Towards a single-photon energy-sensitive pixel readout chip: pixel level ADCs and digital readout circuitry

Unlike conventional CMOS imaging, a single\ud photon imager detects each individual photon impinging on\ud a detector, accumulating the number of photons during a\ud certain time window and not the charge generated by the all\ud the photons hitting the detector during said time window.\ud The latest developments in the semiconductor industry\ud are allowing faster and more complex chips to be designed\ud and manufactured. With these developments in mind we are\ud working towards the next step in single photon X-ray imaging:\ud energy sensitive pixel readout chips. The goal is not only\ud to detect and count individual photons, but also to measure\ud the charge deposited in the detector by each photon, and\ud consequently determine its energy. Basically, we are aiming\ud at a spectrometer-in-a-pixel, or a “color X-ray camera”.\ud The approach we have followed towards this goal is the\ud design of small analog-to-digital-converters at the pixel level,\ud together with a very fast digital readout from the pixels to\ud the periphery of the chip, where the data will be transmitted\ud off-chip.\ud We will present here the design and measurement on prototype\ud chips of two different 4-bit pixel level ADCs. The\ud ADCs are optimized for very small area and low power, with\ud a resolution of 4-bits and a sample rate of 1 Msample/s. The\ud readout architecture is based around current-mode sense\ud amplifiers and asynchronous token-passing between the pixels.\ud This is done in order to achieve event-by-event readout\ud and, consequently, on-line imaging. We need to read eventby-\ud event (photon-by-photon), because we cannot have memory\ud on the pixels due to obvious size constraints. We use\ud current-mode sense amplifiers because they perform very\ud well in similar applications as very fast static-RAM readout

Venezuela’s Growth Experience

The standard of living, measured as gross domestic product (GDP) per capita, increased dramatically in Venezuela relative to that of the United States from 20 percent in 1920 to 90 percent in 1958, but since then has collapsed to around 30 percent nowadays. What explains these remarkable growth and collapse episodes? Using a standard development accounting framework, we show that the growth episode is mainly accounted for by an increase in capital accumulation and knowledge transfer associated with the foreign direct investment in the booming oil industry. The collapse episode is accounted for equally by a fall in total factor productivity and in capital accumulation. We analyze Venezuela during the collapse episode in the context of a model of heterogeneous production units were policies and institutions favour unproductive in detriment of more productive activities. These policies generate misallocation, lower TFP, and a decline in capital accumulation. We show in the context of an heterogeneous-establishment growth model that distortionary policies can explain a large portion of the current differences in TFP, capital accumulation, and income per capita between Venezuela and the United States.Productivity, physical capital, misallocation, policies

Venezuela's Growth Experience

The standard of living, measured as gross domestic product (GDP) per capita, increased dramatically in Venezuela relative to that of the United States from 20 percent in 1920 to 90 percent in 1958, but since then has collapsed to around 30 percent nowadays. What explains these remarkable growth and collapse episodes? Using a standard development accounting framework, we show that the growth episode is mainly accounted for by an increase in capital accumulation and knowledge transfer associated with the foreign direct investment in the booming oil industry. The collapse episode is accounted for equally by a fall in total factor productivity and in capital accumulation. We analyze Venezuela during the collapse episode in the context of a model of heterogeneous production units were policies and institutions favour unproductive in detriment of more productive activities. These policies generate misallocation, lower TFP, and a decline in capital accumulation. We show in the context of an heterogeneous-establishment growth model that distortionary policies can explain between 80 to 95 percent of the current differences in TFP, capital accumulation, and income per capita between Venezuela and the United States.Productivity, physical capital, misallocation, policies

Enhancing Environmental Staff Cleaning Process and Adenosine Triphosphate (ATP)

Clostridium difficile (C. difficile) has become the most common microbial cause of healthcareassociated infections (HAI) in U.S. hospitals and costs billions of dollars each year in excess of health care costs for acute care facilities alone (Centers for Disease Control and Prevention [CDC], 2015, para. 2). Inadequate cleaning of contaminated surfaces in the hospital environment may lead to an HAI. Potential barriers related to environmental cleaning of C. difficile infected rooms were identified at a small safety net hospital. The investigator used a convenience sample of 12 environmental staff (EVS) and a quasi-experimental pre-posttest design, to explore whether or not an educational intervention with EVS on a new cleaning process and Adenosine triphosphate (ATP) testing would improve environmental staff understanding of the cleaning process, as well as decrease the incidence of C. difficile HAI. Overall, the study supported the use of an educational intervention to improve cleaning efficacy with statistically significant results from the EVS staff educational pre-posttest (t= -2.680, p=.021) and pre-post ATP tests (t=12.520, p=.000). The study site’s C. difficile incidence rates changed from 3.76 to 1.86. The major limitation of this study was the small sample size. The most significant implication of this study is the investigator plans to continue implementing the new cleaning process with follow-up ATP testing, as well as conduct future research to assess other possible risk factors for C. difficile HAI

Dynamic Output State Classification for Quantum Computers

Quantum computers promise a potentially disruptive approach to improving computation in fields such as physics, chemistry, cryptography, optimisation, and machine learning. However, testing quantum computations for faults is currently impractical because of the existence of noise and errors associated with the output. Executing in a quantum system a circuit with only a few valid output states can generate a significant number of implausible states that have zero probability in an ideal computation. Among other sources of noise, readout errors come from the difficulty of discriminating a measurement between 0 and 1 for the different qubits. These issues are affected by readout drift, requiring regular recalibration of the process. In this paper, we provide a novel technique for post-computation analysis of the output probability distributions that permits better discrimination of kerneled data, delaying the need for recalibration. We achieve this by altering the linear discrimination of the final output states by way of a dynamic state selection process that combines Gaussian mixture models with a probability threshold. As an initial assessment of the technique we examine its effect on three to five qubits GHZ states. Our results on almost every one of nine IBM quantum computers show that the number of implausible states is reduced significantly and that the resulting probability distribution is closer to the expected one

A Megacam Survey of Outer Halo Satellites. IV. Two foreground populations possibly associated with the Monoceros substructure in the direction of NGC2419 and Koposov2

The origin of the Galactic halo stellar structure known as the Monoceros ring is still under debate. In this work, we study that halo substructure using deep CFHT wide-field photometry obtained for the globular clusters NGC2419 and Koposov2, where the presence of Monoceros becomes significant because of their coincident projected position. Using Sloan Digital Sky Survey photometry and spectroscopy in the area surrounding these globulars and beyond, where the same Monoceros population is detected, we conclude that a second feature, not likely to be associated with Milky Way disk stars along the line-of-sight, is present as foreground population. Our analysis suggests that the Monoceros ring might be composed of an old stellar population of age t ~ 9Gyr and a new component ~ 4Gyr younger at the same heliocentric distance. Alternatively, this detection might be associated with a second wrap of Monoceros in that direction of the sky and also indicate a metallicity spread in the ring. The detection of such a low-density feature in other sections of this halo substructure will shed light on its nature.Comment: 10 pages, 10 figures, accepted for publication in Ap