual inhibitors of hTopo I and II with a partial effect on the metabolic activity of cancer cells A594. The acridine-benzohydrazides 3a and 3c reduced the clonogenic ability of A549 cells by 72% or 74%, respectively. The general results of the study suggest that the novel compounds show potential for future development as anticancer agents.     

The lattice of positive quasi-orders on a semigroup

In the present paper we study some properties of positive quasi-orders on simigroups and using these results we describe all semilattice and chain homomorphic images of a semigroup. Supported by Grant 0401B of RFNS through Math. Inst. SANU.     

Analysis of cytokinin nucleotides by capillary zone electrophoresis with diode array and mass spectrometric detection in a recombinant enzyme in vitro reaction

A capillary zone electrophoresis (CZE) method for separation of adenosine and N⁶-isopentenyladenosine (cytokinin) nucleotides was developed, optimized and validated. Aqueous solutions of several amino acids were evaluated as the background electrolyte constituents. Separation of six nucleotides in less than 20 min with high theoretical plate number (up to 400 000 for isopentenyladenosine triphosphate) was achieved using a 100 mM sarcosine/ammonia buffer at pH 10.0. The detection limits of the CZE-UV method are in the low micromolar range (0.69–1.27 μmol L⁻¹). Good repeatability of migration times (within 1.3%), peak areas (within 1.8%) and linearity (R² > 0.999) was achieved over the concentration range 5–1000 μmol L⁻¹. The method was used to assay the activity of the recombinant Arabidopsis thaliana isopentenyltransferase 1 (AtIPT1). Baseline separation of isopentenylated nucleotides by CE–ESI-MS using a volatile buffer (30 mM ammonium formate; pH 10.0) was accomplished. The identities of the reaction products – isopentenyladenosine di- and triphosphate were confirmed by HPLC-QqTOF-MS. Dephosphorylation of ATP was observed as a parallel reaction.     

Mössbauer Spectrometer with Novel Moving System and Resonant Detection of Gamma Rays

Temperature-dependent ⁵⁷Fe Mössbauer spectroscopy has been used to elucidate the hyperfine parameters and dynamical behavior of the metal atom in several organo-iron complexes which have one or more η⁵ P₅ ring structures as ligated groups. The spin-lattice relaxation of the (paramagnetic) one-electron oxidation products occurs on a time scale fast compared to τ_1/2 (ME) at temperatures in the range 85 < T < 320 K.