Fundamental noise limitations to supercontinuum generation in microstructure fiber

Broadband noise on supercontinuum spectra generated in microstructure fiber is shown to lead to amplitude fluctuations as large as 50 % for certain input laser pulse parameters. We study this noise using both experimental measurements and numerical simulations with a generalized stochastic nonlinear Schroedinger equation, finding good quantitative agreement over a range of input pulse energies and chirp values. This noise is shown to arise from nonlinear amplification of two quantum noise inputs: the input pulse shot noise and the spontaneous Raman scattering down the fiber.Comment: 16 pages with 6 figure

Optical Frequency Comb Generation based on Erbium Fiber Lasers

Citation: Droste, S., Ycas, G., Washburn, B. R., Coddington, I., & Newbury, N. R. (2016). Optical Frequency Comb Generation based on Erbium Fiber Lasers. Nanophotonics, 5(2), 196-213. doi:10.1515/nanoph-2016-0019Optical frequency combs have revolutionized optical frequency metrology and are being actively investigated in a number of applications outside of pure optical frequency metrology. For reasons of cost, robustness, performance, and flexibility, the erbium fiber laser frequency comb has emerged as the most commonly used frequency comb system and many different designs of erbium fiber frequency combs have been demonstrated. We review the different approaches taken in the design of erbium fiber frequency combs, including the major building blocks of the underlying mode-locked laser, amplifier, supercontinuum generation and actuators for stabilization of the frequency comb

Spin-axis relaxation in spin-exchange collisions of alkali atoms

We present calculations of spin-relaxation rates of alkali-metal atoms due to the spin-axis interaction acting in binary collisions between the atoms. We show that for the high-temperature conditions of interest here, the spin relaxation rates calculated with classical-path trajectories are nearly the same as those calculated with the distorted-wave Born approximation. We compare these calculations to recent experiments that used magnetic decoupling to isolate spin relaxation due to binary collisions from that due to the formation of triplet van-der-Waals molecules. The values of the spin-axis coupling coefficients deduced from measurements of binary collision rates are consistent with those deduced from molecular decoupling experiments. All the experimental data is consistent with a simple and physically plausible scaling law for the spin-axis coupling coefficients.Comment: text+1 figur

Through the looking glass: public and professional perspectives on patient-centred professionalism in modern-day community pharmacy

This paper presents five consultation workshops with 29 community pharmacists, stakeholders and patients that examined "patient-centred professionalism" in terms of pharmacists' working day and environment. The concept is ill-defined in both medical and pharmacy literature and the study aimed to clarify the situated nature of the term for patients and health professionals across settings. Workshops were supported by bio-photographic datasets of "in-situ" practice and Nominal Group Work. The thematic content analyses led to the following aspects: building caring relationships; managing external forces; the effects of space and environment, and different roles and expectations. The study reveals how patient-centred professionalism cannot be defined in any singular or stationary sense, but should be seen as a "moveable feast", best understood through everyday examples of practice and interaction, in relation to whose experience is being expressed, and whose needs considered. The phrase is being mobilised by a whole set of interests and stakeholders to reshape practice, the effect of which remains both uncertain and contested. Whilst patients prioritise a quick and efficient dispensing service from knowledgeable pharmacists, pharmacists rail against increasing public demands and overtly formalised consultations that take them away from the dispensary where the defining aspects of their professionalism lie. URN: urn:nbn:de:0114-fqs100177Unser Beitrag stellt die Ergebnisse aus insgesamt fünf Workshops mit 29 Apotheker/innen, Patient/innen und weiteren Akteuren vor, die sich mit "Patient/innen-zentrierter Versorgung" in der Alltagsarbeit und -umgebung von Apotheker/innen befassten. Dieses Konzept ist in der relevanten Literatur nur ungenügend definiert, und ein Ziel der Studie war, dessen situativen Charakter für Patient/innen und im Gesundheitssystem Tätige zu präzisieren. In den Workshops kamen Fotografien aus der Alltagspraxis und spezifische Gruppenarbeitsverfahren zum Einsatz. Im Beitrag werden nach einer Information über die Teilnehmenden die Ergebnisse der thematischen Inhaltsanalyse zusammengefasst, die die folgenden Schwerpunkte erbrachte: Aufbau von Beziehungen mit Patient/innen, Umgang mit externen Einflussgrößen, (räumliche) Umgebungseffekte und Unterschiedlichkeit von Rollen und Erwartungen. Die Ergebnisse zeigen, dass "Patient/innen-zentrierte Versorgung" nicht in einer singulären oder statischen Weise definiert werden kann, sondern am besten nachvollziehbar ist entlang von Beispielen aus der Alltagspraxis und von Alltagsinteraktionen, abhängig davon, wessen Erfahrungen ausgedrückt und wessen Bedürfnisse im Fokus stehen sollen. Dieses Verständnis trifft für eine Vielzahl an Interessen und Akteuren zu, um Praxis zu rekonzeptualisieren, die zugleich auch fragil und strittig ist: Während Patient/innen möglichst schnelle und effektive Dienstleistungen von sachkundigen Apotheker/innen erwarten, wenden diese sich gegen wachsende öffentliche Ansprüche und zunehmend formalisierte Beratungen, die sie von der Art von Arbeit entfernen, die Kern ihrer professionellen Identität ist. URN: urn:nbn:de:0114-fqs100177Este documento presenta cinco talleres de consulta con 29 farmacéuticos comunitarios, los promotores y los pacientes que examinaron "el profesionalismo centrado en el paciente" en términos de jornada de trabajo de los farmacéuticos y el medio ambiente. El concepto está mal definido, tanto en la literatura médica y farmacéutica, y el estudio tuvo como objetivo aclarar la naturaleza situada del término en los pacientes y en los profesionales de la salud en diferentes contextos. Los talleres fueron apoyados por conjuntos de datos bio-fotográficas de la práctica "in-situ" y el Grupo Nominal de Trabajo. El análisis de contenido temático c a los siguientes aspectos: creación de relaciones afectuosas; gestión de fuerzas externas; los efectos del espacio y el medio ambiente, y roles y expectativas diferentes. El estudio revela cómo el profesionalismo centrado en el paciente no puede definirse en un sentido singular o estacional, pero debe ser visto como “fiesta ambulante”, mejor entendida a través de ejemplos de la vida diaria y la interacción, en relación con cuya experiencia se expresa, y cuyas necesidades considera. La frase está siendo movilizada por un juego entero de intereses y de los promotores para reformar la práctica, el efecto del cual sigue siendo incierto y puesto en debate. Mientras los pacientes priorizan un servicio de distribución rápido y eficiente de parte de farmacéuticos bien informados, los farmacéuticos critican severamente las crecientes demandas públicas y abiertamente formalizan consultas que se los llevan lejos del dispensario donde radican los aspectos de definición de su profesionalismo. URN: urn:nbn:de:0114-fqs10017

Spectroscopy of the Methane {\nu}3 Band with an Accurate Mid-Infrared Coherent Dual- Comb Spectrometer

We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 \mu m. The amplitude and phase spectra of the P, Q, and partial R-branch of the methane {\nu}3 band are measured at 25 MHz to 100 MHz point spacing with ~kHz resolution and a signal-to-noise ratio of up to 3500. A fit of the absorbance and phase spectra yield the center frequency of 132 rovibrational lines. The systematic uncertainty is estimated to be 300 kHz, which is 10-3 of the Doppler width and a tenfold improvement over Fourier transform spectroscopy. These data are the first high- accuracy molecular spectra obtained with a direct comb spectrometer.Comment: journal articl

Relaxation Processes in Clouds of Trapped Bosons above the Bose-Einstein Condensation Temperature

We present a unified account of damping of low-lying collective modes and of relaxation of temperature anisotropies in a trapped Bose gas in the collisionless regime. By means of variational techniques, we show that the relaxation times for the two situations are closely related to the simplest variational estimate of the viscous relaxation time. We derive rather precise theoretical expressions for the characteristic relaxation times, and compare our results with experiment.Comment: 4 pages, revte

Magnetoresistance and magnetic breakdown in the quasi-two-dimensional conductors (BEDT-TTF)2_2MHg(SCN)4_4[M=K,Rb,Tl]

The magnetic field dependence of the resistance of (BEDT-TTF)$_2$MHg(SCN)$_4$[M=K,Rb,Tl] in the density-wave phase is explained in terms of a simple model involving magnetic breakdown and a reconstructed Fermi surface. The theory is compared to measurements in pulsed magnetic fields up to 51 T. The value implied for the scattering time is consistent with independent determinations. The energy gap associated with the density-wave phase is deduced from the magnetic breakdown field. Our results have important implications for the phase diagram.Comment: 5 pages, RevTeX + epsf, 3 figures. To appear in Physical Review B, Rapid Communications, September 15, 199

Coherent Dual Comb Spectroscopy at High Signal to Noise

Two frequency combs can be used to measure the full complex response of a sample in a configuration which can be alternatively viewed as the equivalent of a dispersive Fourier transform spectrometer, infrared time domain spectrometer, or a multiheterodyne laser spectrometer. This dual comb spectrometer retains the frequency accuracy and resolution inherent to the comb sources. We discuss, in detail, the specific design of our coherent dual-comb spectrometer and demonstrate the potential of this technique by measuring the first overtone vibration of hydrogen cyanide, centered at 194 THz (1545 nm). We measure the fully normalized, complex response of the gas over a 9 THz bandwidth at 220 MHz frequency resolution yielding 41,000 resolution elements. The average spectral signal-to-noise ratio (SNR) is 2,500 for both the fractional absorption and the phase, with a peak SNR of 4,000 corresponding to a fractional absorption sensitivity of 0.025% and phase sensitivity of 250 microradians. As the spectral coverage of combs expands, this dual-comb spectroscopy could provide high frequency accuracy and resolution measurements of a complex sample response across a range of spectral regions.Comment: 18 pages, 8 figures updated references, updated to match publication versio

A qualitative account of young people's experiences of alcohol screening and brief interventions in schools: SIPS Jr-HIGH trial findings.

BACKGROUND: The United Kingdom (UK) has seen a decrease in the number of young people drinking alcohol. However, the UK prevalence of underage drinking still ranks amongst the highest in Western Europe. Whilst there is a wealth of evidence reporting on the effectiveness of both primary, and secondary interventions, there are few reports of the experiences of young people who receive them. METHODS: The present study reports findings from interviews with 33 young people who were involved in an alcohol screening and brief intervention randomized controlled trial in schools in England. All interviews were analysed using inductive applied thematic analysis. RESULTS: Three major themes were identified following the analysis process: 1) drinking identities and awareness of risk; 2) access to support and advice in relation to alcohol use; and 3) appraisal of the intervention and potential impact on alcohol use. CONCLUSIONS: There appeared to be a reluctance from participants to describe themselves as someone who drinks alcohol. Furthermore, those who did drink alcohol often did so with parental permission. There was variation amongst participants as to how comfortable they felt talking about alcohol issues with school staff. Overall participants felt the intervention was useful, but would be better suited to 'heavier' drinkers