Suppression of electron spin decoherence in a quantum dot

The dominant source of decoherence for an electron spin in a quantum dot is the hyperfine interaction with the surrounding bath of nuclear spins. The decoherence process may be slowed down by subjecting the electron spin to suitable sequences of external control pulses. We investigate the performance of a variety of dynamical decoupling protocols using exact numerical simulation. Emphasis is given to realistic pulse delays and the long-time limit, beyond the domain where available analytical approaches are guaranteed to work. Our results show that both deterministic and randomized protocols are capable to significantly prolong the electron coherence time, even when using control pulse separations substantially larger than what expected from the {\em upper cutoff} frequency of the coupling spectrum between the electron and the nuclear spins. In a realistic parameter range, the {\em total width} of such a coupling spectrum appears to be the physically relevant frequency scale affecting the overall quality of the decoupling.Comment: 8 pages, 3 figures. Invited talk at the XXXVII Winter Colloquium on the Physics of Quantum Electronics, Snowbird, Jan 2007. Submitted to J. Mod. Op

Computation of Windstorm Catalogues and Windstorm Severity Indices 1969-2013 for the UK and 11 UK Regions

This document outlines the methodology employed by the Climate Extremes Group in the Department of Space and Climate Physics at University College London (UCL) to identify and severity rank UK windstorms for the 45-year period from 1969 to 2013. The UCL methodology is underpinned by a robust UK windstorm definition that is applied to cleaned and homogenised continuous gust observations from 262 low-level station sites spread evenly around the UK. Windstorm catalogues and event severity rankings are provided for the whole UK and, uniquely, for each of 11 UK regions. The product’s background, input data, creation methods and output form are summarised under eight headings. References and appendix figures provide additional information

Methodology for Computation of UK Windstorm Gust Return Levels on a High Spatial Resolution (100 m) Grid

This document outlines the methodology employed by the Climate Extremes Group in the Department of Space and Climate Physics at University College London (UCL) to compute windstorm gust return levels (from 1 year to 1000 years) at high spatial resolution (100 m grid) for the whole UK. The methodology is summarised under eight headings. A ninth section addresses the precision of the gust return levels. A product format section, references and an appendix provide additional information

Global tropical cyclones and European windstorms in recent decline

Tropical cyclones worldwide and European windstorms (extratropical cyclones) are the main cause of great weather disasters worldwide but low confidence exists in the quantification and attribution of trends in these storms. This uncertainty is caused by limitations in the quality and quantity of historical data, by the presence of large year-to-year variability in storm counts and by an incomplete understanding of the mechanisms that cause trends. Here we reduce this uncertainty by clarifying the nature, significance and underlying causes of storm trends for the recent 1971 to 2010 period of generally sound surface windspeed data. We find that global tropical cyclones and European winter extratropical storms are mostly decreasing in annual frequency and accumulated power; for the periods 1981 to 2010 and 1991 to 2010 all trends are decreasing and in several cases significantly so. We attribute the recent significant decrease in global tropical cyclone activity to a trend towards colder ENSO (El Niño Southern Oscillation) conditions that produces anomalous zonal flows which tend to inhibit storm spin-up in the North Pacific. We attribute the recent significant decrease in UK and European winter windstorm activity to a decrease in North Atlantic tropospheric thermal wind associated with warmer winter air temperatures at polar and subpolar latitudes. Despite global temperatures rising by about 0.5°C since 1971 our results suggest that climate change has had no discernible positive impact on either globally averaged tropical cyclone activity or on European extratropical cyclone activity; indeed global warming may be contributing to the recent decrease in European extratropical storm activity

Learning to See Forces: Surgical Force Prediction with RGB-Point Cloud Temporal Convolutional Networks

Robotic surgery has been proven to offer clear advantages during surgical procedures, however, one of the major limitations is obtaining haptic feedback. Since it is often challenging to devise a hardware solution with accurate force feedback, we propose the use of "visual cues" to infer forces from tissue deformation. Endoscopic video is a passive sensor that is freely available, in the sense that any minimally-invasive procedure already utilizes it. To this end, we employ deep learning to infer forces from video as an attractive low-cost and accurate alternative to typically complex and expensive hardware solutions. First, we demonstrate our approach in a phantom setting using the da Vinci Surgical System affixed with an OptoForce sensor. Second, we then validate our method on an ex vivo liver organ. Our method results in a mean absolute error of 0.814 N in the ex vivo study, suggesting that it may be a promising alternative to hardware based surgical force feedback in endoscopic procedures.Comment: MICCAI 2018 workshop, CARE(Computer Assisted and Robotic Endoscopy

Replicating Annual North Atlantic Hurricane Activity 1878-2012 from Environmental Variables

Statistical models can replicate annual North Atlantic hurricane activity from large-scale environmental field data for August and September, the months of peak hurricane activity. We assess how well the six environmental fields used most often in contemporary statistical modeling of seasonal hurricane activity replicate North Atlantic hurricane numbers and Accumulated Cyclone Energy (ACE) over the 135-year period from 1878 to 2012. We find that these fields replicate historical hurricane activity surprisingly well, showing that contemporary statistical models and their seasonal physical links have long-term robustness. We find that August-September zonal trade wind speed over the Caribbean Sea and the tropical North Atlantic is the environmental field which individually replicates long-term hurricane activity the best, and that trade wind speed combined with the difference in sea surface temperature between the tropical Atlantic and the tropical mean is the best multi-predictor model. Comparing the performance of the best single-predictor and best multi-predictor models shows that they exhibit little difference in hindcast skill for predicting long-term ACE but that the best multi-predictor model offers improved skill for predicting long-term hurricane numbers. We examine whether replicated real-time prediction skill 1983-2012 increases as the model training period lengthens and find evidence that this happens slowly. We identify a dropout in hurricane replication centered on the 1940s and show that this is likely due to a decrease in data quality which affects all data sets but Atlantic sea surface temperatures in particular. Finally we offer insights on the implications of our findings for seasonal hurricane prediction

Perception of Students on Online Homework in Integral Calculus and Its Relation on Their Motivation and Performance

Teachers are always in the search of better teaching and learning techniques to keep students engaged and motivated in class. One emerging technology is the use of online homework whereby students may be given unlimited chances of working on a set of problems that vary in their every attempt for self-practice. These are presented in a set-up perceived as more engaging and appropriate to today’s type of learners. This study explored the perception of Integral Calculus students on taking online homework particularly on the topic integration techniques. DLSU-D Schoolbook, the learning management system of the university was utilized to administer the online exercises and learning modules to students. A total of 127 students became part of the study and were asked to answer questionnaires that determined their perception of online homework as well as their motivation level towards engaging in math activities. Their performance was also determined through a comprehensive test. Results showed they had a high positive perception of online homework and they found it useful in studying lessons and in their preparation for exams. It was also found through correlation analysis that perception is significantly correlated with the motivation level of students but not with their performance

The Interaction Pattern of Murine Serum Ficolin-A with Microorganisms

The ficolins are soluble pattern recognition molecules in the lectin pathway of complement, but the spectrum and mode of interaction with pathogens are largely unknown. In this study, we investigated the binding properties of the murine serum ficolin-A towards a panel of different clinical relevant microorganisms (N = 45) and compared the binding profile with human serum ficolin-2 and ficolin-3. Ficolin-A was able to bind Gram-positive bacteria strains including E. faecalis, L. monocytogenes and some S. aureus strains, but not to the investigated S. agalactiae (Group B streptococcus) strains. Regarding Gram-negative bacteria ficolin-A was able to bind to some E. coli and P. aeruginosa strains, but not to the investigated Salmonella strains. Of particular interest ficolin-A bound strongly to the pathogenic E. coli, O157:H7 and O149 strains, but it did not bind to the non-pathogenic E. coli, ATCC 25922 strain. Additionally, ficolin-A was able to bind purified LPS from these pathogenic strains. Furthermore, ficolin-A bound to a clinical isolate of the fungus A. fumigatus. In general ficolin-2 showed similar selective binding spectrum towards pathogenic microorganisms as observed for ficolin-A indicating specific pathophysiological roles of these molecules in host defence. In contrast, ficolin-3 did not bind to any of the investigated microorganisms and the anti-microbial role of ficolin-3 still remains elusive

Characterization of Residential Pesticide Use and Chemical Formulations through Self-Report and Household Inventory: The Northern California Childhood Leukemia Study

Background: Home and garden pesticide use has been linked to cancer and other health outcomes in numerous epidemiological studies. Exposure has generally been self-reported, so the assessment is potentially limited by recall bias and lack of information on specific chemicals. Objectives: As part of an integrated assessment of residential pesticide exposure, we identified active ingredients and described patterns of storage and use. Methods: During a home interview of 500 residentially stable households enrolled in the Northern California Childhood Leukemia Study during 2001–2006, trained interviewers inventoried residential pesticide products and queried participants about their storage and use. U.S. Environmental Protection Agency registration numbers, recorded from pesticide product labels, and pesticide chemical codes were matched to public databases to obtain information on active ingredients and chemical class. Poisson regression was used to identify independent predictors of pesticide storage. Analyses were restricted to 259 participating control households. Results: Ninety-five percent (246 of 259) of the control households stored at least one pesticide product (median, 4). Indicators of higher sociodemographic status predicted more products in storage. We identified the most common characteristics: storage areas (garage, 40%; kitchen, 20%), pests treated (ants, 33%; weeds, 20%), pesticide types (insecticides, 46%; herbicides, 24%), chemical classes (pyrethroids, 77%; botanicals, 50%), active ingredients (pyrethrins, 43%) and synergists (piperonyl butoxide, 42%). Products could contain multiple active ingredients. Conclusions: Our data on specific active ingredients and patterns of storage and use will inform future etiologic analyses of residential pesticide exposures from self-reported data, particularly among households with young children