Detectors for the Gamma-Ray Resonant Absorption (GRA) Method of Explosives Detection in Cargo: A Comparative Study

Gamma-Ray Resonant Absorption (GRA) is an automatic-decision radiographic screening technique that combines high radiation penetration with very good sensitivity and specificity to nitrogenous explosives. The method is particularly well-suited to inspection of large, massive objects (since the incident gamma-ray probe is at 9.17 MeV) such as aviation and marine containers, heavy vehicles and railroad cars. Two kinds of gamma-ray detectors have been employed to date in GRA systems: 1) Resonant-response nitrogen-rich liquid scintillators and 2) BGO detectors. This paper analyses and compares the response of these detector-types to the resonant radiation, in terms of single-pixel figures of merit. The latter are sensitive not only to detector response, but also to accelerator-beam quality, via the properties of the nuclear reaction that produces the resonant gamma-rays. Generally, resonant detectors give rise to much higher nitrogen-contrast sensitivity in the radiographic image than their non-resonant detector counterparts and furthermore, do not require proton beams of high energy-resolution. By comparison, the non-resonant detectors have higher gamma-detection efficiency, but their contrast sensitivity is very sensitive to the quality of the accelerator beam. Implications of these detector/accelerator characteristics for eventual GRA field systems are discussed.Comment: 11 page

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

The Changing Face of Renal-Cell Carcinoma

The present decade can be credited with the improved understanding of renal-cell carcinoma (RCC), its local and systemic management, and various controversies from diagnosis to types of various available interventions. The old paradigms and dogmas are no longer accepted as “the best way” without evidence, and many “old” principles are cautiously questioned. These notions have resulted in new knowledge, questions, arguments, and treatment options. This article will describe the “changing face of RCC” over the past several years and will briefly summarize the major changes and issues in the field of renal oncology. The discussed topics include improved molecular understanding of RCC, management of small renal masses, the safety and accuracy of renal mass biopsy, the emerging role of molecular imaging, the importance of maximal renal preservation, and the evolving role of laparoscopy, robotics, and ablation

The Saga of Water and Halide Perovskites: Evidence of Water in Methylammonium Lead Tri‐Iodide

International audienceThe environment humidity effects on performance of halide perovskites (HaPs), especially MAPbI 3 , are known. Nevertheless, it is hard to find direct experimental evidence of H 2 O in the bulk materials at the levels lower than that of Monohydrate (MAPbI 3 .H 2 O). Here, for the first time, direct experimental evidence of water being released from bulk (µm-s deep) of MAPbI 3 single crystal is reported. The thermogravimetric analysis coupled with mass spectrometry (TGA-MS) of evolved gases is used to detect the MS signal of H 2 O from the penetrable depth and correlate it with the TGA mass loss due to H 2 O leaving the material. These measurements yield an estimate of the average H 2 O content of 1 H 2 O molecule per three MAPbI 3 formula units (MAPbI 3 .0.33H 2 O). Under the relatively low temperature conditions no other evolved gases that can correspond to MAPbI 3 decomposition products, are observed in the MS. In addition to being direct evidence that there is H 2 O inside MAPbI 3 , the data show that H 2 O diffuses into it. With this article, a solid basis is proved for further studies on the mechanisms through which water modifies the properties of MAPbI 3 and all the other halide perovskites

Dynamics of the Earth's particle radiation environment

The physical processes affecting the dynamics of the Earth's particle radiation environment are reviewed along with scientific and engineering models developed for its description. The emphasis is on models that are either operational engineering models or models presently under development for this purpose. Three components of the radiation environment, i.e., galactic cosmic rays (GCRs), solar energetic particles (SEPs) and trapped radiation, are considered separately. In the case of SEP models, we make a distinction between statistical flux/fluence models and those aimed at forecasting events. Models of the effects of particle radiation on the atmosphere are also reviewed. Further, we summarize the main features of the models and discuss the main outstanding issues concerning the models and their possible use in operational space weather forecasting. We emphasize the need for continuing the development of physics-based models of the Earth's particle radiation environment, and their validation with observational data, until the models are ready to be used for nowcasting and/or forecasting the dynamics of the environment