78 research outputs found
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Analysis of the EMCCD point-source response using x-rays
Electron Multiplying Charge Coupled Devices, EMCCD are used as x-ray detectors. The NSLS-II Soft Inelastic x-ray Scattering (SIX) beam line has two EMCCDs for x-ray detection in the spectrometer arm. The spectrometer with high resolving power disperses x-rays vertically. The x-ray vertical position on the sensor plane is related to its energy. This allows for very accurate x-ray energy measurements through x-ray coordinates. X-rays interact with silicon and create a number of electronâhole pairs proportional to the x-ray energy. Electrons drift and diffuse toward pixel gates and are collected there. The diffused electrons form a charge cloud distributed over several neighboring pixels. This charge sharing enables coordinate measurements with accuracy better than the pixel pitch. The charge distribution shape has to be taken into account to achieve ultimate accuracy in coordinate measurements. In this paper, we present a method of the charge distribution shape analysis and demonstrate its applications.
The drift and diffusion of electrons from the point of generation to pixel gates results in the bell-shaped electron cloud usually approximated by Gaussian shape. The number of electrons collected under a pixel is proportional to the shape function integral. These electron packets get transferred to the sense node of the output amplifier. The transfer process could introduce distortions to the original charge distribution. For example, during transfers, electrons in the packet could be exposed to traps if they are present in the sensor. The trapping and later the release processes distort the apparent shape of the charge distribution. Therefore, deviations of the charge distribution shape from the originally symmetrical form can indicate the presence of trap centers in the sensor and can be used for sensor diagnostics
Preclinical Evaluation of a Lentiviral Vector for Huntingtin Silencing.
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder resulting from a polyglutamine expansion in the huntingtin (HTT) protein. There is currently no cure for this disease, but recent studies suggest that RNAi to downregulate the expression of both normal and mutant HTT is a promising therapeutic approach. We previously developed a small hairpin RNA (shRNA), vectorized in an HIV-1-derived lentiviral vector (LV), that reduced pathology in an HD rodent model. Here, we modified this vector for preclinical development by using a tat-independent third-generation LV (pCCL) backbone and removing the original reporter genes. We demonstrate that this novel vector efficiently downregulated HTT expression in vitro in striatal neurons derived from induced pluripotent stem cells (iPSCs) of HD patients. It reduced two major pathological HD hallmarks while triggering a minimal inflammatory response, up to 6 weeks after injection, when administered by stereotaxic surgery in the striatum of an in vivo rodent HD model. Further assessment of this shRNA vector in vitro showed proper processing by the endogenous silencing machinery, and we analyzed gene expression changes to identify potential off-targets. These preclinical data suggest that this new shRNA vector fulfills primary biosafety and efficiency requirements for further development in the clinic as a cure for HD
Itinerant effects and enhanced magnetic interactions in Bi-based multilayer cuprates
The cuprate high temperature superconductors exhibit a pronounced trend in which the superconducting transition temperature Tc increases with the number of CuO2 planes n in the crystal structure. We compare the magnetic excitation spectrum of Bi2+xSr2âxCuO6+ÎŽ (Bi-2201) and Bi2Sr2Ca2Cu3O10+ÎŽ (Bi-2223), with n = 1 and 3, respectively, using Cu L3-edge resonant inelastic x-ray scattering. Near the antinodal zone boundary we find the paramagnon energy in Bi-2223 is substantially higher than that in Bi-2201, indicating that multilayer cuprates host stronger effective magnetic exchange interactions, providing a possible explanation for the Tc vs n scaling. In contrast, the nodal direction exhibits very strongly damped, almost nondispersive excitations. We argue that this implies that the magnetism in the doped cuprates is partially itinerant in nature
Excitonic Instability in the Transition from the Black Phase to the Golden Phase of SmS under Pressure Investigated by Infrared Spectroscopy
We report the pressure-dependent optical reflectivity spectra of a strongly
correlated insulator, samarium monosulfide (SmS), in the far- and
middle-infrared regions to investigate the origin of the pressure-induced phase
transition from the black phase to the golden phase. The energy gap becomes
narrow with increasing pressure in the black phase. A valence transition from
Sm2+ in the black phase to mainly Sm3+ in the golden phase accompanied by
spectral change from insulator to metal were observed at the transition
pressure of 0.65 GPa. The black-to-golden phase transition occurs when the
energy gap size of black SmS becomes the same as the binding energy of the
exciton at the indirect energy gap before the gap closes. This result indicates
that the valence transition originates from an excitonic instability.Comment: 5 pages, 4 figures. To be published in J. Phys. Soc. Jpn. Vol. 77,
No. 1
Changing the prehistory of Sindh and Las Bela coast: twenty-five years of Italian contribution
The paper discusses the prehistory of Lowr Sindh and Las Bela Coast, and the role played by the Italian archaeologists since the 1980's. New date are presented regarding mainly the radiocarbon chronology the Indus Delta settlement on rocky outcrops and the shell middens of Las Bela
Manquements au droit Ă lâinformation du sujet ĂągĂ© cognitivement dĂ©pendant
International audienceRĂ©sumĂ© Les auteurs rappellent quâun des droits fondamentaux du sujet ĂągĂ© cognitivement dĂ©pendant est celui dâĂȘtre informĂ© clairement de ce qui le concerne (santĂ©, finances, entourage) mais ce droit peut ĂȘtre aisĂ©ment mĂ©connu. Ceci relĂšve sans doute dâintentions altruistes (Ă©viter des souffrances) mais ne prend guĂšre en compte les effets dĂ©lĂ©tĂšres occasionnĂ©s dĂšs lors que le sujet nâest plus considĂ©rĂ© comme acteur de sa propre vie. Ainsi nous pouvons considĂ©rer trois exemples de situations courantes de mĂ©sinformation du sujet ĂągĂ© cognitivementdĂ©pendant : lâannonce du diagnostic de maladie neurocognitive et notamment de maladie dâAlzheimer (annonce partielle ou au seul profit de lâentourage) ; lâabsence dâannonce du dĂ©cĂšs dâun proche (enfant-conjoint) dĂšs lors que le sujet ĂągĂ© prĂ©sente une altĂ©ration cognitive patente ; le manque de clartĂ© dans lâannonce de lâinstitutionnalisation. Cet exposĂ© nâa pas vocation Ă juger des comportements soignants, mĂ©dicaux ou dâaidants mais Ă tĂ©moigner des limites dâun systĂšme de prise en soin, marquĂ© par le manque, sinon lâabsence, de contrĂŽlesjuridiques concernant notamment lâinstitutionnalisation
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