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Sample records for fels longitudinal study

  1. Validation of Maturity Offset in the Fels Longitudinal Study.

    PubMed

    Malina, Robert M; Choh, Audrey C; Czerwinski, Stefan A; Chumlea, Wm Cameron

    2016-08-01

    Sex-specific equations for predicting maturity offset, time before or after peak height velocity (PHV), were evaluated in 63 girls and 74 boys from the Fels Longitudinal Study. Serially measured heights (0.1 cm), sitting heights (0.1 cm), weights (0.1 kg), and estimated leg lengths (0.1 cm) from 8 to 18 years were used. Predicted age at PHV (years) was calculated as the difference between chronological age (CA) and maturity offset. Actual age at PHV for each child was derived with a triple logistic model (Bock-Thissen-du Toit). Mean predicted maturity offset was negative and lowest at 8 years and increased linearly with increasing CA. Predicted ages at PHV increased linearly with CA from 8 to 18 years in girls and from 8 to 13 years in boys; predictions varied within relatively narrow limits from 12 to 15 years and then increased to 18 years in boys. Differences between predicted and actual ages at PHV among youth of contrasting maturity status were significant across the age range in both sexes. Dependence of predicted age at PHV upon CA at prediction and on actual age at PHV limits its utility as an indicator of maturity timing and in sport talent programs.

  2. Heritability of calcaneal quantitative ultrasound measures in healthy adults from the Fels Longitudinal Study.

    PubMed

    Lee, Miryoung; Czerwinski, Stefan A; Choh, Audrey C; Towne, Bradford; Demerath, Ellen W; Chumlea, Wm Cameron; Sun, Shumei S; Siervogel, Roger M

    2004-11-01

    Quantitative ultrasound (QUS) measurements of bone have been reported to predict osteoporotic fracture risk in postmenopausal women and older men. Although many studies have examined the heritability of bone mineral density (BMD), few studies have estimated the heritability of calcaneal QUS phenotypes. In the present study, we examined the genetic regulation of calcaneal QUS parameters in individuals from nuclear and extended families. The study population includes 260 men and 295 women aged 18-91 years (mean+/-SD: 46+/-16 years) who belong to 111 pedigrees in the Fels Longitudinal Study. Three measures of calcaneal structure were collected from both the right and left heel using the Sahara bone sonometer. These measures included broadband ultrasound attenuation (BUA), speed of sound (SOS), and the quantitative ultrasound index (QUI). We used a variance components based maximum likelihood method to estimate the heritability of QUS parameters while simultaneously adjusting for covariate effects. Additionally, we used bivariate extensions of these methods to calculate additive genetic and random environmental correlations among QUS measures. All phenotypes demonstrated statistically significant heritabilities (P<0.0000001). Heritabilities in the right heel (h2+/-SE) were h2=0.59+/-0.10 for BUA, h2=0.73+/-0.09 for SOS, and h2=0.72+/-0.09 for QUI. Similarly, heritabilities for the left heel were h2=0.52+/-0.10, h2=0.75+/-0.10, and h2=0.70+/0.10, respectively. There was evidence for significant genetic and environmental correlations among these six QUS measures. Combinations of QUS measures in the right and left heel demonstrated genetic correlations of 0.94-0.99 and all were significantly different from one indicating at least a partially unique genetic architecture for each of these measures. This study demonstrates that QUS measures of the calcaneus among healthy men and women are heritable, and there are large shared additive genetic effects among all of the traits

  3. Left ventricular mass, abdominal circumference and age: the Fels longitudinal study.

    PubMed

    Chumlea, W C; Schubert, C M; Towne, B; Siervogel, R M; Sun, S S

    2009-11-01

    To determine the relationship of abdominal circumference with increased left ventricular mass (LVM) from young adulthood into old age. Cross-sectional echocardiographic images were taken from 182 men and 220 women in the Fels Longitudinal Study 20 to 75 years of age to determine left ventricular mass. Left ventricular mass was divided by stature raised to the power of 2.7 (LVM/ht2.7) in order to minimize the impact of heart size variation from body size without overcompensating for the adverse effect of obesity. Abdominal circumference was measured and BMI calculated from stature and weight and categories of overweight, obesity and abdominal obesity were determined using published cut points. Regression models were used to describe the relationships of age, abdominal circumference, BMI and self-reported physical activity to LVM/ht2.7. Age, abdominal circumference and BMI were each positively and significantly related to an increased LVM/ht2.7 in men and women (p < 0.05). In the men, multivariate models indicated that abdominal circumference and BMI were both significantly related to an increased LVM/ht2.7, but the inclusion of BMI in these models for the women reduced the association of abdominal circumference and physical activity below significant levels. In the men, there was also a quadratic association of abdominal circumference with LVM/ht2.7 that was significant along with BMI and physical activity. Sex-specific logistic regressions with BMI and abdominal circumference obesity categories did not change or improve the initial findings in men or women. In women, increases in abdominal fatness as reflected in abdominal circumference at any age are linearly related to an increase in LVM/ht2.7, but the relationship of overall fatness as reflected in BMI with LVM/ht2.7 is stronger. In men, both abdominal fatness and overall fatness at any age are linearly related to an increase LVM/ht2.7. However, the significant curvilinear association of abdominal circumference

  4. Studies Of Coherent Synchrotron Radiation And Longitudinal Space Charge In The Jefferson Lab FEL Driver

    SciTech Connect

    Tennant, Christopher D.; Douglas, David R.; Li, Rui; Tsai, C.-Y.

    2014-12-01

    The Jefferson Laboratory IR FEL Driver provides an ideal test bed for studying a variety of beam dynamical effects. Recent studies focused on characterizing the impact of coherent synchrotron radiation (CSR) with the goal of benchmarking measurements with simulation. Following measurements to characterize the beam, we quantitatively characterized energy extraction via CSR by measuring beam position at a dispersed location as a function of bunch compression. In addition to operating with the beam on the rising part of the linac RF waveform, measurements were also made while accelerating on the falling part. For each, the full compression point was moved along the backleg of the machine and the response of the beam (distribution, extracted energy) measured. Initial results of start-to-end simulations using a 1D CSR algorithm show remarkably good agreement with measurements. A subsequent experiment established lasing with the beam accelerated on the falling side of the RF waveform in conjunction with positive momentum compaction (R56) to compress the bunch. The success of this experiment motivated the design of a modified CEBAF-style arc with control of CSR and microbunching effects.

  5. Do changes in body mass index percentile reflect changes in body composition in children? Data from the Fels Longitudinal Study.

    PubMed

    Demerath, Ellen W; Schubert, Christine M; Maynard, L Michele; Sun, Shumei S; Chumlea, W Cameron; Pickoff, Arthur; Czerwinski, Stefan A; Towne, Bradford; Siervogel, Roger M

    2006-03-01

    Our aim was to examine the degree to which changes in BMI percentile reflect changes in body fat and lean body mass during childhood and how age and gender affect these relationships. This analysis used serial data on 494 white boys and girls who were aged 8 to 18 years and participating in the Fels Longitudinal Study (total 2319 observations). Total body fat (TBF), total body fat-free mass (FFM), and percentage of body fat (%BF) were determined by hydrodensitometry, and then BMI was partitioned into its fat and fat-free components: fat mass index (FMI) and FFM index (FFMI). We calculated predicted changes (Delta) in FMI, FFMI, and %BF for each 10-unit increase in BMI percentile using mixed-effects models. FFMI had a linear relationship with BMI percentile, whereas FMI and %BF tended to increase dramatically only at higher BMI percentiles. Gender and age had significant effects on the relationship between BMI percentile and FFMI, FMI, and %BF. Predicted Delta%BF for boys 13 to 18 years of age was negative, suggesting loss of relative fatness for each 10-unit increase in BMI percentile. In this longitudinal study of white children, FFMI consistently increased with BMI percentile, whereas FMI and %BF had more complicated relationships with BMI percentile depending on gender, age, and whether BMI percentile was high or low. Our results suggest that BMI percentile changes may not accurately reflect changes in adiposity in children over time, particularly among male adolescents and children of lower BMI.

  6. Quantitative genetics of cortical bone mass in healthy 10-year-old children from the Fels Longitudinal Study

    PubMed Central

    Duren, Dana L.; Sherwood, Richard J.; Choh, Audrey C.; Czerwinski, Stefan A.; Chumlea, Wm. Cameron; Lee, Miryoung; Sun, Shumei S.; Demerath, Ellen W.; Siervogel, Roger M.; Towne, Bradford

    2007-01-01

    The genetic influences on bone mass likely change throughout the life span, but most genetic studies of bone mass regulation have focused on adults. There is, however, a growing awareness of the importance of genes influencing the acquisition of bone mass during childhood on lifelong bone health. The present investigation examines genetic influences on childhood bone mass by estimating the residual heritabilities of different measures of second metacarpal bone mass in a sample of 600 10-year-old participants from 144 families in the Fels Longitudinal Study. Bivariate quantitative genetic analyses were conducted to estimate genetic correlations between cortical bone mass measures, and measures of bone growth and development. Using a maximum likelihood-based variance components method for pedigree data, we found a residual heritability estimate of 0.71 for second metacarpal cortical index. Residual heritability estimates for individual measures of cortical bone (e.g., lateral cortical thickness, medial cortical thickness) ranged from 0.47 to 0.58, at this pre-pubertal childhood age. Low genetic correlations were found between cortical bone measures and both bone length and skeletal age. However, after Bonferonni adjustment for multiple testing, ρG was not significantly different from 0 for any of these pairs of traits. Results of this investigation provide evidence of significant genetic control over bone mass largely independent of maturation while bones are actively growing and before rapid accrual of bone that typically occurs during puberty. PMID:17056310

  7. Body mass index associations between mother and offspring from birth to age 18: the Fels Longitudinal Study.

    PubMed

    Swanton, S; Choh, A C; Lee, M; Laubach, L L; Linderman, J K; Czerwinski, S A; Peterson, M J

    2017-06-01

    Parental obesity is a known determinant of childhood obesity. Previous research has shown a strong maternal influence on body mass index (BMI) during infancy and early childhood. The purpose of this research was to investigate the BMI associations between mother and offspring from birth to age 18 years. Participants were selected from the Fels Longitudinal Study. The current study sample includes 427 (215 mother/son and 212 mother/daughter) mother/child pairs. These pairs are repeatedly measured at multiple age groups in children, resulting in a total of 6,263 (3,215 mother/son, 3,048 mother/daughter) observations for data analysis. Inclusion criteria were children with measured height and weight for BMI collected at ages 0 to 18 years and their mother with BMI data. Maternal influences of BMI on offspring BMI from birth to early adulthood were analyzed by Spearman correlations and linear regression analyses. Mother/son BMI correlations became statistically significant (p ≤ 0.05) at age 5-6 years and were significant through puberty and into early adulthood at age 18 years. Mother/daughter correlations became significant at age 1.5 years and also continued through adolescence, puberty and early adulthood at age 18 years. Associations persisted after the study sample was grouped into life stages and adjusted for decade of birth and parity. The mother/daughter relationship was more strongly correlated than the mother/son relationship and also became statistically significant at an earlier age than boys.

  8. Body mass index during childhood, adolescence and young adulthood in relation to adult overweight and adiposity: the Fels Longitudinal Study.

    PubMed

    Guo, S S; Huang, C; Maynard, L M; Demerath, E; Towne, B; Chumlea, W C; Siervogel, R M

    2000-12-01

    Childhood overweight develops during 'critical periods', but the relationship of body mass index (BMI) patterns during 'critical periods' from childhood into adulthood with subsequent overweight and adiposity has not been previously investigated. BMI patterns during early childhood, pubescence and post-pubescence and their independent effects on overweight and body fatness at 35-45 y of age were examined along with birth weight and the effects of adult lifestyle factors. BMI parameters describing the timing, velocity minimum (min) and maximum (max) values from 2 to 25 y of age were related to adulthood BMI values and total and percentage body fat (TBF, %BF) at 35-45 y. These data were from 180 males and 158 females in the Fels Longitudinal Study. There was no sex difference in the timing of BMI rebound, but the age of BMI maximum velocity and maximum BMI were both earlier in girls. Children with an earlier BMI rebound had larger BMI values at rebound and at maximum velocity. Children who reached maximum BMI at later age had larger maximum BMI values. Maximum BMI was a strong predictor for adult BMI and in females, a strong predictor of adulthood TBF and %BF. Maximum BMI was closely related to maximum BMI velocity in females and in males, BMI at maximum velocity is a strong predictor of TBF and %BF. Changes in childhood BMI were related to adult overweight and adiposity more so in females than males. BMI rebound is a significant important period related to overweight at 35-45 y in females but not in males. However BMI patterns during and post-adolescence were more important than the BMI rebound for adulthood TBF and %BF status. There is marked tracking in BMI from approximately 20 y into 35-45 y. The pattern of BMI changes from 2 to 25 y had stronger effects on subsequent adult overweight than birth weight and adult lifestyle variables.

  9. Variation in Timing, Duration, Intensity, and Direction of Adolescent Growth in the Mandible, Maxilla, and Cranial Base: the Fels Longitudinal Study

    PubMed Central

    Nahhas, Ramzi W.; Valiathan, Manish; Sherwood, Richard J.

    2014-01-01

    There is considerable individual variation in the timing, duration, and intensity of growth that occurs in the craniofacial complex during childhood and adolescence. The purpose of this paper is to describe the extent of this variation between traits and between individuals within the Fels Longitudinal Study. Polynomial multilevel models were used to estimate the ages of onset, peak velocity, and cessation of adolescent growth, the time between these ages, the amount of growth between these ages, and peak velocity. This was done at both the group and individual levels for standard cephalometric measurements of the lengths of the mandible, maxilla, and cranial base, the gonial angle, and the saddle angle. Data are from 293 untreated boys and girls age 4 to 24 years in the Fels Longitudinal Study. The timing of the adolescent growth spurt was, in general, not significantly different between the mandible and the maxilla, with each having an earlier age of onset, later age of peak velocity, and later age of cessation of growth compared to the cranial base length. Compared to lengths, angles had in general later ages of onset, peak velocity, and cessation of growth. Accurate characterization of the ontogenetic trajectories of the traits in the craniofacial complex is critical for both clinicians seeking to optimize treatment timing and anatomists interested in examining heterochrony. PMID:24737730

  10. Evolution of longitudinal modes in low voltage FEL

    SciTech Connect

    Stuart, R.A.; Al-Shamma`a, A.; Shaw, A.

    1995-12-31

    A low voltage FEL operating at 130 kV which can be run cw with a continuous electron beam current level up to 12 mA has been constructed for the X-Band microwave range (8-12 GHz). In this poster, we will report on the dependence on time, after the electron beam is switched on, of the growth and competition of those longitudinal modes in the cavity having nett gain.

  11. Variation in timing, duration, intensity, and direction of adolescent growth in the mandible, maxilla, and cranial base: the Fels longitudinal study.

    PubMed

    Nahhas, Ramzi W; Valiathan, Manish; Sherwood, Richard J

    2014-07-01

    There is considerable individual variation in the timing, duration, and intensity of growth that occurs in the craniofacial complex during childhood and adolescence. The purpose of this article is to describe the extent of this variation between traits and between individuals within the Fels Longitudinal Study (FLS). Polynomial multilevel models were used to estimate the ages of onset, peak velocity, and cessation of adolescent growth, the time between these ages, the amount of growth between these ages, and peak velocity. This was done at both the group and individual levels for standard cephalometric measurements of the lengths of the mandible, maxilla, and cranial base, the gonial angle, and the saddle angle. Data are from 293 untreated boys and girls age 4-24 years in the FLS. The timing of the adolescent growth spurt was, in general, not significantly different between the mandible and the maxilla, with each having an earlier age of onset, later age of peak velocity, and later age of cessation of growth as compared to the cranial base length. Compared to lengths, angles had in general later ages of onset, peak velocity, and cessation of growth. Accurate characterization of the ontogenetic trajectories of the traits in the craniofacial complex is critical for both clinicians seeking to optimize treatment timing and anatomists interested in examining heterochrony. © 2014 Wiley Periodicals, Inc.

  12. A changing pattern of childhood BMI growth during the 20th century: 70 y of data from the Fels Longitudinal Study123

    PubMed Central

    Johnson, William; Soloway, Laura E; Erickson, Darin; Choh, Audrey C; Lee, Miryoung; Chumlea, William C; Siervogel, Roger M; Czerwinski, Stefan A; Towne, Bradford

    2012-01-01

    Background: The BMI distribution shifted upward in the United States between the 1960s and the 1990s, but little is known about secular trends in the pattern of BMI growth, particularly earlier in the century and early in childhood. Objective: The objective was to examine differences in BMI growth in children born in 1929–1999. Design: BMI curves from ages 2 to 18 y were produced for 855 European-American children in the Fels Longitudinal Study born in 1929–1953, 1954–1972, and 1973–1999. Age (Amin) and BMI (BMImin) at adiposity rebound and age (AVmax), BMI (BMIVmax), and velocity (Vmax) at maximum velocity were derived; multivariable regression was used to examine whether maternal BMI, infant weight gain, and other covariates mediated the cohort effects on these traits. Results: BMI curves showed that children born in 1973–1999 had the lowest BMI values until age 5 y but had the largest values from age 8 y onward. In adjusted models, boys and girls born in 1973–1999 had a 0.15-kg/m2 per year faster Vmax and a 1-kg/m2 higher BMIVmax than did children of the same sex born in 1929–1953, and girls had a 0.8-y earlier Amin (P < 0.01). Maternal BMI and infant weight gain were associated with an obesity-prone pattern of BMI growth but did not account for the observed trends. Conclusions: Shifts in the BMI growth rate around the time of pubertal initiation were apparent starting after 1973. The BMI growth curve did not increase monotonically over time; rather, children born during the obesity epidemic were characterized by lower BMI values before the adiposity rebound and by rapid subsequent BMI gain. PMID:22418089

  13. A changing pattern of childhood BMI growth during the 20th century: 70 y of data from the Fels Longitudinal Study.

    PubMed

    Johnson, William; Soloway, Laura E; Erickson, Darin; Choh, Audrey C; Lee, Miryoung; Chumlea, William C; Siervogel, Roger M; Czerwinski, Stefan A; Towne, Bradford; Demerath, Ellen W

    2012-05-01

    The BMI distribution shifted upward in the United States between the 1960s and the 1990s, but little is known about secular trends in the pattern of BMI growth, particularly earlier in the century and early in childhood. The objective was to examine differences in BMI growth in children born in 1929-1999. BMI curves from ages 2 to 18 y were produced for 855 European-American children in the Fels Longitudinal Study born in 1929-1953, 1954-1972, and 1973-1999. Age (A(min)) and BMI (BMI(min)) at adiposity rebound and age (AV(max)), BMI (BMIV(max)), and velocity (V(max)) at maximum velocity were derived; multivariable regression was used to examine whether maternal BMI, infant weight gain, and other covariates mediated the cohort effects on these traits. BMI curves showed that children born in 1973-1999 had the lowest BMI values until age 5 y but had the largest values from age 8 y onward. In adjusted models, boys and girls born in 1973-1999 had a 0.15-kg/m(2) per year faster V(max) and a 1-kg/m(2) higher BMIV(max) than did children of the same sex born in 1929-1953, and girls had a 0.8-y earlier A(min) (P < 0.01). Maternal BMI and infant weight gain were associated with an obesity-prone pattern of BMI growth but did not account for the observed trends. Shifts in the BMI growth rate around the time of pubertal initiation were apparent starting after 1973. The BMI growth curve did not increase monotonically over time; rather, children born during the obesity epidemic were characterized by lower BMI values before the adiposity rebound and by rapid subsequent BMI gain.

  14. Optimization Studies of the FERMI at ELETTRA FEL Design

    SciTech Connect

    De Ninno, Giovanni; Fawley, William M.; Penn, Gregory E.; Graves,William

    2005-08-25

    The FERMI at ELETTRA project at Sincotrone Trieste involves two FEL's, each based upon the principle of seeded harmonic generation and using the existing ELETTRA injection linac at 1.2 GeV beam energy. Scheduled to be completed in 2008, FEL-1 will operate in 40-100 nm wavelength range and will involve one stage of harmonic up-conversion. The second undulator line, FEL-2, will begin operation two years later in the 10-40 nm wavelength range and use two harmonic stages operating as a cascade. The FEL design assumes continuous wavelength tunability over the full wavelength range, and polarization tunability of the output radiation including vertical or horizontal linear as well as helical polarization. The design considers focusing properties and segmentation of realizable undulators and available input seed lasers. We review the studies that have led to our current design. We present results of simulations using GENESIS and GINGER simulation codes including studies of various shot-to-shot fluctuations and undulator errors. Findings for the expected output radiation in terms of the power, transverse and longitudinal coherence are reported.

  15. Design study of a longer wavelength FEL for FELIX

    SciTech Connect

    Lin, L.; Oepts, D.; Meer, A.F.G. van der

    1995-12-31

    We present a design study of FEL3, which will extend the FELIX spectral range towards a few hundred microns. A rectangular waveguide will be used to reduce diffraction losses. Calculations show that with a waveguide gap of 1 cm, only one sinusoidal mode along the guided direction can exist within the FEL gain bandwidth, thus excluding group velocity dispersion and lengthening of short radiation pulses. To incorporate FEL3 in the existing FELIX facility, two options are being considered: to combine FEL3 with FEL1 by insertion of a waveguide into FEL1, and to build a dedicated third beam line for FEL3 after the two linacs. Expected FEL performance: gain, spectrum, power, pulse shape, etc., will be presented based on numerical simulations.

  16. The FERMI @ Elettra Technical Optimization Study: General Layoutand Parameters and Physics Studies of Longitudinal Space Charge, theSpreader, the Injector, and Preliminary FEL Performance

    SciTech Connect

    Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox,Russell; Wurtele, Jonathan; Zholents, Alexander

    2005-09-01

    The FERMI {at} Elettra facility will make use of the existing GeV linac at Sincrotrone Elettra, which will become available for dedicated FEL applications following the completion of construction of a new injector booster complex for the storage ring. With a new rf photocathode injector, and some additional accelerating sections, this linac will be capable of providing high brightness bunches at 1.2 GeV and up to 50 Hz repetition rates.

  17. Analysis of longitudinal bunching in an FEL driven two-beam accelerator

    SciTech Connect

    Lidia, S.; Gardelle, J.; Lefevre, T.; Donohue, J.T.; Gouard, P.; Rullier, J.L.; Vermare, C.

    2000-08-01

    Recent experiments have explored the use of a free-electron laser (FEL) as a buncher for a microwave two-beam accelerator, and the subsequent driving of a standing-wave rf output cavity. Here the authors present a deeper analysis of the longitudinal dynamics of the electron bunches as they are transported from the end of the FEL and through the output cavity. In particular, the authors examine the effect of the transport region and cavity aperture to filter the bunched portion of the beam.

  18. Electron beam effects in a UV FEL

    SciTech Connect

    Wong, R.K.; Blau, J.; Colson, W.B.

    1995-12-31

    At the Continuous Electron Beam Accelerator Facility (CEBAF), a free electron laser (FEL) is designed to produce ultraviolet (UV) light. A four-dimensional FEL simulation studies the effects of betatron oscillations, external focusing, and longitudinal pulse compression of the electron beam on the FEL performance.

  19. Non equilibrium studies on FEL facilities

    NASA Astrophysics Data System (ADS)

    Harmand, Marion

    2013-06-01

    The recent development of Free Electron Lasers (FEL), giving ultrafast, high intensity pulses in the X-ray and XUV energy range is opening new opportunities for WDM studies. Development of X-ray diagnostics such as X-ray absorption spectroscopy and X-ray scattering, has received much attention for the in situ measurement of the structure and physical properties of matter at extreme conditions. Coupled to ultrafast pump - probe schemas, such diagnostics are giving new insights into out-of-equilibrium processes and thus validate current models. We report recent developments to perform few fs time resolved pump - probe experiments, giving access to ultrafast transient WDM states. We also present collective Thomson Scattering with soft x-ray Free Electron Laser radiation (at FLASH) as a method to track the evolution of highly transient warm dense hydrogen with around 100 fs time resolution. In addition, recent experiments at LCLS are suggesting the possibility to perform X-ray absorption spectroscopy (XANES) on FEL facilities to provide simultaneously information on the valence electrons and on the atomic local arrangement within sub-ps time scales.

  20. LONGITUDINAL PHASE SPACE CHARACTERIZATION OF ELECTRON BUNCHES AT THE JLAB FEL FACILITY

    SciTech Connect

    Shukui Zhang; Stephen Benson; David Douglas; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

    We report longitudinal phase space measurements of short electron bunches at the 10kW Free-Electron Laser Facility at Jefferson Lab using broadband synchrotron radiation and a remotely controlled fast streak camera. Accurate measurements are possible because the optical transport system uses only reflective components that do not introduce dispersion. The evolution of longitudinal phase space of the electron beam can be observed in real time while phases of accelerator RF components are being adjusted. This fast and efficient diagnostic enhances the suite of machine setup tools available to JLab FEL operators and applies to other accelerators. The results for certain beam setups will be presented.

  1. FEL Design Studies at LBNL: Activities and Plans

    SciTech Connect

    Corlett, John N.; Fawley, W.; Lidia, S.; Padmore, H.; Penn, G.; Pogorelov, I.; Qiang, J.; Sannibale, F.; Staples, J.; Steier, C.; Venturini, M.; Wan, W.; Wilcox, R.; Zholents, A.

    2007-03-01

    LBNL staff are currently pursuing R&D for future x-ray FELs, and participate in two FEL construction projects. Our strategy is to address the most fundamental challenges, which are the cost-drivers and performance limitations of FEL facilities. An internally funded R&D program is aimed at investigating accelerator physics and technologies in three key areas: (1) Theoretical study, modeling, and experimental development of low emittance, high quantum efficiency cathodes; (2) Design studies of electron beam delivery systems, including emittance manipulations, high-resolution modeling of 6-D phase space, and low-emittance beam transport; and (3) Design studies of optical manipulations of electron beams for seeded and SASE FELs, providing short x-ray pulses of variable duration, synchronous with the seed and pump laser sources, and also long transform-limited pulses with a narrow bandwidth. Design studies of means for production of attosecond x-ray pulses at various wavelengths. We are collaborators in the FERMI{at}Elettra seeded FEL facility under construction at Sincrotrone Trieste, Italy, participating in accelerator design and FEL physics studies, and mechanical and electrical engineering. We are participating in the LCLS project at SLAC, implementing our design of stabilized timing and synchronization systems. Here we outline our long-term objectives, and current activities.

  2. Study of waveguide resonators for FEL operating at submillimeter wavelengths

    SciTech Connect

    Yakover, I.M.; Pinhasi, Y.; Gover, A.

    1995-12-31

    This paper presents theoretical results of waveguide resonator study for FEL operating at the submillimeter wavelength region. Because of increased ohmic losses it is harder to obtain high Q waveguide cavities at these wavelengths. The following unconventional multimode waveguides: metal-dielectric, corrugated and curved parallel plates, were considered. The type and structure of the operating modes were determined and their attenuation constant, effective mode area and wave impedance were calculated. On the basis of this analysis small-signal gain simulations were made. We have performed a parametric study of the various FEL oscillator cavity designs based on the parameters of the Israeli Tandem FEL experiment. It was found that an FEL utilizing unconventional waveguides has much better performance in comparison to an FEL based on conventional multimode rectangular and circular waveguides. In particular, promising design parameters for a sub-mm wavelength FEL utilizing a metal-dielectric waveguide were identified: gain of 45%/Amp and ohmic losses of 2% at frequency 300 GHz, and gain of 20%/Amp and ohmic losses 1% at frequency 675 GHz.

  3. THz wiggler applied for measurements of electron bunch longitudinal structure in FEL

    NASA Astrophysics Data System (ADS)

    Syresin, E.; Kostromin, S.; Krasilnikov, M.; Makarov, R.; Morozov, N.; Petrov, D.

    2015-01-01

    The infrared undulator manufactured at JINR and installed at FLASH in 2007 is used for longitudinal bunch shape measurements in the range of several tenths of a micrometer. The presented electromagnetic wiggler is intended for generating a narrow-band THz radiation to measure the longitudinal electron bunch structure in FELs with an electron energy of several tens of MeV. This is a planar electromagnetic device with six regular periods, each 30 cm long. The K parameter is varied in the range 0.5-7.12 corresponding to the range B = 0.025-0.356 T of the peak field on the axis. The wiggler is simulated for 19.8 MeV/ c corresponding to the possible FEL option at PITZ. The wavelength range is 126 μm - 5.1 mm for this electron beam momentum. The 3D Opera simulations of the THz wiggler are discussed. A new PITZ photocathode laser system is proposed for the optimized performance of the high-brightness electron beam. The main goal is a production of 3D ellipsoidal electron bunches with homogeneous charge density. The electromagnetic wiggler is supposed to be used for measuring the longitudinal shape of these electron bunches.

  4. BEAM OPTIMIZATION STUDY FOR AN X-RAY FEL OSCILLATOR AT THE LCLS-II

    SciTech Connect

    Qin, Weilun; Huang, S.; Liu, K.X.; Huang, Z; Ding, Y.; Maxwell, T.J.; Kim, K.-J.

    2016-06-01

    The 4 GeV LCLS-II superconducting linac with high repetition beam rate enables the possibility to drive an X-Ray FEL oscillator at harmonic frequencies *. Compared to the regular LCLS-II machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Also a flat longitudinal phase space distribution is critical to maintain the FEL gain since the X-ray cavity has extremely narrow bandwidth. In this paper, we study the longitudinal phase space optimization including shaping the initial beam from the injector and optimizing the bunch compressor and dechirper parameters. We obtain a bunch with a flat energy chirp over 400 fs in the core part with current above 100 A. The optimization was based on LiTrack and Elegant simulations using LCLS-II beam parameters.

  5. R&D Requirements, RF Gun Mode Studies, FEL-2 Steady-StateStudies, Preliminary FEL-1 Time-Dependent Studies, and Preliminary LayoutOption Investigation

    SciTech Connect

    Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox Russell; Wurtele, Jonathan; Zholents, Alexander

    2005-10-01

    This report constitutes the third deliverable of LBNLs contracted role in the FERMI {at} Elettra Technical Optimization study. It describes proposed R&D activities for the baseline design of the Technical Optimization Study, initial studies of the RF gun mode-coupling and potential effects on beam dynamics, steady-state studies of FEL-2 performance to 10 nm, preliminary studies of time-dependent FEL-1 performance using electron bunch distribution from the start-to-end studies, and a preliminary investigation of a configuration with FEL sinclined at a small angle from the line of the linac.

  6. Studies of Resistive Wall Heating at JLAB FEL

    SciTech Connect

    Li, Rui; Benson, Stephen V.

    2013-06-01

    When the JLAB FEL is under CW operation, it had been observed that temperature rises over the wiggler vacuum chamber, presumably as the result of the power deposition on the resistive wall of the wiggler chamber. Previous analyses have been done on the resistive wall impedance for various cases, such as DC, AC, and anomalous skin effects*. Here we report an investigation on the beam kinetic energy losses for each of these cases. This study includes the non-ultrarelativistic effect on resistive wall loss, for both round pipe and parallel plates. We will present the comparison of our results with the measured data obtained during CW operation of the JLAB FEL. Other possible factors contributing to the measured heating will also be discussed.

  7. Study of CSR Effects in the Jefferson Laboratory FEL Driver

    SciTech Connect

    Hall, C. C.; Biedron, S.; Burleson, Theodore A.; Milton, Stephen V.; Morin, Auralee L.; Benson, Stephen V.; Douglas, David R.; Evtushenko, Pavel E.; Hannon, Fay E.; Li, Rui; Tennant, Christopher D.; Zhang, Shukui; Carlsten, Bruce E.; Lewellen, John W.

    2013-08-01

    In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped.

  8. Progress at the Jefferson Laboratory FEL

    SciTech Connect

    Tennant, Christopher

    2009-01-01

    As the only currently operating free electron laser (FEL) based on a CW superconducting energy recovering linac (ERL), the Jefferson Laboratory FEL Upgrade remains unique as an FEL driver. The present system represents the culmination of years of effort in the areas of SRF technology, ERL operation, lattice design, high power optics and DC photocathode gun technology. In 2001 the FEL Demo generated 2.1 kW of laser power. Following extensive upgrades, in 2006 the FEL Upgrade generated 14.3 kW of laser power breaking the previous world record. The FEL Upgrade remains a valuable testbed for studying a variety of collective effects, such as the beam breakup instability, longitudinal space charge and coherent synchrotron radiation. Additionally, there has been exploration of operation with lower injection energy and higher bunch charge. Recent progress and achievements in these areas will be presented, and two recent milestones â installation of a UV FEL and establishment of a DC gun test s

  9. Parameter study of the VUV-FEL at the Tesla Test Facility

    SciTech Connect

    Brefeld, W.; Faatz, B.

    1995-12-31

    In this contribution we present a detailed study of the influence of the electron beam and machine parameters on the performance of the TTF VUV FEL, which is in its design stage at DESY. The TTF FEL will be a 6 nm SASE device operating with the beam provided by the Tesla Test Facility superconducting linac, driven by an rf photcathode gun. The FEL output power and saturation length have been assessed with the use of different 2D3-D steady state simulation codes. The parameter range over which the FEL would reach saturation within the specified undulator length of 25 to 30 m have been determined and checked against semi-analytical expressions.

  10. Coherence and linewidth studies of a 4-nm high power FEL

    NASA Astrophysics Data System (ADS)

    Fawley, W. M.; Sessler, A. M.; Scharlemann, E. T.

    1993-05-01

    Recently the SSRL/SLAC and its collaborators elsewhere have considered the merits of a 2 to 4-nm high power FEL utilizing the SLAC linac electron beam. The FEL would be a single pass amplifier excited by spontaneous emission rather than an oscillator, in order to eliminate the need for a soft X-ray resonant cavity. We have used GINGER, a multifrequency 2D FEL simulation code, to study the expected linewidth and coherence properties of the FEL, in both the exponential and saturated gain regimes. We present results concerning the effective shot noise input power and mode shape, the expected subpercent output line widths, photon flux, and the field temporal and spatial correlation functions. We also discuss the effects of tapering the wiggler upon the output power and line width.

  11. Coherence and linewidth studies of a 4-nm high power FEL

    SciTech Connect

    Fawley, W.M.; Sessler, A.M.; Scharlemann, E.T.

    1993-05-01

    Recently the SSRL/SLAC and its collaborators elsewhere have considered the merits of a 2 to 4-nm high power FEL utilizing the SLAC linac electron beam. The FEL would be a single pass amplifier excited by spontaneous emission rather than an oscillator, in order to eliminate the need for a soft X-ray resonant cavity. We have used GINGER, a multifrequency 2D FEL simulation code, to study the expected linewidth and coherence properties of the FEL, in both the exponential and saturated gain regimes. We present results concerning the effective shot noise input power and mode shape, the expected subpercent output line widths, photon flux, and the field temporal and spatial correlation functions. We also discuss the effects of tapering the wiggler upon the output power and line width.

  12. Emittance studies at the Los Alamos National Laboratory Free-Electron Laser (FEL)

    NASA Astrophysics Data System (ADS)

    Carlsten, B. E.; Feldman, D. W.; Lumpkin, A. H.; Stein, W. E.; Warren, R. W.

    Recent emittance studies at the Los Alamos Free-Electron Laser (FEL) have indicated several areas of concern in the linac and beamline feeding the wiggler. Four emittance growth mechanisms of special importance have been studied. First, a rapid growth of the electron beam's emittance immediately after the spherical gridded Pierce gun resulted, in part, from the long time required for our pulsing electronics to ramp the grid voltage up at the start and down at the end of the pulse, which created a pulse with a cosine-like current distribution as a function of time. The growth was compounded by the extremely small radial beam size (almost a waist) leaving the gun. In addition, we saw evidence of electrostatic charging of the insulators in the gun, reducing the quality of the electron beam further. Second, the action of the solenoidal focusing fields in the low-voltage bunching region was studied, and criteria for a minimum emittance growth were established. Third, maximum misalignment angles and displacements for various elements of the beamline were calculated for the desired low emittance growth. Finally, emittance growth in the horizontal dimension through the nonisochronous bend caused by varying energy depression on the particles due to longitudinal wake fields was both calculated and observed. In addition, we measured energy depressions caused by the wake fields generated by various other elements in the beamline. Strategies were developed to relieve the magnitude of these wake-field effects.

  13. The FEL and IFEL design study for the proposed NTHU photon-electron dynamics laboratory

    NASA Astrophysics Data System (ADS)

    Huang, Y. C.; Hsue, C. S.; Pantell, R. H.; Smith, T. I.

    1999-06-01

    A photon-electron dynamics laboratory is being proposed at National Tsinghua University, Taiwan. The mission of the proposed laboratory is to conduct advanced research on free-electron laser, inverse free-electron laser, and laser-driven particle acceleration. We discuss in this paper the design study of the Stanford high efficiency FEL and the reconfigured Stanford/TRW wiggler in the proposed laboratory. The Stanford high efficiency FEL is to demonstrate a 19% beam-to-laser efficiency. The reconfigured, 1-m Stanford/TRW wiggler may serve as an inverse FEL that provides 1.5-μm bunched electrons for various kinds of laser-driven acceleration experiments.

  14. Intrabeam Scattering in an X-ray FEL Driver

    SciTech Connect

    Huang, Z.

    2005-01-31

    Intrabeam scattering (IBS) of a high-brightness electron beam in an x-ray free-electron laser (FEL) driver is studied. Such a beam is much ''colder'' in the longitudinal direction than in transverse ones. As a result, the beam energy spread is increased with negligible change of transverse emittances. We estimate the IBS induced energy spread in the Linac Coherent Light Source and evaluate its effects on FEL and CSR microbunching instabilities.

  15. Transverse effects in UV FELs

    SciTech Connect

    Small, D.W.; Wong, R.K.; Colson, W.B.

    1995-12-31

    In an ultraviolet Free Electron Laser (UV FEL), the electron beam size can be approximately the same as the optical mode size. The performance of a UV FEL is studied including the effect of emittance, betatron focusing, and external focusing of the electron beam on the transverse optical mode. The results are applied to the Industrial Laser Consortium`s UV FEL.

  16. Numerical study of the 3-D effect on FEL performance and its application to the APS LEUTL FEL

    SciTech Connect

    Chae, Y.C.

    1998-09-01

    A Low-Energy Undulator Test Line (LEUTL) is under construction at the Advanced Photon Source (APS). In LEUTL periodic focusing is provided by external quadrupoles. This results in an elliptical beam with its betatron oscillation envelope varying along the undulators. The free-electron laser (FEL) interaction with such a beam will exhibit truly 3-D effects. Thus the investigation of 3-D effects is important in optimizing the FEL performance. The programs GINGER and TDA3D, coupled with theoretically known facts, have been used for this purpose. Both programs are fully 3-D in moving the particle, but model the interaction between particles and axially symmetric electromagnetic waves. Even though TDA3D can include a few azimuthal modes in the interaction, it is still not a fully 3-D FEL code. However, they show that these 2-D programs can still be used for an elliptical beam whose aspect ratio is within certain limits. The author presents numerical results of FEL performance for the circular beam, the elliptical beam, and finally for the beam in the realistic LEUTL lattice.

  17. Transverse-coherence properties of the FEL at the LCLS

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; Ocko, Samuel A.; /MIT, Cambridge, Dept. Phys.

    2010-09-02

    The recently commissioned Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is now operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources. Understanding of coherence properties of the radiation from SASE FELs at LCLS is of great practical importance for some user experiments. We present the numerical analysis of the coherence properties at different wavelengths based on a fast algorithmusing ideal and start-end simulated FEL fields. The sucessful commissioning and operation of the linac coherent light source (LCLS) [1] has demonstrated that the x-ray free-electron laser (FEL) has come of age; these types of x-ray sources are poised to revolutionize the ultra-fast x-ray sciences. The LCLS and other hard x-ray FELs under construction are based on the principle of self-amplified spontaneous emission (SASE) [2, 3], where the amplification process starts from the shot noise in the electron beam. A large number of transverse radiation modes are also excited when the electron beam enters the undulator. The FEL collective instability in the electron beam causes the modulation of the electron density to increase exponentially, and after sufficient undulator distances, a single transverse mode starts to dominate. As a result, SASE FEL is almost fully coherent in the transverse dimension. Understanding of transverse coherence properties of the radiation from SASE FELs is of great practical importance. The longitudinal coherence properties of SASE FELs have been studied before [4]. Some studies on the transverse coherence can be found in previous papers, for example, in ref. [5, 6, 7, 8, 9]. In this paper, we first discuss a new numerical algorithm based on Markov chain Monte Carlo techniques to calculate the FEL transverse coherence. Then we focus on the numerical analysis of the LCLS FEL transverse coherence.

  18. Studies of a Linac Driver for a High Repetition Rate X-Ray FEL

    SciTech Connect

    Venturini, M.; Corlett, J.; Doolittle, L.; Filippetto, D.; Papadopoulos, C.; Penn, G.; Prosnitz, D.; Qiang, J.; Reinsch, M.; Ryne, R.; Sannibale, F.; Staples, J.; Wells, R.; Wurtele, J.; Zolotorev, M.; Zholents, A.

    2011-06-01

    We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a pointdesign for a 1.8 GeV machine tuned for 300 pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.

  19. JINR test facility for studies FEL bunching technique for CLIC driving beam

    SciTech Connect

    Dolbilov, G.V.; Fateev, A.A.; Ivanov, I.N.

    1995-12-31

    SILUND-21 linear induction accelerator (energy up to 10 MeV, peak current about of 1 kA, pulse duration 50 - 70 ns) is constructed at JINR in the framework of experimental program to study free electron laser physics, a problem of two-beam acceleration and microwave electronics. In this paper we present project of an experiment to adopt the FEL bunching technique for generation of the CLIC driving beam.

  20. Primary experimental studies on mid-infrared FEL irradiation on dental substances at BFEL

    NASA Astrophysics Data System (ADS)

    Junbiao, Zhu; Yonggui, Li; Nianqing, Liu; Guoqing, Zhang; Minkai, Wang; Gan, Wu; Xuepin, Yan; Yuying, Huang; Wei, He; Yanmei, Dong; Xuejun, Gao

    2001-12-01

    A free electron laser (FEL) with its characteristics of wide wavelength tunability, ultrashort pulse time structure, and high peak power density is predominantly superior to all other conventional lasers in applications. Several experimental studies on mid-infrared FEL irradiation on dental enamel and dentine were performed at the Beijing FEL. Experimental aims were to investigate changes in the hardness, ratios of P to Ca and Cs before and after irradiation on samples with a characteristic absorption wavelength of 9.66 μm, in the colors of these sample surfaces after irradiation with different wavelengths around the peak wavelength. The time dependence of temperature of the dentine sample was measured with its ps pulse effects compared to that with a continuous CO 2 laser. FTIR absorption spectra in the range of 2.5-15.4 μm for samples of these hard dental substances and pure hydroxyapatite were first examined to decide their chemical components and absorption maximums. Primary experimental results will be presented.

  1. Tapered undulator for SASE FELs

    SciTech Connect

    Fawley, William M.; Huang, Zhirong; Kim, Kwang-Je; Vinokurov, Nikolai A.

    2001-09-14

    We discuss the use of tapered undulators to enhance the performance of free-electron lasers (FELs) based upon self-amplified spontaneous emission (SASE), where the radiation tends to have a relatively broad bandwidth, limited temporal phase coherence, and large amplitude fluctuations. Using the polychromatic FEL simulation code GINGER, we numerically demonstrate the effectiveness of a tapered undulator for parameters corresponding to the existing Argonne low-energy undulator test line (LEUTL) FEL. We also study possible tapering options for proposed x-ray FELs such as the Linac Coherent Light Source (LCLS).

  2. Two FEL`s in one

    SciTech Connect

    Epp, V.; Nikitin, M.

    1995-12-31

    A new scheme for a FEL operation is proposed. The conventional principle of FEL operation is means that the electron bunch passes through the interaction area of FEL only in one direction. We suggest another possible layout which implies that the electron bunch makes a turn after leaving the wiggler and entries the wiggler at the same end. Actually the wiggler is a kind of a bridge between two storage rings. The electron bunches on the orbit are expected to be adjusted in the way that after one of them leaves the wiggler, another one enters in the opposite direction and in the proper phase with the wave pulse emitted by the previous bunch. So the electron bunch comes in interaction with the amplified electromagnetic wave in both directions i.e. twice per period. It is especially important for the short wavelength FELs, because each reflection from the mirror causes a significant losses of the wave magnitude. The proposed design gives one interaction per each reflection instead of one interaction per two reflections in the traditional scheme. Another way to realize the suggested principle of operating is to insert the wiggler in the electron-positron storage ring. But this layout can be less efficient because of low intensity of the positron beam. The comparison study of radiation from different types of described double wigglers is fulfilled. The synchronization problems are discussed in this paper.

  3. Resonantly enhanced multiphoton ionization under XUV FEL radiation: a case study of the role of harmonics

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, G. M.; Lambropoulos, P.

    2015-12-01

    We provide a detailed quantitative study of the possible role of a small admixture of harmonics on resonant two-photon ionization. The motivation comes from the occasional presence of 2nd and 3rd harmonics in FEL radiation. We obtain the dependence of ionic yields on the intensity of the fundamental, the percentage of 2nd harmonic and the detuning of the fundamental from resonance. Having examined the cases of one and two intermediate resonances, we arrive at results of general validity and global behaviour, showing that even a small amount of harmonic may seem deceptively innocuous.

  4. Three-dimensional study of the multi-cavity FEL

    SciTech Connect

    Krishnagopal, S.; Kumar, V.

    1995-12-31

    The Multi-Cavity Free-Electron Laser has been proposed earlier, as a new configuration to obtain short, intense pulses of radiation, the key idea being to pre-bunch the electron beam in a number of very short cavities. Those studies were one-dimensional. Here we use three-dimensional simulations to study the viability of this concept when three-dimensional effects are included, particularly with regard to the transverse modes of the optical beam.

  5. Parameter Selection and Longitudinal Phase Space Simulation for a Single Stage X-Band FEL Driver at 250 MeV

    SciTech Connect

    Sun, Yipeng; Raubenheimer, Tor; Wu, Juhao; /SLAC

    2011-08-19

    Hard x-ray Free electron lasers (FEL) are being built or proposed at many accelerator laboratories as it supports wide range of applications in many aspects. Most of the hard x-ray FEL design is similar with the SLAC Linac Coherent Light Source (LCLS), which features a two (or multiple) stage bunch compression. For the first stage of the bunch compression, usually the beam is accelerated in a lower-frequency RF section (such as S-band for LCLS), and then the longitudinal phase space is linearized by a higher-frequency RF section (harmonic RF, such as X-band for LCLS). In this paper, a compact hard x-ray FEL design is proposed, which is based on X-band RF acceleration and eliminating the need of a harmonic RF. The parameter selection and relation is discussed, and the longitudinal phase space simulation is presented. The FEL coherence condition of the electron beam in the undulators requires a large charge density, a small emittance and small energy spread. The RMS electron bunch length from the injector is in the ps scale, with a bunch charge in the range of hundreds pC to several nC, which means that the current is roughly 0.1 kA. According to the requirement from soft x-ray lasing and hard x-ray lasing, a peak current of 1 kA and 3 kA is needed respectively. Thus the bunch has to be compressed. Usually a two stage bunch compression or multipole stage bunch compression is adopted. The z-correlated energy chirp is normally established by letting the beam pass through a section of RF cavities, with a RF phase off crest. As stated above, S-band RF (3 GHz) acceleration could be applied in this section. Due to the nature of RF acceleration wave, the chirp on the bunch is not linear, but has the RF curvature on it. In order to linearize the energy chirp, a harmonic RF section with higher frequency is needed. For LCLS a short X-band RF section (12 GHz) is used which is a fourth order harmonic. The linearized bunch is then passing by a dispersive region, in which the

  6. Sensitivity and alternative operating point studies on a high charge CW FEL injector test stand at CEBAF

    SciTech Connect

    Liu, H.; Kehne, D.; Benson, S.

    1995-12-31

    A high charge CW FEL injector test stand is being built at CEBAF based on a 500 kV DC laser gun, a 1500 MHz room-temperature buncher, and a high-gradient ({approx}10 MV/m) CEBAF cryounit containing two 1500 MHz CEBAF SRF cavities. Space-charge-dominated beam dynamics simulations show that this injector should be an excellent high-brightness electron beam source for CW UV FELs if the nominal parameters assigned to each component of the system are experimentally achieved. Extensive sensitivity and alternative operating point studies have been conducted numerically to establish tolerances on the parameters of various injector system components. The consequences of degraded injector performance, due to failure to establish and/or maintain the nominal system design parameters, on the performance of the main accelerator and the FEL itself are discussed.

  7. GATB LONGITUDINAL MATURATION STUDY.

    ERIC Educational Resources Information Center

    DROEGE, ROBERT C.

    THIS ARTICLE DESCRIBES RESULTS OF THE FIRST IN A SERIES OF THREE LARGE-SCALE LONGITUDINAL STUDIES CONDUCTED BY THE U.S. EMPLOYMENT SERVICE TO INCREASE THE USEFULNESS OF THE GENERAL APTITUDE TEST BATTERY (GATB) FOR COUNSELING HIGH SCHOOL STUDENTS. THE FINAL SAMPLE CONSISTED OF 26,708 HIGH SCHOOL STUDENTS. ALL WERE TESTED WITH THE GATB IN 1958, AND…

  8. FEL Oscillators

    SciTech Connect

    George Neil

    2003-05-12

    FEL Oscillators have been around since 1977 providing not only a test bed for the physics of Free Electron Lasers and electron/photon interactions but as a workhorse of scientific research. More than 30 FEL oscillators are presently operating around the world spanning a wavelength range from the mm region to the ultraviolet using DC and rf linear accelerators and storage rings as electron sources. The characteristics that have driven the development of these sources are the desire for high peak and average power, high micropulse energies, wavelength tunability, timing flexibility, and wavelengths that are unavailable from more conventional laser sources. Substantial user programs have been performed using such sources encompassing medicine, biology, solid state research, atomic and molecular physics, effects of non-linear fields, surface science, polymer science, pulsed laser vapor deposition, to name just a few.

  9. High quality electron beams for high quality FEL

    NASA Astrophysics Data System (ADS)

    Allaria, E.

    2017-05-01

    Thanks to the use of seeding, modern high gain FELs can now produce high power pulses with a longitudinal coherence much higher than normally available from SASE FELs. This possibility of fully coherent FEL pulses in the X-ray spectral range has several benefits for user's experiment and also it opens the door to new experimental possibilities such as coherent control experiments. The achievement of a full coherence in the FEL pulses does not only requires a coherent seed but also needs an electron beam whose properties does not change over the length of the final FEL pulse. For this reason, requirements for electron beam quality in seeded FELs are significantly higher than for SASE FEL. Starting from the FERMI experience we report in the talk examples of small electron beam perturbations that have a large impact on FEL properties.

  10. Performance study of a soft X-ray harmonic generation FEL seededwith an EUV laser pulse

    SciTech Connect

    Gullans, M.; Wurtele, J.S.; Penn, G.; Zholents, A.A.

    2007-02-01

    The performance of a free electron laser (FEL) using alow-power extreme ultraviolet (EUV) pulse as an input seed isinvestigated. The parameters are appropriate for 30 nm seeds producedfrom high-power Ti:Sa pulses using high harmonic generation schemes. Itis found that, for reasonable beam parameters, robust FEL performance canbe obtained. Both time-independent and time-dependent simulations areperformed for varying system parameters using the GENESIS simulationcode. A comparison is made with a two-stage harmonic FEL that is seededby a high-power Ti:Sa pulse.

  11. The Stanford Picosecond FEL Center

    SciTech Connect

    Schwettman, H.A.; Smith, T.I.; Swent, R.L.

    1995-12-31

    In the past two years, FELs have decisively passed the threshold of scientific productivity. There are now six FEL facilities in the United States and Europe, each delivering more than 2000 hours of FEL beam time per year. at the present time approximately 100 papers are published each in referred journals describing optics experiments performed with FELs. Despite the recent success there are important challenges the FEL facilities must address. At Stanford these challenges include: (1) Providing sufficient experimental time at reasonable cost: At Stanford we provide 2000 hours of experimental time per year at a cost of approximately $500 per hour: We are now studying options for markedly increasing experimental time and decreasing cost per hour. (2) Competing effectively with conventional lasers in the mid-IR: Despite the NRC report we do not intend to concede the mid-IR to conventional lasers. FELs are capable of providing optical beams of exceptional quality and stability, and they can also be remarkable flexible devices. Improvements in our superconducting linac driver and our optical beam conditioning systems will dramatically enhance our FEL experimental capabilities. (3) making the transition from first generation to second generation experiments: Important pump-probe and photon echo experiments have been performed at Stanford and others are feasible using present capabilities. None-the-less we are now investing substantial experimental time to improving signal-to-noise and developing other optical cababilities. (4) Extending operation to the far-infrared where the FEL is unique inits capabilities: {open_quotes}FIREFLY{close_quotes} will extend our FEL capabilities to 100 microns. We are now seeking funds for optical instrumentation. (5) Creating and maintaining a good environment for graduate students.

  12. Electron bunch length measurement at the Vanderbilt FEL

    SciTech Connect

    Amirmadhi, F.; Brau, C.A.; Mendenhall, M.

    1995-12-31

    During the past few years, a number of experiments have been performed to demonstrate the possibility to extract the longitudinal charge distribution from spectroscopic measurements of the coherent far-infrared radiation emitted as transition radiation or synchrotron radiation. Coherent emission occurs in a spectral region where the wavelength is comparable to or longer than the bunch length, leading to an enhancement of the radiation intensity that is on the order of the number of particles per bunch, as compared to incoherent radiation. This technique is particularly useful in the region of mm and sub-mm bunch lengths, a range where streak-cameras cannot be used for beam diagnostics due to their limited time resolution. Here we report on experiments that go beyond the proof of principle of this technique by applying it to the study and optimization of FEL performance. We investigated the longitudinal bunch length of the Vanderbilt FEL by analyzing the spectrum of coherent transition radiation emitted by the electron bunches. By monitoring the bunch length while applying a bunch-compression technique, the amount of the compression could be easily observed. This enabled us to perform a systematic study of the FEL performance, especially gain and optical pulse width, as a function of the longitudinal electron distribution in the bunch. The results of this study will be presented and discussed.

  13. Beam Dynamics Study of X-Band Linac Driven X-Ray FELS

    SciTech Connect

    Adolphsen, C.; Limborg-Deprey, C.; Raubenheimer, T.O.; Wu, J.; Sun, Y.; /SLAC

    2011-12-13

    Several linac driven X-ray Free Electron Lasers (XFELs) are being developed to provide high brightness photon beams with very short, tunable wavelengths. In this paper, three XFEL configurations are proposed that achieve LCLS-like performance using X-band linac drivers. These linacs are more versatile, efficient and compact than ones using S-band or C-band rf technology. For each of the designs, the overall accelerator layout and the shaping of the bunch longitudinal phase space are described briefly. During the last 40 years, the photon wavelengths from linac driven FELs have been pushed shorter by increasing the electron beam energy and adopting shorter period undulators. Recently, the wavelengths have reached the X-ray range, with FLASH (Free-Electron Laser in Hamburg) and LCLS (Linac Coherent Light Source) successfully providing users with soft and hard X-rays, respectively. FLASH uses a 1.2 GeV L-band (1.3 GHz) superconducting linac driver and can deliver 10-70 fs FWHM long photon pulses in a wavelength range of 44 nm to 4.1 nm. LCLS uses the last third of the SLAC 3 km S-band (2.856 GHz) normal-conducting linac to produce 3.5 GeV to 15 GeV bunches to generate soft and hard X-rays with good spatial coherence at wavelengths from 2.2 nm to 0.12 nm. Newer XFELs (at Spring8 and PSI) use C-band (5.7 GHz) normal-conducting linac drivers, which can sustain higher acceleration gradients, and hence shorten the linac length, and are more efficient at converting rf energy to bunch energy. The X-band (11.4 GHz) rf technology developed for NLC/GLC offers even higher gradients and efficiencies, and the shorter rf wavelength allows more versatility in longitudinal bunch phase space compression and manipulation. In the following sections, three different configurations of X-band linac driven XFELs are described that operate from 6 to 14 GeV. The first (LOW CHARGE DESIGN) has an electron bunch charge of only 10 pC; the second (OPTICS LINEARIZATION DESIGN) is based on optics

  14. Transport studies of LPA electron beam towards the FEL amplification at COXINEL

    NASA Astrophysics Data System (ADS)

    Khojoyan, M.; Briquez, F.; Labat, M.; Loulergue, A.; Marcouillé, O.; Marteau, F.; Sharma, G.; Couprie, M. E.

    2016-09-01

    Laser Plasma Acceleration (LPA) [1] is an emerging concept enabling to generate electron beams with high energy, high peak current and small transverse emittance within a very short distance. The use of LPA can be applied to the Free Electron Laser (FEL) [2] case in order to investigate whether it is suitable for the light amplification in the undulator. However, capturing and guiding of such beams to the undulator is very challenging, because of the large divergence and high energy spread of the electron beams at the plasma exit, leading to large chromatic emittances. A specific beam manipulation scheme was recently proposed for the COXINEL (Coherent X-ray source inferred from electrons accelerated by laser) setup, which makes an advantage from the intrinsically large chromatic emittance of such beams [3]. The electron beam transport is studied using two simulation codes: a SOLEIL in-house one and ASTRA [4]. The influence of the collective effects on the electron beam performance is also examined.

  15. Theoretical study of the design and performance of a high-gain, high-extraction-efficiency FEL oscillator

    SciTech Connect

    Goldstein, J.; Nguyen, D.C.; Sheffield, R.L.

    1996-10-01

    We present the results of theoretical and simulation studies of the design and performance of a new F type of FEL oscillator. This device, known by the acronym RAFEL for Regenerative Amplifier Free-Electron Laser, will be constructed in the space presently occupied by the AFEL (Advanced FEL) at Los Alamos, and will be driven by an upgraded (to higher average power) version of the present AFEL linac. In order to achieve a long-time-averaged optical output power of {approximately} 1 kW using an electron beam with an average power of {approximately} 20 kW, a rather high extraction efficiency {eta} {approximately} 5% is required. We have designed a 2-m-long undulator to attain this goal: the first meter is untapered and provides high gain while the second meter is linearly-tapered in magnetic field amplitude to provide high extraction efficiency in the standard K-M-R manner. Two-plane focusing and linear polarization of the undulator are assumed. Electron-beam properties from PARMEIA simulations of the AFEL accelerator were used in the design. A large saturated gain, {approximately} 500, requires a very small optical feedback to keep the device operating at steady-state. However, the large gain leads to distorted optical modes which require two- and three-dimensional simulations to adequately treat diffraction effects. This FEL will be driven by 17 MeV electrons and will operate in the 16 {mu}m spectral region.

  16. Microbunching Instability Effect Studies and Laser Heater Optimization for the SPARX FEL Accelerator

    SciTech Connect

    Vaccarezza, C.; Chiadroni, E.; Ferrario, M.; Giannessi, L.; Quattromini, M.; Ronsivalle, C.; Venturini, C.; Migliorati, M.; Dattoli, G.

    2010-05-23

    The effects of microbunching instability for the SPARX accelerator have been analyzed by means of numerical simulations. The laser heater counteracting action has been addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.

  17. OCELOT: A software framework for synchrotron light source and FEL studies

    NASA Astrophysics Data System (ADS)

    Agapov, I.; Geloni, G.; Tomin, S.; Zagorodnov, I.

    2014-12-01

    OCELOT is a novel multiphysics simulation toolkit, which has been in development at European XFEL in collaboration with NRC Kurchatov Institute and DESY since 2011. In this paper we describe its architecture, implementation, and applications in the area of synchrotron light sources and FELs.

  18. Studies for a beam trajectory monitor for TTF-FEL at DESY

    SciTech Connect

    Mueller, Ute Carina

    1997-06-01

    A beam trajectory monitor for the FEL at the TESLA test facility at DESY has been proposed for the reconstruction of the electron beam trajectory by observing the spontaneous undulator radiation along the beam using the pinhole camera principle. Simulations for this concept have been performed and results are presented here.

  19. Simulations of the LANL regenerative amplifier FEL

    SciTech Connect

    Kesselring, M.; Colson, W.B.; Wong, R.K.; Sheffield, R.L.

    1997-08-01

    The LANL regenerative amplifier FEL is designed to produce an average output power of 1 kW. Simulations study the transverse effects due to guiding by the intense electron beam and feedback. These simulations coupled with experimental measurements can be used to improve future high-power FEL designs.

  20. Detailed numerical studies of space charge effects in an FEL RF gun

    NASA Astrophysics Data System (ADS)

    Cee, R.; Krassilnikov, M.; Setzer, S.; Weiland, T.; Novokhatski, A.

    2002-05-01

    The production of short bunches with low emittance is a key issue for the successful operation of an SASE-FEL as proposed by the TESLA collaboration (TESLA Technical design report, DESY 2001-011, Hamburg, 2001). In this paper we present the results of detailed MAFIA TS-2 (CST GmbH, Büdinger Strasse 2a, D-64289 Darmstadt) simulations for the FEL RF-gun revealing the main physical effects leading to emittance growth. The simulations prove that the transverse emittance growth can mainly be observed close to the cathode area. This is caused by the non-linear space charge forces acting inside the bunch during the injection process. For the application of an emittance compensation scheme (Nucl. Instr. and Meth. 285 (1989) 313) the slice emittance is of significant importance. Therefore, a wide range of parameters for the photo cathode laser has been investigated in order to find an appropriate operation point.

  1. An experimental study of an FEL oscillator with a linear taper

    NASA Astrophysics Data System (ADS)

    Benson, S.; Gubeli, J.; Neil, G. R.

    2001-12-01

    Motivated by the work of Saldin, Schneidmiller and Yurkov, we have measured the detuning curve widths, spectral characteristics, efficiency, and energy spread as a function of the taper for low and high Q resonators in the IR Demo FEL at Jefferson Lab. Both positive and negative tapers were used. Gain and frequency agreed surprisingly well with the predictions of a single mode theory. The efficiency agreed reasonably well for a negative taper with a high Q resonator but disagreed for lower Q values both due to the large slippage parameter and the non-ideal resonator Q. We saw better efficiency for a negative taper than for the same positive taper. The energy spread induced in the beam, normalized to the efficiency is larger for the positive taper than for the corresponding negative taper. This indicates that a negative taper is preferred over a positive taper in an energy recovery FEL.

  2. Design Studies for a High-Repetition-Rate FEL Facility at LBNL.

    SciTech Connect

    CORLETT, J.; BELKACEM, A.; BYRD, J. M.; FAWLEY, W.; KIRZ, J.; LIDIA, S.; MCCURDY, W.; PADMORE, H.; PENN, G.; POGORELOV, I.; QIANG, J.; ROBIN, D.; SANNIBALE, F.; SCHOENLEIN, R.; STAPLES, J.; STEIER, C.; VENTURINI, M.; WAN, W.; WILCOX, R.; ZHOLENTS, A.

    2007-10-04

    Lawrence Berkeley National Laboratory (LBNL) is working to address the needs of the primary scientific Grand Challenges now being considered by the U.S. Department of Energy, Office of Basic Energy Sciences: we are exploring scientific discovery opportunities, and new areas of science, to be unlocked with the use of advanced photon sources. A partnership of several divisions at LBNL is working to define the science and instruments needed in the future. To meet these needs, we propose a seeded, high-repetition-rate, free-electron laser (FEL) facility. Temporally and spatially coherent photon pulses, of controlled duration ranging from picosecond to sub-femtosecond, are within reach in the vacuum ultraviolet (VUV) to soft X-ray regime, and LBNL is developing critical accelerator physics and technologies toward this goal. We envision a facility with an array of FELs, each independently configurable and tunable, providing a range of photon-beam properties with high average and peak flux and brightness.

  3. Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory

    SciTech Connect

    Tochitsky, S. Ya.; Musumeci, P.; Rosenzweig, J. B.; Joshi, C.; Gottschalk, S. C.

    2010-11-04

    Seeded high-gain FELs, which can generate very powerful radiation pulses in a relatively compact undulator and simultaneously modulate the electron beam longitudinally at the seed wavelength, are important tools for advanced accelerator development. A single-pass 0.5-9 THz FEL amplifier-buncher driven by a regular photoinjector is being built at the UCLA Neptune Laboratory. FEL interactions at 340 {mu}m (1 THz) are considered for the first experiment, since time-resolved measurements of longitudinal current distribution of the bunched beam using the RF deflecting cavity are possible. A design of a 0.2-2.0 {mu}m FEL using the same undulators is presented. In this case the FEL is driven by a high-peak current beam from the laser-plasma accelerator tunable in the 100-300 MeV range.

  4. COMPARISON OF TWO DIFFERENT WAVELENGTH TUNING SCHEMES IN A SEEDED HIGH-GAIN FEL.

    SciTech Connect

    SHAFTAN,T.; YU,L.H.

    2004-08-04

    In the following text we analyze and compare results of the two publications ([1], [2]), dedicated to development of the tunable high-gain Free Electron laser (FEL), seeded by an external source. As a conclusion we summarize similarities and differences between these concepts. This note is initiated by the polemics on the similarity of two different schemes of the wavelength tuning in a seeded high-gain FEL. Below we will be calling the scheme, presented by S. Biedron, S, Milton and H. Freund in Nuclear Instruments and Methods of 2001 ([1]), as the first (1st) scheme. The scheme that we developed and presented in the BNL preprint ([2]) will be called as the second (2nd) scheme. The following analysis provides important information on similarities and differences between both techniques. We start by considering the first approach. As we understand, the goal of the Modular Approach is to make X-ray FEL design more flexible [1]. Usual linac-based FELs begin from a long linac with bunch compressor(s) followed by an FEL magnetic system. The essence of the Modular Approach is to break a machine into modules and then recombine these modules in a more efficient way (from the point of view of monetary and/or time constraints). The chapter 3.5 of [1] presents some basic example of Modular Approach. We have studied the scheme, discussed in [1] and illustrated in Fig. 2. Even though very few details of the scheme were presented, it was still sufficient to obtain a complete qualitative picture. Let us begin with the usual phase space of the microbunched beam, which enters a radiator in a prebunched FEL (Fig. 1). The sharp spike (in blue) represents the longitudinal density bunching, which will be the main subject of interest in this discussion. The key principle of a seeded high-gain FEL optimization is to establish this kind of the electron beam phase space at the entrance of the radiator.

  5. Innovative FEL schemes using variable-gap undulators

    NASA Astrophysics Data System (ADS)

    Schneidmiller, E. A.; Yurkov, M. V.

    2017-06-01

    We discuss theoretical background and experimental verification of advanced schemes for X-ray FELs using variable gap undulators (harmonic lasing self-seeded FEL, reverse taper etc.) Harmonic lasing in XFELs is an opportunity to extend operating range of existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental. Another interesting application of harmonic lasing is Harmonic Lasing Self-Seeded (HLSS) FEL that allows to improve longitudinal coherence and spectral power of a SASE FEL. Recently this concept was successfully tested at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. That was also the first experimental demonstration of harmonic lasing in a high-gain FEL and at a short wavelength (before it worked only in infrared FEL oscillators). Another innovative scheme that was tested at FLASH2 is the reverse tapering that can be used to produce circularly polarized radiation from a dedicated afterburner with strongly suppressed linearly polarized radiation from the main undulator. This scheme can also be used for an efficient background-free production of harmonics in an afterburner. Experiments on the frequency doubling that allowed to reach the shortest wavelength at FLASH as well as on post-saturation tapering to produce a record intencity in XUV regime are also discussed.

  6. FULL ELECTROMAGNETIC FEL SIMULATION VIA THE LORENTZ-BOOSTED FRAME TRANSFORMATION

    SciTech Connect

    Fawley, William; Vay, Jean-Luc

    2010-08-16

    Numerical electromagnetic simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz-boosted frame. A particularly good application for calculation in a boosted frame isthat of short wavelength free-electron lasers (FELs) where a high energy electron beam with small fractional energy spread interacts with a static magnetic undulator. In the optimal boost frame (i.e., the ponderomotive rest frame), the red-shifted FEL radiation and blue-shifted undulator field have identical wavelengths and the number of required longitudinal grid cells and time-steps for fully electromagnetic simulation (relative to the laboratory frame) decrease by factors of gamma^2 each. In theory, boosted frame EM codes permit direct study of FEL problems for which the eikonal approximation for propagation of the radiation field and wiggler-period-averaging for the particle-field interaction may be suspect. We have adapted the WARP code to apply this method to several electromagnetic FEL problems including spontaneous emission, strong exponential gain in a seeded, single pass amplifier configuration, and emission from e-beams in undulators with multiple harmonic components. WARP has a standard relativistic macroparticle mover and a fully 3-D electromagnetic field solver. We discuss our boosted frame results and compare with those obtained using the ?standard? eikonal FEL simulation approach.

  7. Temporal and spectral evolution of a storage ring FEL source: Experimental results on Super-ACO and new theoretical approach

    SciTech Connect

    Hara, T.; Couprie, M.E. ||

    1995-12-31

    The Super-ACO FEL source in UV is now used for applications like a time-resolved fluorescence in biology and two colors experiments coupling FEL and Synchrotron Radiation, which are naturally synchronized. The stability of the FEL is then a critical issue for the users. Detailed experimental studies conducted on the temporal characteristics of the laser micropulse showed various phenomena, such as a longitudinal micropulse jitter and a deformation of a longitudinal micropulse distribution. A similar analysis has been performed on the laser spectral evolution with a scanning Fabry-Perot interferometer, showing a spectrum narrowing, and a wavelength drift. A longitudinal feedback system developed after the first user experiment, allowed to reduce significantly the longitudinal jitter, the intensity fluctuation and the spectral drift. Nevertheless, the stability of the FEL is very dependent on any perturbation, and the observed phenomena can not be described by former models like super-mode assuming a stationary regime. A new theoretical model has then been developed, in order to simulate dynamic behaviors. A simple iterative method is employed to obtain the laser spectrum. The access to the temporal distribution requires additional complexity, because the Fourier transformation has to be performed for each pass. The comparison between the experimental data and the simulation results will be given.

  8. The Importance of Longitudinal Studies

    NASA Astrophysics Data System (ADS)

    Knezek, Patricia

    2014-01-01

    It has been eight years since the AAS Council unanimously endorsed the document, known as "Equity Now: The Pasadena Recommendations for Gender Equality in Astronomy," in January 2005. This document was the main product of the conference entitled “Women in Astronomy II: Ten Years After” (WIA II), held in June 2003 in Pasadena, CA. One of the key recommendations represented in that document was the need for a longitudinal study of astronomers. It was recognized that in order to understand our own field, how it is evolving, and the impact on individuals, we need to track people over time. I will discuss the fundamental questions that led to the recommendation, and set the stage for the current (ongoing) longitudinal study.

  9. SASE FEL Polarization Control Using Crossed Undulator

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; /SLAC

    2008-09-30

    There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

  10. Multidimensional simulation studies of the SELENE FEL oscillator/buncher followed by a radiator/amplifier output scheme

    SciTech Connect

    Hahn, S.J.; Fawley, W.M.

    1995-02-01

    We analyze and present numerical simulations of the so-called electron output scheme [G. I. Erg et al., 15th Int. FEL Conf., The Hague, The Netherlands, 1993, Book of Abstracts p. 50; Preprint Budker INP 93-75] applied to the SELENE proposal of using a high power FEL to illuminate satellite solar cells. In this scheme, a first stage FEL oscillator bunches the electron beam while a second stage ``radiator`` extracts high power radiation. Our analysis suggests only in the case where the radiator employs a long, tapered undulator will the electron output scheme produce a significant increase in extraction efficiency over what is obtainable from a simple, single-stage oscillator. 1- and 2-D numerical simulations of a 1.7{mu}m FEL employing the electron output scheme show reasonably large bunching fractions ({approximately} 0.3--0.4) at the output of the oscillator stage but only {le}2% extraction efficiency from the radiator stage.

  11. Design study of the bending sections between harmonic cascade FEL stages

    SciTech Connect

    Wan, Weishi; Corlett, John; Fawley, William; Zholents, A.

    2004-06-30

    The present design of LUX (linac based ultra-fast X-ray facility) includes a harmonic cascade FEL chain to generate coherent EUV and soft X-ray radiation. Four cascade stages, each consisting of two undulators acting as a modulator and a radiator, respectively, are envisioned to produce photons of approximate wavelengths 48 nm, 12 nm, 4 nm and 1 nm. Bending sections may be placed between the modulator and the radiator of each stage to adjust and maintain bunching of the electrons, to separate, in space, photons of different wavelengths and to optimize the use of real estate. In this note, the conceptual design of such a bending section, which may be used at all four stages, is presented. Preliminary tracking results show that it is possible to maintain bunch structure of nm length scale in the presence of errors, provided that there is adequate orbit correction and there are 2 families of trim quads and trim skew quads, respectively, in each bending section.

  12. Ther FERMI FEL project at TRIESTE

    SciTech Connect

    Walker, R.P.; Bulfone, D.; Cargnello, F.

    1995-12-31

    The goal of the FERMI project - Free Electron Radiation and Matching Instrumentation - is to construct a new user facility for FEL radiation beams covering a broad spectral range (2-250 {mu}m) to complement the high brightness VUV/Soft-Xray radiation available from the ELETTRA synchrotron radiation facility at Trieste. A unique feature of the project will be the possibility of carrying out {open_quote}pump-probe{close_quote} experiments using synchronized radiation beams from FERMI and ELETTRA on the same sample. The project was launched at a meeting with Italian FEL experts held in Trieste on the 18th November 1994, chaired by C. Rubbia, as a collaboration between Sincrotrone Trieste, ENEA (Frascati), INFN (Frascati) and the University of Naples (Department of Electronic Engineering). The facility will make use of an existing linac, that forms part of the ELETTRA injection system, and a hall into which the beam can be extracted. In addition, for the first phase of the project equipment will be used from the suspended INFN/ENEA {open_quote}SURF{close_quote} FEL experiment, including the undulator, beam transport magnets and optical cavity. In this first International FEL Conference report on the project, we summarize the main features of the project, concentrating in particular on the most recent activities, including: results of measurements of the linac beam in the FEL mode of operation, further studies of the electron beam transport system including possibilities for bunch length manipulations, and further numerical calculations of the FEL performance.

  13. SOFT X-RAY FEL BY CASCADING STAGES OF HIGH GAIN HARMONIC GENERATION.

    SciTech Connect

    YU,L.H.

    2003-04-17

    Short wavelength Free-Electron Lasers are perceived as the next generation of synchrotron light sources. In the past decade, significant advances have been made in the theory and technology of high brightness electron beams and single pass FELs. These developments facilitate the construction of practical VUV FELs and make x-ray FELs possible. Self-Amplified Spontaneous Emission (SASE) and High Gain Harmonic Generation (HGHG)[17-19] are the two leading candidates for x-ray FELs. The first lasing of HGHG proof-of-principle experiment succeeded in August, 1999 in Brookhaven National Laboratory. The experimental results agree with the theory prediction. Compared with SASE FEL, the following advantages of HGHG FEL were confirmed; (1) Better longitudinal coherence, and hence, much narrower bandwidth than SASE. (2) More stable central wavelength, (3) More stable output energy. In this introduction, we will first briefly describe the principle of HGHG in Section A. Then in Section B, we give a general description about how to produce soft x-ray by cascading HGHG scheme. In section 2, we give a detailed description of the system design. Then, in section 3, we give a description of an analytical estimate for the HGHG process, and the calculation of the parameters of different parts of the system. The estimate is found to agree with simulation within about a factor 2 for most cases we studied. The stability issue, the sensitivity to parameter variation, the harmonic contents of the final output, and the noise degradation issue of such HGHG scheme are discussed in Section 4. The results are presented in Section 4. Finally, in Section 5, we will give some discussion of the challenges in development of the system. The conclusion is given in Section 6.

  14. Optical Klystron Enhancement to SASE X-ray FELs

    SciTech Connect

    Ding, Yuantao; Emma, Paul; Huang, Zhirong; Kumar, Vinit

    2006-04-07

    The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 A) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a shorter-period undulator.

  15. Nonlinear harmonic generation and proposed experimental verification in SASE FELs.

    SciTech Connect

    Biedron, S. G.; Freund, H. P.; Milton, S. V.

    1999-08-24

    Recently, a 3D, polychromatic, nonlinear simulation code was developed to study the growth of nonlinear harmonics in self-amplified spontaneous emission (SASE) free-electron lasers (FELs). The simulation was applied to the parameters for each stage of the Advanced Photon Source (APS) SASE FEL, intended for operation in the visible, UV, and short UV wavelength regimes, respectively, to study the presence of nonlinear harmonic generation. Significant nonlinear harmonic growth is seen. Here, a discussion of the code development, the APS SASE FEL, the simulations and results, and, finally, the proposed experimental procedure for verification of such nonlinear harmonic generation at the APS SASE FEL will be given.

  16. Sex differences in the rate of abdominal adipose accrual during adulthood: the Fels Longitudinal Study

    PubMed Central

    Whitaker, Kara M.; Choh, Audrey C.; Lee, Miryoung; Towne, Bradford; Czerwinski, Stefan A.; Demerath, Ellen W.

    2016-01-01

    Objectives The purpose of this analysis was to evaluate sex differences in the rate of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) accrual in adults. Secondary analyses examined differences in the rate of VAT and SAT accrual in pre-, peri-, and post-menopausal women. Subjects/Methods Participants were 472 (60% female) non-Hispanic whites, aged 18-84 years at baseline in whom abdominal VAT and SAT were assessed using multiple-image magnetic resonance imaging at two time points, with an average follow-up of 7.3 ± 2.6 years. Linear regression models were used to examine the effects of sex, baseline age and their interaction on rate of change per year in body composition measures (ΔBMI, ΔVAT, and ΔVAT/SAT ratio (ΔVSR)) independent of baseline body composition measures, visit year, income, marital status, physical activity, smoking and alcohol intake. Secondary analyses examined differences in rate of fat change by menopausal status (pre, peri, post). Results Levels of BMI, VAT, and VSR all increased over the 7 year period on average (p<.001); however, the change in BMI (mean ΔBMI = +0.5%) was far smaller than for VAT (mean ΔVAT= +6.8%), SAT (mean ΔSAT = +2.4%), and VSR (mean ΔVSR = +3.6%). ΔBMI, ΔVAT, and ΔSAT decreased linearly with age in both sexes (p<0.01), such that older individuals had lower rates of BMI, VAT, and SAT gain, and this deceleration in BMI, VAT, and SAT accrual was greater in men than women (p for interaction <0.05). ΔVSR did not vary with age in either sex, but remained higher in men than women throughout adulthood. There were no differences in rate of weight or fat gain by menopausal status after adjustment for age. Conclusions Men and women continue to accrue abdominal adiposity with age, but the rate of weight and fat gain decreases over time, particularly in men. PMID:27005404

  17. High-power, high-efficiency FELs

    SciTech Connect

    Sessler, A.M.

    1989-04-01

    High power, high efficiency FELs require tapering, as the particles loose energy, so as to maintain resonance between the electromagnetic wave and the particles. They also require focusing of the particles (usually done with curved pole faces) and focusing of the electromagnetic wave (i.e. optical guiding). In addition, one must avoid transverse beam instabilities (primarily resistive wall) and longitudinal instabilities (i.e sidebands). 18 refs., 7 figs., 3 tabs.

  18. Longitudinal study of fingerprint recognition.

    PubMed

    Yoon, Soweon; Jain, Anil K

    2015-07-14

    Human identification by fingerprints is based on the fundamental premise that ridge patterns from distinct fingers are different (uniqueness) and a fingerprint pattern does not change over time (persistence). Although the uniqueness of fingerprints has been investigated by developing statistical models to estimate the probability of error in comparing two random samples of fingerprints, the persistence of fingerprints has remained a general belief based on only a few case studies. In this study, fingerprint match (similarity) scores are analyzed by multilevel statistical models with covariates such as time interval between two fingerprints in comparison, subject's age, and fingerprint image quality. Longitudinal fingerprint records of 15,597 subjects are sampled from an operational fingerprint database such that each individual has at least five 10-print records over a minimum time span of 5 y. In regard to the persistence of fingerprints, the longitudinal analysis on a single (right index) finger demonstrates that (i) genuine match scores tend to significantly decrease when time interval between two fingerprints in comparison increases, whereas the change in impostor match scores is negligible; and (ii) fingerprint recognition accuracy at operational settings, nevertheless, tends to be stable as the time interval increases up to 12 y, the maximum time span in the dataset. However, the uncertainty of temporal stability of fingerprint recognition accuracy becomes substantially large if either of the two fingerprints being compared is of poor quality. The conclusions drawn from 10-finger fusion analysis coincide with the conclusions from single-finger analysis.

  19. Longitudinal study of fingerprint recognition

    PubMed Central

    Yoon, Soweon; Jain, Anil K.

    2015-01-01

    Human identification by fingerprints is based on the fundamental premise that ridge patterns from distinct fingers are different (uniqueness) and a fingerprint pattern does not change over time (persistence). Although the uniqueness of fingerprints has been investigated by developing statistical models to estimate the probability of error in comparing two random samples of fingerprints, the persistence of fingerprints has remained a general belief based on only a few case studies. In this study, fingerprint match (similarity) scores are analyzed by multilevel statistical models with covariates such as time interval between two fingerprints in comparison, subject’s age, and fingerprint image quality. Longitudinal fingerprint records of 15,597 subjects are sampled from an operational fingerprint database such that each individual has at least five 10-print records over a minimum time span of 5 y. In regard to the persistence of fingerprints, the longitudinal analysis on a single (right index) finger demonstrates that (i) genuine match scores tend to significantly decrease when time interval between two fingerprints in comparison increases, whereas the change in impostor match scores is negligible; and (ii) fingerprint recognition accuracy at operational settings, nevertheless, tends to be stable as the time interval increases up to 12 y, the maximum time span in the dataset. However, the uncertainty of temporal stability of fingerprint recognition accuracy becomes substantially large if either of the two fingerprints being compared is of poor quality. The conclusions drawn from 10-finger fusion analysis coincide with the conclusions from single-finger analysis. PMID:26124106

  20. Users program for storage-ring based FEL and synchrotron sources of the Duke FEL Laboratory

    SciTech Connect

    Straub, K.D.; Barnett, G.; Burnham, B.

    1995-12-31

    The storage ring at the Duke FEL Laboratory was first operated with a stored e-beam in November, 1994. It has now achieved operation energies in excess 1 GeV with more than 100 mA current at 280 MeV. The ring has several ports for FEL and synchrotron light source research. The circulating ring current can be synchronized with the seperate Mark III FEL operating in the 2-9.5 {mu}m IR region. This allows low optical jitter (10-20 ps) between the two sources and thus pump-probe operation. The ring has been configured to drive a number of light sources including the OK-4 FEL system capable of FEL operation between 400 and 65 nm, an inverse Compton scattering source using this undulator which will yield 4-200 MeV gammas, an undulator source at approximately 40 {angstrom} (not an FEL), a mm FEL with inverse compton scattering providing 1-100 keV x-rays and two synchrotron ports from the bend magnets for which the {lambda}{sub c} = 11-12 {angstrom} for 1 GeV. The broadly tunable FEL sources and their associated inverse compton scattering are extremely bright. The initial research proposals, submitted to the Laboratory emphasizes photoelectron spectroscopy, PEEM, high resolution vacuum UV of gases, solid spectroscopy and photochemistry in the UV, X-ray microprobe studies, X-ray microscopy, X-ray holography, X-ray crystallography, Mossbauer spectroscopy, nuclear spectroscopy, neutron production, photon activation therapy and broadband synchrotron as a probe of fast reaction in the IR and near IR.

  1. Colorado Longitudinal Twin Study of Reading Disability

    ERIC Educational Resources Information Center

    Wadsworth, Sally J.; DeFries, John C.; Olson, Richard K.; Willcutt, Erik G.

    2007-01-01

    The primary objectives of the present study are to introduce the Colorado Longitudinal Twin Study of Reading Disability, the first longitudinal twin study in which subjects have been specifically selected for having a history of reading difficulties, and to present some initial assessments of the stability of reading performance and cognitive…

  2. Colorado Longitudinal Twin Study of Reading Disability

    ERIC Educational Resources Information Center

    Wadsworth, Sally J.; DeFries, John C.; Olson, Richard K.; Willcutt, Erik G.

    2007-01-01

    The primary objectives of the present study are to introduce the Colorado Longitudinal Twin Study of Reading Disability, the first longitudinal twin study in which subjects have been specifically selected for having a history of reading difficulties, and to present some initial assessments of the stability of reading performance and cognitive…

  3. Fears in Czech Adolescents: A Longitudinal Study

    ERIC Educational Resources Information Center

    Michalcáková, Radka; Lacinová, Lenka; Kyjonková, Hana; Bouša, Ondrej; Jelínek, Martin

    2013-01-01

    The present study investigates developmental patterns of fear in adolescence. It is based on longitudinal data collected as a part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) project. A total of 186 Czech adolescents (43% girls) were assessed repeatedly at the age of 11, 13, and 15 years. The free-response method was…

  4. Fears in Czech Adolescents: A Longitudinal Study

    ERIC Educational Resources Information Center

    Michalcáková, Radka; Lacinová, Lenka; Kyjonková, Hana; Bouša, Ondrej; Jelínek, Martin

    2013-01-01

    The present study investigates developmental patterns of fear in adolescence. It is based on longitudinal data collected as a part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) project. A total of 186 Czech adolescents (43% girls) were assessed repeatedly at the age of 11, 13, and 15 years. The free-response method was…

  5. A longitudinal study of confabulation.

    PubMed

    Dalla Barba, Gianfranco; Brazzarola, Marta; Marangoni, Sara; Barbera, Claudia; Zannoni, Ilaria

    2017-02-01

    Confabulation, the production of statements and actions that are unintentionally incongruous to the subject's history, background, present and future situation, is a rather infrequent disorder, observed in several conditions affecting the nervous system. Little is known about the quantitative and qualitative evolution of confabulation in time. In this study we evaluated longitudinally the evolution of this disorder in a group of severe confabulators, using the Confabulation Battery (CB), a sensitive tool to detect confabulations in various memory domains. It was found that confabulations were stable over time and not temporally limited. It was also found that "Habits Confabulations" (HCs), i.e., habits and repeated personal events mistaken as specific, unique past and future personal episodes, or well-known public events when semantic knowledge is concerned, was the more frequently observed type of confabulation. Confabulations were also more prominent in the domain of Temporal Consciousness (TC), i.e., a specific form of consciousness that allows individuals to remember their personal past, to be oriented in their present world and to predict their personal future, than in Knowing Consciousness (KC), i.e., a specific form of consciousness allowing individuals to be aware of past, present and future impersonal knowledge and information. Confabulations showed also persistence, i.e., confabulations at the same questions over time, and consistency, i.e., same type of confabulation at the same question over time. These findings are discussed within the framework of the Memory, Consciousness and Temporality Theory.

  6. Longitudinal Studies of Spelling Development.

    ERIC Educational Resources Information Center

    Ellis, Nick

    Noting that proposed models of literacy development suggest that reading and writing mutually influence and grow from each other, this paper summarizes aspects of stage theories of literacy development and an integrative model, and considers how the model fared in empirical longitudinal tests. The paper begins with a summary of the modal aspects…

  7. Longitudinal study of keratoconus progression.

    PubMed

    Li, Xiaohui; Yang, Huiying; Rabinowitz, Yaron S

    2007-10-01

    To determine if differences in topographic progression between unaffected keratoconus relatives and normal controls can predict factors associated with the development of keratoconus in a longitudinal study. We recruited 369 unaffected keratoconus relatives and 119 normal controls in Los Angeles. Both eyes of subjects were examined at baseline clinically and by quantitative videokeratography and at a period ranging from 1 year to 8 years. Progression to keratoconus was evaluated by quantitative videokeratography variables. Unaffected relatives had higher Central K (CK), I-S and KISA values and were younger than normal controls (CK: 44.70 vs 44.01, P<0.01; I-S: 0.76 vs 0.58, P<0.01, KISA: 29.97 vs 23.89, P=0.02; age: 34.8 vs 41.0, P<0.01) at baseline. All three indices significantly increased with age, and CK and KISA values were associated with a positive family history for keratoconus (P<0.001 for CK and P=0.05 for KISA), however, the two groups were not statistically different in progression of keratoconus. After grouping unaffected relatives as high risk (age< or = 30 or Central K > or = 47.2 and I-S> or =1.2 or KISA> or = 60) and low risk (age>30 and Central K<47.2 and I-S<1.2 and KISA< 60), relatives in the high risk group had a greater increase in CK and I-S values than those in the low risk group (CK: P=0.009; I-S: P<0.001), which indicated that there were significantly different rates of progression between two groups. Unaffected relatives had higher videokeratography indices than normal controls, but overall they did not progress to keratoconus quicker than normal controls. However, relatives in the high risk group may have a greater risk of progression to keratoconus.

  8. Longitudinal study of keratoconus progression

    PubMed Central

    Li, Xiaohui; Yang, Huiying; Rabinowitz, Yaron S.

    2013-01-01

    To determine if differences in topographic progression between unaffected keratoconus relatives and normal controls can predict factors associated with the development of keratoconus in a longitudinal study. We recruited 369 unaffected keratoconus relatives and 119 normal controls in Los Angeles. Both eyes of subjects were examined at baseline clinically and by quantitative videokeratography and at a period ranging from 1 year to 8 years. Progression to keratoconus was evaluated by quantitative videokeratography variables. Unaffected relatives had higher Central K (CK), I-S and KISA values and were younger than normal controls (CK: 44.70 vs 44.01, P<0.01; I-S: 0.76 vs 0.58, P<0.01, KISA: 29.97 vs 23.89, P=0.02; age: 34.8 vs 41.0, P<0.01) at baseline. All three indices significantly increased with age, and CK and KISA values were associated with a positive family history for keratoconus (P<0.001 for CK and P=0.05 for KISA), however, the two groups were not statistically different in progression of keratoconus. After grouped unaffected relatives as the high risk (age<=30 or Central K>=47.2 or I-S >=1.2 or KISA>=60) and the low risk (age>30 and Central K<47.2 and I-S <1.2 and KISA<60), relatives in the high risk group had a greater increase in CK and I-S values than those in the low risk group (CK: p=0.009; I-S: p<0.001), which indicated that there were significantly different rates of progression between two groups. Unaffected relatives had higher videokeratography indices than normal controls, but overall they did not progress to keratoconus quicker than normal controls. However, relatives in a high risk group may have a greater risk of progression to keratoconus. PMID:17681291

  9. FEL-accelerator related diagnostics

    SciTech Connect

    Kevin Jordan; David Douglas; Stephen V. Benson; Pavel Evtuschenko

    2007-08-02

    Free Electron Lasers (FEL) present a unique set of beam parameters to the diagnostics suite. The FEL requires characterization of the full six dimensional phase space of the electron beam at the wiggler and accurate alignment of the electron beam to the optical mode of the laser. In addition to the FEL requirements on the diagnostics suite, the Jefferson Lab FEL is operated as an Energy Recovered Linac (ERL) which imposes additional requirements on the diagnostics. The ERL aspect of the Jefferson Lab FEL requires that diagnostics operate over a unique dynamic range and operate with simultaneous transport of the accelerated and energy recovered beams. This talk will present how these challenges are addressed at the Jefferson Lab FEL.

  10. Tapered undulators for SASE FELs

    NASA Astrophysics Data System (ADS)

    Fawley, William M.; Huang, Zhirong; Kim, Kwang-Je; Vinokurov, Nikolai A.

    2002-05-01

    We discuss the use of tapered undulators to enhance the performance of free-electron lasers (FELs) based upon self-amplified spontaneous emission, where the radiation tends to have a relatively broad bandwidth and limited temporal coherence. Using the polychromatic FEL simulation code GINGER, we numerically demonstrate the effectiveness of tapered undulators for parameters corresponding to the Argonne low-energy undulator test line FEL and the proposed linac coherent light source.

  11. Power beaming with FEL lasers

    NASA Astrophysics Data System (ADS)

    Lampel, Michael C.; Curtin, Mark S.; Burke, Robert J.; Cover, Ralph A.; Rakowsky, George; Bennett, Glenn T.

    1993-06-01

    FEL power beaming has broad application to space operations. The Rocketdyne Division of Rockwell International Corporation has examined the commercial applications of beamed power from Earth to space using the Radio Frequency LINAC Free Electron Laser (RF FEL) and has determined that there is a substantial addressable market. Rocketdyne's experience in developing and demonstrating FEL technologies, optics and atmospheric compensation and advanced power and power distribution systems ideally positions the Division to conduct the initial demonstration to prove the feasibility of using a FEL to beam power to space platforms.

  12. Saturation and pulsed FEL dynamics

    SciTech Connect

    Giannessi, L.; Mezi, L.

    1995-12-31

    The behavior of a FEL operating in the saturated pulsed regime, may be reproduced by the linear FEL integral equation, suitably modified to include saturation effects through a gain depression coefficient depending on the laser intensity. This simple method allows to evaluate several FEL parameters like gain, efficiency, band-width and optical pulse duration as functions of the optical cavity length, only with a numerical integration. The predictions have been compared with available experimental and numerical data, and the method has been applied to estimate the operating characteristics of some planned FEL experiments.

  13. A proposed visible FEL Facility at Boeing

    SciTech Connect

    Dowell, D.H.; Adamski, J.L.; Hayward, T.D.

    1995-12-31

    A 1-kW average power, visible wavelength FEL is described, based on a 120-MeV, 0.1. A macropulse average current linac operating at a duty factor of 0. 6% and having average beam power of 70 kW. The accelerator will employ a demonstrated photoinjector, 18-MeV, 433-MHz linac as an injector, followed by a 1300-MHz longitudinal phase space {open_quotes} linearizer,{close_quotes} a magnetic buncher chicane, and seven 1300-MHz, pulsed traveling wave linac sections. The magnets used to transport the beam from the linac to the FEL centerline, the 5-m THUNDER wiggler, and the optical resonator will be reclaimed from previous FEL demonstration experiments. We expect to attain pulse lengths of 7 ps for 3.5 nC, with minimal distortion of the pulse profile and normalized rms emittance of 7.5 {+-} 2.5 {pi} mm-mr. FELEX projects a laser conversion efficiency of 4.3 %, yielding average output of 3 kW.

  14. Feedback Requirements for SASE-FELs

    SciTech Connect

    Loos, Henrik; /SLAC

    2012-07-06

    The operation of a Self Amplified Spontaneous Emission (SASE) Free Electron Lasers (FEL) at soft and hard X-ray wavelengths driven by a high brightness electron beam imposes strong requirements on the stability of the accelerator and feedback systems are necessary to both guarantee saturation of the SASE process as well as a stable photon beam for user experiments. Diagnostics for the relevant transverse and longitudinal beam parameters are presented and various examples of feedback systems for bunches with low repetition rate as well as systems for intra bunch train feedbacks are discussed.

  15. Diagnostic technique applied for FEL electron bunches

    NASA Astrophysics Data System (ADS)

    Brovko, O.; Grebentsov, A.; Morozov, N.; Syresin, E.; Yurkov, M.

    2016-05-01

    Diagnostic technique applied for FEL ultrashort electron bunches is developed at JINR-DESY collaboration within the framework of the FLASH and XFEL projects. Photon diagnostics are based on calorimetric measurements and detection of undulator radiation. The infrared undulator constructed at JINR and installed at FLASH is used for longitudinal bunch shape measurements and for two-color lasing provided by the FIR and VUV undulators. The pump probe experiments with VUV and FIR undulators provide the bunch profile measurements with resolution of several femtosecond. The new three microchannel plates (MCP) detectors operated in X-ray range are under development now in JINR for SASE1-SASE 3 European XFEL.

  16. Femtosecond laser-generated high-energy-density states studied by x-ray FELs

    NASA Astrophysics Data System (ADS)

    Nakatsutsumi, M.; Appel, K.; Baehtz, C.; Chen, B.; Cowan, T. E.; Göde, S.; Konopkova, Z.; Pelka, A.; Priebe, G.; Schmidt, A.; Sukharnikov, K.; Thorpe, I.; Tschentscher, Th; Zastrau, U.

    2017-01-01

    The combination of powerful optical lasers and an x-ray free-electron laser (XFEL) provides unique capabilities to study the transient behaviour of matter in extreme conditions. The high energy density science instrument (HED instrument) at the European XFEL will provide the experimental platform on which an unique x-ray source can be combined with various types of high-power optical lasers. In this paper, we highlight selected scientific examples together with the associated x-ray techniques, with particular emphasis on femtosecond (fs)-timescale pump-probe experiments. Subsequently, we present the current design status of the HED instrument, outlining how the experiments could be performed. First user experiments will start at the beginning of 2018, after which various optical lasers will be commissioned and made available to the international scientific community.

  17. Effects of Beamtube Roughness on X-Ray FEL Performance

    SciTech Connect

    Stupakov, Gennady

    1999-04-05

    In an X-Ray FEL like the Linear Coherent Light Source (LCLS) being designed at SLAC, electron bunches about 70 {micro}m FWHM long are sent into a beam tube only 5 mm in internal diameter and more than 100 m in length. Due to the surface roughness of the beam tube, wakefields can be generated that catch up to the bunch and interact with it, causing energy spread and emittance growth. The strength of this effect depends on the details of the roughness of the surface. We present here a study in which the roughness of the beam tube was measured, and the longitudinal impedance of the tube was calculated. Our result shows that commercially available beam tube can be made smooth enough so the resulting wakefield effects are within the tolerance determined by the requirement that the induced relative energy spread of the beam be less then 5 x 10{sup {minus}4}.

  18. Short wavelength FELS

    SciTech Connect

    Sheffield, R.L.

    1991-01-01

    The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. The recent progress in the development of brighter electron beams enables the use of much lower energy electron rf linacs to reach short-wavelengths than previously considered possible. This paper will summarize the present results obtained with synchrotron sources, review proposed short- wavelength FEL designs and then present a new design which is capable of over an order of magnitude higher power to the extreme ultraviolet. 17 refs., 10 figs.

  19. Simulation studies of a XUV/soft X-ray harmonic-cascade FEL for the proposed LBNL recirculating linac*

    SciTech Connect

    Fawley, W.M.; Barletta, W.A.; Corlett, J.N.; Zholents, A.

    2003-06-02

    Presently there is significant interest at LBNL in designing and building a facility for ultrafast (i.e. femtosecond time scale) x-ray science based upon a superconducting, recirculating RF linac (see Corlett et al. for more details). In addition to producing synchrotron radiation pulses in the 1-15 keV energy range, we are also considering adding one or more free-electron laser (FEL) beamlines using a harmonic cascade approach to produce coherent XUV soft X-ray emission beginning with a strong input seed at {approx}200 nm wavelength obtained from a ''conventional'' laser. Each cascade is composed of a radiator together with a modulator section, separated by a magnetic chicane. The chicane temporally delays the electron beam pulse in order that a ''virgin'' pulse region (with undegraded energy spread) be brought into synchronism with the radiation pulse, which together then undergo FEL action in the modulator. We present various results obtained with the GINGER simulation code examining final output sensitivity to initial electron beam parameters. We also discuss the effects of spontaneous emission and shot noise upon this particular cascade approach which can limit the final output coherence.

  20. Electron Beam Diagnostics Of The JLAB UV FEL

    SciTech Connect

    Evtushenko, Pavel; Benson, Stephen; Biallas, George; Coleman, James; Dickover, Cody; Douglas, David; Marchlik, Matthew; Sexton, Daniel; Tennant, Christopher

    2011-03-01

    In this contribution we describe various systems and aspects of the electron beam diagnostics of the JLab UV FEL. The FEL is installed on a new bypass beam line at the existing 10 kW IR Upgrade FEL. Here, we describe a set of the following systems. A combination of OTR and phosphor viewers is used for measurements of the transverse beam profile, transverse emittance, and Twiss parameters. This system is also used for alignment of the optical cavity of the UV oscillator and to ensure the overlap between the electron beam and optical mode in the FEL wiggler. A system of beam position monitors equipped with log-amp based BPM electronics. Bunch length on the order of 120 fs RMS is measured with the help of a modified Martin-Puplett interferometer. The longitudinal transfer function measurement system is used to set up bunch compression in an optimal way, such that the LINAC RF curvature is compensated using only higher order magnetic elements of the beam transport. This set of diagnostic systems made a significant contribution in achieving first lasing of the FEL after only about 60 hours of beam operation.

  1. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

  2. Coherent Synchrotron Radiation as a Diagnostic Tool for the LCLS Longitudinal Feedback System

    SciTech Connect

    Wu, Juhao; Emma, P.; Huang, Z.; /SLAC

    2005-06-15

    The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL). To ensure the vitality of FEL lasing, a longitudinal feedback system is required together with other diagnostics. In this paper, we study the possibility of using Coherent Synchrotron Radiation (CSR) from the chicane as a diagnostic tool for bunch length feedback. Studies show that CSR is a good candidate, even for a non-Gaussian, double-horn longitudinal charge distribution as in the LCLS. We further check the possibility for detecting possible microbunching.

  3. Longitudinal Studies--Are They Worth It?

    ERIC Educational Resources Information Center

    Cowley, Judith

    A longitudinal study of otitis media in young children, begun in 1981, aimed to provide information on the incidence and prevalence of otitis media in young children in the Newcastle (England) region and to follow their academic progress. Subjects selected for the study were kindergartners in five schools and represented an ethnically homogeneous…

  4. Are Sibling Relationships Protective? A Longitudinal Study

    ERIC Educational Resources Information Center

    Gass, Krista; Jenkins, Jennifer; Dunn, Judy

    2007-01-01

    Background: Although the protective effects of familial and parental support have been studied extensively in the child psychopathology literature, few studies have explored the protective quality of positive sibling relationships. Methods: A two-wave longitudinal design was used to examine the protective effect of positive sibling relationships…

  5. FEL on slow cyclotron wave

    SciTech Connect

    Silivra, A.

    1995-12-31

    A physical mechanism of interaction of fast electromagnetic wave with slow cyclotron wave of relativistic electron beam in a FEL with helical wiggler field is described. It is shown that: (1) interaction is possible for both group of steady state electron trajectories (2) positive gain is achieved within certain interval of guide field strength (3) operation wavelength for group 1 trajectories ({Omega}{sub 0}/{gamma} < k{omega}{upsilon}{parallel}) is shorter than for the conventional FEL synchronism. A nonlinear analysis shows that efficiency of slow cyclotron FEL is restricted mainly by a breakdown of a single electron synchronism due to dependence of (modified) electron cyclotron frequency on an energy of electron. Nevertheless, as numerical simulation shows, typical efficiency of 15 % order is achieved in millimeter wavelength band for the midrelativistic ({gamma}= 3 {divided_by} 4) slow cyclotron wave FEL. Tapering of magnetic field results in a substantial increase of efficiency.

  6. Analysis of FEL-based CeC amplification at high gain limit

    SciTech Connect

    Wang, G.; Litvinenko, V.; Jing, Y.

    2015-05-03

    An analysis of Coherent electron Cooling (CeC) amplifier based on 1D Free Electron Laser (FEL) theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.

  7. Review of High Gain FELs

    SciTech Connect

    Shintake, Tsumoru

    2007-01-19

    For understanding on basic radiation mechanism of the high-gain FEL based on SASE, the author presents electron-crystal interpretation of FEL radiation. In the electron-crystal, electrons are localized at regularly spaced multi-layers, which represents micro-bunching, whose spacing is equal to the radiation wavelength, and the multi-layers are perpendicular to beam axis, thus, diffracted wave creates Bragg's spots in forward and backward directions. Due to the Doppler's effect, frequency of the back-scattered wave is up-converted, generates forwardly focused X-ray. The Bragg's effect contributes focusing the X-ray beam into a spot, thus peak power becomes extremely higher by factor of typically 107. This is the FEL radiation. As well known, the total numbers of scattered photons in Bragg's spots is equal to the total elastic scattering photons from the atoms contained in the crystal. Therefore, total power in the FEL laser is same as the spontaneous radiation power from the undulator for the same beam parameter. The FEL radiation phenomenon is simple interference effect. In today's presentations, we use the laser pointer, and we frequently experience difficulty in pointing precisely or steadily in one place on the screen, since the laser spot is very small and does not spread. Exactly same to this, X-ray FEL is a highly focused beam, and pointing stability dominates productivity of experiment, thus we need special care on beam stability from linear accelerator.

  8. Biomechanics of Distance Running: A Longitudinal Study

    ERIC Educational Resources Information Center

    Nelson, Richard C.; Gregor, Robert J.

    1976-01-01

    Training for distance running over a long period produces meaningful changes in the running mechanics of experienced runners, as revealed in this longitudinal study of the biomechanical components of stride length, stride rate, stride time, and support and nonsupport time. (MB)

  9. Collaborative Knowledge-Building: A Longitudinal Study

    ERIC Educational Resources Information Center

    Li, Qing

    2009-01-01

    The focus of this paper is on knowledge-building in a technology-supported learning environment in higher education through a longitudinal study of a graduate course from 2003 to 2007. The primary question is: how do learning conditions designed into a graduate course contribute to collaborative knowledge building? In particular, two major…

  10. Biomechanics of Distance Running: A Longitudinal Study

    ERIC Educational Resources Information Center

    Nelson, Richard C.; Gregor, Robert J.

    1976-01-01

    Training for distance running over a long period produces meaningful changes in the running mechanics of experienced runners, as revealed in this longitudinal study of the biomechanical components of stride length, stride rate, stride time, and support and nonsupport time. (MB)

  11. MPCP Longitudinal Educational Growth Study Baseline Report

    ERIC Educational Resources Information Center

    Witte, John F.; Wolf, Patrick J.; Cowen, Joshua M.; Fleming, David J.; Lucas-McLean, Juanita

    2008-01-01

    This report focuses on the initial design, implementation and baseline results of the five-year Longitudinal Educational Growth Study (LEGS) of the Milwaukee Parental Choice Program (MPCP) being conducted by the School Choice Demonstration Project (SCDP). The LEGS will be the first evaluation of the participant effects of the MPCP using…

  12. Optimization of single-step tapering amplitude and energy detuning for high-gain FELs

    NASA Astrophysics Data System (ADS)

    Li, He-Ting; Jia, Qi-Ka

    2015-01-01

    We put forward a method to optimize the single-step tapering amplitude of undulator strength and initial energy tuning of electron beam to maximize the saturation power of high gain free-electron lasers (FELs), based on the physics of longitudinal electron beam phase space. Using the FEL simulation code GENESIS, we numerically demonstrate the accuracy of the estimations for parameters corresponding to the linac coherent light source and the Tesla test facility.

  13. Photon Source Capabilities of the Jefferson Lab FEL

    SciTech Connect

    Benson, S. V.; Douglas, D. R.; Evtushenko, P.; Hannon, F. E.; Hernandez-Garcia, C.; Klopf, J. M.; Legg, R. A.; Neil, G. R.; Shinn, M. D.; Tennant, C. D.; Zhang, S.; Williams, G. P.

    2013-03-22

    Jefferson Lab operates a superconducting energy recovered linac which is operated with CW RF and which powers oscillator-based IR and UV Free Electron Lasers (FELs) with diffraction limited sub-picosecond pulses with >10{sup 13} photons per pulse (1.0%BW) at pulse repetition frequencies up to 75 MHz. Useful harmonics extend into the vacuum ultraviolet (VUV). Based on FEL model calculations validated using this facility, we have designed both an oscillator-based VUV-FEL that would produce 6 10{sup12} coherent (0.5% BW) 100 eV photons per pulse at multi-MHz repetition rates in the fundamental, and a dual FEL configuration that would allow simultaneous lasing lasing at THz and UV wavelengths. The VUV-FEL would utilize a novel high gain, low Q cavity, while the THz source would be an FEL oscillator with a short wiggler providing diffraction limited pulses with pulse energy exceeding 50 microJoules. The THz source would use the exhaust beam from a UVFEL. Such multiphoton capabilities would provide unique opportunities for out of equilibrium dynamical studies at time-scales down to 50 fs. The fully coherent nature of all these sources results in peak and average brightness values that are many orders of magnitude higher than storage rings. We acknowledge support from the Commonwealth of Virginia. Jefferson Lab is supported by the U.S. DOE under Contract No. DE-AC05-84-ER40150.

  14. Possible enhancement of SASE FEL output field intensity induced by local phase jump

    NASA Astrophysics Data System (ADS)

    Varfolomeev, A. A.; Yarovoi, T. V.; Bousine, P. V.

    1998-02-01

    A possible influence on the FEL dynamics of a locally induced phase jump between the FEL radiation and electron beam is considered. A numerical study has been made for the SASE mode FEL supposing that the phase jumps are introduced at different depths inside the undulator. The FEL evolution starting from a small input signal was studied in 1D high gain approach. It was shown that the FEL radiation output is sensitive to the phase jump value if it is introduced at the depth where saturation of output power takes places. In the steady state regime, the phase displacement of order ˜π provides enhancement of the peak output power up to 50%. Some kind of optical tapering is also possible giving further FEL efficiency enhancement.

  15. Staged energy cascades for the LUX FEL

    SciTech Connect

    Penn, G.

    2004-07-27

    Designs and simulation studies for harmonic cascades, consisting of multiple stages of harmonic generation in free electron lasers (FELs), are presented as part of the LUX R&D project to design ultrafast, high photon energy light sources for basic science. Beam energies of 1.1, 2.1, and 3.1 GeV, corresponding to each pass through a recirculating linac, have independent designs for the harmonic cascade. Simulations were performed using the GENESIS FEL code, to obtain predictions for the performance of these cascades over a wide range of photon energies in terms of the peak power and laser profile. The output laser beam consists of photon energies of up to 1 keV, with durations of the order of 200 fs or shorter. The contribution of shot noise to the laser output is minimal, however fluctuations in the laser and electron beam properties can lead to variations in the FEL output. The sensitivity of the cascade to electron beam properties and misalignments is studied, taking advantage of the fact that GENESIS is a fully 3-dimensional code.

  16. What Can We Learn From Longitudinal Studies of Adult Development?

    PubMed Central

    Schaie, K. Warner

    2005-01-01

    This article distinguishes between normal and pathological aging, provides an interdisciplinary context, and then considers a sample case of cognitive aging. Developmental influences on cognition include the physiological infrastructure, genetic predispositions, and environmental influences. Different types of longitudinal studies are distinguished, and contrasting findings of cross-sectional and longitudinal are examined in the sample case of the Seattle Longitudinal Study. Also considered is the longitudinal context for intervention studies and the role of longitudinal family studies in assessing rate of aging and generational differences in rates of aging. Finally, attention is given to the role of longitudinal studies in the early detection of risk for dementia in advanced age. PMID:16467912

  17. Nonlinear harmonic generation in the STARS FEL

    NASA Astrophysics Data System (ADS)

    Abo-Bakr, M.; Goldammer, K.; Kamps, T.; Knobloch, J.; Kuske, B.; Leitner, T.; Meseck, A.

    2008-08-01

    BESSY proposes to build STARS, an FEL to demonstrate cascaded High Gain Harmonic Generation (HGHG). In two HGHG stages, a laser source of 700-900 nm is converted down to a wavelength of 40-70 nm. The STARS facility consists of a normal-conducting RF photoinjector, three superconducting TESLA-type acceleration modules, a magnetic bunch compressor and two stages of HGHG, each consisting of a modulator, dispersive chicane and a radiator. At the entrance of the undulator section, the beam energy is 325 MeV and the peak current is about 500 A. With these parameters, the STARS FEL reaches saturation with a peak power of 100-350 MW. A superradiant mode is also foreseen which boosts the radiation power to the GW-level. Due to nonlinear harmonic generation (NHG), free electron lasers also radiate coherently at higher harmonics of the FEL resonant frequency. STARS can hence extend its output range to even shorter wavelengths. This paper presents studies of the STARS harmonic content in the wavelength range of 6-20 nm. Seeding with high harmonic generation pulses at 32 nm is also discussed.

  18. Harmonic cascade FEL designs for LUX

    SciTech Connect

    Penn, G.; Reinsch, M.; Wurtele, J.; Corlett, J.N.; Fawley, W.M.; Zholents, A.; Wan, W.

    2004-07-16

    LUX is a design concept for an ultrafast X-ray science facility, based on an electron beam accelerated to GeV energies in are circulating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 200-250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1 keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.

  19. Future metrology needs for FEL reflective optics.

    SciTech Connect

    Assoufid, L.

    2000-09-21

    An International Workshop on Metrology for X-ray and Neutron Optics has been held March 16-17, 2000, at the Advanced Photon Source, Argonne National Laboratory, near Chicago, Illinois (USA). The workshop gathered engineers and scientists from both the U.S. and around the world to evaluate metrology instrumentation and methods used to characterize surface figure and finish for long grazing incidence optics used in beamlines at synchrotrons radiation sources. This two-day workshop was motivated by the rapid evolution in the performance of x-ray and neutron sources along with requirements in optics figure and finish. More specifically, the performance of future light sources, such as free-electron laser (FEL)-based x-ray sources, is being pushed to new limits in term of both brilliance and coherence. As a consequence, tolerances on surface figure and finish of the next generation of optics are expected to become tighter. The timing of the workshop provided an excellent opportunity to study the problem, evaluate the state of the art in metrology instrumentation, and stimulate innovation on future metrology instruments and techniques to be used to characterize these optics. This paper focuses on FEL optics and metrology needs. (A more comprehensive summary of the workshop can be found elsewhere.) The performance and limitations of current metrology instrumentation will be discussed and recommendations from the workshop on future metrology development to meet the FEL challenges will be detailed.

  20. Predictors of Transfer Adjustment: A Longitudinal Study.

    DTIC Science & Technology

    1985-01-01

    Department of Psychology . : PREDICTORS OF TRANSFER AIIJUSTNEN: . A LONGITUDIN4AL STUDY"- Jaues B. Shaw Cynthia D. Fisher and Richard W. Woodman...1985 Acssa o NTIS GRA&I TR-ONR-7 DTIC TAB Unannounced E Just ification Distribution/ Department of Psychology Availability Codes Department of...PROJECT. TASKAREA & WORK UNIT NUMIBERS Departments of Management and Psychology 62763 N Texas.A&M University RF 63521 College Station, TX 77843 RF

  1. [Methodological problems of longitudinal studies on schizophrenia].

    PubMed

    Häfner, H; an der Heiden, W

    2000-05-01

    Longitudinal studies are a key to understanding schizophrenia. They are the more informative, the longer the periods covered. Hence, good studies into the course of schizophrenia almost exclusively involve a lot of effort and cost. In practice, however, time-consuming methods and design variables must be avoided. The pitfalls this constraint produces are instructive of the difficulties longitudinal studies are faced with in striving for valid results. For reasons of research economy, requirements must be adjusted to study objectives. Studies into the short term course are less time-consuming, but because of the rapid changes in the illness course study intervals should be defined clearly and observed strictly. In long-term studies, too, one source of error lies in the highly varying lengths of illness of the patients studied. Even some of the classic long-term studies are marred by this error. The beginning of the follow-up period should be comparable across the study cohort and as close to illness onset as possible. To obtain generally valid results the probands must be representative of all the illness cases in the general population not only at the outset, but also all the later stages of the study. Besides the efforts to avoid attrition in the study cohort, ways must be found for correcting and estimating data for an acceptable proportion of drop-outs. In the analysis of course and outcome the indicators chosen must be apt to the traditional subtypes as well as to a theoretical symptom patterns and empirical symptom structures. In the context of typical design variables of longitudinal studies the assets and weaknesses of two retrospective and one prospective design will be discussed. Concerning the social course, importance of disease-independent factors, such as age, sex and level of social development at illness onset, as well as of control groups will be demonstrated. Predictor models will be discussed with reference to the direct and indirect influences

  2. HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS.

    SciTech Connect

    BEN-ZVI, ILAN, DAYRAN, D.; LITVINENKO, V.

    2005-08-21

    Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department.

  3. Material deprivation and health: a longitudinal study.

    PubMed

    Tøge, Anne Grete; Bell, Ruth

    2016-08-08

    Does material deprivation affect the consequences of ill health? Answering this question requires that we move beyond the effects of income. Longitudinal data on material deprivation, longstanding illness and limiting longstanding illness enables investigations of the effects of material deprivation on risk of limiting longstanding illness. This study investigates whether a shift from affording to not affording a car predicts the probability of limiting longstanding ill (LLSI). The 2008-2011 longitudinal panel of Statistics on Income, Social Inclusion and Living Conditions (EU-SILC) is utilised. Longitudinal fixed effects logit models are applied, using LLSI as dependent variable. Transition from affording a car to not affording a car is used as a proxy for material deprivation. All models are controlled for whether the person becomes longstanding ill (LSI) as well as other time-variant covariates that could affect the results. The analysis shows a statistically significant increased odds ratio of LLSI when individuals no longer can afford a car, after controlling for confounders and LSI in the previous year (1.129, CI = 1.022-1.248). However, when restricting the sample to observations where respondents report longstanding illness the results are no longer significant (1.032, CI = 0.910-1.171). The results indicate an individual level effect of material deprivation on LLSI, suggesting that material resources can affect the consequences of ill health.

  4. Measuring FEL Radiation Properties at VISA-FEL

    SciTech Connect

    Cornacchia, Massimo

    2002-08-21

    The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements.

  5. Using the Longitudinal Study as a Central Teaching Focus.

    ERIC Educational Resources Information Center

    Demchik, Michael J.

    1999-01-01

    Argues that treatment of one investigative longitudinal topic from start to finish in a high school biology class can illustrate many major ideas and concepts. Discusses ways to use various longitudinal studies of plant growth with General Biology classes. (WRM)

  6. A longitudinal study of urea cycle disorders.

    PubMed

    Batshaw, Mark L; Tuchman, Mendel; Summar, Marshall; Seminara, Jennifer

    2014-01-01

    The Urea Cycle Disorders Consortium (UCDC) is a member of the NIH funded Rare Diseases Clinical Research Network and is performing a longitudinal study of 8 urea cycle disorders (UCDs) with initial enrollment beginning in 2006. The consortium consists of 14 sites in the U.S., Canada and Europe. This report summarizes data mining studies of 614 patients with UCDs enrolled in the UCDC's longitudinal study protocol. The most common disorder is ornithine transcarbamylase deficiency, accounting for more than half of the participants. We calculated the overall prevalence of urea cycle disorders to be 1/35,000, with 2/3rds presenting initial symptoms after the newborn period. We found the mortality rate to be 24% in neonatal onset cases and 11% in late onset cases. The most common precipitant of clinical hyperammonemic episodes in the post-neonatal period was intercurrent infections. Elevations in both blood ammonia and glutamine appeared to be biomarkers for neurocognitive outcome. In terms of chronic treatment, low protein diet appeared to result in normal weight but decreased linear growth while N-scavenger therapy with phenylbutyrate resulted in low levels of branched chain amino acids. Finally, we found an unexpectedly high risk for hepatic dysfunction in patients with ornithine transcarbamylase deficiency. This natural history study illustrates how a collaborative study of a rare genetic disorder can result in an improved understanding of morbidity and disease outcome.

  7. A longitudinal study of urea cycle disorders

    PubMed Central

    Batshaw, Mark L.; Tuchman, Mendel; Summar, Marshall; Seminara, Jennifer

    2014-01-01

    The urea cycle disorders consortium (UCDC) is a member of the NIH funded Rare Diseases Clinical Research Network and is performing a longitudinal study of 8 urea cycle disorders (UCD) with initial enrollment beginning in 2006. The consortium consists of 14 sites in the U.S., Canada and Europe. This report summarizes data mining studies of 614 patients with UCD enrolled in the UCDC’s longitudinal study protocol. The most common disorder is ornithine transcarbamylase deficiency, accounting for more than half of the participants. We calculated the overall prevalence of urea cycle disorders to be 1/35,000, with 2/3rds presenting initial symptoms after the newborn period. We found the mortality rate to be 24% in neonatal onset cases and 11% in late onset cases. The most common precipitant of clinical hyperammonemic episodes in the post-neonatal period was intercurrent infections. Elevations in both blood ammonia and glutamine appeared to be biomarkers for neurocognitive outcome. In terms of chronic treatment, low protein diet appeared to result in normal weight but decreased linear growth while N-scavenger therapy with phenybutyrate resulted in low levels of branched chain amino acids. Finally, we found an unexpectedly high risk for hepatic dysfunction in patients with ornithine transcarbamylase deficiency. This natural history study illustrates how a collaborative study of a rare genetic disorder can result in an improved understanding of morbidity and disease outcome. PMID:25135652

  8. Operation of FERMI FELs for users

    NASA Astrophysics Data System (ADS)

    Svandrlik, M.

    2015-05-01

    The FERMI seeded free electron laser facility, located at the Elettra laboratory in Trieste (Italy), has been operated for user experiments in the past years using the first FEL line, FEL-1, covering the VUV - EVU spectral range (100 - 20 nm). After the conclusion of the commissioning for the soft-X ray FEL line, FEL-2, the facility is now ready to provide the scientific community with intense FEL pulses (<10 μJ) characterized by a high degree of coherence and spectral stability in the whole range from 100 nm down to 4 nm. We report about the recent achievement of FERMI FELs and our experience with operations for user requiring specific FEL configurations.

  9. Colorado longitudinal twin study of reading disability.

    PubMed

    Wadsworth, Sally J; DeFries, John C; Olson, Richard K; Willcutt, Erik G

    2007-12-01

    The primary objectives of the present study are to introduce the Colorado Longitudinal Twin Study of Reading Disability, the first longitudinal twin study in which subjects have been specifically selected for having a history of reading difficulties, and to present some initial assessments of the stability of reading performance and cognitive abilities in this sample. Preliminary examination of the test scores of 124 twins with a history of reading difficulties and 154 twins with no history of reading difficulties indicates that over the 5- to 6-year interval between assessments, cognitive and reading performance are highly stable. As a group, those subjects with a history of reading difficulties had substantial deficits relative to control subjects on all measures at initial assessment, and significant deficits remained at follow-up. The stability noted for all cognitive and achievement measures was highest for a composite measure of reading, whose average stability correlation across groups was 0.80. Results of preliminary behavior genetic analyses for this measure indicated that shared genetic influences accounted for 86% and 49% of the phenotypic correlations between the two assessments for twin pairs with and without reading difficulties, respectively. In addition, genetic correlations reached unity for both groups, suggesting that the same genetic influences are manifested at both time points.

  10. Parental mediation and cyberbullying - a longitudinal study.

    PubMed

    Chng, Grace S; Liau, Albert; Khoo, Angeline; Li, Dongdong

    2014-01-01

    Parents use active and restrictive mediation strategies to guide and regulate children's online participation and the online risks they encounter. However, changes in parental mediation do occur over time and the effectiveness of these strategies on cyberbullying demands for further empirical investigation. The current study addresses these issues with a sample of 1084 students (49% girls) in a longitudinal, three-wave design. Gender differences were tested via multi-group analyses. Longitudinal growth models showed that parental use of both active and restrictive mediation decreased over time. For both types of mediation, the mean rate of change had a significant effect on boys' engagement in cyberbullying, but not for girls. Initial levels of restrictive mediation, but not active mediation, were found to be significantly predictive of cyberbullying in both genders. Girls had higher initial levels of both parental mediation types in comparison to boys. The results reveal that the effectiveness of active and restrictive mediation in relation to students' cyberbullying differs and informs us on gender differences. The implications of these results for parental education in online mediation are discussed.

  11. X-band prebunched FEL amplifier

    SciTech Connect

    Saito, Kazuyoshi; Takayama, Ken; Ozaki, Toshiyuki

    1995-12-31

    Following the successful results of the ion-channel-guiding FEL experiments, we began a new experiment {open_quotes}prebunched FEL{close_quotes}. It is an FEL driven by prebunched beams, whose configuration is a normal FEL system with a prebuncher like the bunching section of a klystron. There are two purposes in this prebunched FEL system; (1) Demonstration of a compact/efficient FEL. Attaining the saturation power level with a short wiggler length (compact wiggler) and enhancing the power through the remaining wiggler length by wiggler tapering (high efficiency FEL). (2) Experimental simulation of multi-stage FELs in the FEL-TBA. Examination of FEL interactions with prebunched injection beams, especially, about the controllability of the output RF phase by changing the RF phase of the input seed power to the wiggler. Recent experimental results show: (1) The saturation power of 120MW has been attained at the wiggler length of 1.1m by 1.5MeV prebunched beams with a 45%-modulated 750A current. However, enhanced power has not been observed yet by wiggler tapering. (2) The current modulation of the injection beam (1.5MeV-500A) becoming higher than 30%, the adjustable range of the output RF phase was limitted less than 40 degrees by the input power of 60kW only. Detail explanations of design concept, theoretical and experimental results will be presented at the conference.

  12. Optimisation of An HHG-Seeded Harmonic Cascade FEL Design for the NLS Project

    SciTech Connect

    Dunning, David; Thompson, Neil; Bartolini, Riccardo; Geng, Huiping; Huang, Zhirong; McNeil, Brian; /Strathclyde U.

    2012-06-25

    Optimization studies of an HHG-seeded harmonic cascade FEL design for the UK's proposed New Light Source (NLS) facility are presented. Three separate FELs are planned to meet the requirements for continuous coverage of the photon energy range 50-1000 eV with variable polarization, 20 fs pulse widths and good temporal coherence. The design uses an HHG seed source tuneable from 50-100 eV to provide direct FEL seeding in this range, and one or two stage harmonic cascades to reach the higher photon energies. Studies have been carried out to optimize a harmonic cascade FEL operating at 1 keV; topics investigated include modulator configuration, seed power level and ef- fects of the HHG seed structure. FEL simulations using realistic electron beam distributions are presented and tolerance to increased emittance has been considered.

  13. A Parameter Optimization for a National SASE FEL Facility

    SciTech Connect

    Yavas, O.; Yigit, S.

    2007-04-23

    The parameter optimization for a national SASE FEL facility was studied. Turkish State Planing Organization (DPT) gave financial support as an inter-universities project to begin technical design studies and test facility of National Accelerator Complex starting from 2006. In addition to a particle factory, the complex will contain a linac based free electron laser, positron ring based synchrotron radiation facilities and a proton accelerator. In this paper, we have given some results of main parameters of SASE FEL facility based on 130 MeV linac, application potential in basic and applied research.

  14. FEL GAIN LENGTH AND TAPER MEASUREMENTS AT LCLS

    SciTech Connect

    Ratner, D.; Fawley, W. M.; Brachmann, A.; Decker, F.J.; Ding, Y.; Dowell, D.; Emma, P.; Frisch, J.; Gilevich, S.; Hays, G.; Hering, P.; Huang, Z.; Loos, H.; Miahnahri, A.; Nuhn, H.D.; Turner, J.; Welch, J.; White, W.; Wu, J.; Xiang, D.; Yocky, G.; Fawley, W. M.

    2009-08-14

    We present experimental studies of the gain length and saturation power level from 1.5 nm to 1.5 Angstroms at the Linac Coherent Light Source (LCLS). By disrupting theFEL process with an orbit kick, we are able to measure the X-ray intensity as a function of undulator length. This kick method is cross-checked with the method of removing undulator sections. We also study the FEL-induced electron energy loss after saturation to determine the optimal taper of the undulator K values. The experimental results are compared to theory and simulations.

  15. FEL Gain Length and Taper Measurements at LCLS

    SciTech Connect

    Ratner, Daniel; Brachmann, A.; Decker, F.J.; Ding, Y.; Dowell, D.; Emma, P.; Frisch, J.; Gilevich, S.; Hays, G.; Hering, P.; Huang, Z.; Iverson, R.; Loos, H.; Miahnahri, A.; Nuhn, H.D.; Turner, J.; Welch, J.; White, W.; Wu, J.; Xiang, D.; Yocky, G.; /SLAC /LBL, Berkeley

    2010-07-30

    We present experimental studies of the gain length and saturation power level from 1.5 nm to 1.5 {angstrom} at the Linac Coherent Light Source (LCLS). By disrupting the FEL process with an orbit kick, we are able to measure the X-ray intensity as a function of undulator length. This kick method is cross-checked with the method of removing undulator sections. We also study the FEL-induced electron energy loss after saturation to determine the optimal taper of the undulator K values. The experimental results are compared to theory and simulations.

  16. FERMI@Elettra FEL Design Technical Optimization Final Report

    SciTech Connect

    Fawley, William; Penn, Gregory; Allaria, Enrico; De Ninno,Giovanni; Graves, William

    2006-07-31

    This is the final report of the FEL Design Group for the Technical Optimization Study for the FERMI{at}ELETTRA project. The FERMI{at}ELETTRA project is based on the principle of harmonic upshifting of an initial ''seed'' signal in a single pass, FEL amplifier employing multiple undulators. There are a number of FEL physics principles which underlie this approach to obtaining short wavelength output: (1) the energy modulation of the electron beam via the resonant interaction with an external laser seed (2) the use of a chromatic dispersive section to then develop a strong density modulation with large harmonic overtones (3) the production of coherent radiation by the microbunched beam in a downstream radiator. Within the context of the FERMI project, we discuss each of these elements in turn.

  17. Performance of hole coupling resonator in the presence of asymmetric modes and FEL gain

    SciTech Connect

    Xie, Ming; Kim, Kwang-Je.

    1991-08-01

    We continue the study of the hole coupling resonator for free electron laser (FEL) application. The previous resonator code is further developed to include the effects of the azimutally asymmetric modes and the FEL gain. The implication of the additional higher order modes is that there are more degeneracies to be avoided in tuning the FEL wavelengths. The FEL interaction is modeled by constructing a transfer map in the small signal regime and incorporating it into the resonator code. The FEL gain is found to be very effective in selecting a dominant mode from the azimuthally symmetric class of modes. Schemes for broad wavelength tuning based on passive mode control via adjustable apertures are discussed. 12 refs., 7 figs., 1 tab.

  18. Monoclonal antibodies to the major feline allergen Fel d I. II. Single step affinity purification of Fel d I, N-terminal sequence analysis, and development of a sensitive two-site immunoassay to assess Fel d I exposure.

    PubMed

    Chapman, M D; Aalberse, R C; Brown, M J; Platts-Mills, T A

    1988-02-01

    techniques will allow full structural and antigenic analysis of Fel d I and more detailed studies on the relationship between cat antigen exposure and the development of asthma.

  19. Psychosocial adjustment to ALS: a longitudinal study.

    PubMed

    Matuz, Tamara; Birbaumer, Niels; Hautzinger, Martin; Kübler, Andrea

    2015-01-01

    For the current study the Lazarian stress-coping theory and the appendant model of psychosocial adjustment to chronic illness and disabilities (Pakenham, 1999) has shaped the foundation for identifying determinants of adjustment to ALS. We aimed to investigate the evolution of psychosocial adjustment to ALS and to determine its long-term predictors. A longitudinal study design with four measurement time points was therefore, used to assess patients' quality of life, depression, and stress-coping model related aspects, such as illness characteristics, social support, cognitive appraisals, and coping strategies during a period of 2 years. Regression analyses revealed that 55% of the variance of severity of depressive symptoms and 47% of the variance in quality of life at T2 was accounted for by all the T1 predictor variables taken together. On the level of individual contributions, protective buffering, and appraisal of own coping potential accounted for a significant percentage in the variance in severity of depressive symptoms, whereas problem management coping strategies explained variance in quality of life scores. Illness characteristics at T2 did not explain any variance of both adjustment outcomes. Overall, the pattern of the longitudinal results indicated stable depressive symptoms and quality of life indices reflecting a successful adjustment to the disease across four measurement time points during a period of about two years. Empirical evidence is provided for the predictive value of social support, cognitive appraisals, and coping strategies, but not illness parameters such as severity and duration for adaptation to ALS. The current study contributes to a better conceptualization of adjustment, allowing us to provide evidence-based support beyond medical and physical intervention for people with ALS.

  20. Psychosocial adjustment to ALS: a longitudinal study

    PubMed Central

    Matuz, Tamara; Birbaumer, Niels; Hautzinger, Martin; Kübler, Andrea

    2015-01-01

    For the current study the Lazarian stress-coping theory and the appendant model of psychosocial adjustment to chronic illness and disabilities (Pakenham, 1999) has shaped the foundation for identifying determinants of adjustment to ALS. We aimed to investigate the evolution of psychosocial adjustment to ALS and to determine its long-term predictors. A longitudinal study design with four measurement time points was therefore, used to assess patients' quality of life, depression, and stress-coping model related aspects, such as illness characteristics, social support, cognitive appraisals, and coping strategies during a period of 2 years. Regression analyses revealed that 55% of the variance of severity of depressive symptoms and 47% of the variance in quality of life at T2 was accounted for by all the T1 predictor variables taken together. On the level of individual contributions, protective buffering, and appraisal of own coping potential accounted for a significant percentage in the variance in severity of depressive symptoms, whereas problem management coping strategies explained variance in quality of life scores. Illness characteristics at T2 did not explain any variance of both adjustment outcomes. Overall, the pattern of the longitudinal results indicated stable depressive symptoms and quality of life indices reflecting a successful adjustment to the disease across four measurement time points during a period of about two years. Empirical evidence is provided for the predictive value of social support, cognitive appraisals, and coping strategies, but not illness parameters such as severity and duration for adaptation to ALS. The current study contributes to a better conceptualization of adjustment, allowing us to provide evidence-based support beyond medical and physical intervention for people with ALS. PMID:26441696

  1. RF FEL for power beaming

    NASA Astrophysics Data System (ADS)

    Burke, Robert

    The laser device components associated with operating a radio frequency-free electron laser (RF-FEL) for beaming power from Earth were designed and tested. Analysis of the power beaming system requirements reveals that the FEL, identified by NASA as the laser of choice, is the major subsystem requiring demonstration before proceeding further in proving the efficacy of laser power beaming. Rocketdyne has identified a series of low cost, low risk demonstrations which proceed sequentially, as follows: (1) a 1 kW proof-of-principle demonstration; (2) a 150 kW demonstration of beaming power to a satellite; and (3) a MW class demonstration of Earth to lunar surface power transmission. This sequence of events can be completed in 5.5 years at a cost of $188M, with key milestones each year.

  2. Design and Start-to-End Simulation of an X-Band RF Driven Hard X-Ray FEL with LCLS Injector

    SciTech Connect

    Sun, Yipeng; /SLAC

    2012-08-20

    In this note, it is briefly discussed the accelerator design and start-to-end 3D macro particles simulation (using ELEGANT and GENESIS) of an X-band RF driven hard X-ray FEL with LCLS injector. A preliminary design and LiTrack 1D simulation studies were presented before in an older publication [1]. In numerical simulations this X-band RF driven hard X-ray FEL achieves/exceeds LCLS-like performance in a much shorter overall length of 350 m, compared with 1200 m in the LCLS case. One key feature of this design is that it may achieve a higher final beam current of 5 kA plus a uniform energy profile, mainly due to the employment of stronger longitudinal wake fields in the last X-band RF linac [2].

  3. Optimization of precursor synthesis, formulation and stability of 1′-[18 F] fluoroethyl-β-d-lactose ([18 F]FEL) for preclinical studies in detection of pancreatic cancer

    PubMed Central

    Paolillo, Vincenzo; De Palatis, Louis; Alauddin, Mian M.

    2014-01-01

    Introduction 1′-[18 F]Fluoroethyl-β-d-lactose ([18 F]FEL) is a new PET imaging agent for early detection of pancreatic cancer and hepatocellular carcinoma. We previously reported the syntheses of [18 F]FEL using a bromo- and a tosyl- precursor, followed by an improved method using a nosyl-precursor. However, some steps in the synthesis of the precursor appeared to be problematic producing low yields. Here, we report on an optimized method for synthesis of the precursor and production of [18 F]FEL; we also describe [18 F]FEL’s formulation and stability. Methods Acetylation of d-lactose 1 was performed following a literature procedure to obtain 1′,2′,3′,6′,2,3,4,6-d-lactose octa-acetate 2a/2b. Bromination of 2a/2b was performed using HBr/acetic acid to produce 1'-bromo-2′,3′,6′,2,3,4,6-hepta-O-acetyl-α-d-lactose 3. Coupling of 3 with ethylene glycol was performed in the presence of Ag-tosylate and an excess of ethylene glycol to produce 4a. Compound 4a was reacted with p-nitrophenylsulfonyl chloride to produce the nosyl derivative 5. Radiofluorination of 5 was performed using K[18 F]fluoride/kryptofix to obtain 6, which was purified by HPLC and hydrolyzed with Na-methoxide to produce 7. Results Compound 2 (2a/2b) was obtained in 83% yield as a mixture of two anomeric products. Compound 3 was obtained from the 2a/2b mixture in 80% yield as one product. Coupling of 3 with ethylene glycol produced 4a in 90% yield. Compound 5 was obtained in 64% yield, and radiofluorination of 5 produced 6 in 62.5% ± 7.5% yields (n = 8). Hydrolysis of 6 with Na-methoxide produced 7 in 42.0% ± 7.0% yield (n = 8) from the end of bombardment. Conclusions A simple 4-step synthesis of the precursor, compound 5, has been achieved with improved yields. A new formulation of [18 F]FEL has been developed that allows the product to remain stable at ambient temperature for use in animal studies. This improved synthesis of the precursor and stable formulation of [18 F]FEL should

  4. Prospects for the FEL (Free Electron Laser)

    SciTech Connect

    Sessler, A.M.

    1989-04-01

    The future for FELs depends upon the very large number of applications which is envisioned for them. These grow out of the FEL extensive range of wavelengths, tunability, and high power capability. High power requires demonstration of optical guiding. Tunability has already been demonstrated. And the effort to extend the range of wavelengths is ever ongoing. The future will also bring more work on gas-loaded FELs, on electromagnetic wigglers, and on harmonic generation. We can, also, look forward to observation of various new effects, a few of which will be described. Finally, a list of various FEL projects around the world will be given. 12 refs., 5 figs., 8 tabs.

  5. Status report on the development of a high-power UV/IR FEL at CEBAF

    SciTech Connect

    Benson, S.; Bohn, C.; Dylla, H.F.

    1995-12-31

    Last year we presented a design for a kilowatt industrial UV FEL based on a superconducting RF accelerator delivering 5 mA of electron-beam current at 200 MeV with energy recovery to enhance efficiency. Since then, we have progressed toward resolving several issues associated with that design. More exact simulations of the injector have resulted in a more accurate estimate of the injector performance. A new injection method has reduced the longitudinal and transverse emittance at the linac entrance. A more compact lattice has been designed for the UV FEL, and a new recirculation scheme has been identified which greatly increases the threshold for longitudinal instabilities. We decided to use a wiggler from the Advanced Photon Source which leads to a robust high-gain FEL. Analysis of the stability of an RF control system based on CEBAF control modules indicates that only minor modifications will be needed to apply them to this FEL. Detailed magnet specifications, vacuum-chamber beam apertures, and diagnostic specifications have been developed for the recirculation arcs. The design of the optical cavity has been conceptualized, and control systems have been devised to regulate mirror distortion. A half-scale model of one of the end-corner cubes has been built and tested. Finally, three-dimensional simulations have been carried out which indicate that the FEL should exceed its minimum design goals with adequate performance margin.

  6. Cuba's Aging and Alzheimer Longitudinal Study.

    PubMed

    Llibre-Rodríguez, Juan de Jesús; Valhuerdi-Cepero, Adolfo; López-Medina, Ana M; Noriega-Fernández, Lisseth; Porto-Álvarez, Rutbeskia; Guerra-Hernández, Milagros A; Bosch-Bayard, Rodolfo I; Zayas-Llerena, Tania; Hernandez-Ulloa, Elaine; Rodríguez-Blanco, Ana L; Salazar-Pérez, Enrique; Llibre-Guerra, Juan C; Llibre-Guerra, Jorge J; Marcheco-Teruel, Beatriz

    2017-01-01

    Aging and Alzheimer is a prospective, longitudinal cohort study involving 2944 adults aged ≥65 years from selected areas in Cuba's Havana and Matanzas Provinces. This door-to-door study, which began in 2003, includes periodic assessments of the cohort based on an interview; physical exam; anthropometric measurements; and diagnosis of dementia and its subtypes, other mental disorders, and other chronic non-communicable diseases and their risk factors. Information was gathered on sociodemographic characteristics; disability, dependency and frailty; use of health services; and characteristics of care and caregiver burden. The first assessment also included blood tests: complete blood count, blood glucose, kidney and liver function, lipid profile and ApoE4 genotype (a susceptibility marker). In 2007-2011, the second assessment was done of 2010 study subjects aged ≥65 years who were still alive. The study provides data on prevalence and incidence of dementia and its risk factors, and of related conditions that affect the health of older adults. It also contributes valuable experiences from field work and interactions with older adults and their families. Building on lessons learned, a third assessment to be done in 2016-2018 will incorporate a community intervention strategy to respond to diseases and conditions that predispose to dementia, frailty and dependency in older adults. KEYWORDS Dementia, Alzheimer disease, chronic disease, aging, chronic illness, frailty, dependency, cohort studies, Cuba.

  7. Objectives, Design, and History of the National Longitudinal Study.

    ERIC Educational Resources Information Center

    Davis, J. A.; Collins, Elmer

    The National Longitudinal Study of the High School Class of 1972 (NLS) is a federally supported longitudinal study of a national sample of some 23,000 young people first surveyed as high school seniors in the spring of 1972. The historical precedents of such a study include the work of Friend and Haggert in a Boston settlement house, Louis…

  8. Objectives, Design, and History of the National Longitudinal Study.

    ERIC Educational Resources Information Center

    Davis, J. A.; Collins, Elmer

    The National Longitudinal Study of the High School Class of 1972 (NLS) is a federally supported longitudinal study of a national sample of some 23,000 young people first surveyed as high school seniors in the spring of 1972. The historical precedents of such a study include the work of Friend and Haggert in a Boston settlement house, Louis…

  9. The Impact of Mixing Modes on Reliability in Longitudinal Studies

    ERIC Educational Resources Information Center

    Cernat, Alexandru

    2015-01-01

    Mixed-mode designs are increasingly important in surveys, and large longitudinal studies are progressively moving to or considering such a design. In this context, our knowledge regarding the impact of mixing modes on data quality indicators in longitudinal studies is sparse. This study tries to ameliorate this situation by taking advantage of a…

  10. A Longitudinal Study of Adolescent Adjustment Following Family Transitions

    ERIC Educational Resources Information Center

    Ruschena, Eda; Prior, Margot; Sanson, Ann; Smart, Diana

    2005-01-01

    Background: This study examined the impact of family transitions, that is, parental separation, divorce, remarriage and death, upon the lives of Australian children and adolescents in a longitudinal study of temperament and development. Methods: Using longitudinal and concurrent questionnaire data, outcomes for young people experiencing…

  11. Early Predictors of Adolescent Depression: A 7-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Mazza, James J.; Abbott, Robert D.; Fleming, Charles B.; Harachi, Tracy W.; Cortes, Rebecca C.; Park, Jisuk; Haggerty, Kevin P.; Catalano, Richard F.

    2009-01-01

    This study examined the longitudinal relationship of early elementary predictors to adolescent depression 7 years later. The sample consisted of 938 students who have been part of a larger longitudinal study that started in 1993. Data collected from parents, teachers, and youth self-reports on early risk factors when students were in 1st and 2nd…

  12. Beyond Terman: Contemporary Longitudinal Studies of Giftedness and Talent.

    ERIC Educational Resources Information Center

    Subotnik, Rena F., Ed.; Arnold, Karen D., Ed.

    This volume presents 16 papers describing recent longitudinal studies of giftedness. Papers have the following titles and authors: (1) "Longitudinal Study of Giftedness and Talent" (Rena F. Subotnik and Karen D. Arnold); (2) "The Illinois Valedictorian Project: Early Adult Careers of Academically Talented Male High School Students" (Karen D.…

  13. Adolescent stress and coping: a longitudinal study.

    PubMed

    Groër, M W; Thomas, S P; Shoffner, D

    1992-06-01

    The purpose of this longitudinal panel study was to investigate developmental and gender influences on stress and coping in adolescents attending a suburban high school in Tennessee. Data were collected from the same 167 subjects during the freshman year and again during the senior year. Life events stress was measured through the Adolescent Life Change Event Scale (ALCES) and ways of coping were categorized from data gathered from an open-ended questionnaire. Girls reported more life events stress at both testings than boys. Life events stress was greater at senior testing for both girls and boys, but girls' scores increased more. The "gender intensification" phenomenon may account for the greater disparity in types of stress reported by boys and girls as seniors. Girls generally reported more life events associated with interpersonal and family relationships. Both girls and boys reported coping with stress mostly through active distraction techniques such as exercise. However, girls' use of active distraction decreased over time, while passive distraction increased. Self-destructive and aggressive coping behaviors increased for boys. There were no relationships between amounts or types of life events stress and ways of coping for subjects at either time.

  14. NASA Planetary Science Summer School: Longitudinal Study

    NASA Astrophysics Data System (ADS)

    Giron, Jennie M.; Sohus, A.

    2006-12-01

    NASA’s Planetary Science Summer School is a program designed to prepare the next generation of scientists and engineers to participate in future missions of solar system exploration. The opportunity is advertised to science and engineering post-doctoral and graduate students with a strong interest in careers in planetary exploration. Preference is given to U.S. citizens. The “school” consists of a one-week intensive team exercise learning the process of developing a robotic mission concept into reality through concurrent engineering, working with JPL’s Advanced Project Design Team (Team X). This program benefits the students by providing them with skills, knowledge and the experience of collaborating with a concept mission design. A longitudinal study was conducted to assess the impact of the program on the past participants of the program. Data collected included their current contact information, if they are currently part of the planetary exploration community, if participation in the program contributed to any career choices, if the program benefited their career paths, etc. Approximately 37% of 250 past participants responded to the online survey. Of these, 83% indicated that they are actively involved in planetary exploration or aerospace in general; 78% said they had been able to apply what they learned in the program to their current job or professional career; 100% said they would recommend this program to a colleague.

  15. Technical report of biota, FEL Site 1, Lawrence Livermore National Laboratory: Final report

    SciTech Connect

    Taylor, D.W.; Davilla, W.; Orloff, S.

    1986-09-26

    Lawrence Livermore National Laboratory is considering an expansion of laser test facilities adjacent to its existing LLNL Site 300 test location. Construction of a free-electron laser, known as the FEL Project, is being considered on approximately 3900 hectates (10,500 acres) of land. We will refer to this proposed site as FEL Site 1. Knowledge of the flora and vegetation resources of the proposed FEL Site 1 is necessary in order to plan for construction, operation, and possible future expansion of the FEL facility. The purpose of botanical sections of this report is to quantitatively describe the variation of vegetation on FEL Site 1, and to relate the vegetation to potential environmental impacts associated with present operation and possible expansion of site facilities. The primary purpose of the wildlife studies was to determine the presence and status of any endangered, threatened, fully protected, or otherwise sensitive species on FEL Site 1 that might be affected by the proposed FEL project. We directed our studies mainly toward the federally endangered San Joaquin kit fox (Vulpes macrotis mutica), but also toward another 14 special status species that potentially occur on site, including the state threatened Alameda striped racer (Masticophis lateralis euryxanthus).

  16. Compact FEL`s based on slow wave wigglers

    SciTech Connect

    Riyopoulos, S.

    1995-12-31

    Slow waves excited in magnetron-type cavities are attractive canditates as wigglers for compact Free Electron Lasers. Because of group velocities much below the speed of light, slow waves offer an order of magnitude increase in FEL gain under given circulating power in the wiggler resonator, compared to fast wave wigglers of similar period. In addition, they offer the versatility of operation either at modest beam energy via upshifing of the fundamental wavelength, or at low beam energy benefiting from the submillimeter wiggler harmonics. Because the main electron undulation is in the transverse direction for all spatial harmonics, the radiated power is increased by a factor {gamma}{sup 2} relative to the Smith-Purcell approach that relies on axial electron undulation. Technical advantages offered by magnetron-type wiggles are: the generation of the wiggler microwaves and the FEL interaction take place inside the same cavity, avoiding the issue of high power coupling between cavities; the excitation of wiggler microwaves relies on distributed electron emission from the cavity wall and does not require separate beam injection.

  17. A Comparison of Short Rayleigh Range FEL Performance with Simulations

    SciTech Connect

    Benson, Stephen; Evtushenko, Pavel; Michelle D. Shinn; Neil, George; Blau, Joe; Burggraff, D.; Colson, William; Crooker, P.P.; Sans Aguilar, J.

    2007-08-01

    One approach to attaining very high power in a free-electron laser (FEL) is to operate with a Rayleigh range much smaller than the wiggler length. Previously, 3D simulations of Free-electron laser (FEL) oscillators showed that FEL gain doesn't fall off with Rayleigh range as predicted by one-dimensional simulations*. They also predict that the angular tolerance for the mirrors is much large than simplistic theory predicts. Using the IR Upgrade laser at Jefferson Lab lasing at 935 nm we have studied the performance of an FEL with very short Rayleigh range. We also looked at the angular sensitivity for several different Rayleigh ranges. We find very good agreement between simulations and measured gain and angular sensitivities. Surprisingly the gain continues to rise as the Rayleigh range is shortened and continues to grow even when the resonator becomes geometrically unstable. The same behavior is seen in both the experiment and simulations. We also find that, even for large Rayleigh r

  18. Ultrafast Coherent Control and Characterization of Surface Reactions using FELs

    SciTech Connect

    Ogasawara, Hirohito; Nordlund, Dennis a Nilsson, Anders; /SLAC, SSRL

    2005-09-30

    The microscopic understanding of reactions at surfaces requires an in-depth knowledge of the dynamics of elementary processes on an ultrafast timescale. This can be accomplished using an ultrafast excitation to initiate a chemical reaction and then probe the progression of the reaction with an ultrashort x-ray pulse from the FEL. There is a great potential to use atom-specific spectroscopy involving core levels to probe the chemical nature, structure and bonding of species on surfaces. The ultrashort electron pulse obtained in the linear accelerator to feed the X-ray FEL can also be used for generation of coherent synchrotron radiation in the low energy THz regime to be used as a pump. This radiation has an energy close to the thermal excitations of low-energy vibrational modes of molecules on surfaces and phonons in substrates. The coherent THz radiation will be an electric field pulse with a certain direction that can collectively manipulate atoms or molecules on surfaces. In this respect a chemical reaction can be initiated by collective atomic motion along a specific reaction coordinate. If the coherent THz radiation is generated from the same source as the X-ray FEL radiation, full-time synchronization for pump-probe experiments will be possible. The combination of THz and X-ray spectroscopy could be a unique opportunity for FEL facilities to conduct ultrafast chemistry studies at surfaces.

  19. Recent developments in CrystFEL 1

    PubMed Central

    White, Thomas A.; Mariani, Valerio; Brehm, Wolfgang; Yefanov, Oleksandr; Barty, Anton; Beyerlein, Kenneth R.; Chervinskii, Fedor; Galli, Lorenzo; Gati, Cornelius; Nakane, Takanori; Tolstikova, Alexandra; Yamashita, Keitaro; Yoon, Chun Hong; Diederichs, Kay; Chapman, Henry N.

    2016-01-01

    CrystFEL is a suite of programs for processing data from ‘serial crystallography’ experiments, which are usually performed using X-ray free-electron lasers (FELs) but also increasingly with other X-ray sources. The CrystFEL software suite has been under development since 2009, just before the first hard FEL experiments were performed, and has been significantly updated and improved since then. This article describes the most important improvements which have been made to CrystFEL since the first release version. These changes include the addition of new programs to the suite, the ability to resolve ‘indexing ambiguities’ and several ways to improve the quality of the integrated data by more accurately modelling the underlying diffraction physics. PMID:27047311

  20. Longitudinal respiratory studies in older people

    PubMed Central

    Milne, J S

    1978-01-01

    Milne, J S (1978).Thorax, 33, 547-554. Longitudinal respiratory studies in older people. A random sample of older people in Edinburgh (215 men, 272 women aged 62-90 years) was examined with the MRC questionnaire on respiratory symptoms. The FEV1 and FVC were recorded. Spirograms were repeated after one and five years and the questions after five years, the sample by then having been reduced to 133 men and 148 women. After five years 7% of the surviving men and women had developed persistent cough and phlegm. This syndrome had disappeared in 12% of men and 2% of women. Dyspnoea had increased beyond grade 2 in 13% of men and 7% of women and had lessened only in 6% of women. One-quarter of male and one-seventh of female cigarette smokers had given up smoking, mostly in the first year. Nearly all who stopped were symptomless before and after. In those men who stopped smoking before the study began symptom prevalence was similar to that in those who continued smoking. Mean values of FEV1 and FVC declined as age increased, the decline being greater in FVC with resulting rise in FEV1%. Five-year differences in FEV1 and FVC were symmetrically distributed with mean differences increasing with age. Mean differences in FEV1 were 280-350 ml in men and 150-230 ml in women. Prediction equations from the first examinations remained usable for clinical work. Mean values of FEV1 and FVC at the first examination were smaller in those who died compared with survivors, whether symptoms were present or not. The prevalence of symptoms was greater in those who died. PMID:725823

  1. Integrated computer simulation on FIR FEL dynamics

    SciTech Connect

    Furukawa, H.; Kuruma, S.; Imasaki, K.

    1995-12-31

    An integrated computer simulation code has been developed to analyze the RF-Linac FEL dynamics. First, the simulation code on the electron beam acceleration and transport processes in RF-Linac: (LUNA) has been developed to analyze the characteristics of the electron beam in RF-Linac and to optimize the parameters of RF-Linac. Second, a space-time dependent 3D FEL simulation code (Shipout) has been developed. The RF-Linac FEL total simulations have been performed by using the electron beam data from LUNA in Shipout. The number of particles using in a RF-Linac FEL total simulation is approximately 1000. The CPU time for the simulation of 1 round trip is about 1.5 minutes. At ILT/ILE, Osaka, a 8.5MeV RF-Linac with a photo-cathode RF-gun is used for FEL oscillation experiments. By using 2 cm wiggler, the FEL oscillation in the wavelength approximately 46 {mu}m are investigated. By the simulations using LUNA with the parameters of an ILT/ILE experiment, the pulse shape and the energy spectra of the electron beam at the end of the linac are estimated. The pulse shape of the electron beam at the end of the linac has sharp rise-up and it slowly decays as a function of time. By the RF-linac FEL total simulations with the parameters of an ILT/ILE experiment, the dependencies of the start up of the FEL oscillations on the pulse shape of the electron beam at the end of the linac are estimated. The coherent spontaneous emission effects and the quick start up of FEL oscillations have been observed by the RF-Linac FEL total simulations.

  2. Polarization Analysis for Seeded FELs in a Crossed-Planar Undulator

    SciTech Connect

    Geng, Huiping; Ding, Yuantao; Huang, Zhirong; Bartolini, Riccardo; Dunning, David; Thompson, Neil; /Daresbury

    2012-06-25

    The crossed-planar undulator is a promising scheme for full polarization control in x-ray FELs. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable at fundamental wavelength just before saturation. In this paper, we study the effectiveness of a crossed undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered. Simulations with realistic beam distributions show that a degree of circular polarization of over 90% and 80% is obtainable at the fundamental and 2nd harmonic frequencies, respectively.

  3. A Dynamic Feedback Model for High Repetition Rate LINAC-Driven FELS

    SciTech Connect

    Mellado Munoz, M.; Doolittle, L.; Emma, P.; Huang, G.; Ratti, A.; Serrano, C.; Byrd, J. M.

    2012-05-20

    One of the concepts for the next generation of linacdriven FELs is a CW superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the stability of the xray pulses by improving the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. A high repetition rate FEL with a CW linac presents an opportunity to use a variety of broadband feedbacks to stabilize the beam parameters. To understand the performance of such a feedback system, we are developing a dynamic model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and includes the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we present a detailed description of this model.

  4. On a theory of an FEL amplifier with circular waveguide and guiding magnetic field

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    We consider an FEL amplifier with an axisymmetric electron beam, circular waveguide, helical undulator and guiding magnetic field. The presented nonlinear theory of the FEL amplifier is based on Hamiltonian description of particle motion and radiation field representation with Green function method. The space charge fields, energy spread and diffraction effects are taken into consideration. Such an FEL amplifier configuration possesses some peculiarities when it operates in a regime with the negative longitudinal mass (i.e. when{mu}{sup -1}{proportional_to}dv{sub z}/dE < 0). It is shown that in the presence of strong space charge fields, the so-called {open_quotes}negative mass{close_quotes} instability may influence significantly on the FEL amplifier operation resulting in a significant increase in the FEL amplifier efficiency. It is proposed in the presented paper to use the effect of the {open_quotes}negative mass instability{close_quotes} to achieve an effective bunching of the CERN Linear Collider (LIC) driving beam.

  5. Diffraction and pulse slippage in the Boeing 1 kW FEL oscillator

    SciTech Connect

    Blau, J.; Wong, R.K.; Colson, W.B.

    1995-12-31

    A four-dimensional simulation in x, y, z, and t, including betatron motion of the electrons, is used to study the combined effects of diffraction, pulse slippage and desynchronism in the Boeing 1 kW FEL oscillator.

  6. Laser-Pumped Coherent X-Ray FEL

    DTIC Science & Technology

    2008-11-14

    laser field replaces the magnetic wiggler field of a conventional FEL. Depending on the intensity and quality of both the electron beam and pump laser...and Line Width 16 IV. Comparison of Theory with Simulations 17 a) Wiggler based X-Ray FEL 17 b) Laser Pumped X-Ray FEL 18 V. Conclusions 19...FEL) an intense laser field replaces the magnetic wiggler field of a conventional FEL. Depending on the intensity and quality of both the electron

  7. Immunological differences in the global release of the major cat allergen Fel d 1 are influenced by sex and behaviour.

    PubMed

    Bienboire-Frosini, Cécile; Cozzi, Alessandro; Lafont-Lecuelle, Céline; Vervloet, Daniel; Ronin, Catherine; Pageat, Patrick

    2012-07-01

    The biological function of Fel d 1, the major cat allergen released in the environment, is still unclear despite studies suggesting a putative role in chemical communication. Structural and immunological polymorphisms of Fel d 1 have been described. This study examined how Fel d 1 immunological polymorphism may have a physiological origin by estimating a potential relationship with the sex of cats and cat-human interactions. Samples from bath washes of 21 cats were screened to study antibody binding to Fel d 1 using an ELISA. Personality and Tolerance Handling scores were used to assess the behaviour of the cats. In the washes, Fel d 1 concentrations were significantly lower in females than in males (P<0.05). Slopes from the ELISA dose-dependent curves varied among the cats: males secreted Fel d 1 variants with higher antibody recognition than females (P<0.01). Females that were aggressive and difficult to handle displayed a diminished slope value, and therefore a weaker Fel d 1 immunoreactivity in global washes, compared to females that were sociable (P=0.09) and easy to handle (P=0.07). This study shows a variable immunological polymorphism of Fel d 1 within a cat population, particularly between males and females, and this polymorphism appears to be related to cat-human interactions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Interactive computer program for optimal designs of longitudinal cohort studies.

    PubMed

    Tekle, Fetene B; Tan, Frans E S; Berger, Martijn P F

    2009-05-01

    Many large scale longitudinal cohort studies have been carried out or are ongoing in different fields of science. Such studies need a careful planning to obtain the desired quality of results with the available resources. In the past, a number of researches have been performed on optimal designs for longitudinal studies. However, there was no computer program yet available to help researchers to plan their longitudinal cohort design in an optimal way. A new interactive computer program for the optimization of designs of longitudinal cohort studies is therefore presented. The computer program helps users to identify the optimal cohort design with an optimal number of repeated measurements per subject and an optimal allocations of time points within a given study period. Further, users can compute the loss in relative efficiencies of any other alternative design compared to the optimal one. The computer program is described and illustrated using a practical example.

  9. High Power Operation of the JLab IR FEL Driver Accelerator

    SciTech Connect

    Kevin Beard; Stephen Benson; George Biallas; James Boyce; Donald Bullard; James Coleman; David Douglas; H. Dylla; Richard Evans; Pavel Evtushenko; Christopher Gould; Albert Grippo; Joseph Gubeli; David Hardy; Carlos Hernandez-Garcia; J. Hovater; Kevin Jordan; John Klopf; Rui Li; Steven Moore; George Neil; Benard Poelker; Thomas Powers; Joseph Preble; Robert Rimmer; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Gwyn Williams; Shukui Zhang

    2007-08-01

    Operation of the JLab IR Upgrade FEL at CW powers in excess of 10 kW requires sustained production of high electron beam powers by the driver ERL. This in turn demands attention to numerous issues and effects, including: cathode lifetime; control of beamline and RF system vacuum during high current operation; longitudinal space charge; longitudinal and transverse matching of irregular/large volume phase space distributions; halo management; management of remnant dispersive effects; resistive wall, wake-field, and RF heating of beam vacuum chambers; the beam break up instability; the impact of coherent synchrotron radiation (both on beam quality and the performance of laser optics); magnetic component stability and reproducibility; and RF stability and reproducibility. We discuss our experience with these issues and describe the modus vivendi that has evolved during prolonged high current, high power beam and laser operation.

  10. 78 FR 44553 - Agency Information Collection Activities; Comment Request; Early Childhood Longitudinal Study...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-24

    ... Agency Information Collection Activities; Comment Request; Early Childhood Longitudinal Study... notice will be considered public records. Title of Collection: Early Childhood Longitudinal Study... Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011), sponsored by the National...

  11. J's Rhymes: A Longitudinal Case Study of Language Play.

    ERIC Educational Resources Information Center

    Inkelas, Sharon

    2003-01-01

    A longitudinal study of one children documents an invented language game consisting of suffixal reduplication and onset replacement. Argues that this game may more closely resemble adult rhyme. (Author/VWL)

  12. Transverse-to-Longitudinal Emittance Exchange to Improve Performance of High-Gain Free-Electron Lasers

    SciTech Connect

    Emma, P.; Huang, Z.; Kim, K.-J.; Piot, P.; /Northern Illinois U. /Fermilab

    2006-09-21

    The ability to generate small transverse emittance is perhaps the main limiting factor for the performance of high-gain x-rays free-electron lasers (FELs). Noting that beams from an rf photocathode gun can have energy spread much smaller than required for efficient FEL interaction, we present a method to produce normalized transverse emittance at or below about 0.1 {micro}m, which will lead to a significantly shorter length undulator as well as a lower electron beam energy for an x-ray FEL project. The beam manipulation consists of producing an unequal partition of the initially equal emittances into two dissimilar emittances by a flat beam technique and exchanging the larger transverse emittance with a small longitudinal emittance. We study various issues involved in the manipulation. In particular, a new emittance exchange optics we found enables an exact emittance exchange necessary for this scheme.

  13. Synthesis and cyclic voltammetric studies of diiron complexes, ER2[(η5-C5H4)Fe(L2)Me]2 (E = C, Si, Ge, Sn; R = H, alkyl; L2 = diphosphine] and (η5-C5H5)Fe(L2)ER2Fc [Fc = (η5-C5H4)Fe(η5-C5H5)

    PubMed Central

    Kumar, Mukesh; Cervantes-Lee, Francisco; Pannell, Keith H.; Shao, Jianguo

    2009-01-01

    Summary The cyclic voltammetric studies on ER2[(η5-C5H4)Fe(L2)Me]2 (L2 = dppe; ER2 = CH2 (1a), SiMe2 (2a), GeMe2 (3a), SnMe2 (4a) revealed two well resolved reversible waves [1E1/2 = -0.33 V, 2E1/2 = -0.20 V (for 1a); 1E1/2 = -0.35 V, 2E1/2 = -0.21 V (for 2a);1E1/2 = -0.36 V, 2E1/2 = -0.23 V (for 3a);1E1/2 = -0.36 V, 2E1/2 = -0.22 V (for 4a)] in CH2Cl2 suggesting electronic communication between two iron centers which is seen for the first time in this family of organometallic complexes. The resolution between two reversible waves increases in the order of 1a < 2a < 3a < 4a; however, coordinating solvents such as pyridine, PhCN, DMSO and DMF decreased these interactions attributable to the stabilization of cationic species formed after the first oxidation. UV/Vis spectroelectrochemistry of 1a-4a revealed two distinct absorbance patterns for both redox processes and reflected the stepwise oxidation. Homobimetallic complexes containing ferrocenyl groups, (η5-C5H5)Fe(L2)ER2Fc [ER2 = none, L2 = cis-dppen (5a), ER2 = SiMe2, L2 = cis-dppen (6a), dppm (6b); ER2 = GeMe2, L2 = cis-dppen (7a), dppm (7b); ER2 = SntBu2, L2 = dmpe (8a); Fc = (η5-C5H4)Fe(η54-C5H5)] were prepared and studied in terms of electrochemistry. The cyclic voltammogram of 5a exhibited two well resolved one electron reversible waves at 1E1/2 = -0.21 V and 2E1/2 = 0.58 V corresponding to oxidation of the Fe(P-P) and Fc iron atoms respectively. Other complexes in this series (6a/6b, 7a/7b, 8a) containing direct Fe-E-Fc (E = Si, Ge and Sn) bridging units were not stable under electrochemical conditions and rupture of the Fe-E bonds was observed. PMID:19718238

  14. Statistical Analysis of Crossed Undulator for Polarization Control in a SASE FEL

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; /SLAC

    2008-02-01

    There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme (K.-J. Kim, Nucl. Instrum. Methods A 445, 329 (2000)) for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

  15. Temporal characteristics of a SASE FEL.

    SciTech Connect

    Li, Y,; Huang, Z.; Kim, K.-J.; Lewellen, J.; Milton, S. V.; Sajaev, V.

    2003-01-01

    We have performed a single-shot, time-resolved measurement of the output field of a SASE FEL using the frequency-resolved optical gating (FROG) technique. The measurement reveals the phase and the amplitude of the SASE output as functions of time and frequency, hence enables us to perform a full characterization of the SASE FEL output. We examined both the single-shot field evolution as well as the statistics over multiple shots on the phase and intensity evolution.

  16. Optical beam transport system at FEL-SUT

    NASA Astrophysics Data System (ADS)

    Nomaru, K.; Kawai, M.; Yokoyama, M.; Oda, F.; Nakayama, A.; Koike, H.; Kuroda, H.

    2000-05-01

    Kawasaki Heavy Industries Ltd. has installed an FEL beam transport system at the IR FEL Research Center of the Science University of Tokyo (FEL-SUT). This system transports the FEL output beam from the FEL machine room to the optical diagnostic room through a vacuum tube. The in-vacuum multi-mirror synchronized system operated from the FEL control room enables the operator to control the multiple mirrors simultaneously on or off axis of the FEL beam and to distribute the FEL output to one of the laboratories. The essential component of the transport system is the passive control optics that is composed of an elliptical and parabolic mirror couple. Once the control optics is aligned, a parallel FEL beam with a good pointing stability is obtained without any active operation to tune the optical system for different wavelengths.

  17. Lattice Design for a High-Power Infrared FEL

    NASA Astrophysics Data System (ADS)

    Douglas, D. R.

    1997-05-01

    A 1 kW infrared FEL, funded by the U.S. Navy, is under construction at Jefferson Lab. This device will be driven by a compact, 42 MeV, 5 mA, energy-recovering, CW SRF-based linear accelerator to produce light in the 3-6.6 μm range. The machine concept comprises a 10 MeV injector, a linac based on a single high-gradient Jefferson Lab accelerator cryomodule, a wiggler and optical cavity, and an energy-recovery recirculation arc. Energy recovery limits cost and technical risk by reducing the RF power requirements in the driver accelerator. Following deceleration to 10 MeV, the beam is dumped. Stringent phase space requirements at the wiggler, low beam energy, and high beam current subject the accelerator lattice to numerous constraints. Principal considerations include: transport and delivery to the FEL of a high-quality, high-current beam; the impact of coherent synchrotron radiation (CSR) during beam recirculation transport; beam optics aberration control, to provide low-loss energy-recovery transport of a 5% relative momentum spread, high-current beam; attention to possible beam breakup (BBU) instabilities in the recirculating accelerator; and longitudinal phase space management during beam transport, to optimize RF drive system control during energy recovery and FEL operation. The presentation will address the design process and design solution for an accelerator transport lattice that meets the requirements imposed by these physical phenomena and operational necessities.

  18. Serial snapshot crystallography for materials science with SwissFEL

    SciTech Connect

    Dejoie, Catherine; Smeets, Stef; Baerlocher, Christian; Tamura, Nobumichi; Pattison, Philip; Abela, Rafael; McCusker, Lynne B.

    2015-04-21

    New opportunities for studying (sub)microcrystalline materials with small unit cells, both organic and inorganic, will open up when the X-ray free electron laser (XFEL) presently being constructed in Switzerland (SwissFEL) comes online in 2017. Our synchrotron-based experiments mimicking the 4%-energy-bandpass mode of the SwissFEL beam show that it will be possible to record a diffraction pattern of up to 10 randomly oriented crystals in a single snapshot, to index the resulting reflections, and to extract their intensities reliably. The crystals are destroyed with each XFEL pulse, but by combining snapshots from several sets of crystals, a complete set of data can be assembled, and crystal structures of materials that are difficult to analyze otherwise will become accessible. Even with a single shot, at least a partial analysis of the crystal structure will be possible, and with 10–50 femtosecond pulses, this offers tantalizing possibilities for time-resolved studies.

  19. Acute optic nerve sheath fenestration in humans using the free electron laser (FEL): a case report

    NASA Astrophysics Data System (ADS)

    Joos, Karen M.; Mawn, Louise A.; Shen, Jin-Hui; Jansen, E. Duco; Casagrande, Vivien A.

    2002-06-01

    Our previous studies using rabbits and monkeys showed that the Amide II wavelength (6.45 micrometers ) produced by the FEL could efficiently produce an optic nerve sheath fenestration with minimal damage. In order to determine if the technology safely could be applied to human surgery, we used 2 blind human eyes during enucleation to compare the results of producing fenestrations with the FEL or a scissors. FDA and Vanderbilt IRB approvals, and individual patient consents were obtained. The FEL energy was transmitted to a human operating room. After disinsertion of the medial rectus muscle, an optic nerve sheath fenestration (2 mm diameter) was made with either the FEL (6.45 micrometers , 325 micrometers spot size, 30 Hz, 3 mJ) through a hollow waveguide surgical probe or with a scissors. The enucleation was then completed. The optic nerve was dissected from the globe and fixed. Specimens were examined histologically. Dural incisions were effective with both methods. FEL energy at 6.45 micrometers can be transmitted to an operating room and delivered to human ocular tissue through a hollow waveguide surgical probe. This FEL wavelength can produce an optic nerve sheath fenestration without acute direct damage to the nerve in this case report.

  20. A HIGH REPETITION RATE VUV-SOFT X-RAY FEL CONCEPT

    SciTech Connect

    Corlett, J.; Byrd, J.; Fawley, W.M.; Gullans, M.; Li, D.; Lidia,S.M.; Padmore, H.; Penn, G.; Pogorelov, I.; Qiang, J.; Robin, D.; Sannibale, F.; Staples, J.W.; Steier, C.; Venturini, M.; Virostek, S.; Wan, W.; Wells, R.; Wilcox, R.; Wurtele, J.; Zholents, A.

    2007-06-24

    We report on design studies for a seeded FEL light source that is responsive to the scientific needs of the future. The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, reduced gain length in the FEL, utilization of harmonics to attain shorter wavelengths, and precise synchronization of the x-ray pulse with seed laser systems. We describe an FEL facility concept based on a high repetition rate RF photocathode gun, that would allow simultaneous operation of multiple independent FEL's, each producing high average brightness, tunable over the VUV-soft x-ray range, and each with individual performance characteristics determined by the configuration of the FEL. SASE, enhanced-SASE (ESASE), seeded, harmonic generation, and other configurations making use of optical manipulations of the electron beam may be employed, providing a wide range of photon beam properties to meet varied user demands.

  1. FEL options for power beaming

    SciTech Connect

    Kim, K.J.; Zholents, A.A.; Zolotorev, M.S.; Vinokurov, N.A.

    1997-10-01

    The demand for the output power of communication satellites has been increasing exponentially. The satellite power is generated from solar panels which collect the sunlight and convert it to electrical power. The power per satellite is limited due to the limit in the practical size of the solar panel. One way to meet the power demand is to employ multiple satellites (up to 10) per the internationally agreed-upon ``slot`` in the geosynchronous earth orbit (GEO). However, this approach is very expensive due to the high cost of sending a satellite into a GEO orbit. An alternative approach is power beaming, i.e., to illuminate the solar panels with high power, highly-directed laser beams from earth. The power beaming generates more power per satellite for the same area of the solar panel. The minimum optical beam power, interesting for power beaming application, is P{sub L} = 200kW. The wavelength is chosen to be {lambda} = 0.84 {micro}m, so that it is within one of the transmission windows of the air, and at the same time near the peak of the photo-voltaic conversion efficiency of Si, which is the commonly used material for the solar panels. Free electron lasers (FELs) are well suited for the power beaming application because they can provide high power with coherent wavefront, but without high energy density in media. In this article the authors discuss some principal issues, such as the choice of accelerator and electron gun, the choice of beam parameters, radiation hazards, technological availability, and overall efficiency and reliability of the installation. They also attempt to highlight the compromise between the cost of the primary installation, the operation cost, and the choice of technology, and its maturity. They then present several schemes for the accelerator-FEL systems based on RF accelerators. The initial electron beam accelerator up to the energy of a few MeV is more or less common for all these schemes.

  2. Summary of the working group on FEL theory

    SciTech Connect

    Pellegrini, C.

    1984-01-01

    The working group on FEL theory dedicated most of its discussions to topics relevant to the high gain regime in a free electron laser. In addition the area of interest was mainly restricted to FELs for the production of XUV radiation (<1000 A). A list of the topics that were felt to be relevant is: (1) characterization of the FEL high gain regime; (2) the amplified spontaneous emission mode of operation (ASE); (3) superradiance in FELs; (4) diffraction effects for high gain FELs; (5) noise and start-up; (6) coherence properties of the radiation for the ASE and superradiant FELS. 9 references.

  3. Lorentz detuning and tuning system study of 3+1/2cell DC-SC photo-injector for PKU-FEL

    NASA Astrophysics Data System (ADS)

    Xu, Wen-Can; Quan, Sheng-Wen; Zhao, Kui; Zhu, Feng

    2008-03-01

    A 3+1/2cell DC-SC photo-injector for PKU-FEL facility is under development, which is an upgrade design of the successful 1+1/2cell DC-SC photo-injector. The Lorentz detuning and tuning structure for the 3+1/2cell superconducting cavity is presented in this paper. The Lorentz force detuning coefficient is 1.2 Hz/(MV/m)2 with double stiffening rings for the half cell and single stiffening rings between the adjacent TESLA cells. With the special stiffening structure, the 3+1/2cell whole cavity needs only one tuner. The influences of the tuning on frequency shift, field flatness and average gradient are discussed in this paper. The simulation results show that the stiffening rings' design is successful. Supported by Major State Basic Research Development Program of China (2002CB713600)

  4. Physical optics simulations with PHASE for SwissFEL beamlines

    SciTech Connect

    Flechsig, U.; Follath, R.; Reiche, S.; Bahrdt, J.

    2016-07-27

    PHASE is a software tool for physical optics simulation based on the stationary phase approximation method. The code is under continuous development since about 20 years and has been used for instance for fundamental studies and ray tracing of various beamlines at the Swiss Light Source. Along with the planning for SwissFEL a new hard X-ray free electron laser under construction, new features have been added to permit practical performance predictions including diffraction effects which emerge with the fully coherent source. We present the application of the package on the example of the ARAMIS 1 beamline at SwissFEL. The X-ray pulse calculated with GENESIS and given as an electrical field distribution has been propagated through the beamline to the sample position. We demonstrate the new features of PHASE like the treatment of measured figure errors, apertures and coatings of the mirrors and the application of Fourier optics propagators for free space propagation.

  5. Separation-Individuation of Late Adolescents : A Longitudinal Study

    ERIC Educational Resources Information Center

    Aslan, Sevda; Gelbal, Selahattin

    2016-01-01

    The aim of this study was to demonstrate the change in separation-individuation between late adolescents in the first, second, third and fourth year of higher education. The study sample used for this longitudinal study consisted of 148 students attending class studies, computer education and science education departments of Kirikkale University.…

  6. Residential characteristics predict changes in Der p 1, Fel d 1 and ergosterol but not fungi over time.

    PubMed

    Matheson, M C; Dharmage, S C; Forbes, A B; Raven, J M; Woods, R K; Thien, F C K; Guest, D I; Rolland, J M; Haydn Walters, E; Abramson, M J

    2003-09-01

    Allergen and fungal exposures are important risk factors for asthma. We conducted a longitudinal analysis of allergen levels in Melbourne homes between 1996 and 1998 to examine the effects of changing residential characteristics on allergen and fungal levels. We also examined the changes in levels of indoor allergens. The subjects were participants in the European Community Respiratory Health Survey (ECRHS) in Melbourne. In 1996, 485 subjects participated in a follow-up study, which involved both home and laboratory visits. Dust and air samples were collected from participants' bedrooms and a validated residential questionnaire was administered. In 1998, 360 participants underwent further follow-up. House dust mite (Der p 1) and cat allergens (Fel d 1) and ergosterol were measured in dust. We observed moderate within home correlations between 1996 and 1998 in floor Der p 1 (intraclass correlation ICC=0.48), bed Der p 1 (ICC=0.61), Fel d 1 (kappa=0.53) and ergosterol (ICC=0.28) levels. We found that the floor Der p 1 levels decreased from 1996 to 1998 in the homes of participants who moved to an attached home, moved their bedrooms to the first floor, removed fitted carpet or central heating. Replacing or vacuuming the mattress more than twice per year reduced levels of Der p 1 in the bed. Ergosterol levels were reduced by removing visible mould and fitted carpet. These findings provide evidence to support current advice with regard to allergen avoidance in patients with dust mite and fungal allergies.

  7. Social Class Differentiation in Cognitive Development: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Golden, Mark; And Others

    In an effort to isolate the emergence and causes of social class differences in intellectual performance, this longitudinal study was undertaken as a follow-up on a cross-sectional study that yielded no social class differences on the Cattell Infant Intelligence Scale for 12-, 18-, and 24-month-old black children. In the present study, 89 children…

  8. Optical tailoring of xFEL beams

    SciTech Connect

    West, Gavin; Coffee, R.

    2015-08-20

    There is an inherent exibility unique to free electron lasers (FELs) that lends well to experimental approaches normally too difficult for other light sources to accomplish. This includes the ability to optically shape the electron bunch prior to final its acceleration for the final FEL process. Optical pulse shaping of the electron bunch can enable both femtosecond and attosecond level FEL pulse control. Pulse shaping is currently implemented, not optically but mechanically, in LCLS-I with an adjustable foil slit that physically spoils the momentum phase of the electron bunch. This selectively suppresses the downstream FEL process ofspoiled electrons. Such a mechanical spoiling method fails for both the soft x-ray regime as well as the high repetition rates that are planned in LCLS-II. Our proposed optical spoiling method circumvents this limitation by making use of the existing ultrafast laser beam that is typically used for adjusting the energy spread for the initial electron bunch. Using Fourier domain shaping we can nearly arbitrarily shape the laser pulses to affect the electron bunch. This can selectively spoil electrons within each bunch. Here we demonstrate the viability of this approach with a programmable acousto-optic dispersive filter. This method is not only well suited for LCLS-II but also has several advantages over mechanical spoiling, including lack of radiation concerns, experiment specific FEL pulse shapes, and real-time adjustment for applications that require high duty-cycle variation such as lock-in amplification of small signals.

  9. Wakefield computations for a corrugated pipe as a beam dechirper for FEL applications

    SciTech Connect

    Ng, C. K.; Bane, K. L.F.

    2015-06-09

    A beam “dechirper” based on a corrugated, metallic vacuum chamber has been proposed recently to cancel residual energy chirp in a beam before it enters the undulator in a linac-based X-ray FEL. Rather than the round geometry that was originally proposed, we consider a pipe composed of two parallel plates with corrugations. The advantage is that the strength of the wake effect can be tuned by adjusting the separation of the plates. The separation of the plates is on the order of millimeters, and the corrugations are fractions of a millimeter in size. The dechirper needs to be meters long in order to provide sufficient longitudinal wakefield to cancel the beam chirp. Considerable computation resources are required to determine accurately the wakefield for such a long structure with small corrugation gaps. Combining the moving window technique and parallel computing using multiple processors, the time domain module in the parallel finite-element electromagnetic suite ACE3P allows efficient determination of the wakefield through convergence studies. In this paper, we will calculate the longitudinal, dipole and quadrupole wakefields for the dechirper and compare the results with those of analytical and field matching approaches.

  10. [Longitudinal studies in the prevention of cardiovascular diseases].

    PubMed

    Balaguer Vintró, Ignacio

    2004-01-01

    Longitudinal studies of well defined cohorts have contributed to the identification of risk factors of coronary heart disease and other clinical complications of atherosclerosis. After commenting on the conclusions of experimental atherosclerosis and risk factors suggested by the study of a series of myocardial infarction in young adults and their matched controls, we discuss the methodology, management and results of longitudinal studies carried out in the United States since 1949: Twin Cities, Framingham, Pooling Project, Western Collaborative, Puerto Rico Evans County, NI-IION-SAN, San Francisco, Harvard, Bogalusa and CARDIA. Special attention is given to the hypothesis proposed at the beginning of the Framingham Study and the obstacles and changes to continue the project after the first twenty-four years. We also expose the Seven Countries Study, designed and managed by Ancel Keys, as the first study performed with centralized methodology in various countries, and the studies in various European countries: Whitehall, Manresa, Paris, British Regional, Northwick Park, Caerphilly, Speedwell and PROCAM. We analyse the role of the longitudinal studies in the methodology of later studies: sons and daughters of the Framingham participants, longitudinal studies based on questionnaires, studies of the other risk factors, prevalence of risk factors in retrospective studies, trials of primary prevention (MRFIT, WHO European Collaborative Trial and Gotenburg Study) and the participation of the trained teams in the MONICA Project. We present the issues still under debate in connection with the methodology and results of the longitudinal studies: problems in the periodic examination of the participants in the epidemiologic studies, changes in definition of the new cases of acute cardiovascular events, use and selection of risk functions based on coronary charts to calculate the individual risk and cardiovascular risk factors as yet unknown.

  11. A Longitudinal Study of Retirement in Older Male Veterans

    ERIC Educational Resources Information Center

    Schnurr, Paula P.; Lunney, Carole A.; Sengupta, Anjana; Spiro, Avron

    2005-01-01

    In this study, the authors examined the effect of retirement on psychological and physical symptoms in 404 older male veterans who were taking part in an ongoing longitudinal study. Hierarchical linear modeling was used to analyze symptom trajectories from preretirement, peri-retirement, and postretirement periods in veterans with either lifetime…

  12. Longitudinal Study of Low and High Achievers in Early Mathematics

    ERIC Educational Resources Information Center

    Navarro, Jose I.; Aguilar, Manuel; Marchena, Esperanza; Ruiz, Gonzalo; Menacho, Inmaculada; Van Luit, Johannes E. H.

    2012-01-01

    Background: Longitudinal studies allow us to identify, which specific maths skills are weak in young children, and whether there is a continuing weakness in these areas throughout their school years. Aims: This 2-year study investigated whether certain socio-demographic variables affect early mathematical competency in children aged 5-7 years.…

  13. A Longitudinal Study of Judge Leniency and Consistency.

    ERIC Educational Resources Information Center

    Lunz, Mary E.; O'Neill, Thomas R.

    This retrospective longitudinal study was designed to show grading leniency patterns of judges within and across clinical examination administrations. Data from 17 different administrations of the histology examination of the American Society of Clinical Pathologists over 10 years were studied. Over the 10 years there were 4,683 candidates and 57…

  14. The Myers Longitudinal Medical Study. Monograph II. Final Report.

    ERIC Educational Resources Information Center

    McCaulley, Mary H.

    The Myers Longitudinal Medical Study is a five-stage investigation of the application of C.G. Jung's theory of psychological types to the understanding of medical student selection, achievement, and choices of specialty, professional employment and location of practice. Part I of this report describes the design and variables of the study, the…

  15. Suprasegmental Phonology Development and Reading Acquisition: A Longitudinal Study

    ERIC Educational Resources Information Center

    Calet, Nuria; Gutiérrez-Palma, Nicolás; Simpson, Ian C.; González-Trujillo, M. Carmen; Defior, Sylvia

    2015-01-01

    Previous studies implicate suprasegmental phonology in reading acquisition. However, little is known about how suprasegmental sensitivity develops or how it contributes to reading. Here, 130 Spanish primary-school children participated in this 2-year longitudinal study. Nonlinguistic rhythm, lexical-stress sensitivity and metrical-stress…

  16. Investigating Sexual Abuse: Findings of a 15-Year Longitudinal Study

    ERIC Educational Resources Information Center

    McCormack, Bob; Kavanagh, Denise; Caffrey, Shay; Power, Anne

    2005-01-01

    Background: There is a lack of longitudinal large-scale studies of sexual abuse in intellectual disability services. Such studies offer opportunities to examine patterns in disclosure, investigation and outcomes, and to report on incidence and trends. Methods: All allegations of sexual abuse (n = 250) involving service users as victims or…

  17. Suprasegmental Phonology Development and Reading Acquisition: A Longitudinal Study

    ERIC Educational Resources Information Center

    Calet, Nuria; Gutiérrez-Palma, Nicolás; Simpson, Ian C.; González-Trujillo, M. Carmen; Defior, Sylvia

    2015-01-01

    Previous studies implicate suprasegmental phonology in reading acquisition. However, little is known about how suprasegmental sensitivity develops or how it contributes to reading. Here, 130 Spanish primary-school children participated in this 2-year longitudinal study. Nonlinguistic rhythm, lexical-stress sensitivity and metrical-stress…

  18. A Longitudinal Case Study of Curriculum Genres, K-3

    ERIC Educational Resources Information Center

    Chapman, Marilyn

    2002-01-01

    I have presented the findings from a longitudinal case study of one child's writing from kindergarten to grade 3, across different curriculum contexts, with a focus on writing in mathematics, social studies, science, and music. I describe changes in textual features of the child's writing over time, which support Newkirk's (1987) developmental…

  19. Longitudinal Study of Low and High Achievers in Early Mathematics

    ERIC Educational Resources Information Center

    Navarro, Jose I.; Aguilar, Manuel; Marchena, Esperanza; Ruiz, Gonzalo; Menacho, Inmaculada; Van Luit, Johannes E. H.

    2012-01-01

    Background: Longitudinal studies allow us to identify, which specific maths skills are weak in young children, and whether there is a continuing weakness in these areas throughout their school years. Aims: This 2-year study investigated whether certain socio-demographic variables affect early mathematical competency in children aged 5-7 years.…

  20. Giftedness, Trauma, and Development: A Qualitative, Longitudinal Case Study

    ERIC Educational Resources Information Center

    Peterson, Jean Sunde

    2014-01-01

    A qualitative, longitudinal, phenomenological case study explored how a gifted female experienced various life events and aspects of development during adolescence and young adulthood (ages 15-30 years), particularly as related to multiple traumatic experiences, which were revealed late in the first year of the study. Additional experiences, well…

  1. Career Trajectories of Dutch Pop Musicians: A Longitudinal Study

    ERIC Educational Resources Information Center

    Zwaan, Koos; ter Bogt, Tom F. M.; Raaijmakers, Quinten

    2010-01-01

    Systematic studies of artistic careers are scarce and this is the first large-scale study on the career development of pop musicians. Using a prospective longitudinal approach we followed a sample of aspiring pop musicians in the Netherlands (N=369) over a three-year period. First we identified four groups of pop musicians with different career…

  2. Homeschooling Education: Longitudinal Study of Methods, Materials, and Curricula

    ERIC Educational Resources Information Center

    Hanna, Linda G.

    2012-01-01

    In a comprehensive study of two-hundred fifty homeschooling families in urban, rural and suburban areas of the Commonwealth of Pennsylvania, the researcher examined all aspects of the instruction, materials and curricula employed by the families in a ten-year longitudinal study from 1998 through 2008. The researcher conducted interviews and…

  3. English as a Foreign Language Spelling Development: A Longitudinal Study

    ERIC Educational Resources Information Center

    Kahn-Horwitz, Janina; Sparks, Richard L.; Goldstein, Zahava

    2012-01-01

    English as a foreign language (EFL) spelling was examined longitudinally three times (4th, 9th, 12th grades) during 9 years of EFL study among Hebrew first language (L1) students. The study examined the impact of L1 literacy variables including phonemic awareness, word attack, and spelling on EFL spelling and the relationship between EFL literacy…

  4. A Longitudinal Study of School Districts' Sustained Improvement

    ERIC Educational Resources Information Center

    Sampson, Pauline M.

    2011-01-01

    In this longitudinal study of one region in the state of Texas, there was an examination of district leadership and the sustaining of high student achievement for their districts. The results of this study suggest that sustained improvement of student achievement is very difficult. The districts that had sustained improvement had stable district…

  5. English as a Foreign Language Spelling Development: A Longitudinal Study

    ERIC Educational Resources Information Center

    Kahn-Horwitz, Janina; Sparks, Richard L.; Goldstein, Zahava

    2012-01-01

    English as a foreign language (EFL) spelling was examined longitudinally three times (4th, 9th, 12th grades) during 9 years of EFL study among Hebrew first language (L1) students. The study examined the impact of L1 literacy variables including phonemic awareness, word attack, and spelling on EFL spelling and the relationship between EFL literacy…

  6. Giftedness, Trauma, and Development: A Qualitative, Longitudinal Case Study

    ERIC Educational Resources Information Center

    Peterson, Jean Sunde

    2014-01-01

    A qualitative, longitudinal, phenomenological case study explored how a gifted female experienced various life events and aspects of development during adolescence and young adulthood (ages 15-30 years), particularly as related to multiple traumatic experiences, which were revealed late in the first year of the study. Additional experiences, well…

  7. Investigating Sexual Abuse: Findings of a 15-Year Longitudinal Study

    ERIC Educational Resources Information Center

    McCormack, Bob; Kavanagh, Denise; Caffrey, Shay; Power, Anne

    2005-01-01

    Background: There is a lack of longitudinal large-scale studies of sexual abuse in intellectual disability services. Such studies offer opportunities to examine patterns in disclosure, investigation and outcomes, and to report on incidence and trends. Methods: All allegations of sexual abuse (n = 250) involving service users as victims or…

  8. Theoretical study of transverse-longitudinal emittance coupling

    SciTech Connect

    Qin, H; Davidson, R C; Chung, M; Barnard, J J; Wang, T F

    2011-04-14

    The effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions is investigated using the generalized Courant-Snyder theory for coupled lattices. Recently, the concept and technique of transverse-longitudinal emittance coupling have been proposed for applications in the Linac Coherent Light Source and other free-electron lasers to reduce the transverse emittance of the electron beam. Such techniques can also be applied to the driver beams for the heavy ion fusion and beam-driven high energy density physics, where the transverse emittance budget is typically tighter than the longitudinal emittance. The proposed methods consist of one or several coupling components which completely swap the emittances of one of the transverse directions and the longitudinal direction at the exit of the coupling components. The complete emittance exchange is realized in one pass through the coupling components. In the present study, we investigate the effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions. A weak coupling component is introduced at every focusing lattice, and we would like to determine if such a lattice can realize the function of emittance exchange.

  9. An induction linac developed for FEL application

    NASA Astrophysics Data System (ADS)

    de Mascureau, J.; Anthouard, Ph.; Bardy, J.; Eyharts, Ph.; Eyl, P.; Launspach, J.; Thevenot, M.; Villate, D.

    1992-07-01

    An induction linac is being studied and built at CESTA for FEL application. At first we studied the induction technology and namely the high-voltage (HV) generators and the induction cells. A HV generator designed to feed the cells with calibrated pulses (150 kV, 50 ns, δV/V < 1%) has been built using a resonant charging system and magnetic switches. This generator is planned for kHz repetition-rate operation. A prototype induction cell has also been built and tested with a cable generator. An electron injector (1.5 MeV, 1.5kA) has been designed and is now under test: it uses ten induction cells and a thermionic dispenser cathode. Numerical codes have been developed and simulations have been compared with experimental results for HV generators, induction cells, and the injector. An induction accelerating module has been studied and we plan to have the accelerator working at 3 MeV in 1992.

  10. Use of Multipass Recirculation and Energy Recovery In CW SRF X-FEL Driver Accelerators

    SciTech Connect

    Douglas, David; Akers, Walt; Benson, Stephen V.; Biallas, George; Blackburn, Keith; Boyce, James; Bullard, Donald; Coleman, James; Dickover, Cody; Ellingsworth, Forrest; Evtushenko, Pavel; Fisk, Sally; Gould, Christopher; Gubeli, Joseph; Hannon, Fay; Hardy, David; Hernandez-Garcia, Carlos; Jordan, Kevin; Klopf, John; Kortze, J.; Legg, Robert; Li, Rui; Marchlik, Matthew; Moore, Steven W.; Neil, George; Powers, Thomas; Sexton, Daniel; Shin, Ilkyoung; Shinn, Michelle D.; Tennant, Christopher; Terzic, Balsa; Walker, Richard; Williams, Gwyn P.; Wilson, G.; Zhang, Shukui

    2010-08-01

    We discuss the use of multipass recirculation and energy recovery in CW SRF drivers for short wavelength FELs. Benefits include cost management (through reduced system footprint, required RF and SRF hardware, and associated infrastructure - including high power beam dumps and cryogenic systems), ease in radiation control (low drive beam exhaust energy), ability to accelerate and deliver multiple beams of differing energy to multiple FELs, and opportunity for seamless integration of multistage bunch length compression into the longitudinal matching scenario. Issues include all those associated with ERLs compounded by the challenge of generating and preserving the CW electron drive beam brightness required by short wavelength FELs. We thus consider the impact of space charge, BBU and other environmental wakes and impedances, ISR and CSR, potential for microbunching, intra-beam and beam-residual gas scattering, ion effects, RF transients, and halo, as well as the effect of traditional design, fabrication, installation and operational errors (lattice aberrations, alignment, powering, field quality). Context for the discussion is provided by JLAMP, the proposed VUV/X-ray upgrade to the existing Jefferson Lab FEL.

  11. Oscillator Seeding of a High Gain Harmonic Generation FEL in a Radiator-First Configuration

    SciTech Connect

    Gandhi, P.; Wurtele, J.; Penn, G.; Reinsch, M.

    2012-05-20

    A longitudinally coherent X-ray pulse from a high repetition rate free electron laser (FEL) is desired for a wide variety of experimental applications. However, generating such a pulse with a repetition rate greater than 1 MHz is a significant challenge. The desired high repetition rate sources, primarily high harmonic generation with intense lasers in gases or plasmas, do not exist now, and, for the multi-MHz bunch trains that superconducting accelerators can potentially produce, are likely not feasible with current technology. In this paper, we propose to place an oscillator downstream of a radiator. The oscillator generates radiation that is used as a seed for a high gain harmonic generation (HGHG) FEL which is upstream of the oscillator. For the first few pulses the oscillator builds up power and, until power is built up, the radiator has no HGHG seed. As power in the oscillator saturates, the HGHG is seeded and power is produced. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft X-ray FEL.

  12. Photon Beam Diagnostics for VISA FEL

    SciTech Connect

    Murokh, A.; Pellegrini, C.; Rosenzweig, J.; Frigola, P.; Musumeci, P.; Tremaine, A.; Babzien, M.; Ben-Zvi, I.; Doyuran, A.; Johnson, E.; Skaritka, J.; Wang, X.J.; Van Bibber, K.; Hill, J.M.; LeSage, G.P.; Nguyen, D.; Cornacchia, M.

    1999-11-05

    The VISA (Visible to Infrared SASE Amplifier) project is designed to be a SASE-FEL driven to saturation in the sub-micron wavelength region. Its goal is to test various aspects of the existing theory of Self-Amplified Spontaneous Emission, as well as numerical codes. Measurements include: angular and spectral distribution of the FEL light at the exit and inside of the undulator; electron beam micro-bunching using CTR; single-shot time resolved measurements of the pulse profile, using auto-correlation technique and FROG algorithm. The diagnostics are designed to provide maximum information on the physics of the SASE-FEL process, to ensure a close comparison of the experimental results with theory and simulations.

  13. The Jefferson Lab 1 KW IR FEL

    SciTech Connect

    D. Douglas for the Jefferson Lab IR Demo FEL Team

    2000-08-01

    The Jefferson Lab (JLab) IR Demo Free Electron Laser (FEL) has completed commissioning and is initiating user service. The FEL - a high repetition rate, low extraction efficiency wiggler-driven optical cavity resonator - produces over 1 kW of tuneable light on intervals in a 3-6 lim wavelength range. It is driven by a 35-48 MeV, 5 mA superconducting RF (SRF) based energy-recovering continuous wave (CW) electron linac. The driver accelerator meets requirements imposed by low energy, high current, and a demand for stringent beam control at the wiggler and during energy recovery. These constraints are driven by the need for six-dimensional phase space management, the existence of deleterious collective phenomena (space charge, wake-fields, beam break-up, and coherent synchrotron radiation), and interactions between the FEL and the accelerator RF. The authors detail the system design, relate commissioning highlights, and discuss present performance.

  14. The APS SASE FEL : modeling and code comparison.

    SciTech Connect

    Biedron, S. G.

    1999-04-20

    A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.

  15. A Longitudinal Study of Idiom and Text Comprehension

    ERIC Educational Resources Information Center

    Levorato, M. Chiara; Roch, Maja; Nesi, Barbara

    2007-01-01

    The relation between text and idiom comprehension in children with poor text comprehension skills was investigated longitudinally. In the first phase of the study, six-year-old first graders with different levels of text comprehension were compared in an idiom and sentence comprehension task. Text comprehension was shown to be more closely related…

  16. A Longitudinal Study of Relational and Physical Aggression in Preschool

    ERIC Educational Resources Information Center

    Crick, Nicki R.; Ostrov, Jamie M.; Burr, Jean E.; Cullerton-Sen, Crystal; Jansen-Yeh, Elizabeth; Ralston, Peter

    2006-01-01

    To understand the development of relational aggression during early childhood, 91 girls and boys ("M" age=39.0; "SD"=7.6 months) and their teachers participated in an 18-month longitudinal study. Children were observed for relational and physical aggression during free play in four time periods. Individually administered interviews were conducted…

  17. Criminal Victimization and Crime Risk Perception: A Multilevel Longitudinal Study

    ERIC Educational Resources Information Center

    Russo, Silvia; Roccato, Michele; Vieno, Alessio

    2013-01-01

    In a national sample of the Italian population, surveyed four times between October 2002 and January 2007 (N = 2,008), we performed a multilevel longitudinal study aimed at predicting the increase in crime risk perception as a function of three families of independent variables, respectively lying at the within individual level (direct…

  18. Minor Delinquency and Immigration: A Longitudinal Study among Male Adolescents

    ERIC Educational Resources Information Center

    Titzmann, Peter F.; Silbereisen, Rainer K.; Mesch, Gustavo

    2014-01-01

    On the basis of general theories of delinquency and the specific situation of immigrants, this longitudinal study investigated predictors of initial levels and rates of change in delinquency among 188 male ethnic German Diaspora immigrants from the former Soviet Union (FSU) in Germany, 237 male native German adolescents, and 182 male Jewish…

  19. Secondary Analysis of National Longitudinal Transition Study 2 Data

    ERIC Educational Resources Information Center

    Hicks, Tyler A.; Knollman, Greg A.

    2015-01-01

    This review examines published secondary analyses of National Longitudinal Transition Study 2 (NLTS2) data, with a primary focus upon statistical objectives, paradigms, inferences, and methods. Its primary purpose was to determine which statistical techniques have been common in secondary analyses of NLTS2 data. The review begins with an…

  20. Attachment from Infancy to Adulthood: The Major Longitudinal Studies

    ERIC Educational Resources Information Center

    Grossmann, Klaus E., Ed.; Grossmann, Karin, Ed.; Waters, Everett, Ed.

    2005-01-01

    This volume provides unique and valuable firsthand accounts of the most important longitudinal studies of attachment. Presented are a range of research programs that have broadened the understanding of early close relationships and their role in individual adaptation throughout life. In addition to discussing the findings that emerged from each…

  1. From ICT Coordination to ICT Integration: A Longitudinal Case Study

    ERIC Educational Resources Information Center

    Tondeur, J.; Cooper, M.; Newhouse, C. P.

    2010-01-01

    This study utilizes a school-improvement perspective to examine the role of curriculum coordination in the integration of information and communication technologies (ICT) into primary schools. The nature and impact of this role is examined in seven primary schools in Australia. These seven schools were drawn from a longitudinal intervention that…

  2. Violence Viewing and Adolescent Aggression: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Viemero, Vappu

    A longitudinal field study conducted in Turku, Finland, traced the development of aggression as a function of the viewing of violence by children from the ages of 7 and 9 to the ages of 15 and 17 to explore the connection between violence viewing and viewers' aggression, and to shed light on the question of causality. The 220 subjects, both male…

  3. Language Acquisition after Mutism: A Longitudinal Case Study of Autism.

    ERIC Educational Resources Information Center

    Windsor, Jennifer; And Others

    1994-01-01

    This longitudinal case study follows the development of a woman with autism from mutism at age 10 to acquisition of a range of spoken and written language skills by age 26. Results support hypotheses that both spoken and written language may become feasible forms of communication in such cases, although some skills may plateau or decline.…

  4. Anxiety Sensitivity and Panic Attacks: A 1-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Li, Wen; Zinbarg, Richard E.

    2007-01-01

    The hypothesis that anxiety sensitivity (AS) is a risk factor for panic genesis has obtained compelling support, but the clinical/practical importance of AS in panic genesis has been questioned. In addition, the association between panic experience and AS increase has not been clearly demonstrated. Through this 1-year longitudinal study among…

  5. A Longitudinal Study Assessing the Microsoft Office Skills Course

    ERIC Educational Resources Information Center

    Carpenter, Donald A.; McGinnis, Denise; Slauson, Gayla Jo; Snyder, Johnny

    2013-01-01

    This paper explains a four-year longitudinal study of the assessment process for a Microsoft Office skills course. It examines whether there is an increase in students' knowledge based on responses to pre- and post-surveys that asked students to evaluate how well they can do particular tasks. Classical classroom teaching methods were used in the…

  6. A Longitudinal Study of the Impact of an Environmental Action

    ERIC Educational Resources Information Center

    Rioux, Liliane; Pasquier, Daniel

    2013-01-01

    In a previous study, we investigated the impact of an awareness-raising campaign on the behaviour of secondary school children in the Centre Region of France, regarding the recycling of used batteries. But, was it a question of pro-environmental behaviour or simply an environmental action? To answer this question, a three-year longitudinal study…

  7. A Longitudinal Study of the Impact of an Environmental Action

    ERIC Educational Resources Information Center

    Rioux, Liliane; Pasquier, Daniel

    2013-01-01

    In a previous study, we investigated the impact of an awareness-raising campaign on the behaviour of secondary school children in the Centre Region of France, regarding the recycling of used batteries. But, was it a question of pro-environmental behaviour or simply an environmental action? To answer this question, a three-year longitudinal study…

  8. Secondary Analysis of National Longitudinal Transition Study 2 Data

    ERIC Educational Resources Information Center

    Hicks, Tyler A.; Knollman, Greg A.

    2015-01-01

    This review examines published secondary analyses of National Longitudinal Transition Study 2 (NLTS2) data, with a primary focus upon statistical objectives, paradigms, inferences, and methods. Its primary purpose was to determine which statistical techniques have been common in secondary analyses of NLTS2 data. The review begins with an…

  9. Exploring Dynamism in Willingness to Communicate: A Longitudinal Case Study

    ERIC Educational Resources Information Center

    Cao, Yiqian Katherine

    2013-01-01

    This paper examines dynamism in students' situational willingness to communicate (WTC) within a second language classroom. This longitudinal study involved twelve English as a Second Language (ESL) participants who enrolled in an English for Academic Purposes (EAP) programme in New Zealand for five months. Based on data from classroom…

  10. The National Early Intervention Longitudinal Study (NEILS) Design Overview.

    ERIC Educational Resources Information Center

    Hebbeler, Kathleen; Wagner, Mary

    The National Early Intervention Longitudinal Study (NEILS) is being conducted to address some of the most important questions related to the implementation and outcomes of Part C of the Individuals with Disabilities Education Act (IDEA). NEILS is following a nationally representative sample of children from birth to 3 years old and their families…

  11. Attachment from Infancy to Adulthood: The Major Longitudinal Studies

    ERIC Educational Resources Information Center

    Grossmann, Klaus E., Ed.; Grossmann, Karin, Ed.; Waters, Everett, Ed.

    2005-01-01

    This volume provides unique and valuable firsthand accounts of the most important longitudinal studies of attachment. Presented are a range of research programs that have broadened the understanding of early close relationships and their role in individual adaptation throughout life. In addition to discussing the findings that emerged from each…

  12. A Longitudinal Study of the Talent Search Program

    ERIC Educational Resources Information Center

    Brewer, Ernest W.; Landers, Jama McMahan

    2005-01-01

    This longitudinal study examined the impact of participation in the federally funded Talent Search program at The University of Tennessee, Knoxville. The Talent Search program provides career exploration and counseling services to low-income students with the potential to be first-generation college graduates. Postsecondary education enrollment…

  13. Connecticut Participation in the National Educational Longitudinal Study (NELS).

    ERIC Educational Resources Information Center

    Connecticut State Department of Education Research Bulletin, 1990

    1990-01-01

    Statewide information concerning the Connecticut eight-grade public school students who particpated in the National Education Longitudinal Study (NELS) in the spring of 1988 is presented. Over 900 students in 46 schools in 35 school districts, almost evenly divided between males and females, completed cognitive tests and student surveys about…

  14. A Longitudinal Study on Learner Career Advancement in MOOCs

    ERIC Educational Resources Information Center

    Wang, Yuan; Paquette, Luc; Baker, Ryan

    2014-01-01

    In this paper, we present progress towards a longitudinal study of the post-course career advancement of MOOC learners. We present initial results and analysis plans for how to link this to in-course behaviour, towards better understanding the goals of all MOOC learners.

  15. Anxiety Sensitivity and Panic Attacks: A 1-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Li, Wen; Zinbarg, Richard E.

    2007-01-01

    The hypothesis that anxiety sensitivity (AS) is a risk factor for panic genesis has obtained compelling support, but the clinical/practical importance of AS in panic genesis has been questioned. In addition, the association between panic experience and AS increase has not been clearly demonstrated. Through this 1-year longitudinal study among…

  16. A Longitudinal Study on Internship Effectiveness in Vocational Higher Education

    ERIC Educational Resources Information Center

    Wan, Chin-Sheng; Yang, Jen-te; Cheng, Shu-yun; Su, Chiakai

    2013-01-01

    A cooperative education experience (or internship placement) is an essential component of the curricula of vocational higher education. The efficacy of internship placements has become one of the major concerns facing those who develop education curricula. The purpose of this longitudinal study was to explore the relationships among the…

  17. Early Cognitive Profiles of Emergent Readers: A Longitudinal Study

    ERIC Educational Resources Information Center

    Brunswick, Nicola; Martin, G. Neil; Rippon, Georgina

    2012-01-01

    This longitudinal study examined the contribution of phonological awareness, phonological memory, and visuospatial ability to reading development in 142 English-speaking children from the start of kindergarten to the middle of Grade 2. Partial cross-lagged analyses revealed significant relationships between early performance on block design and…

  18. Longitudinal Study on Reciprocity between Personality Traits and Parenting Stress

    ERIC Educational Resources Information Center

    Rantanen, Johanna; Tillemann, Kati; Metsäpelto, Riitta-Leena; Kokko, Katja; Pulkkinen, Lea

    2015-01-01

    Reciprocal associations between the Big Five personality traits and parenting stress--including both parents' feelings of their distress and perception of their incompetence as parents--were studied with 248 participants (49% of which were males). Longitudinal data, collected at ages 33/36, 42 and 50 years, were used. Cross-lagged path analysis…

  19. Body Image Among Adolescent Girls and Boys: A Longitudinal Study

    ERIC Educational Resources Information Center

    Jones, Diane Carlson

    2004-01-01

    This longitudinal study of adolescent girls and boys examined the contributions of social (peer appearance context), psychological (internalized appearance ideals and appearance social comparison), and biological (body mass) factors to the development of body dissatisfaction. Students (165 girls and 139 boys) completed questionnaires when they…

  20. Minor Delinquency and Immigration: A Longitudinal Study among Male Adolescents

    ERIC Educational Resources Information Center

    Titzmann, Peter F.; Silbereisen, Rainer K.; Mesch, Gustavo

    2014-01-01

    On the basis of general theories of delinquency and the specific situation of immigrants, this longitudinal study investigated predictors of initial levels and rates of change in delinquency among 188 male ethnic German Diaspora immigrants from the former Soviet Union (FSU) in Germany, 237 male native German adolescents, and 182 male Jewish…

  1. Criminal Victimization and Crime Risk Perception: A Multilevel Longitudinal Study

    ERIC Educational Resources Information Center

    Russo, Silvia; Roccato, Michele; Vieno, Alessio

    2013-01-01

    In a national sample of the Italian population, surveyed four times between October 2002 and January 2007 (N = 2,008), we performed a multilevel longitudinal study aimed at predicting the increase in crime risk perception as a function of three families of independent variables, respectively lying at the within individual level (direct…

  2. Exploring Dynamism in Willingness to Communicate: A Longitudinal Case Study

    ERIC Educational Resources Information Center

    Cao, Yiqian Katherine

    2013-01-01

    This paper examines dynamism in students' situational willingness to communicate (WTC) within a second language classroom. This longitudinal study involved twelve English as a Second Language (ESL) participants who enrolled in an English for Academic Purposes (EAP) programme in New Zealand for five months. Based on data from classroom…

  3. Longitudinal Study on Reciprocity between Personality Traits and Parenting Stress

    ERIC Educational Resources Information Center

    Rantanen, Johanna; Tillemann, Kati; Metsäpelto, Riitta-Leena; Kokko, Katja; Pulkkinen, Lea

    2015-01-01

    Reciprocal associations between the Big Five personality traits and parenting stress--including both parents' feelings of their distress and perception of their incompetence as parents--were studied with 248 participants (49% of which were males). Longitudinal data, collected at ages 33/36, 42 and 50 years, were used. Cross-lagged path analysis…

  4. Stages of Headship: A Longitudinal Study of the Principalship.

    ERIC Educational Resources Information Center

    Weindling, Dick

    This paper uses socialization theory to re-examine a unique, 10-year longitudinal study of headteachers so as to describe the stages of headship transition. It outlines prior models of leadership succession in both business and schools and produces a stage theory of headship that can be used not only as a research tool, but also as a way to assist…

  5. A Longitudinal Study: Phonological Changes Associated with Pharyngeal Flap Surgery.

    ERIC Educational Resources Information Center

    Letcher, Lisa M.; And Others

    The longitudinal study compared the speech of two children (beginning at age 3) with cleft palate and inadequate velopharyngeal closure in an attempt to identify the patterns of production observed prior to surgery and the course and rate of change in production following surgery. Subjects' speech samples were evaluated prior to pharyngeal flap…

  6. A Longitudinal Study of Pretend Play in Autism

    ERIC Educational Resources Information Center

    Rutherford, M. D.; Young, Gregory S.; Hepburn, Susan; Rogers, Sally J.

    2007-01-01

    This study describes a longitudinal design (following subjects described in Rutherford & Rogers [2003, "Journal of Autism and Developmental Disorder", 33, 289-302]) to test for predictors of pretend play competence in a group of children with autism. We tested the hypothesis that developmental change in pretend play performance can be predicted by…

  7. Longitudinal Field Research Methods for Studying Processes of Organizational Change.

    ERIC Educational Resources Information Center

    Van de Ven, Andrew H.; Huber, George P.

    1990-01-01

    This and the next issue of "Organization Science" contain eight papers that deal with the process of organizational change. The five papers in this issue feature the theory of method and practice of researchers engaged in longitudinal field studies aimed at understanding processes of organizational change. (MLF)

  8. The i/t/a in Lompoc: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Wapner, Irwin

    Five hypotheses were tested in two longitudinal studies involving i/t/a used with primary-grade children in the Lompoc Unified School District of California. Parents were allowed to request i/t/a training, teachers were given instruction in i/t/a, and children received i/t/a training in first grade. Reading sections of the Stanford Achievement…

  9. A Longitudinal Study of Early Adolescent Precursors to Running Away

    ERIC Educational Resources Information Center

    Tyler, Kimberly A.; Bersani, Bianca E.

    2008-01-01

    Although previous research has examined correlates of running away among samples of currently homeless and runaway adolescents, little is known about what factors will predict the likelihood that a housed adolescent with no prior history of running away will leave home. As such, the current study uses the National Longitudinal Survey of Youth to…

  10. Health Benefits of Volunteering in the Wisconsin Longitudinal Study

    ERIC Educational Resources Information Center

    Piliavin, Jane Allyn; Siegl, Erica

    2007-01-01

    We investigate positive effects of volunteering on psychological well-being and self-reported health using all four waves of the Wisconsin Longitudinal Study. Confirming previous research, volunteering was positively related to both outcome variables. Both consistency of volunteering over time and diversity of participation are significantly…

  11. A Longitudinal Study of Early Adolescent Precursors to Running Away

    ERIC Educational Resources Information Center

    Tyler, Kimberly A.; Bersani, Bianca E.

    2008-01-01

    Although previous research has examined correlates of running away among samples of currently homeless and runaway adolescents, little is known about what factors will predict the likelihood that a housed adolescent with no prior history of running away will leave home. As such, the current study uses the National Longitudinal Survey of Youth to…

  12. A Longitudinal Study of ESL Learners' Fluency and Comprehensibility Development

    ERIC Educational Resources Information Center

    Derwing, Tracey M.; Munro, Murray J.; Thomson, Ron I.

    2008-01-01

    This longitudinal mixed-methods study compared the oral fluency of well-educated adult immigrants from Mandarin and Slavic language backgrounds (16 per group) enrolled in introductory English as a second language (ESL) classes. Speech samples were collected over a 2-year period, together with estimates of weekly English use. We also conducted…

  13. A Longitudinal Study on Internship Effectiveness in Vocational Higher Education

    ERIC Educational Resources Information Center

    Wan, Chin-Sheng; Yang, Jen-te; Cheng, Shu-yun; Su, Chiakai

    2013-01-01

    A cooperative education experience (or internship placement) is an essential component of the curricula of vocational higher education. The efficacy of internship placements has become one of the major concerns facing those who develop education curricula. The purpose of this longitudinal study was to explore the relationships among the…

  14. Families as Case Managers: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Seltzer, Marsha Mailick; And Others

    1989-01-01

    Performed follow-up study measuring effects of case management training on management activities of families of elderly persons. Interviewed 78 subjects from original study and found case management to be normative activity for families of elderly. Noted differences reported between male and female case managers and in types of obstacles…

  15. A Longitudinal Study of Consumer Socialization.

    ERIC Educational Resources Information Center

    Moschis, George P.; Moore, Roy L.

    A study examined the effects of factors (including television, family, peers, age, and socioeconomic status) on consumer socialization, the process by which individuals develop consumption-related cognitions and behaviors. The specific criterion variables studied included consumer affairs knowledge, puffery filtering, consumer finance management,…

  16. Tourism Degree Internships: A Longitudinal Study

    ERIC Educational Resources Information Center

    Busby, Graham

    2003-01-01

    This case study briefly reviews the development of tourism degrees in the United Kingdom before considering the experiences obtained by students on year-long internship programmes over a period of 8 years. Verbatim confidential comments, from students, are provided and specific transferable skills discussed. Whilst some skills can be developed…

  17. Young Children's Improvisations: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Flohr, John W.

    The purpose of this study was to characterize the behavior of 2-, 3-, 4-, and 5-year-old children engaged in improvisational musical tasks. Ten subjects from each of the four age levels participated in the 4-year investigation, which lasted until the 2-year-olds reached 5 years of age. Children met individually with the investigator for 15 minutes…

  18. Pierce College Longitudinal Study: First Year Report.

    ERIC Educational Resources Information Center

    Sheldon, M. Stephen; Hunter, Russell

    During 1977-78 Pierce College undertook a study to (1) examine major reasons for attrition; (2) determine reasons for student attendance at Pierce; (3) determine the long-range effects of academic residence at Pierce for its students; and (4) experimentally determine the effects on retention of special treatment, through a "caring ombudsman." Each…

  19. Method for Studying Helicopter Longitudinal Maneuver Stability

    NASA Technical Reports Server (NTRS)

    Amer, Kenneth B

    1954-01-01

    A theoretical analysis of helicopter maneuver stability is made and the results are compared with experimental results for both a single and a tandem rotor helicopter. Techniques are described for measuring in flight the significant stability derivatives for use with the theory to aid in design studies of means for achieving marginal maneuver stability for a prototype helicopter.

  20. Generation of a few femtoseconds pulses in seeded FELs using a seed laser with small transverse size

    NASA Astrophysics Data System (ADS)

    Li, Heting; Jia, Qika

    2016-09-01

    We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the center portion of the electron beam and then short pulses at high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse based on the HGHG scheme and 9 nm soft x-ray pulse based on the EEHG scheme with duration of about 8 fs (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 μm. This new scheme can provide an optional operation mode for the existing seeded FEL facilities to meet the requirement of short-pulse FEL.

  1. Accounting for dropout reason in longitudinal studies with nonignorable dropout.

    PubMed

    Moore, Camille M; MaWhinney, Samantha; Forster, Jeri E; Carlson, Nichole E; Allshouse, Amanda; Wang, Xinshuo; Routy, Jean-Pierre; Conway, Brian; Connick, Elizabeth

    2017-08-01

    Dropout is a common problem in longitudinal cohort studies and clinical trials, often raising concerns of nonignorable dropout. Selection, frailty, and mixture models have been proposed to account for potentially nonignorable missingness by relating the longitudinal outcome to time of dropout. In addition, many longitudinal studies encounter multiple types of missing data or reasons for dropout, such as loss to follow-up, disease progression, treatment modifications and death. When clinically distinct dropout reasons are present, it may be preferable to control for both dropout reason and time to gain additional clinical insights. This may be especially interesting when the dropout reason and dropout times differ by the primary exposure variable. We extend a semi-parametric varying-coefficient method for nonignorable dropout to accommodate dropout reason. We apply our method to untreated HIV-infected subjects recruited to the Acute Infection and Early Disease Research Program HIV cohort and compare longitudinal CD4(+) T cell count in injection drug users to nonusers with two dropout reasons: anti-retroviral treatment initiation and loss to follow-up.

  2. A high-power compact regenerative amplifier FEL

    SciTech Connect

    Nguyen, D.C.; Sheffield, R.L.; Fortgang, C.M.; Kinross-Wright, J.M.; Ebrahim, N.A.; Goldstein, J.C.

    1997-08-01

    The Regenerative Amplifier FEL (RAFEL) is a new FEL approach aimed at achieving the highest optical power from a compact rf-linac FEL. The key idea is to feed back a small fraction (< 10%) of the optical power into a high-gain ({approximately}10{sup 5} in single pass) wiggler to enable the FEL to reach saturation in a few passes. This paper summarizes the design of a high-power compact regenerative amplifier FEL and describes the first experimental demonstration of the RAFEL concept.

  3. Some novel features of an FEL oscillator with tapered undulator

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    A one-dimensional analysis of an FEL oscillator with a linear undulator tapering is presented. Some principally novel results have been obtained. The origin of these results is in principal difference between the FEL oscillator and an FEL amplifier. In the case of the FEL amplifier the frequency of the amplified wave and all the other parameters are defined by an experimenter. Contrary to this, the case of the FEL oscillator with tapered undulator is more complicated. The lasing frequency is defined by the maximum of the small-signal gain and depends on the tapering depth in some complex way.

  4. Concepts for NASA longitudinal health studies

    NASA Technical Reports Server (NTRS)

    Nicogossian, A. E.; Pool, S. L.; Leach, C. S.; Moseley, E.; Rambaut, P. C.

    1983-01-01

    Clinical data collected from a 15-year study of the homogenous group of pre-Shuttle astronauts have revealed no significant long-term effects from spaceflight. The current hypothesis suggests that repeated exposures to the space environment in the Shuttle era will similarly have no long-term health effects. However, a much more heterogenous group of astronauts and non-astronaut scientists will fly in Shuttle, and data on this group's adaptation to the space environment and readaptation to earth are currently sparse. In addition, very little information is available concerning the short- and long-term medical consequences of long duration exposure to space and subsequent readaptation to the earth environment. In this paper, retrospective clinical information on astronauts is reviewed and concepts for conducting epidemiological studies examining long-term health effects of spaceflight on humans, including associated occupational risks factors, are presented.

  5. Benchmarking pathology services: implementing a longitudinal study.

    PubMed

    Gordon, M; Holmes, S; McGrath, K; Neil, A

    1999-05-01

    This paper details the benchmarking process and its application to the activities of pathology laboratories participating in a benchmark pilot study [the Royal College of Pathologists of Australasian (RCPA) Benchmarking Project]. The discussion highlights the primary issues confronted in collecting, processing, analysing and comparing benchmark data. The paper outlines the benefits of engaging in a benchmarking exercise and provides a framework which can be applied across a range of public health settings. This information is then applied to a review of the development of the RCPA Benchmarking Project. Consideration is also given to the nature of the preliminary results of the project and the implications of these results to the on-going conduct of the study.

  6. Concepts for NASA longitudinal health studies

    NASA Technical Reports Server (NTRS)

    Nicogossian, A. E.; Pool, S. L.; Leach, C. S.; Moseley, E.; Rambaut, P. C.

    1983-01-01

    Clinical data collected from a 15-year study of the homogenous group of pre-Shuttle astronauts have revealed no significant long-term effects from spaceflight. The current hypothesis suggests that repeated exposures to the space environment in the Shuttle era will similarly have no long-term health effects. However, a much more heterogenous group of astronauts and non-astronaut scientists will fly in Shuttle, and data on this group's adaptation to the space environment and readaptation to earth are currently sparse. In addition, very little information is available concerning the short- and long-term medical consequences of long duration exposure to space and subsequent readaptation to the earth environment. In this paper, retrospective clinical information on astronauts is reviewed and concepts for conducting epidemiological studies examining long-term health effects of spaceflight on humans, including associated occupational risks factors, are presented.

  7. Longitudinal studies of exposure to cadmium.

    PubMed Central

    Armstrong, R; Chettle, D R; Scott, M C; Blindt, M; Mason, H J

    1992-01-01

    Measurements of urinary proteins, blood and urinary cadmium, and in vivo kidney and liver cadmium have been made for a group of workers at several times between 1981 and 1990. The possibility of the introduction of measurement artifacts due to the use of different in vivo measurement systems has been assessed and is considered to be small. Changes in cadmium body burden with time have been studied in relation to kidney function. The results suggest several interesting patterns, although more data are needed to elucidate these further. They do, however, show the effectiveness of good hygiene in the workplace. PMID:1515347

  8. Neuropathologic Studies of the Baltimore Longitudinal Study of Aging (BLSA)

    PubMed Central

    O’Brien, Richard J.; Resnick, Susan M.; Zonderman, Alan B.; Ferrucci, Luigi; Crain, Barbara J.; Pletnikova, Olga; Rudow, Gay; Iacono, Diego; Riudavets, Miguel A.; Driscoll, Ira; Price, Donald L.; Martin, Lee J.; Troncoso, Juan C.

    2010-01-01

    The Baltimore Longitudinal Study of Aging (BLSA) was established in 1958 and is one the oldest prospective studies of aging in the USA and the world. The BLSA is supported by the National Institute of Aging (NIA) and its mission is to learn what happens to people as they get old and how to sort out changes due to aging and from those due to disease or other causes. In 1986, an autopsy program combined with comprehensive neurologic and cognitive evaluations was established in collaboration with the Johns Hopkins University Alzheimer’s Disease Research Center (ADRC). Since then, 211 subjects have undergone autopsy. Here we review the key clinical neuropathological correlations from this autopsy series. The focus is on the morphological and biochemical changes that occur in normal aging, and the early neuropathological changes of neurodegenerative diseases, especially Alzheimer’s disease (AD). We highlight the combined clinical, pathologic, morphometric, and biochemical evidence of asymptomatic AD, a state characterized by normal clinical evaluations in subjects with abundant AD pathology. We conclude that in some individuals, successful cognitive aging results from compensatory mechanisms that occur at the neuronal level (i.e., neuronal hypertrophy and synaptic plasticity) whereas a failure of compensation may culminate in disease. PMID:19661626

  9. A longitudinal study of administrative segregation.

    PubMed

    O'Keefe, Maureen L; Klebe, Kelli J; Metzner, Jeffrey; Dvoskin, Joel; Fellner, Jamie; Stucker, Alysha

    2013-01-01

    The use of administrative segregation for inmates with and without mental illness has generated considerable criticism. Segregated inmates are locked in single cells for 23 hours per day, are subjected to rigorous security procedures, and have restricted access to programs. In this study, we examined whether inmates in segregation would show greater deterioration over time on psychological symptoms than would comparison offenders. The subjects were male inmates, with and without mental illness, in administrative segregation, general population, or special-needs prison. Subjects completed the Brief Symptom Inventory at regular intervals for one year. Results showed differentiation between groups at the outset and statistically significant but small positive change over time across all groups. All groups showed the same change pattern such that there was not the hypothesized differential change of inmates within administrative segregation. This study advances the empirical research, but replication research is needed to make a better determination of whether and under what conditions harm may or may not occur to inmates in solitary confinement.

  10. Plasma HVA in psychiatric patients: longitudinal studies.

    PubMed

    Javaid, J I; Sharma, R P; Janicak, P G; Davis, J M

    1990-01-01

    Plasma homovanillic acid (pHVA) was measured in 40 inpatients (25 schizophrenic and 15 nonschizophrenic patients) who underwent up to 3 weeks of drug washout. Schizophrenic patients were then treated with trifluoperazine for 4 weeks, and weekly behavioral and pHVA measures were obtained. The baseline pHVA had no relationship to age, sex, washout period, diagnosis, or behavioral rating scores. In schizophrenic patients, the baseline pHVA did not differ significantly from any value obtained during 4 weeks of treatment. Although there was significant improvement in clinical symptoms, this was not related to changes in pHVA. Further, changes in any of the four Brief Psychiatric Rating Scale (BPRS) factors (i.e., positive symptoms, negative symptoms, hostility/suspicion, or anxiety/depression) were not correlated with changes in pHVA. Although other studies have reported a positive correlation between pHVA and psychotic symptoms, results of this study suggest that any observed relationship between pHVA and psychosis must be carefully interpreted.

  11. Longitudinal study of alexithymia and multiple sclerosis.

    PubMed

    Chahraoui, Khadija; Duchene, Céline; Rollot, Fabien; Bonin, Bernard; Moreau, Thibault

    2014-01-01

    The aim of this study was to investigate the course of alexithymia and its relation with anxiety and depression in patients with multiple sclerosis (MS), over a period of 5 years. Sixty-two MS patients were examined at two timepoints, 5 years apart, and they answered questionnaires collecting socio-demographic, medical, and psychological data (depression, anxiety, alexithymia). Our data show that emotional disorders remain stable over time in patients with MS, particularly as regards alexithymia and anxiety. Conversely, the rate of depression decreased between the two evaluations, falling from 40% to 26%. The two dimensions of alexithymia (i.e., difficulty describing and difficulty identifying feelings) were correlated with anxiety and depression, whereas the third component of alexithymia (externally oriented thinking) was independent, and was the only component to change over time, with a significant fall observed at 5 years. Alexithymia was associated with increased severity of anxiety and attack relapses.

  12. Ophthalmologic complications of meningomyelocele: a longitudinal study.

    PubMed Central

    Biglan, A W

    1990-01-01

    Patients with spina bifida have multiple ophthalmologic problems, many of which are preventable. Most of the problems are related to the hydrocephalus, which is caused by the coexisting Arnold-Chiari malformation. When patients are treated for hydrocephalus, and comprehensive eye care is available, 94% of the patients will have 6/12 visual acuity or better. Strabismus is common but it responds well to medical and surgical treatment. Children with spina bifida should have frequent examinations by an ophthalmologist who is familiar with the diagnosis and management of the defects recorded in this study. Images FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 PMID:2095031

  13. Evidence for a Fel d I-like molecule in the "big cats" (Felidae species).

    PubMed

    de Groot, H; van Swieten, P; Aalberse, R C

    1990-07-01

    In this study, we investigated the cross-reactivity pattern of IgE and IgG4 antibodies to the major feline allergen, Fel d I. We studied the IgE and IgG4 response of 11 cat-allergic patients against Fel d I-like structures in eight members of the Felidae family: ocelot, puma, serval, siberian tiger, lion, jaguar, snow leopard, and caracal. Hair from these "big cats" was collected, extracted, and used in a RAST system and histamine-release test. By means of a RAST-inhibition assay with affinity-purified Fel d I from cat dander, it was established that, in the Felidae species, a Fel d I equivalent is present that reacts with IgE and IgG4 antibodies. We found that all patients had cross-reacting IgE antibodies to seven of the Felidae tested; no IgE antibodies reactive with the caracal were found. Eight of 10 patients with IgG4 antibodies directed to cat dander also had IgG4 antibodies directed to several Felidae species, including the caracal. However, the correlation between the IgE and the IgG4 antibody specificity was low, indicating that, in the case of Fel d I IgE and IgG4, antibodies do not necessarily have the same specificity.

  14. Longitudinal study of alexithymia and multiple sclerosis

    PubMed Central

    Chahraoui, Khadija; Duchene, Céline; Rollot, Fabien; Bonin, Bernard; Moreau, Thibault

    2014-01-01

    Objective The aim of this study was to investigate the course of alexithymia and its relation with anxiety and depression in patients with multiple sclerosis (MS), over a period of 5 years. Methods Sixty-two MS patients were examined at two timepoints, 5 years apart, and they answered questionnaires collecting socio-demographic, medical, and psychological data (depression, anxiety, alexithymia). Results Our data show that emotional disorders remain stable over time in patients with MS, particularly as regards alexithymia and anxiety. Conversely, the rate of depression decreased between the two evaluations, falling from 40% to 26%. The two dimensions of alexithymia (i.e., difficulty describing and difficulty identifying feelings) were correlated with anxiety and depression, whereas the third component of alexithymia (externally oriented thinking) was independent, and was the only component to change over time, with a significant fall observed at 5 years. Conclusion Alexithymia was associated with increased severity of anxiety and attack relapses. PMID:24653957

  15. A compact FEL upconverter of coherent radiation

    SciTech Connect

    Liu, Y.; Marshall, T.C.

    1995-12-31

    The objective is to generate a powerful millimeter-wave FEL signal in a single pass, using a coherent microwave source (24GHz) to prebunch the electron beam for a harmonically-related wave (72GHz). We use the Columbia FEL facility, operating the electron beam at 600kV, 100A; undulator period = 1.85cm and 250G (K = 0.25); electron beam diameter = 3mm inside a 8.5 mm ID drift tube; guiding field of 8800G. Under these conditions, both the microwave signal (5kW input) and the millimeter signal will show travelling-wave gain in the TE11 mode. We report initial experimental results for the millimeter wave spectrum and find an overall power gain of {approximately}20 for the 24GHz input wave. Also presented will be numerical solutions of the wave growth using the FEL equations with slippage. This device has the advantage of producing a high-power FEL output in a single-pass travelling-wave configuration, obtaining a millimeter wave which is phase-referenced to a coherent laboratory source.

  16. Longitudinal study of intraocular lens exchange.

    PubMed

    Marques, Frederico F; Marques, Daniela M V; Osher, Robert H; Freitas, Lincoln L

    2007-02-01

    To analyze the indications for intraocular lens (IOL) exchange, interval between the first IOL implantation and the exchange, type and mix of IOLs used, effect on vision, and frequency of complications. Cincinnati Eye Institute-Cincinnati-Ohio-USA. This retrospective study comprised 49 eyes of 49 adult patients who had IOL exchange between 1986 and 2002 performed by the same surgeon. The mean age was 70 years old, and 55% were women. The mean interval between surgeries was 53.8 months and the mean follow-up, 35.6 months. The patients were divided into 2 groups according to the type of IOL originally implanted: anterior chamber (AC) or posterior chamber (PC). There were 15 eyes with an AC IOL and 34 eyes with a PC IOL. The difference in mean age and follow-up were not statistically significant between groups. The mean interval between the primary surgery and IOL explantation was 82.3 months in the AC IOL group and 37.9 months in the PC IOL group. The main reason for IOL exchange was inflammation (53.34%) and dislocation/decentration (85.30%), respectively. The preoperative best corrected visual acuity was similar in both groups, and visual acuity was maintained or improved in 80%. Vitreous prolapse was the main intraoperative complication. The primary indication for IOL exchange was intraocular inflammation in patients with an AC IOL and IOL malposition in patients with a PC IOL. The results confirm the safety and positive visual outcome in this complex group of patients.

  17. A review of longitudinal studies on antenatal and postnatal depression.

    PubMed

    Underwood, Lisa; Waldie, Karen; D'Souza, Stephanie; Peterson, Elizabeth R; Morton, Susan

    2016-10-01

    Antenatal depression is a known risk factor for postnatal depression; both are common disorders associated with negative impacts on child development. Few studies have followed up women from pregnancy and through the postnatal period to explore how rates of depression change. This review evaluates recent evidence on depression during pregnancy and after childbirth. A search of Embase, PsychINFO, MEDLINE and Cochrane Reviews was carried out to identify longitudinal studies on antenatal and postnatal depression. Studies that measured depression during pregnancy and up to 1 year after childbirth were evaluated against a set of criteria (e.g. less than 50 % attrition). Of the initial 523 studies identified, 16 studies met the final inclusion criteria with a total of 35,419 women. The average rate of antenatal depression across these studies was 17 and 13 % postnatal depression. The longitudinal nature of the studies revealed that on average 39 % of those who experienced antenatal depression went on to have postnatal depression. Similarly, on average, 47 % of those with postnatal depression had also experienced antenatal depression. On average, almost 7 % of women reported significant depressive symptoms in pregnancy that persisted after childbirth. The review provided evidence that rates of depression tend to be higher during pregnancy than in the first year following childbirth. Furthermore, the longitudinal data show that there is much movement between the groups categorised as depressed or not depressed. There is evidence that postnatal depression is often a continuation of existing antenatal depression.

  18. FEL potential of eRHIC

    SciTech Connect

    Litvinenko, V.N.; Ben-Zvi, I.; Hao, Y.; Kao, C-C.; Kayran, D.; Murphy, J.B.; Ptitsyn, V.; Trbojevic, D.; Tsoupas, N.

    2010-08-23

    Brookhaven National Laboratory plans to build a 5-to-30 GeV energy-recovery linac (ERL) for its future electron-ion collider, eRHIC. In past few months, the Laboratory turned its attention to the potential of this unique machine for free electron lasers (FELS), which we initially assessed earlier. In this paper, we present our current vision of a possible FEL farm, and of narrow-band FEL-oscillators driven by this accelerator. eRHIC, the proposed electron-ion collider at BNL, takes advantage of the existing Relativistic Heavy Ion Collider (RHIC) complex. Plans call for adding a six-pass super-conducting (SRF) ERL to this complex to collide polarized- and unpolarized- electron beams with heavy ions (with energies up to 130 GeV per nucleon) and with polarized protons (with energies up to 325 GeV). RHIC, with a circumference of 3.834 km, has three-fold symmetry and six straight sections each {approx} 250 m long. Two of these straight sections will accommodate 703-MHz SRF linacs. The maximum energy of the electron beam in eRHIC will be reached in stages, from 5 GeV to 30 GeV, by increasing the lengths of its SRF linacs. We plan to install at the start the six-pass magnetic system with small gap magnets. The structure of the eRHIC's electron beam will be identical with that of its hadron beam, viz., 166 bunches will be filled, reserving about a one-microsecond gap for the abort kicker. With modest modifications, we can assure that eRHIC's ERL will become an excellent driver for continuous wave (CW) FELs (see Fig.1). The eRHIC's beam structure will support the operation of several such FELs in parasitic mode.

  19. Predictors of attrition in a longitudinal study of substance abusers.

    PubMed

    Claus, Ronald E; Kindleberger, Lisa R; Dugan, Mary C

    2002-01-01

    Previous research has emphasized the importance of minimizing attrition in longitudinal studies. The authors examined the influence of demographic, clinical, and process factors on attrition from a longitudinal study of 286 substance abusers recruited at a central intake unit. Univariate tests showed that those who completed three, six, and 12 month interviews had higher baseline alcohol and drug use and were more likely to provide three or more contacts when recruited, to be female, to have been married, and to have previously received substance abuse or psychiatric treatment. Multivariate logistic regression revealed that complete data participants (those who completed all three ASI interviews) were nearly three times more likely to have previously received psychiatric treatment and twice as likely to have completed an early engagement interview. In addition, they were twice as likely to be female, and nearly twice as likely to be employed, own a residence, have completed high school, and be married. Procedures that may help decrease study attrition are discussed.

  20. The Seattle Longitudinal Study: Relationship Between Personality and Cognition

    PubMed Central

    Schaie, K. Warner; Willis, Sherry L.; Caskie, Grace I.L.

    2006-01-01

    This article reviews the history, measures and principal findings of the Seattle Longitudinal Study. This study began in 1956 focusing upon age differences and age changes in cognitive abilities. Its sampling frame is a large HMO in the Pacific Northwest. The study has been expanded to investigate various influences on cognitive aging including, cognitive styles, personality traits, life styles, and family environment. Current interest is also in the early detection of risk for dementia. In addition, this article reports original analyses of the relation of personality dimensions to cognitive abilities (both concurrent and longitudinal). While personality remains relatively stable over the adult life span, modest proportions of variance are shared between various personality traits and the cognitive abilities. PMID:16755303

  1. Design Concept for a Compact ERL to Drive a VUV/Soft X-Ray FEL

    SciTech Connect

    Christopher Tennant ,David Douglas

    2011-03-01

    We explore possible upgrades of the existing Jefferson Laboratory IR/UV FEL driver to higher electron beam energy and shorter wavelength through use of multipass recirculation to drive an amplifier FEL. The system would require beam energy at the wiggler of 600 MeV with 1 mA of average current. The system must generate a high brightness beam, configure it appropriately, and preserve beam quality through the acceleration cycle ? including multiple recirculations ? and appropriately manage the phase space during energy recovery. The paper will discuss preliminary design analysis of the longitudinal match, space charge effects in the linac, and recirculator design issues, including the potential for the microbunching instability. A design concept for the low energy recirculator and an emittance preserving lattice solution will be presented.

  2. A longitudinal study of attempted religiously mediated sexual orientation change.

    PubMed

    Jones, Stanton L; Yarhouse, Mark A

    2011-01-01

    The authors conducted a quasi-experimental longitudinal study spanning 6-7 years examining attempted religiously mediated sexual orientation change from homosexual orientation to heterosexual orientation. An initial sample was formed of 72 men and 26 women who were involved in a variety of Christian ministries, with measures of sexual attraction, infatuation and fantasy, and composite measures of sexual orientation and psychological distress, administered longitudinally. Evidence from the study suggested that change of homosexual orientation appears possible for some and that psychological distress did not increase on average as a result of the involvement in the change process. The authors explore methodological limitations circumscribing generalizability of the findings and alternative explanations of the findings, such as sexual identity change or adjustment.

  3. Managing Endings in a Longitudinal Study: Respect for Persons

    NASA Astrophysics Data System (ADS)

    Reiss, Michael J.

    2005-03-01

    In this paper I describe and discuss the way that a book I had written on a five-year longitudinal study of school science teaching was received by the pupils and teachers it featured. By and large the pupils' reception was positive. However, one group of teachers was deeply hurt by the book. I trace this mainly to my failure to consider adequately their fears of the consequences of the book's publication and possibly to my failure to consider with them the psychological significance of my withdrawing from the school after five years of regular study. I hope that there are lessons not only for myself but also for others considering longitudinal and ethnographic research in science education and more broadly.

  4. Indigenous Australians are under-represented in longitudinal ageing studies.

    PubMed

    Anstey, Kaarin J; Kiely, Kim M; Booth, Heather; Birrell, Carole L; Butterworth, Peter; Byles, Julie; Luszcz, Mary A; Gibson, Richard

    2011-08-01

    Evidence-based policy depends on the availability of high-quality research that is relevant to the population. This study aimed to identify the available data on the health of older Indigenous Australians in population-based longitudinal studies of ageing. Evaluation of the Dynamic Analyses to Optimise Ageing Project (DYNOPTA) dataset that has pooled nine Australian longitudinal ageing studies, six of which were analysed here. Proportions of the DYNOPTA sample identified as Indigenous. Indigenous participants made up 0.7% of males and 0.5% of females in the weighted sample, compared with 0.8% of both sexes in the Australian population. Indigenous under-representation is greater at ages 45-54 than at older ages, despite overall greater participation in this age range. Within the existing Australian longitudinal ageing studies, Indigenous Australians are under-represented. This means there is a significant gap in the evidence base relating to the health of older Indigenous Australians. Research approaches specifically designed to address the health and wellbeing of older Indigenous Australians are urgently required. © 2011 The Authors. ANZJPH © 2011 Public Health Association of Australia.

  5. Scientific Applications of a Hard-X-Ray FEL

    NASA Astrophysics Data System (ADS)

    Arthur, John

    1998-04-01

    Free electron lasers are now being designed which will operate at wavelengths down to about 1 angstrom. Due to the physics of the high-gain, single pass FEL process that these sources will exploit, the radiation produced will have unique properties. In particular: -- The FEL peak intensity and peak brightness will be many orders of magnitude higher than can be produced by any other source. -- The pulse length will be less than 1 picosecond, orders of magnitude shorter than can be achieved with any other bright source such as a synchrotron. -- The FEL radiation will have full transverse coherence and a degeneracy parameter (photons/coherence volume) equal to 10^9 or more. No other source can produce hard x-radiation with a degeneracy parameter significantly greater than 1. These properties offer the chance to study chemical, biological, and condensed matter dynamical processes with sub-picosecond time resolution and angstrom spatial resolution. X-ray crystallography could be used to determine the structures of very-short-lived states of photosynthetic reaction centers. X-ray photon correlation spectroscopy could be used to study fluctuations in materials such as gels and glass-forming liquids, on a time scale complementary to that probed by neutron spin echo and dynamic light scattering techniques, but with better spatial resolution. Snap-shot x-ray scattering experiments could be performed on samples in extreme conditions such as ultra-high pulsed magnetic fields. Furthermore, the high peak power of the FEL radiation could be used to create precisely-controlled chemical and structural modifications inside samples. There is also the possibility that nonlinear x-ray interactions could be used to give increased resolution for spectroscopic studies, to greatly expand the parameter space for atomic physics studies, and to permit new fundamental tests of quantum mechanics. For example, the study of nonlinear photon interactions with core atomic electrons would test and

  6. Procedural justice and prisoners' mental health problems: a longitudinal study.

    PubMed

    Beijersbergen, Karin A; Dirkzwager, Anja J E; Eichelsheim, Veroni I; van der Laan, Peter H; Nieuwbeerta, Paul

    2014-04-01

    Given the high prevalence of mental health problems among prisoners, knowledge on its determinants is important. Prior cross-sectional studies suggest that procedurally just treatment within prison is a significant predictor; however, longitudinal research is lacking. The aims of this study were to examine (1) the longitudinal relationship between prisoners' perceptions of procedural justice--including fairness, respect, humanity and relationships with officers--and their mental health and (2) the moderating role of coping style in this relationship. Data were obtained from the Prison Project, a longitudinal study of adult male prisoners in the Netherlands, interviewed both 3 weeks and 3 months after their reception into pre-trial detention (N = 824). A cross-lagged structural equation model was employed to investigate associations. Prisoners who reported experiencing a higher level of procedural justice 3 weeks after their arrival in custody reported fewer mental health problems after 3 months. No evidence was found that coping style moderated this relationship. These findings suggest a causal relationship between procedural justice and psychological well-being. Fair and respectful treatment of prisoners is a predictor not only of prison order and prisoners' compliance but also of prisoners' psychological well-being. Copyright © 2013 John Wiley & Sons, Ltd.

  7. Web-based tracking methods in longitudinal studies.

    PubMed

    Williams, Izaak L; O'Donnell, Clifford R

    2014-08-01

    The use of online resources to reduce the attrition of program participants in longitudinal studies is examined. Higher-risk individuals, those involved in illegal activities, and females with last name changes are typically more difficult to locate. The effectiveness of using online resources for these participants is addressed. These resources include social networking sites, people-finder search engines, telephone and address directories, judicial records, and death records. The strengths and limitations of these resources are presented and discussed. Longitudinal studies using these resources are examined to evaluate their successful follow-up rates. The results of these studies indicate that participant characteristics are more important to successful follow-up than the length of time since participation or sample size. The use of multiple online sites increased follow-up rates, especially for those who are typically difficult to locate. The variables and websites to consider are discussed, and six lessons learned are offered. The prospective use of online participant involvement is especially important for successful longitudinal evaluation and program planning.

  8. Academic dishonesty among Italian nursing students: A longitudinal study.

    PubMed

    Macale, Loreana; Ghezzi, Valerio; Rocco, Gennaro; Fida, Roberta; Vellone, Ercole; Alvaro, Rosaria

    2017-03-01

    Considering the ethical issues related to nursing and that Ethics is an integral part of the nursing education in the degree course, one would suppose that academic dishonesty might be less frequent in nursing students than in students of other disciplines. However, several studies show that this trend of deceitful behaviour seems to be similar among the university nursing students and those of other disciplines. The aim of this study is to investigate the phenomenon of academic dishonesty in the classroom from a longitudinal perspective within a cohort of Italian nursing students. A non-experimental longitudinal design was used. All nursing students were recruited from the Nursing Science Bachelor Degree Program of a big Italian university in the centre of Italy and participants were part of an ongoing longitudinal research project which started in 2011 on nursing students' wellbeing. The results show that students get accustomed to taking academically deceitful actions. They come to consider their behaviours acceptable and normal, thereby stabilizing them, which increases the probability of stabilizing subsequent deceitful behaviours. The stability through time of academic cheating behaviours committed during higher education, within the study's timeframe, provides important perspectives into the establishment of rigorous standards of ethical and moral behaviours by the students.

  9. Enhancement of Permeation in Transdermal Drug Delivery System by 6μm Wavelength Area Using an MIR-FEL

    NASA Astrophysics Data System (ADS)

    Uchizono, T.; Ishii, K.; Iwao, Y.; Itou, Y.; Maruo, H.; Hori, M.; Awazu, K.

    2005-03-01

    Ablation of the stratum corneum (SC) by pulsed-laser irradiation is one method of enhancing transdermal drug delivery (TD). For non-invasive laser TD treatment, we have tried to enhance TD without ablation of the SC using an MIR-FEL (6-μm wavelength) (FEL : free electron laser). Lidocaine was used as the drug in this study. The enhancement of TD was measured by HPLC. It was found that the lidocaine TD of the sample irradiated by MIR-FEL was enhanced 10 fold faster than the non-irradiated sample with a flux at 0.5 μg/cm2/h, measured by HPLC. We have demonstrated the effectiveness of TD enhancement by an MIR-FEL (6-μm wavelength) irradiation.

  10. Cat (Fel d 1) and dog (Can f 1) allergen levels in cars, dwellings and schools.

    PubMed

    Niesler, A; Ścigała, G; Łudzeń-Izbińska, B

    Pets are an important source of indoor allergens. The aim of the study was to compare cat and dog allergen levels in cars, schools and homes. The study was carried out in 17 cars, 14 classrooms and 19 dwellings located in the highly industrialized and urbanized region of Poland. Dust and air samples were analyzed for Fel d 1 and Can f 1 using a double monoclonal ELISA assay. The highest amounts of cat and dog allergens (Fel d 1: 1169 μg/g; Can f 1: 277 μg/g) were found in dwellings with pets. Allergen concentrations were correlated with the number of animals kept at home. Although concentrations on automobile seats were lower, Fel d 1 levels exceeded 8 μg/g in 23.5 % of cars and high levels of Can f 1 (>10 μg/g) were found in 17.6 % of cars. The study revealed that cars of pet owners may be reservoirs of cat and dog allergens even when animals are not transported in them. In schools, concentrations of pet allergens did not reach high levels, but the moderate levels of Fel d 1 (≥1-8 μg/g) and Can f 1 (≥2-10 μg/g) were detected in 42.9 and 7.1 % of the investigated classrooms. Concentrations of cat and dog allergen in schools were higher than in homes without pets. While airborne Fel d 1 and Can f 1 levels were found low, residential allergen concentrations in settled dust and air were correlated. The study results suggest that classrooms and cars of pet owners may be important sites of exposure to cat and dog allergens, though the highest concentrations of Fel d 1 and Can f 1 are found in homes of pet owners.

  11. Towards attosecond X-ray pulses from the FEL

    SciTech Connect

    Zholents, Alexander A.; Fawley, William M.

    2004-07-01

    The ability to study ultrafast phenomena has been recently advanced by the demonstrated production and measurement of a single, 650-attosecond (10{sup 18} sec), VUV x-ray pulse[1] and, latter, a 250-attosecond pulse[2]. The next frontier is a production of the x-ray pulses with shorter wavelengths and in a broader spectral range. Several techniques for a generation of an isolated, attosecond duration, short-wavelength x-ray pulse based upon the ponderomotive laser acceleration [3], SASE and harmonic cascade FELs ([4] - [6]) had been already proposed. In this paper we briefly review a technique proposed in [5] and present some new results.

  12. On a theory of an FEL oscillator with multicomponent undulator

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    Some novel results of a theory of an FEL oscillator with multicomponent undulator are presented. Two popular FEL oscillator configuration are under consideration: optical klystron and FEL oscillator with a prebuncher and tapered main undulator. Using similarity techniques, universal formulae and plots are obtained which allow one to calculate the FEL oscillator lasing conditions an output parameters at saturation. A one-dimensional analysis of an FEL oscillator with a linear undulator tapering is presented. Some principally novel results have been obtained. The origin of these results is in principal difference between the FEL oscillator and an FEL amplifier. In the case of the FEL amplifier the frequency of the amplified wave and all the other parameters are defined by an experimenter. Contrary to this, the case of the FEL oscillator with tapered undulator is more complicated. The lasing frequency is defined by the maximum of the small-signal gain and depends on the tapering depth in some complex way. In particular, at smooth increasing of the tapering depth, the lasing frequency may change by a leap and lasing occurs at another local maximum of the gain curve. This effect influences significantly on the FEL oscillator operation at saturation. As a result, generally accepted method of undulator tapering (for instance, by decreasing undulator field at fixed period) provides an efficiency increase only in a narrow range of the parameters of tapering. We show that in some cases, so called {open_quotes}negative tapering{close_quotes} (for instance, by increasing undulator field at fixed period) has a benefit against traditional tapering method. Ignoring of these basic features of the FEL oscillator with the tapered undulator have led many FEL research groups to nonoptimal design of the FEL experiments and incorrect interpretation of the obtained results.

  13. A photocathode rf gun design for a mm-wave linac-based FEL

    SciTech Connect

    Nassiri, A.; Berenc, T,; Foster, J.; Waldschmidt, G.; Zhou, J.

    1995-07-01

    In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths ({approximately}300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell {pi}-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure.

  14. Longitudinal studies: An essential component for complex psychiatric disorders.

    PubMed

    McInnis, Melvin G; Greden, John F

    2016-01-01

    Most psychiatric syndromes are chronic and lifetime in course. Kraepelin's seminal work pointed out a century ago that longitudinal/lifetime assessments were powerful aids in differentiating dementia praecox from manic-depressive disorder. Despite this, clinical research investigations in psychiatry have historically emphasized short-term and cross-sectional approaches. This review of an array of longitudinal studies supports that they are arguably an essential component of psychiatric investigations, but that they must be coupled with other approaches. The use of standardized, validated, repeated assessments in a disease over the course of time must be incorporated with pathophysiology investigations to identify underlying mechanisms, biomarker studies, comparative effectiveness clinical trials to identify the best treatments for different causes, and translational strategies to provide the right treatments to the right patients at the right time. Strategies for incorporating longitudinal assessments into newer diagnostic proposals, such as the Research Domain Criteria (RDoC), are discussed. Copyright © 2015 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  15. Design and simulation of 3½-cell superconducting gun cavity and beam dynamics studies of the SASE-FEL System at the Institute of Accelerator Technologies at Ankara University

    NASA Astrophysics Data System (ADS)

    Yildiz, H. Duran; Cakir, R.; Porsuk, D.

    2015-06-01

    Design and simulation of a superconducting gun cavity with 3½ cells have been studied in order to give the first push to the electron beam for the linear accelerating system at The Institute of Accelerator Technologies at Ankara University. Electrons are accelerated through the gun cavity with the help of the Radiofrequency power suppliers from cryogenic systems. Accelerating gradient should be as high as possible to accelerate electron beam inside the cavity. In this study, electron beam reaches to 9.17 MeV energy at the end of the gun cavity with the accelerating gradient; Ec=19.21 MV/m. 1.3 GHz gun cavity consists of three TESLA-like shaped cells while the special designed gun-cell includes a cathode plug. Optimized important beam parameters inside the gun cavity, average beam current 3 mA, transverse emittance 2.5 mm mrad, repetition rate 30 MHz and other parameters are obtained for the SASE-FEL System. The Superfish/Poisson program is used to design each cell of the superconducting cavity. Superconducting gun cavity and Radiofrequency properties are studied by utilizing 2D Superfish/Poisson, 3D Computer Simulation Technology Microwave Studio, and 3D Computer Simulation Technology Particle Studio. Superfish/Poisson is also used to optimize the geometry of the cavity cells to get the highest accelerating gradient. The behavior of the particles along the beamline is included in this study. ASTRA Code is used to track the particles.

  16. Wavelength dependent delay in the onset of FEL tissue ablation

    SciTech Connect

    Tribble, J.A.; Edwards, G.S.; Lamb, J.A.

    1995-12-31

    We are investigating the wavelength dependence of the onset of laser tissue ablation in the IR Visible and UV ranges. Toward this end, we have made simultaneous measurements of the ejected material (using a HeNe probe beam tangential to the front surface) and the residual stress transient in the tissue (using traditional piezoelectric detection behind the thin samples). For the IR studies we have used the Vanderbilt FEL and for the UV and Vis range we have used a Q-switched ND:Yag with frequency doubling and quadrupling. To satisfy the conditions of the near field limit for the detection of the stress transient, the duration of the IR FEL macropulse must be as short as possible. We have obtained macropulses as short as 100 ns using Pockels Cell technology. The recording of the signals from both the photodiode monitoring the HeNe probe beam and the acoustic detector are synchronized with the arrival of the 100 ns macropulse. With subablative intensities, the resulting stress transient is bipolar with its positive peak separated from its negative peak by 100 ns in agreement with theory. Of particular interest is the comparison of ablative results using 3 {mu}m and 6.45 {mu}m pulses. Both the stress transient and the ejection of material suffer a greater delay (with respect to the arrival of the 100 ns pulse) when the FEL is tuned to 3 {mu}m as compared to 6.45 {mu}m. A comparison of IR Vis and UV data will be discussed in terms of microscopic mechanisms governing the laser ablation process.

  17. Academic Performance of Language-Minority Students and All-Day Kindergarten: A Longitudinal Study

    ERIC Educational Resources Information Center

    Chang, Mido

    2012-01-01

    This longitudinal study examined the effect of all-day kindergarten programs on the academic achievement of students from racial language minority and low socioeconomic class. The study employed a series of 3-level longitudinal multilevel analyses using a nationally representative database, the Early Childhood Longitudinal Study (ECLS). The study…

  18. 77 FR 20885 - Agency Information Collection (Vocational Rehabilitation and Employment Longitudinal Study Survey...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-06

    .... 2900-New (VR&E Longitudinal Study Survey)'' in any correspondence. For Further Information or a Copy of....mclamb@va.gov . Please refer to ``OMB Control No. 2900-New (VR&E Longitudinal Study Survey... Control Number: 2900-New (VR&E Longitudinal Study Survey). Type of Review: New data collection. Abstract...

  19. Academic Performance of Language-Minority Students and All-Day Kindergarten: A Longitudinal Study

    ERIC Educational Resources Information Center

    Chang, Mido

    2012-01-01

    This longitudinal study examined the effect of all-day kindergarten programs on the academic achievement of students from racial language minority and low socioeconomic class. The study employed a series of 3-level longitudinal multilevel analyses using a nationally representative database, the Early Childhood Longitudinal Study (ECLS). The study…

  20. Gain length dependence on phase shake in the VUV-FEL at the TESLA Test Facility

    SciTech Connect

    Pflueger, J.; Pierini, P.

    1995-12-31

    The TTF VUV FEL, which is in its design stage at DESY, consists of a 30 m long SASE FEL which will radiate around 6 nm, driven by a superconducting linac with final energy of 1 GeV. One of the important issues in its design is the undulator performance, which is studied in this paper. The present setup, including FODO lattice, is discussed in this paper. Results of simulations, including the realistic wiggler field errors and beam stearing, are presented. Dependence of the performance, in particular the gain and saturation length as well as the saturation peak power, on the wiggler field errors is discussed.

  1. Generation of a comb electron beam to drive SASE FEL radiation spikes

    NASA Astrophysics Data System (ADS)

    Boscolo, M.; Boscolo, I.; Castelli, F.; Cialdi, S.; Ferrario, M.; Petrillo, V.; Vaccarezza, C.

    2008-08-01

    A radiofrequency electron gun followed by a compressor can generate trains of subpicosecond electron pulses by illuminating the photocathode with a comb laser pulse. This kind of electron beams can generate trains of single radiation spikes in a SASE-FEL. The dynamics of different electron beam trains traveling in an accelerator is investigated by PARMELA simulations. A set of parameters relative to the SPARC machine are studied with the intent of generating a train of single radiation spikes in a 500 nm SASE-FEL.

  2. An Analysis of Shot Noise Propagation and Amplificationin Harmonic Cascade FELs

    SciTech Connect

    Huang, Z.; /SLAC

    2006-12-11

    The harmonic generation process in a harmonic cascade (HC) FEL is subject to noise degradation which is proportional to the square of the total harmonic order. In this paper, we study the shot noise evolution in the first-stage modulator and radiator of a HC FEL that produces the dominant noise contributions. We derive the effective input noise for a modulator operating in the low-gain regime, and analyze the radiator noise for a density-modulated beam. The significance of these noise sources in different harmonic cascade designs is also discussed.

  3. Preparation, piloting and validation for a longitudinal birth cohort study.

    PubMed

    Golding, Jean

    2009-07-01

    No longitudinal study should go into the field prior to detailed piloting and validation studies of the measures and techniques to be used. Preparation should also involve the training of staff, the acquisition of space and appropriate equipment, and liaison with the community and ethical committees as well as with scientific collaborators. Because different measures will continually be introduced as the participants age, the preparation, piloting and validation studies have to be ongoing. Here we describe some of the different strategies that should be used.

  4. New RF gun for Novosibirsk ERL FEL

    NASA Astrophysics Data System (ADS)

    Volkov, Vladimir N.; Arbusov, Vladimir S.; Kenzhebulatov, Ermek K.; Kolobanov, Evgeniy I.; Kondakov, Aleksey A.; Kozyrev, Evgeniy V.; Krutikhin, Sergey A.; Kurkin, Grigoriy Ya.; Kuptsov, Igor V.; Motygin, Sergey V.; Ovchar, Vladimir K.; Petrov, Victor M.; Pilan, Andrey M.; Rotov, Evgeniy A.; Sedlyarov, Igor K.; Serednykov, Stanislav S.; Shevchenko, Oleg A.; Scheglov, Mikhail A.; Tribendis, Aleksey G.; Vinokurov, Nikolay A.

    The new radiofrequency (RF) gun making an intensive high-quality electron beam for injecting in Novosibirsk microtron recuperator (ERL) and driving Free Electron Laser (FEL) is made in Budker INP SB RAS. Bench tests of RF gun demonstrated good results in strict accordance with the calculations predicting average current of a bunch of 100 iA, energy of particles of 400 keV and normalized emittance less than 15 microns. The RF gun stand testing showed reliable work, unpretentious for vacuum conditions and stable in long-term operation. The additional injection beamline built-in to the existing system of the NovoFEL injector with the static gun is developed and designed.

  5. Duke storage rink UV/VUV FEL: Status and prospects

    SciTech Connect

    Litvinenko, V.N.; Burnham, B.; Madey, J.M.J.

    1995-12-31

    The 1 GeV Duke storage ring was successfully commissioned with parameters exceeding initial specification. The OK-4 FEL has arrived at the Duke FEL laboratory from the Novosibirsk Institute of Nuclear Physics. The OK-4 installation and commissioning is in progress. In this paper we describe the up-to-date status of the Duke storage ring and the OK-4 FEL. The projected performance of the OK-4 UV/VUV FEL is presented based on the electron beam parameters achieved. Initial plans to operate the OK-4 UV/VUV FEL at the Duke 1 GeV storage ring are outlined. Future plans and prospects of both the OK-4 FEL and the Duke storage ring are discussed.

  6. Energy recovery transport design for PKU FEL

    SciTech Connect

    Guimei Wang; Yu-Chiu Chao; KUI Zhao; Xiangyang Lu; Jiejia Zhuang; Chuyu Liu; Zhenchao Liu; Jiaer Chen

    2007-06-25

    A free-electron laser based on superconducting linac is under construction in Peking University(PKU). To increase FEL output power, energy recovery is chosen as one of the most potential and popular way. The design of beam transport system for energy recovery is presented, which is suitable for Peking University construction area. Especially, a chicane structure is chosen to change path length at +/-18 degree and R56 in the arc is adjusted for fully bunch compression.

  7. FEL for the polymer processing industries

    NASA Astrophysics Data System (ADS)

    Kelley, Michael J.

    1997-05-01

    Polymers are everywhere in modern life because of their unique combination of end-use functionalities, ease of processing, recycling potential and modest cost. The physical and economic scope of the infrastructure committed to present polymers makes the introduction of entirely new chemistry unlikely. Rather, the breadth of commercial offerings more likely to shrink in the face of the widening mandate for recycling, especially of packaging. Improved performance and new functionality must therefore come by routes such as surface modification. However they must come with little environmental impact and at painfully low cost. Processing with strongly absorbed light offers unique advantages. The journal and patent literatures disclose a number of examples of benefits that can be achieved, principally by use of excimer lasers or special UV lamps. Examples of commercialization are few, however, because of the unit cost and maximum scale of existing light sources. A FEL, however, offers unique advantages: tunability to the optimum wavelength, potential for scale up to high average power, and a path to attractively low unit cost of light. A business analysis of prospective applications defines the technical and economic requirements a FEL for polymer surface processing must meet. These are compared to FEL technology as it now stands and as it is envisioned.

  8. Study of longitudinal dynamics in space-charge dominated beams

    NASA Astrophysics Data System (ADS)

    Tian, Kai

    Modern accelerator applications, such as heavy ion fusion drivers, pulsed neutron sources, electron injectors for high-energy linear colliders, and X-ray Free Electron Lasers, demand beams with high intensity, low emittance and small energy spread. At low (non-relativistic) energies, the "electrostatic", collective interactions from space-charge forces existing in such intense beams play the dominant role; we characterize these beams as space-charge dominated beams. This dissertation presents numerous new findings on the longitudinal dynamics of a space-charge dominated beam, particularly on the propagation of density perturbations. In order to fully understand the complex physics of longitudinal space-charge waves, we combine the results of theory, computer simulation, and experiment. In the Long Solenoid Experimental system (LSE), with numerous diagnostic tools and techniques, we have, for the first time, experimentally measured the detailed energy profiles of longitudinal space-charge waves at different locations, both near the beam source and at the end of the transport system. Along with the current profiles, we have a complete set of experimental data for the propagation of space-charge waves. We compare these measured results to a 1-D theory and find better agreement for beams with perturbations in the linear regime, where the perturbation strength is less than 10%, than those with nonlinear perturbations. Using fast imaging techniques that we newly developed, we have, for the first time, obtained the progressive time-resolved images of longitudinal slices of a space-charge dominated beam. These images not only provide us time-resolved transverse density distribution of the beam, but also enable us to take time-resolved transverse phase space measurement using computerized tomography. By combining this information with the longitudinal energy measurement, we have, for the first time, experimentally constructed the full 6-D phase space. Part of the results

  9. Integrating Prospective Longitudinal Data: Modeling Personality and Health in the Terman Life Cycle and Hawaii Longitudinal Studies

    ERIC Educational Resources Information Center

    Kern, Margaret L.; Hampson, Sarah E.; Goldberg, Lewis R.; Friedman, Howard S.

    2014-01-01

    The present study used a collaborative framework to integrate 2 long-term prospective studies: the Terman Life Cycle Study and the Hawaii Personality and Health Longitudinal Study. Within a 5-factor personality-trait framework, teacher assessments of child personality were rationally and empirically aligned to establish similar factor structures…

  10. Integrating Prospective Longitudinal Data: Modeling Personality and Health in the Terman Life Cycle and Hawaii Longitudinal Studies

    ERIC Educational Resources Information Center

    Kern, Margaret L.; Hampson, Sarah E.; Goldberg, Lewis R.; Friedman, Howard S.

    2014-01-01

    The present study used a collaborative framework to integrate 2 long-term prospective studies: the Terman Life Cycle Study and the Hawaii Personality and Health Longitudinal Study. Within a 5-factor personality-trait framework, teacher assessments of child personality were rationally and empirically aligned to establish similar factor structures…

  11. Cohort Profile: The English Longitudinal Study of Ageing

    PubMed Central

    Steptoe, Andrew; Breeze, Elizabeth; Banks, James; Nazroo, James

    2013-01-01

    The English Longitudinal Study of Ageing (ELSA) is a panel study of a representative cohort of men and women living in England aged ≥50 years. It was designed as a sister study to the Health and Retirement Study in the USA and is multidisciplinary in orientation, involving the collection of economic, social, psychological, cognitive, health, biological and genetic data. The study commenced in 2002, and the sample has been followed up every 2 years. Data are collected using computer-assisted personal interviews and self-completion questionnaires, with additional nurse visits for the assessment of biomarkers every 4 years. The original sample consisted of 11 391 members ranging in age from 50 to 100 years. ELSA is harmonized with ageing studies in other countries to facilitate international comparisons, and is linked to financial and health registry data. The data set is openly available to researchers and analysts soon after collection (http://www.esds.ac.uk/longitudinal/access/elsa/l5050.asp). PMID:23143611

  12. A 2-D numerical simulation study on longitudinal solute transport and longitudinal dispersion coefficient

    NASA Astrophysics Data System (ADS)

    Zhang, Wei

    2011-07-01

    The longitudinal dispersion coefficient, DL, is a fundamental parameter of longitudinal solute transport models: the advection-dispersion (AD) model and various deadzone models. Since DL cannot be measured directly, and since its calibration using tracer test data is quite expensive and not always available, researchers have developed various methods, theoretical or empirical, for estimating DL by easier available cross-sectional hydraulic measurements (i.e., the transverse velocity profile, etc.). However, for known and unknown reasons, DL cannot be satisfactorily predicted using these theoretical/empirical formulae. Either there is very large prediction error for theoretical methods, or there is a lack of generality for the empirical formulae. Here, numerical experiments using Mike21, a software package that implements one of the most rigorous two-dimensional hydrodynamic and solute transport equations, for longitudinal solute transport in hypothetical streams, are presented. An analysis of the evolution of simulated solute clouds indicates that the two fundamental assumptions in Fischer's longitudinal transport analysis may be not reasonable. The transverse solute concentration distribution, and hence the longitudinal transport appears to be controlled by a dimensionless number ?, where Q is the average volumetric flowrate, Dt is a cross-sectional average transverse dispersion coefficient, and W is channel flow width. A simple empirical ? relationship may be established. Analysis and a revision of Fischer's theoretical formula suggest that ɛ influences the efficiency of transverse mixing and hence has restraining effect on longitudinal spreading. The findings presented here would improve and expand our understanding of longitudinal solute transport in open channel flow.

  13. Strong focusing influence on high gain FEL characteristics

    SciTech Connect

    Smirnov, A.; Varfolomeev, A.

    1995-12-31

    The use of intrinsic alternating focusing in a linac-driven FEL with planar undulator is considered numerically. The analysis is done on the basis of TDA code for soft X-ray FEL with FD lattice implementing focusing of quadrupole and periodic sextupole type. The influence of the focusing (type and phase advance) on FEL performance and the reasons of difference in FEL performance for focusing of two kinds are analyzed. A possibility of some kind of beam conditioning for intrinsic focusing is discussed.

  14. Start-Up of FEL Oscillator from Shot Noise

    SciTech Connect

    Kumar, V.; Krishnagopal, S.; Fawley, W.M.

    2007-01-25

    In free-electron laser (FEL) oscillators, as inself-amplified spontaneous emission (SASE) FELs, the buildup of cavitypower starts from shot noise resulting from the discreteness ofelectronic charge. It is important to do the start-up analysis for thebuild-up of cavity power in order to fix the macropulse width from theelectron accelerator such that the system reaches saturation. In thispaper, we use the time-dependent simulation code GINGER [1]toperformthis analysis. We present results of this analysis for theparameters of the Compact Ultrafast TErahertz FEL (CUTE-FEL) [2]beingbuilt atRRCAT.

  15. Longitudinal space charge amplifier

    NASA Astrophysics Data System (ADS)

    Schneidmiller, E. A.; Yurkov, M. V.

    2013-05-01

    Longitudinal space charge (LSC) driven microbunching instability in electron beam formation systems of X-ray FELs is a recently discovered effect hampering beam instrumentation and FEL operation. The instability was observed in different facilities in infrared and visible wavelength ranges. In this paper we propose to use such an instability for generation of vacuum ultraviolet (VUV) and X-ray radiation. A typical longitudinal space charge amplifier (LSCA) consists of few amplification cascades (drift space plus chicane) with a short undulator behind the last cascade. If the amplifier starts up from the shot noise, the amplified density modulation has a wide band, on the order of unity. The bandwidth of the radiation within the central cone is given by inverse number of undulator periods. A wavelength compression could be an attractive option for LSCA since the process is broadband, and a high compression stability is not required. LSCA can be used as a cheap addition to the existing or planned short-wavelength FELs. In particular, it can produce the second color for a pump-probe experiment. It is also possible to generate attosecond pulses in the VUV and X-ray regimes. Some user experiments can profit from a relatively large bandwidth of the radiation, and this is easy to obtain in LSCA scheme. Finally, since the amplification mechanism is broadband and robust, LSCA can be an interesting alternative to self-amplified spontaneous emission free electron laser (SASE FEL) in the case of using laser-plasma accelerators as drivers of light sources.

  16. Linac Coherent Light Source Longitudinal Feedback Model

    SciTech Connect

    Wu, Juhao; Emma, P.; Hendrickson, L.; /SLAC

    2005-06-15

    The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL). To ensure the vitality of FEL lasing, it is critical to preserve the high quality of the electron beam during acceleration and compression. The peak current and final energy are very sensitive to system jitter. To minimize this sensitivity, a longitudinal feedback system on the bunch length and energy is required, together with other diagnostics and feedback systems (e.g., on transverse phase space). Here, we describe a simulation framework, which includes a realistic jitter model for the LCLS accelerator system, the RF acceleration, structure wakefield, and second order optics. Simulation results show that to meet the tight requirements set by the FEL, such a longitudinal feedback system is mandatory.

  17. Longitudinal study of workers in an aluminum smelter

    SciTech Connect

    Chan-Yeung, M.; Enarson, D.A.; MacLean, L.; Irving, D.

    1989-05-01

    We conducted a 6-y follow-up study that included workers in an aluminum smelter in British Columbia. Of the original cohort, 951 workers left the industry and 985 workers participated in both studies. Comparison of those who left and those who remained showed that those who left were (1) older, (2) had a slightly higher prevalence of respiratory symptoms, and (3) had lower lung function; this was especially true for workers who were 50 + y of age at the time the initial study was conducted. Analyses were conducted only on 586 male workers who did not change their job location or smoking habits between the initial and the follow-up study. Potroom workers in the ''high-exposure'' group had a significant reduction in the prevalence of cough, but experienced an increase in the prevalence of wheeze. There was no significant difference in the annual decline in forced expiratory volume in 1 sec and forced vital capacity between the potroom workers and controls. In general, older workers and smokers had a greater decline in lung function compared to younger workers and nonsmokers. Leukocyte count done during the initial study was found to be an independent predictor of longitudinal decline in lung function. The lack of exposure effect on longitudinal decline in lung function could be due to ''healthy worker'' effect and improvement in the working condition of the smelter.

  18. Serial snapshot crystallography for materials science with SwissFEL

    DOE PAGES

    Dejoie, Catherine; Smeets, Stef; Baerlocher, Christian; ...

    2015-04-21

    New opportunities for studying (sub)microcrystalline materials with small unit cells, both organic and inorganic, will open up when the X-ray free electron laser (XFEL) presently being constructed in Switzerland (SwissFEL) comes online in 2017. Our synchrotron-based experiments mimicking the 4%-energy-bandpass mode of the SwissFEL beam show that it will be possible to record a diffraction pattern of up to 10 randomly oriented crystals in a single snapshot, to index the resulting reflections, and to extract their intensities reliably. The crystals are destroyed with each XFEL pulse, but by combining snapshots from several sets of crystals, a complete set of datamore » can be assembled, and crystal structures of materials that are difficult to analyze otherwise will become accessible. Even with a single shot, at least a partial analysis of the crystal structure will be possible, and with 10–50 femtosecond pulses, this offers tantalizing possibilities for time-resolved studies.« less

  19. Complete Study of Longitudinal Oscillation of a VE-7 Airplane

    NASA Technical Reports Server (NTRS)

    Norton, F H; Brown, W G

    1924-01-01

    This investigation was carried out by the National Advisory Committee for Aeronautics at Langley Field in order to study as closely as possible the behavior of an airplane when it was making a longitudinal oscillation. The airspeed, the altitude, the angle with the horizon and the angle of attack were all recorded simultaneously and the resulting curves plotted to the same time scale. The results show that all the curves are very close to damped sine curves, with the curves for height and angle of attack in phase, that for angle with the horizon leading them by 18 per cent and that for path angle leading them by 25 per cent.

  20. The wage effects of obesity: a longitudinal study.

    PubMed

    Baum, Charles L; Ford, William F

    2004-09-01

    We use National Longitudinal Survey of Youth (NLSY) data to examine the effects of obesity on wages by gender. Sample means indicate that both men and women experience a persistent obesity wage penalty over the first two decades of their careers. We then control for a standard set of socioeconomic and familial variables but find that standard covariates do not explain why obese workers experience persistent wage penalties. This suggests that other variables -- including job discrimination, health-related factors and/or obese workers' behavior patterns -- may be the channels through which obesity adversely affects wages. The study closes with a discussion of the public policy implications suggested by these findings.

  1. Theoretical study of longitudinal beam splitting and related phenomena

    SciTech Connect

    Ellison, J.; Shih, H.J.; Kummer, M.

    1993-10-01

    A recent experiment at the Indiana University Cyclotron Facility (IUCF) with electron cooling showed that rf phase modulation near 1:1 resonance leads to longitudinal beam splitting. Here we explain this by applying the method of averaging, a powerful tool from the study of dynamical systems, to the underlying equation of motion -- a pendulum equation with small damping and periodic forcing. The beam splitting is explained by showing that the associated Poincare map has two attracting fixed points, each with a well-defined basin of attraction. Our approach can be immediately applied to other accelerator physics problems governed by a similar equation.

  2. Theoretical study of longitudinal beam splitting and related phenomena

    SciTech Connect

    Ellison, J.A.; Shih, H. ); Kummer, M. )

    1994-03-01

    A recent experiment at the Indiana University Cyclotron Facility with electron cooling showed that rf phase modulation near the 1:1 resonance leads to longitudinal beam splitting. Here we explain this by applying the method of averaging, a powerful tool from the study of dynamical systems, to the underlying equation of motion---a pendulum equation with small damping and periodic forcing. The beam splitting is explained by showing that the associated Poincare map has two attracting fixed points, each with a well-defined basin of attraction. Our approach can be immediately applied to other accelerator-physics problems governed by a similar equation.

  3. Comparing classification methods for longitudinal fMRI studies.

    PubMed

    Schmah, Tanya; Yourganov, Grigori; Zemel, Richard S; Hinton, Geoffrey E; Small, Steven L; Strother, Stephen C

    2010-11-01

    We compare 10 methods of classifying fMRI volumes by applying them to data from a longitudinal study of stroke recovery: adaptive Fisher's linear and quadratic discriminant; gaussian naive Bayes; support vector machines with linear, quadratic, and radial basis function (RBF) kernels; logistic regression; two novel methods based on pairs of restricted Boltzmann machines (RBM); and K-nearest neighbors. All methods were tested on three binary classification tasks, and their out-of-sample classification accuracies are compared. The relative performance of the methods varies considerably across subjects and classification tasks. The best overall performers were adaptive quadratic discriminant, support vector machines with RBF kernels, and generatively trained pairs of RBMs.

  4. Sleep and the Transition to Adolescence: A Longitudinal Study

    PubMed Central

    Sadeh, Avi; Dahl, Ronald E.; Shahar, Golan; Rosenblat-Stein, Shiran

    2009-01-01

    Study Objectives: To assess the links between sleep and pubertal development using a longitudinal design. Design: Three consecutive annual assessments of sleep and pubertal development. Sleep was assessed using a week of home actigraphy. Setting: Naturalistic sleep in the home setting of school children, Tel Aviv Area, Israel. Participants: A sample of 94 (41 boys) typically developing healthy school-age children (age range at first assessment: 9.9–11.2 years). Intervention: N/A Measurements and Results: The Petersen's Pubertal Development Scale (PDS) and Sexual Maturation Scale (SMS) were used to assess pubertal development, and a week of actigraphy served to assess naturalistic sleep patterns. The results reflect expected developmental trends: an increase in signs of pubertal maturation, delayed sleep onset, and shorter sleep time. After controlling for age, significant relationships were found between sleep onset time, true sleep time, and number of night wakings at Time 1 and pubertal ratings at Time 2, and pubertal changes from Time 1 to Time 2. Delayed and disrupted sleep at Time 1 predicted faster pubertal changes from Time 1 to Time 2. These results were supported by structural equation modeling. These findings were similar in boys and girls. Conclusions: Based on these longitudinal data, it appears that pubertal changes in sleep (delayed sleep phase and disrupted sleep patterns) antedate bodily changes associated with puberty. The underlying mechanisms explaining these predictive links should be further explored. Citation: Sadeh A; Dahl RE; Shahar G; Rosenblat-Stein S. Sleep and the transition to adolescence: a longitudinal study. SLEEP 2009;32(12):1602-1609. PMID:20041596

  5. National Longitudinal Study. Withdrawal from Institutions of Higher Education. An Appraisal with Longitudinal Data Involving Diverse Institutions.

    ERIC Educational Resources Information Center

    Fetters, William B.

    Using data from the National Longitudinal Study of the High School Class of 1972, the National Center for Education Statistics undertook a study of dropouts in higher education. Specifically, the study was designed to discover: (1) to what extent students withdraw from institutions of higher education before completion, and how these rates might…

  6. North American Prodrome Longitudinal Study (NAPLS 2): Overview and Recruitment

    PubMed Central

    Addington, Jean; Cadenhead, Kristin S.; Cornblatt, Barbara A.; Mathalon, Daniel H.; McGlashan, Thomas H.; Perkins, Diana O.; Seidman, Larry J.; Tsuang, Ming T.; Walker, Elaine F.; Woods, Scott W.; Addington, Jack A.; Cannon, Tyrone D.

    2012-01-01

    The North American Prodrome Longitudinal Study (NAPLS) is a consortium of eight programs focusing on the psychosis prodrome. Funded by the National Institute of Mental Health (NIMH), the sites are located at Emory University, Harvard University, University of Calgary, UCLA, UCSD, University of North Carolina Chapel Hill, Yale University, and Zucker Hillside Hospital. Although the programs initially developed independently, they previously collaborated to combine their historical datasets and to produce a series of analyses on predictors of psychosis in one of the largest samples of longitudinally followed prodromal subjects worldwide. This led to the development of a five year prospective study “Predictors and Mechanisms of Conversion to Psychosis”, (also known as NAPLS-2) with three major aims: (1) to prospectively test the prediction algorithm developed in NAPLS-1, (2) to investigate the neuroanatomical, neurophysiological, neurocognitive, and neurohormonal factors that may contribute to the development of psychosis, and (3) to develop a repository of DNA, RNA, and plasma from participants meeting diagnostic criteria for a clinical high risk (CHR) state and from demographically similar healthy subjects. Funded by NIMH in 2008, NAPLS-2 will generate the largest CHR for psychosis sample with 720 CHR and 240 healthy comparison subjects, and thus will provide statistical power and scientific scope that cannot be duplicated by any single site study. This paper describes the overall methodology of the NAPLS-2 project and reports on the ascertainment and demographics at the midway point of the study with (360 CHR) and 180 controls. PMID:23043872

  7. Design of the SRF Driver ERL for the Jefferson Lab UV FEL

    SciTech Connect

    Douglas, David R; Benson, Stephen; Biallas, George; Blackburn, Keith; Boyce, James; Bullard, Donald; Coleman, James; Dickover, Cody; Ellingsworth, Forrest; Evtushenko, Pavel; Gould, Christopher; Gubeli, Joseph; Hannon, Fay; Hardy, David; Hernandez-Garcia, Carlos; Jordan, Kevin; Klopf, Michael; Kortze, James; Marchlik, Matthew; Moore, Steven; Neil, George; Powers, Thomas; Sexton, Daniel; Shinn, Michelle D; Tennant, Christopher; Walker, Richard; Wilson, Frederick; Zhang, Shukui

    2011-03-01

    We describe the design of the SRF Energy-Recovering Linac (ERL) providing the CW electron drive beam at the Jefferson Lab UV FEL. Based on the same 135 MeV linear accelerator as and sharing portions of the recirculator with the Jefferson Lab 10 kW IR Upgrade FEL, the UV driver ERL uses a novel bypass geometry to provide transverse phase space control, bunch length compression, and nonlinear aberration compensation (including correction of RF curvature effects) without the use of magnetic chicanes or harmonic RF. Stringent phase space requirements at the wiggler, low beam energy, high beam current, and use of a pre-existing facility and legacy hardware subject the design to numerous constraints. These are imposed not only by the need for both transverse and longitudinal phase space management, but also by the potential impact of collective phenomena (space charge, wakefields, beam break-up (BBU), and coherent synchrotron radiation (CSR)), and by interactions between the FEL and the accelerator RF system. This report addresses these issues and presents the accelerator design solution that is now in operation.

  8. Leadership in transformation: a longitudinal study in a nursing organization.

    PubMed

    Viitala, Riitta

    2014-01-01

    Not only does leadership produce changes, but those changes produce leadership in organisations. The purpose of this paper is to present a theoretical and empirical analysis of the transformation of leadership at two different historical points in a health care organisation. It leans on the perspective of social constructionism, drawing especially from the ideas of Berger and Luckmann (1966). The paper seeks to improve understanding of how leaders themselves construct leadership in relation to organisational change. The empirical material was gathered in a longitudinal case study in a nursing organisation in two different historical and situational points. It consists of written narratives produced by nurse leaders that are analysed by applying discourse analysis. The empirical study revealed that the constructions of leadership were dramatically different at the two different historical and situational points. Leadership showed up as a complex, fragile and changing phenomenon, which fluctuates along with the other organisational changes. The results signal the importance of agency in leadership and the central role of "significant others". The paper questions the traditional categorisation and labelling of leadership as well as the cross-sectional studies in understanding leadership transformation. Its originality relates to the longitudinal perspective on transformation of leadership in the context of a health care organisation.

  9. Confounding in longitudinal studies in addiction treatment research

    PubMed Central

    Pierce, Matthias; Dunn, Graham; Millar, Tim

    2017-01-01

    Abstract Background: The effectiveness of treatment for people with substance use disorders is usually examined using longitudinal cohorts. In these studies, treatment is often considered as a time-varying exposure. The aim of this commentary is to examine confounding in this context, when the confounding variable is time-invariant and when it is time-varying. Method: Types of confounding are described with examples and illustrated using path diagrams. Simulations are used to demonstrate the direction of confounding bias and the extent that it is accounted for using standard regression adjustment techniques. Results: When the confounding variable is time invariant or time varying and not influenced by prior treatment, then standard adjustment techniques are adequate to control for confounding bias, provided that in the latter scenario the time-varying form of the variable is used. When the confounder is time varying and affected by prior treatment status (i.e. it is a mediator of treatment), then standard methods of adjustment result in inconsistency. Conclusions: In longitudinal cohorts where treatment exposure is time varying, confounding is an issue which should be considered, even if treatment exposure is initially randomized. In these studies, standard methods of adjustment may result be inadequate, even when all confounders have been identified. This occurs when the confounder is also a mediator of treatment. This is a likely scenario in many studies in addiction.

  10. Confounding in longitudinal studies in addiction treatment research.

    PubMed

    Pierce, Matthias; Dunn, Graham; Millar, Tim

    2017-05-04

    Background: The effectiveness of treatment for people with substance use disorders is usually examined using longitudinal cohorts. In these studies, treatment is often considered as a time-varying exposure. The aim of this commentary is to examine confounding in this context, when the confounding variable is time-invariant and when it is time-varying. Method: Types of confounding are described with examples and illustrated using path diagrams. Simulations are used to demonstrate the direction of confounding bias and the extent that it is accounted for using standard regression adjustment techniques. Results: When the confounding variable is time invariant or time varying and not influenced by prior treatment, then standard adjustment techniques are adequate to control for confounding bias, provided that in the latter scenario the time-varying form of the variable is used. When the confounder is time varying and affected by prior treatment status (i.e. it is a mediator of treatment), then standard methods of adjustment result in inconsistency. Conclusions: In longitudinal cohorts where treatment exposure is time varying, confounding is an issue which should be considered, even if treatment exposure is initially randomized. In these studies, standard methods of adjustment may result be inadequate, even when all confounders have been identified. This occurs when the confounder is also a mediator of treatment. This is a likely scenario in many studies in addiction.

  11. Design and methods of the national Vietnam veterans longitudinal study.

    PubMed

    Schlenger, William E; Corry, Nida H; Kulka, Richard A; Williams, Christianna S; Henn-Haase, Clare; Marmar, Charles R

    2015-09-01

    The National Vietnam Veterans Longitudinal Study (NVVLS) is the second assessment of a representative cohort of US veterans who served during the Vietnam War era, either in Vietnam or elsewhere. The cohort was initially surveyed in the National Vietnam Veterans Readjustment Study (NVVRS) from 1984 to 1988 to assess the prevalence, incidence, and effects of post-traumatic stress disorder (PTSD) and other post-war problems. The NVVLS sought to re-interview the cohort to assess the long-term course of PTSD. NVVLS data collection began July 3, 2012 and ended May 17, 2013, comprising three components: a mailed health questionnaire, a telephone health survey interview, and, for a probability sample of theater Veterans, a clinical diagnostic telephone interview administered by licensed psychologists. Excluding decedents, 78.8% completed the questionnaire and/or telephone survey, and 55.0% of selected living veterans participated in the clinical interview. This report provides a description of the NVVLS design and methods. Together, the NVVRS and NVVLS constitute a nationally representative longitudinal study of Vietnam veterans, and extend the NVVRS as a critical resource for scientific and policy analyses for Vietnam veterans, with policy relevance for Iraq and Afghanistan veterans.

  12. A novel self-seeding scheme for hard X-ray FELs

    NASA Astrophysics Data System (ADS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2011-09-01

    Typical SASE XFEL pulses exhibit poor longitudinal coherence, a characteristic inherited from the start-up from shot noise. Self-seeding schemes are an answer to the call for improved longitudinal coherence. If applied to already working or designed XFELs, these schemes are subject to constraints, including minimal change to the baseline design, and possibility to recover the baseline mode of operation. In this work we propose a novel single-bunch self-seeding method, based on a particular kind of monochromator that satisfies these constraints. We will limit ourselves to the analysis of the simplest possible configuration, consisting of an input undulator and an output undulator, separated by our novel monochromatization stage. Such a stage consists of a weak few-meter long chicane, acting as a tunable delay stage, washing out the electron beam microbunching, and creating a transverse offset for the monochromator. In essence, the monochromator consists of a single crystal in Bragg-transmission geometry, which operates as a bandstop filter for the transmitted X-ray SASE radiation pulse. When the incident angle and the spectral contents of the incoming beam satisfy the Bragg diffraction condition, the temporal waveform of the transmitted radiation pulse shows a long monochromatic tail, whose duration is inversely proportional to the bandwidth of the absorption line in the transmittance spectrum. The magnetic chicane is tuned to shift the electron bunch on top of the monochromatic wake created by the bandstop filter thus selecting (temporal windowing) a part of the wake. By this, the electron bunch is seeded with a radiation pulse characterized by a bandwidth much narrower than the natural FEL bandwidth. The output power from our setup can be further increased by tapering the magnetic field of the undulator, yielding a tremendous increase in peak brightness with respect to the baseline mode of operation. In this work we present a feasibility study and exemplifications

  13. Longitudinal associations between objective sleep and lipids: the CARDIA study.

    PubMed

    Petrov, Megan E Ruiter; Kim, Yongin; Lauderdale, Diane; Lewis, Cora E; Reis, Jared P; Carnethon, Mercedes R; Knutson, Kristen; Glasser, Stephen J

    2013-11-01

    To investigate the longitudinal relationships between actigraph-derived sleep duration, fragmentation, and lipid levels. Longitudinal data from the Coronary Artery Risk Development in Young Adults Sleep Study (2003-05), an observational cohort at the Chicago site. There were 503 black and white adults, ages 32-51 years, with no prior history of cardiovascular disease. N/A. Sleep duration and fragmentation were measured using 6 days of wrist actigraphy. Sleep quality was measured with the Pittsburgh Sleep Quality Index. The outcome variables, measured at 3 examinations over 10 years (Baseline [2000-01], 5-year [2005-06], and 10-year follow-up [2010-11]), were total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides (TG), and TC/HDL ratio. The associations between each sleep parameter and 10-year change in lipids were analyzed with generalized estimating equation models adjusting for relevant confounders. After adjustment, each hour increase in sleep duration was significantly associated with higher TC (5.2 mg/dL, 95%CI: 1.7, 8.6) and LDL (3.4 mg/dL, 95%CI: 0.2, 6.6) in the total sample, a 1.1 mg/dL increase in TG (95%CI: 1.0, 1.1) among men, and a borderline significant greater odds for a TC/HDL ratio ≥ 5 among men (OR: 1.37, 95%CI: 0.99, 1.90). Overall, sleep fragmentation and sleep quality scores were not associated with change in lipids. Beyond relevant covariates, over a 10-year follow-up, longer objective sleep duration was longitudinally and significantly associated with a poorer lipid profile. Greater objective sleep fragmentation and self-reported poor sleep quality were not related to a poorer lipid profile.

  14. INCAP Oriente longitudinal study: 40 years of history and legacy.

    PubMed

    Ramirez-Zea, Manuel; Melgar, Paul; Rivera, Juan A

    2010-02-01

    Our purpose in this article is to describe the objectives, design, overall coverage, and main domains of data collection of the Institute of Nutrition of Central America and Panama Oriente Longitudinal Study and subsequent follow-up studies. This supplementary feeding trial targeted to pregnant and lactating women and children from birth to 7 y of age, conducted in 4 rural Guatemalan villages (1969-77) with a series of follow-up studies (1988-2007), is one of the richest sources of information on the effects of nutrition, growth, development, and human capital in the developing world, with outstanding data from gestation to adult age and 40 y of follow-up. Its results have influenced nutrition knowledge and policy with over 300 scientific publications. We present brief descriptions of preliminary studies that were critical for the success of the trial and the design and methods used during the trial and in the follow-up studies, in chronological order.

  15. Influence of cat characteristics on Fel d 1 levels in the home.

    PubMed

    Nicholas, Charlotte; Wegienka, Ganesa; Havstad, Suzanne; Ownby, Dennis; Johnson, Christine Cole

    2008-07-01

    Previous studies investigating cat characteristics and cat allergen production focused on clinical experiments that quantified allergen from either the shaved skin or the fur of the animal; however, these studies did not address these experimental relationships in the home. To determine the relationships between cat characteristics and cat allergen isolated from household dust. Fel d 1 allergen levels in dust from homes participating in a population-based study of environmental effect on allergy development were analyzed using a standard monoclonal antibody-based assay. Cat characteristics were based on interviews conducted during home visits by study personnel. Households with any cats had higher geometric mean Fel d 1 levels than households without cats (32.88 vs 0.43; P < .01), and cat allergen levels increased with increasing numbers of cats in the home (P < .01). Length of cat hair, cat sex, reproductive status, and time spent indoors were analyzed; the only characteristic associated with higher levels of Fel d 1 was whether the cat had been neutered or spayed. Having cats in the home is significantly associated with increased Fel d 1 levels, and having more cats in the home is correlated with more cat allergen. Cat reproductive characteristics may be associated with measurable differences in cat allergen levels.

  16. Optical design and performance of an XUV FEL (free-electron laser) oscillator

    SciTech Connect

    Goldstein, J.C.; McVey, B.D.; Newnam, B.E.

    1989-01-01

    A study of numerical simulation of the performance of a multifacet metal mirror ring resonator FEL is presented for several XUV wavelengths. Laser performance in the presence of mirror aberrations and thermal distortion is calculated for two different output coupling methods, a scraper mirror and a hole. 11 refs., 1 fig.

  17. Generation of doublet spectral lines at self-seeded X-ray FELs

    NASA Astrophysics Data System (ADS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2011-06-01

    Self-seeding schemes, consisting of two undulators with a monochromator in between, aim to reduce the bandwidth of SASE X-ray FELs. We recently proposed to use a new method of monochromatization exploiting a single crystal in Bragg transmission geometry for self-seeding in the hard X-ray range. The obvious and technically possible extension is to use such kind of monochromator setup with two (or more) crystals arranged in a series to spectrally filter the SASE radiation at two (or more) closely-spaced wavelengths within the FEL gain band. This allows for the production of doublet (or multiplet) spectral lines. Exploitations of such mode of operation involve any situation where there is a large change in cross-section over a narrow wavelength range. In this paper we consider the simultaneous operation of the LCLS hard X-ray FEL at two closely spaced wavelengths. We present simulation results for the LCLS baseline, and we show that this method can produce fully coherent radiation shared between two longitudinal modes. Mode spacing can be easily tuned within the FEL gain band, i.e. within 10 eV. An interesting aspect of the proposed scheme is a way of modulating the electron bunch at optical frequencies without a seed quantum laser. In fact, the XFEL output intensity contains an oscillating "mode-beat" component whose frequency is related to the frequency difference between the pair of longitudinal modes considered. Thus, at saturation one obtains FEL-induced modulations of energy loss and energy spread in the electron bunch at optical frequency. These modulations can be converted into density modulation at the same optical frequency with the help of a weak chicane installed behind the baseline undulator. Powerful coherent radiation can then be generated with the help of an optical transition radiation (OTR) station, which have important applications. In this paper we briefly consider how the doublet structure of the XFEL generation spectra can be monitored by an

  18. A Longitudinal Study of Memory Advantages in Bilinguals

    PubMed Central

    Ljungberg, Jessica K.; Hansson, Patrik; Andrés, Pilar; Josefsson, Maria; Nilsson, Lars-Göran

    2013-01-01

    Typically, studies of cognitive advantages in bilinguals have been conducted previously by using executive and inhibitory tasks (e.g. Simon task) and applying cross-sectional designs. This study longitudinally investigated bilingual advantages on episodic memory recall, verbal letter and categorical fluency during the trajectory of life. Monolingual and bilingual participants (n = 178) between 35–70 years at baseline were drawn from the Betula Prospective Cohort Study of aging, memory, and health. Results showed that bilinguals outperformed monolinguals at the first testing session and across time both in episodic memory recall and in letter fluency. No interaction with age was found indicating that the rate of change across ages was similar for bilinguals and monolinguals. As predicted and in line with studies applying cross-sectional designs, no advantages associated with bilingualism were found in the categorical fluency task. The results are discussed in the light of successful aging. PMID:24023803

  19. Longitudinal and transverse mode evolution in free electron laser

    SciTech Connect

    Dattoli, G.; Giannessi, L.; Georgii, R.

    1995-12-31

    We use the method of Padg approximants and Fourier transform techniques to treat analytically the problem of transverse and longitudinal mode evolution in FELs. We obtain simple relations providing a transparent understanding of the dynamic of pulse propagation effects and of transverse mode guiding. We discuss the interplay with inhomogeneous broadening effects and derive gain formulae including longitudinal and transverse mode couplings.

  20. Design of High Power FELS and the Effects of Diffraction on Detuning in an FEL Oscillator

    DTIC Science & Technology

    2015-12-01

    DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) In experiments going back to the first free electron laser (FEL) oscillator at Stanford, the measured...Advisor Keith Cohn Second Reader Kevin Smith Chair, Department of Physics iii THIS PAGE INTENTIONALLY LEFT BLANK iv ABSTRACT In experiments going back to

  1. Postural changes in dental hygienists. Four-year longitudinal study.

    PubMed

    Barry, R M; Woodall, W R; Mahan, J M

    1992-01-01

    Numerous surveys identify the occurrence of musculoskeletal complaints as a concern in dentistry. However, no longitudinal data exist to indicate whether postural changes occur as a result of practicing dental hygiene. The purpose of this preliminary, four-year longitudinal study was to investigate whether any postural changes developed during the hygienists' clinical education and/or during subsequent dental hygiene practice after one and/or two years. It was anticipated that the awkward positions and intense physical demands placed on hygienists might initiate musculoskeletal problems, but that no postural changes would occur over this short period of time. Nine of 10 dental hygienists in the graduating class of 1987 were surveyed for existing musculoskeletal complaints, and the subjects were photographed for a measurement of postural change. Responses from participants indicated an increase in musculoskeletal-related complaints in each of the six areas investigated. The photographic findings indicated that one of the nine hygienists showed an increase in forward head posture, a postural change.

  2. Longitudinal bunch dynamics study with coherent synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Billinghurst, B. E.; Bergstrom, J. C.; Baribeau, C.; Batten, T.; May, T. E.; Vogt, J. M.; Wurtz, W. A.

    2016-02-01

    An electron bunch circulating in a storage ring constitutes a dynamical system with both longitudinal and transverse degrees of freedom. Through a self-interaction with the wakefields created by the bunch, certain of these degrees may get excited, defining a set of eigenmodes analogous to a spectroscopic series. The present study focuses on the longitudinal modes of a single bunch. The excitation of a mode appears as an amplitude modulation at the mode frequency of the coherent synchrotron radiation (CSR) emitted by the bunch. The modulations are superimposed on a much larger continuum from CSR emission in the continuous mode. A given eigenmode is classified by the integer m which is the ratio of the mode frequency to the synchrotron frequency. The present measurements extend up to m =8 and focus on the region near the instability thresholds. At threshold the modes are excited sequentially, resembling a staircase when the mode frequencies are plotted as a function of bunch length or synchrotron frequency. Adjacent modes are observed to coexist at the boundaries between the modes. An energy-independent correlation is observed between the threshold current for an instability and the corresponding zero-current bunch length. Measurements were made at five beam energies between 1.0 and 2.9 GeV at the Canadian Light Source. The CSR was measured in the time domain using an unbiased Schottky diode spanning 50-75 GHz.

  3. Recruitment and retention in a longitudinal palliative care study.

    PubMed

    Sherman, Deborah Witt; McSherry, Christina Beyers; Parkas, Valerie; Ye, Xiang Y; Calabrese, Miriam; Gatto, Maria

    2005-08-01

    A longitudinal feasibility study regarding quality of life and interventions for patients with advanced cancer or AIDS and their family caregivers was conducted to determine issues related to their recruitment and retention and to obtain pilot data relevant to the development of a larger study. At the completion of the study, a focus group consisting of the members of the palliative care research team was convened to identify barriers to and facilitators of the research process based on their research experience. The purpose of this article is to (1) describe recruitment, mortality rates, attrition rates, and compliance with data collection of patients and family caregivers experiencing an advanced illness and to (2) examine the researchers' perspectives regarding barriers to and facilitators of the research process that relate to patients and family caregivers, institutions, the data collection process, and their personal experiences. Implications for palliative care research are discussed.

  4. Longitudinal Study: Efficacy of Online Technology Tools for Instructional Use

    NASA Technical Reports Server (NTRS)

    Uenking, Michael D.

    2011-01-01

    Studies show that the student population (secondary and post secondary) is becoming increasingly more technologically savvy. Use of the internet, computers, MP3 players, and other technologies along with online gaming has increased tremendously amongst this population such that it is creating an apparent paradigm shift in the learning modalities of these students. Instructors and facilitators of learning can no longer rely solely on traditional lecture-based lesson formals. In order to achieve student academic success and satisfaction and to increase student retention, instructors must embrace various technology tools that are available and employ them in their lessons. A longitudinal study (January 2009-June 2010) has been performed that encompasses the use of several technology tools in an instructional setting. The study provides further evidence that students not only like the tools that are being used, but prefer that these tools be used to help supplement and enhance instruction.

  5. A Longitudinal Examination of Childhood Maltreatment and Adolescent Obesity: Results from the National Longitudinal Study of Adolescent Health (AddHealth) Study

    ERIC Educational Resources Information Center

    Shin, Sunny Hyucksun; Miller, Daniel P.

    2012-01-01

    Objectives: We sought to explore the association between childhood maltreatment (e.g., neglect, physical and sexual abuse) and longitudinal growth trajectories of body mass index (BMI) from adolescence to young adulthood. Methods: We used latent curve modeling to examine data from the National Longitudinal Study of Adolescent Health (N = 8,471),…

  6. A Longitudinal Examination of Childhood Maltreatment and Adolescent Obesity: Results from the National Longitudinal Study of Adolescent Health (AddHealth) Study

    ERIC Educational Resources Information Center

    Shin, Sunny Hyucksun; Miller, Daniel P.

    2012-01-01

    Objectives: We sought to explore the association between childhood maltreatment (e.g., neglect, physical and sexual abuse) and longitudinal growth trajectories of body mass index (BMI) from adolescence to young adulthood. Methods: We used latent curve modeling to examine data from the National Longitudinal Study of Adolescent Health (N = 8,471),…

  7. Longitudinal Studies of Attitude Change: Issues and Methods

    DTIC Science & Technology

    1975-04-01

    relative contributions of variables which are presently influencing attitudes from historical variables. Conversely a longitudinal method can be used to...different training techniques. Neidt and Meredith (1966) used a longitudinal method to determine the changes in attitudes of a single group of Air... longitudinal method is viewed as the most promising for measurement of change. With the increasing improvement in unobtrusive measures (e.g., Webb

  8. Where Would Economics Education Be without Rendigs Fels?

    ERIC Educational Resources Information Center

    Siegfried, John J.; And Others

    1994-01-01

    Discusses the career of Rendigs Fels from his first academic appointment in 1948 until the present. Concludes that Fels is one of a small number of respected economists who have made interest, involvement, and research in the teaching of economics an important and respectable part of the profession. (CFR)

  9. Proposed uv-FEL user facility at BNL

    SciTech Connect

    Ben-Zvi, I.; Di Mauro, L.F.; Krinsky, S.; White, M.G.; Yu, L.H.; Batchelor, K.; Friedman, A.; Fisher, A.S.; Halama, H.; Ingold, G.; Johnson, E.D.; Kramer, S.; Rogers, J.T.; Solomon, L.; Wachtel, J.; Zhang, X.

    1991-01-01

    The NSLS at Brookhaven National Laboratory is proposing the construction of a UV-FEL operating in the wavelength range from visible to 750{Angstrom}. Nano-Coulomb electron pulses will be generated at a laser photo-cathode RF gun at a repetition rate of 10 KHz. The 6 ps pulses will be accelerated to 250 MeV in a superconducting linac. The FEL output will serve four stations with independent wavelength tuning, using two wigglers and two rotating mirror beam switches. Seed radiation for the FEL amplifiers will be provided by conventional tunable lasers, and the final frequency multiplication from the visible or near UV to the VUV will be carried out in the FEL itself. Each FEL will comprise of an initial wiggler resonant to the seed wavelength, a dispersion section, and a second wiggler resonant to the output wavelength. The facility will provide pump probe capability, FEL or FEL, and FEL on synchrotron light from an insersion device on the NSLS X-Ray ring. 15 refs., 2 figs., 3 tabs.

  10. Gain results for low voltage FEL

    SciTech Connect

    Shaw, A.; Stuart, R.A.; Al-Shamma`a, A.

    1995-12-31

    We have designed and constructed a low voltage (130 kV) FEL system capable of operating in the microwave frequency range for which the electron beam current is cw (rather than pulsed) in time at a level of {approximately} 12 mA. The gain of this system has been measured as a function of the electron beam accelerating voltage and current level, and the input microwave frequency (8-10 GHz). The results are compared with the predictions of a simple theoretical model.

  11. Hearing loss in the Royal Norwegian Navy: A longitudinal study

    PubMed Central

    Irgens-Hansen, Kaja; Baste, Valborg; Bråtveit, Magne; Lind, Ola; Koefoed, Vilhelm F.; Moen, Bente E

    2016-01-01

    The aims of this longitudinal study were to investigate a significant threshold shift (STS) among personnel working on board the Royal Norwegian Navy's (RNoN) vessels between 2012 and 2014 and to identify possible determinants of STS. Hearing thresholds were measured by pure tone audiometry in two consecutive examinations (n = 226). STS was defined as an average change in hearing thresholds ≥ + 10 dB at 2,000 Hz, 3,000 Hz, and 4,000 Hz in either ear. Determinants of STS were assessed through a questionnaire. The incidence of STS was 23.0%. Significant determinants of STS were the number of episodes of temporary threshold shifts (TTS) in the Navy, exposure to continuous loud noise during work on board, and the number of gun shots (in the Navy, hunting, and sports). This study indicated a significant association between noise exposure on board Navy vessels and development of STS. PMID:27157689

  12. Α Markov model for longitudinal studies with incomplete dichotomous outcomes.

    PubMed

    Efthimiou, Orestis; Welton, Nicky; Samara, Myrto; Leucht, Stefan; Salanti, Georgia

    2017-03-01

    Missing outcome data constitute a serious threat to the validity and precision of inferences from randomized controlled trials. In this paper, we propose the use of a multistate Markov model for the analysis of incomplete individual patient data for a dichotomous outcome reported over a period of time. The model accounts for patients dropping out of the study and also for patients relapsing. The time of each observation is accounted for, and the model allows the estimation of time-dependent relative treatment effects. We apply our methods to data from a study comparing the effectiveness of 2 pharmacological treatments for schizophrenia. The model jointly estimates the relative efficacy and the dropout rate and also allows for a wide range of clinically interesting inferences to be made. Assumptions about the missingness mechanism and the unobserved outcomes of patients dropping out can be incorporated into the analysis. The presented method constitutes a viable candidate for analyzing longitudinal, incomplete binary data.

  13. Semiparametric Stochastic Modeling of the Rate Function in Longitudinal Studies

    PubMed Central

    Zhu, Bin; Taylor, Jeremy M.G.; Song, Peter X.-K.

    2011-01-01

    In longitudinal biomedical studies, there is often interest in the rate functions, which describe the functional rates of change of biomarker profiles. This paper proposes a semiparametric approach to model these functions as the realizations of stochastic processes defined by stochastic differential equations. These processes are dependent on the covariates of interest and vary around a specified parametric function. An efficient Markov chain Monte Carlo algorithm is developed for inference. The proposed method is compared with several existing methods in terms of goodness-of-fit and more importantly the ability to forecast future functional data in a simulation study. The proposed methodology is applied to prostate-specific antigen profiles for illustration. Supplementary materials for this paper are available online. PMID:22423170

  14. Α Markov model for longitudinal studies with incomplete dichotomous outcomes

    PubMed Central

    Welton, Nicky; Samara, Myrto; Leucht, Stefan; Salanti, Georgia

    2016-01-01

    Missing outcome data constitute a serious threat to the validity and precision of inferences from randomized controlled trials. In this paper, we propose the use of a multistate Markov model for the analysis of incomplete individual patient data for a dichotomous outcome reported over a period of time. The model accounts for patients dropping out of the study and also for patients relapsing. The time of each observation is accounted for, and the model allows the estimation of time‐dependent relative treatment effects. We apply our methods to data from a study comparing the effectiveness of 2 pharmacological treatments for schizophrenia. The model jointly estimates the relative efficacy and the dropout rate and also allows for a wide range of clinically interesting inferences to be made. Assumptions about the missingness mechanism and the unobserved outcomes of patients dropping out can be incorporated into the analysis. The presented method constitutes a viable candidate for analyzing longitudinal, incomplete binary data. PMID:27917593

  15. Longitudinal study of spatial working memory development in young children.

    PubMed

    Tsujii, Takeo; Yamamoto, Eriko; Masuda, Sayako; Watanabe, Shigeru

    2009-05-27

    This study longitudinally compared activity in the frontal cortex during a spatial working memory task between 5-year-old and 7-year-old children using near-infrared spectroscopy. Eight children participated in this study twice, once at 5 years and once at 7 years of age. Behavioral analysis showed that older children performed the working memory task more precisely and more rapidly than younger children. Near-infrared spectroscopy analysis showed that right hemisphere dominance was observed in older children, whereas no hemispheric difference was apparent in younger children. Children with strengthened lateralization showed improved performance from 5 to 7 years. We therefore offer the first demonstration of the developmental changes in frontal cortical activation during spatial working memory tasks during the preschool period.

  16. Imputation of incident events in longitudinal cohort studies.

    PubMed

    Howard, George; McClure, Leslie A; Moy, Claudia S; Safford, Monika M; Cushman, Mary; Judd, Suzanne E; Kissela, Brett M; Kleindorfer, Dawn O; Howard, Virginia J; Rhodes, David J; Muntner, Paul; Tiwari, Hemant K

    2011-09-15

    Longitudinal cohort studies normally identify and adjudicate incident events detected during follow-up by retrieving medical records. There are several reasons why the adjudication process may not be successfully completed for a suspected event including the inability to retrieve medical records from hospitals and an insufficient time between the suspected event and data analysis. These "incomplete adjudications" are normally assumed not to be events, an approach which may be associated with loss of precision and introduction of bias. In this article, the authors evaluate the use of multiple imputation methods designed to include incomplete adjudications in analysis. Using data from the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study, 2008-2009, they demonstrate that this approach may increase precision and reduce bias in estimates of the relations between risk factors and incident events.

  17. Study of weld offset in longitudinally welded SSME HPFTP inlet

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Spanyer, K. S.; Brunair, R. M.

    1992-01-01

    Welded joints are an essential part of rocket engine structures such as the Space Shuttle Main Engine (SSME) turbopumps. Defects produced in the welding process can be detrimental to weld performance. Recently, review of the SSME high pressure fuel turbopump (HPFTP) titanium inlet X-rays revealed several weld discrepancies such as penetrameter density issues, film processing discrepancies, weld width discrepancies, porosity, lack of fusion, and weld offsets. Currently, the sensitivity of welded structures to defects is of concern. From a fatigue standpoint, weld offset may have a serious effect since local yielding, in general, aggravates cyclic stress effects. Therefore, the weld offset issue is considered in this report. Using the FEM and beamlike plate approximations, parametric studies were conducted to determine the influence of weld offsets and a variation of weld widths in longitudinally welded cylindrical structures with equal wall thicknesses on both sides of the joint. Following the study, some conclusions are derived for the weld offsets.

  18. Optimization for Single-Spike X-Ray FELs at LCLS with a Low Charge Beam

    SciTech Connect

    Wang, L.; Ding, Y.; Huang, Z.; /SLAC

    2011-12-14

    -compression mode, although the photon number is less than that from under-compression or over-compression mode. Since we cannot measure the x-ray pulse length at this time scale, the machine is typically optimized for generating maximum photons, not minimum pulse length. In this paper, we study the methods of producing femtosecond (or single-spike) x-ray pulses at LCLS with 20 pC charge, based on start-to-end simulations. Figure 1 shows a layout of LCLS. The compression in the second bunch compressor (BC2) determines the final e-beam bunch length. However, the laser heater, dog-leg after the main linac (DL2) and collective effects also affect the final bunch length. To adjust BC2 compression, we can either change the L2 phase or BC2 R{sub 56}. In this paper we only tune L2 phase while keep BC2 R{sub 56} fixed. For the start-to-end simulations, we used IMPACT-T and ELEGANT tracking from the photocathode to the entrance of the undulator, after that the FEL radiation was simulated with GENESIS. IMPACT-T tracks about 10{sup 6} particles in the injector part until 135 MeV, including 3D space charge force. The output particles from IMPACT-T are smoothed and increased to 12 x 10{sup 6} to reduce high-frequency numerical noise for subsequent ELEGANT simulations, which include linear and nonlinear transport effects, a 1D transient model of CSR, and longitudinal space charge effects, as well as geometric and resistive wake fields in the accelerator. In GENESIS part, the longitudinal wake field from undulator chamber and longitudinal space field are also included.

  19. Experimental setups for FEL-based four-wave mixing experiments at FERMI

    SciTech Connect

    Bencivenga, Filippo; Zangrando, Marco; Svetina, Cristian; Abrami, Alessandro; Battistoni, Andrea; Borghes, Roberto; Capotondi, Flavio; Cucini, Riccardo; Dallari, Francesco; Danailov, Miltcho; Demidovich, Alexander; Fava, Claudio; Gaio, Giulio; Gerusina, Simone; Gessini, Alessandro; Giacuzzo, Fabio; Gobessi, Riccardo; Godnig, Roberto; Grisonich, Riccardo; Kiskinova, Maya; Kurdi, Gabor; Loda, Giorgio; Lonza, Marco; Mahne, Nicola; Manfredda, Michele; Mincigrucci, Riccardo; Pangon, Gianpiero; Parisse, Pietro; Passuello, Roberto; Pedersoli, Emanuele; Pivetta, Lorenzo; Prica, Milan; Principi, Emiliano; Rago, Ilaria; Raimondi, Lorenzo; Sauro, Roberto; Scarcia, Martin; Sigalotti, Paolo; Zaccaria, Maurizio; Masciovecchio, Claudio

    2016-01-01

    The recent advent of free-electron laser (FEL) sources is driving the scientific community to extend table-top laser research to shorter wavelengths adding elemental selectivity and chemical state specificity. Both a compact setup (mini-TIMER) and a separate instrument (EIS-TIMER) dedicated to four-wave-mixing (FWM) experiments has been designed and constructed, to be operated as a branch of the Elastic and Inelastic Scattering beamline: EIS. The FWM experiments that are planned at EIS-TIMER are based on the transient grating approach, where two crossed FEL pulses create a controlled modulation of the sample excitations while a third time-delayed pulse is used to monitor the dynamics of the excited state. This manuscript describes such experimental facilities, showing the preliminary results of the commissioning of the EIS-TIMER beamline, and discusses original experimental strategies being developed to study the dynamics of matter at the fs–nm time–length scales. In the near future such experimental tools will allow more sophisticated FEL-based FWM applications, that also include the use of multiple and multi-color FEL pulses.

  20. Transient absorption spectroscopy using the super-ACO storage ring FEL

    NASA Astrophysics Data System (ADS)

    Renault, Eric; Nahon, Laurent; Nutarelli, Daniele; Garzella, David; Merola, F.; Couprie, Marie-Emmanuelle

    2000-04-01

    The Super-ACO storage ring FEL is operating with a high average power in the UV range (300 mW at 350 nm), and recently at wavelengths down to 300 nm. In addition this source exhibits high stability and long lifetime which makes it a unique tool for user applications. The coupling of the FEL with other synchrotron based sources (bending magnet and undulator) opens many unexplored possibilities for various types of two-color time-resolved spectroscopies. Presently, we are developing a two-color experiment where we study the sub-nanosecond time-resolved absorption of different chromophoric compounds. In this type of pump-probe experiments, the intense UV pulse of the Super-ACO FEL is used to prepare a high initial concentration of chromophores in their first singlet electronic excited state. The nearby bending magnet synchrotron radiation provides on the other hand a pulsed, white light continuum ranging from UV to IR, which is naturally synchronized with the FEL pulses and can be used to probe the photochemical subsequent events and the transient species. With a dye molecule (POPOP), we have obtained a two-color effect which demonstrates the feasibility of the experiment in terms of flux. Applications on various chromophores of biological interest are planned.

  1. Numerical modeling of thermal loading of diamond crystal in X-ray FEL oscillators

    NASA Astrophysics Data System (ADS)

    Song, Mei-Qi; Zhang, Qing-Min; Guo, Yu-Hang; Li, Kai; Deng, Hai-Xiao

    2016-04-01

    Due to high reflectivity and high resolution of X-ray pulses, diamond is one of the most popular Bragg crystals serving as the reflecting mirror and mono-chromator in the next generation of free electron lasers (FELs). The energy deposition of X-rays will result in thermal heating, and thus lattice expansion of the diamond crystal, which may degrade the performance of X-ray FELs. In this paper, the thermal loading effect of diamond crystal for X-ray FEL oscillators has been systematically studied by combined simulation with Geant4 and ANSYS, and its dependence on the environmental temperature, crystal size, X-ray pulse repetition rate and pulse energy are presented. Our results show that taking the thermal loading effects into account, X-ray FEL oscillators are still robust and promising with an optimized design. Supported by National Natural Science Foundation of China (11175240, 11205234, 11322550) and Program for Changjiang Scholars and Innovative Research Team in University (IRT1280)

  2. Method for separating FEL output beams from long wavelength radiation

    DOEpatents

    Neil, George; Shinn, Michelle D.; Gubeli, Joseph

    2016-04-26

    A method for improving the output beam quality of a free electron laser (FEL) by reducing the amount of emission at wavelengths longer than the electron pulse length and reducing the amount of edge radiation. A mirror constructed of thermally conductive material and having an aperture therein is placed at an oblique angle with respect to the beam downstream of the bending magnet but before any sensitive use of the FEL beam. The aperture in the mirror is sized to deflect emission longer than the wavelength of the FEL output while having a minor impact on the FEL output beam. A properly sized aperture will enable the FEL radiation, which is coherent and generally at a much shorter wavelength than the bending radiations, to pass through the aperture mirror. The much higher divergence bending radiations will subsequently strike the aperture mirror and be reflected safely out of the way.

  3. Gastrocnemius muscle contracture after spinal cord injury: a longitudinal study.

    PubMed

    Diong, Joanna; Harvey, Lisa A; Kwah, Li Khim; Clarke, Jillian L; Bilston, Lynne E; Gandevia, Simon C; Herbert, Robert D

    2013-07-01

    The aim of this study was to examine changes in passive length and stiffness of the gastrocnemius muscle-tendon unit in people after spinal cord injury. In a prospective longitudinal study, eight wheelchair-dependent participants with severe paralysis were assessed 3 and 12 mos after spinal cord injury. Passive torque-angle data were obtained as the ankle was slowly rotated through range at six knee angles. Differences in passive ankle torque-angle data recorded at different knee angles were used to derive passive length-tension curves of the gastrocnemius muscle-tendon unit. Ultrasound imaging was used to determine fascicle and tendon contributions to the muscle-tendon unit length-tension curves. The participants had ankle contractures (mean [SD] maximum passive ankle dorsiflexion angle, 88 [9] degrees) 3 mos after spinal cord injury. Ankle range did not worsen significantly during the subsequent 9 mos (mean change, -5 degrees; 95% confidence interval, -16 to 6 degrees). There were no changes in the mean slack length or the stiffness of the gastrocnemius muscle-tendon unit or in the slack lengths of the fascicles or the tendon between 3 and 12 mos after spinal cord injury. There were no consistent patterns of the change in slack length or stiffness with the changes in ankle range in the data from the individual participants. This study, the first longitudinal study of muscle length and stiffness after spinal cord injury, showed that the length and the stiffness of the gastrocnemius did not change substantially between 3 and 12 mos after injury.

  4. Rationales, design and recruitment of the Taizhou Longitudinal Study

    PubMed Central

    Wang, Xiaofeng; Lu, Ming; Qian, Ji; Yang, Yajun; Li, Shilin; Lu, Daru; Yu, Shunzhang; Meng, Wei; Ye, Weimin; Jin, Li

    2009-01-01

    Background Rapid economic growth in China in the past decades has been accompanied by dramatic changes in lifestyle and environmental exposures. The burdens of non-communicable diseases, such as cardiovascular diseases, diabetes and cancer, have also increased substantially. Methods/design We initiated a large prospective cohort–the Taizhou Longitudinal Study–in Taizhou (a medium-size city in China) to explore the environmental and genetic risk factors for common non-communicable diseases. The sample size of the cohort will be at least 100,000 adults aged 30–80 years drawn from the general residents of the districts of Hailin, Gaogang, and Taixing (sample frame, 1.8 million) of Taizhou. A three-stage stratified sampling method will be applied. Baseline investigations include interviewer-administered questionnaire, anthropometric measurements, and collection of buccal mucosal cells and blood specimens. DNA will be extracted for genetic studies and serum samples will be used for biochemical examinations. A follow-up survey will be conducted every three years to obtain information on disease occurrence and information on selected lifestyle exposures. Study participants will be followed-up indefinitely by using a chronic disease register system for morbidity and cause-specific mortality. Information on non-fatal events will be obtained for certain major categories of disease (e.g., cancer, stroke, myocardial infarction) through established registry systems. Discussion The Taizhou Longitudinal Study will provide a good basis for exploring the roles of many important environmental factors (especially those concomitant with the economic transformation in China) for common chronic diseases, solely or via interaction with genetic factors. PMID:19589173

  5. A Longitudinal Study of Uremic Pruritus in Hemodialysis Patients

    PubMed Central

    Mathur, Vandana S.; Lindberg, Jill; Germain, Michael; Block, Geoffrey; Tumlin, James; Smith, Mark; Grewal, Mandeep

    2010-01-01

    Background and objectives: Although uremic pruritus (UP) is a highly prevalent complication of chronic kidney disease, it remains poorly characterized. There have been no longitudinal studies of natural history, and no health-related quality of life (HR-QOL) instruments have been developed for UP. The objectives of this study were to describe the natural history of UP, to compare rating scales of itching intensity, and to assess usefulness and validity of HR-QOL instruments for UP. Design, setting, participants, & measurements: The intensity, severity, and effects of pathologic itching on HR-QOL were assessed prospectively in 103 patients with UP on chronic hemodialysis. Outcome measures were obtained at scheduled intervals over 3.5 months. Results: Itching daily or nearly daily was reported by 84% of patients and had been ongoing for >1 year in 59%. In 83%, pruritus involved large, nondermatomal areas with striking bilateral symmetry. Two thirds of the patients were using medications such as antihistamines, steroids, and various emollients without satisfactory relief of itching. Statistically significant associations were found among itching intensity, severity, and HR-QOL measures in domains such as mood, social relations, and sleep. Among patients with moderate-to-severe UP, changes in itching intensity of 20% or greater were associated with significant reductions in HR-QOL measures. Conclusions: This first longitudinal study of UP describes key features of UP and its effect on HR-QOL. The assessment instruments we have developed are easily used, are responsive to changes in UP intensity, and should facilitate clinical evaluation and research to meet the needs of afflicted patients. PMID:20558560

  6. A longitudinal study of children with developmental dysphasia.

    PubMed

    Dlouhá, O

    2007-01-01

    This study reports longitudinal follow-up of 300 children with developmental dysphasia. Their expressive disturbances are a manifestation of their auditory decoding impairment. These children were investigated on battery of tests of spoken language, of phonological processing and of different audiometric procedures, in order to register all the information necessary to be able judge the speech-language development. The tests focused on diagnosis of central auditory disorder, confirmed the difficulties in association area in children with developmental dysphasia. In speech perception, the temporal processing is one of the functions necessary for the discrimination of phonemes, and of similar words. Our results confirmed long-term problems of children with developmental dysphasia with central auditory perception disorder.

  7. Facial expression recognition in Alzheimer's disease: a longitudinal study.

    PubMed

    Torres, Bianca; Santos, Raquel Luiza; Sousa, Maria Fernanda Barroso de; Simões Neto, José Pedro; Nogueira, Marcela Moreira Lima; Belfort, Tatiana T; Dias, Rachel; Dourado, Marcia Cristina Nascimento

    2015-05-01

    Facial recognition is one of the most important aspects of social cognition. In this study, we investigate the patterns of change and the factors involved in the ability to recognize emotion in mild Alzheimer's disease (AD). Through a longitudinal design, we assessed 30 people with AD. We used an experimental task that includes matching expressions with picture stimuli, labelling emotions and emotionally recognizing a stimulus situation. We observed a significant difference in the situational recognition task (p ≤ 0.05) between baseline and the second evaluation. The linear regression showed that cognition is a predictor of emotion recognition impairment (p ≤ 0.05). The ability to perceive emotions from facial expressions was impaired, particularly when the emotions presented were relatively subtle. Cognition is recruited to comprehend emotional situations in cases of mild dementia.

  8. Early cognitive profiles of emergent readers: a longitudinal study.

    PubMed

    Brunswick, Nicola; Neil Martin, G; Rippon, Georgina

    2012-02-01

    This longitudinal study examined the contribution of phonological awareness, phonological memory, and visuospatial ability to reading development in 142 English-speaking children from the start of kindergarten to the middle of Grade 2. Partial cross-lagged analyses revealed significant relationships between early performance on block design and matching letter-like forms tasks and later reading ability. Rhyme awareness correlated with later reading ability during the earliest stages, but onset awareness did not emerge as important until after the children had started reading. Digit span correlated significantly with future reading ability at every stage. These findings indicate that although phonological awareness, phonological memory, and visuospatial ability are all necessary for emergent reading, their relative importance varies across the first 2 years of reading development.

  9. Body image among adolescent girls and boys: a longitudinal study.

    PubMed

    Carlson Jones, Diane

    2004-09-01

    This longitudinal study of adolescent girls and boys examined the contributions of social (peer appearance context), psychological (internalized appearance ideals and appearance social comparison), and biological (body mass) factors to the development of body dissatisfaction. Students (165 girls and 139 boys) completed questionnaires when they were either in 7th grade or 10th grade and again 1 year later. The results for the boys revealed a singular pathway to body dissatisfaction through internalized commitment to muscularity ideals. The prospective analyses of change in body dissatisfaction among the girls reflected the contributions of appearance conversations with friends, appearance social comparisons, and body mass. There was no evidence of mediation among the boys and limited support for it among the girls. Copyright 2004 American Psychological Association

  10. Nurses' ethical conflict with hospitals: a longitudinal study of outcomes.

    PubMed

    Gaudine, Alice; Thorne, Linda

    2012-11-01

    This study examined the association of nurses' ethical conflict with hospitals with organizational commitment, stress, turnover intention, absence and turnover. Participants were 410 nurses working at four different Canadian hospitals. A longitudinal design was used where nurses completed a questionnaire to capture ethical conflict, stress and organizational commitment, and one year later, measures of turnover intention, absence and actual turnover were obtained for the same sample. We found three aspects of nurses' ethical conflict with hospitals: patient care values, value of nurses, and staffing policy values. Our findings showed that all three aspects of nurses' ethical conflict are associated with stress and patient care values is associated with actual turnover. We also found that staffing policy values is predictive of turnover intention, and that patient care values is predictive of absenteeism. Thus, our findings show the multidimensionality of nurses' ethical conflict with hospitals. Further implications of our findings for practice and theory are discussed.

  11. Emotion recognition by children with Down syndrome: a longitudinal study.

    PubMed

    Pochon, Régis; Declercq, Christelle

    2013-12-01

    According to the literature, children with Down syndrome (DS) have difficulties recognising facial expressions. Yet abilities to recognise emotional expressions are often assessed in tasks that imply comprehension of words for emotions. We investigated the development of these abilities in children with DS in a longitudinal study that did not involve lexical knowledge of emotions. Children with DS and nonspecific intellectual disability and typically developing children matched for developmental age (DA) were assessed once a year over 3 years. They were asked to recognise the facial expression of an emotion after hearing a vocalisation. In each annual session, children with DS were not significantly different from others at recognising emotions. Their abilities to discriminate basic emotions improved significantly and to a similar extent to those of other children. The findings indicate that children with DS develop emotion recognition abilities similarly to other children of the same DA.

  12. J's rhymes: a longitudinal case study of language play.

    PubMed

    Inkelas, Sharon

    2003-08-01

    A longitudinal study of one child aged 2;5 documents an invented language game consisting of suffixal reduplication and onset replacement. Initially, reduplication is partial: the reduplicant enlarges in discrete increments over the five stages of the game until by the last stage reduplication is total. Reduplication is accompanied by a process of onset replacement, in which the reduplicant always begins with /b/. Early in the game, this replacive onset 'dissimilates' to /p/ whenever the reduplicant would independently have begun with /b/. In subsequent stages, other voiced obstruents trigger dissimilation as well. Though similar in many ways to adult language reduplication, it is argued that J's game may more closely resemble adult rhyme (both poetic and word rhyme). Regardless, the structure of the game clearly reveals the child's awareness, in the third year of life, of stress and metrical feet, segmental natural classes, and segments themselves (phonemic awareness).

  13. Skin conductance fear conditioning impairments and aggression: a longitudinal study.

    PubMed

    Gao, Yu; Tuvblad, Catherine; Schell, Anne; Baker, Laura; Raine, Adrian

    2015-02-01

    Autonomic fear conditioning deficits have been linked to child aggression and adult criminal behavior. However, it is unknown if fear conditioning deficits are specific to certain subtypes of aggression, and longitudinal research is rare. In the current study, reactive and proactive aggression were assessed in a sample of males and females when aged 10, 12, 15, and 18 years old. Skin conductance fear conditioning data were collected when they were 18 years old. Individuals who were persistently high on proactive aggression measures had significantly poorer conditioned responses at 18 years old when compared to others. This association was not found for reactive aggression. Consistent with prior literature, findings suggest that persistent antisocial individuals have unique neurobiological characteristics and that poor autonomic fear conditioning is associated with the presence of increased instrumental aggressive behavior.

  14. A longitudinal study of low back pain in student nurses.

    PubMed

    Klaber Moffett, J A; Hughes, G I; Griffiths, P

    1993-06-01

    Results from a longitudinal study of low back pain in 199 student nurses followed up for 20 months show that 37% reported back pain which lasted for at least 3 consecutive days. The first incidence peaked markedly between 9 and 12 months into training, and coincided with work on wards described by the nurses as "heavy". A combination of personal characteristics are also associated with back pain reports, within this group of nurses. These include attitudes to health as measured by the Health Locus of Control, low levels of trait anxiety, increased neuroticism, and emotional disturbance as measured by the General Health Questionnaire, the strength endurance of the thigh muscles (quadriceps), and height. Recommendations are made for: (1) the consideration of a modified training programme for lifting and handling; and (2) the need for a standardized system of recording back problems as suggested by the DHSS-commissioned Robens Institute (University of Surrey) Report.

  15. [Autoaggression and pulse rate--a longitudinal study].

    PubMed

    Rohmann, U H; Elbing, U; Hartmann, H

    1988-12-01

    This article presents a model of autoaggressive behavior in which a distinction is made between determining and maintaining factors. Specific environmental, in particular social, and organismic variables are linked to them. The two types of variables interact, thus causing or maintaining autoaggressive behavior. A theory of autoaggression must therefore rely on multicausal/multimodal explanations. A connection between autoaggression and a high level of arousal suggests itself. In this single-case longitudinal study a comparison was made between heart rate and frequency of autoaggressive behavior. High heart rates were found to be correlated with low frequencies of autoaggressive behavior and vice versa. Decreasing autoaggressive behavior was coupled with increasing muscle relaxation and increasing motor activity. However, abnormally high heart rates were associated with both low and high levels of motor activity.

  16. Health benefits of volunteering in the Wisconsin longitudinal study.

    PubMed

    Piliavin, Jane Allyn; Siegl, Erica

    2007-12-01

    We investigate positive effects of volunteering on psychological well-being and self-reported health using all four waves of the Wisconsin Longitudinal Study. Confirming previous research, volunteering was positively related to both outcome variables. Both consistency of volunteering over time and diversity of participation are significantly related to well-being and self-reported health. The relationship of volunteering to psychological well-being was moderated by level of social integration, such that those who were less well integrated benefited the most. Mattering appears to mediate the link between volunteering and wellbeing. Controls for other forms of social participation and for the predictors of volunteering are employed in analyses of well-being in 1992. We find volunteering effects on psychological well-being in 2004, controlling for 1992 wellbeing, thus providing strong evidence for a causal effect.

  17. Skin Conductance Fear Conditioning Impairments and Aggression: A Longitudinal Study

    PubMed Central

    Gao, Yu; Tuvblad, Catherine; Schell, Anne; Baker, Laura; Raine, Adrian

    2014-01-01

    Autonomic fear conditioning deficits have been linked to child aggression and adult criminal behavior. However, it is unknown if fear conditioning deficits are specific to certain subtypes of aggression, and longitudinal research is rare. In the current study, reactive and proactive aggression were assessed in a sample of males and females when aged 10, 12, 15, and 18 years old. Skin conductance fear conditioning data were collected when they were 18 years old. Individuals who were persistently high on proactive aggression measures had significantly poorer conditioned responses at 18 years old when compared to others. This association was not found for reactive aggression. Consistent with prior literature, findings suggest that persistent antisocial individuals have unique neurobiological characteristics and that poor autonomic fear conditioning is associated with the presence of increased instrumental aggressive behavior. PMID:25174802

  18. Longitudinal study of household smoking ban adoption among Korean Americans.

    PubMed

    Hughes, Suzanne C; Corcos, Isabel A; Hofstetter, C Richard; Hovell, Melbourne F; Irvin, Veronica L

    2009-11-01

    Few longitudinal studies have examined the adoption of bans on smoking in private homes. This longitudinal study examined: (1) the prevalence of home smoking bans at baseline, (2) the incidence and predictors of new ban implementation by follow-up, and (3) the reasons for banning smoking and the difficulties with enforcement. The sample consisted of 1360 adults of Korean descent residing in California who were interviewed by telephone (in English/Korean) at baseline during 2001-2002 and re-interviewed in 2006-2007. Data analyses were conducted in 2007-2008. The proportion of respondents with a complete household smoking ban grew from 59% at baseline to 91% by the follow-up interview. Among the 552 respondents who did not have a ban at baseline, 84% had adopted a ban by follow-up. Three baseline factors independently predicted ban adoption during the follow-up period: the presence of a nonsmoking respondent or spouse, the presence of nonsmoking family members, and respondent's belief that secondhand smoke caused lung cancer. The most highly rated reasons for banning smoking were as follows: because smoke annoys others, to protect family members, to avoid the odor, to discourage youth from smoking, and to encourage smokers to quit. Finally, respondents indicated that they would find it most difficult to ask their parent-in-law not to smoke. The proportion of households with smoking bans increased substantially, but households with smokers or family members who smoke remained less likely to implement bans. The importance of culturally sensitive programs to promote household bans cannot be overstated.

  19. Strategies for longitudinal neuroimaging studies of overt language production.

    PubMed

    Meltzer, Jed A; Postman-Caucheteux, Whitney A; McArdle, Joseph J; Braun, Allen R

    2009-08-15

    Longitudinal fMRI studies of language production are of interest for evaluating recovery from post-stroke aphasia, but numerous methodological issues remain unresolved, particularly regarding strategies for evaluating single subjects at multiple timepoints. To address these issues, we studied overt picture naming in eleven healthy subjects, scanned four times each at one-month intervals. To evaluate the natural variability present across repeated sessions, repeated scans were directly contrasted in a unified statistical framework on a per-voxel basis. The effect of stimulus familiarity was evaluated using explicitly overtrained pictures, novel pictures, and untrained pictures that were repeated across sessions. For untrained pictures, we found that activation declined across multiple sessions, equally for both novel and repeated stimuli. Thus, no repetition priming for individual stimuli at one-month intervals was found, but rather a general effect of task habituation was present. Using a set of overtrained pictures identical in each session, no decline was found, but activation was minimized and produced less consistent patterns across participants, as measured by intra-class correlation coefficients. Subtraction of a baseline task, in which subjects produced a stereotyped utterance to scrambled pictures, resulted in specific activations in the left inferior frontal gyrus and other language areas for untrained items, while overlearned stimuli relative to pseudo pictures activated only the fusiform gyrus and supplementary motor area. These findings indicate that longitudinal fMRI is an effective means of detecting changes in neural activation magnitude over time, as long as the effect of task habituation is taken into account.

  20. The nutritional situation in Swedish nursing homes - a longitudinal study.

    PubMed

    Borgström Bolmsjö, Beata; Jakobsson, Ulf; Mölstad, Sigvard; Ostgren, Carl Johan; Midlöv, Patrik

    2015-01-01

    Poor nutritional status is widespread among the elderly and is associated with increased morbidity and mortality. The aim of this study was to longitudinally describe the nutritional status in elderly people living in nursing homes. Nutritional status was recorded longitudinally in elderly people living in 11 different nursing homes in Sweden. Participants were examined at baseline by specially trained nurses who also assisted with questionnaires and collected data for current medical treatment from patient records. Nutritional status was evaluated at baseline and after 24 months with the mini nutritional assessment (MNA). The study included 318 subjects. The mean age of the participants was 85.0 years (range 65-101). At baseline, 41.6% were well nourished, 40.3% at risk of malnutrition, and 17.7% malnourished according to the MNA. Survival was significantly lower in the malnourished group. After 24 months, almost half of the population had died. The group of participants who survived at 24 months represents a population of better nutritional state, where 10.6% were malnourished at baseline increasing to 24.6% after 24 months. After 24 months, 38.7% of the participants showed a decline in nutritional state. The group with deteriorating MNA scores had higher weight, BMI values, and a higher hospitalization rate. The prevalence of malnutrition in nursing home residents increased over time and it is important to evaluate nutritional state regularly. Nutritional interventions should be considered in better nourished groups, as well as in malnourished individuals, to prevent a decline in nutritional state. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Inverse Compton gamma-ray source for nuclear physics and related applications at the Duke FEL

    SciTech Connect

    O`Shea, P.G.; Litvinenko, V.N.; Madey, J.M.J.

    1995-12-31

    In recent years the development of intense, short-wavelength FEL light sources has opened opportunities for the development new applications of high-energy Compton-backscattered photons. These applications range from medical imaging with X-ray photons to high-energy physics with {gamma}{gamma} colliders. In this paper we discuss the possibilities for nuclear physics studies using polarized Compton backscattered {gamma}-rays from the Duke storage-ring-driven UV-FEL. There are currently a number of projects that produce polarized {gamma}-rays for nuclear physics studies. All of these facilities operate by scattering conventional laser-light against electrons circulating in a storage ring. In our scheme, intra-cavity scattering of the UV-FEL light will produce a {gamma}-flux enhancement of approximately 10{sup 3} over existing sources. The Duke ring can operate at energies up to 1.2 GeV and can produce FEL photons up to 12.5 eV. We plan to generate {gamma}-rays up to 200 MeV in energy with an average flux in excess of 10{sup 7} /s/MeV, using a modest scattering beam of 10-mA average stored current. The {gamma}-ray energy may be tuned by varying the FEL wavelength or by adjusting the stored electron beam energy. Because of the intense flux, we can eliminate the need for photon energy tagging by collimating of the {gamma}-ray beam. We will discuss the characteristics of the device and its research opportunities.

  2. High power induction linac for FEL applications at CESTA

    NASA Astrophysics Data System (ADS)

    Launspach, J.; Angles, J. M.; Angles, M.; Anthouard, P.; Bardy, J.; Bonnafond, C.; Bottollier-Curtet, H.; Devin, A.; Eyharts, P.; Eyl, P.; Gardelle, J.; Germain, G.; Grua, P.; Labrouche, J.; de Mascureau, J.; Le Taillandier, P.; Stadnikoff, W.; Thevenot, M.

    1991-07-01

    The purpose of the LELIA program developed at CESTA is to acquire the knowledge on induction accelerator technology for high peak power FEL applications. In a first step we study basic technology: (1) A high voltage pulse generator (150 kV, 60 ns, 2 ω) has been designed to drive the induction injector and the accelerating cells. It is able to work at high repetition rate (typically 1 kHz) by the use of magnetic switches. A flat top of 130 kV with {ΔV}/{V} = ±0.8% has been obtained for about 50 ns. (2) An induction cell prototype has been built in order to check technological choices (vacuum, mechanics, magnetic guiding, voltage supply, etc.) for injector and accelerating modules. (3) The injector geometry is being studied using Euphrosyne (a classical intense relativistic electron beam device) which consists of a concave thermo-ionic oxide cathode, an intermediate electrode and a hollow anode with a magnetic guiding channel. This diode delivers an electron beam between 1 and 3 MV, about 1 kA and a flat top pulse during 20 ns. We will carry on the injector studies with our induction injector LELIA I (1.5 MV, 1.5 kA, 1 kHz) which will be available at the end of 1990. An accelerating module is also being designed, taking into account guiding and stability problems. All these points are described in more detail in a poster paper [J. Bardy et al., these Proceedings (12th Int. FEL Conf., Paris, France, 1990) Nucl. Instr. and Meth. A304 (1991) 311]. The main goal is to build a 10 MV, 1-3 kA, 1 kHz induction accelerator and to have it running at CESTA in 1993. On the other hand, we want to use the electron beam provided by Euphrosyne then in LELIA I to perform FEL experiments at 35 GHz using a bifilar helical wiggler [H. Bottollier-Curtet et al., these Proceedings, p. 197].

  3. Undulators to FELs: Nanometers, Femtoseconds, Coherence and Applications

    SciTech Connect

    Attwood, David

    2011-11-30

    For scientists in many fields, from material science to the life sciences and archeology, synchrotron radiation, and in particular undulator radiation, has provide an intense source of x-rays which are tunable to the absorption edges of particular elements of interest, often permitting studies at high spatial and spectral resolution. Now a close cousin to the undulator, the x-ray free electron laser (XFEL) has emerged with improved spatial coherence and, perhaps more importantly, femtosecond pulse durations which permit dynamical studies. In the future attosecond x-ray capabilities are anticipated. In this colloqium we will describe some state of the art undulator studies, how undulators work, the evolution to FELs, their pulse and coherence properties, and the types of experiments envisioned.

  4. FEL gain optimisation and spontaneous radiation

    SciTech Connect

    Bali, L.M.; Srivastava, A.; Pandya, T.P.

    1995-12-31

    Colson have evaluated FEL gains for small deviations from perfect electron beam injection, with radiation of the same polarisation as that of the wiggler fields. We find that for optimum gain the polarisation of the optical field should be the same as that of the spontaneous emission under these conditions. With a helical wiggler the axial oscillations resulting from small departures from perfect electron beam injection lead to injection dependent unequal amplitudes and phases of the spontaneous radiation in the two transverse directions. Viewed along the axis therefore the spontaneous emission is elliptically polarised. The azimuth of the ellipse varies with the difference of phase of the two transverse components of spontaneous emission but the eccentricity remains the same. With planar wigglers the spontaneous emission viewed in the axial direction is linearly polarised, again with an injection dependent azimuth. For optimum coherent gain of a radiation field its polarisation characteristics must be the same as those of the spontaneous radiation with both types of wiggler. Thus, with a helical wiggler and the data reported earlier, an increase of 10% in the FEL gain at the fundamental frequency and of 11% at the fifth harmonic has been calculated in the small gain per pass limit. Larger enhancements in gain may result from more favourable values of input parameters.

  5. The GALAXIE all-optical FEL project

    SciTech Connect

    Rosenzweig, J. B.; Arab, E.; Andonian, G.; Cahill, A.; Fitzmorris, K.; Fukusawa, A.; Hoang, P.; Jovanovic, I.; Marcus, G.; Marinelli, A.; Murokh, A.; Musumeci, P.; Naranjo, B.; O'Shea, B.; O'Shea, F.; Ovodenko, A.; Pogorelsky, I.; Putterman, S.; Roberts, K.; Shumail, M.; and others

    2012-12-21

    We describe a comprehensive project, funded under the DARPA AXiS program, to develop an all-optical table-top X-ray FEL based on dielectric acceleration and electromagnetic undulators, yielding a compact source of coherent X-rays for medical and related applications. The compactness of this source demands that high field (>GV/m) acceleration and undulation-inducing fields be employed, thus giving rise to the project's acronym: GV/m AcceLerator And X-ray Integrated Experiment (GALAXIE). There are numerous physics and technical hurdles to surmount in this ambitious scenario, and the integrated solutions include: a biharmonic photonic TW structure, 200 micron wavelength electromagnetic undulators, 5 {mu}m laser development, ultra-high brightness magnetized/asymmetric emittance electron beam generation, and SASE FEL operation. We describe the overall design philosophy of the project, the innovative approaches to addressing the challenges presented by the design, and the significant progress towards realization of these approaches in the nine months since project initialization.

  6. SUPERSTRUCTURES FOR HIGH CURRENT FEL APPLICATION

    SciTech Connect

    Jacek Sekutowicz; Kevin Beard; Peter Kneisel; Genfa Wu; Catherine Thomas; Zheng

    2003-05-01

    The next generations of FELs at TJNAF will produce coherent light at power levels of 10 kW and 100 kW, respectively [1]. To achieve these power levels, 200 MeV electron beams of 10 mA and 100 mA have to be accelerated in the linear accelerators of the devices. The accelerators will be based on superconducting technology. Stable operation of these machines is only possible if the cavity Higher Order Modes (HOM) excited by the beams can sufficiently be damped. One of the possible accelerating structures which can fulfill this requirement, is a superstructure (SST) made of two weakly coupled subunits and equipped with appropriate HOM couplers. Based on the positive experience at DESY with 1.3 GHz superstructures, we are investigating for possible use similar structures in the linacs for the FEL upgrades. We have built a copper model of the proposed superstructure, based on two copper models of the 5-cell CEBAF cavities. This contribution presents measured results on this model. We are now in the process of fabrication a Nb prototype and hope to perform its cold test by the end of this year.

  7. Gender differences in postpartum depression: a longitudinal cohort study

    PubMed Central

    Artazcoz, Lucía

    2010-01-01

    Background The course of depression from pregnancy to 1 year post partum and risk factors among mothers and fathers are not known. Aims (1) To report the longitudinal patterns of depression from the third trimester of pregnancy to 1 year after childbirth; (2) to determine the gender differences between women and their partners in the effect of psychosocial and personal factors on postpartum depression. Methods A longitudinal cohort study was carried out over a consecutive sample of 769 women in their third trimester of pregnancy and their partners attending the prenatal programme in the Valencian Community (Spain) and follow-up at 3 and 12 months post partum. The outcome variable was the presence of depression at 3 or 12 months post partum measured by the Edinburgh Postnatal Depression Scale. Predictor variables were: psychosocial (marital dissatisfaction, confidant and affective social support) and personal (history of depression, partner's depression and negative life events, depression during the third trimester of pregnancy) variables. Logistic regression models were fitted via generalised estimating equations. Results At 3 and 12 months post partum, 9.3% and 4.4% of mothers and 3.4% and 4.0% of fathers, respectively, were newly diagnosed as having depression. Low marital satisfaction, partner's depression and depression during pregnancy increased the probability of depression during the first 12 months after birth in mothers and fathers. Negative life events increased the risk of depression only among mothers. Conclusions Psychosocial and personal factors were strong predictors of depression during the first 12 months post partum for both mothers and fathers. PMID:20515899

  8. A helical optical for circular polarized UV-FEL project at the UVSOR

    SciTech Connect

    Hama, Hiroyuki

    1995-12-31

    Most of existing storage ring free electron lasers (SRFEL) are restricted those performances by degradation of mirrors in optical cavities. In general, the SRFEL gain at the short wavelength region with high energy electrons is quite low, and the high reflectivity mirrors such as dielectric multilayer mirrors are therefore required. The mirror degradation is considered as a result of irradiation of higher harmonic photons that are simultaneously emitted from planar optical klystron (OK) type undulators, which are commonly used in SRFEL. This problem is getting severer as the lasing wavelength becomes shorter. The UVSOR-FEL had been originally scheduled to be shutdown by 1996 because another undulator project for spectroscopic studies with circular polarized photon would take the FEL`s place. According to suggestion of the insertion device group of the SPring-8, we have designed a helical undulator that is able to vary degree and direction of the polarization easily. In addition, the undulator can be converted into a helical OK by replacing magnets at the center part of undulator in order to coexist with further FEL experiments. Using a calculated magnetic field for magnet configurations of the OK mode, the radiation spectrum at wide wavelength range was simulated by a Fourier transform of Lienard-Wiechert potentials. As a matter of course, some higher harmonics are radiated on the off-axis angle. However it was found out that the higher harmonics is almost negligible as far as inside a solid angle of the Gaussian laser mode. Moreover the gain at the UV region of 250 nm is expected to be much higher than our present FEL because of high brilliant fundamental radiation. The calculated spatial distribution of higher harmonics and the estimated instantaneous gain is presented. Advantages of the helical OK for SRFEL will be discussed in view of our experience, and a possibility of application two-color experiment with SR will be also mentioned.

  9. ECH by FEL and gyrotron sources on the Microwave Tokamak Experiment (MTX) tokamak

    SciTech Connect

    Stallard, B.W.; Turner, W.C.; Allen, S.L.; Byers, J.A.; Felker, B.; Fenstermacher, M.E.; Ferguson, S.W.; Hooper, E.G.; Thomassen, K.I.; Throop, A.L. ); Makowski, M.A. )

    1990-08-09

    The Microwave Tokamak Experiment (MTX) at LLNL is studying the physics of intense pulse ECH is a high-density tokamak plasma using a microwave FEL. Related technology development includes the FEL, a windowless quasi-optical transmission system, and other microwave components. Initial plasma experiments have been carried out at 140 GHz with single rf pulses generated using the ETA-II accelerator and the ELF wiggler. Peak power levels up to 0.2 GW and pulse durations up to 10 ns were achieved for injection into the plasma using as untapered wiggler. FEL pulses were transmitted over 33 m from the FEL to MTX using six mirrors mounted in a 50-cm-diam evacuated pipe. Measurements of the microwave beam and transmission through the plasma were carried out. For future rapid pulse experiments at high average power (4 GW peak power, 5kHz pulse rate, and {bar P} > 0.5 MW) using the IMP wiggler with tapered magnetic field, a gyrotron (140 GHz, 400 kW cw or up to 1 MW short pulse) is being installed to drive the FEL input or to directly heat the tokamak plasma at full gyrotron power. Quasi-optic techniques will be used to couple the gyrotron power. For direct plasma heating, the gyrotron will couple into the existing mirror transport system. Using both sources of rf generation, experiments are planned to investigate intense pulse absorption and tokamak physics, such as the ECH of a pellet-fueled plasma and plasma control using localized heating. 12 refs., 9 figs.

  10. The role of radiation reaction in Lienard-Wiechert description of FEL interaction

    SciTech Connect

    Kimel, I.; Elias, L.R.

    1995-12-31

    The most common theoretical analysis of the FEL interaction is based on the set of equations consisting of Lorentz and wave equations. This approach explains most of FEL features and, in particular, works well to describe operation in the amplifier mode. In that approach however, there are some difficulties in describing operation in oscillator mode, as well as self amplified spontaneous emission. In particular, it is not possible to describe the start up stage since there is no wave to start with. It is clear that a different approach is required in such situations. That is why we have pursued the study of the FEL interaction in the framework of Lorentz plus Lienard-Wiechert equations. The Lienard-Wiechert Lorentz equation approach however, presents its own set of problems. Variation in energy of the electrons is given exclusively by the Lorentz equation. Thus, the energy lost due to the radiation process is not properly taken into account. This, of course, is a long standing problem in classical electrodynamics. In order to restore energy conservation radiation reaction has to be incorporated into the framework. The first question in that regard has to do with which form of the radiation reaction equations is the most convenient for computations in the FEL process. This has to do with the fact that historically, radiation reaction has been added in an ad hoc manner instead of being derived from the fundamental equations. Another problem discussed is how to take into account the radiation reaction in a collective manner in the interaction among electrons. Also discussed is the radiation reaction vis a vi the coherence properties of the FEL process.

  11. Amplification of current density modulation in a FEL with an infinite electron beam

    SciTech Connect

    Wang, G.; Litvinenko, V.N.; Webb, S.D.

    2011-03-28

    We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with {kappa}-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain. In developing an analytical model for a FEL-based coherent electron cooling system, an infinite electron beam has been assumed for the modulation and correction processes. While the assumption has its limitation, it allows for an analytical close form solution to be obtained, which is essential for investigating the underlying scaling law, benchmarking the simulation codes and understanding the fundamental physics. 1D theory was previously applied to model a CeC FEL amplifier. However, the theory ignores diffraction effects and does not provide the transverse profile of the amplified electron density modulation. On the other hand, 3D theories developed for a finite electron beam usually have solutions expanded over infinite number of modes determined by the specific transverse boundary conditions. Unless the mode with the largest growth rate substantially dominates other modes, both evaluation and extracting scaling laws can be complicated. Furthermore, it is also preferable to have an analytical FEL model with assumptions consistent with the other two sections of a CeC system. Recently, we developed the FEL theory in an infinitely wide electron beam with {kappa}-1 (Lorentzian) energy distribution. Close form solutions have been obtained for the amplified current modulation initiated by an external electric field with various spatial-profiles. In this work, we extend the theory into {kappa}-2 energy distribution and study the evolution of current density induced by an initial density modulation.

  12. ECH by FEL and gyrotron sources on the Microwave Tokamak Experiment (MTX) tokamak

    NASA Astrophysics Data System (ADS)

    Stallard, B. W.; Turner, W. C.; Allen, S. L.; Byers, J. A.; Felker, B.; Fenstermacher, M. E.; Ferguson, S. W.; Hooper, E. G.; Thomassen, K. I.; Throop, A. L.

    1990-08-01

    The Microwave Tokamak Experiment (MTX) at LLNL is studying the physics of intense pulse ECH is a high-density tokamak plasma using a microwave FEL. Related technology development includes the FEL, a windowless quasi-optical transmission system, and other microwave components. Initial plasma experiments have been carried out at 140 GHz with single RF pulses generated using the ETA-2 accelerator and the ELF wiggler. Peak power levels up to 0.2 GW and pulse durations up to 10 ns were achieved for injection into the plasma using as untapered wiggler. FEL pulses were transmitted over 33 m from the FEL to MTX using six mirrors mounted in a 50 cm diam evacuated pipe. Measurements of the microwave beam and transmission through the plasma were carried out. For future rapid pulse experiments at high average power (4 GW peak power, 5 kHz pulse rate, and bar P is greater than 0.5 MW) using the IMP wiggler with tapered magnetic field, a gyrotron (140 GHz, 400 kW CW or up to 1 MW short pulse) is being installed to drive the FEL input or to directly heat the tokamak plasma at full gyrotron power. Quasi-optic techniques will be used to couple the gyrotron power. For direct plasma heating, the gyrotron will couple into the existing mirror transport system. Using both sources of RF generation, experiments are planned to investigate intense pulse absorption and tokamak physics, such as the ECH of a pellet-fueled plasma and plasma control using localized heating.

  13. An Investigation into Using National Longitudinal Studies to Examine Trends in Educational Attainment and Development

    ERIC Educational Resources Information Center

    McNiece, Rosie; Bidgood, Penelope; Soan, Peter

    2004-01-01

    Longitudinal studies can provide individual histories of educational attainment and are becoming widely used in educational research. Two national longitudinal studies, the National Child Development Study (NCDS) and the British Cohort Study of 1970 (BCS70), are used here to investigate changing trends in the educational attainment of children in…

  14. Longitudinal trajectories of arterial stiffness and the role of blood pressure: the Baltimore Longitudinal Study of Aging.

    PubMed

    AlGhatrif, Majd; Strait, James B; Morrell, Chris H; Canepa, Marco; Wright, Jeanette; Elango, Palchamy; Scuteri, Angelo; Najjar, Samer S; Ferrucci, Luigi; Lakatta, Edward G

    2013-11-01

    Carotid-femoral pulse wave velocity (PWV), a marker of arterial stiffness, is an established independent cardiovascular risk factor. Little information is available on the pattern and determinants of the longitudinal change in PWV with aging. Such information is crucial to elucidating mechanisms underlying arterial stiffness and the design of interventions to retard it. Between 1988 and 2013, we collected 2 to 9 serial measures of PWV in 354 men and 423 women of the Baltimore Longitudinal Study of Aging, who were 21 to 94 years of age and free of clinically significant cardiovascular disease. Rates of PWV increase accelerated with advancing age in men more than women, leading to sex differences in PWV after the age of 50 years. In both sexes, not only systolic blood pressure (SBP) ≥140 mm Hg but also SBP of 120 to 139 mm Hg was associated with steeper rates of PWV increase compared with SBP<120 mm Hg. Furthermore, there was a dose-dependent effect of SBP in men with marked acceleration in PWV rate of increase with age at SBP ≥140 mm Hg compared with SBP of 120 to 139 mm Hg. Except for waist circumference in women, no other traditional cardiovascular risk factors predicted longitudinal PWV increase. In conclusion, the steeper longitudinal increase of PWV in men than women led to the sex difference that expanded with advancing age. Age and SBP are the main longitudinal determinants of PWV, and the effect of SBP on PWV trajectories exists even in the prehypertensive range.

  15. Spontaneous emission effects in optically pumped x-ray FEL

    SciTech Connect

    Smetanin, I.V.; Grigor`ev, S.V.

    1995-12-31

    An effect of spontaneous emission in both quantum and classical regimes of the optically pumped X-ray free electron laser (FEL) in investigated. The quantum properties of an FEL are determined by the ratio of the separation {h_bar} between the absorption and emission lines (i.e. the quanta emitted) and their effective width {Delta}{epsilon} {eta}={h_bar}/{Delta}{epsilon}. In the conventional classical regime {eta} {much_lt} 1 an electron emits and absorbes a great number of shortwavelength photons over the interaction region, the gain in FEL being the result of these competitive processes. In the quantum limit {eta} {much_gt} 1 the emission and absorption lines are completely separated and thus the FEL becomes a two-level quantum oscillator with a completely inverted active medium. Spontaneous emission causes the electron to leave the range of energies where resonant interaction with the laser field occurs, thus effectively reducing the number of particles that take part in generating the induced X-ray signal. This effect is found to be crucial for lasing in optically pumped X-ray FEL. The characteristic relaxation times are calculated for both classical and quantum FEL regimes. It is shown that spontaneous emission results in FEL electron beam threshold current, which is of rather high value. An optimal range of pumping laser intensities is determined.

  16. Optics-free x-ray FEL oscillator

    SciTech Connect

    Litvinenko, V.N.; Hao, Y.; Kayran, D.; Trbojevic, D.

    2011-03-28

    There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the X-ray range, the spectra of SASE FELs remains rather wide ({approx}0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01%-0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.

  17. Optical alignment and tuning system for the HUST THz-FEL

    NASA Astrophysics Data System (ADS)

    Liu, Xu; Liu, Kaifeng; Qin, Bin; Tan, Ping; Fu, Qiang; Wang, Wei; Pei, Yuanji

    2016-11-01

    A compact FEL oscillator with a radiation wavelength of 30 - 100 μm is proposed by HUST and NSRL. The optical cavity is very sensitive to misalignment errors of the mirror, due to its near-concentric and symmetric structure. The magnetic axis of the undulator, the optical axis of the resonator, and the electron beam propagation axis must all be aligned with high precision for achieving saturated lasing. This paper introduces a high-precision, multi-degree-of-freedom controlled optical alignment system, which has the ability to align in the transverse and longitudinal directions. The alignment tolerances are given by theoretical analysis and numerical simulations with three-dimensional FEL code GENESIS and optical propagation code (OPC). To accomplish optical alignment, two auxiliary HeNe laser systems were introduced. By adjusting the HeNe laser beam spot on the wedge, the optical axis can be aligned to the magnetic axis, and the estimated errors meet the tolerances. Finally, the electron beam will be guided through the hole in the central wedge to complete the transverse alignment. The longitudinal alignment and tuning methods are also described.

  18. Chronic pain in multiple sclerosis: A 10-year longitudinal study.

    PubMed

    Young, Jamie; Amatya, Bhasker; Galea, Mary P; Khan, Fary

    2017-07-01

    Pain is a common symptom associated with multiple sclerosis (MS), and has lasting effects on an individual's functional capacity and quality of life. A wide range of prevalence rates of pain (between 23% and 90%)have been reported in MS and this is mainly due to the methodological differences amongst the studies such as variability in patient sources, method of sampling and the definition of pain used. Chronic pain in MS, defined as pain lasting for greater than 3-6 months, can have a significant impact on their biopsychosocial health, including negative impact on activities of daily living, relationships and social participation. The long-term course of MS-related pain and its impact in an Australian cohort over a 7-year period has been investigated earlier. The aim of this longitudinal study was to describe the impact of chronic pain, pain-related disability and carer burden in persons with MS over a 10-year period. The aim of this longitudinal study was to describe the impact of chronic pain, pain-related disability and carer burden in persons with MS over a 10-year period. This was a prospective longitudinal study conducted at the Rehabilitation Department of Royal Melbourne Hospital (RMH), a tertiary referral hospital in Victoria and Australia. The source of participants was from the RMH MS database and contains detailed MS patient information including demographic data, diagnosis details (using McDonald's criteria), pain characteristics. Structured face-face interviews and validated measures were used, which include the visual analogue scale (VAS); chronic pain grade (CPG); the assessment of quality of life (AQoL) and the carer strain index (CSI). The mean age of the participants (n=70) was 55.3 years and majority (70%) were female. The mean age of the participants (n=70) was 55.3 years and majority (70%) were female. The findings show that over time (10 years), participants report having greater bilateral bodily pain and greater description of pain as 'worse

  19. A 300-nm compact mm-wave linac FEL design

    SciTech Connect

    Nassiri, A.; Kustom, R.L.; Kang, Y.W.

    1995-12-31

    Microfabrication technology offers an alternative method for fabricating precision, miniature-size components suitable for use in accelerator physics and commercial applications. The original R&D work at Argonne, in collaboration with the University of Illinois at Chicago, has produced encouraging results in the area of rf accelerating structure design, optical and x-ray masks production, deep x-ray lithography (LIGA exposures), and precision structural alignments. In this paper we will present a design study for a compact single pass mm-linac FEL to produce short wavelength radiation. This system will consists of a photocathode rf gun operated at 30 GHz, a 50-MeV superconducting constant gradient structure operated at 60 GHz, and a microundulator with 1-mm period. Initial experimental results on a scale model rf gun and microundulator will be presented.

  20. EMITTANCE GROWTH IN THE FEL RF-GUN

    SciTech Connect

    Novokhatski, Alexander

    2002-08-20

    A high brightness and low emittance is of crucial importance for the SASE-FEL at the TESLA Test Facility. Therefore a Photo-RF-Gun has been installed as particle source. Numerical simulations with codes like ASTRA [1] and MAFIA [2] show that the space charge dominated processes inside the RF-Gun contribute significantly to the emittance. In this paper we present the results of detailed studies with MAFIA TS2 which clarify the effects resulting in emittance growth for space charge dominated beams. It is shown that the resulting emittance can be minimized by changing the laser parameters like pulse length and spot size on the cathode. Additionally we present the concept of slice emittances which allows a more precise prediction of the real transverse emittance achievable with an emittance compensation scheme.

  1. An analysis of the saturation of a high gain FEL

    SciTech Connect

    Gluckstern, R.L.; Okamoto, Hiromi . Dept. of Physics); Krinsky, S. )

    1992-12-01

    We study the saturated state of an untapered free electron laser in the Compton regime, arising after exponential amplification of an initial low level of radiation by an initially monoenergetic, unbunched electron beam. The saturated state of the FEL is described by oscillations about an equilibrium state. Using the two invariants of the motion, and certain assumptions motivated by computer simulations, we provide approximate analytic descriptions of the radiation field and electron distribution in the saturation regime. We first consider a one-dimensional approximation, and later extend our approach to treat an electron beam of finite radial extent. Of note is a result on the radiated power in the case of an electron beam with small radius.

  2. Longitudinal study of children with unilateral hearing loss

    PubMed Central

    Lieu, Judith E. C.; Tye-Murray, Nancy; Fu, Qiang

    2012-01-01

    Objective Children with unilateral hearing loss (UHL) have been found to have lower language scores, and increased rate of speech therapy, grade failures, or needing Individualized Education Plans (IEPs). The objective of this study was to determine whether language skills and educational performance improved or worsened over time in a cohort of children with UHL. Study Design Prospective longitudinal cohort study Methods Forty-six children with permanent UHL, ages 6 to 12 years, were studied using standardized cognitive, achievement, and language testing at yearly intervals for three years. Using standardized test scores allowed implicit comparison to norms established by national cross-sectional samples. Secondary outcomes included behavioral issues, IEPs, receipt of speech therapy, or teacher report of problems at school. Analysis utilized repeated measures ANOVA and multilevel random regression modeling. Results Several cognitive and language mean standardized scores increased over time. Possible predictors of increase with time included higher baseline cognitive levels and receipt of interventions through an IEP. However, standardized achievement scores and indicators of school performance did not show concomitant improvements. Rates of IEPs remained > 50% throughout, and rates of speech therapy were consistently about 20%. Conclusions Children with UHL demonstrated improvement in oral language and verbal IQ scores over time, but not improvements in school performance. Parents and teachers reported persistent behavioral problems and academic weaknesses or areas of concern in about 25%. The provision of IEPs for children with UHL, and acknowledging UHL as a hearing disability, may be an effective intervention to improve language skills over time. PMID:22865630

  3. MAOA, abuse exposure and antisocial behaviour: 30-year longitudinal study.

    PubMed

    Fergusson, David M; Boden, Joseph M; Horwood, L John; Miller, Allison L; Kennedy, Martin A

    2011-06-01

    Recent studies have raised issues concerning the replicability of gene × environment (G × E) interactions involving the monoamine oxidase A (MAOA) gene in moderating the associations between abuse or maltreatment exposure and antisocial behaviour. This study attempted to replicate the findings in this area using a 30-year longitudinal study that has strong resemblance to the original research cohort. To test the hypothesis that the presence of the low-activity MAOA genotype was associated with an increased response to abuse exposure. Participants were 398 males from the Christchurch Health and Development Study who had complete data on: MAOA promoter region variable number tandem repeat genotype; antisocial behaviour to age 30; and exposure to childhood sexual and physical abuse. Regression models were fitted to five antisocial behaviour outcomes (self-reported property offending; self-reported violent offending; convictions for property/violent offending; conduct problems; hostility) observed from age 16 to 30, using measures of childhood exposure to sexual and physical abuse. The analyses revealed consistent evidence of G × E interactions, with those having the low-activity MAOA variant and who were exposed to abuse in childhood being significantly more likely to report later offending, conduct problems and hostility. These interactions remained statistically significant after control for a range of potentially confounding factors. Findings for convictions data were somewhat weaker. The present findings add to the evidence suggesting that there is a stable G × E interaction involving MAOA, abuse exposure and antisocial behaviour across the life course.

  4. Natural history of alpha mannosidosis a longitudinal study

    PubMed Central

    2013-01-01

    Background Alpha-Mannosidosis is a rare lysosomal storage disorder, caused by the deficiency of the enzyme alpha-Mannosidase. Clinically it is characterized by hearing impairment, skeletal and neurological abnormalities and mental retardation. In order to characterize the clinical features and disease progression of patients affected by alpha-Mannosidosis, a survey study was conducted. 43 patients from 4 European countries participated in this longitudinal study. Age range of the participants was 3 to 42 years. For each patient a medical history, complete physical and neurological examination, joint range of motion and assessment of physical endurance and of lung function were completed. In addition, serum and urinary oligosaccharide levels were analysed. Methods In this multicenter longitudinal study clinical data of 43 alpha-Mannosidosis patients were collected. In addition to objective clinical measurements biochemical assays were performed. Results Data analysis revealed a wide spectrum of clinical presentation regarding the severity and disease progression. Most clinical abnormalities were observed in the musculoskeletal and neurological system. All patients showed mental retardation and hearing loss from early childhood. An impairment in physical endurance was revealed by the 6-minute walk and 3-minute stair stair climb tests. There was only slight progression of a few clinical findings: Psychiatric troubles in both groups essentially, and respiratory dysfunction under 18 years. The serum and urinary oligosaccharide levels were increased in all affected individuals and correlated well with the 6-minute walk and 3-minute stair climb test results. Conclusions This study confirms that alpha-Mannosidosis is a very heterogeneous disorder regarding both, disease severity and progression. As it has been shown that Mannosidosis patients are able to perform lung function tests and the 6MWT and stair-climb test, these clinical parameters apparently can be used as

  5. Dielectric Wakefield Accelerator to drive the future FEL Light Source.

    SciTech Connect

    Jing, C.; Power, J.; Zholents, A. )

    2011-04-20

    X-ray free-electron lasers (FELs) are expensive instruments and a large part of the cost of the entire facility is driven by the accelerator. Using a high-energy gain dielectric wake-field accelerator (DWA) instead of the conventional accelerator may provide a significant cost saving and reduction of the facility size. In this article, we investigate using a collinear dielectric wakefield accelerator to provide a high repetition rate, high current, high energy beam to drive a future FEL x-ray light source. As an initial case study, a {approx}100 MV/m loaded gradient, 850 GHz quartz dielectric based 2-stage, wakefield accelerator is proposed to generate a main electron beam of 8 GeV, 50 pC/bunch, {approx}1.2 kA of peak current, 10 x 10 kHz (10 beamlines) in just 100 meters with the fill factor and beam loading considered. This scheme provides 10 parallel main beams with one 100 kHz drive beam. A drive-to-main beam efficiency {approx}38.5% can be achieved with an advanced transformer ratio enhancement technique. rf power dissipation in the structure is only 5 W/cm{sup 2} in the high repetition rate, high gradient operation mode, which is in the range of advanced water cooling capability. Details of study presented in the article include the overall layout, the transform ratio enhancement scheme used to increase the drive to main beam efficiency, main wakefield linac design, cooling of the structure, etc.

  6. Stress Process of Illicit Drug Use among U.S. Immigrants' Adolescent Children: A Longitudinal Study

    ERIC Educational Resources Information Center

    Choo, Hyekyung

    2012-01-01

    This study examined a full path model of stress process for predicting illicit drug use among Asian and Latino immigrants' adolescent children. Using 2-year longitudinal data (National Longitudinal Study of Adolescent Health) from a sample of adolescents with Asian or Latino immigrant parents (N = 2,353), the study explored structural…

  7. Stress Process of Illicit Drug Use among U.S. Immigrants' Adolescent Children: A Longitudinal Study

    ERIC Educational Resources Information Center

    Choo, Hyekyung

    2012-01-01

    This study examined a full path model of stress process for predicting illicit drug use among Asian and Latino immigrants' adolescent children. Using 2-year longitudinal data (National Longitudinal Study of Adolescent Health) from a sample of adolescents with Asian or Latino immigrant parents (N = 2,353), the study explored structural…

  8. A longitudinal study of very young children's vowel production.

    PubMed

    McGowan, Rebecca W; McGowan, Richard S; Denny, Margaret; Nittrouer, Susan

    2014-02-01

    Ecologically realistic, spontaneous, adult-directed, longitudinal speech data of young children were described by acoustic analyses. The first 2 formant frequencies of vowels produced by 6 children from different American English dialect regions were analyzed from ages 18 to 48 months. The vowels were from largely conversational contexts and were classified according to dictionary pronunciation. Within-subject formant frequency variability remained relatively constant for the span of ages studied. It was often difficult to detect overall decreases in the first 2 formant frequencies between ages 30 and 48 months. A study of the movement of the corner vowels with respect to the vowel centroid showed that the shape of the vowel space remained qualitatively constant from 30 through 48 months. The shape of the vowel space is established early in life. Some aspects of regional dialect were observed in some of the subjects at 42 months of age. The present study adds to the existing data on the development of vowel spaces by describing ecologically realistic speech.

  9. A longitudinal study relating carpeting with sick building syndrome

    SciTech Connect

    Norbaeck, D.; Torgen, M. )

    1989-01-01

    A longitudinal questionnaire study was performed among personnel in two Swedish primary schools with wall-to-wall carpets and four schools with hard floor covering. The study groups consisted of all primary schools equipped with wall-to-wall carpets in the town of Uppsala, plus a random sample of two newer and two elderly primary schools with hard floor covering. In an initial cross-sectional study, the wall-to-wall carpet group reported an enhanced prevalence of eye and airway symptoms, face rashes, headache, abnormal tiredness and a sensation of being electrostatically charged in comparison with personnel in schools with hard floor covering. Since the enhanced prevalence of symptoms in the wall-to-wall carpets versus the hard floor covering group was also observed among persons without signs of atopy it was concluded that wall-to-wall carpets are not exclusively a problem for the sensitive atopic individual. The type of ventilation system (mechanical ventilation versus natural ventilation) had no significant effect on the symptom frequencies. After the removal of the wall-to-wall carpets, many of the reported symptoms decreased to a level similar to the group without previous or present exposure to such carpets. However, the frequency of airway symptoms remained enhanced among the wall-to-wall carpet group.

  10. Bone loss in chronic hemiplegia: a longitudinal cohort study.

    PubMed

    de Brito, Christina May Moran; Garcia, Ana Cristina Ferreira; Takayama, Liliam; Fregni, Felipe; Battistella, Linamara Rizzo; Pereira, Rosa Maria Rodrigues

    2013-01-01

    The purpose of this study was to evaluate hemiplegic stroke patients in terms of long-term changes in bone mineral density and related factors. We conducted a longitudinal cohort study, involving 57 first-stroke patients (40 males) with chronic hemiplegia (for more than 12mo), at a university rehabilitation center in the city of São Paulo, Brazil. Bone loss, body composition, lean mass, and fat mass were evaluated at 2 time points (mean interval, 16mo). Bone loss was significantly greater in paretic forearms than in nonparetic forearms (p=0.001) and in patients having suffered strokes more recently (p=0.015). We found no difference between paretic and nonparetic femurs. Femoral bone loss was significantly greater in patients using anticoagulants or anticonvulsants (p=0.025) and in those with greater spasticity (p=0.040), regardless of the time since stroke. Our results provide additional evidence that hemiplegic stroke patients have progressive bone loss and that such bone loss is more common in the arms than in the legs. Patients with poststroke hemiplegia should be densitometric monitored mainly in paretic arm and treated for bone loss, with attention to the determinants identified in this study. Copyright © 2013 The International Society for Clinical Densitometry. Published by Elsevier Inc. All rights reserved.

  11. Biochemical Markers of Aging for Longitudinal Studies in Humans

    PubMed Central

    Engelfriet, Peter M.; Jansen, Eugène H. J. M.; Picavet, H. Susan J.; Dollé, Martijn E. T.

    2013-01-01

    Much progress has been made in the past decades in unraveling the mechanisms that are responsible for aging. The discovery that particular gene mutations in experimental species such as yeast, flies, and nematodes are associated with longevity has led to many important insights into pathways that regulate aging processes. However, extrapolating laboratory findings in experimental species to knowledge that is valid for the complexity of human physiology remains a major challenge. Apart from the restricted experimental possibilities, studying aging in humans is further complicated by the development of various age-related diseases. The availability of a set of biomarkers that really reflect underlying aging processes would be of much value in disentangling age-associated pathology from specific aging mechanisms. In this review, we survey the literature to identify promising biochemical markers of aging, with a particular focus on using them in longitudinal studies of aging in humans that entail repeated measurements on easily obtainable material, such as blood samples. Our search strategy was a 2-pronged approach, one focused on general mechanisms of aging and one including studies on clinical biomarkers of age-related diseases. PMID:23382477

  12. Undergraduate nursing students' learning styles: a longitudinal study.

    PubMed

    Fleming, Sandra; McKee, Gabrielle; Huntley-Moore, Sylvia

    2011-07-01

    This paper reports on the main findings of a longitudinal study of the learning styles of one cohort of undergraduate pre-registration nursing students at an Irish university. The Honey and Mumford (2000a) Learning Styles Questionnaire was administered to a sample of students in their first (n=202) and final year of study (n=166), the final sample number (58) was based on matched pairs. The most common dominant learning style in first year was the dual learning category (35%) while a large proportion of the students (53%) in their final year had no dominant learning style. The preferred learning style of students in their first (69%) and final (57%) year was reflector. Learning styles were significantly different at the two time points and there was a significant relationship between some learning styles and students' age but not with academic achievement. Total scores of all learning styles showed significant improvements across the two time points of the study. An important implication for nurse education practice is the need for nurse educators to be aware of students' learning styles and in an attempt to maximise students' learning potential, utilise a range of teaching and learning methodologies and assessments that develop all learning styles.

  13. Data management in a longitudinal cross-cultural study.

    PubMed

    Roberts, R J; Musick, B S; Olley, B; Hall, K S; Hendrie, H C; Oyediran, A B

    The Indianapolis-Ibadan Dementia Project compares the rates of dementia at two sites, one in the U.S.A. and one in Nigeria. This paper concentrates on the data management issues in this longitudinal cross-cultural study. Approximately 2500 elderly people were recruited at each site, and continue to be re-assessed every two years. All the data are collected on paper and then entered into a FoxPro relational database. Most of the data management, including data cleaning, is done in Indianapolis. The design of the data collection forms is particularly important in a cross-cultural study, with the questions and the coding of responses clear and simple. Since Nigeria and the U.S.A. have different levels of technological development, the computer hardware and software were chosen to be suitable for use at either site. Exchange visits have been needed to address data management issues and resolve unexpected problems. The data management on cross-cultural studies can be handled successfully, given careful planning.

  14. [Changes in interpersonal values in student nurses: a longitudinal study].

    PubMed

    Nagata, H; Kondo, M; Ogawa, S

    1994-01-01

    Our cross-sectional studies of interpersonal values in female student nurses showed that (1) third graders attached more importance to the values of Support and Independence and less to those of Benevolence and Leadership than did first graders, and (2) the discrepancy between the ratings of what they were and those of what their ideal nurses were was greater in the third than in the first graders. We interpreted these differences between the two graders as indicating a developmental change brought about during the three years. This study examined the internal validity of this interpretation through the use of a longitudinal method. The KG-SIV (Kikuchi-Gordon Survey of Interpersonal Values) was administered twice to 85 female student nurses: immediately after entering their nursing schools and immediately before finishing them, with a testing interval of approximately three years. For each testing, subjects were asked to rate what they were and then what their ideal nurses were. Analyses produced almost the same results as obtained in cross-sectional studies: perceived values of Benevolence and Leadership decrease while those of Support and Independence increase over the three years, with the discrepancy increasing from the first to the second testing. Findings thus support the internal validity of our prior interpretation. The changes in interpersonal values found for the student nurses suggest a socialization process they undertake in nurse training and imply an increase of stress they experience in that process.

  15. High-power FEL design issues - a critical review

    SciTech Connect

    Litvinenko, V.N.; Madey, J.M.J.; O`Shea, P.G.

    1995-12-31

    The high-average power capability of FELs has been much advertised but little realized. In this paper we provide a critical analysis of the technological and economic issues associated with high-average power FEL operation from the UV to near IR. The project of IR FEL for the Siberian Center of photochemical researches is described. The distinguished features of this project are the use of the race-track microtron-recuperator and the {open_quotes}electron output of radiation{close_quotes}. The building for the machine is under reconstruction now. About half of hardware has been manufactured. The assembly of installation began.

  16. CEBAF UV/IR FEL subsystem testing and validation program

    SciTech Connect

    G.R. Neil; S.V. Benson; H.F. Dylla; H. Liu

    1995-01-01

    A design has been established for IR and UV FELs within the Laser Processing Consortium's (LPC) program for development and application of high-average-power FELs for materials processing. Hardware prototyping and testing for the IR portion of the system are underway. The driver portion has been designed based on the superconducting radio-frequency (SRF) technology now seeing large-scale application in the commissioning of CEBAF, the Continuous Electron Beam Accelerator Facility, where LPC activities are centered. As of July 1994, measurements of beam performance confirm SRF's benefits in beam quality and stability, which are applicable to high-average-power FELs.

  17. An overview of the design, implementation, and analyses of longitudinal studies on aging.

    PubMed

    Newman, Anne B

    2010-10-01

    Longitudinal studies have contributed substantially to understanding of aging and geriatric syndromes. These efforts have provided a base of knowledge of the critical factors to consider in designing and implementing new longitudinal studies in older adults. This review highlights some of the major considerations in planning and implementing this type of study. Longitudinal studies can assess change over time and specific disease endpoints. Such projects require multidisciplinary teams with expertise in the many health and contextual factors that must be considered. Recent advances in study design include the use of imaging and biomarkers to assess mechanisms and approaches that raise the ceiling on measurement and integrate assessment of exposures over time. Study implementation requires careful planning and monitoring to maintain fidelity to the scientific goals. Analysis of longitudinal data requires approaches that account for inevitable missing data. New studies should take advantage of the experience obtained from longitudinal studies on aging already conducted.

  18. Depression in medical students: insights from a longitudinal study.

    PubMed

    Silva, Vanessa; Costa, Patrício; Pereira, Inês; Faria, Ricardo; Salgueira, Ana P; Costa, Manuel J; Sousa, Nuno; Cerqueira, João J; Morgado, Pedro

    2017-10-10

    Factors associated with depression of medical students are poorly understood. The purpose of this study is to determine the prevalence of depression in medical students, its change during the course, if depression persists for affected students, what are the factors associated with depression and how these factors change over time. A prospective, longitudinal observational study was conducted at the Medical School of the University of Minho, Portugal, between academic years 2009-2010 to 2012-2013. We included students who maintained their participation by annually completing a questionnaire including Beck Depression Inventory (BDI). Anxiety and burnout were assessed using the State Trait Anxiety Inventory and Maslach Burnout Inventory. Surveys on socio-demographic variables were applied to evaluate potential predictors, personal and academic characteristics and perceived difficulties. ANOVA with multiple comparisons were used to compare means of BDI score. The medical students were organized into subgroups by K-means cluster analyses. ANOVA mixed-design repeated measurement was performed to assess a possible interaction between variables associated with depression. The response rate was 84, 92, 88 and 81% for academic years 2009-2010, 2010-2011,2011-2012 and 2012/2013, respectively. Two hundred thirty-eight medical students were evaluated longitudinally. For depression the prevalence ranged from 21.5 to 12.7% (academic years 2009/2010 and 2012/2013). BDI scores decreased during medical school. 19.7% of students recorded sustained high BDI over time. These students had high levels of trait-anxiety and choose medicine for anticipated income and prestige, reported more relationship issues, cynicism, and decreased satisfaction with social activities. Students with high BDI scores at initial evaluation with low levels of trait-anxiety and a primary interest in medicine as a career tended to improve their mood and reported reduced burnout, low perceived learning problems

  19. Natural course of behavioral addictions: a 5-year longitudinal study.

    PubMed

    Konkolÿ Thege, Barna; Woodin, Erica M; Hodgins, David C; Williams, Robert J

    2015-01-22

    Resolving the theoretical controversy on the labeling of an increasing number of excessive behaviors as behavioral addictions may also be facilitated by more empirical data on these behavioral problems. For instance, an essential issue to the classification of psychiatric disorders is information on their natural course. However, longitudinal research on the chronic vs. episodic nature of behavioral addictions is scarce. The aim of the present study, therefore, was to provide data on prevalence, substance use comorbidity, and five-year trajectories of six excessive behaviors-namely exercising, sexual behavior, shopping, online chatting, video gaming, and eating. Analyses were based on the data of the Quinte Longitudinal Study, where a cohort of 4,121 adults from Ontario, Canada was followed for 5 years (2006 to 2011). The response rate was 21.3%, while retention rate was 93.9%. To assess the occurrence of each problem behavior, a single self-diagnostic question asked people whether their over-involvement in the behavior had caused significant problems for them in the past 12 months. To assess the severity of each problem behavior reported, the Behavioral Addiction Measure was administered. A mixed design ANOVA was used to investigate symptom trajectories over time for each problem behavior and whether these symptom trajectories varied as a function of sex. The large majority of people reported having problematic over-involvement for just one of these behaviors and just in a single time period. A main effect of time was found for each problem behavior, indicating a moderately strong decrease in symptom severity across time. The time x sex interaction was insignificant in each model indicating that the decreasing trend is similar for males and females. The data also showed that help seeking was very low in the case of excessive sexual behavior, shopping, online chatting, and video gaming but substantially more prevalent in the case of excessive eating and

  20. Longitudinal study of children exposed to sulfur oxides

    SciTech Connect

    Dodge, R.; Solomon, P.; Moyers, J.; Hayes, C.

    1985-05-01

    This study is a longitudinal comparison of the health of children exposed to markedly different concentrations of sulfur dioxide and moderately different concentrations of particulate sulfate. The four groups of subjects lived in two areas of one smelter town and in two other towns, one of which was also a smelter town. In the area of highest pollution, children were intermittently exposed to high SO/sub 2/ levels (peak three-hour average concentration exceeded 2,500 micrograms/m3) and moderate particulate SO/sub 4/= levels (average concentration was 10.1 micrograms/m3). When the children were grouped by the four gradients of pollution observed, the prevalence of cough (measured by questionnaire) correlated significantly with pollution levels (trend chi-square = 5.6, p = 0.02). No significant differences in the incidence of cough or other symptoms occurred among the groups of subjects over three years, and pulmonary function and lung function growth over the study were roughly equal among all the groups. These results suggest that intermittent elevations in SO/sub 2/ concentration, in the presence of moderate particulate SO/sub 4/= concentration, produced evidence of bronchial irritation in the subjects, but no chronic effect on lung function or lung function growth was detected.

  1. A longitudinal study of very young children's vowel production

    PubMed Central

    McGowan, Rebecca W.; McGowan, Richard S.; Denny, Margaret; Nittrouer, Susan

    2014-01-01

    Purpose Ecologically realistic, spontaneous adult-directed longitudinal speech data of young children was described by acoustic analyses. Method The first two formant frequencies of vowels produced by six children from different American English dialect regions were analyzed from ages 18 to 48 months. The vowels were from largely conversational contexts and were classified according to dictionary pronunciation. Results Within-subject formant frequency variability remained relatively constant for the span of ages studied here. It was often difficult to detect overall decreases in the first two formant frequencies between the ages of 30 and 48 months. A study of the movement of the corner vowels with respect to the vowel centroid showed that the shape of the vowel space remained qualitatively constant from 30 through 48 months. Conclusions The shape of the vowel space is established early in life. Some aspects of regional dialect were observed in some of the subjects at 42 months of age. The present paper adds to the existing data on the development of vowel spaces by describing ecologically realistic speech. PMID:24687464

  2. Cardiovascular Health and Arterial Stiffness: The Maine Syracuse Longitudinal Study

    PubMed Central

    Crichton, Georgina E; Elias, Merrill F; Robbins, Michael A

    2014-01-01

    Ideal cardiovascular health is a recently defined construct by the American Heart Association (AHA) to promote cardiovascular disease reduction. Arterial stiffness is a major risk factor for cardiovascular disease. The extent to which the presence of multiple prevalent cardiovascular risk factors and health behaviors is associated with arterial stiffness is unknown. The aim of this study was to examine the association between the AHA construct of cardiovascular health and arterial stiffness, as indexed by pulse wave velocity and pulse pressure. The AHA health metrics, comprising of four health behaviors (smoking, body mass index, physical activity, and diet) and three health factors (total cholesterol, blood pressure, and fasting plasma glucose) were evaluated among 505 participants in the Maine-Syracuse Longitudinal Study. Outcome measures were carotid-femoral pulse wave velocity (PWV) and pulse pressure measured at 4 to 5-year follow-up. Better cardiovascular health, comprising both health factors and behaviors, was associated with lower arterial stiffness, as indexed by pulse wave velocity and pulse pressure. Those with at least five health metrics at ideal levels had significantly lower PWV (9.8 m/s) than those with two or less ideal health metrics (11.7 m/s) (P<0.001). This finding remained with the addition of demographic and PWV-related variables (P=0.004). PMID:24384629

  3. Cohort Profile: Longitudinal Study of Adult Health (ELSA-Brasil)

    PubMed Central

    Schmidt, Maria Inês; Duncan, Bruce B; Mill, José Geraldo; Lotufo, Paulo A; Chor, Dóra; Barreto, Sandhi Maria; Aquino, Estela ML; Passos, Valéria Maria Azeredo; Matos, Sheila MA; Molina, Maria del Carmen B; Carvalho, Marilia S; Bensenor, Isabela M

    2015-01-01

    Chronic diseases are a global problem, yet information on their determinants is generally scant in low- and middle-income countries. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) aims to contribute relevant information regarding the development and progression of clinical and subclinical chronic diseases, particularly cardiovascular diseases and diabetes, in one such setting. At Visit 1, we enrolled 15 105 civil servants from predefined universities or research institutes. Baseline assessment (2008–10) included detailed interviews and measurements to assess social and biological determinants of health, as well as various clinical and subclinical conditions related to diabetes, cardiovascular diseases and mental health. A second visit of interviews and examinations is under way (2012–14) to enrich the assessment of cohort exposures and to detect initial incident events. Annual surveillance has been conducted since 2009 for the ascertainment of incident events. Biological samples (sera, plasma, urine and DNA) obtained at both visits have been placed in long-term storage. Baseline data are available for analyses, and collaboration via specific research proposals directed to study investigators is welcome. PMID:24585730

  4. Race, ideology, and the tea party: a longitudinal study.

    PubMed

    Knowles, Eric D; Lowery, Brian S; Shulman, Elizabeth P; Schaumberg, Rebecca L

    2013-01-01

    The Tea Party movement, which rose to prominence in the United States after the election of President Barack Obama, provides an ideal context in which to examine the roles of racial concerns and ideology in politics. A three-wave longitudinal study tracked changes in White Americans' self-identification with the Tea Party, racial concerns (prejudice and racial identification), and ideologies (libertarianism and social conservatism) over nine months. Latent Growth Modeling (LGM) was used to evaluate potential causal relationships between Tea Party identification and these factors. Across time points, racial prejudice was indirectly associated with movement identification through Whites' assertions of national decline. Although initial levels of White identity did not predict change in Tea Party identification, initial levels of Tea Party identification predicted increases in White identity over the study period. Across the three assessments, support for the Tea Party fell among libertarians, but rose among social conservatives. Results are discussed in terms of legitimation theories of prejudice, the "racializing" power of political judgments, and the ideological dynamics of the Tea Party.

  5. Training Kentuckians for industrial jobs: a longitudinal study

    SciTech Connect

    Weseman, M.; Preston-Anderson, A.

    1982-09-01

    The Training and Technology (TAT) program, operated by Oak Ridge Associated Universities (ORAU) and Union Carbide Corporation, Nuclear Division, in a Department of Energy facility, has trained unemployed Kentuckians for a number of years. The program is part of DOE's continuing effort to help supply trained personnel for the energy industry. During fiscal years 1978 to 1980, the period covered in this study, TAT enrolled 192 Kentuckians under CETA, Balance of State, and Governor's Special Grants contracts with the Department for Human Resources. One hundred sixty-seven (87%) of these participants completed the program, of which 154 (92%) were placed in unsubsidized employment. Average hourly wage rates for the 154 graduates placed in unsubsidized employment were as follows: FY 1980 - $6.05; FY 1979 - $4.94; and FY 1978 - $4.97. These data indicate short-term success but do not address the questions of postprogram employment stability and wage increases over time. In order to assess the long term impact of TAT, ORAU has conducted a longitudinal study of participants' employment experiences after training.

  6. Training Tennesseans for industrial jobs: a longitudinal study

    SciTech Connect

    Weseman, M.; Preston-Anderson, A.

    1982-09-01

    The Training and Technology (TAT) program is operated for the US Department of Energy by Oak Ridge Associated Universities (ORAU) and Union Carbide Corporation, Nuclear Division, in a Department of Energy facility. The program is part of the Department's continuing efforts to help supply trained personnel for the energy industry. TAT has trained unemployed economically disadvantaged Tennesseans for 16 years. During fiscal years 1978 to 1980, the period covered in this study, TAT enrolled 460 Tennesseans under CETA, Title 2B contracts with the Department of Employment Security. Three hundred sixty (78%) of these participants completed the program, of which 335 (93%) were placed in unsubsidized employment. Average hourly wage rates for the 335 graduates placed in unsubsidized employment were as follows: FY 1980 - $6.32; FY 1979 - $5.12; FY 1978 - $5.71. These data indicate short-term success but do not address the questions of postprogram employment stability and wage increases over time. In order to assess the long-term impact of TAT, ORAU has conducted a longitudinal study of participants' employment experiences after training.

  7. Whole grain intake: The Baltimore Longitudinal Study of Aging.

    PubMed

    Maras, Janice E; Newby, P K; Bakun, Peter J; Ferrucci, Luigi; Tucker, Katherine L

    2009-02-01

    Our objective was to identify major dietary sources of whole grains and to describe the construction of a database of whole grain content of foods. Dietary information was collected with 7-d food records from men and women in the Baltimore Longitudinal Study of Aging, mean age 62.1 +/- 16.0 years, who participated in the dietary assessment portion of the study (n = 1516), and estimates of whole grain intake were obtained from a newly developed database. The Pyramid Servings database and 1994-1996 Continuing Survey of Food Intakes by Individuals (CSFII) recipe ingredients database were then used to calculate both servings and gram weights of whole grain intakes. Mean intakes of whole grains, refined grains, and total grains, as well as frequency of intake for major whole grain food groups and whole grain content for each group, were calculated. Top contributors of whole grains were ready-to-eat breakfast cereals (made with whole grain as well as bran), hot breakfast cereals (made with whole grain), multi-grain bread, and whole wheat bread. While more research is needed to better understand the benefits of whole grains, the development of research tools, including databases to accurately assess whole grain intake, is a critical step in completing such research.

  8. Whole grain intake: The Baltimore Longitudinal Study of Aging

    PubMed Central

    Maras, Janice E.; Newby, P.K.; Bakun, Peter J.; Ferrucci, Luigi; Tucker, Katherine L.

    2009-01-01

    Our objective was to identify major dietary sources of whole grains and to describe the construction of a database of whole grain content of foods. Dietary information was collected with 7-d food records from men and women in the Baltimore Longitudinal Study of Aging, mean age 62.1 ± 16.0 years, who participated in the dietary assessment portion of the study (n = 1516), and estimates of whole grain intake were obtained from a newly developed database. The Pyramid Servings database and 1994–1996 Continuing Survey of Food Intakes by Individuals (CSFII) recipe ingredients database were then used to calculate both servings and gram weights of whole grain intakes. Mean intakes of whole grains, refined grains, and total grains, as well as frequency of intake for major whole grain food groups and whole grain content for each group, were calculated. Top contributors of whole grains were ready-to-eat breakfast cereals (made with whole grain as well as bran), hot breakfast cereals (made with whole grain), multi-grain bread, and whole wheat bread. While more research is needed to better understand the benefits of whole grains, the development of research tools, including databases to accurately assess whole grain intake, is a critical step in completing such research. PMID:20126297

  9. Interpersonal social responsibility model of service learning: A longitudinal study.

    PubMed

    Lahav, Orit; Daniely, Noa; Yalon-Chamovitz, Shira

    2017-06-02

    Service-learning (SL) is commonly used in Occupational Therapy (OT) programs worldwide as a community placement educational strategy. However, most SL models are not clearly defined in terms of both methodology and learning outcomes. This longitudinal study explores a structured model of Service-Learning (Interpersonal Social Responsibility-Service Learning: ISR-SL) aimed towards the development of professional identity among OT students. Based on OT students experiences from the end of the course through later stages as mature students and professionals. A qualitative research design was used to explore the perceptions and experiences of 150 first, second, and third-year OT students and graduates who have participated in ISR-SL during their first academic year. Our findings suggest that the structured, long-term relationship with a person with a disability in the natural environment, which is the core of the ISR-SL, allowed students to develop a professional identity based on seeing the person as a whole and recognizing his/her centrality in the therapeutic relationship. This study suggests ISR-SL as future direction or next step for implementing SL in OT and other healthcare disciplines programs.

  10. A Systematic Review of Longitudinal Studies of Mathematics Difficulty.

    PubMed

    Nelson, Gena; Powell, Sarah R

    2017-06-01

    Some students may be diagnosed with a learning disability in mathematics or dyscalculia, whereas other students may demonstrate below-grade-level mathematics performance without a disability diagnosis. In the literature, researchers often identify students in both groups as experiencing math difficulty. To understand the performance of students with math difficulty, we examined 35 studies that reported longitudinal results of mathematics achievement (i.e., mathematics performance measured across at least a 12-month span). Our primary goal was to conduct a systematic review of these studies and to understand whether the growth of students with math difficulty was comparable or stagnant when compared with that of students without math difficulty. We also analyzed whether identification of math difficulty was predictive of mathematics achievement in later grades and whether a diagnosis of math difficulty was stable across grade levels. Results indicate that students with math difficulty demonstrate growth on mathematics measures, but this growth still leads to lower performance than that of students without math difficulty. Identification of math difficulty is strongly related to math performance in subsequent grades, and this diagnosis is often stable. Collectively, this literature indicates that students with math difficulty continue to struggle with mathematics in later grades.

  11. Heritability of Delay Discounting in Adolescence: A Longitudinal Twin Study

    PubMed Central

    Golosheykin, Simon; Grant, Julia D.; Heath, Andrew C.

    2010-01-01

    Delay discounting (DD) refers to the preference for smaller immediate rewards over larger but delayed rewards, and is considered to be a distinct component of a broader “impulsivity” construct. Although greater propensity for discounting the value of delayed gratification has been associated with a range of problem behaviors and substance abuse, particularly in adolescents, the origins of individual differences in DD remain unclear. We examined genetic and environmental influences on a real-life behavioral measure of DD using a longitudinal twin design. Adolescent participants were asked to choose between a smaller ($7) reward available immediately and a larger ($10) reward to be received in 7 days. Biometrical genetic analysis using linear structural equation modeling showed significant heritability of DD at ages 12 and 14 (30 and 51%, respectively) and suggested that the same genetic factors influenced the trait at both ages. DD was significantly associated with symptoms of conduct disorder, attention deficit hyperactivity disorder, substance use, and with higher novelty seeking and poor self-regulation. This study provides the first evidence for heritability of DD in humans and suggests that DD can be a promising endophenotype for genetic studies of addiction and externalizing disorders. PMID:20700643

  12. Intellectual development in Noonan syndrome: a longitudinal study.

    PubMed

    Roelofs, Renée L; Janssen, Nikki; Wingbermühle, Ellen; Kessels, Roy P C; Egger, Jos I M

    2016-07-01

    Although cognitive impairments in adults with Noonan syndrome seem to be limited to a low-average intelligence and slower processing speed, studies in children with Noonan syndrome have demonstrated more extensive cognitive problems. These include deficits in language skills, memory, attention, and executive functioning. This longitudinal study is the first to investigate intellectual development in a group of individuals with Noonan syndrome. Sixteen patients with Noonan syndrome underwent intelligence assessment both in childhood and in adulthood, using Wechsler's intelligence scales. IQ scores and Wechsler standard scores achieved in childhood and adulthood were compared. Subsequently, verbal and performance IQ in childhood were used as predictors for adult IQ and index scores. Compared with childhood scores, adult full-scale IQ and performance IQ significantly increased. Adult performance IQ was higher than verbal IQ. Childhood performance IQ and verbal IQ together predicted all adult IQ and index scores, except for the processing speed index. Childhood IQ was a significant predictor of adult intelligence in patients with Noonan syndrome. Performance IQ advanced to a normal level in adulthood, while verbal IQ did not develop proportionately, resulting in a discrepancy between adult performance IQ and verbal IQ. This finding could suggest a delay in the development of executive functioning in patients with Noonan syndrome, which seems to be outgrown in adulthood.

  13. Multiproject interdependencies in health systems management: a longitudinal qualitative study.

    PubMed

    Spaulding, Aaron; Gamm, Larry; Kim, Jungyeon; Menser, Terri

    2014-01-01

    A health care organization often engages in the simultaneous implementation of multiple organization change initiatives. However, the degree to which these initiatives are implemented and can be enhanced based on their interdependencies is an open question. How organizations and the change initiatives they pursue might benefit from more careful examination of potential interdependencies among projects was explored in this article. The aim of this study was to introduce a multiproject management conceptualization that stresses project interdependencies and suggests synergies can be found to enhance overall project and organizational performance. It examines this conceptualization in the context of a health system pursuing several major initiatives to capture insights into the nature of such interdependencies. Longitudinal qualitative analysis of interviews conducted with hospital leaders attempting to manage multiple initiatives being implemented by the system's leadership team was used in this study. The implementation of an electronic medical record (EMR) is empirically identified as the most central among multiple projects based on other projects dependencies on the EMR. Furthermore, concerns for data are identified most frequently as success factors across all projects. This reinforces the depiction of the EMR as a central organizational focus. A unique perspective on multiproject management in hospitals and on EMR projects is presented. In addition, the interdependency conceptualization and its application and results provide insights into multiproject management that can help ensure that benefits of individual projects are more fully optimized or exploited in leveraging the effectiveness of other project initiatives.

  14. Race, Ideology, and the Tea Party: A Longitudinal Study

    PubMed Central

    Knowles, Eric D.; Lowery, Brian S.; Shulman, Elizabeth P.; Schaumberg, Rebecca L.

    2013-01-01

    The Tea Party movement, which rose to prominence in the United States after the election of President Barack Obama, provides an ideal context in which to examine the roles of racial concerns and ideology in politics. A three-wave longitudinal study tracked changes in White Americans’ self-identification with the Tea Party, racial concerns (prejudice and racial identification), and ideologies (libertarianism and social conservatism) over nine months. Latent Growth Modeling (LGM) was used to evaluate potential causal relationships between Tea Party identification and these factors. Across time points, racial prejudice was indirectly associated with movement identification through Whites’ assertions of national decline. Although initial levels of White identity did not predict change in Tea Party identification, initial levels of Tea Party identification predicted increases in White identity over the study period. Across the three assessments, support for the Tea Party fell among libertarians, but rose among social conservatives. Results are discussed in terms of legitimation theories of prejudice, the “racializing” power of political judgments, and the ideological dynamics of the Tea Party. PMID:23825630

  15. Longitudinal relationships between nutritional status, body composition, and physical fitness in rural children of South Africa: The Ellisras longitudinal study.

    PubMed

    Monyeki, M Andries; Koppes, Lando L J; Monyeki, K Dan; Kemper, Han C G; Twisk, Jos W R

    2007-01-01

    The objective of this study was to investigate the development and tracking of nutritional status, body composition and physical fitness, and the longitudinal relationship of changes in nutritional status, and body composition with changes in physical fitness over a 1-year period of follow-up. Studied were 380 boys and 322 girls aged 7-14 years from the Ellisras Longitudinal Study. Boys and girls were divided into two groups of pre-adolescence (<11 years) and adolescence (>10 years). High tracking coefficients (>8) were found for nutritional status, body mass index, and fat-free mass, while low tracking coefficients (<4) were found for the sum of skinfolds, fat mass, arm muscle area, and central fat distribution. Moderate and low tracking coefficients were found for the physical fitness items. Longitudinal regression analyses showed that physical fitness performances that require a high energy flux over a short period of time are affected by muscle wasting, whereas having a low body weight appears to be important for a good performance on other fitness items in these malnourished rural South African children.

  16. [Orotracheal intubation and temporomandibular disorder: a longitudinal controlled study].

    PubMed

    Battistella, Cláudia Branco; Machado, Flávia Ribeiro; Juliano, Yara; Guimarães, Antônio Sérgio; Tanaka, Cássia Emi; Garbim, Cristina Talá de Souza; Fonseca, Paula de Maria da Rocha; Sanches, Monique Lalue

    2016-01-01

    To determine the incidence of signs and symptoms of temporomandibular disorder in elective surgery patients who underwent orotracheal intubation. This was a longitudinal controlled study with two groups. The study group included patients who underwent orotracheal intubation and a control group. We used the American Academy of Orofacial Pain questionnaire to assess the temporomandibular disorder signs and symptoms one-day postoperatively (T1), and the patients' baseline status prior to surgery (T0) was also recorded. The same questionnaire was used after three months (T2). The mouth opening amplitude was measured at T1 and T2. We considered a p value of less than 0.05 to be significant. We included 71 patients, with 38 in the study group and 33 in the control. There was no significant difference between the groups in age (study group: 66 [52.5-72]; control group: 54 [47-68]; p=0.117) or in their belonging to the female gender (study group: 57.9%; control group: 63.6%; p=0.621). At T1, there were no statistically significant differences between the groups in the incidence of mouth opening limitation (study group: 23.7% vs. 18.2%; p=0.570) or in the mouth opening amplitude (study group: 45 [40-47] vs. 46 [40-51]; p=0.278). At T2 we obtained similar findings. There was no significant difference in the affirmative response to all the individual questions in the American Academy of Orofacial Pain questionnaire. In our population, the incidence of signs and symptoms of temporomandibular disorder of muscular origin was not different between the groups. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

  17. Orotracheal intubation and temporomandibular disorder: a longitudinal controlled study.

    PubMed

    Battistella, Cláudia Branco; Machado, Flávia Ribeiro; Juliano, Yara; Guimarães, Antônio Sérgio; Tanaka, Cássia Emi; de Souza Garbim, Cristina Talá; de Maria da Rocha Fonseca, Paula; Sanches, Monique Lalue

    2016-01-01

    To determine the incidence of signs and symptoms of temporomandibular disorder in elective surgery patients who underwent orotracheal intubation. This was a longitudinal controlled study with two groups. The study group included patients who underwent orotracheal intubation and a control group. We used the American Academy of Orofacial Pain questionnaire to assess the temporomandibular disorder signs and symptoms one-day postoperatively (T1), and the patients' baseline status prior to surgery (T0) was also recorded. The same questionnaire was used after three months (T2). The mouth opening amplitude was measured at T1 and T2. We considered a p value of less than 0.05 to be significant. We included 71 patients, with 38 in the study group and 33 in the control. There was no significant difference between the groups in age (study group: 66.0 [52.5-72.0]; control group: 54.0 [47.0-68.0]; p=0.117) or in their belonging to the female gender (study group: 57.9%; control group: 63.6%; p=0.621). At T1, there were no statistically significant differences between the groups in the incidence of mouth opening limitation (study group: 23.7% vs. 18.2%; p=0.570) or in the mouth opening amplitude (study group: 45.0 [40.0-47.0] vs. 46.0 [40.0-51.0]; p=0.278). At T2 we obtained similar findings. There was no significant difference in the affirmative response to all the individual questions in the American Academy of Orofacial Pain questionnaire. In our population, the incidence of signs and symptoms of temporomandibular disorder of muscular origin was not different between the groups. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

  18. UV FEL light source for industrial processing

    NASA Astrophysics Data System (ADS)

    Kelley, Michael J.; Dylla, H. Frederick; Neil, George R.; Brillson, Leonard J.; Henkel, Daniel P.; Helvajian, Henry

    1996-04-01

    Short-wavelength UV light is strongly absorbed by most materials, creating the opportunity to drive near-surface thermal or chemical processes. The resulting modifications have a wide range of prospective applications, but few have been developed because of the low capacity and high unit cost of light from present sources. We analyze the light source requirements for large-scale applications to polymers and metals. We describe meeting them with free electron laser whose design is described in a companion paper in this session. This machine will deliver 1.0 to 2.5 kW between 190 nm and 350 nm with options in the visible and IR, and serve to further develop FEL technology for much higher powered machines. We gratefully acknowledge support for this work from the Commonwealth of Virginia Center for Innovative Technologies and The U.S. Department of Energy.

  19. Peer Victimization in Childhood and Internalizing Problems in Adolescence: A Prospective Longitudinal Study

    ERIC Educational Resources Information Center

    Zwierzynska, Karolina; Wolke, Dieter; Lereya, Tanya S.

    2013-01-01

    Traumatic childhood experiences have been found to predict later internalizing problems. This prospective longitudinal study investigated whether repeated and intentional harm doing by peers (peer victimization) in childhood predicts internalizing symptoms in early adolescence. 3,692 children from the Avon Longitudinal Study of Parents and…

  20. The Timing of Maternal Depressive Symptoms and Child Cognitive Development: A Longitudinal Study

    ERIC Educational Resources Information Center

    Evans, Jonathan; Melotti, Roberto; Heron, Jon; Ramchandani, Paul; Wiles, Nicola; Murray, Lynne; Stein, Alan

    2012-01-01

    Background: Maternal depression is known to be associated with impairments in child cognitive development, although the effect of timing of exposure to maternal depression is unclear. Methods: Data collected for the Avon Longitudinal Study of Parents and Children, a longitudinal study beginning in pregnancy, included self-report measures of…

  1. Reducing Bias Due to Systematic Attrition in Longitudinal Studies: The Benefits of Multiple Imputation

    ERIC Educational Resources Information Center

    Asendorpf, Jens B.; van de Schoot, Rens; Denissen, Jaap J. A.; Hutteman, Roos

    2014-01-01

    Most longitudinal studies are plagued by drop-out related to variables at earlier assessments (systematic attrition). Although systematic attrition is often analysed in longitudinal studies, surprisingly few researchers attempt to reduce biases due to systematic attrition, even though this is possible and nowadays technically easy. This is…

  2. The Timing of Maternal Depressive Symptoms and Child Cognitive Development: A Longitudinal Study

    ERIC Educational Resources Information Center

    Evans, Jonathan; Melotti, Roberto; Heron, Jon; Ramchandani, Paul; Wiles, Nicola; Murray, Lynne; Stein, Alan

    2012-01-01

    Background: Maternal depression is known to be associated with impairments in child cognitive development, although the effect of timing of exposure to maternal depression is unclear. Methods: Data collected for the Avon Longitudinal Study of Parents and Children, a longitudinal study beginning in pregnancy, included self-report measures of…

  3. The doubly labeled water method produces highly reproducible longitudinal results in nutrition studies

    USDA-ARS?s Scientific Manuscript database

    The doubly labeled water (DLW) method is considered the reference method for the measurement of energy expenditure under free-living conditions. However, the reproducibility of the DLW method in longitudinal studies is not well documented. This study was designed to evaluate the longitudinal reprodu...

  4. Neurophysiological Characterization of Subacute Stroke Patients: A Longitudinal Study

    PubMed Central

    Lamola, Giuseppe; Fanciullacci, Chiara; Sgherri, Giada; Bertolucci, Federica; Panarese, Alessandro; Micera, Silvestro; Rossi, Bruno; Chisari, Carmelo

    2016-01-01

    Various degrees of neural reorganization may occur in affected and unaffected hemispheres in the early phase after stroke and several months later. Recent literature suggests to apply a stratification based on lesion location and to consider patients with cortico-subcortical and subcortical strokes separately: different lesion location may also influence therapeutic response. In this study we used a longitudinal approach to perform TMS assessment (Motor Evoked Potentials, MEP, and Silent Period, SP) and clinical evaluations (Barthel Index, Fugl-Meyer Assessment for upper limb motor function and Wolf Motor Function Test) in 10 cortical-subcortical and 10 subcortical ischemic stroke patients. Evaluations were performed in a window between 10 and 45 days (t0) and at 3 months after the acute event (t1). Our main finding is that 3 months after the acute event patients affected by subcortical stroke presented a reduction in contralateral SP duration in the unaffected hemisphere; this trend is related to clinical improvement of upper limb motor function. In conclusion, SP proved to be a valid parameter to characterize cortical reorganization patterns in stroke survivors and provided useful information about motor recovery within 3 months in subcortical patients. PMID:27899888

  5. Spiritual stress and coping model of divorce: a longitudinal study.

    PubMed

    Krumrei, Elizabeth J; Mahoney, Annette; Pargament, Kenneth I

    2011-12-01

    This study represents the first longitudinal effort to use a spiritual stress and coping model to predict adults' psychosocial adjustment following divorce. A community sample of 89 participants completed measures at the time of their divorce and 1 year later. Though the sample endorsed slightly lower levels of religiosity than the general U.S. population, most reported spiritual appraisals and positive and negative religious coping tied to divorce. Hierarchical regression analyses controlling general religiousness and nonreligious forms of coping indicated that (a) appraising divorce as a sacred loss or desecration at the time it occurred predicted more depressive symptoms and dysfunctional conflict tactics with the ex-spouse 1 year later; (b) positive religious coping reported about the year following divorce predicted greater posttraumatic growth 1 year after divorce; and (c) negative religious coping reported about the year following divorce predicted more depressive symptoms 1 year after the divorce. Bootstrapping mediation analyses indicated that negative religious coping fully mediated links between appraising the divorce as a sacred loss or desecration at the time it occurred and depressive symptoms 1 year later. In addition, moderation analyses revealed that negative religious coping is more strongly associated with depressive symptoms among those who form high versus low appraisals of their divorce as a sacred loss or desecration. These findings are relevant to divorce education and intervention provided by professionals in legal, family, mental health, and clerical roles. Implications are discussed for clinical and counseling psychology and religious communities.

  6. Results from the Longitudinal Study of Astronomy Graduate Students

    NASA Astrophysics Data System (ADS)

    Ivie, Rachel

    2014-01-01

    The Longitudinal Study of Astronomy Graduate Students (LSAGS), an ongoing, joint project of the American Astronomical Society (AAS) and the American Institute of Physics (AIP), first collected survey data from astronomy and astrophysics graduate students in 2007-08. The LSAGS follows the same people, all of whom were in graduate school in 2006-07, over time as they start their careers. Most of the respondents are currently working as postdocs. There have been two rounds of the survey so far, and we have recently received funding for a third round from the National Science Foundation (AST-1347723). Results from the first round showed the importance of mentoring for graduate students. Data collection for the second round has been completed, and AIP has just begun analysis of these data. At this talk, I will present the results of the second survey. Ultimately, the LSAGS will *provide detailed data on trends in employment over 10+ years for a single cohort, *collect data on people who leave the field of astronomy during or after graduate school, *determine whether there are sex differences in attrition from astronomy and reasons for this, and *examine factors that precede decisions to persist in, or leave, the field of astronomy.

  7. Longitudinal Study of Student Attitudes in a Biology Program

    PubMed Central

    Birol, Gülnur

    2014-01-01

    This is among the first longitudinal studies to report student attitudes across 4 yr of a university program. We found that the attitudes of students in biology become significantly more expert-like from the first year to the fourth year of the program, that is, there was a significant positive shift in students’ overall percent favorable scores from 64.5 to 72%, as opposed to the expert response, which averaged 90%. There was a significant positive shift for the real world connection category (78–85%), the enjoyment (personal interest) category (74–82%), and the conceptual connections/memorization category (66–74%). Moreover, there was a significant correlation between students’ overall percent favorable scores and performance (cumulative grade point average) at the end, but not at the beginning, of the fourth year, with high-performing students having significantly more expert-like attitudes than low-performing students. The correlation between percent favorable score and performance was the strongest for the problem solving: synthesis and application category, in which the highest-performing students finished their fourth year with 90% favorable compared with 35% favorable for the lowest-performing students. A comparison of these results with previously reported results and their implications for teaching are discussed. PMID:26086663

  8. Some antecedents of academic self-concept: a longitudinal study.

    PubMed

    Chapman, J W; Lambourne, R; Silva, P A

    1990-06-01

    The influence of cognitive, achievement, and family background variables on academic self-concept was examined for 435 students participating in a major longitudinal study in New Zealand. Family background variables included mother's marital status at the birth of the child, family socio-economic status at the time the child was born, and family environment when the child was 7 years and 9 years of age. These factors were not significantly related to academic self-concept at ages 9 and 11. In addition, the general emotional status of mothers when their child was 3 years and 5 years old was not significantly related to academic self-concept at ages 9 and 11. Mother's intelligence when the child was 3 years, and mother's expectations for school performance when the child started school at age 5 were not significantly related to academic self-concept. Similarly, cognitive and intellectual functioning at ages 3, 5, 7, and 9 years were not significantly related to academic self-concept at ages 7 and 9 years. Rather, academic self-concept at age 11 appeared to be influenced primarily by reading achievement and academic self-concept at age 9, and academic self-concept at age 9 was influenced primarily by reading achievement at age 7. It was concluded that academic self-concept is mainly a product of school achievement, and that any influence home background factors may have are likely to occur by means of their effect on school achievement.

  9. A longitudinal study of infant faecal microbiota during weaning.

    PubMed

    Magne, Fabien; Hachelaf, Wahiba; Suau, Antonia; Boudraa, Ghazalia; Mangin, Irène; Touhami, Mahmoud; Bouziane-Nedjadi, Karim; Pochart, Philippe

    2006-12-01

    For infants, the introduction of food other than breast milk is a high risk period due to diarrheal diseases, and may be corroborated with a shift in the faecal microbiota. This longitudinal study was the first undertaken to understand the effect of the supplementation on the infant's faecal microbiota and particularly the bifidobacteria. Eleven infants were enrolled. Their faecal microbiota were analysed using temporal temperature gradient gel electrophoresis (TTGE) with bacterial and bifidobacterial primers. In parallel, bifidobacterial counts were followed using competitive PCR. Three periods were distinguished: exclusive breastfeeding (Bf period), weaning (i.e. formula-milk addition, W period) and postweaning (i.e. breastfeeding cessation, Pw period). The bifidobacterial counts were not modified, reaching 10.5 (Log10 cells g(-1) wet weight). In the TTGE profiles, the main identified bands corresponded to Escherichia coli, Ruminococcus sp. and Bifidobacterium sp., more precisely Bifidobacterium longum, Bifidobacterium infantis and Bifidobacterium breve. For both TTGE profiles, the analysis of the distance suggested a maturation of the faecal microbiota but no correlation could be established with the diet. Despite a high interindividual variability, composition of the faecal microbiota appeared more homogenous after weaning and this point may be correlated with the cessation of breastfeeding.

  10. Cost of breast cancer treatment. A 4-year longitudinal study.

    PubMed

    Legorreta, A P; Brooks, R J; Leibowitz, A N; Solin, L J

    1996-10-28

    To determine the longitudinal cost of the treatment of patients with breast cancer. An analysis was performed of 200 women with 205 newly diagnosed breast cancers during 1989 in a health maintenance organization population (US Healthcare, Blue Bell, Pa). Medical records and claims data were analyzed for the total costs of medical care during the 4-year period after diagnosis. The costs over time were analyzed for clinical stage and use of mammography screening. The total costs of medical care during the 4-year period after diagnosis were strongly related to clinical stage at diagnosis, with higher total costs for patients with stages III to IV at diagnosis compared with patients with stages 0 to II at diagnosis. The cost for all stages of disease declined after years 1 to 2, with the exception of stage II, which increased slightly in years 3 to 4. The use of screening mammography was associated with a significant decrease in the cost of medical care during the 4-year study period. The goal of mammography screening programs should be to achieve downstaging to stages 0 to 1 to achieve reduction in breast cancer mortality and to reduce the overall consumption of health care resources for the treatment of breast cancer. These cost data should be considered within the framework of future cost-effective analysis for screening mammography programs.

  11. Lung function in asphalt pavers: a longitudinal study.

    PubMed

    Ulvestad, Bente; Randem, Britt Grethe; Skare, Øivind; Aaløkken, Trond Mogens; Myranek, Georg Karl; Elihn, Karine; Lund, May Brit

    2017-01-01

    To study longitudinal changes in lung function in asphalt pavers and a reference group of road maintenance workers, and to detect possible signs of lung disease by high-resolution computed tomography (HRCT) scans. Seventy-five asphalt pavers and 71 road maintenance workers were followed up with questionnaires and measurements of lung function. Not every worker was tested every year, but most of them had four or more measurement points. The 75 asphalt pavers were also invited to have HRCT scans of the lungs at the end of the follow-up period. Mean annual decline in forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) of the asphalt pavers was 58 and 35 ml, respectively. Adjusted for age at baseline, packyears of smoking and BMI, the asphalt pavers had a significant excess annual decline in FVC and FEV1 compared to the references. The screedmen, the most exposed group of the asphalt pavers, showed a significantly larger decline in FVC than the other asphalt pavers (P = 0.029). Fine intralobular fibrosis without evident cysts was identified with HRCT in three subjects (4 %). We conclude that our findings may indicate an excess annual decline in FVC and FEV1 related to exposure to asphalt fumes. The screedmen, who carry out their work behind and close to the paving machine, had the largest decline in lung function. The finding of adverse pulmonary effects in asphalt pavers calls for better technological solutions to prevent exposure.

  12. Parent-offspring similarity for drinking: a longitudinal adoption study.

    PubMed

    McGue, Matt; Malone, Steve; Keyes, Margaret; Iacono, William G

    2014-11-01

    Parent-offspring resemblance for drinking was investigated in a sample of 409 adopted and 208 non-adopted families participating in the Sibling Interaction and Behavior Study. Drinking data was available for 1,229 offspring, assessed longitudinally up to three times in the age range from 10 to 28 years. A single drinking index was computed from four items measuring quantity, frequency and density of drinking. As expected, the mean drinking index increased with age, was greater in males as compared to females (although not at the younger ages), but did not vary significantly by adoption status. Parent-offspring correlation in drinking did not vary significantly by either offspring or parent gender but did differ significantly by adoption status. In adopted families, the parent-offspring correlation was statistically significant at all ages but decreased for the oldest age group (age 22-28). In non-adopted families, the parent-offspring correlation was statistically significant at all ages and increased in the oldest age group. Findings imply that genetic influences on drinking behavior increase with age while shared family environment influences decline, especially during the transition from late-adolescence to early adulthood.

  13. [Longitudinal study of the situational specificity of coping strategies].

    PubMed

    Mafune, Kosuke; Kosugi, Shotaro

    2007-02-01

    This longitudinal study examines the situational specificity of coping strategies for 3 943 male employees of the research and development division of an industrial company. The Job Stress Scale-Revised version (JSS-R) was administered twice to the same subjects 40 months apart to assess chronic job stressors (qualitative and quantitative) and coping strategies (problem-solving, support-seeking, and problem-leaving). Analysis of variance (ANOVA) was used to examine changes in coping strategies corresponding to changes in chronic job stressors. The results suggest a situational specificity of coping strategies. (a) With decreasing qualitative stressors, "problem-solving" coping increases and "problem-leaving" coping decreases. (b) With increasing qualitative stressors, "problem-leaving" coping increases and "problem-solving" coping decreases. (c) With increasing quantitative stressors, "support-seeking" coping increases. (d) With decreasing quantitative stressors, "problem-leaving" coping decreases. (e) There is no variance in "problem-leaving" coping attributable to the change in the quantitative stressors when the qualitative stressors decrease or increase. "Problem-leaving" coping is more strongly related to qualitative than quantitative stressors.

  14. Long term and transitional intermittent smokers: a longitudinal study

    PubMed Central

    Lindstrom, M; Isacsson, S

    2002-01-01

    Objective: To investigate differences in snuff consumption, sociodemographic and psychosocial characteristics between baseline intermittent smokers that had become daily smokers, stopped smoking or remained intermittent smokers at the one year follow up. Design/setting/participants/measurements: A population of 12 507 individuals interviewed at baseline in 1992-94 and at a one year follow up, aged 45–69 years, was investigated in a longitudinal study. The three groups of baseline intermittent smokers were compared to the reference population (all others) according to sociodemographic, psychosocial, and snuff consumption characteristics. A multivariate logistic regression model was used to assess differences in psychosocial conditions, adjusting for age, sex, country of origin, marital status, education, and snuff consumption. Results: 60% of all baseline intermittent smokers had remained intermittent smokers, 16% had become daily smokers, and 24% had stopped smoking at the one year follow up. The long term intermittent smokers and those who had stopped smoking were young, unmarried, highly educated, and snuff consumers to a higher extent than the reference population. They also had more psychosocial resources than the reference population, while the psychosocial resources of those who had become daily smokers were poorer. Conclusions: The majority of intermittent smokers are long term intermittent smokers. The results suggest that long term intermittent smokers have other psychosocial characteristics than daily smokers. PMID:11891370

  15. Minor delinquency and immigration: a longitudinal study among male adolescents.

    PubMed

    Titzmann, Peter F; Silbereisen, Rainer K; Mesch, Gustavo

    2014-01-01

    On the basis of general theories of delinquency and the specific situation of immigrants, this longitudinal study investigated predictors of initial levels and rates of change in delinquency among 188 male ethnic German Diaspora immigrants from the former Soviet Union (FSU) in Germany, 237 male native German adolescents, and 182 male Jewish Diaspora adolescents from the FSU in Israel. The participants (15.2 years old) completed 3 annual assessments. Latent growth curve models showed that ethnic German adolescents reported higher initial levels of delinquency than native German adolescents and lower levels than the Russian Jewish adolescents. Groups did not differ in the rate of change, indicating a decrease in delinquency over time. Peer-oriented leisure related positively and parental knowledge negatively with levels and change rates in delinquency in all groups, but could not fully account for the ethnic differences in delinquency levels. School bonding was associated negatively with delinquency only among native German adolescents. Acculturation-related hassles were an additional predictor for higher levels and also associated with change rates in the immigrant groups. Thus, general theories of delinquency apply to immigrants, but may be complemented by adding acculturation-specific challenges.

  16. Trajectories of PTSD: a 20-year longitudinal study.

    PubMed

    Solomon, Zahava; Mikulincer, Mario

    2006-04-01

    This study assessed the psychopathological effects of combat in veterans with and without combat stress reaction. Veterans (N=214) from the 1982 Lebanon War were assessed in a prospective longitudinal design: 131 suffered from combat stress reaction during the war, and 83 did not. They were evaluated 1, 2, 3, and 20 years after the war. Combat stress reaction is an important vulnerability marker. Veterans with combat stress reaction were 6.6 times more likely to endorse posttraumatic stress disorder (PTSD) at all four measurements, their PTSD was more severe, and they were at increased risk for exacerbation/reactivation. A qualitative analysis of the profile of PTSD symptoms revealed some time-related changes in the symptom configuration of veterans who did not suffer from combat stress reaction. In both groups, the course fluctuated; PTSD rates dropped 3 years postwar and rose again 17 years later; 23% of veterans without combat stress reaction reported delayed PTSD. These findings suggest that the detrimental effects of combat are deep and enduring and follow a complex course, especially in combat stress reaction casualties. The implications of aging and ongoing terror in impeding recovery from the psychological wounds of war are discussed.

  17. Phenol reduces hypertonia and enhances strength: a longitudinal case study.

    PubMed

    McCrea, Patrick H; Eng, Janice J; Willms, Rhonda

    2004-06-01

    Phenyl alcohol blocks are used to relieve spasticity. Such nerve conduction blocks result from phenol-induced axonotmesis and could potentially affect muscle properties related to the ability to generate, maximize, and reduce force. This study assessed the 12-week longitudinal effect of phenol on position (stiffness) and velocity (damping) components of hypertonia, in addition to strength (peak torque and times to generate and reduce torque) in an individual with chronic elbow flexor spasticity following stroke. Phenol motor point injections of flexor muscles paradoxically increased the magnitude of flexion torque and decreased the times required to generate and reduce flexion and extension joint torques, in addition to reducing elbow extension stiffness and damping. Large reductions in the velocity-related component of hypertonia (damping changes > 90%) occurred immediately following injection, which is a finding that supports the velocity-dependent definition of spasticity. Although the changes in damping were large and transient, changes in stiffness and strength variables were small, slower to occur, and maintained. This suggests secondary changes following nerve block, possibly facilitated by regular elbow use subsequent to spasticity reduction.

  18. A longitudinal study of category-specific agnosia.

    PubMed

    Thomas, Richard M; Forde, Emer M E; Humphreys, Glyn W; Graham, Kim S

    2002-01-01

    We report a 12-year longitudinal case study on a 60-year-old male patient (DW) with category-specific agnosia. The extent to which DW's impairment has changed over time was evaluated using identical tests at time 1 (1988) and time 2 (2000). In particular, we assessed his ability to identify pictures and real objects, to draw from memory, and to access stored semantic information about living and non-living things. The principal findings were: (i). DW was significantly better at identifying real objects in comparison with line drawings. (ii). DW presented with a category-specific impairment for living things that remained consistent over the 12-year period. (iii). He significantly improved in his ability to identify real non-living objects over the 12-year period but real living objects remained at floor. (iv). His ability to access stored visual knowledge declined over time. On the basis of these data, we suggest that visual perception is required to maintain intact visual memories over a period of time. We also suggest that integrative visual agnosia co-occurs with a category-specific impairment for living things because the recognition of these items requires more global processing than for non-living things. In addition, we suggest that degradation to stored visual knowledge can cause category-specific naming impairments for living compared with non-living things because naming living things requires access to more detailed visual knowledge.

  19. Parent-Offspring Similarity for Drinking: A Longitudinal Adoption Study

    PubMed Central

    McGue, Matt; Malone, Steve; Keyes, Margaret; Iacono, William G.

    2015-01-01

    Parent-offspring resemblance for drinking was investigated in a sample of 409 adopted and 208 non-adopted families participating in the Sibling Interaction and Behavior Study (SIBS). Drinking data was available for 1229 offspring, assessed longitudinally up to three times in the age range from 10 to 28 years. A single drinking index was computed from four items measuring quantity, frequency and density of drinking. As expected, the mean drinking index increased with age, was greater in males as compared to females (although not at the younger ages), but did not vary significantly by adoption status. Parent-offspring correlation in drinking did not vary significantly by either offspring or parent gender but did differ significantly by adoption status. In adopted families, the parent-offspring correlation was statistically significant at all ages but decreased for the oldest age group (age 22–28). In non-adopted families, the parent-offspring correlation was statistically significant at all ages and increased in the oldest age group. Findings imply that genetic influences on drinking behavior increase with age while shared family environment influences decline, especially during the transition from late-adolescence to early adulthood. PMID:25224596

  20. Markers of gluten sensitivity in acute mania: a longitudinal study.

    PubMed

    Dickerson, Faith; Stallings, Cassie; Origoni, Andrea; Vaughan, Crystal; Khushalani, Sunil; Yolken, Robert

    2012-03-30

    Increased levels of antibodies to gliadin, which is derived from the wheat protein gluten, have been reported in schizophrenia and bipolar disorder in cross-sectional studies. We examined longitudinally the levels of antibody reactivity to gliadin in acute mania. The sample included 60 individuals assessed during a hospital stay for acute mania, 39 at a 6-month follow-up, and a sample of 143 non-psychiatric controls. Antibodies to gliadin were measured by enzyme immunoassay. The relationship of the antibodies to the clinical course of mania was analyzed by the use of regression models. Individuals with mania had significantly increased levels of IgG antibodies to gliadin, but not other markers of celiac disease, at baseline compared with controls in multivariate analyses. However, these levels were not significantly different from those of controls at the six month follow-up. Among the individuals with mania, elevated levels at follow-up were significantly associated with re-hospitalization in the 6-month follow-up period. The monitoring and control of gluten sensitivity may have significant effects on the management of individuals hospitalized with acute mania.

  1. Longitudinal study of habits leading to malocclusion development in childhood

    PubMed Central

    2014-01-01

    Background The increased prevalence of malocclusions represents a secular trend attributed to the interaction of genetic and environmental factors. The analysis of factors related to the causes of these changes is essential for planning public health policies aimed at preventing and clinically intercepting malocclusion. This study investigated the sucking habits, nocturnal mouth breathing, as well as the relation of these factors with malocclusion. Methods This is a longitudinal study in which 80 mother-child pairs were monitored from the beginning of pregnancy to the 30th month after childbirth. Home visits for interviews with the mothers were made on the 12th, 18th and 30th months of age. Finger sucking, pacifier sucking, bottle feeding, breastfeeding and nocturnal mouth breathing, were the variables studies. On the 30th month, clinical examinations were performed for overjet, overbite and posterior crossbite. A previously calibrated single examiner (Kappa coefficient = 0.92) was responsible for all examinations. Data were analyzed using the chi-squared or Fisher’s exact tests, at a significance level of 5%. Results Bottle feeding was the most prevalent habit at 12, 18 and 30 months (87.5%; 90% and 96.25%, respectively). Breastfeeding was 40%, 25% and 12.50% at 12, 18 and 30 months, respectively. Nearly 70% of the children in this study had some sort of malocclusion. Pacifier sucking habit at 12, 18 and 30 months of age was associated with overjet and open bite; and at 30 months, an association with overbite was also observed. Finger sucking habit and breastfeeding at 12, 18 and 30 months were also associated with overjet and open bite. The posterior crossbite was associated with bottle feeding at 12 and 30 months, and nocturnal mouth breathers at 12 and 18 months. Conclusions Sucking habits, low rates of breastfeeding, and nocturnal mouth breathing were risk factors for malocclusion. PMID:25091288

  2. Longitudinal study of habits leading to malocclusion development in childhood.

    PubMed

    Moimaz, Suzely Adas Saliba; Garbin, Artênio José Ísper; Lima, Arinilson Moreira Chaves; Lolli, Luiz Fernando; Saliba, Orlando; Garbin, Cléa Adas Saliba

    2014-08-04

    The increased prevalence of malocclusions represents a secular trend attributed to the interaction of genetic and environmental factors. The analysis of factors related to the causes of these changes is essential for planning public health policies aimed at preventing and clinically intercepting malocclusion. This study investigated the sucking habits, nocturnal mouth breathing, as well as the relation of these factors with malocclusion. This is a longitudinal study in which 80 mother-child pairs were monitored from the beginning of pregnancy to the 30th month after childbirth. Home visits for interviews with the mothers were made on the 12th, 18th and 30th months of age. Finger sucking, pacifier sucking, bottle feeding, breastfeeding and nocturnal mouth breathing, were the variables studies. On the 30th month, clinical examinations were performed for overjet, overbite and posterior crossbite. A previously calibrated single examiner (Kappa coefficient = 0.92) was responsible for all examinations. Data were analyzed using the chi-squared or Fisher's exact tests, at a significance level of 5%. Bottle feeding was the most prevalent habit at 12, 18 and 30 months (87.5%; 90% and 96.25%, respectively). Breastfeeding was 40%, 25% and 12.50% at 12, 18 and 30 months, respectively. Nearly 70% of the children in this study had some sort of malocclusion. Pacifier sucking habit at 12, 18 and 30 months of age was associated with overjet and open bite; and at 30 months, an association with overbite was also observed. Finger sucking habit and breastfeeding at 12, 18 and 30 months were also associated with overjet and open bite. The posterior crossbite was associated with bottle feeding at 12 and 30 months, and nocturnal mouth breathers at 12 and 18 months. Sucking habits, low rates of breastfeeding, and nocturnal mouth breathing were risk factors for malocclusion.

  3. MAOA, abuse exposure and antisocial behaviour: 30-year longitudinal study

    PubMed Central

    Fergusson, David M.; Boden, Joseph M.; Horwood, L. John; Miller, Allison L.; Kennedy, Martin A.

    2011-01-01

    Background Recent studies have raised issues concerning the replicability of gene × environment (G × E) interactions involving the monoamine oxidase A (MAOA) gene in moderating the associations between abuse or maltreatment exposure and antisocial behaviour. This study attempted to replicate the findings in this area using a 30-year longitudinal study that has strong resemblance to the original research cohort. Aims To test the hypothesis that the presence of the low-activity MAOA genotype was associated with an increased response to abuse exposure. Method Participants were 398 males from the Christchurch Health and Development Study who had complete data on: MAOA promoter region variable number tandem repeat genotype; antisocial behaviour to age 30; and exposure to childhood sexual and physical abuse. Results Regression models were fitted to five antisocial behaviour outcomes (self-reported property offending; self-reported violent offending; convictions for property/violent offending; conduct problems; hostility) observed from age 16 to 30, using measures of childhood exposure to sexual and physical abuse. The analyses revealed consistent evidence of G × E interactions, with those having the low-activity MAOA variant and who were exposed to abuse in childhood being significantly more likely to report later offending, conduct problems and hostility. These interactions remained statistically significant after control for a range of potentially confounding factors. Findings for convictions data were somewhat weaker. Conclusions The present findings add to the evidence suggesting that there is a stable G × E interaction involving MAOA, abuse exposure and antisocial behaviour across the life course. PMID:21628708

  4. Rationales, design and recruitment for the Elfe longitudinal study

    PubMed Central

    Vandentorren, Stéphanie; Bois, Corinne; Pirus, Claudine; Sarter, Hélène; Salines, Georges; Leridon, Henri

    2009-01-01

    Background Many factors act simultaneously in childhood to influence health status, life chances and well being, including pre-birth influences, the environmental pollutants of early life, health status but also the social influences of family and school. A cohort study is needed to disentangle these influences and explore attribution. Methods Elfe will be a nationally representative cohort of 20 000 children followed from birth to adulthood using a multidisciplinary approach. The cohort will be based on the INSEE Permanent Demographic Panel (EDP) established using census data and civil records. The sample size has been defined in order to match the representativeness criteria and to obtain some prevalence estimation, but also to address the research area of low exposure/rare effects. The cohort will be based on repeated surveys by face to face or phone interview (at birth and each year) as well as medical interview (at 2 years) and examination (at 6 years). Furthermore, biological samples will be taken at birth to evaluate the foetal exposition to toxic substances, environmental sensors will be placed in the child's homes. Pilot studies have been initiated in 2007 (500 children) with an overall acceptance rate of 55% and are currently under progress, the 2-year survey being carried out in October this year. Discussion The longitudinal study will provide a unique source of data to analyse the development of children in their environment, to study the various factors interacting throughout the life course up to adulthood and to determine the impact of childhood experience on the individual's physical, psychological, social and professional development. PMID:19772571

  5. Picky eating and child weight status development: a longitudinal study.

    PubMed

    Antoniou, E E; Roefs, A; Kremers, S P J; Jansen, A; Gubbels, J S; Sleddens, E F C; Thijs, C

    2016-06-01

    Children's picky eating behaviour has been linked both to being overweight and underweight. However, the role of parenting practices in this relationship has rarely been investigated. The present study aimed to clarify the direction of the association between picky eating and weight status and to examine the moderating role of food parenting practices. The present study comprised a longitudinal study on the effects of picky eating on child weight status within the KOALA Birth Cohort Study, the Netherlands. Mothers and their children were included in the analyses. Children's picky eating behaviour and food parenting practices were assessed at baseline (child age 5 years). Their weight status was assessed repeatedly until age 9 years. Mixed effects linear and logistic regressions were used to compare picky eaters (n = 403) and non-picky eaters (n = 621) on changes in weight status over the years. At baseline of age 5 years, picky eaters were slightly shorter, more often underweight and less often overweight than non-picky eaters, whereas energy intake in relation to body weight (kJ kg(-1)) was similar. Picky eaters with a normal weight at baseline had no increased risk of becoming underweight during follow-up until age 9 years, and were less likely to become overweight compared to non-picky eaters. There were no interactions with food parenting practices. The parents of picky eaters more often reported pressuring their child to eat and restrict unhealthy food intake compared to parents of non-picky eaters. The association between picky eating and child weight status was not influenced by parenting practices. © 2015 The British Dietetic Association Ltd.

  6. Analysis of the eigenvalue equation of the FEL amplifier with axisymmetric electron beam and diaphragm focusing line

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Ulyanov, Yu.N.

    1995-12-31

    The paper presents analysis of the eigenvalue problem of the FEL amplifier with axisymmetric electron beam and diaphragm focusing line. An FEL model is discussed wherein diffraction effects, space charge fields and energy spread of electrons in the beam are taken into account. To take into account diffraction effects at the diaphragms we apply the rigorous impedance boundary conditions proposed by Veinstein. The rigorous solutions of the eigenvalue problem leave been found for the stepped and bounded parabolic electron beam profiles. Analytical expressions for eigenfunctions of active open waveguide and formulae of their expansion in eigenfunctions of passive open waveguide, are derived, too. Asymptotic behaviour of the obtained solutions is studied in details. The multilayer approximation method has been used to solve the eigenvalue problem for the beams with an arbitrary gradient profile of current density. This novel type of an FEL amplifier has perspective to be used for applications where high average and peak radiation power is required.

  7. Optical properties of infrared FELs from the FELI Facility II

    SciTech Connect

    Saeki, K.; Okuma, S.; Oshita, E.

    1995-12-31

    The FELI Facility II has succeeded in infrared FEL oscillation at 1.91 {mu} m using a 68-MeV, 40-A electron beam from the FELI S-band linac in February 27, 1995. The FELI Facility II is composed of a 3-m vertical type undulator ({lambda}u=3.8cm, N=78, Km a x=1.4, gap length {ge}20mm) and a 6.72-m optical cavity. It can cover the wavelength range of 1-5{mu}m. The FELs can be delivered from the optical cavity to the diagnostics room through a 40-m evacuated optical pipeline. Wavelength and cavity length dependences of optical properties such as peak power, average power, spectrum width, FEL macropulse, FEL transverse profile are reported.

  8. The FERMI seeded-FEL facility: Status and perspectives

    SciTech Connect

    Allaria, Enrico; Badano, Laura; Bencivenga, Filippo; Callegari, Carlo Capotondi, Flavio; Castronovo, Davide; Cinquegrana, Paolo; Coreno, Marcello; Cucini, Riccardo; Cudin, Ivan; Danailov, Miltcho B.; D’Auria, Gerardo; De Monte, Raffaele; De Ninno, Giovanni; Delgiusto, Paolo; Demidovich, Alexander; Di Mitri, Simone; Diviacco, Bruno; Fabris, Alessandro; Fabris, Riccardo; and others

    2016-07-27

    The FERMI Free Electron Laser (FEL) in Trieste, Italy operates in the extreme ultraviolet and soft x rays (EUV-SXR) wavelength range delivering high-fluence, stable, ultra-short pulses. Its unique design based on a seeded scheme and on tunable undulators allows unprecedented control of pulse parameters such as wavelength, phase, polarization, synchronization, pulse duration and implementation of multi-color FEL schemes. Both FEL-1 and FEL-2 lines with nominal wavelength range 100–20 nm and 20–4 nm, respectively, are open to users. We report on the unique features of FERMI, in particular those that have evolved beyond the original design, and on their application to pioneering experiments. We also present the upgrades that are planned to further expand the capabilities of this unique light source.

  9. Electro-Magnetic Quadrupole Magnets in the LCLS FEL Undulator

    SciTech Connect

    Emma, P.

    2005-01-31

    We discuss various aspects of electro-magnetic quadrupole (EMQ) magnets for the LCLS FEL undulator, including their utility in beam-based alignment (BBA), magnet design issues, and impact on tunnel environment, reliability, and cost.

  10. National Longitudinal Study of the High School Class of 1972. Review and Annotation of Study Reports.

    ERIC Educational Resources Information Center

    Peng, Samuel S.; And Others

    Over 150 journal articles, papers presented at professional meetings, dissertations, government publications, contract reports, and studies in progress as of March 1977 on the National Longitudinal Study of the High School Class of 1972 (NLS) are annotated and indexed by subject, author, and sponsoring agency. Introductory chapters describe the…

  11. Social Strategies during University Studies Predict Early Career Work Burnout and Engagement: 18-Year Longitudinal Study

    ERIC Educational Resources Information Center

    Salmela-Aro, Katariina; Tolvanen, Asko; Nurmi, Jari-Erik

    2011-01-01

    This longitudinal study spanning 18 years examined the role of social strategies in early career adaptation. The aim was to find out whether individuals' social strategies measured during their university studies had an impact on work burnout and work engagement measured 10-18 years later. A sample of 292 university students completed the SAQ…

  12. Graduate Pathways: A Longitudinal Study of Graduates in Outdoor Studies in the U.K.

    ERIC Educational Resources Information Center

    Prince, Heather

    2005-01-01

    A longitudinal study provides a more detailed analysis of the career pathways of graduates than the First Destination Survey can achieve. This survey of 41% of graduates from a BSc (Honours) Outdoor Studies degree also examines the importance of named skills to their careers and the success of the degree in developing each skill. Two thirds of…

  13. The value of time in longitudinal studies of ageing. Lessons from the Australian Longitudinal Study on Women's Health.

    PubMed

    Byles, Julie E; Dobson, Annette

    2011-10-01

    The Australian Longitudinal Study on Women's Health (ALSWH) involves three cohorts of women born in 1921-1926, 1946-1951 and 1973-1978, who have been surveyed every 3 years since 1996. We describe how the 1921-1926 cohort have changed over time. We also describe trends in health risks among the younger cohorts, providing an indication of future health threats. By Survey 5, 28.4% of the 1921-1926 cohort had died. Among those who survived and remained in the study, 61% maintained high physical function scores over time. Chronic conditions such as arthritis, diabetes, heart disease and stroke were associated with lower physical function scores and decline in scores over time. ALSWH will continue to provide information on changes in health and health service use as we follow the oldest cohort through their 90 s, and as younger cohorts accumulate increasing burden of disease and disability as they age. © 2011 The Authors. Australasian Journal on Ageing © 2011 ACOTA.

  14. Longitudinal study on methicillin-resistant Staphylococcus pseudintermedius in households.

    PubMed

    Laarhoven, Laura M; de Heus, Phebe; van Luijn, Jeanine; Duim, Birgitta; Wagenaar, Jaap A; van Duijkeren, Engeline

    2011-01-01

    Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is an emerging pathogen in dogs and has been found in Europe, Asia and North America. To date most studies are one-point prevalence studies and therefore little is known about the dynamics of MRSP in dogs and their surrounding. In this longitudinal study MRSP colonization in dogs and the transmission of MRSP to humans, contact animals and the environment was investigated. Sixteen dogs with a recent clinical MRSP infection were included. The index dogs, contact animals, owners and environments were sampled once a month for six months. Samples taken from the nose, perineum and infection site (if present) of the index cases and contact animals, and the nares of the owners were cultured using pre-enrichment. Index cases were found positive for prolonged periods of time, in two cases during all six samplings. In five of the 12 households that were sampled during six months, the index case was intermittently found MRSP-positive. Contact animals and the environment were also found MRSP-positive, most often in combination with a MRSP-positive index dog. In four households positive environmental samples were found while no animals or humans were MRSP-positive, indicating survival of MRSP in the environment for prolonged periods of time. Genotyping revealed that generally similar or indistinguishable MRSP isolates were found in patients, contact animals and environmental samples within the same household. Within two households, however, genetically distinct MRSP isolates were found. These results show that veterinarians should stay alert with (former) MRSP patients, even after repeated MRSP-negative cultures or after the disappearance of the clinical infection. There is a considerable risk of transmission of MRSP to animals in close contact with MRSP patients. Humans were rarely MRSP-positive and never tested MRSP-positive more than once suggesting occasional contamination or rapid elimination of colonization of

  15. Longitudinal study of children with unilateral hearing loss.

    PubMed

    Lieu, Judith E C; Tye-Murray, Nancy; Fu, Qiang

    2012-09-01

    Children with unilateral hearing loss (UHL) have been found to have lower language scores, and increased rate of speech therapy, grade failures, or needing Individualized Education Plans (IEPs). The objective of this study was to determine whether language skills and educational performance improved or worsened over time in a cohort of children with UHL. Prospective longitudinal cohort study. Forty-six children with permanent UHL, ages 6 to 12 years, were studied using standardized cognitive, achievement, and language testing at yearly intervals for 3 years. Using standardized test scores allowed implicit comparison to norms established by national cross-sectional samples. Secondary outcomes included behavioral issues, IEPs, receipt of speech therapy, or teacher report of problems at school. Analysis utilized repeated measures analysis of variance and multilevel random regression modeling. Several cognitive and language mean standardized scores increased over time. Possible predictors of increase with time included higher baseline cognitive levels and receipt of interventions through an IEP. However, standardized achievement scores and indicators of school performance did not show concomitant improvements. Rates of IEPs remained >50% throughout, and rates of speech therapy were consistently about 20%. Children with UHL demonstrated improvement in oral language and verbal intelligence quota scores over time, but not improvements in school performance. Parents and teachers reported persistent behavioral problems and academic weaknesses or areas of concern in about 25%. The provision of IEPs for children with UHL, and acknowledging UHL as a hearing disability, may be an effective intervention to improve language skills over time. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.

  16. Nine year longitudinal retrospective study of Taekwondo injuries.

    PubMed

    Kazemi, Mohsen; Chudolinski, Artur; Turgeon, Matt; Simon, Aaron; Ho, Eric; Coombe, Lianne

    2009-12-01

    This retrospective longitudinal study aims to describe reported Taekwondo injuries and to examine associations between competitor experience level, age and gender, and the type, location, and mechanism of injury sustained. Additionally, we examined whether recent rule changes concerning increased point value of head shots in adult Taekwondo competition had affected injury incidence.This study was a summation of 9 years of data of competition injury reports, which included 904 injury reports spanning 58 individual competitions. The data was collected on standardized injury reports at time of injury during competition. Care was provided to the athletes, but the type of care provided was not included in the study. Participants included athletes injured during competition who sought care by the health care team, and for whom an injury report was filled out. The data analysis was performed at the Canadian Memorial Chiropractic College.The three most common locations of presenting injury were the head (19%), foot (16%), and thigh (9%). The most common mechanism of presenting injury was found to be a defensive kick (44%), followed by an offensive kick (35%). The most commonly diagnosed injuries were contusions (36%), sprains (19%), and strains (15%). Coloured belts had a higher incidence of contusions, while black belts sustained more joint irritation injuries. Black belts were more likely to suffer multiple injuries. Colored belts suffered more injuries while receiving a kick, while black belts had a larger influence of past history of injury. We found no significant difference in location or type of injury when comparing pre versus post rule change. The most common locations of injury are head, foot, and thigh respectively, and are areas for concern when considering preventative measures. Colour belt competitors are more likely to sustain contusions, which the authors believe is due to more aggressive tactics and lack of control. Those more likely to be injured tend to

  17. Distress and job satisfaction after robbery assaults: a longitudinal study.

    PubMed

    Giorgi, G; Leon Perez, J M; Montani, F; Courcy, F; Arcangeli, G

    2015-06-01

    External/intrusive violence at work can result in psychological distress and can be an important risk to employee health and safety. However, the vast majority of workplace violence studies have employed cross-sectional and correlational research, designed to examine immediate reactions after being assaulted at work. To explore whether exposure to robbery as a traumatic event may contribute to the onset of typical symptoms of psychological distress (anxiety depression, dysphoria and loss of confidence) and job dissatisfaction over time. We collected data by using a two-wave panel design, in which employees working the days of bank robberies, in an Italian bank, filled in a questionnaire between 48h and 1 week after the robbery (T1) and 2 months after the robbery (T2). We performed structural equation models to evaluate the fit of different models to our data. There were 513 participants at T1 (58% women) and 175 (34%) participants at T2 (62% women). There was a simultaneous association in which psychological distress leads to job dissatisfaction both following robbery and 2 months later. Our findings support a synchronous effects model and suggest that interventions after suffering physical assaults, apart from helping employees to recover their health, should consider restoring their trust and confidence in the organization. This study contributes to understanding the dynamic relationships between a robbery at work and its outcomes over time, by addressing several methodological deficiencies in previous longitudinal studies. © The Author 2015. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. Pelvic pain after childbirth: a longitudinal population study.

    PubMed

    Bjelland, Elisabeth Krefting; Owe, Katrine Mari; Pingel, Ronnie; Kristiansson, Per; Vangen, Siri; Eberhard-Gran, Malin

    2016-03-01

    In this longitudinal population study, the aims were to study associations of mode of delivery with new onset of pelvic pain and changes in pelvic pain scores up to 7 to 18 months after childbirth. We included 20,248 participants enrolled in the Norwegian Mother and Child Cohort Study (1999-2008) without preexisting pelvic pain in pregnancy. Data were obtained by 4 self-administered questionnaires and linked to the Medical Birth Registry of Norway. A total of 4.5% of the women reported new onset of pelvic pain 0 to 3 months postpartum. Compared to unassisted vaginal delivery, operative vaginal delivery was associated with increased odds of pelvic pain (adjusted odds ratio [OR]: 1.30; 95% confidence interval [CI]: 1.06-1.59). Planned and emergency cesarean deliveries were associated with reduced odds of pelvic pain (adjusted OR: 0.48; 95% CI: 0.31-0.74 and adjusted OR: 0.65; 95% CI: 0.49-0.87, respectively). Planned cesarean delivery, young maternal age, and low Symptom Checklist-8 scores were associated with low pelvic pain scores after childbirth. A history of pain was the only factor associated with increased pelvic pain scores over time (P = 0.047). We conclude that new onset of pelvic pain after childbirth was not commonly reported, particularly following cesarean delivery. Overall, pelvic pain scores were rather low at all time points and women with a history of pain reported increased pelvic pain scores over time. Hence, clinicians should follow up women with pelvic pain after a difficult childbirth experience, particularly if they have a history of pain.

  19. Nine year longitudinal retrospective study of Taekwondo injuries

    PubMed Central

    Kazemi, Mohsen; Chudolinski, Artur; Turgeon, Matt; Simon, Aaron; Ho, Eric; Coombe, Lianne

    2009-01-01

    This retrospective longitudinal study aims to describe reported Taekwondo injuries and to examine associations between competitor experience level, age and gender, and the type, location, and mechanism of injury sustained. Additionally, we examined whether recent rule changes concerning increased point value of head shots in adult Taekwondo competition had affected injury incidence. This study was a summation of 9 years of data of competition injury reports, which included 904 injury reports spanning 58 individual competitions. The data was collected on standardized injury reports at time of injury during competition. Care was provided to the athletes, but the type of care provided was not included in the study. Participants included athletes injured during competition who sought care by the health care team, and for whom an injury report was filled out. The data analysis was performed at the Canadian Memorial Chiropractic College. The three most common locations of presenting injury were the head (19%), foot (16%), and thigh (9%). The most common mechanism of presenting injury was found to be a defensive kick (44%), followed by an offensive kick (35%). The most commonly diagnosed injuries were contusions (36%), sprains (19%), and strains (15%). Coloured belts had a higher incidence of contusions, while black belts sustained more joint irritation injuries. Black belts were more likely to suffer multiple injuries. Colored belts suffered more injuries while receiving a kick, while black belts had a larger influence of past history of injury. We found no significant difference in location or type of injury when comparing pre versus post rule change. The most common locations of injury are head, foot, and thigh respectively, and are areas for concern when considering preventative measures. Colour belt competitors are more likely to sustain contusions, which the authors believe is due to more aggressive tactics and lack of control. Those more likely to be injured tend

  20. Recent Progress in High-Gain FEL Theory

    SciTech Connect

    Huang, Z.; /SLAC

    2005-09-30

    High-gain free electron lasers (FEL) are being developed as extremely bright x-ray sources of a next-generation radiation facility. In this paper, we review the basic theory and the recent progress in understanding the startup, the exponential growth and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission (SASE). We will also discuss how the FEL performance may be affected by various errors and wakefield effects in the undulator.

  1. The performance of the Duke FEL storage ring

    SciTech Connect

    Wu, Y.; Burnham, B.; Litvinenko, V.N.

    1995-12-31

    The commissioning of the Duke FEL storage ring has been completed. During commissioning, we have conducted a series of performance measurements on the storage ring lattice and the electron beam parameters. In this paper, we will discuss the techniques used in the measurements, present measurement results, and compare the measured parameters with the design specifications. In addition, we will present the expected OK-4 FEL performance based on the measured beam parameters.

  2. Longitudinal variability of time-location/activity patterns of population at different ages: a longitudinal study in California

    PubMed Central

    2011-01-01

    Background Longitudinal time-activity data are important for exposure modeling, since the extent to which short-term time-activity data represent long-term activity patterns is not well understood. This study was designed to evaluate longitudinal variations in human time-activity patterns. Method We report on 24-hour recall diaries and questionnaires collected via the internet from 151 parents of young children (mostly under age 55), and from 55 older adults of ages 55 and older, for both a weekday and a weekend day every three months over an 18-month period. Parents also provided data for their children. The self-administrated diary and questionnaire distinguished ~30 frequently visited microenvironments and ~20 activities which we selected to represent opportunities for exposure to toxic environmental compounds. Due to the non-normal distribution of time-location/activity data, we employed generalized linear mixed-distribution mixed-effect models to examine intra- and inter-individual variations. Here we describe variation in the likelihood of and time spent engaging in an activity or being in a microenvironment by age group, day-type (weekday/weekend), season (warm/cool), sex, employment status, and over the follow-up period. Results As expected, day-type and season influence time spent in many location and activity categories. Longitudinal changes were also observed, e.g., young children slept less with increasing follow-up, transit time increased, and time spent on working and shopping decreased during the study, possibly related to human physiological changes with age and changes in macro-economic factors such as gas prices and the economic recession. Conclusions This study provides valuable new information about time-activity assessed longitudinally in three major age groups and greatly expands our knowledge about intra- and inter-individual variations in time-location/activity patterns. Longitudinal variations beyond weekly and seasonal patterns should be

  3. Change over Time: Conducting Longitudinal Studies of Children’s Cognitive Development

    PubMed Central

    Grammer, Jennie K.; Coffman, Jennifer L.; Ornstein, Peter A.; Morrison, Frederick J.

    2014-01-01

    Developmental scientists have argued that the implementation of longitudinal methods is necessary for obtaining an accurate picture of the nature and sources of developmental change (Magnusson & Cairns, 1996; Morrison & Ornstein, 1996; Magnusson & Stattin, 2006). Developmentalists studying cognition have been relatively slow to embrace longitudinal research, and thus few exemplar studies have tracked individual children’s cognitive performance over time and even fewer have examined contexts that are associated with this growth. In this article we first outline some of the benefits of implementing longitudinal designs. Using illustrations from existing studies of children’s basic cognitive development and of their school-based academic performance, we discuss when it may be appropriate to employ longitudinal (versus other) methods. We then outline methods for integrating longitudinal data into one’s research portfolio, contrasting the leveraging of existing longitudinal data sets with the launching of new longitudinal studies in order to address specific questions concerning cognitive development. Finally, for those who are interested in conducting longitudinal investigations of their own, we provide practical on-the-ground guidelines for designing and carrying out such studies of cognitive development. PMID:24955035

  4. Comparing Longitudinal Profile Patterns of Mathematics and Reading in Early Child Longitudinal Study, Kindergarten: The Profile Analysis via Multidimensional Scaling (PAMS) Approach

    ERIC Educational Resources Information Center

    Kim, Se-Kang

    2010-01-01

    The aim of the study is to compare longitudinal patterns from Mathematics and Reading data from the direct child assessment of Early Child Longitudinal Study, Kindergarten (ECLS-K, US Department of Education, National Center for Education Statistics 2006), utilizing Profile Analysis via Multidimensional Scaling (PAMS). PAMS has been used initially…

  5. Cannabis and social welfare assistance: a longitudinal study.

    PubMed

    Pedersen, Willy

    2011-09-01

    To investigate associations between cannabis use and subsequent receipt of social welfare assistance. The Young in Norway Longitudinal Study. A population-based Norwegian sample (n = 2606) was followed-up from adolescence to late 20s. Self-report data were merged with data from national registers. Data were extracted on the use of alcohol, tobacco and cannabis and other illegal substances. Information was also retrieved on socio-demographic and family factors, academic achievement, conduct problems and mental health. National registers provided data on social welfare assistance, educational level and crime statistics. We observed prospective bivariate associations between increasing levels of cannabis use and subsequent social welfare assistance (P < 0.0001). The associations were reduced after adjusting for a range of potentially confounding factors, but remained significant. Frequent cannabis users were at highly increased risk for subsequently receiving social welfare assistance. At 28 years, those with 50+ times cannabis use during the previous 12 months and had an odds ratio of 9.3 (95% confidence interval: 4.3-20.1) for receiving social welfare assistance in the following 2-year span. Users of cannabis also had longer periods of receiving social welfare assistance than others (P < 0.0001) and were less likely to leave the welfare assistance system (P < 0.0001). In Norway the use of cannabis is linked with subsequent receipt of social welfare assistance whether the consequences are related to use of the substance per se, or to cultural factors and the illegal status of the cannabis. Future research should attempt to understand the interactions of factors behind these associations. © 2011 The Author, Addiction © 2011 Society for the Study of Addiction.

  6. Longitudinal Study of Postconcussion Syndrome: Not Everyone Recovers

    PubMed Central

    Hiploylee, Carmen; Dufort, Paul A.; Davis, Hannah S.; Wennberg, Richard A.; Tartaglia, Maria Carmela; Mikulis, David; Hazrati, Lili-Naz

    2017-01-01

    Abstract We examined recovery from postconcussion syndrome (PCS) in a series of 285 patients diagnosed with concussion based on international sport concussion criteria who received a questionnaire regarding recovery. Of 141 respondents, those with postconcussion symptoms lasting less than 3 months, a positive computed tomography (CT) and/or magnetic resonance imaging (MRI), litigants, and known Test of Memory Malingering (TOMM)-positive cases were excluded, leaving 110 eligible respondents. We found that only 27% of our population eventually recovered and 67% of those who recovered did so within the first year. Notably, no eligible respondent recovered from PCS lasting 3 years or longer. Those who did not recover (n = 80) were more likely to be non-compliant with a do-not-return-to-play recommendation (p = 0.006) but did not differ from the recovered group (n = 30) in other demographic variables, including age and sex (p ≥ 0.05). Clustergram analysis revealed that symptoms tended to appear in a predictable order, such that symptoms later in the order were more likely to be present if those earlier in the order were already present. Cox proportional hazards model analysis showed that the more symptoms reported, the longer the time to recovery (p = 7.4 × 10−6), with each additional symptom reducing the recovery rate by approximately 20%. This is the first longitudinal PCS study to focus on PCS defined specifically as a minimum of 3 months of symptoms, negative CT and/or MRI, negative TOMM test, and no litigation. PCS may be permanent if recovery has not occurred by 3 years. Symptoms appear in a predictable order, and each additional PCS symptom reduces recovery rate by 20%. More long-term follow-up studies are needed to examine recovery from PCS. PMID:27784191

  7. Changes in HRM in Europe: A Longitudinal Comparative Study among 18 European Countries

    ERIC Educational Resources Information Center

    Nikandrou, Irene; Apospori, Eleni; Papalexandris, Nancy

    2005-01-01

    Purpose: To examine HRM strategies and practices and HRM position within organizations in various cultural, economic and sociopolitical contexts from a longitudinal perspective. Design/methodology/approach: The study uses the 1995 and 1999 Cranet data in a longitudinal methodological framework to explore the changes and trends in 18 European…

  8. Use of Missing Data Methods in Longitudinal Studies: The Persistence of Bad Practices in Developmental Psychology

    ERIC Educational Resources Information Center

    Jelicic, Helena; Phelps, Erin; Lerner, Richard M.

    2009-01-01

    Developmental science rests on describing, explaining, and optimizing intraindividual changes and, hence, empirically requires longitudinal research. Problems of missing data arise in most longitudinal studies, thus creating challenges for interpreting the substance and structure of intraindividual change. Using a sample of reports of longitudinal…

  9. Use of Missing Data Methods in Longitudinal Studies: The Persistence of Bad Practices in Developmental Psychology

    ERIC Educational Resources Information Center

    Jelicic, Helena; Phelps, Erin; Lerner, Richard M.

    2009-01-01

    Developmental science rests on describing, explaining, and optimizing intraindividual changes and, hence, empirically requires longitudinal research. Problems of missing data arise in most longitudinal studies, thus creating challenges for interpreting the substance and structure of intraindividual change. Using a sample of reports of longitudinal…

  10. A Longitudinal Study of Midage Women with Indicators of Disordered Eating

    ERIC Educational Resources Information Center

    Fairweather-Schmidt, A. Kate; Lee, Christina; Wade, Tracey D.

    2015-01-01

    This longitudinal study of midage women has two main aims: to examine the effect of disordered eating (DE) on quality of life (QoL) among women, including a comparison with a younger cohort and to investigate the mediating roles of both depressive symptoms and social support on the longitudinal relationship between DE and QoL as potential…

  11. The Study of Adolescent Identity Formation 2000-2010: A Review of Longitudinal Research

    ERIC Educational Resources Information Center

    Meeus, Wim

    2011-01-01

    Longitudinal research into personal and ethnic identity has expanded considerably in the first decade of the present century. The longitudinal studies have shown that personal identity develops progressively during adolescence, but also that many individuals do not change identity, especially ethnic identity. Researchers have found rank-order…

  12. What Alumni Value from New Product Development Education: A Longitudinal Study

    ERIC Educational Resources Information Center

    Cobb, Corie L.; Hey, Jonathan; Agogino, Alice M.; Beckman, Sara L.; Kim, Sohyeong

    2016-01-01

    We present a longitudinal study of what graduates take away from a cross-disciplinary graduate-level New Product Development (NPD) course at UC Berkeley over a 15-year period from 1996-2010. We designed and deployed a longitudinal survey and interviewed a segment of our NPD alumni population to better understand how well our course prepared these…

  13. Changes in HRM in Europe: A Longitudinal Comparative Study among 18 European Countries

    ERIC Educational Resources Information Center

    Nikandrou, Irene; Apospori, Eleni; Papalexandris, Nancy

    2005-01-01

    Purpose: To examine HRM strategies and practices and HRM position within organizations in various cultural, economic and sociopolitical contexts from a longitudinal perspective. Design/methodology/approach: The study uses the 1995 and 1999 Cranet data in a longitudinal methodological framework to explore the changes and trends in 18 European…

  14. Recruitment Modeling Applied to Longitudinal Studies of Group Differences in Intelligence

    ERIC Educational Resources Information Center

    Madhyastha, Tara M.; Hunt, Earl; Deary, Ian J.; Gale, Catharine R.; Dykiert, Dominika

    2009-01-01

    In longitudinal studies data is collected in a series of waves. Each wave after the first suffers from attrition. Therefore it can be difficult to discriminate between changes in sample parameters due to a longitudinal process (e.g. ageing) and changes due to attrition. The problem is particularly vexing if one of the purposes is to compare…

  15. Problematics of Time and Timing in the Longitudinal Study of Human Development: Theoretical and Methodological Issues

    ERIC Educational Resources Information Center

    Lerner, Richard M.; Schwartz, Seth J.; Phelps, Erin

    2009-01-01

    Studying human development involves describing, explaining, and optimizing intraindividual change and interindividual differences in such change and, as such, requires longitudinal research. The selection of the appropriate type of longitudinal design requires selecting the option that best addresses the theoretical questions asked about…

  16. Cultural Orientation Trajectories and Substance Use: Findings from a Longitudinal Study of Mexican-Origin Youth

    ERIC Educational Resources Information Center

    Cruz, Rick A.; King, Kevin M.; Cauce, Ana M.; Conger, Rand D.; Robins, Richard W.

    2017-01-01

    Cultural adaptation may influence Latino youth substance use (SU) development, yet few longitudinal studies have examined cultural change over time and adolescent SU outcomes. Using longitudinal data collected annually across ages 10-16 from 674 Mexican-origin youth (50% female), the authors characterized cultural adaptation patterns for language…

  17. A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II

    SciTech Connect

    Bane, Karl

    2015-09-23

    The Linac Coherent Light Source (LCLS) at SLAC, the world’s first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures, to allow for high rep-rate operation. It is envisioned that eventually the LCLS-II will be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2 K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3—where the peak current is highest—the power radiated by the bunches in the CMs is estimated at 13.8 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In the present work we calculate the multi-bunch wakefields excited in a CM of LCLS-II, in order to estimate the probability of the beam losing a given amount of power. Along theway, we find some interesting properties of the resonant interaction. In detail, we begin this report by finding the wakes experienced by bunches far back in the bunch train. Then we present a complementary approach that calculates the field amplitude excited in steady-state by a train of bunches, and show that the two approaches agree. Next we obtain the properties of the 450 longitudinal HOMs that cover the range 3–5 GHz in the CMs of LCLS-II, where we include the effects of the inter-CM ceramic dampers. At the end we apply our method using these modes.

  18. Exercise and depressive symptoms in adolescents: a longitudinal cohort study.

    PubMed

    Toseeb, Umar; Brage, Soren; Corder, Kirsten; Dunn, Valerie J; Jones, Peter B; Owens, Matthew; St Clair, Michelle C; van Sluijs, Esther M F; Goodyer, Ian M

    2014-12-01

    Physical activity (PA) may have a positive effect on depressed mood. However, whether it can act as a protective factor against developing depressive symptoms in adolescence is largely unknown. To investigate the association between objectively measured PA and depressive symptoms during 3 years of adolescence. We performed a longitudinal study between November 1, 2005, and January 31, 2010, of a community-based sample from Cambridgeshire and Suffolk, United Kingdom, that included 736 participants (mean [SD] age, 14.5 years [6 months]). The follow-up period was approximately 3 years after baseline (the ROOTS study). Linear regression models were fitted using physical activity energy expenditure (PAEE) and moderate and vigorous physical activity (MVPA) as the predictors and depressive symptoms as the outcome variable. Binomial logistic regression models were also fitted using PAEE and MVPA as the predictors and clinical depression as the outcome measure. Exercise. Individually calibrated heart rate and movement sensing were used to measure PA at baseline only. Physical activity summary measures included total PAEE and time spent in MVPA. These measures were divided into weekend and weekday activity. All participants also completed the Mood and Feelings Questionnaire, a self-report measure of current depressive symptoms, and took part in a Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version interview at baseline and 3 years later. Depressive symptoms at 3-year follow-up were not significantly predicted by any of the 4 PA measures at baseline: weekend MVPA (unstandardized β = 0.02; 95% CI, -0.15 to 0.20; P = .79), weekday MVPA (β = 0.00; 95% CI, -0.17 to 0.17; P = .99), weekend PAEE (β = 0.03; 95% CI, -0.14 to 0.20; P = .75), and weekday PAEE (β = -0.03; 95% CI, -0.20 to 0.14; P = .71). This was also true for major depressive disorder diagnoses at follow-up: weekend MVPA (odds ratio

  19. A Longitudinal Study of Accounting Students' Ethical Judgement Making Ability

    ERIC Educational Resources Information Center

    Mohamed Saat, Maisarah; Porter, Stacey; Woodbine, Gordon

    2012-01-01

    This paper reports the effect of a moral education programme on the ethical judgement making ability of university students. The programme comprises two forms of intervention: a dedicated ethics course and subsequent practical training. A total of 113 accounting students from six Malaysian universities participated in a longitudinal study…

  20. Consistency and Development of Prosocial Dispositions: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Eisenberg, Nancy; Guthrie, Ivanna K.; Murphy, Bridget C.; Shepard, Stephanie A.; Cumberland, Amanda; Carol, Gustavo

    1999-01-01

    Examined consistency in prosocial dispositions, using longitudinal data from preschool through early adulthood. Found that spontaneous prosocial behavior observed in preschools predicted actual prosocial behavior, other- and self-reported prosocial behavior, self-reported sympathy, and perspective taking in childhood to early adulthood. Prosocial…