Virtual dielectric waveguide mode description of a high-gain free-electron laser I: Theory

A set of mode-coupled excitation equations for the slowly-growing amplitudes of dielectric waveguide eigenmodes is derived as a description of the electromagnetic signal field of a high-gain free-electron laser, or FEL, including the effects of longitudinal space-charge. This approach of describing the field basis set has notable advantages for FEL analysis in providing an efficient characterization of eigenmodes, and in allowing a clear connection to free-space propagation of the input (seeding) and output radiation. The formulation describes the entire evolution of the radiation wave through the linear gain regime, prior to the onset of saturation, with arbitrary initial conditions. By virtue of the flexibility in the expansion basis, this technique can be used to find the direct coupling and amplification of a particular mode. A simple transformation converts the derived coupled differential excitation equations into a set of coupled algebraic equations and yields a matrix determinant equation for the FEL eigenmodes. A quadratic index medium is used as a model dielectric waveguide to obtain an expression for the predicted spot size of the dominant system eigenmode, in the approximation that it is a single gaussian mode.Comment: 14 page

Diagnóstico em tempo real do estado nutricional de nitrogênio de cultura do alho livre de vírus

TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Agrárias. Curso de Agronomia.Na cultura do alho, o manejo adequado do nitrogênio (N) é determinante para obtenção de altos rendimentos de bulbos. No entanto, este manejo pode ser auxiliado com o uso de um diagnóstico nutricional mais preciso. O objetivo desse trabalho foi avaliar o uso de tecnologias para avaliação em tempo real do estado nutricional de nitrogênio em plantas de alho livre de vírus submetidos a doses de N. O experimento foi conduzido em uma lavoura comercial em Fraiburgo-SC, em que testou-se num esquema fatorial 4x4x4, doses crescentes de N (0, 65, 130 e 195 kg ha-1) aplicadas no plantio, primeira cobertura (35 dias após o plantio) e segunda cobertura (após a diferenciação das plantas em bulbilhos), totalizando 64 tratamentos e três repetições. Como ferramentas de diagnóstico do estado nutricional de N nas plantas avaliou-se o uso do clorofilômetro e os teores de nitrato na solução do solo e no suco celular. Verificou-se que o aumento das doses de nitrogênio no plantio, na primeira e segunda cobertura, aumentou os teores relativos de clorofila da folha, assim como, os teores de nitrato no suco celular e na solução do solo. Conclui que o uso de ferramentas para diagnóstico do estado nutricional de N das plantas em tempo real, seja eles medidores de íons nitrato do suco celular ou da solução do solo, ou o uso do clorofilômetro, apresentam um grande potencial no monitoramento do estado nutricional de plantas de alhoThe suitable management of nitrogen for the garlic crop is determinant to get high yields of bulbs. However this management can be aided with the use of a nutritional diagnostic more accurately. The work objective was to evaluate the use of evaluation technologies at real time of the nutritional status of nitrogen of garlic plants free of virus submitted to nitrogen doses. The experiment was conducted on a commercial crop at Fraiburgo-SC, where was tested on a factorial scheme 4x4x4 increasing doses of nitrogen (0, 65, 130 and 195 kg ha-1). These doses were applied in three steps: planting, first covering (applied at 35 days after the planting) and the second covering (after the differentiation of plants to bulbils), totalizing 64 treatments with three replications. As diagnostic tools of the nutritional state of N was evaluated the use of chlorophyll meter and the nitrate levels in the soil solution and in the petiole sap. It was verified that the increase of the nitrogen doses in the first and second coverings increased the relative chlorophyll content of the leaf, as well as the nitrate levels in the petiole sap and in the soil solution. The use of tools to diagnose the nutritional status of N in plants in real time, whether nitrate ion meters of petiole sap or soil solution, or the use of chlorophyll, has great potential in monitoring the nutritional status of garlic plant

Soft X-ray seeding studies for the SLAC Linac Coherent Light Source II

We present the results from studies of soft X-ray seeding options for the LCLS-II X-ray free electron laser (FEL) at SLAC. The LCLS-II will use superconducting accelerator technology to produce X-ray pulses at up to 1 MHz repetition rate using 4 GeV electron beams. If properly seeded, these pulses will be nearly fully coherent, and highly stable in photon energy, bandwidth, and intensity, thus enabling unique experiments with intense high-resolution soft X-rays. Given the expected electron beam parameters from start to end simulations and predicted FEL performance, our studies reveal echo enabled harmonic generation (EEHG) and soft X-ray self-seeding (SXRSS) as promising and complementary seeding methods. We find that SXRSS has the advantage of simplicity and will deliver 5-35 times higher spectral brightness than EEHG in the 1-2 nm range, but lacks some of the potential for phase-stable multipulse and multicolor FEL operations enabled by external laser seeding with EEHG

Stop smoking practitioner consensus on barriers and facilitators to smoking cessation in pregnancy and how to address these: A modified Delphi survey.

Introduction Pregnant women can experience barriers and facilitators towards achieving smoking cessation. We sought consensus from smoking cessation practitioners on how influential pre-identified barriers and facilitators can be on pregnant women's smoking behaviour, and how difficult these might be to manage. Suggestions for techniques that could help overcome the barriers or enhance the facilitators were elicited and consensus sought on the appropriateness for their use in practice. Methods Forty-four practitioners who provided cessation support to pregnant women completed a three-round modified Delphi survey. Round one sought consensus on the ‘influence’ and ‘difficulty’ of the barriers and facilitators, and gathered respondents' suggestions on ways to address these. Rounds two and three sought further consensus on the barriers and facilitators and on ‘appropriateness’ of the respondent-suggested techniques. The techniques were coded for behaviour change techniques (BCTs) content using existing taxonomies. Results Barriers and facilitators considered to be the most important mainly related to the influence of significant others and the women's motivation & self-efficacy. Having a supportive partner was considered the most influential, whereas lack of support from partner was the only barrier that reached consensus as being difficult to manage. Barriers relating to social norms were also considered influential, however these received poor coverage of respondent-suggested techniques. Those considered the easiest to address mainly related to aspects of cessation support, including misconceptions surrounding the use of nicotine replacement therapy (NRT). Barriers and facilitators relating to the women's motivation & self-efficacy, such as the want to protect the baby, were also considered as being particularly easy to address. Fifty of the 54 respondent-suggested techniques reached consensus as being appropriate. Those considered the most appropriate ranged from providing support early, giving correct information on NRT, highlighting risks and benefits and reinforcing motivating beliefs. Thirty-three BCTs were identified from the respondent-suggested techniques. ‘Social support (unspecified)’, ‘Tailor interactions appropriately’ and ‘Problem solving’ were the most frequently coded BCTs. Conclusions Involving partners in quit attempts was advocated. Existing support could be potentially improved by establishing appropriate ways to address barriers relating to pregnant smokers' ‘social norms’. In general, providing consistent and motivating support seemed favourable

Properties of electrons scattered on a strong plane electromagnetic wave with a linear polarization: classical treatment

The relations among the components of the exit momenta of ultrarelativistic electrons scattered on a strong electromagnetic wave of a low (optical) frequency and linear polarization are established using the exact solutions to the equations of motion with radiation reaction included (the Landau-Lifshitz equation). It is found that the momentum components of the electrons traversed the electromagnetic wave depend weakly on the initial values of the momenta. These electrons are mostly scattered at the small angles to the direction of propagation of the electromagnetic wave. The maximum Lorentz factor of the electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momenta. The momentum component parallel to the electric field strength vector of the electromagnetic wave is determined only by the diameter of the laser beam measured in the units of the classical electron radius. As for the reflected electrons, they for the most part lose the energy, but remain relativistic. There is a reflection law for these electrons that relates the incident and the reflection angles and is independent of any parameters.Comment: 12 pp, 3 fig

Women, Environments and Chronic Disease: Shifting the Gaze from Individual Level to Structural Factors

Introduction: Chronic heart and respiratory diseases are two of the leading causes of morbidity and mortality affecting women. Patterns of and disparities in chronic diseases between sub-populations of women suggest that there are social as well as individual level factors which enhance or impede the prevention or development of chronic respiratory and cardio- vascular diseases. By examining the sex, gender and diversity based dimensions of women’s lung and heart health and how these overlap with environmental factors we extend analysis of preventive health beyond the individual level. We demon- strate how biological, environmental and social factors interact and operate in women’s lives, structuring their opportunities for health and abilities to prevent or manage chronic cardiovascular and respiratory diseases.Methods: This commentary is based on the findings from two evidence reviews, one conducted on women’s heart health, and another on women’s lung health. Additional literature was also reviewed which assessed the relationship between environmental factors and chronic heart and lung diseases. This paper explores how obesogenic environments, exposure to tobacco smoke, and the experience of living in deprived areas can affect women’s heart and respiratory health. We discuss the barriers which impede women’s ability to engage in physical activity, consume healthy foods, or avoid smoking, tobacco smoke, and other airborne contaminants.Results: Sex, gender and diversity clearly interact with environmental factors and shape women’s promotion of health and prevention of chronic respiratory and cardiovascular diseases. The environments women live in structure their opportunities for health, and women navigate these environments in unique ways based on gender, socioeconomic status, race/ethnicity and other social factors.Discussion: Future research, policy and programs relating to the prevention of chronic disease need to move beyond linear individually-oriented models and address these complexities by developing frameworks and interventions which improve environmental conditions for all groups of women. Indeed, in order to improve women’s health, broad social and economic policies and initiatives are required to eliminate negative environmental impacts on women’s opportunities for health

Minimum Spectral Bandwidth in Echo Seeded Free Electron Lasers

This paper examines the impact of non-linear longitudinal phase distortions on the spectral bandwidth in echo seeded free electron lasers (FELs). It extends the existing theory developed in Hemsing [1] for echo-enabled harmonic generation (EEHG) to include finite laser pulse durations. An analytic expression for the shape of the optimized longitudinal bunching envelope is derived, and is used to determine the laser and electron beam pulse durations that minimize the seeded bandwidth in the presence of arbitrary phase distortions. The time-bandwidth product (TBP) is also derived, and is shown that the TBP and the bandwidth increase by no more than 2 from their transform-limited values when the bandwidth is minimized

Reshuffling and Relocating: The Gendered and Income-Related Differential Effects of Restricting Smoking Locations

This study investigates secondhand smoke (SHS) exposure and management in the context of smoking location restrictions, for nonsmokers, former, and current smokers. A purposive sample of 47 low income and non-low-income men and women of varied smoking statuses was recruited to participate in a telephone interview or a focus group. Amidst general approval of increased restrictions there were gendered patterns of SHS exposure and management, and effects of SHS policies that reflect power, control, and social roles that need to be considered as policies are developed, implemented and monitored. The experience of smoking restrictions and the management of SHS is influenced by the social context (relationship with a partner, family member, or stranger), the space of exposure (public or private, worksite), the social location of individuals involved (gender, income), and differential tolerance to SHS. This confluence of factors creates differing unintended and unexpected consequences to the social and physical situations of male and female smokers, nonsmokers, and former smokers. These factors deserve further study, in the interests of informing the development of future interventions and policies restricting SHS