Ultra-high strength concrete produced with agro-residual wastes and industrial by-products were tested for radiation shielding capacity by measuring the linear attenuation coefficient, half value layer and tenth value layer. The linear attenuation test results, show that the ul- tra-high strength concrete with agro-residual and industrial wastes can be effectively employed in shielding the radiation. The half value layer results reveal that radiation shielding concretes can be produced using industrial and agro-residual wastes, by concentrating equally on the enhancement of both the homogeneity and density of the concrete matrix. The ultra-high strength concrete developed in this investigation registered a better radiation shielding properties than that of the conventional anti-radiation shielding concretes with high dense aggregates which are costlier and found to have environmental degradation along with the health hazards.
The materials characterization based on gamma measurements is one of the main features for verifying the radioactive materials for safeguards purposes. This work focuses on the optimization approach in order to find solutions that include some influence parameters, which should be taken into consideration during measurements. The considered samples in our work are certified reference nuclear materials of chemical composition (U3O8) with different enrichment ratios ranging from 0.31 wt.% to 4.46 wt.%. The gamma spectrometer based on a planar high-purity germanium detector of high-resolution was used in the current study. The study of various setups was experimentally carried out for different cans at different positions for different energy lines. The verified parameters influencing the characterization of the measured samples have been estimated. This approach for the measurement setup of the measured gamma spectra has been successfully explored to be very affected by different parameters such as the source to detector position and the various enrichment ratios. Consequently, the verified and characterized samples could be estimated based on this optimization approach.
Vladimir Lukic, Milica Spasojevic, Milentije Lukovic
et al.
Kinetics and mechanism of hydrogen adsorption in as-obtained and ground nuclear graphite Wendelstein 7-X are examined. In the first time interval the adsorption process is determined by dissociation of the hydrogen molecule, occurring at the outer surface and in open micropores of nuclear graphite particles. However, in the second time interval, the slowest step in the hydrogen adsorption is inter-granular and inter-crystallite diffusion in nanopores of graphite. The X-ray analysis shows, that grinding of as-obtained nuclear graphite results in finer particles with finer nanocrystals and larger density of opened pores and carbon reactive sites. The capacity and rate of adsorption increase with comminution of nuclear graphite particles and adsorbed hydrogen does not substantially alter the microstructure of nuclear graphite.
The objective of this study was to analyze the dependence of the neutron dose from the geometry of the second band of the maze using dosimetric measurements of neutrons and Monte Carlo simulations, and based on those results to design a novel radiotherapy room layout. Measurements of the neutron dose at a two-band maze therapy room were performed for a 15 MeV photon beam only. Monte Carlo simulations were performed using the GEANT4 toolkit. In order to obtain the geometry dependence, we were changing the second band angle while we kept the length, height, and width the same as in reality. Results show that the highest calculated dose was obtained for the 60? angle of the second maze. It is 17 % higher than for standard 0? angle. For 30? it was 30 % smaller and for 90? was 10% smaller. Although the lowest dose was obtained for 30? band angle with calculations, it is not very practical for clinical use. Clinically the most interesting would be the 90? angle which is practically a short three-band maze, which could be promising from the perspective of neutron radiation protection since it could offer a compact constructional solution, and better optimization of the available space.
Results of analyzes of the growth and development of species Pterocarya pterocarpa (Michx.) Kunth ex Iljinsk. of the Pterocarya Kunth genus (Juglandaceae DC. ex Perleb) — relict plant of the Arctic flora of the III period in ex situ conditions have been shown in the paper. Degree of adaptation of wingnut in ex situ conditions, its growth characteristics were assessed both in young and old age. The biomorphological structure of P. pterocarpa seedlings, the size and number of hypocotyls and germ layer were determined in the course of the study. The formation and growth of simple complex true leaves and the life cycle of germ layer were determined as a result of observations of seedlings. The growth of seedlings of wingnut occurs intensively from the third decade of April to the second decade of June under ex situ conditions have been showed the study. The final productivity of seedlings under in situ conditions was higher than under cultivation conditions in ex situ as was found under studying the growth and development of plant. The vegetation of the species P. pterocarpa under the conditions of Absheron begins from the second decade of March to the second decade of November; the duration of the growing season is several days. P. pterocarpa grows and develops normally in cultural conditions of Absheron on based of the analysis of the research.
In contrast to traditional static cold preservation of donor livers, normothermic machine perfusion may reduce preservation injury, improve graft viability and potentially allows ex vivo assessment of graft viability before transplantation. We have studied the feasibility of normothermic machine perfusion in four discarded human donor livers. Normothermic machine perfusion consisted of pressure and temperature controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion for 6 h. Two hollow fiber membrane oxygenators provided oxygenation of the perfusion fluid. Biochemical markers in the perfusion fluid reflected minimal hepatic injury and improving function. Lactate levels decreased to normal values, reflecting active metabolism by the liver (mean lactate 10.0 ± 2.3 mmol/L at 30 min to 2.3 ± 1.2 mmol/L at 6 h). Bile production was observed throughout the 6 h perfusion period (mean rate 8.16 ± 0.65 g/h after the first hour). Histological examination before and after 6 h of perfusion showed well‐preserved liver morphology without signs of additional hepatocellular ischemia, biliary injury or sinusoidal damage. In conclusion, this study shows that normothermic machine perfusion of human donor livers is technically feasible. It allows assessment of graft viability before transplantation, which opens new avenues for organ selection, therapeutic interventions and preconditioning.
MOPAC and LAMMPS molecular dynamics codes and reaction kinetics code based on multi-ionic continuum-based model are used to analyze the impact of gamma radiation on concrete hydration. The experimental studies showed that while cured with the low gamma dose concrete shows a statistically significant increase in its strength compared to conventionally cured concrete. The potential reason is the interactions of gamma rays with water causing concrete faster hydration. The question then to ask is would the higher gamma dose enhance the concrete curing further producing its higher strength. This paper provides in-depth numerical analyses of the high-dose gamma radiation effect on concrete based on molecular dynamics and reaction kinetics models. Under these conditions, it is assumed that gamma radiation interacting with water within the concrete induces water radiolysis. These numerical simulations show that the reactivity is generally increased in the presence of electrophiles. However, the early hydration models of tricalcium silicate (alite) and dicalcium silicate (belite) with H+, OH-, and H3O+ show that the hydration process is slowed down leading to a lower concrete strength. Additionally, the reaction kinetics model used to estimate the effect of [OH-] on tricalcium silicate hydration shows that an increase or decrease of [OH-] during tricalcium silicate hydration can respectively slow down or enhance its rate of hydration. The dose necessary to produce the water radiolysis resulting in varying [OH-] during tricalcium silicate hydration is required to be extremely high and therefore, will damage the concrete structure itself. This leads to the conclusion that increasing the gamma dose to concrete above that used in the experimental studies in order to induce water radiolysis will not improve concrete strength, therefore water radiolysis is not the required condition for improving concrete strength when cured under gamma radiation.
How does subatomic matter organize itself? Neutron stars are cosmic laboratories uniquely poised to answer this fundamental question that lies at the heart of nuclear science. Newly commissioned rare isotope facilities, telescopes operating across the entire electromagnetic spectrum, and ever more sensitive gravitational wave detectors will probe the properties of neutron-rich matter with unprecedented precision over an enormous range of densities. Yet, a coordinated effort between observation, experiment, and theoretical research is of paramount importance for realizing the full potential of these investments. Theoretical nuclear physics provides valuable insights into the properties of neutron-rich matter in regimes that are not presently accessible to experiment or observation. In particular, nuclear density functional theory is likely the only tractable framework that can bridge the entire nuclear landscape by connecting finite nuclei to neutron stars. This compelling connection is the main scope of the present review.
Azimuthal correlations between the same type of particles (protons or pions) in the target fragmentation region was studied in d, He, C + C, Ta (4.2 AGeV/c), C + Ne, Cu (4.5AGeV/c) and p + C, Ta (10 GeV/c) interactions. The data were obtained from the SKM-200-GIBS streamer chamber and from Propane Bubble Chamber (PBL-500) systems utilized at JINR. Study of multiparticle azimuthal correlations offers unique information about space-time evolution of the interactions. Azimuthal correlations were investigated by using correlation function C($Δφ$)=dN/d($Δφ$), where $Δφ$ represents the angle between the sums of transverse momenta vectors for particles emitted in the forward and backward hemispheres. For protons a "back-to back" ("negative") azimuthal correlations were observed in the above mentioned interactions. The absolute values of the correlation coefficient $|ξ|$ -- the slope parameter of C($Δφ$), strongly depend on the mass number of the target ($A_T$) nuclei in the nucleon-nucleus and nucleus-nucleus collisions. Namely, $|ξ|$ -- decreases with increase of $A_T$ in p+C and p+Ta collisions, while $|ξ|$ decreases from d+C up to C+Ne and then almost does not change with increase of $A_P$, $A_T$ in (d+He)Ta, C+Cu and C+Ta collisions. For pions a "back-to-back" correlations were obtained for a light targets (C, Ne), and a "side-by-side" ("positive") correlations for a heavy targets (Cu, Ta). The $|ξ|$ insignificantly changes with increase of the momenta per nucleon and almost does not change with increase of $A_P$ and $A_T$. Models, used for description of the data -- the Ultra relativistic Quantum Molecular Dynamic (UrQMD) and Quark-Gluon String Model (QGSM), satisfactorily describe the obtained experimental results.
Richard Sisson, Cameron Reinhart, Paul Bridgman
et al.
In order to combine niobium (Nb) with lanthanum (La) and cerium (Ce), Nb ions were deposited within a thin film of these two elements. According to the Hume-Rothery rules, these elements cannot be combined into a traditional crystalline metallic solid. The creation of an amorphous metallic glass consisting of Nb, La, and Ce is then investigated. Amorphous metallic glasses are traditionally made using fast cooling of a solution of molten metals. In this paper, we show the results of an experiment carried out to form a metallic glass by implanting 9 MeV Nb 3+ atoms into a thin film of La and Ce. Prior to implantation, the ion volume distribution is calculated by Monte Carlo simulation using the SRIM tool suite. Using multiple methods of electron microscopy and material characterization, small quantities of amorphous metallic glass are indeed identified.
Swarnapratim Bhattacharyya, Maria Haiduc, Alina Tania Neagu
et al.
A study of multiplicity distribution of singly charged, doubly charged, multi charged projectile fragments and shower particles have been carried out for the peripheral collisions in 16O-emulsion,22Ne-emulsion and 28Si-emulsion interactions at an incident momentum of (4.1-4.5) AGeV/c. Events having no target fragments have been designated as peripheral collision events. Percentage of peripheral events has been found to increase with the increase of projectile mass. Dispersion of the multiplicity distribution and its dependence on projectile mass for projectile fragments and shower particles has also been investigated. Dependence of average multiplicity of projectile fragments and shower particles on the mass of the projectile beam has been studied. Study of different fragmentation mode during the emission of multi charged projectile fragments has also been carried out.
Zhuo Shao, Mollie S H Friedlander, Christian G. Hurst
et al.
Angiogenesis of the microvasculature is central to the etiology of many diseases including proliferative retinopathy, age-related macular degeneration and cancer. A mouse model of microvascular angiogenesis would be very valuable and enable access to a wide range of genetically manipulated tissues that closely approximate small blood vessel growth in vivo. Vascular endothelial cells cultured in vitro are widely used, however, isolating pure vascular murine endothelial cells is technically challenging. A microvascular mouse explant model that is robust, quantitative and can be reproduced without difficulty would overcome these limitations. Here we characterized and optimized for reproducibility an organotypic microvascular angiogenesis mouse and rat model from the choroid, a microvascular bed in the posterior of eye. The choroidal tissues from C57BL/6J and 129S6/SvEvTac mice and Sprague Dawley rats were isolated and incubated in Matrigel. Vascular sprouting was comparable between choroid samples obtained from different animals of the same genetic background. The sprouting area, normalized to controls, was highly reproducible between independent experiments. We developed a semi-automated macro in ImageJ software to allow for more efficient quantification of sprouting area. Isolated choroid explants responded to manipulation of the external environment while maintaining the local interactions of endothelial cells with neighboring cells, including pericytes and macrophages as evidenced by immunohistochemistry and fluorescence-activated cell sorting (FACS) analysis. This reproducible ex vivo angiogenesis assay can be used to evaluate angiogenic potential of pharmacologic compounds on microvessels and can take advantage of genetically manipulated mouse tissue for microvascular disease research.