Identification and rejection of scattered neutrons in AGATA

Gamma rays and neutrons, emitted following spontaneous fission of 252Cf, were measured in an AGATA experiment performed at INFN Laboratori Nazionali di Legnaro in Italy. The setup consisted of four AGATA triple cluster detectors (12 36-fold segmented high-purity germanium crystals), placed at a distance of 50 cm from the source, and 16 HELENA BaF2 detectors. The aim of the experiment was to study the interaction of neutrons in the segmented high-purity germanium detectors of AGATA and to investigate the possibility to discriminate neutrons and gamma rays with the gamma-ray tracking technique. The BaF2 detectors were used for a time-of-flight measurement, which gave an independent discrimination of neutrons and gamma rays and which was used to optimise the gamma-ray tracking-based neutron rejection methods. It was found that standard gamma-ray tracking, without any additional neutron rejection features, eliminates effectively most of the interaction points due to recoiling Ge nuclei after elastic scattering of neutrons. Standard tracking rejects also a significant amount of the events due to inelastic scattering of neutrons in the germanium crystals. Further enhancements of the neutron rejection was obtained by setting conditions on the following quantities, which were evaluated for each event by the tracking algorithm: energy of the first and second interaction point, difference in the calculated incoming direction of the gamma ray, figure-of-merit value. The experimental results of tracking with neutron rejection agree rather well with Geant4 simulations

Discrimination of gamma rays due to inelastic neutron scattering in AGATA

Possibilities of discriminating neutrons and gamma rays in the AGATA gamma-ray tracking spectrometer have been investigated with the aim of reducing the background due to inelastic scattering of neutrons in the high-purity germanium crystals. This background may become a serious problem especially in experiments with neutron-rich radioactive ion beams. Simulations using the Geant4 toolkit and a tracking program based on the forward tracking algorithm were carried out by emitting neutrons and gamma rays from the center of AGATA. Three different methods were developed and tested in order to find 'fingerprints' of the neutron interaction points in the detectors. In a simulation with simultaneous emission of six neutrons with energies in the range 1-5 MeV and ten gamma rays with energies between 150 and 1450 keV, the peak-to-background ratio at a gamma-ray energy of 1.0 MeV was improved by a factor of 2.4 after neutron rejection with a reduction of the photopeak efficiency at 1.0 MeV of only a factor of 1.25.Comment: Accepted for publication in Nuclear Instruments and Methods in Physics Research, A, 26 May 2009; 13 pages, 5 tables, 12 figure

Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A=90

"Why are the tin isotopes soft?" has remained, for the past decade, an open problem in nuclear structure physics: models which reproduce the isoscalar giant monopole resonance (ISGMR) in the "doubly-closed shell" nuclei, $^{90}$Zr and $^{208}$Pb, overestimate the ISGMR energies of the open-shell tin and cadmium nuclei, by as much as 1 MeV. In an effort to shed some light onto this problem, we present results of detailed studies of the ISGMR in the molybdenum nuclei, with the goal of elucidating where--and how--the softness manifests itself between $^{90}$Zr and the cadmium and tin isotopes. The experiment was conducted using the $^{94,96,98,100}$Mo($\alpha,\alpha^\prime$) reaction at $E_\alpha = 386$ MeV. A comparison of the results with relativistic, self-consistent Random-Phase Approximation calculations indicates that the ISGMR response begins to show softness in the molybdenum isotopes beginning with $A=92$.Comment: Accepted for publication to Physics Letters

Search for 22^{22}Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of $^{26}$Al and $^{22}$Na. While gamma rays from the decay of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na remains untraceable. The half-life of $^{22}$Na (2.6 yr) would allow the observation of its 1.275 MeV gamma-ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of the nuclear reactions involved in the production and destruction of this nucleus. The $^{22}$Na($p,\gamma$)$^{23}$Mg reaction remains the only source of large uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in $^{23}$Mg. In the present work, a combined analysis of particle-particle correlations and velocity-difference profiles is proposed to measure femtosecond nuclear lifetimes. The application of this novel method to the study of the $^{23}$Mg states, combining magnetic and highly-segmented tracking gamma-ray spectrometers, places strong limits on the amount of $^{22}$Na produced in novae, explains its non-observation to date in gamma rays (flux < 2.5x$10^{-4}$ ph/(cm$^2$s)), and constrains its detectability with future space-borne observatories.Comment: 18 pages, 3 figures, 1 tabl

Milne problem for non-absorbing medium with extremely anisotropic scattering kernel in the case of specular and diffuse reflecting boundaries

WOS:000423107300010The Milne problem is studied in one speed neutron transport theory using the linearly anisotropic scattering kernel which combines forward and backward scatterings (extremely anisotropic scattering) for a non-absorbing medium with specular and diffuse reflection boundary conditions. In order to calculate the extrapolated endpoint for the Milne problem, Legendre polynomial approximation (P-N method) is applied and numerical results are tabulated for selected cases as a function of different degrees of anisotropic scattering. Finally, some results are discussed and compared with the existing results in literature

Compression coated ornidazole tablets for colon specific drug delivery: Development, in vitro evaluation and optimisation by artificial neural network

The objective of the present study is to develop, evaluate and optimize colon targeted tablets of ornidazole. For this aim, the core tablets containing ornidazole were compression coated with different polymer mixtures and subjected to quality control studies. Thereafter, swelling, erosion and dissolution studies were performed under conditions mimicking mouth to colon transit. The results of in vitro studies showed that all of the compression coated tablet formulations prevented the drug release in mimicking conditions of stomach and small intestine. On the other hand, only the tablets that were compression coated with pectin and ethyl cellulose (EC) mixtures provided high ratio of drug release (up to 96%) during 24 h in colonic medium. Thereafter, the release kinetics of all formulations were investigated according to zero order kinetic model and the highest r2 value (0.967) was found to belong the formulation compression coated with 80% pectin and 20% EC N10 mixture. Finally, the large amount of in vitro experimental data obtained in this study was evaluated with artificial neural network (ANN) programme to optimize the best-fit formulation. The results obtained from ANN studies were similar with in vitro evaluation results but they were more accurate. According to ANN evaluation, tablets compression coated with 79.024% pectin and 20.976% EC N10 mixture was found to be the most likely formulation to provide targeting ornidazole for local action in the colon. © 2015, Colegio de Farmaceuticos de la Provincia de Buenos Aires. All rights reserved

Modified F N solution of the neutron transport equation for the Milne problem with FBIS kernel

The solution of the Milne problem is studied by one-speed neutron transport equation in plane geometry with İnönü’s scattering kernel, which is known as a linear combination of the forward, backward and isotropic scattering kernel (FBIS kernel). The solution of the neutron transport equation with İnönü’s scattering kernel can be written in terms of the solution of the neutron transport equation for isotropic scattering case. The extrapolation distance is calculated with modified FN (or HN) method. The numerical values of the extrapolation distance are obtained depending on the secondary neutron numbers and anisotropy coefficients and compared with the available data in the literature values

Nanovesicles for tumor-targeted drug delivery

Cancer is one of the most important burdens for the health systems worldwide due to cancer-related deaths associated with late diagnosis and treatment toxicities. Diagnosis of cancer plays a critical role in reducing cancer death rates as it facilitates early prognosis and treatment. Current cancer treatment mainly includes the resection of tumor tissue, radiation treatment, and pharmaceutical treatment. Although various techniques, methods, and drugs are clinically used in cancer diagnosis and treatment, they are inadequate for early diagnosis and effective treatment. Therefore, several studies regarding cancer-targeted nanosized drug delivery systems and theranostic approach are performed. Nanovesicular systems, one of the most important types of drug delivery systems, are formulated for the effective delivery and controlled release of active compounds such as drugs, genes, phytocompounds, and imaging agents. In this chapter, different types of nanovesicles are reviewed after providing information about conventional cancer imaging and treatment. Furthermore, targeting mechanisms of nanovesicles for cancer are explained. Finally, some studies performed to develop the nanovesicles as the imaging, treatment, or theranostic system for cancer are summarized. © 2022 Elsevier Inc. All rights reserved