Breaking the Buildup-time Limit of sensitivity in Avalanche Photodiodes by Dynamic Biasing

Avalanche photodiodes (APDs) are the preferred photodetectors for direct-detection, high data-rate long-haul optical telecommunications. APDs can detect low-level optical signals due to their internal amplification of the photon-generated electrical current, which is attributable to the avalanche of electron and hole impact ionizations. Despite recent advances in APDs aimed at reducing the average avalanche-buildup time, which causes intersymbol interference and compromises receiver sensitivity at high data rates, operable speeds of commercially available APDs have been limited to 10Gbps. We report the first demonstration of a dynamically biased APD that breaks the traditional sensitivity-versus-speed limit by employing a data-synchronous sinusoidal reverse-bias that drastically suppresses the average avalanche-buildup time. Compared with traditional DC biasing, the sensitivity of germanium APDs at 3Gbps is improved by 4.3 dB, which is equivalent to a 3,500-fold reduction in the bit-error rate. The method is APD-type agnostic and it promises to enable operation at rates of 25Gbps and beyond

A Protocol for Retrospective Remote Sensing-Based Ecological Monitoring of Rangelands

The degree of rangeland degradation in the United States is unknown due to the failure of traditional field-based monitoring to capture the range of variability of ecological indicators and disturbances, including climatic effects and land use practices, at regional to national spatial scales, and temporal scales of decades. Here, a protocol is presented for retrospective monitoring and assessment of rangeland degradation using historical time series of remote sensing data and catastrophe theory as an ecological framework to account for both gradual and rapid changes of state. This protocol 1) justifies the use of time-series satellite imagery in terms of the spatial and temporal scale of data collection; 2) briefly explains how to acquire, process, and transform the data into ecological indicators; 3) discusses the use of time-series analysis as the appropriate procedure for detecting significant change; and 4) explains what reference conditions are appropriate. Landsat data have been collected and archived since 1972, and include complete coverage of US rangelands. Characteristics of land degradation can be retrospectively measured for a nearly 33-year trend using surrogate remote sensing-based indicators that correlate with changes in life-form composition (time series of thematic maps), declines in vegetation productivity (vegetation indices), accelerated soil erosion (soil indices), declines in soil quality (piospheric analysis), and changes in landscape configuration (time series of thematic maps). Aspects of 2 retrospective studies are presented as examples of application of the protocol to considerations of the land use impacts from military training and testing and ranching activities on rangelands. The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_jrm_v59i1_alle

Cigarette smoking is negatively associated with family average income among urban and rural men in regional Mainland China

Socio-economic status (SES) has a strong influence on cigarette smoking behaviour. However, as a more sensitive and realistic index of SES, family average income (FAI) has little studied regarding its association with smoking. With a response rate of 90.1%, a cross-sectional study was conducted among randomly selected urban-rural participants (n&thinsp; =&thinsp;29,353) between October of 2000 and March of 2001 in Nanjing, China. The proportion of male participants who were current smokers was 54.7%; for females it was 2.2%. After adjustment for possible confounding variables (area of residence, age, education, occupation) males in the middle (OR 0.76; 95% CI 0.69&ndash;0.84) and higher (OR 0.64; 95% CI 0.57&ndash;0.71) FAI tertiles had lower odds of being smokers than did males in the lower FAI tertile. There were no differences by FAI category in the odds of being an ex-smoker. Therefore, current smoking among adult males is inversely associated with family average income in a regional Chinese population. FAI may inform the targeting of campaigns or other initiatives, particularly in populations where material prosperity is low in some social groups.<br /