The effects of relativistic and nonlocal nonlinearities on modulational instabilities in inhomogeneous plasma

A general detailed analysis of the nonlinear generation of localized fields due to the existence of a strong pump field inside an inhomogeneous plasma has been performed taking into account the effects of relativistic and nonlocal nonlinearities on the structure of the plasma resonance region. The nonlinear Schrödinger equation describing the localized fields is investigated. A generalized dispersion relation is obtained to study the modulational instabilities in different cases.     

Structures of oxaliplatin‐oligonucleotide adducts from DNA

Oxaliplatin, [(1R,2R)‐cyclohexane‐1,2‐diamine](ethanedioato‐O,O')platinum(II) shows a great efficiency against colorectal cancer. Although the mode of action of oxaliplatin is not yet understood, it is commonly accepted that binding of oxaliplatin to DNA prevents DNA synthesis and alters protein to DNA binding. In order to elucidate the modified DNA–protein interaction and thus to understand the mechanisms leading to cellular misinterpretation of DNA information and apoptosis, we have identified the preferential binding sites and the dynamics of the oxaliplatin‐DNA intrastrand and interstrand adducts at the oligomer level using high‐performance liquid chromatography/electrospray ionization‐tandem mass spectrometry (HPLC/ESI‐MS/MS) and HPLC/inductively coupled plasma‐MS for quantitative studies. We used a combination of benzonase, alkaline phosphatase and Nuclease S1 for digestion. This digestion procedure allows the study of platinated oligomeric nucleotides and more complex interstrand adducts. The digestion products were mostly chromatographically separated and characterized using HPLC/ESI‐ion trap MS/MS experiments. We could show that the adducts to guanine and adenine are quite dynamic; that is, the ratios are changing for several days. In addition, the resulting adducts provide evidence for the action of the digesting enzymes and indicate that the adduct spectrum at the oligomeric level is different to that at the commonly studies dinucleotide level. Copyright © 2012 John Wiley & Sons, Ltd.     

Amberlite IR-120 catalyzed,microwave-assisted rapid synthesis of 2-aryl-benzimidazoles

An expeditious synthesis of 2-aryl-benzimidazoles by the condensation of o-phenylenediamine with various araldehydes is described. This greener protocol is catalyzed by Amberlite IR-120, and proceeds efficiently in the absence of any organic solvent under microwave irradiation within 3–5 min.     

Inclusion complex of N-nitroso,N-(2-chloroethyl), N′, N′-dibenzylsulfamid with β-Cyclodextrin: Fluorescence and molecular modeling

The inclusion complex of N-nitroso, N-(2-chloroethyl), N′, N′-dibenzylsulfamid with β-Cyclodextrin have been investigated using the spectrofluorescence technique ¹H NMR spectroscopy. The stoichiometric ratio of the complex was found to be 1:1 and the stability constant was evaluated using the Benesi-Hildebrand equation. In order to find the most favorable structure, molecular mechanics calculations were employed to study the inclusion of CENS-Dibenz in β-CD in vacuum and in the presence of water as a solvent. The driving forces for complexation are dominated by non-bonded van der Waals host-guest interactions with very little electrostatic contribution in both environments. After this stage of calculation, both the most stable complexes obtained by MM+ were re-optimized using semi-empirical and quantum mechanical calculations. It was found that the PM3 and the hybrid method ONIOM2 calculations predict the same mode of inclusion of the drug molecule in the host cavity. In the most stable conformation (i.e. Complex A), one of the two aromatic cycles is dipped within the relatively less polar cavity of β-cyclodextrin, while the other aromatic cycle as well as the active groupings (alkylating agent and nitroso group) are directed towards the exterior through the narrow rim of β-CD. This orientation is preferred because it is the most energetically favorable structure. Moreover, statistical thermodynamic calculations demonstrate that the formation of the inclusion complex is an enthalpy-driven process. A comparison between the experimental and theoretical values of ΔG⁰ proves that simulation of the complexes without an explicit treatment of the solvent leads to dubious results.     

An investigation of motion correction algorithms for pediatric spinal cord DTI in healthy subjects and patients with spinal cord injury

Patient and physiological motion can cause artifacts in DTI of the spinal cord which can impact image quality and diffusion indices. The purpose of this investigation was to determine a reliable motion correction method for pediatric spinal cord DTI and show effects of motion correction on DTI parameters in healthy subjects and patients with spinal cord injury. Ten healthy subjects and ten subjects with spinal cord injury were scanned using a 3 T scanner. Images were acquired with an inner field-of-view DTI sequence covering cervical spine levels C1 to C7. Images were corrected for motion using two types of transformation (rigid and affine) and three cost functions. Corrected images and transformations were examined qualitatively and quantitatively using in-house developed code. Fractional anisotropy (FA) and mean diffusivity (MD) indices were calculated and tested for statistical significance pre- and post- motion correction. Images corrected using rigid methods showed improvements in image quality, while affine methods frequently showed residual distortions in corrected images. Blinded evaluation of pre and post correction images showed significant improvement in cord homogeneity and edge conspicuity in corrected images (p < 0.0001). The average FA changes were statistically significant (p < 0.0001) in the spinal cord injury group, while healthy subjects showed less FA change and were not significant. In both healthy subjects and subjects with spinal cord injury, quantitative and qualitative analysis showed the rigid scaled-least-squares registration technique to be the most reliable and effective in improving image quality.     

Band Theory in the Context of the Hamilton-Jacobi Formulation

In the one-dimensional periodic potential case, we formulate the condition of Bloch periodicity for the reduced action by using the relation between the wave function and the reduced action established in the context of the equivalence postulate of quantum mechanics. Then, without appealing to the wave function properties, we reproduce the well-known dispersion relations which predict the band structure for the energy spectrum in the Krönig-Penney model.     

Elastic scattering via quark structure of nucleons

In the framework of the Glauber multiple-scattering theory, the elastic collisions of proton-proton (pp) at the center-of-mass energies = 23.5, 30.7, 44.7, and 52.8 GeV and alpha-proton (p) at = 88 and 89 GeV are analyzed by considering the quark structure of their constituents. The differential cross-section containing the full multiple-scattering series between their quarks is calculated using Gaussian forms for the quark density and quark-quark (QQ) scattering amplitudes. The results obtained from the quark model and the conventional nucleon model are compared with the experimental data. The comparison shows that the nucleon model reproduces the experimental data more satisfactorily than the quark model, and both approaches have limited success in describing the data at such energies. The agreement with the experimental data is improved by the inclusion of the phase variation.     

Preparation and Photophysics of 2-(1-Pyrenyl)acrylic Acid and Its Methyl and 2′,2′,6′,6′-Tetramethyl-4′-Piperidyl Esters

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO^.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form –COO⁻. Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form –COOH and the cationic form –COOH₂⁺. The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1′-oxo-2′,2′,6′,6′-tetramethyl-4′-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO^.).