Ultrashort intense-field optical vortices produced with laser-etched mirrors

We introduce a simple and practical method to create ultrashort intense optical vortices for applications involving high-intensity lasers. Our method utilizes femtosecond laser pulses to laser-etch grating lines into laser-quality gold mirrors. These grating lines holographically encode an optical vortex. We derive mathematical equations for each individual grating line to be etched, for any desired (integer) topological charge. We investigate the smoothness of the etched grooves. We show that they are smooth enough to produce optical vortices with an intensity that is only a few percent lower than in the ideal case. We demonstrate that the etched gratings can be used in a folded version of our 2f-2f setup [Mariyenko et al., Opt. Express 19, 7599 (2005)] to compensate angular dispersion. Lastly, we show that the etched gratings withstand intensities of up to 10^12 W/cm2.Comment: 14 pages, 12 figures, submitted to Optics Expres

Knowledge tree: Putting discourse into computer‐based learning

Most CBL materials currently in use model only the declarative aspects of the learning process. If such courseware is used without careful planning, this can be dangerous because one of the most fundamental aspects of education is the dialogue that occurs between teachers and the students. Traditionally, this has taken place in informal discussions as well as in formal small‐group learning sessions such as the conventional tutorial. However, as the student‐staff ratio increases, so does the opportunity for this type of personal dialogue decrease. Modern networking technology offers a huge potential to add discourse to CBL, but there are many pedagogical problems involved with the intrinsically ephemeral and anarchic nature both of the Internet and of most conferencing or bulletin‐board systems. In this paper we describe a software system called Knowledge Tree (KT) which we have developed to address some of these issues. KT combines a hierarchical concept‐oriented database functionality with that of a Usenet‐style bulletin board Using this, a knowledge garden may be developed for any subject area. These each contain a hypermedia database of frequently asked questions, together with answers provided by subject experts. There is provision for inter‐student discussions of problems and issues. When students ask new questions these are automatically emailed to a relevant subject expert (determined by a subject‐specific concept thesaurus). The answer is then placed in the database which eventually grows to become a valuable teaching resource. KT is discipline‐independent as the concept thesaurus can be changed to encapsulate any domain of knowledge. We have used it in support of conventional lecture courses, as an important component of a multimedia course, and for general IT support. These examples illustrate the role that this system can play both in basic information provision, and in facilitating the discussion of deep issues

Manufacturing checkout of orbital operational stages Midterm report, period ending 24 Feb. 1965

Manufacturing checkout of orbital operational Saturn S-IVB stage and instrument unit for parking orbit operation

Intense-Field Ionization of Monoaromatic Hydrocarbons using Radiation Pulses of Ultrashort Duration: Monohalobenzenes and Azabenzenes

Using 50-fs, 800-nm pulses, we study the intense-field ionization and fragmentation of the monohalobenzenes C_(6)H_(5)-X (X=F, Cl, Br, I) and of the heterocyclics azabenzene C5H5N (pyridine) and the three diazabenzenes C_(4)H_(4)N_(2) (pyridazine, pyrimidine, and pyrazine). Avoiding focal intensity averaging we find indications of resonance-enhanced MPI. In the monohalobenzenes the propensity for fragmentation increases for increasing Z: fluorobenzene yields predominantly C6H5Fn+, while iodobenzene yields atomic ions with charges up to I^(8+). We ascribe this to the heavy-atom effect: the large charge of the heavy halogens' nuclei induces ultrafast intersystem crossing to dissociative triplet states

Improving the Crystal Ball: Consumer Consensus and Retail Prediction Markets

Retail buyers\u27 forecasts, decisions, and subsequent purchases result in billions of dollars of merchandise being purchased and offered for sale by retailers around the world. However, academic research examining this decision process has been limited, and recommendations for improvement almost nonexistent. In the present study, we begin to address this issue by introducing a new approach that compares retail buyers\u27 consensus forecasts with those from a sample of “ordinary” consumers. The potential for incorporating forecasts from ordinary consumers suggests an opportunity to create what are termed retail prediction markets, which offer significant potential to improve the accuracy of buyers’ forecasts. We conclude with limitations and areas for future research

Assessing the impact on chronic disease of incorporating the societal cost of greenhouse gases into the price of food: an econometric and comparative risk assessment modelling study

Objectives To model the impact on chronic disease of a tax on UK food and drink that internalises the wider costs to society of greenhouse gas (GHG) emissions and to estimate the potential revenue. Design An econometric and comparative risk assessment modelling study. Setting The UK. Participants The UK adult population. Interventions Two tax scenarios are modelled: (A) a tax of £2.72/tonne carbon dioxide equivalents (tCO2e)/100 g product applied to all food and drink groups with above average GHG emissions. (B) As with scenario (A) but food groups with emissions below average are subsidised to create a tax neutral scenario. Outcome measures Primary outcomes are change in UK population mortality from chronic diseases following the implementation of each taxation strategy, the change in the UK GHG emissions and the predicted revenue. Secondary outcomes are the changes to the micronutrient composition of the UK diet. Results Scenario (A) results in 7770 (95% credible intervals 7150 to 8390) deaths averted and a reduction in GHG emissions of 18 683 (14 665to 22 889) ktCO2e/year. Estimated annual revenue is £2.02 (£1.98 to £2.06) billion. Scenario (B) results in 2685 (1966 to 3402) extra deaths and a reduction in GHG emissions of 15 228 (11 245to 19 492) ktCO2e/year. Conclusions Incorporating the societal cost of GHG into the price of foods could save 7770 lives in the UK each year, reduce food-related GHG emissions and generate substantial tax revenue. The revenue neutral scenario (B) demonstrates that sustainability and health goals are not always aligned. Future work should focus on investigating the health impact by population subgroup and on designing fiscal strategies to promote both sustainable and healthy diets

Radiotherapy for Soft Tissue Sarcoma of the Proximal Lower Extremity

Soft-tissue sarcoma (STS) is a histopathologically diverse group of tumors accounting for approximately 10,000 new malignancies in the US each year. The proximal lower extremity is the most common site for STS, accounting for approximately one-third of all cases. Coordinated multimodality management in the form of surgery and radiation is often critical to local control, limb preservation, and functional outcome. Based on a review of currently available Medline literature and professional experience, this paper provides an overview of the treatment of STS of the lower extremity with a particular focus on the modern role of radiotherapy

Overall and income specific effect on prevalence of overweight and obesity of 20% sugar sweetened drink tax in UK: econometric and comparative risk assessment modelling study

Objective To model the overall and income specific effect of a 20% tax on sugar sweetened drinks on the prevalence of overweight and obesity in the UK. Design Econometric and comparative risk assessment modelling study. Setting United Kingdom. Population Adults aged 16 and over. Intervention A 20% tax on sugar sweetened drinks. Main outcome measures The primary outcomes were the overall and income specific changes in the number and percentage of overweight (body mass index ≥25) and obese (≥30) adults in the UK following the implementation of the tax. Secondary outcomes were the effect by age group (16-29, 30-49, and ≥50 years) and by UK constituent country. The revenue generated from the tax and the income specific changes in weekly expenditure on drinks were also estimated. Results A 20% tax on sugar sweetened drinks was estimated to reduce the number of obese adults in the UK by 1.3% (95% credible interval 0.8% to 1.7%) or 180 000 (110 000 to 247 000) people and the number who are overweight by 0.9% (0.6% to 1.1%) or 285 000 (201 000 to 364 000) people. The predicted reductions in prevalence of obesity for income thirds 1 (lowest income), 2, and 3 (highest income) were 1.3% (0.3% to 2.0%), 0.9% (0.1% to 1.6%), and 2.1% (1.3% to 2.9%). The effect on obesity declined with age. Predicted annual revenue was £276m (£272m to £279m), with estimated increases in total expenditure on drinks for income thirds 1, 2, and 3 of 2.1% (1.4% to 3.0%), 1.7% (1.2% to 2.2%), and 0.8% (0.4% to 1.2%). Conclusions A 20% tax on sugar sweetened drinks would lead to a reduction in the prevalence of obesity in the UK of 1.3% (around 180 000 people). The greatest effects may occur in young people, with no significant differences between income groups. Both effects warrant further exploration. Taxation of sugar sweetened drinks is a promising population measure to target population obesity, particularly among younger adults

The Brighton declaration: the value of non-communicable disease modelling in population health sciences.

The Brighton declaration arose out of a one day workshop held in Brighton in September 2013 as part of the Society for Social Medicine annual conference. The workshop convened UK based non-communicable disease modellers to discuss the challenges and opportunities for non-communicable disease modelling in the UK. The declaration describes the value and importance of non-communicable disease modelling, both for research and for informing health policy. The declaration also describes challenges and issues for non-communicable disease modelling. The declaration has been endorsed by many non-communicable disease modellers in the UK.The following academics collaborated with the authors to finalise this article are and acknowledged as co-signatories on its content. The authors are extremely grateful for their input. University of Cambridge: Ali Abbas, Marko Tanio; University of Edinburgh: Dr Susannah McLean; UK Health Forum: Martin Brown, Tim Marsh, Marco Mesa-Frias, Lise Retat; Imperial College London: Anthony Laverty; The London School of Hygiene and Tropical Medicine: Zaid Chalabi; University College London: Luz Sanchez Romero; University of Oxford: Anja Mizdrak, Mike Rayner, Marco Springmann; University of Sheffield: Alan Brennan, James Chilcott, John Holmes, Petra Meier, John Mooney; University of Southampton: Grant Aitken. ADMB and OTM are funded by the Wellcome Trust. PS is funded by the British Heart Foundation. JW is funded by an MRC Population Health Scientist Fellowship.This is the final published version. The article was originally published in the European Journal of Epidemiology (2014) 29, 867–870, DOI 10.1007/s10654-014-9978-0