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SN2014J is the closest supernova of type Ia that occurred in the last 40 years. This provides an opportunity for unprecedented observational detail and coverage in many astronomical bands, which will help to better understand the still unknown astro-physics of these supernovae. For the first time, such an event occurs sufficiently nearby so that also γ-rays are able to contribute to such investigations. This is important, as the primary source of the supernova light is the radioactive energy from about 0.5 M⊙ of 56Ni produced in the explosion, and the γ rays associated with this decay make the supernova shine for months. The INTEGRAL γ-ray observatory of ESA has followed the supernova emission for almost 5 months. The characteristic γ-ray lines from the 56Ni decay chain through 56Co to 56Fe have been measured. We discuss these observations, and the implications of the measured γ-ray line characteristics as they evolve. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The quantitative structure determination of adsorbed species on quasicrystal surfaces has sofar appeared to present insurmountable problems. The normal incidence standing x-ray wave field technique offers a simple solution, without extensive data sets or large computations. Its application to quasicrystals raises several conceptual difficulties that are related to the phase problem in x-ray diffraction. We demonstrate their solution for the case of Si atoms adsorbed on the decagonal Co-rich modification of the Al-Co-Ni quasicrystal to determine the local structure, comprising 6-atom clusters in particular hollow sites. [ABSTRACT FROM AUTHOR]

Particles are accelerated in cosmic sites probably under conditions very different from those at terrestrial particle accelerator laboratories. Nevertheless, specific experiments which explore plasma conditions and stimulate particle acceleration carry significant potential to illuminate some aspects of the cosmic particle acceleration process. Here we summarize our understanding of cosmic particle acceleration, as derived from observations of the properties of cosmic ray particles, and through astronomical signatures caused by these near their sources or throughout their journey in interstellar space. We discuss the candidate-source object variety, and what has been learned about their particle-acceleration characteristics. We conclude identifying open issues as they are discussed among astrophysicists. – The cosmic ray differential intensity spectrum across energies from 1010 eV to 1021 eV reveals a rather smooth power-law spectrum. Two kinks occur at the “knee” (≃1015 eV) and at the “ankle” (≃ 3×1018 eV). It is unclear if these kinks are related to boundaries between different dominating sources, or rather related to characteristics of cosmic-ray propagation. Currently we believe that galactic sources dominate up to 1017 eV or even above, and the extragalactic origin of cosmic rays at highest energies merges rather smoothly with galactic contributions throughout the 1015–1018 eV range. Pulsars and supernova remnants are among the prime candidates for galactic cosmic-ray production, while nuclei of active galaxies are considered best candidates to produce ultrahigh-energy cosmic rays of extragalactic origin. The acceleration processes are probably related to shocks formed when matter is ejected into surrounding space from energetic sources such as supernova explosions or matter accreting onto black holes. Details of shock acceleration are complex, as relativistic particles modify the structure of the shock, and simple approximations or perturbation calculations are unsatisfactory. This is where laboratory plasma experiments are expected to contribute, to enlighten the non-linear processes which occur under such conditions. [ABSTRACT FROM AUTHOR]

Abstract: The Orion region hosts one of the closest associations of recent massive-star formation. Measurements of the 1809keV emission from this region by the COMPTEL observatory shows an interesting offset of the 26Al emission from the massive stars that are believed to be the source of the 26Al, and the emission appears rather extended. This suggests that the radioactive material flows from the stellar associations into the nearby Eridanus cavity, and this provides a unique possibility to study the properties of massive stars and their interactions with their surroundings, as well as the properties of the turbulent ISM in the vicinity of OB associations. We model this region with a population synthesis code, and take the geometry of the region into account. This study also bears on the larger theme of galactic chemo dynamics (GCD), as the winds and supernova ejecta of massive stars provide the essential chemical and energetic feedback mechanisms responsible for the formation and evolution of galaxies. [Copyright &y& Elsevier]

This paper reviews recent progress in the study of rare gas films on quasicrystalline surfaces. The adsorption of Xe on the 10-fold surface of decagonal Al-Ni-Co was studied using low-energy electron diffraction (LEED). The results of these studies prompted the development of a theoretical model, which successfully reproduced the thermodynamic parameters found in the experiment. Grand canonical Monte Carlo (GCMC) simulations for Xe-produced structures that agreed with the experimental observations of the adsorption structures and provided a deeper insight into the nature of the ordering. A first-order commensurate-incommensurate transition, which involves a transition from a quasicrystalline five-fold structure to a periodic hexagonal structure, was discovered and characterized for the Xe monolayer. The five rotational domains of the hexagonal structure observed in the LEED study were shown in the GCMC study to be mediated by pentagonal defects, which are entropic in nature, and not by substrate defects. The GCMC study found an absence of any such transition for Kr, Ar and Ne on the same surface. A detailed analysis of this transition led to the conclusion that the formation of the hexagonal layer depends on matching the gas and substrate characteristic lengths. [ABSTRACT FROM AUTHOR]

Abstract: The shape of the γ-ray line from radioactive 26Al, at 1808.7keV energy in the frame of the decaying isotope, is determined by its kinematics when it decays, typically 106 yr after its ejection into the interstellar medium from its nucleosynthesis source. Three prior measurements of the line width exist: HEAO-C’s 1982 value of (0+3)keV FWHM, the GRIS 1996 value of (5.4±1.3)keV FWHM, and the recent RHESSI value of (2.0±0.8)keV FWHM, suggesting either “cold”, “hot”, or “warm”26Al in the ISM. We model the line width as expected from Galactic rotation, expanding supernova ejecta, and/or Wolf–Rayet winds, and predict a value below 1keV (FWHM) with plausible assumptions about 26Al initial velocities and expansion history. We use this model as an input to a model-fitting approach for INTEGRAL/SPI data analysis in the 1808.7keV line. Our aim is to detect the signature of Galactic rotation and to constrain the contributions of 26Al from different regions of the Galaxy to the total emission, such as putting an upper limit on the contribution of local sources. [Copyright &y& Elsevier]

The ordering of physically adsorbed gases on quasicrystalline surfaces exemplifies the effects of competing interactions. In this study, grand canonical Monte Carlo simulations were performed to complement experimental measurements of the ordering of Xe adsorbed on the tenfold surface of decagonal Al–Ni–Co. The simulations employed a semi-empirical gas-surface interaction, based on conventional combining rules, and the Lennard–Jones Xe–Xe interaction. The simulation results are consistent with the experiment and provide a new insight into the ordering behavior. The film initially has a fivefold quasicrystalline symmetry, but it evolves into a close-packed structure during adsorption of the second layer. The presence of symmetry defects in the sixfold structure creates domains of Xe having different (but equivalent) rotational epitaxy, suggesting that even in the absence of substrate defects, the annealed film has the five different rotational alignments observed in the experimental studies. [ABSTRACT FROM AUTHOR]

Gamma-ray lines from radioactive isotopes, ejected into interstellar space by cosmic nucleosynthesis events, are observed with new space telescopes. The Compton Observatory had provided a sky survey for the isotopes 56Co, 22Na, 44Ti, and 26Al, detecting supernova radioactivity and the diffuse glow of long-lived radioactivity from massive stars in the Galaxy. High-resolution spectroscopy is now being exploited with Ge detectors: Since 2002, with ESA''s INTEGRAL satellite and the RHESSI solar imager two space-based Ge-gamma-ray telescopes are in operation, measuring Doppler broadenings and line shape details of cosmic gamma-ray lines. First year''s results include a detection and line shape measurement of annihilation emission, and 26Al emission from the inner Galaxy and from the Cygnus region. 60Fe gamma-ray intensity is surprisingly low; it may have been detected by RHESSI at 10% of the 26Al brightness, yet is not seen by INTEGRAL. 44Ti emission from Cas A and SN1987A is being studied; no other candidate young supernova remnants have been found through 44Ti. 22Na from novae still is not seen. [Copyright &y& Elsevier]

Galactic 26Al is believed to be predominantly injected into the ISM from winds and supernovae of massive stars. These stars are typically born in groups and associations, which evolve over tens of Myrs, and shape the interstellar medium in their surroundings. 26Al contained in stellar outflows produces a γ-ray line at 1.809 MeV, which is potentially observable from regions of active star formation on time scales of a few Myrs, i.e., comparable to the mean life of 26Al. This relatively long time scale may lead to spatial offsets between the observed 26Al γ-ray emission and tracers of 26Al sources, such as locations of massive-stars, HII regions, or IR emission from dust heated by starlight. We find evidence for such an offset in star forming regions towards Orion. [Copyright &y& Elsevier]

Objective – To investigate the occurrence of microembolic signals (MES) and hemodynamic features in patients with acute symptomatic intracranial cerebral artery stenoses by transcranial Doppler (TCD). Material and methods – Twelve patients with acute hemispheric ischemic events and corresponding intracranial cerebral artery stenoses as identified by TCD, and exclusion of extracranial or cardiac emboli sources were repeatedly studied by TCD monitoring of the affected and the contralateral vessel. The occurrence of MES and MES clusters (≥3 MES per second) and of flow velocity changes was examined. Results – Nine patients presented with MES in the affected artery during the first measurement. In seven patients sudden flow velocity changes could be detected in the affected vessel. In five patients these changes were accompanied by MES clusters. MES and velocity changes disappeared in all patients during follow-up, and the degree of stenosis decreased in nine patients. Conclusions – The high prevalence of MES and sudden velocity changes in acute intracranial cerebral artery stenoses indicates that acute intracranial stenoses may be formed at least in part by mobile thrombotic material. [ABSTRACT FROM AUTHOR]

We examine the isotope production in star forming regions through a model of stellar-group population synthesis evolution. From this we obtain the light-curves of γ-ray line emission due to radioactive decay of 26Al, 60Fe and the e−e+ annihilation line. We discuss in particular, the effects of the dispersion due to the discreteness of the stellar populations. We conclude that when predicted γ-ray line observations are combined with other multi-wavelength measurements, one can efficiently constrain the age of a stellar population, and help to identify the primary nucleosynthesis sources of the radio-isotopes. [ABSTRACT FROM AUTHOR]

ABSTRACT The performance of the INTEGRAL Spectrometer SPI for large-scale imaging of the Galactic diffuse continuum emission has been studied, Simulations of long-term survey data have been made baaed on the computed SPI response and background estimates for Galactic emission based on OSSE results. Since for continuum emission the background in a wide energy band is much larger than for narrow lines such as 511 keV or [sup 26]Al, the background is larger; however this is compensated by the higher intensity of the Galactic continuum. Expected results for the 200 - 400 keV band are presented. [ABSTRACT FROM AUTHOR]

Deals with the use of COMPTEL data in the course of the Compton Mission for the production of a first all-sky map in the 1.275 megaelectronvolt (MeV) sodium emission. Calculation of the sodium mass in the ejected shell; Factor that hampered the derivation of sodium mass limits from the 1.275 MeV line flux measurements; Conclusions.

Focuses on a 1.8 megaelectronvolt measurements in the Vela region based in six years of observation. Approaches to the imaging analysis performed in the region; Illustration on the overall deviation of the Vela region from the Galactic-large scale emission; Correlation of the flux limits observed with existing model of supernova nucleosynthesis.

Abstract: Factor XIII deficiency is an uncommon inherited disorder which is characterized by umbilical cord bleeding and an unusually high incidence of intracranial hemorrhage. We report here a case of Factor XIII deficiency in a child that presented a caput. succedaneum as the first manifestation of the disease and then an umbilical cord bleeding. The importance of performing a quantitative FXIII assay in the presence of strong clinical suspicion is strengthened because of the normality of the standard screening tests and the important therapeutic consequences. [Copyright &y& Elsevier]

Type Ia supernovae (SNe Ia) may originate from a wide variety of explosion scenarios and progenitor channels. They exhibit a factor of ≈10 difference in brightness and thus a differentiation in the mass of 56Ni â†' 56Co â†' 56Fe. We present a study on the fate of positrons within SNe Ia in order to evaluate their escape fractions and energy spectra. Our detailed Monte Carlo transport simulations for positrons and Îł -rays include both β + decay of 56Co and pair production. We simulate a wide variety of explosion scenarios, including the explosion of white dwarfs (WDs) close to the Chandrasekhar mass (M Ch), He-triggered explosions of sub- M Ch WDs, and dynamical mergers of two WDs. For each model, we study the influence of the size and morphology of the progenitor magnetic field between 1 and 1013 G. Population synthesis based on the observed brightness distribution of SNe Ia was used to estimate the overall contributions to Galactic positrons due to escape from SNe Ia. We find that this is dominated by SNe Ia of normal brightness, where variations in the distribution of emitted positrons are small. We estimate a total SNe Ia contribution to Galactic positrons of <2% and, depending on the magnetic field morphology, <6â€"20% for M Ch and sub- M Ch, respectively. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor referencing articles and topics on cerebral ischemia related to cannabis smoking, published in previous issues.

A letter to the editor about a theory which states that the evolutionary target situation of vasovagal fainting was a life threatening bleeding is presented.

Context. Massive stars influence their environment through stellar winds, ionising radiation, and supernova explosions. This is signified by observed interstellar bubbles. Such feedback is an important factor for galaxy evolution theory and galactic wind models. The efficiency of the energy injection into the interstellar medium (ISM) via bubbles and superbubbles is uncertain, and is usually treated as a free parameter for galaxy scale effects. In particular, since many stars are born in groups, it is interesting to study the dependence of the effective energy injection on the concentration of the stars. Aims. We aim to reproduce observations of superbubbles, their relation to the energy injection of the parent stars, and to understand their effective energy input into the ISM, as a function of the spatial configuration of the group of parent stars. Methods. We study the evolution of isolated and merging interstellar bubbles of three stars (25, 32, and 60 M☉) in a homogeneous background medium with a density of 10mp cm-3 via 3D-hydrodynamic simulations with standard ISM thermodynamics (optically thin radiative cooling and photo-electric heating) and time-dependent energy and mass input according to stellar evolutionary tracks. We vary the position of the three stars relative to each other to compare the energy response for cases of isolated, merging and initially cospatial bubbles. Results. Mainly due to the Vishniac instability, our simulated bubbles develop thick shells and filamentary internal structures in column density. The shell widths reach tens of per cent of the outer bubble radius, which compares favourably to observations. More energy is retained in the ISM for more closely packed groups, by up to a factor of three and typically a factor of two for intermediate times after the first supernova. Once the superbubble is established, different positions of the contained stars make only a minor difference to the energy tracks. For our case of three massive stars, the energy deposition varies only very little for distances up to about 30 pc between the stars. Energy injected by supernovae is entirely dissipated in a superbubble on a timescale of about 1 Myr, which increases slightly with the superbubble size at the time of the explosion. Conclusions. The Vishniac instability may be responsible for the broadening of the shells of interstellar bubbles. Massive star winds are significant energetically due to their - in the long run - more efficient, steady energy injection and because they evacuate the space around the massive stars. For larger scale simulations, the feedback effect of close groups of stars or clusters may be subsumed into one effective energy input with insignificant loss of energy accuracy. [ABSTRACT FROM AUTHOR]

Aims. We study the populations of massive stars in the Carina region and their energetic feedback and ejection of 26Al. Methods. We did a census of the stellar populations in young stellar clusters within a few degrees of the Carina nebula. For each star we estimated the mass, based on the spectral type and the host cluster age. We used population synthesis to calculate the energetic feedback and ejection of 26Al from the winds of the massive stars and their supernova explosions. We used 7 years of INTEGRAL observations to measure the 26Al signal from the region. Results. The INTEGRAL 26Al signal is not significant with a best-fit value of ∼1.5 ± 1.0 × 10-5 ph cm-2 s-1, approximately half of the published Compton Gamma Ray Observatory (CGRO) result, but in agreement with the latest CGRO estimates. Our analysis of the stellar populations in the young clusters leads to an expected signal of ∼half the observed value, but the results are consistent within 2σ. We find that the fraction of 26Al ejected in Wolf-Rayet winds is high, and the observed signal is unlikely to be caused by 26Al ejected in supernovae alone, indicating a strong wind ejection of 26Al. Due to the lack of prominent O stars, regions with ages ≳10 Myr are often neglected in studies of OB associations. We find that in the Carina region such clusters contribute significantly to the stellar mass and the energetics of the region. [ABSTRACT FROM AUTHOR]

Background. Impairment of cerebral autoregulation is known to adversely affect outcome following traumatic brain injury (TBI). The phase shift (PS) method of cerebral autoregulation (CA) assessment describes the time lag between fluctuations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in the middle cerebral artery. An alternative method (Mx-ABP) is based on the statistical correlation between ABP and CBFV waveforms over time. We compared these two indices in a cohort of severely head injured patients undergoing controlled, 6-breaths-per-minute ventilation. Methods. PS and Mx-ABP were calculated from 33 recordings of CBFV and MAP in 22 patients with TBI. Spearman’s correlation coefficient was used to assess the agreement between PS and Mx-ABP. The relationship between ICP slow wave amplitude, MAP slow wave amplitude and mean ICP was also examined. Findings. Mean values for Mx-ABP and PS were 0.44 ± 0.27, and 49 ± 26 (degrees), respectively. PS correlated significantly with Mx-ABP ( r = −0.648, p < 0.001). A Bland-Altman plot of normalised Mx-ABP and Phase Shift values showed no significant bias or relationship (mean difference = 0.0004, r = −0.037, p = 0.852). During the test procedure, ICP fluctuated in an approximately sinusoidal fashion, with a mean amplitude of 4.96 ± 2.72 mmHg (peak to peak). The magnitude of ICP fluctuation during deep breathing correlated weakly but significantly with mean ICP ( r = 0.391, p < 0.05) and with the amplitude of ABP fluctuations ( r = 0.625, p < 0.0005). Conclusions. Phase shift and Mx-ABP in TBI are well correlated. Deep breathing presents as an effective tool with which to assess autoregulation using the phase shift method. [ABSTRACT FROM AUTHOR]

Background. As a sensitive and convenient means for the cerebral hemodynamic monitoring, dynamic cerebral autoregulation testing could be especially useful in medical conditions where less invasive diagnostics and therapies are preferred. This study analysed the effect of carotid stenting on dynamic autoregulation in elderly patients focussing on the relation between blood pressure and cerebral blood flow velocity. Methods. We examined 20 patients age 69 ± 8 years with coexisting cerebrovascular and medical risk factors before and at least six month after stenting of severe carotid stenoses. Data were compared to 24 age-matched healthy controls. Slow spontaneous oscillations were studied in continuous recordings of Transcranial Doppler and beat-to-beat blood pressure. Analysis was based on the “high-pass filter model”, which predicts a positive phase relationship between these oscillations. Findings. Whereas phase shift angles were diminished (20.4 ± 14.1°) before stenting, after stenting these values were significantly increased to normal (48.1 ± 16.6°), to the level of controls (46.7 ± 15.9°). Medical conditions such as coronary artery disease, arterial hypertension, and dyslipidemia did not diminish this recovery. The level of increase was inversely correlated with the initial autoregulatory deficit ( r = −0.68) which was largest with insufficient collateral blood supply and symptomatic carotid stenoses. Conclusions. The study showed that an impaired cerebral autoregulation may recover after stent-guided carotid angioplasty even in the elderly with co-existing medical conditions. In this respect to regain vasomotor capability, patients with cerebrovascular risk factors seemed to benefit particularly. [ABSTRACT FROM AUTHOR]

Objectives – This study applied dynamic cerebral autoregulation (DCA) testing distally to severe bilateral vertebral artery disease (BVAD). Methods – Using continuous monitoring of beat-to-beat blood pressure and transcranial Doppler of the posterior cerebral arteries (PCA) were examined in 20 patients with BVAD and 22 controls. DCA testing was based on the ‘high-pass filter model’, which predicts a positive phase relationship between spontaneous oscillations (M-waves 3–9 cpm and R-waves 9–20 cpm) in blood pressure and cerebral blood flow velocity. Results – In patients with BVAD, DCA testing detected autoregulatory deficits of different degrees. The lowest M-wave phase shift angles were found in the PCA territory distally to intracranial BVAD. Conclusion – This study suggests that DCA testing of the PCA could help to quantify the hemodynamic impact of BVAD. It highlights the relevance of functional TCD sonography as a useful diagnostic tool for the hemodynamic evaluation of vertebrobasilar disease. [ABSTRACT FROM AUTHOR]

The diffraction from one- and two-dimensional aperiodic structures is studied by using Fibonacci and other aperiodic gratings produced by several methods. By examining the laser diffraction patterns obtained from these gratings, the effects of aperiodic order on the diffraction pattern was observed and compared to the diffraction from real quasicrystalline surfaces. The correspondence between diffraction patterns from two-dimensional gratings and from real surfaces is demonstrated. [ABSTRACT FROM AUTHOR]

Haubrich C, Klemm A, Diehl RR, Möller-Hartmann W, Klötzsch C. M-wave analysis and passive tilt in patients with different degrees of carotid artery disease. Acta Neurol Scand 2003 DOI: 10.1046/j.1600-0404.2003.00210.x © Blackwell Munksgaard 2003. Carotid artery disease (CAD) is able to critically impair cerebral autoregulation which increases the risk for stroke. As therapeutic strategy largely depends on the degree of CAD, we investigated whether this gradation is also related to significant changes in autoregulatory capacity. We applied cross-spectral analysis (CSA) of spontaneous Mayer-wave (M-wave) oscillations and passive tilting (PT) to test cerebral autoregulation. Cerebral autoregulation was tested in 102 patients with carotid stenosis (≥70%) or occlusion and 14 controls by comparison of continuous transcranial Doppler sonography of the middle cerebral artery and beat-to-beat arterial blood pressure (ABP) during PT to 80° head-up position as well as by CSA of M-waves (3–9 cpm). The orthostatic decrease of cerebral blood flow velocity (CBFV) was not correlated with the degree of CAD and showed a lower sensitivity and specificity than phase angle shifts between M-waves in ABP and CBFV (sensitivity: 75–80%, specificity: 86%). Phase angles were gradually lowered in carotid stenoses > 70%, but apparently, they were only moderately correlated with the degree of CAD ( r = −0.35, P < 0.01). An additional influencing factor seemed to be the sufficiency of collateralization. The results show that CSA of M-waves is more appropriate for testing autoregulation than PT. CSA suggests that the capacity to autoregulate depends to a certain extent on the degree of CAD but is also influenced by the sufficiency of collateral pathways and pre-existing strokes. [ABSTRACT FROM AUTHOR]

The COMPTEL observations of the galactic 1.809 MeV emission attributed to the radioactive decay of 26Al have confirmed the diffuse nature of this interstellar emission line. One of the most significant features of the reconstructed intensity pattern is a flux enhancement towards Cygnus. This region is fairly young and contains a wealth of massive stars, most of them grouped in the Cygnus OB associations. Multi-frequency model fitting strongly supports the hypothesis of massive stars and their descendent supernovae being the dominant sources of interstellar 26Al as observed by COMPTEL. Massive stars and supernovae are known to impart a large amount of kinetic energy into their surroundings causing shock regions and large cavities in the ISM. In addition, a significant fraction of the electro-magnetic radiation of these stars is emitted in the EUV regime leading to photoionisation of the surrounding medium. We applied a population synthesis model in combination with an 1D model of expanding superbubbles to the Cygnus OB associations. Besides the expected 1.809 MeV flux and the γ-ray line intensity due to interstellar 60Fe we compute the sizes and expansion parameters of the expected HI-structures and the free–free emission intensities due to the photoionizing radiation from massive stars within this region of the sky. We discuss our present understanding of the Cygnus region with respect to the massive star census. Our model assigns about 70% of the 1.809 MeV intensity to six known OB associations, about 20% to known isolated sources and roughly 10% to an unknown diffuse component. [ABSTRACT FROM AUTHOR]

The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ~580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ~660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (=750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and "global" measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature. [ABSTRACT FROM AUTHOR]

ABSTRACT Large-scale skymapping with COMPTEL using the full survey database presents challenging problems on account of the complex response and time-variable background. A new approach which attempts to address some of these problems is described, in which the information about each observation is preserved throughout the analysis. In this method, a maximum-entropy algorithm is used to determine image and background simultaneously. Because of the extreme computing requirements, the method has been implemented on a parallel computer, which brings large gains since the response computation is fully parallelizable. The zero level is left undetermined in this method. Results using data from 7 years of COMPTEL data are presented. [ABSTRACT FROM AUTHOR]

ABSTRACT We present first results from a new large-scale mapping and model-fitting analysis of the COMPTEL data at 1-30 MeV using 5 years of observations. The analysis includes our currently most advanced technique of accounting for the time-variable Instrumental background and produces a mutually consistent set of model-fitting parameters (spectra) and sky maps. [ABSTRACT FROM AUTHOR]

Considers a two-step approach to determine the underlying celestial continuum emission in the 1.8 megaelectronvolt (MeV) band. Purpose of the model fitting technique used in the MeV data; Description on the 1.8 MeV maximum-entropy map.

Highlights the titanium (Ti) line emission survey performed by COMPTEL on-board the Compton Gamma Ray Observatory. Discussion on the full-sky mapping and imaging analysis in the Ti line emission; Conclusions.

Compares the COMPTEL 1.8 megaelectronvolt (MeV) γ-ray line data to an extended set of all-sky maps covering the entire explored wavelength range from the radio band up to high-energy gamma-rays. Description on the background model used in the COMPTEL data; Maps in the database which trace all of the features of the 1.8 MeV data; Discussion on the MeV distribution or emission.

A low-temperature (25 K) STM study of Cs adsorption on Cu(211) indicates that Cs forms variabledensity structures which align along the step edges of the Cu(211) surface. The density of the overlayer increases with Cs coverage, forming a quasihexagonal c(2 × 2) structure at a coverage of 0.17. A dynamical LEED study of that structure at 130 K indicates that the Cs atoms are adsorbed on top of the Cu atoms in the center of the terraces, with a Cs-Cu nearest-neighbor distance of 3.56 ± 0.04 Å. This structure is accompanied by a significant rumpling of the Cu(211) surface. [ABSTRACT FROM AUTHOR]

Nuclear astrophysics, and particularly nuclear emission line diagnostics from a variety of cosmic sites, has remained one of the least developed fields in experimental astronomy, despite its central role in addressing a number of outstanding questions in modern astrophysics. Radioactive isotopes are co-produced with stable isotopes in the fusion reactions of nucleosynthesis in supernova explosions and other violent events, such as neutron star mergers. The origin of the 511 keV positron annihilation line observed in the direction of the Galactic Center is a 50-year-long mystery. In fact, we still do not understand whether its diffuse large-scale emission is entirely due to a population of discrete sources, which are unresolved with current poor angular resolution instruments at these energies, or whether dark matter annihilation could contribute to it. From the results obtained in the pioneering decades of this experimentally-challenging window, it has become clear that some of the most pressing issues in high-energy astrophysics and astro-particle physics would greatly benefit from significant progress in the observational capabilities in the keV-to-MeV energy band. Current instrumentation is in fact not sensitive enough to detect radioactive and annihilation lines from a wide variety of phenomena in our and nearby galaxies, let alone study the spatial distribution of their emission. In this White Paper (WP), we discuss how unprecedented studies in this field will become possible with a new low-energy gamma-ray space experiment, called ASTENA (Advanced Surveyor of Transient Events and Nuclear Astrophysics), which combines new imaging, spectroscopic and polarization capabilities. In a separate WP (Guidorzi et al. 39), we discuss how the same mission concept will enable new groundbreaking studies of the physics of Gamma–Ray Bursts and other high-energy transient phenomena over the next decades. [ABSTRACT FROM AUTHOR]

Emission from the radioactive trace element 26Al has been observed throughout the Milky Way with the COMPTEL and INTEGRAL satellites. In particular, the Doppler shifts measured with INTEGRAL connect 26Al with superbubbles, which may guide 26Al flows off spiral arms in the direction of Galactic rotation. In order to test this paradigm, we have performed galaxy-scale simulations of superbubbles with 26Al injection in a Milky Way-type galaxy. We produce all-sky synthetic γ-ray emission maps of the simulated galaxies. We find that the 1809 keV emission from the radioactive decay of 26Al is highly variable with time and the observer's position. This allows us to estimate an additional systematic variability of 0.2 dex for a star formation rate derived from 26Al for different times and measurement locations in Milky Way-type galaxies. High-latitude morphological features indicate nearby emission with correspondingly high-integrated γ-ray intensities. We demonstrate that the 26Al scale height from our simulated galaxies depends on the assumed halo gas density. We present the first synthetic 1809 keV longitude-velocity diagrams from 3D hydrodynamic simulations. The line-of-sight velocities for 26Al can be significantly different from the line-of-sight velocities associated with the cold gas. Over time, 26Al velocities consistent with the INTEGRAL observations, within uncertainties, appear at any given longitude, broadly supporting previous suggestions that 26Al injected into expanding superbubbles by massive stars may be responsible for the high velocities found in the INTEGRAL observations. We discuss the effect of systematically varying the location of the superbubbles relative to the spiral arms. [ABSTRACT FROM AUTHOR]

The rapid neutron capture process (r process) is believed to be responsible for about half of the production of the elements heavier than iron and contributes to abundances of some lighter nuclides as well. A universal pattern of r -process element abundances is observed in some metal-poor stars of the Galactic halo. This suggests that a well-regulated combination of astrophysical conditions and nuclear physics conspires to produce such a universal abundance pattern. The search for the astrophysical site for r -process nucleosynthesis has stimulated interdisciplinary research for more than six decades. There is currently much enthusiasm surrounding evidence for r -process nucleosynthesis in binary neutron star mergers in the multi-wavelength follow-up observations of kilonova/gravitational-wave GRB170807A/GW170817. Nevertheless, there remain questions as to the contribution over the history of the Galaxy to the current solar-system r -process abundances from other sites such as neutrino-driven winds or magnetohydrodynamical ejection of material from core-collapse supernovae. In this review we highlight some current issues surrounding the nuclear physics input, astronomical observations, galactic chemical evolution, and theoretical simulations of r -process astrophysical environments with the goal of outlining a path toward resolving the remaining mysteries of the r process. [ABSTRACT FROM AUTHOR]

The coadsorption of alkali atoms with Xe on a graphite substrate has been studied using He-atom scattering and low-energy electron diffraction (LEED). When Xe is adsorbed on a graphite surface which has a low density of alkali metal adatoms, ordered Xe monolayers and bilayers are formed. Differences in adsorption rate and desorption temperatures of the Xe indicate that the presence of alkali metal atoms on the surface increase the sticking coefficient and the desorption temperatures of Xe adatoms. As deduced from specular He-atom scattering desorption curves, this stronger adsorption behavior appears to be a local effect, causing the largest changes for Xe atoms next to the alkali metal adatoms. An increase in the Xe–graphite stretching frequency is also observed with inelastic He-atom scattering, consistent with the stronger adsorption of Xe. We observed no evidence for Xe adsorption onto full alkali metal overlayers down to 40 K, consistent with theoretical studies which indicate small physisorption well depths for rare gases on alkali metal surfaces. [ABSTRACT FROM AUTHOR]

During the first observing run of LIGO, two gravitational wave events and one lower-significance trigger (LVT151012) were reported by the LIGO/Virgo collaboration. At the time of LVT151012, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) was pointing at a region of the sky coincident with the high localization probability area of the event and thus permitted us to search for its electromagnetic counterpart (both prompt and afterglow emission). The imaging instruments on board INTEGRAL (IBIS/ISGRI, IBIS/PICsIT, SPI, and the two JEM-X modules) have been exploited to attempt the detection of any electromagnetic emission associated with LVT151012 over three decades in energy (from 3 keV to 8 MeV). The omni-directional instruments on board the satellite, i.e., the SPI-ACS and the IBIS/Veto, complemented the capabilities of the IBIS/ISGRI and IBIS/PICsIT for detections outside their imaging field of view in order to provide an efficient monitoring of the entire LVT151012 localization region at energies above 75 keV. We did not find any significant transient source that was spatially and/or temporally coincident with LVT151012, obtaining tight upper limits on the associated hard X-ray and γ-ray radiation. For typical spectral models, the upper limits on the fluence of the emission from any 1 s counterpart of LVT151012 ranges from Fγ = 3.5 × 10-8 erg cm-2 (20–200 keV), within the field of view of the imaging instruments, to Fγ = 7.1 × 10-7 erg cm-2 (75–2000 keV), considering the least favorable location of the counterpart for a detection by the omni-directional instruments. These results can be interpreted as a tight constraint on the ratio of the isotropic equivalent energy released in the electromagnetic emission to the total energy of the gravitational waves: E75−2000 keV/EGW< 4.4 × 10-5. Finally, we provide an exhaustive summary of the capabilities of all instruments on board INTEGRAL to hunt for γ-ray counterparts of gravitational wave events, exploiting both serendipitous and pointed follow-up observations. This will serve as a reference for all future searches. [ABSTRACT FROM AUTHOR]

Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z > 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 cm-3) collisionally ionised ISM could produce UV/optical and soft X-ray absorbing column densities that differ by a factor of 10. However the UV/optical and soft X-ray absorbing column densities for such sightlines are 2-3 orders of magnitude lower in comparison to the GRB afterglow spectra. For those GRBs with a larger soft X-ray excess by up to an order of magnitude, the contribution in absorption from a turbulent ISM as considered here would ease the required conditions of additional absorbing components, such as the GRB circumburst medium and intergalactic medium. [ABSTRACT FROM AUTHOR]