A Processor Extension for Cycle-Accurate Real-Time Software

Certain hard real-time tasks demand precise timing of events, but the usual software solution of periodic interrupts driving a scheduler only provides precision in the millisecond range. NOP-insertion can provide higher precision, but is tedious to do manually, requires predictable instruction timing, and works best with simple algorithms. To achieve high-precision timing in software, we propose instruction-level access to cycle-accurate timers. We add an instruction that waits for a timer to expire then reloads it synchronously. Among other things, this provides a way to exactly specify the period of a loop. To validate our approach, we implemented a simple RISC processor with our extension on an FPGA and programmed it to behave like a video controller and an asynchronous serial receiver. Both applications were much easier to write and debug than their hardware counterparts, which took roughly four times as many lines in VHDL. Simple processors with our extension brings software-style development to a class of applications that were once only possible with hardware

Post-Harvest Marketing Alternatives

4 pp.The marketing time frame for crops can be divided into three parts--pre-harvest, harvest and post-harvest. This publication focuses on the more common post-harvest marketing strategies using forward contracts, storage, futures contracts, options and various combinations of these tools

Use of a Closed-Loop Tracking Algorithm for Orientation Bias Determination of an S-Band Ground Station

The Space Communications and Navigation (SCaN) Testbed project completed installation and checkout testing of a new S-Band ground station at the NASA Glenn Research Center in Cleveland, Ohio in 2015. As with all ground stations, a key alignment process must be conducted to obtain offset angles in azimuth (AZ) and elevation (EL). In telescopes with AZ-EL gimbals, this is normally done with a two-star alignment process, where telescope-based pointing vectors are derived from catalogued locations with the AZ-EL bias angles derived from the pointing vector difference. For an antenna, the process is complicated without an optical asset. For the present study, the solution was to utilize the gimbal control algorithms closed-loop tracking capability to acquire the peak received power signal automatically from two distinct NASA Tracking and Data Relay Satellite (TDRS) spacecraft, without a human making the pointing adjustments. Briefly, the TDRS satellite acts as a simulated optical source and the alignment process proceeds exactly the same way as a one-star alignment. The data reduction process, which will be discussed in the paper, results in two bias angles which are retained for future pointing determination. Finally, the paper compares the test results and provides lessons learned from the activity

The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441

We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster. The red clump slopes nearly parallel to the reddening vector. A component of this slope is due to differential reddening, but part is intrinsic. The blue horizontal branch stars are more centrally concentrated than the red clump stars. We have discovered about 50 new variable stars near NGC 6441, among them eight or more RR Lyrae stars which are very probably cluster members. Comprehensive period searches over the range 0.2-1.0 days yielded unusually long periods (0.5-0.9 days) for the fundamental pulsators compared with field RR Lyrae of the same metallicity. Three similar long-period RR Lyrae are known in other metal-rich globulars. With over ten examples in hand, it seems that a distinct sub-class of RR Lyrae is emerging. The observed properties of the horizontal branch stars are in reasonable agreement with recent models which invoke deep mixing to enhance the atmospheric helium abundance, while they conflict with models which assume high initial helium abundance. The light curves of the c-type RR Lyrae seem to have unusually long rise times and sharp minima. Reproducing these light curves in stellar pulsation models may provide another means of constraining the physical variables responsible for the anomalous blue horizontal branch extension and sloped red clump observed in NGC 6441.Comment: 30 pages plus 6 EPS and 6 JPEG figures; uses AAS TeX. Accepted by the Astronomical Journal. Minor changes include computing He abundance, modifications to Figs 1 and 8, and expansion on idea that blue HB stars may be produced in binarie

Systematic review of the psychological consequences of false-positive screening mammograms

Background: In the UK, women aged 50-73 years are invited for screening by mammography every 3 years. In 2009-10, more than 2.24 million women in this age group in England were invited to take part in the programme, of whom 73% attended a screening clinic. Of these, 64,104 women were recalled for assessment. Of those recalled, 81% did not have breast cancer; these women are described as having a false-positive mammogram. Objective: The aim of this systematic review was to identify the psychological impact on women of false positive screening mammograms and any evidence for the effectiveness of interventions designed to reduce this impact. We were also looking for evidence of effects in subgroups of women. Data sources: MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, Health Management Information Consortium, Cochrane Central Register for Controlled Trials, Cochrane Database of Systematic Reviews, Centre for Reviews and Dissemination (CRD) Database of Abstracts of Reviews of Effects, CRD Health Technology Assessment (HTA), Cochrane Methodology, Web of Science, Science Citation Index, Social Sciences Citation Index, Conference Proceedings Citation Index-Science, Conference Proceeding Citation Index-Social Science and Humanities, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, Sociological Abstracts, the International Bibliography of the Social Sciences, the British Library's Electronic Table of Contents and others. Initial searches were carried out between 8 October 2010 and 25 January 2011. Update searches were carried out on 26 October 2011 and 23 March 2012. Review methods: Based on the inclusion criteria, titles and abstracts were screened independently by two reviewers. Retrieved papers were reviewed and selected using the same independent process. Data were extracted by one reviewer and checked by another. Each included study was assessed for risk of bias. Results: Eleven studies were found from 4423 titles and abstracts. Studies that used disease-specific measures found a negative psychological impact lasting up to 3 years. Distress increased with the level of invasiveness of the assessment procedure. Studies using instruments designed to detect clinical levels of morbidity did not find this effect. Women with false-positive mammograms were less likely to return for the next round of screening [relative risk (RR) 0.97; 95% confidence interval (CI) 0.96 to 0.98] than those with normal mammograms, were more likely to have interval cancer [odds ratio (OR) 3.19 (95% CI 2.34 to 4.35)] and were more likely to have cancer detected at the next screening round [OR 2.15 (95% CI 1.55 to 2.98)]. Limitations: This study was limited to UK research and by the robustness of the included studies, which frequently failed to report quality indicators, for example failure to consider the risk of bias or confounding, or failure to report participants' demographic characteristics. Conclusions: We conclude that the experience of having a false-positive screening mammogram can cause breast cancer-specific psychological distress that may endure for up to 3 years, and reduce the likelihood that women will return for their next round of mammography screening. These results should be treated cautiously owing to inherent weakness of observational designs and weaknesses in reporting. Future research should include a qualitative interview study and observational studies that compare generic and disease-specific measures, collect demographic data and include women from different social and ethnic groups

Selecting and Working with a Broker

4 pp.Producers who wish to trade futures or options contracts will need to work with a broker. These tips can help in selecting a broker and in forging a good working relationship

An enantio- and diastereoselective chemoenzymatic synthesis of α-fluoro β-hydroxy carboxylic esters

The trans-o-hydroxybenzylidene pyruvate aldolase-catalysed reactions between fluoropyruvate and many (het)aromatic aldehydes yield aldol adducts without subsequent dehydration. Treatment of the reaction products with hydrogen peroxide yields the corresponding syn-configured α-fluoro β-hydroxy carboxylic acids which have >98% ee. The overall chemoenzymatic approach, in which fluoropyruvate serves as a fluoroacetate equivalent, may be exploited in the synthesis of polar building blocks and fragments with potential value in drug discovery