Proton acceleration by irradiation of isolated spheres with an intense laser pulse

We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2-3 x 10(20) W cm(-2). With a laser focal spot size of 10 mu m full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 mu m. Maximum proton energies of similar to 25 MeV are achieved for targets matching the focal spot size of 10 mu m in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.DFG via the Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) Transregio SFB TR18NNSA DE-NA0002008Super-MUC pr48meIvo CermakCGC Instruments in design and realization of the Paul trap systemIMPRS-APSLMUexcellent Junior Research FundDAAD|ToIFEEuropean Union's Horizon research and innovation programme 633053Physic

Rapid Synthesis of Sub-10 nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol® 66

We report a simple one-pot method for the rapid preparation of sub-10 nm pure hexagonal (β-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol® 66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core–shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects

The Effect of Vehicle Fuel Economy Standards on Technology Adoption

Many countries are tightening passenger vehicle fuel economy standards. The literature on passenger vehicle standards has used structural models to estimate their welfare effects. This paper provides the first empirical evidence on the effects of recently tightened fuel economy standards on technology adoption. Specifically, it investigates changes in the rate and direction of technology adoption, that is, the extent to which technology is used to increase fuel economy at the expense of other vehicle attributes. We find that recent U.S. and European standards have both increased the rate of technology adoption and affected the direction of technology adoption. Producers reduced horsepower and torque compared to a counterfactual in which fuel economy standards remained unchanged. We estimate opportunity costs from reduced horsepower and torque to be of similar magnitude as the gains from fuel savings

Health services research into postnatal depression : results from a preliminary cross-cultural study

Background: Little is known about the availability and uptake of health and welfare services by women with postnatal depression in different countries. Aims: Within the context of a cross- cultural research study, to develop and test methods for undertaking quantitative health services research in postnatal depression. Method: Interviews with service planners and the collation of key health indicators were used to obtain a profile of service availability and provision. A service use questionnaire was developed and administered to a pilot sample in a number of European study centres. Results: Marked differences in service access and use were observed between the centres, including postnatal nursing care and contacts with primary care services.Rates of use of specialist services were generally low.Common barriers to access to care included perceived service quality and responsiveness. On the basis of the pilot work, a postnatal depression version of the Service Receipt Inventory was revised and finalised. Conclusions: This preliminary study demonstrated the methodological feasibility of describing and quantifying service use, highlighted the varied and often limited use of care in this population, and indicated the need for an improved understanding of the resource needs and implications of postnatal depression

The design, construction and performance of the MICE scintillating fibre trackers

This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 ElsevierCharged-particle tracking in the international Muon Ionisation Cooling Experiment (MICE) will be performed using two solenoidal spectrometers, each instrumented with a tracking detector based on diameter scintillating fibres. The design and construction of the trackers is described along with the quality-assurance procedures, photon-detection system, readout electronics, reconstruction and simulation software and the data-acquisition system. Finally, the performance of the MICE tracker, determined using cosmic rays, is presented.This work was supported by the Science and Technology Facilities Council under grant numbers PP/E003214/1, PP/E000479/1, PP/E000509/1, PP/E000444/1, and through SLAs with STFC-supported laboratories. This work was also supportedby the Fermi National Accelerator Laboratory, which is operated by the Fermi Research Alliance, under contract No. DE-AC02-76CH03000 with the U.S. Department of Energy, and by the U.S. National Science Foundation under grants PHY-0301737,PHY-0521313, PHY-0758173 and PHY-0630052. The authors also acknowledge the support of the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan

From nonwetting to prewetting: the asymptotic behavior of 4He drops on alkali substrates

We investigate the spreading of 4He droplets on alkali surfaces at zero temperature, within the frame of Finite Range Density Functional theory. The equilibrium configurations of several 4He_N clusters and their asymptotic trend with increasing particle number N, which can be traced to the wetting behavior of the quantum fluid, are examined for nanoscopic droplets. We discuss the size effects, inferring that the asymptotic properties of large droplets correspond to those of the prewetting film

Postnatal depression across countries and cultures : a qualitative study

Background: Postnatal depression seems to be a universal condition with similar rates in different countries. However, anthropologists question the cross-cultural equivalence of depression, particularly at a life stage so influenced by cultural factors. Aims: To develop a qualitative method to explore whether postnatal depression is universally recognised, attributed and described and to enquire into people’s perceptions of remedies and services for morbid states of unhappiness within the context of local services. Method: The study took place in 15 centres in 11 countries and drew on three groups of informants: focus groups with new mothers, interviews with fathers and grandmothers, and interviews with health professionals.Textual analysis of these three groups was conducted separately in each centre and emergent themes compared across centres. Results: All centres described morbid unhappiness after childbirth comparable to postnatal depression but not all saw this as an illness remediable by health interventions. Conclusions: Although the findings of this study support the universality of a morbid state of unhappiness following childbirth, they also support concerns about the cross-cultural equivalence of postnatal depression as an illness requiring the intervention of health professionals; this has implications for future research

Measurements of Flavour Dependent Fragmentation Functions in Z^0 -> qq(bar) Events

Fragmentation functions for charged particles in Z -> qq(bar) events have been measured for bottom (b), charm (c) and light (uds) quarks as well as for all flavours together. The results are based on data recorded between 1990 and 1995 using the OPAL detector at LEP. Event samples with different flavour compositions were formed using reconstructed D* mesons and secondary vertices. The \xi_p = ln(1/x_E) distributions and the position of their maxima \xi_max are also presented separately for uds, c and b quark events. The fragmentation function for b quarks is significantly softer than for uds quarks.Comment: 29 pages, LaTeX, 5 eps figures (and colour figs) included, submitted to Eur. Phys. J.

Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \lambda_3 value by \~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.