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Background: Considering the importance of photoneutron production in linear accelerators, it is necessary to describe and measure the photoneutrons produced around modern linear accelerators. Objective: The aim of the present research is to study photoneutron production for the 18 MV photon beam of a Siemens Primus Plus medical linear accelerator.Material and Methods: This study is an experimental study. The main components of the head of Siemens Primus Plus linac were simulated using MCNPX 2.7.0 code. The contribution of different components of the linac in photoneutron production, neutron source strength, neutron source strength and photon and electron spectra were calculated for the flattening filter and flattening filter free cases for the 18 MV photon beam, and was scored for three fields of 5 × 5 cm2, 10 × 10 cm2 and 20 × 20 cm2 in size. Results: The results show that the primary collimator has the largest contribution to production of neutrons. Moreover, the photon fluence for the flattening filter free case is 8.62, 6.51 and 4.62 times higher than the flattening filter case for the three fields, respectively. The electron fluences for the flattening filter free case are 4.62, 2.93 and 2.79 times higher than with flattening filter case for the three fields under study, respectively. In addition to these cases, by increasing the field size, the contribution of neutron production related to the jaws is reduced, so that when the field size increases from 5 × 5 cm2 to 20 × 20 cm2, a 17.93% decrease in photoneutron production was observed. Conclusion: In all of the accelerators, the neutron strength also increases with increasing energy. The calculated neutron strength was equal to 0.83×1012 neutron Gy −1 at the isocenter.

Using the gluon condensation (GC) model, we predict a possible connection of the broken power phenomenon between the energy spectra of electron and proton. We find that once the GC occurs, large amount of gluons accumulate near the GC threshold. This phenomenon provides a possible source of the power rule, broken in the energy spectra of cosmic rays, and even predicts the connection between them. [ABSTRACT FROM AUTHOR]

The results of petawatt laser system development in RFNC-VNIIEF and preliminary experiments of laser-matter interaction at intencity about 1019 W/cm2 are presented. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: The specific sorption of Eu(III) and Y(III) on γ-alumina was investigated with solid-state 1H NMR. Solution pH was shown to influence the recorded 1H NMR spectra of γ-alumina, and thus, metal ion-containing samples were prepared under constant pH conditions, 8.00±0.05. The metal ion concentration in the samples was varied between 6.58×10−7 M–3.95×10−4 M in case of Y3+ and 6.58×10−8 M–1.32×10−4 M in case of Eu3+. The mineral concentration was kept constant at 4g/l. After separation of the liquid phase, the samples were dried under vacuum to remove physisorbed water from the mineral surface. However, even after 48h of drying at 150°C and 20 mTorr, water was still detected in the proton spectra as two distinct peaks with chemical shifts at 1.3 and 0.9ppm. The europium addition to the γ-alumina samples induced significant spectral changes in comparison with yttrium-containing samples. These changes were attributed to the paramagnetism of europium rather than to complexation reactions occurring on the mineral surface. Proton spectra obtained for yttrium samples were therefore used to detect the spectral changes induced by the sorption reaction itself. The results revealed a large distribution of protons being removed from the mineral surface upon yttrium complexation. Removed protons were assigned to both bridging surface hydroxyls such as (AlVI)2–OH as well as to terminal hydroxyls, e.g., of type AlVI–OH. Acidic protons belonging to (AlVI)3–OH groups were not observed to participate in the surface reaction. [Copyright &y& Elsevier]

In this paper, gradient selected (gs) NMR experiments are presented for editing the proton, and two-dimensional (2D) 1H–13C-correlation spectra of different fractions of the petroleum according to the carbon multiplicity. The state of the art experiments allow the much sought after simplification and resolution of the proton, and 2D 1H–13C correlated NMR spectra of such fractions in considerably reduced acquisition times. The proton-edited experiments offer a new and much convenient way of unambiguous estimation of cut-off points between signals from α-methyl and α-methylene protons in 1H NMR spectra of petroleum fractions. The gs edited 2D 1H–13C correlated spectra of the fractions provide carbon multiplicity information and hetero-nuclear correlation with improved sensitivity in a single experiment leading to complete spectral assignment. These experiments have been applied to complex petroleum fractions for the first time, and show lot of potential to resolve various hitherto unanswered issues concerning the interpretation of the complex NMR spectra of the petroleum products. [Copyright &y& Elsevier]