APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

Risk factors for intrauterine growth retardation: results of a community-based study from Karachi

There is a serious lack of community-based information on low birthweight or intrauterine growth retardation from Pakistan. A community based prospective study was conducted in four squatter settlements of Karachi, to examine the prevalence and risk factors for adverse pregnancy outcome. This paper reports on the prevalence and risk factors for intrauterine growth retardation (age) among 755 singleton births. The incidence of intrauterine growth retardation was 25.4% (192 intrauterine growth retarded and 563 appropriate for gestational age). Major socioeconomic risk factors identified were low maternal education (RR = 1.4, 95% CI = 1.0,2.1) and poor housing material (RR = 1.7, 95% CI = 1.0,3.0). Among the significant biologic factors, primiparity (RR = 1.9, 95% CI = 1.4,2.7), consanguinity (RR = 1.4, 95% CI = 1.4,2.7), consanguinity (RR = 1.4, 95% CI = 1.1,1.8), short birth to CI = 1.1,2.1), short stature (RR = 2.2, 95% CI = 1.6,3.0), low maternal weight (RR = 2.0, 95% CI = 1.6,2.5) and non-vegetarian diet (RR = 2.3, 95% CI = 1.3,4.2) were especially important. Investigations to assess the adverse mortality and morbidity effects of intrauterine growth retardation are ongoing

Prevalence of potential underlying aetiology of macrocytic anaemia in Dutch general practice

Background: Macrocytic anaemia (MCV \xe2\x89\xa5 100 fL) is a relatively common finding in general practice. However, literature on the prevalence of the different causes in this population is limited. The prevalence of macrocytic anaemia and its underlying aetiology were analysed in a general practice population. The potential effect of the different aetiology on survival was also evaluated. Methods: Between the 1st of February 2007 and the 1st of February 2015, patients aged 50 years or older and presenting to their general practitioner with a newly diagnosed anaemia, were included in the study. Anaemia was defined as haemoglobin level below 13.7 g/dL in men and below 12.1 g/dL in women. A broad range of laboratory tests was performed for each patient. The causes of anaemia were consequently determined by two independent observers based on the laboratory results. Results: Of the 3324 included patients, 249 (7.5 %) displayed a macrocytic anaemia and were subsequently analysed. An underlying explanation could be established in 204 patients (81.9 %) with 27 patients (13.2 %) displaying multiple causes. Classic aetiology (i.e. alcohol abuse, vitamin B12/folic acid deficiency, haemolysis and possible bone marrow disease) was found in 115 patients. Alternative causes (i.e. anaemia of chronic disease, iron deficiency, renal anaemia and other causes) were encountered in 101 patients. In addition, a notable finding was the median gamma GT of 277 U/L in patients diagnosed with alcohol abuse (N = 24, IQR 118.0-925.5) and 23 U/L in the remaining cohort (N = 138, IQR 14.0-61.0). The distribution of gamma GT values was statistically different (P < 0.001). Five year survival rates were determined for six categories of causes, ranging from 39.9 % (95 % CI 12.9-66.9) for renal anaemia to 76.2 % (95 % CI 49.4-103.0) for the category multiple causes. Conclusion: In addition to classic explanations for macrocytosis, alternative causes are frequently encountered in patients with macrocytic anaemia in general practice