Tailoring surface topographies on solids with Mid-IR femtosecond laser pulses

Irradiation of solids with ultrashort pulses using laser sources in the mid-infrared (mid-IR) spectral region is a yet predominantly unexplored field that opens broad possibilities for efficient and precise surface texturing for a wide range of applications. In the present work, we investigate both experimentally and theoretically the impact of laser sources on the generation of surface modification related effects and on the subsequent surface patterning of metallic and semiconducting materials. Through a parametric study we correlate the mid-IR pulsed laser parameters with the onset of material damage and the formation of a variety of periodic surface structures at a laser wavelength of {\lambda}L=3200 nm and a pulse duration of {\tau}p=45 fs. Results for nickel and silicon indicate that the produced topographies comprise both high and low spatial frequency induced periodic structures, similar to those observed at lower wavelengths, while groove formation is absent. The investigation of the damage thresholds suggests the incorporation of nonlinear effects generated from three-photon-assisted excitation (for silicon) and the consideration of the role of the non-thermal excited electron population (for nickel) at very short pulse durations. The results demonstrate the potential of surface structuring with mid-IR pulses, which can constitute a systematic novel engineering approach with strong fields at long-wavelength spectral regions that can be used for advanced industrial laser applications

N N bar,Delta bar N, Delta N bar excitation for the pion propagator in nuclear matter

The particle-hole and Delta -hole excitations are well-known elementary excitation modes for the pion propagator in nuclear matter. But, the excitation also involves antiparticles, namely, nucleon-antinucleon, anti-Delta-nucleon and Delta-antinucleon excitations. These are important for high-energy momentum as well, and have not been studied before, to our knowledge. In this paper, we give both the formulas and the numerical calculations for the real and the imaginary parts of these excitations.Comment: Latex, 3 eps file

Consistent off-shell πNN\pi N N vertex and nucleon self-energy

We present a consistent calculation of half-off-shell form factors in the pion-nucleon vertex and the nucleon self-energy. Numerical results are presented. Near the on-shell point the pion-nucleon vertex is dominated by the pseudovector coupling, while at large nucleon invariant masses we find a sizable pseudoscalar admixture.Comment: 23 pages, 7 figures, REVTeX, submitted to Phys. Rev. C, replaced with corrected versio

UV continuum emission and diagnostics of hydrogen-containing non-equilibrium plasmas

For the first time the emission of the radiative dissociation continuum of the hydrogen molecule ($a^{3}\Sigma_{g}^{+} \to b^{3}\Sigma_{u}^{+}$ electronic transition) is proposed to be used as a source of information for the spectroscopic diagnostics of non-equilibrium plasmas. The detailed analysis of excitation-deactivation kinetics, rate constants of various collisional and radiative transitions and fitting procedures made it possible to develop two new methods of diagnostics of: (1) the ground $X^{1}\Sigma_{g}^{+}$ state vibrational temperature $T_{\text{vib}}$ from the relative intensity distribution, and (2) the rate of electron impact dissociation (d[\mbox{H_{2}}]/dt)_{\text{diss}} from the absolute intensity of the continuum. A known method of determination of $T_{\text{vib}}$ from relative intensities of Fulcher-$\alpha$ bands was seriously corrected and simplified due to the revision of $d \to a$ transition probabilities and cross sections of $d \gets X$ electron impact excitation. General considerations are illustrated with examples of experiments in pure hydrogen capillary-arc and H$_{2}$+Ar microwave discharges.Comment: REVTeX, 25 pages + 12 figures + 9 tables. Phys. Rev. E, eprint replaced because of resubmission to journal after referee's 2nd repor

Imprint of DES superstructures on the cosmic microwave background

Small temperature anisotropies in the cosmic microwave background (CMB) can be sourced by density perturbations via the late-time integrated Sachs-Wolfe (ISW) effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey (DES) in a different footprint, and using a different superstructure finding strategy. We identified 52 large voids and 102 superclusters at redshifts 0.2 < z < 0.65. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with DeltaTf ≈ -5.0 ± 3.7 muK and a hot imprint of superclusters DeltaTf ≈ 5.1 ± 3.2 muK; this is ˜1.2sigma higher than the expected |DeltaTf| ≈ 0.6 muK imprint of such superstructures in Lambda cold dark matter (LambdaCDM). If we instead use an a posteriori selected filter size (R/Rv = 0.6), we can find a temperature decrement as large as DeltaTf ≈ -9.8 ± 4.7 muK for voids, which is ˜2sigma above LambdaCDM expectations and is comparable to previous measurements made using Sloan Digital Sky Survey superstructure data

Scale-dependent non-Gaussianity and the CMB power asymmetry

We introduce an alternative parametrisation for the scale dependence of the non–linearity parameter fNL in quasi-local models of non–Gaussianity. Our parametrisation remains valid when fNL changes sign, unlike the commonly adopted power law ansatz fNL(k) ∝ knfNL. We motivate our alternative parametrisation by appealing to the self-interacting curvaton scenario, and as an application, we apply it to the CMB power asymmetry. Explaining the power asymmetry requires a strongly scale dependent non-Gaussianity. We show that regimes of model parameter space where fNL is strongly scale dependent are typically associated with a large gNL and quadrupolar power asymmetry, which can be ruled out by existing observational constraints

The hemispherical asymmetry from a scale-dependent inflationary bispectrum

If the primordial bispectrum is sufficiently large then the CMB hemispherical asymmetry may be explained by a large-scale mode of exceptional amplitude which perturbs the zeta two-point function. We extend previous calculations, which were restricted to one- or two-source scenarios, by providing a method to compute the response of the two-point function in any model yielding a 'local-like' bispectrum. In general, this shows that it is not the reduced bispectrum fNL which sources the amplitude and scale-dependence of the mode coupling but rather a combination of 'response functions'. We discuss why it is difficult to construct successful scenarios and enumerate the fine-tunings which seem to be required. Finally, we exhibit a concrete model which can be contrived to match the observational constraints and show that to a Planck-like experiment it would appear to have |fNL-local| ~ |fNL-equi| ~ |fNL-ortho| ~ 1. Therefore, contrary to previous analyses, we conclude that it is possible to generate the asymmetry while respecting observational constraints on the bispectrum and low-ell multipoles even without tuning our location on the long-wavelength mode

A CMB Gibbs sampler for localized secondary anisotropies

As well as primary fluctuations, CMB temperature maps contain a wealth of additional information in the form of secondary anisotropies. Secondary effects that can be identified with individual objects, such as the thermal and kinetic Sunyaev-Zel'dovich (SZ) effects due to galaxy clusters, are difficult to unambiguously disentangle from foreground contamination and the primary CMB however. We develop a Bayesian formalism for rigorously characterising anisotropies that are localised on the sky, taking the TSZ and KSZ effects as an example. Using a Gibbs sampling scheme, we are able to efficiently sample from the joint posterior distribution for a multi-component model of the sky with many thousands of correlated physical parameters. The posterior can then be exactly marginalised to estimate properties of the secondary anisotropies, fully taking into account degeneracies with the other signals in the CMB map. We show that this method is computationally tractable using a simple implementation based on the existing Commander component separation code, and also discuss how other types of secondary anisotropy can be accommodated within our framework

Individual development of preschool children - prevalences and determinants of delays in Germany: a cross-sectional study in Southern Bavaria

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2431/12/188 Extent: 9p.Background: Even minor abnormalities of early child development may have dramatic long term consequences. Accurate prevalence rates for a range of developmental impairments have been difficult to establish. Since related studies have used different methodological approaches, direct comparisons of the prevalence of developmental delays are difficult. The understanding of the key factors affecting child development, especially in preschool aged children remains limited. We used data from school entry examinations in Bavaria to measure the prevalence of developmental impairments in pre-school children beginning primary school in 1997–2009. Methods: The developmental impairments of all school beginners in the district of Dingolfing- Landau, Bavaria were assessed using modified “Bavarian School Entry Model” examination from 1997 to 2009 (N=13,182). The children were assessed for motor, cognitive, language and psychosocial impairments using a standardised medical protocol. Prevalence rates of impairments in twelve domains of development were estimated. Using uni- and multivariable logistic regression models, association between selected factors and development delays were assessed. Results: The highest prevalence existed for impairments of pronunciation (13.8%) followed by fine motor impairments (12.2%), and impairments of memory and concentration (11.3%) and the lowest for impairments of rhythm of speech (3.1%). Younger children displayed more developmental delays. Male gender was strongly associated with all developmental impairments (highest risk for fine motor impairments = OR 3.22, 95% confidence interval 2.86-3.63). Preschool children with siblings (vs. children without any siblings) were at higher risk of having impairments in pronunciation (OR 1.31, 1.14-1.50). The influence of the non-German nationality was strong, with a maximum risk increase for the subareas of grammar and psychosocial development. Although children with non-German nationality had a reduced risk of disorders for the rhythm of speech and pronunciation, in all other 10 subareas their risk was increased. Conclusions: In preschool children, most common were delays of pronunciation, memory and concentration. Age effects suggest that delays can spontaneously resolve, but providing support at school entry might be helpful. Boys and migrant children appear at high risk of developmental problems, which may warrant tailored intervention strategies.Heribert L Stich, Bernhard Th Baune, Riccardo N Caniato, Rafael T Mikolajczyk and Alexander Kräme