8,380 research outputs found
Mindfulness, empowerment and feminist identity development as protective factors against women developing body image dissatisfaction
Four wave mixing with self-phase matching due to collective atomic recoil
We describe a method for non-degenerate four-wave mixing in a cold sample of
4-level atoms. An integral part of the four-wave mixing process is a
collective instability which spontaneously generates a periodic density
modulation in the cold atomic sample with a period equal to half of the
wavelength of the generated high-frequency optical field. Due to the generation
of this density modulation, phase-matching between the pump and scattered
fields is not a necessary initial condition for this wave-mixing process to
occur, rather the density modulation acts to "self phase-match" the fields
during the course of the wave-mixing process. We describe a one-dimensional
model of this process, and suggest a proof-of-principle experiment which would
involve pumping a sample of cold Cs atoms with three infra-red pump fields to
produce blue light.Comment: to appear in Physical Review Letter
Inducing strong density modulation with small energy dispersion in particle beams and the harmonic amplifier free electron laser
We present a possible method of inducing a periodic density modulation in a particle beam with little increase in the energy dispersion of the particles. The flow of particles in phase space does not obey Liouville's Theorem. The method relies upon the Kuramoto-like model of collective synchronism found in free electron generators of radiation, such as Cyclotron Resonance Masers and the Free Electron Laser. For the case of an FEL interaction, electrons initially begin to bunch and emit radiation energy with a correlated energy dispersion which is periodic with the FEL ponderomotive potential. The relative phase between potential and particles is then changed by approximately 180 degrees. The particles continue to bunch, however, there is now a correlated re-absorption of energy from the field. We show that, by repeating this relative phase change many times, a significant density modulation of the particles may be achieved with only relatively small energy dispersion. A similar method of repeated relative electron/radiation phase changes is used to demonstrate supression of the fundamental growth in a high gain FEL so that the FEL lases at the harmonic only
Uniform Commercial Code -- Applicability of Section 3-405 to Federal Commercial Paper -- Padded Payroll Exception -- United States v. Bank of America Nat\u27l Trust and Savings Ass\u27n
L-J, Inc. v. Bituminous Fire & Marine Insurance Co.: In Determining Coverage Under Commercial General Liability Policies, Should Policy Language or Public Policy Control?
Objective measurement of habitual sedentary behavior in pre-school children: comparison of activPAL with actigraph monitors
The Actigraph is well established for measurement of both physical activity and
sedentary behavior in children. The activPAL is being used increasingly in children, though with no published evidence on its use in free-living children to date. The present study compared the two monitors in preschool children. Children (n 23) wore both monitors simultaneously during waking hours for 5.6d and 10h/d. Daily mean percentage of time sedentary (nontranslocation of the trunk) was 74.6 (SD 6.8) for the Actigraph and 78.9 (SD 4.3) for activPAL. Daily mean percentage of time physically active (light intensity physical activity plus MVPA) was 25.4 (SD 6.8) for the Actigraph and 21.1 (SD 4.3) for the activPAL. Bland-Altman tests and paired t tests suggested small but statistically significant differences between the two monitors. Actigraph and activPAL estimates of sedentary behaviour and physical activity in young children are similar at a group level
Warm springs national fish hatchery intake improvements
The Warm Springs National Fish Hatchery located in Warm Springs Oregon, is hampered with many issues that impact its effectiveness. In an effort to improve the effectiveness of the hatchery, United States Fish and Wildlife Services (USFWS) has expressed interest in modifying the existing intake to address a number of specific concerns. Five specific objectives have been identified to define the overall project scope. USFWS desires to provide a means to prevent frazil ice from forming on and around the hatchery intake screens, prevent sediment from collecting behind the weir and entering the hatchery intake, provide effective hatchery screening to prevent sediment, debris, and fish from entering the hatchery intake, decrease intake water temperatures during summer months, improve the intake screen cleaning system, and provide a means for effective water quality treatment to limit spikes in turbidity and therefore improving the effectiveness of the existing ultraviolet treatment.
Concept level improvements were developed to address the objectives. Site visits, interviews with hatchery staff, water quality sampling, hydrologic and hydraulic analysis were completed and record construction drawings of the hatchery were reviewed to confirm concept level improvement feasibility.
Three concept level design alternatives were developed to address the first four objectives while only preliminary water quality sampling was conducted so that separate concepts could be developed in the future to address the fifth objective, effectiveness of the existing sand filters. The concepts developed and evaluated included installation of rotary drum screens or vertical fixed plate screens to replace the existing static drum screens. In addition, the concepts included an a la carte of other options that address the objectives. Those a la carte items include; construction of a rock groin structure, weir improvements to provide an adjustable spillway, and miscellaneous utility upgrades.
From this analysis, Concept 3 - relocating the hatchery intake upstream was identified as most likely to address the objectives and is feasible given the site constraints. More analysis is needed before a recommendation can be made including collection of in-stream water temperature data and a quantification of the amount of sediment expected to accumulate near the proposed intake structure. However, it is also recommended that additional and consistent operation and maintenance at the existing intake could also provide significant improvements to address the objectives in the short term
From Default Probabilities To Credit Spreads: Credit Risk Models Do Explain Market Prices
Credit risk models like Moodyâs KMV are now well established in the market and give bond managers reliable estimates of default probabilities for individual firms. Until now it has been hard to relate those probabilities to the actual credit spreads observed on the market for corporate bonds. Inspired by the existence of scaling laws in financial markets by Dacorogna et al. (2001) and Di Matteo et al. (2005) deviating from the Gaussian behavior, we develop a model that quantitatively links those default probabilities to credit spreads (market prices). The main input quantities to this study are merely industry yield data of different times to maturity and expected default frequencies (EDFs) of Moodyâs KMV. The empirical results of this paper clearly indicate that the model can be used to calculate approximate credit spreads (market prices) from EDFs, independent of the time to maturity and the industry sector under consideration. Moreover, the model is effective in an out-of-sample setting, it produces consistent results on the European bond market where data are scarce and can be adequately used to approximate credit spreads on the corporate level.
An extended model of the quantum free-electron laser
Previous models of the quantum regime of operation of the Free Electron Laser
(QFEL) have performed an averaging and the application of periodic boundary
conditions to the coupled Maxwell - Schrodinger equations over short, resonant
wavelength intervals of the interaction. Here, an extended, one-dimensional
model of the QFEL interaction is presented in the absence of any such averaging
or application of periodic boundary conditions, the absence of the latter
allowing electron diffusion processes to be modeled throughout the pulse. The
model is used to investigate how both the steady-state (CW) and pulsed regimes
of QFEL operation are affected. In the steady-state regime it is found that the
electrons are confined to evolve as a 2-level system, similar to the previous
QFEL models. In the pulsed regime Coherent Spontaneous Emission (CSE) due to
the shape of the electron pulse current distribution is shown to be present in
the QFEL regime for the first time. However, unlike the classical case, CSE in
the QFEL is damped by the effects of quantum diffusion of the electron
wavefunction. Electron recoil from the QFEL interaction can also cause a
diffusive drift between the recoiled and non-recoiled parts of the electron
pulse wavefunction, effectively removing the recoiled part from the primary
electron-radiation interaction.Comment: Submitted to Optics Expres
Freezing line of the Lennard-Jones fluid: a Phase Switch Monte Carlo study
We report a Phase Switch Monte Carlo (PSMC) method study of the freezing line
of the Lennard-Jones (LJ) fluid. Our work generalizes to soft potentials the
original application of the method to hard sphere freezing, and builds on a
previous PSMC study of the LJ system by Errington (J. Chem. Phys. {\bf 120},
3130 (2004)). The latter work is extended by tracing a large section of the
Lennard-Jones freezing curve, the results for which we compare to a previous
Gibbs-Duhem integration study. Additionally we provide new background regarding
the statistical mechanical basis of the PSMC method and extensive
implementation details.Comment: 18 pages, 6 figure
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