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Elemental, chemical, and structural analysis of polycrystalline materials at the micron scale is frequently carried out using microfocused synchrotron X-ray beams, sometimes on multiple instruments. The Maia pixelated energy-dispersive X-ray area detector enables the simultaneous collection of X-ray fluorescence (XRF) and diffraction because of the relatively large solid angle and number of pixels when compared with other systems. The large solid angle also permits extraction of surface topography because of changes in self-absorption. This work demonstrates the capability of the Maia detector for simultaneous measurement of XRF and diffraction for mapping the short- and long-range order across the grain structure in a Ni polycrystalline foil.
A new generation of solar instruments provides improved spectral, spatial, and temporal resolution, thus facilitating a better understanding of dynamic processes on the Sun. High-resolution observations often reveal multiple-component spectral line profiles, e.g., in the near-infrared He i 10830 Å triplet, which provides information about the chromospheric velocity and magnetic fine structure. We observed an emerging flux region, including two small pores and an arch filament system, on 2015 April 17 with the ‘very fast spectroscopic mode’ of the GREGOR Infrared Spectrograph (GRIS) situated at the 1.5-meter GREGOR solar telescope at Observatorio del Teide, Tenerife, Spain. We discuss this method of obtaining fast (one per minute) spectral scans of the solar surface and its potential to follow dynamic processes on the Sun. We demonstrate the performance of the ‘very fast spectroscopic mode’ by tracking chromospheric high-velocity features in the arch filament system.
Recently, in an intercomparison of the Hohenheim German oak chronology (Becker 1993) and the Göttingen chronology (Leuschner and Delorme 1988), an error was discovered in the former (Leuschner, in preparation). Due to an error in adding sections at 5241 bc, 41 yr are missing in the published Hohenheim chronology. After correction of the error, the two chronologies synchronize over their entire common length, back to 7200 bc.
The carbon star IRC +10 216 is a long-period Asymptotic Giant Branch (AGB) star suffering from strong stellar winds (several 10-5 M⊙/yr; Loup et al. 1993) which have led to an almost complete obscuration of the star by dust. Due to the high mass-loss rate, long period of P = 649 d (Le Bertre 1992), and carbon-rich chemistry of the dust-shell, IRC +10 216 is obviously in a very advanced stage of its AGB evolution. High-resolution near-infrared imaging of IRC +10 216 has revealed that on sub-arcsecond scales (100 mas) its dust shell is clumpy, bipolar, and changing on a time scale of only ~1 yr (Weigelt et al. 1997, 1998, Haniff & Buscher 1998, Osterbart et al. 2000, Tuthill et al. 2000). Since most dust shells around AGB stars are known to be spherically symmetric, whereas most proto-planetary nebulae (PPN) show an axisymmetric geometry (Olofsson 1996), it appears likely that IRC +10 216 has already entered the transition phase to the PPN stage. This suggests that the break of the dust-shell symmetry between the AGB and post-AGB phase already takes place at the end of the AGB evolution.
The prototypical dust-enshrouded carbon Mira IRC +10216 is known to exhibit intrinsic changes on a time scale of the order of only a few years as revealed, e.g., by CO infrared line profiles (Winters et al. 2000a), its infrared light curves, and by high spatial resolution monitoring in the infrared (Osterbart et al. 2000; Tuthill et al. 2000). In particular, the infrared light curves indicate a possible periodicity on a ≈ 20 yr time scale, i.e. that a recurrent phenomenon might lead to the observed variations. Such multi-periodicity time scales of several (≈ 10) stellar pulsation periods are predicted by consistent hydrodynamical models which include a proper treatment of dust formation (e.g. Winters et al. 2000b). In these models discrete dust layers form in time intervals which are several times longer than the typical pulsation period of an AGB star (Fleischer, Gauger, & Sedlmayr 1995; Höfner, Feuchtinger, & Dorfi 1995).
The center of the stellar association in 30 Doradus, R136 (HD 38268), is an unusually high concentration of massive and bright O, B and Wolf-Rayet stars and represents the closest example of an intense starburst region.
We present speckle masking observations of Seyfert galaxies with the Russian 6 m telescope. Diffraction-limited resolution of 76 mas in the K-band was obtained for the first time. This resolution is similar to the resolution of recent MERLIN and VLA observations of galactic centers, thus allowing us to study the radio-IR spectrum of the same structures. Figure 1 shows the decreasing K-band visibility function of NGC 1068 and the contour plot of our reconstructed image. The results show that NGC 1068 is resolved with a FWHM diameter of 30 mas or 2 pc for an assumed Gaussian flux distribution. The image is elongated in northern direction, which is approximately the direction of the radio jet. In the right panel of figure 1 the observed flux values at 5,15 and 22 GHz (from) are plotted together with our K-band flux. The spectral index between 5 GHz and the K-band is approximately 1/3. This spectrum can be explained by synchrotron emission of quasi-monoenergetic relativistic electrons (as for our Galactic Center by). Assuming that the observed flux is mainly nuclear light (from, for example, scattering lobes above and below a torus, without absorption and re-emission) we use the same synchrotron model as has been used for the Galactic Center to explain our data. With this model, we find a source radius of R ∼ 1015 cm, a magnetic field of B ∼ 11 G, a electron number density of ne ∼ 1.1103 cm−3 and a mean electron energy of ∼ 2.7 GeV. The corresponding model spectrum is shown in the right panel of fig. 1. The observed flux value at 2.2 μm lies slightly above the model spectrum. This could be caused by flux contributions from additional components, for example, a central stellar cluster, an accretion disk or thermal radiation from a dusty torus. We have also observed the central regions of other galaxies. For example, for NGC 4151, we found a dominant central core, which is not resolved, and therefore has a diameter of < 20 mas.
We present high-resolution J–, H–, and K–band observations of the carbon star IRC+10 216. The images were reconstructed from 6 m telescope speckle interferograms using the speckle masking bispectrum method. The H image has the unprecedented resolution of 70 mas. The H and K images consist of at least five dominant components within a 0.21 arcsec radius and a fainter asymmetric nebula. The J-, H-, and K—band images seem to have an X-shaped bipolar structure. A comparison of our images from 1995, 1996, 1997, and 1998 shows that the separation of the two brightest components A and B increased from ∼ 193 mas in 1995 to ∼ 246 mas in 1998.
The cometary shapes of component A in the H and J images and the 0.79 μm and 1.06 μm HST images suggest that the core of A is not the central star, but the southern (nearer) lobe of the bipolar structure. The position of the central star is probably at or near the position of component B, where the H—K color has its largest value of H—K = 4.2.
If the star is located at or near B, then the components A, C, and D are located close to the inner boundary of the dust shell at separations of ∼200 mas ∼30 AU (projected distance) ∼6 stellar radii for a distance of ∼ 150 pc, in agreement with our 2-dimensional radiative transfer modelling.
In addition to IRC+ 10 216 we studied the stellar disks and the dust shells of several related objects. Angular resolutions of 24 mas at 700 nm or 57 mas 1.6 μm were achieved.
We present four wave mixing experiments on GaN. We find an intrinsic homogeneous broadening of the A-exciton of 1.67 meV. A pronounced beating with a period of 0.52 ps is observed at excitation energies between the A- and the B-exciton and corresponds to an energy splitting of 7.98 meV of A- and B-exciton.
The infrared-optical properties of GaAs/GaNxAs1−x superlattice (SL) heterostructures (0 < x < 3.3%) are studied by variable angle-of-incidence infrared spectroscopic ellipsometry (IRSE) for wavenumbers from 250 cm−1 to 700 cm−1. The undoped SL structures where grown on top of a 300 nm thick undoped GaAs buffer layer on Te-doped (001) GaAs substrates by metal-organic vapor phase epitaxy (MOVPE). We observe the well-known Berreman-polariton effect within the GaAs LO-phonon region. We further observe a strong polariton-like resonance near the coupled longitudinal-optical plasmon-phonon frequency of the Te-doped substrate at 306 cm−1. For analysis of the IRSE data we employ the harmonic oscillator dielectric function model and the Drude model for free-carrier response. The additional resonance feature is explained by pseudo surface polariton (PSP) interface modes between the Te-doped GaAs and the undoped GaAs buffer layer / SL film. We find that the PSP modes are extremely sensitive to free-carrier properties within the SL structures, and we obtain a strong increase in free-carrier concentration within the GaNAs SL sublayers with increasing x from analysis of the IRSE data. We further observe the localized vibrational modes of nitrogen at 470 cm−1 in the GaNxAs1−x SL sublayers with a polar strength that increases linearly with x, and which can be used to monitor the nitrogen concentration in GaNxAs1−x.
We report on mid-infrared (600 – 4000 cm-1), refection-type optical-Hall effect measurements on epitaxial graphene grown on C-face silicon carbide and present Landau-level transition features detected at 1.5 K as a function of magnetic field up to 8 Tesla. The Landau-level transitions are detected in reflection configuration at oblique incidence for wavenumbers below, across and above the silicon carbide reststrahlen range. Small Landau-level transition features are enhanced across the silicon carbide reststrahlen range due to surface-guided wave coupling with the electronic Landau-level transitions in the graphene layer. We analyze the spectral and magnetic-field dependencies of the coupled resonances, and compare our findings with previously reported Landau-level transitions measured in transmission configuration [4,5,6]. Additional features resemble transitions previously assigned to bilayer inclusion , as well as graphite . We discuss a model description to account for the electromagnetic polarizability of the graphene layers, and which is sufficient for quantitative model calculation of the optical-Hall effect data.
A modified critical point model dielectric function for graphene is derived here and used to analyze spectroscopic ellipsometry data obtained over a wide spectral range from 3 to 9 eV. Critical point and exciton resonance energies are extracted and discussed. Our findings indicate that epitaxial graphene on SiC to exhibits equivalent exciton behavior to that of suspended graphene. We further apply our model dielectric function to evaluate dielectric function data for highly oriented pyrolytic graphite reported in the literature. Excellent agreement is found between the critical point model developed here and the literature data even for the low energy spectral range up to 1 eV.
The effects of antidepressants for treating depressive disorders have been overestimated because of selective publication of positive trials. Reanalyses that include unpublished trials have yielded reduced effect sizes. This in turn has led to claims that antidepressants have clinically insignificant advantages over placebo and that psychotherapy is therefore a better alternative. To test this, we conducted a meta-analysis of studies comparing psychotherapy with pill placebo.
Ten 10 studies comparing psychotherapies with pill placebo were identified. In total, 1240 patients were included in these studies. For each study, Hedges’ g was calculated. Characteristics of the studies were extracted for subgroup and meta-regression analyses.
The effect of psychotherapy compared to pill placebo at post-test was g = 0.25 [95% confidence interval (CI) 0.14–0.36, I2 = 0%, 95% CI 0–58]. This effect size corresponds to a number needed to treat (NNT) of 7.14 (95% CI 5.00–12.82). The psychotherapy conditions scored 2.66 points lower on the Hamilton Depression Rating Scale (HAMD) than the placebo conditions, and 3.20 points lower on the Beck Depression Inventory (BDI). Some indications for publication bias were found (two missing studies). We found no significant differences between subgroups of the studies and in meta-regression analyses we found no significant association between baseline severity and effect size.
Although there are differences between the role of placebo in psychotherapy and pharmacotherapy research, psychotherapy has an effect size that is comparable to that of antidepressant medications. Whether these effects should be deemed clinically relevant remains open to debate.
The Hanneh Member (Cambrian Stage 5) of the Burj Formation and the Umm Ishrin Formation of Jordan represent a transgressive-regressive succession that contains twenty-eight ichnotaxa, including vertical burrows (Arenicolites isp., Diplocraterion isp., Gyrolithes polonicus, Rosselia isp., Skolithos linearis, escape trace fossils), horizontal simple burrows and trails (Archaeonassa fossulata, Gordia marina, Helminthoidichnites tenuis, Palaeophycus tubularis, Planolites beverleyensis, P. montanus), plug-shaped burrows (Bergaueria sucta), horizontal branched burrows (Asterosoma isp., Phycodes isp., Treptichnus cf. T. pedum), bilobate structures (various ichnospecies of Cruziana and Rusophycus), and trackways and scratch marks (Diplichnites isp., Dimorphichnus cf. D. obliquus, Monomorphichnus isp.). Eleven trace-fossil assemblages are identified. The Arenicolites isp. and Diplocraterion isp. assemblages occur in transgressive tidal dunes and bars whereas the Rosselia isp. assemblage characterizes areas between tidal dunes. The Cruziana salomonis assemblage reflects a wide variety of environmental settings including channels within tidal-bar complexes, bottomsets of tidal dunes, and interdune areas. The Gordia marina assemblage is present between dune patches. The Gyrolithes polonicus assemblage penetrates into firmground mudstone below the maximum flooding surface. The Bergaueria sucta, Archaeonassa fossulata, Rusophycus aegypticus and Cruziana problematica assemblages occur in different subenvironments of the progradational delta. Cruziana salomonis and Rusophycus burjensis, originally considered indicative of an early Cambrian age, are actually middle Cambrian in their type locality. Occurrences of Cruziana jordanica and Rusophycus aegypticus provide evidence that these ichnospecies are of the same age in Jordan and may co-exist in terms of stratigraphic distribution with C. salomonis and R. burjensis.
We demonstrate that the anisotropic optical response of metal (cobalt) slanted columnar thin films (STF) at THz frequencies strongly depends on the dielectric properties of the dielectric ambient surrounding the slanted columnar thin films. An effective medium dielectric function approach is used to describe the combined optical response of metal slanted columnar thin film and dielectric ambient. Our observations indicate that metal (cobalt) slanted columnar thin films can be used as sensors which will enable detection and characterization of minute amounts of dielectrics at THz frequencies, such as for flow-based detection of liquid chemical constituents.
Spectroscopic mapping ellipsometry measurements in the visible spectrum (1.25 to 5.35 eV) are performed to determine the lateral variations of epitaxial graphene properties as grown on 3C SiC. Data taken in the visible spectrum is sensitive to both the Drude absorption of free charge carriers and the characteristic exciton enhanced van Hove singularity at 5 eV. Subsequent analysis with simple oscillator models allows the determination of physical parameters such as free charge carrier scattering time and local graphene thickness with a lateral resolution of 50 microns.