Nonlocal explanation of stationary and nonstationary regimes in cascaded soliton pulse compression

We study soliton pulse compression in materials with cascaded quadratic nonlinearities, and show that the group-velocity mismatch creates two different temporally nonlocal regimes. They correspond to what is known as the stationary and nonstationary regimes. The theory accurately predicts the transition to the stationary regime, where highly efficient pulse compression is possible.Comment: 3 pages, 2 figures, published verison in Optics Letters. Contains revised equations, including an updated mode

Scaling laws for soliton pulse compression by cascaded quadratic nonlinearities

We present a detailed study of soliton compression of ultra-short pulses based on phase-mismatched second-harmonic generation (\textit{i.e.}, the cascaded quadratic nonlinearity) in bulk quadratic nonlinear media. The single-cycle propagation equations in the temporal domain including higher-order nonlinear terms are presented. The balance between the quadratic (SHG) and the cubic (Kerr) nonlinearity plays a crucial role: we define an effective soliton number -- related to the difference between the SHG and the Kerr soliton numbers -- and show that it has to be larger than unity for successful pulse compression to take place. This requires that the phase mismatch be below a critical level, which is high in a material where the quadratic nonlinearity dominates over the cubic Kerr nonlinearity. Through extensive numerical simulations we find dimensionless scaling laws, expressed through the effective soliton number, which control the behaviour of the compressed pulses. These laws hold in the stationary regime, in which group-velocity mismatch effects are small, and they are similar to the ones observed for fiber soliton compressors. The numerical simulations indicate that clean compressed pulses below two optical cycles can be achieved in a $\beta$-barium borate crystal at appropriate wavelengths, even for picosecond input pulses.Comment: 11 pages, 8 figures, resubmitted version, to appear in October issue of J. Opt. Soc. Am. B. Substantially revised, updated mode

Limits to compression with cascaded quadratic soliton compressors

We study cascaded quadratic soliton compressors and address the physical mechanisms that limit the compression. A nonlocal model is derived, and the nonlocal response is shown to have an additional oscillatory component in the nonstationary regime when the group-velocity mismatch (GVM) is strong. This inhibits efficient compression. Raman-like perturbations from the cascaded nonlinearity, competing cubic nonlinearities, higher-order dispersion, and soliton energy may also limit compression, and through realistic numerical simulations we point out when each factor becomes important. We find that it is theoretically possible to reach the single-cycle regime by compressing high-energy fs pulses for wavelengths $\lambda=1.0-1.3 \mu{\rm m}$ in a $\beta$-barium-borate crystal, and it requires that the system is in the stationary regime, where the phase mismatch is large enough to overcome the detrimental GVM effects. However, the simulations show that reaching single-cycle duration is ultimately inhibited by competing cubic nonlinearities as well as dispersive waves, that only show up when taking higher-order dispersion into account.Comment: 16 pages, 5 figures, submitted to Optics Expres

The White Mountains : handbook for travellers : a guide to the peaks, passes, and ravines of the White Mountains of New Hampshire, and to the adjacent railroads, highways, and villages; with the lakes and mountains of western Maine; also lake Winnepesaukee, and the upper Connecticut valley.

With six maps and six panoramashttps://scholars.unh.edu/geology_books/1006/thumbnail.jp

Ariel 6 measurements of ultra-heavy cosmic ray fluxes in the region 34 or = Z or = 48

The Ariel VI satellite was launched by NASA on a Scout rocket on 3rd June 1979 from Wallops Island, Virginia, USA, into a near circular 625 km orbit inclined at 55 deg. It carried a spherical cosmic ray detector designed by a group from Bristol University. A spherical aluminum vessel of diameter 75 cm contains a gas scintillation mixture and a thin spherical shell of Pilot 425 plastic, and forms a single optical cavity viewed by 16 photomultipliers. Particle tracks through the detector may be characterized by their impact parameter p and by whether or not they pass through the cup of plastic scintillator placed between the sphere and the spacecraft body (referred to below as the Anti-Coincidence Detector or ACD). Individual particle charges are determined by separately measuring the gas scintillation and the Cerenkov emission from the plastic shell. This is possible because of the quite different distribution in time of these emissions

The White Mountains : a handbook for travellers : a guide to the peaks, passes, and ravines of the White Mountains of New Hampshire, and to the adjacent railroads, highways, and villages; with the lakes and mountains or western Maine; also, lake Winnepesaukee, and the upper Connecticut valley, With six maps and six panoramas.

Cover title: Osgood\u27s White Mountains.; Includes index

Treatment of multiple sclerosis - relationship between vitamin d and interferon β-1b

There are many reports suggesting an association between vitamin D status and both the development of multiple sclerosis (MS) and its course. This relationship and the effects of vitamin D and interferon {beta}-1b (IFN{beta}-1b) in the treatment of patients are reviewed in the BEtaferon/ Betaseron in Newly Emerging multiple sclerosis For Initial Treatment (BENEFIT) and the Betaferon/Betaseron Efficacy Yielding Outcomes of a New Dose in multiple sclerosis (BEYOND) studies. In the BENEFIT study the average serum 25-hydroxyvitamin D (25[OH]D) levels strongly predicted MS disease activity and progression. The probability of clinically definite MS (CDMS) and magnetic resonance imaging (MRI) activity was lower in these clinically isolated syndrome (CIS) patients with 25(OH)D levels >=50 nmol/L and in those starting with IFN{beta}-1b. Furthermore, there was a beneficial effect on relapse rate, occurrence of new active MRI lesions and disease progression for a 50 nmol/L increase in 25(OH)D levels. Similarly, in relapsing-remitting (RR) MS patients from the BEYOND study serum 25(OH)D levels were inversely associated with MRI markers of MS activity. Genetic analysis of patients from these studies indicated that there may be a benefit in monitoring and managing vitamin D levels in early MS patients treated with IFN{beta}-1b and a cumulative number of risk alleles predict lower 25(OH)D levels in CIS and RRMS patients. Further studies have suggested that some of the IFN{beta}-1b therapeutic effects on relapse could be mediated through modulation of vitamin D metabolism. Thus, there seems to be a benefit on clinical and MRI measures if patients are treated with both vitamin D and IFN{beta}-1b. There is a need to further evaluate this effect in clinical trials. The relationship between vitamin D and MS disease activity along with the effects of vitamin D and IFN{beta}-1b in the treatment of MS patients is reviewed

Optical Cherenkov radiation by cascaded nonlinear interaction: an efficient source of few-cycle energetic near- to mid-IR pulses

When ultrafast noncritical cascaded second-harmonic generation of energetic femtosecond pulses occur in a bulk lithium niobate crystal optical Cherenkov waves are formed in the near- to mid-IR. Numerical simulations show that the few-cycle solitons radiate Cherenkov (dispersive) waves in the \lambda=2.2-4.5\mic range when pumping at \lambda_1=1.2-1.8\mic. The exact phase-matching point depends on the soliton wavelength, and we show that a simple longpass filter can separate the Cherenkov waves from the solitons. The Cherenkov waves are born few-cycle with an excellent Gaussian pulse shape, and the conversion efficiency is up to 25%. Thus, optical Cherenkov waves formed with cascaded nonlinearities could become an efficient source of energetic near- to mid-IR few-cycle pulses.Comment: Extended version of Nonlinear Optics 2011 contribution http://www.opticsinfobase.org/abstract.cfm?URI=NLO-2011-NTuA7. Submitted for Optics Express special issue for NLO conferenc

Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations

The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the T sub min region and ground based magnetogram and He I 10830 A images

Implementing Training and Skills Investment Policy for Effective Performance of Managerial Emergency Unit; Study in Sub-Saharan Africa

The healthcare system of every environment is critical and sensitive, therefore it is important to have healthcare personnels that are up to date in their knowedge of the field, being expert and professionals in this field is not enough due to the dynamic nature of the environment, having impementation policy to acquire often and updated skills and training can not be over emphasize. The challenges encountered during this research is the poor management system and lack of implementation of some important policy as such, hence this research finds the indepth of issues arising due to lack of skills and adequate training, in Nigeria there are challenges with the management of the emergency units of the healthcare organizations; which was observed from the high mortality rate encountered at the emergency unit, lack of skills and training to render best services, patients leaving before being attended to due to high traffic inflow into the emergency unit andhealthcare givers poor turn around time to address emergency situations. Implementing the skills and training policy for often participation in its activities is a situation tourgently address so as to lead to resolution of issues arising, hence it is not enough to have qualify healthcare givers in the hospital without frequent training and skills acquisation policy implemented, to enable healthcare givers to continuely update their learning and knowledge of the field and cope with new diseases and infections arising as seen in the results, concluding with recommendations and advise on further studies