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

Anomalously large capacitance of a plane capacitor with a two-dimensional electron gas

In electronic devices where a two-dimensional electron gas (2DEG) comprises one or both sides of a plane capacitor, the resulting capacitance $C$ can be larger than the "geometric capacitance" $C_g$ determined by the physical separation $d$ between electrodes. This larger capacitance is known to result from the Coulomb correlations between individual electrons within the low density 2DEG, which lead to a negative thermodynamic density of states (negative compressibility). Experiments on such systems generally operate in the regime where the average spacing between electrons $n^{-1/2}$ in the 2DEG is smaller than $d$, and these experiments observe $C > C_g$ by only a few percent. A recent experiment [1], however, has observed $C$ larger than $C_g$ by almost 40% while operating in the regime $nd^2 << 1$. In this paper we argue that at $nd^2 << 1$ correlations between the electronic charge of opposite electrodes become important. We develop a theory of the capacitance for the full range of $nd^2$. We show that, in the absence of disorder, the capacitance can be $4d/a$ times larger than the geometric value, where $a << d$ is the electron Bohr radius. Our results compare favorably with the experiment of Ref. [1] without the use of adjustable parameters.Comment: 8 pages, 6 figures; revised discussion of the zero density limit; some typos fixe

Method for the recovery of Cr and Co species from effluents using agricultural adsorbent – immobilized E. coli, S. aureus and S. typhi isolates and FAAS detection

Microbial chromium and cobalt reduction was investigated for application in their recovery from industrial wastewater using flame atomic absorption technique. This paper presents the development of a routine method for the recovery of Cr and Co species in microbial-treated industrial wastewater using agricultural adsorbents and silica gel. E. coli, S. typhi and S. aureus were used in reducing these heavy metals. Results indicate that the palm kernel shell charcoal exhibited a good recovery capacity in the presence of the bacterial strains. Recovery rates of Cr in the activated charcoal and a bacterial optimum growth at pH 7.2 – 7.4 and 37 °C are 99.72% (S. typhi), 99.61% (E. coli) and 99.64% (S. aureus), while that of silica gel are 98.08% (S. typhi), 98.79% (E. coli) and 98.02% (S. aureus). The recovery of Co using the palm kernel shell charcoal is 99.71% (S. typhi), 99.58% (E. coli) and 99.60% (S. aureus). The results using the silica gel are 98.36% (S. typhi), 98.82% (E. coli) and 99.42% (S. aureus). In comparison to silica gel the palm kernel shell exhibited a higher recovery rate of Cr and Co in the presence of the bacterial strains.Keywords: Bacteria, adsorbent, heavy metal, wastewater, biosorption

Lymphocytes, apoptosis and sepsis: making the jump from mice to humans

Sepsis is an important clinical problem with a mortality rate of 20% to 30%. Lymphocyte apoptosis has been recognized as an important step in the pathogenesis of experimental sepsis, by inducing a state of 'immune paralysis' that renders the host vulnerable to invading pathogens. The importance of lymphocyte apoptosis in human disease is now confirmed by Weber and colleagues, who demonstrate extensive apoptosis in circulating lymphocytes from patients with severe sepsis. Weber and colleagues' data set the basis for further studies aimed at modulating lymphocyte apoptosis in sepsis

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