High spatial resolution inorganic scintillator detector for high energy X-ray beam at small field irradiation

International audiencePurpose: Small fielddosimetry for radiotherapy is one of the major challenges due to the size of most dosimeters,e.g. sufficient spatial resolution, accurate dose distribution and energy dependency of the detector. In this context, the purpose of this research is to develop a small size scintillating detector targeting small field dosimetry and compare its performance with other commercial detectors. Method: An inorganic scintillator detector (ISD) of about 200 μm outer diameter was developed and tested through different small fields dosimetric characterization under high energy photons (6 MV and 15 MV) delivered by an Elekta Linear Accelerator (LINAC). PDD and beam profile measurements were compared using dosimeters from PTW namely, microdiamond and PinPoint 3D detector. A background fiber method has been considered to quantifyand eliminate the minimal Cerenkov effect from the total optical signal magnitude. Measurements were performed inside a water phantom under IAEA Technical reports series recommendations (IAEA TRS 381 and TRS 483). Results:Small fields ranging from 3 x 3 cm2, down to 0.5 x 0.5 cm2 were sequentiallymeasured using the ISD and commercial dosimeters, and a good agreement was obtained among all measurements. The result also shows that, scintillating detector has good repeatabilityand reproducibility of the output signal with maximum deviation of 0.26% and 0.5% respectively. The Full Width Half Maximum (FWHM) was measured 0.55 cm for the smallest available square size field of 0.5 x 0.5 cm2, where the discrepancy of 0.05 cm is dueto the scattering effects inside the water and convolution effect between field and detector geometries. Percentage Depth Dose (PDD) factor dependence variation with water depth exhibits nearly the same behavior for all tested detectors. The ISD allows to perform dose measurements at a very high accuracy from low (50 cGy/min) to high dose rates (800 cGy/min) and found to be independent of dose rate variation. The detection system also showed an excellent linearity with dose; hence calibration was easily achieved. Conclusions: The developed detector can be used to accurately measure the delivered dose at small field during the treatment of small volume tumors. The author’s measurement shows that despite using a non-water equivalent detector, the detector can be a powerful candidate for beam characterization and quality assurance in e.g., radiosurgery, Intensity Modulated Radiotherapy (IMRT), and brachytherapy. Our detector can provide real-time dose measurement and good spatial resolution with immediate readout, simplicity, flexibility, and robustness

Combining scanning probe microscopy and x-ray spectroscopy

A new versatile tool, combining Shear Force Microscopy and X-Ray Spectroscopy was designed and constructed to obtain simultaneously surface topography and chemical mapping. Using a sharp optical fiber as microscope probe, it is possible to collect locally the visible luminescence of the sample. Results of tests on ZnO and on ZnWO4 thin layers are in perfect agreement with that obtained with other conventional techniques. Twin images obtained by simultaneous acquisition in near field of surface topography and of local visible light emitted by the sample under X-Ray irradiation in synchrotron environment are shown. Replacing the optical fibre by an X-ray capillary, it is possible to collect local X-ray fluorescence of the sample. Preliminary results on Co-Ti sample analysis are presented

A experiência e os resultados do Núcleo Piloto de Informação e Gestão Tecnológica para a Agricultura Familiar do Território do Sisal no Sertão da Bahia.

Introdução. Território do Sisal: um território da pecuária. Demanda em tecnologia e o dispositivo de apoio tecnológico. Principais experiências e resultados da Embrapa e seus parceiros. Difusão e promoção de tecnologia. Apoio a gestão do agronegócio associativo e inovativo. Agência de informação.bitstream/item/201355/1/A-experiencia-e-os-resultados-do-Nucleo-Piloto-de-Informacao-e-Gestao-Tecnologica-para-aAgricultura-Familiar-do-Territorio-do-Sisalno-sertao-da-Bahia.pd

Predictive coding and representationalism

According to the predictive coding theory of cognition (PCT), brains are predictive machines that use perception and action to minimize prediction error, i.e. the discrepancy between bottom–up, externally-generated sensory signals and top–down, internally-generated sensory predictions. Many consider PCT to have an explanatory scope that is unparalleled in contemporary cognitive science and see in it a framework that could potentially provide us with a unified account of cognition. It is also commonly assumed that PCT is a representational theory of sorts, in the sense that it postulates that our cognitive contact with the world is mediated by internal representations. However, the exact sense in which PCT is representational remains unclear; neither is it clear that it deserves such status—that is, whether it really invokes structures that are truly and nontrivially representational in nature. In the present article, I argue that the representational pretensions of PCT are completely justified. This is because the theory postulates cognitive structures—namely action-guiding, detachable, structural models that afford representational error detection—that play genuinely representational functions within the cognitive system

Integrative Annotation of 21,037 Human Genes Validated by Full-Length cDNA Clones

The human genome sequence defines our inherent biological potential; the realization of the biology encoded therein requires knowledge of the function of each gene. Currently, our knowledge in this area is still limited. Several lines of investigation have been used to elucidate the structure and function of the genes in the human genome. Even so, gene prediction remains a difficult task, as the varieties of transcripts of a gene may vary to a great extent. We thus performed an exhaustive integrative characterization of 41,118 full-length cDNAs that capture the gene transcripts as complete functional cassettes, providing an unequivocal report of structural and functional diversity at the gene level. Our international collaboration has validated 21,037 human gene candidates by analysis of high-quality full-length cDNA clones through curation using unified criteria. This led to the identification of 5,155 new gene candidates. It also manifested the most reliable way to control the quality of the cDNA clones. We have developed a human gene database, called the H-Invitational Database (H-InvDB; http://www.h-invitational.jp/). It provides the following: integrative annotation of human genes, description of gene structures, details of novel alternative splicing isoforms, non-protein-coding RNAs, functional domains, subcellular localizations, metabolic pathways, predictions of protein three-dimensional structure, mapping of known single nucleotide polymorphisms (SNPs), identification of polymorphic microsatellite repeats within human genes, and comparative results with mouse full-length cDNAs. The H-InvDB analysis has shown that up to 4% of the human genome sequence (National Center for Biotechnology Information build 34 assembly) may contain misassembled or missing regions. We found that 6.5% of the human gene candidates (1,377 loci) did not have a good protein-coding open reading frame, of which 296 loci are strong candidates for non-protein-coding RNA genes. In addition, among 72,027 uniquely mapped SNPs and insertions/deletions localized within human genes, 13,215 nonsynonymous SNPs, 315 nonsense SNPs, and 452 indels occurred in coding regions. Together with 25 polymorphic microsatellite repeats present in coding regions, they may alter protein structure, causing phenotypic effects or resulting in disease. The H-InvDB platform represents a substantial contribution to resources needed for the exploration of human biology and pathology

High aspect ratio nano-oxidation of Silicon with noncontact atomic force microscopy

International audienc

Signal amplification of fiber integrated X-ray detectors by metallization

International audienc