Martina Fuss

Radiation Damage in Biomolecular Systems

Radiation damage in biomolecular systems , Radiation damage in biomolecular systems , کتابخانه دیجیتال جندی شاپور اهواز

Excitation of electronic states in tetrahydrofuran by electron impact

We report on differential and integral cross section measurements for the electron impact excitation of the three lowest lying Rydberg bands of electronic states in tetrahydrofuran. The energy range of the present experiments was 15-50 eV with the angular range of the differential cross section measurements being 15°-90°. The important effects of the long-range target dipole moment and the target dipole polarizability, on the scattering dynamics of this system, are evident from the present results. To the best of our knowledge, there are no other theoretical or experimental data against which we can compare the cross section results from this study.

The role of pyrimidine and water as underlying molecular constituents for describing radiation damage in living tissue: A comparative study

Sem PDF. This research was supported by the Australian Research Council (ARC) through its Centres of Excellence Program. D.B.J. thanks the ARC for provision of a Discovery Early Career Researcher Award. We also acknowledge the support of the Spanish Ministerio de Economia y Competitivad under Project No. FIS 2012-31230 and the European Union COST Actions (MP1002 and CM1301). P.L.V. acknowledges the Portuguese Foundation for Science and Technology (FCT-MEC) through research grants PTDC/FIS-ATO/1832/2012, UID/FIS/00068/2013, and SFRH/BSAB/105792/2014. P.L.V. also acknowledges his Visiting Professor position at Flinders University, Adelaide, South Australia.

Differential cross sections for the electron impact excitation of pyrimidine

We report on differential cross section (DCS) measurements for the electron-impact excitation of the electronic states of pyrimidine. The energy range of the present measurements was 15-50 eV with the angular range of the measurements being 10°-90°. All measured DCSs displayed forward-peaked angular distributions, consistent with the relatively large magnitudes for the dipole moment and dipole polarizability of pyrimidine. Excitations to triplet states were found to be particularly important in some energy loss features at the lower incident electron energies. To the best of our knowledge there are no other experimental data or theoretical computations against which we can compare the present results.

Electron scattering cross sections from HCN over a broad energy range (0.1–10 000 eV): Influence of the permanent dipole moment on the scattering process

We report theoretical integral and differential cross sections for electron scattering from hydrogen cyanide derived from two ab initio scattering potential methods. For low energies (0.1-100 eV), we have used the symmetry adapted-single centre expansion method using a multichannel scattering formulation of the problem. For intermediate and high energies (10-10,000 eV), we have applied an optical potential method based on a screening corrected independent atom representation. Since HCN is a strong polar molecule, further dipole-induced excitations have been calculated in the framework of the first Born approximation and employing a transformation to a space-fixed reference frame of the calculated K-matrix elements. Results are compared with experimental data available in the literature and a complete set of recommended integral elastic, inelastic, and total scattering cross sections is provided from 0.1 to 10,000 eV.

An investigation into electron scattering from pyrazine at intermediate and high energies

Total electron scattering cross sections for pyrazine in the energy range 10-500 eV have been measured with a new magnetically confined electron transmission-beam apparatus. Theoretical differential and integral elastic, as well as integral inelastic, cross sections have been calculated by means of a screening-corrected form of the independent-atom representation (IAM-SCAR) from 10 to 1000 eV incident electron energies. The present experimental and theoretical total cross sections show a good level of agreement, to within 10%, in the overlapping energy range. Consistency of these results with previous calculations (i.e., the R-matrix and Schwinger Multichannel methods) and elastic scattering measurements at lower energies, below 10 eV, is also discussed.

Modelling single positron tracks in Ar

In this study, we present a complete set of positron interaction cross sections for scattering from Ar, for incident energies ranging from 0 to 10 keV. Experimental data have been critically reviewed from previous experiments performed at the Australian National University and University College London. Differential and integral cross sections, including the effect of positronium formation, have been calculated by using two different optical potential methods. The results of these calculations, in combination with experimental cross sections and experimental energy-loss spectra, have been established as input parameters for an event-by-event Monte Carlo simulation procedure to generate single positron tracks in argon. The reliability of this method to obtain energy deposition models at the nano-scale is also discussed.

Carbohydrate-carbohydrate interaction prominence in 3D supramolecular self-assembly.

Self-association in water of biologically significant carbohydrate molecules is a controversial topic due to the strong solvation of these molecules in this solvent and the difficulty to experimentally detect these very weak intermolecular forces by biophysical techniques. Herein we report the tremendous ability of amphiphilic carbohydrate molecules to form complex three-dimensional architectures. We have experimentally observed the 3D self-assembly into multilayers of disaccharide neoglycolipid dimers on graphite by means of noncontact AFM and we have also theoretically modeled the interaction between two dimers in order to learn about the structure and composition of these layers. A simple bilayer structure as observed for many amphiphilic lipids was discarded by the experiments. Instead, based on the good agreement between experiments and calculations, we propose that multilayer formation takes place through the assembly of building blocks consisting of two dimers each. The fundamental key in the formation of this supramolecular structure is the complementarity between the van der Waals surfaces of the amphiphilic carbohydrate molecules, a result which differs from the most common idea that H-bonding interactions are prominent in carbohydrate-mediated interactions.

Energy deposition by a 106Ru/106Rh eye applicator simulated using LEPTS, a low-energy particle track simulation

The present study introduces LEPTS, an event-by-event Monte Carlo programme, for simulating an ophthalmic (106)Ru/(106)Rh applicator relevant in brachytherapy of ocular tumours. The distinctive characteristics of this code are the underlying radiation-matter interaction models that distinguish elastic and several kinds of inelastic collisions, as well as the use of mostly experimental input data. Special emphasis is placed on the treatment of low-energy electrons for generally being responsible for the deposition of a large portion of the total energy imparted to matter.

Electron scattering cross section calculations for polar molecules over a broad energy range

We report computational integral and differential cross sections for electron scattering by two different polar molecules, HCN and pyrimidine, over a broad energy range. We employ, for low energies, either the single-centre expansion (ePOLYSCAT) or the R-matrix method, while for the higher energies we select a corrected form of the independent-atom representation (IAM-SCAR). We provide complete sets of integral electron scattering cross sections from low energies up to 10,000 eV. Our present calculated data agree well with prior experimental results.