Ultra-sensitive surface absorption spectroscopy using sub-wavelength diameter optical fibers

The guided modes of sub-wavelength diameter air-clad optical fibers exhibit a pronounced evanescent field. The absorption of particles on the fiber surface is therefore readily detected via the fiber transmission. We show that the resulting absorption for a given surface coverage can be orders of magnitude higher than for conventional surface spectroscopy. As a demonstration, we present measurements on sub-monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules at ambient conditions, revealing the agglomeration dynamics on a second to minutes timescale.Comment: 4 pages, Fig.1a corrected y-axis, p.2 minor text changes to facilitate the understanding of eq. 4 and

Cold Atom Physics Using Ultra-Thin Optical Fibers: Light-Induced Dipole Forces and Surface Interactions

The strong evanescent field around ultra-thin unclad optical fibers bears a high potential for detecting, trapping, and manipulating cold atoms. Introducing such a fiber into a cold atom cloud, we investigate the interaction of a small number of cold Caesium atoms with the guided fiber mode and with the fiber surface. Using high resolution spectroscopy, we observe and analyze light-induced dipole forces, van der Waals interaction, and a significant enhancement of the spontaneous emission rate of the atoms. The latter can be assigned to the modification of the vacuum modes by the fiber.Comment: 4 pages, 4 figure

Particle contact laws and their properties for simulation of fluid-sediment interaction with coupled SPH-DEM model

The transport of sediment due to the interaction of fluid and solids is a prevalent geophysical process. The detailed modelling of the interaction between the fluid and the sediment particles is still a challenging task. In the present study we model the fluid phase by smoothed particle hydrodynamics (SPH) using the classical approach where the fluid is assumed to be weakly compressible. The sediment, in terms of solid spheres made of granite, is modelled by the discrete element method (DEM). Both of them are meshfree particle methods but SPH is a continuum approach and DEM describes the motion and interaction of discrete solid objects. The interaction between SPH and DEM particles is modelled as particle-to-particle contact in combination with a boundary condition at the solid interface. Therefore, a contact law is used to capture the collision process and to ensure balancing of collision forces. In doing so, two contact types have to be modelled, i.e. sediment-sediment and fluid-sediment. The approach and properties these contact types are presented in detail. Advantages and drawbacks of the approaches are discussed based on examples

A Nanofiber-Based Optical Conveyor Belt for Cold Atoms

We demonstrate optical transport of cold cesium atoms over millimeter-scale distances along an optical nanofiber. The atoms are trapped in a one-dimensional optical lattice formed by a two-color evanescent field surrounding the nanofiber, far red- and blue-detuned with respect to the atomic transition. The blue-detuned field is a propagating nanofiber-guided mode while the red-detuned field is a standing-wave mode which leads to the periodic axial confinement of the atoms. Here, this standing wave is used for transporting the atoms along the nanofiber by mutually detuning the two counter-propagating fields which form the standing wave. The performance and limitations of the nanofiber-based transport are evaluated and possible applications are discussed

Nanofiber Fabry-Perot microresonator for non-linear optics and cavity quantum electrodynamics

We experimentally realize a Fabry-Perot-type optical microresonator near the cesium D2 line wavelength based on a tapered optical fiber, equipped with two fiber Bragg gratings which enclose a sub-wavelength diameter waist. Owing to the very low taper losses, the finesse of the resonator reaches F = 86 while the on-resonance transmission is T = 11 %. The characteristics of our resonator fulfill the requirements of non-linear optics and cavity quantum electrodynamics in the strong coupling regime. In combination with its demonstrated ease of use and its advantageous mode geometry, it thus opens a realm of applications.Comment: 4 pages, 3 figure

Parents' preferences for the organisation of long-term follow-up of childhood cancer survivors

Parents take an important role in follow-up of young cancer survivors. We aimed to investigate (1) parents' preferences for organisation of follow-up (including content, specialists involved and models of care), and (2) parents' and children's characteristics predicting preference for generalist vs. specialist-led follow-up. We sent a questionnaire to parents of childhood cancer survivors aged 11-17 years. We assessed on a 4-point Likert scale (1-4), parents' preferences for organisation of long-term follow-up. Proposed models were: telephone/questionnaire, general practitioner (GP) (both categorised as generalist for regression analysis); and paediatric oncologist, medical oncologist or multidisciplinary team (MDT) (categorised as specialists). Of 284 contacted parents, 189 responded (67%). Parents welcomed if visits included checking for cancer recurrence (mean = 3.89), late effects screening (mean = 3.79), taking patients seriously (mean = 3.86) and competent staff (mean = 3.85). The preferred specialists were paediatric oncologists (mean = 3.73). Parents valued the paediatric oncologist model of care (mean = 3.49) and the MDT model (mean = 3.14) highest. Parents of children not attending clinic-based follow-up (OR = 2.97, p = .009) and those visiting a generalist (OR = 4.23, p = .007) favoured the generalist-led model. Many parents preferred a clinic-based model of follow-up by paediatric oncologists or a MDT. However, parents also valued the follow-up care model according to which their child is followed up

Employment Situation of Parents of Long-Term Childhood Cancer Survivors

BACKGROUND: Taking care of children diagnosed with cancer affects parents' professional life. The impact in the long-term however, is not clear. We aimed to compare the employment situation of parents of long-term childhood cancer survivors with control parents of the general population, and to identify clinical and socio-demographic factors associated with parental employment. METHODS: As part of the Swiss Childhood Cancer Survivor Study, we sent a questionnaire to parents of survivors aged 5-15 years, who survived ≥5 years after diagnosis. Information on control parents of the general population came from the Swiss Health Survey (restricted to men and women with ≥1 child aged 5-15 years). Employment was categorized as not employed, part-time, and full-time employed. We used generalized ordered logistic regression to determine associations with clinical and socio-demographic factors. Clinical data was available from the Swiss Childhood Cancer Registry. RESULTS: We included 394 parent-couples of survivors and 3'341 control parents (1'731 mothers; 1'610 fathers). Mothers of survivors were more often not employed (29% versus 22%; ptrend = 0.007). However, no differences between mothers were found in multivariable analysis. Fathers of survivors were more often employed full-time (93% versus 87%; ptrend = 0.002), which remained significant in multivariable analysis. Among parents of survivors, mothers with tertiary education (OR = 2.40, CI:1.14-5.07) were more likely to be employed. Having a migration background (OR = 3.63, CI: 1.71-7.71) increased the likelihood of being full-time employed in mothers of survivors. Less likely to be employed were mothers of survivors diagnosed with lymphoma (OR = 0.31, CI:0.13-0.73) and >2 children (OR = 0.48, CI:0.30-0.75); and fathers of survivors who had had a relapse (OR = 0.13, CI:0.04-0.36). CONCLUSION: Employment situation of parents of long-term survivors reflected the more traditional parenting roles. Specific support for parents with low education, additional children, and whose child had a more severe cancer disease could improve their long-term employment situation