Investigation of the inelastic deuteron scattering mechanism for 24Mg at E d = 15.3 MeV

Results from measuring the angular dependence of differential cross sections of elastic and inelastic deuteron scattering by the ²⁴Mg nucleus with the formation of the ground and first excited states 2⁺, 1.369 MeV at E _d = 15.3 MeV for deuteron angles interval from 21.5° to 161.5° (lab) are presented. Experimental results are compared with calculations in various approximations of the coupled channels model. The influence of heavy particle stripping mechanisms and consecutive particle transfer is also discussed.     

Crystallization of poly(α-methyl-α-N-propyl-β-propiolactones) prepared from homogeneous and heterogeneous initiators

Half-crystallization times t_½, enthalpies of fusion ΔH, melting temperatures T_f glass transition temperatures T_g x-ray patterns, and morphologies were obtained for nine samples of poly(α-methyl-α-n-propyl-β-propiolactones) prepared from different homogeneous or heterogeneous initiators. The bulk of the results indicates that all samples can be classified into two categories: Polymers A having t_½?, 100 min, ΔH ? 26 J/g, T ? 376 K, T_g ? 275 K, and Polymers B having t_½ ? 10 min, ΔH ? 14.5 J/g T ? 425 K and T_g ? 271 K. Polymers A were prepared with homogeneous initiators while polymers B were polymerized with heterogeneous intiators. The difference in crystallization behavior between polymers A and polymers B is certainly due to a difference in microstructure, brought about by the initiators, which has been qualitatively observed by NMR.     

Formation of Cyclobutane Thymine Dimers from UVA Photosensitization of Pyridopsoralen Monoadducted DNA

The present report provides evidence that thymine dimerization can be UVA photosensitized at a tetranucleotide, 5′-TATT-3′, by a 7-methyl-pyrido(3, 4-c)psoralen monoadduct in DNA. The efficiency of the photoprocess depends on the tetranucleotide flanking sequences. These results demonstrate that one DNA lesion can originate the contiguous formation of a second type of lesion and emphasize the sequence-specific response to interaction of drugs with DNA. Results are related to the sensitivity of DNA to 1, 10-phenanthroline-cuprous ion complex nucleolytic activity and discussed in terms of the major role of local deformability of DNA in interaction with ligands.     

Liquid crystal polymers with terminally 1- phenyl −2-(4-cyanophenyl)-ethane substituted side chains

The synthesis of a series of liquid crystalline side-chain polyacrylates with oligoether spacers and 1-(4-benzoyloxyphenyl)-2-(4 -cyanophenyl)ethane mesogenic moiety is reported. Polymers were prepared by radical polymerization of the corresponding acrylate monomers. The liquid crystalline nature of these polymers was established by calorimetric measurements, optical texture observations and X-ray investigations. For the polymer with the diethylene oxide spacer (EO dimer), the unusual I-N-S_Ad-N_re sequence was observed. For the polymer with the trimer spacer, only “fluid” smectic phases were evidenced.     

Using a 120-cm cyclotron to study the synchronous effects of ionizing radiation and hypomagnetic conditions on the simplest biological objects

The effect of α-particles on one of the simplest unicellular organisms, Synechocystis sp. PCC 6803 cyanobacteria, is studied using a 120-cm cyclotron. Suspensions of cells are irradiated in a cuvette with walls made of thin mylar films. The energy of α-particles in the solution is 24 MeV. The linear energy transfer (LET) of α-particles is close to that of relativistic nuclei of the neon-magnesium group in galactic cosmic rays, making it possible to simulate their effect on biological objects. A number of apparent changes in the Synechocystis spectral characteristics are found for samples irradiated in and outside a hypomagnetic field.     

Dynamic deformation of light nuclei in excited states

An important property—the dynamic deformation of B* light aligned nuclei—is investigated for the nuclear reactions A(x, y)B* → γ + B ₀ by measuring the y-γ correlations. Dynamic deformation is determined from the orientation tensors of multipolar moments. Normalization constants of the contributions from even-rank orientation tensors are determined from the condition of coincidence between dynamic and static deformations of the B* nucleus for θ _y = 0°. Experimental dynamic deformations of ¹²C(2⁺) nuclei caused by the inelastic scattering of α particles and deuterons are determined, along with the ¹⁰Be(2⁺) nuclei formed in reaction ⁹Be(d, p)¹⁰Be(2⁺). It is shown that the dynamic deformation of the aligned nuclei depends on how they are formed and their structure, and evolves substantially when the angle θ _y is varied.     

Angular correlations in the inelastic-scattering process 24Mg(d, dγ)24Mg at E d = 15.3 MeV

The double-differential cross sections for the reaction ²⁴Mg(d, dγ _1.369)²⁴Mg at the projectiledeuteron energy of E _d = 15.3 MeV weremeasured for deuteron emission angles in the forward hemisphere. All even spin-tensor components of the density matrix for the 2⁺ state of the ²⁴Mg nucleus at 1.369 MeV were reconstructed, and its orientation properties were determined. These experimental results were compared with the results of calculations based on various versions of the coupled-channel method.     

Phonon-assisted optical bands of nanosized powdery SrAl2O4:Eu crystals: Evidence of a multimode Pekarian

A stoichiometric powder composed of nanosized grains of SrAl₂O₄:Eu²⁺ was synthesized by combustion method at 500 °C with the subsequent calcination at 1000 °C. The zero-phonon line position, parameter of the Stokes shift, heat release factor and effective phonon energy were studied experimentally and analyzed in the framework of the multimode Pekar–Huang–Rhys model. Experimental data show that the optical 4f–5d$4f\text{–}5d$ transitions in Eu²⁺ ion exhibit a broad asymmetric electron–vibrational bands with a pronounced structure near the maxima. The form-function of the absorption and luminescence bands are theoretically analyzed in the framework of the model of the linear electron–vibrational interaction assuming strong coupling with the local vibration (estimated Pekar–Huang–Rhys parameter a=2S=10$a=2S=10$ and frequency ?ω=509 cm⁻¹$?\omega =509{\text{cm}}^{-1}$) and relatively weak interaction with the crystal phonons. The last results in an effective temperature dependent broadening of the discrete lines corresponding to the local vibrations and to a specific shape of the whole phonon assisted band (multimode Pekarian). Providing specific interrelation between the key parameters the calculated absorption and luminescence bands exhibit peculiar temperature dependent structured peaks in a qualitative agreement with the experimental data.     

Optical and luminescent properties of the lead and barium molybdates

Time-resolved luminescence as well as excitation and reflectivity spectra of the oriented lead and barium molybdate single crystals were studied using synchrotron radiation. Features in reflectivity spectra in the fundamental absorption region were analyzed. The contribution of electronic states of lead cation to the formation of the bandgap in PbMoO₄ is supposed. The role of lead states in the intrinsic luminescence of PbMoO₄ is discussed.     

Synthesis of polylactides by new aluminium Schoff's base complexes

The kinetics of DL‐lactide polymerization was studied in CH₂Cl₂ and dioxane at 25°C and in toluene at 70°C with different aluminium Schiff's base initiators namely HAPENAlOMe, HAPENAlOⁱPr, 5‐ClSALENAlOⁱPr and 5‐ClSALOPHENAlOⁱPr. It was observed that HAPEN‐type complexes derived from 2‐hydroxyacetophenone lead to much faster polymerization as compared to SALEN‐ or 5‐ClSALEN‐type initiators derived from salicylaldehyde. Moreover, substitution of the methoxide group coordinated to the central aluminium by an isopropoxide group brings about an increase in the polymerization rate but leads to transesterification reactions at much lower percentage conversion. On the other hand, replacement of the flexible ethylene diamino group by the more rigid phenylenediamino substituent slows down considerably the polymerization reaction. Analysis of the microstructure of all poly(DL‐lactides) obtained revealed the presence of isotactic sequences in agreement with a first order Markovian statistics.