TY  - JOUR
A1  - Kim, Kyung-Chan
A1  - Shprits, Yuri Y.
T1  - Survey of the Favorable Conditions for Magnetosonic Wave Excitation
JF  - Journal of geophysical research : Space physics
N2  - The ratio of the proton ring velocity (VR) to the local Alfven speed (VA), in addition to proton ring distributions, plays a key factor in the excitation of magnetosonic waves at frequencies between the proton cyclotron frequency fcp and the lower hybrid resonance frequency fLHR in the Earth's magnetosphere. Here we investigate whether there is a statistically significant relationship between occurrences of proton rings and magnetosonic waves both outside and inside the plasmapause using particle and wave data from Van Allen Probe-A during the time period of October 2012 to December 2015. We also perform a statistical survey of the ratio of the ring energy (ER, corresponding to VR) to the Alfven energy (EA, corresponding to VA) to determine the favorable conditions under which magnetosonic waves in each of two frequency bands (fcp < f ≤ 0.5 fLHR and 0.5 fLHR < f < fLHR) can be excited. The results show that the magnetosonic waves in both frequency bands occur around the postnoon (12–18 magnetic local time, MLT) sector outside the plasmapause when ER is comparable to or lower than EA, and those in lower-frequency bands (fcp < f ≤ 0.5 fLHR) occur around the postnoon sector inside the plasmapause when ER/EA > ~9. However, there is one discrepancy between occurrences of proton rings and magnetosonic waves in low-frequency bands around the prenoon sector (6–12 MLT) outside the plasmapause, which suggests either that the waves may have propagated during active time from the postnoon sector after being excited during quiet time, or they may have locally excited in the prenoon sector during active time.
Y1  - 2018
U6  - https://doi.org/10.1002/2017JA024865
SN  - 2169-9380
SN  - 2169-9402
VL  - 123
IS  - 1
SP  - 400
EP  - 413
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Klamroth, Tillmann
T1  - Local resonances in STM manipulation of chlorobenzene on Si(111)-7x7
BT  - performance of different cluster models and density functionals
JF  - Molecular physics
N2  - Hot localised charge carriers on the Si(111)-7x7 surface are modelled by small charged clusters. Such resonances induce non-local desorption, i.e. more than 10 nm away from the injection site, of chlorobenzene in scanning tunnelling microscope experiments. We used such a cluster model to characterise resonance localisation and vibrational activation for positive and negative resonances recently. In this work, we investigate to which extent the model depends on details of the used cluster or quantum chemistry methods and try to identify the smallest possible cluster suitable for a description of the neutral surface and the ion resonances. Furthermore, a detailed analysis for different chemisorption orientations is performed. While some properties, as estimates of the resonance energy or absolute values for atomic changes, show such a dependency, the main findings are very robust with respect to changes in the model and/or the chemisorption geometry. [GRAPHICS] .
KW  - DFT
KW  - cluster model
KW  - charge localisation
KW  - STM
Y1  - 2018
U6  - https://doi.org/10.1080/00268976.2018.1442939
SN  - 0026-8976
SN  - 1362-3028
VL  - 116
IS  - 13
SP  - 1687
EP  - 1696
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Martinez-Chicharro, M.
A1  - Torrejon, J. M.
A1  - Oskinova, Lida
A1  - Furst, F.
A1  - Postnov, K.
A1  - Rodes-Roca, J. J.
A1  - Hainich, Rainer
A1  - Bodaghee, A.
T1  - Evidence of Compton cooling during an X-ray flare supports a neutron star nature of the compact object in 4U1700-37
JF  - Monthly notices of the Royal Astronomical Society
N2  - Based on new Chandra X-ray telescope data, we present empirical evidence of plasma Compton cooling during a flare in the non-pulsating massive X-ray binary 4U1700-37. This behaviour might be explained by quasi-spherical accretion on to a slowly rotating magnetized neutron star (NS). In quiescence, the NS in 4U1700-37 is surrounded by a hot radiatively cooling shell. Its presence is supported by the detection of mHz quasi-periodic oscillations likely produced by its convection cells. The high plasma temperature and the relatively low X-ray luminosity observed during the quiescence, point to a small emitting area similar to 1 km, compatible with a hotspot on an NS surface. The sudden transition from a radiative to a significantly more efficient Compton cooling regime triggers an episode of enhanced accretion resulting in a flare. During the flare, the plasma temperature drops quickly. The predicted luminosity for such transitions, similar to 3 x 10(35) erg s(-1), is very close to the luminosity of 4U1700-37 during quiescence. The transition may be caused by the accretion of a clump in the stellar wind of the donor star. Thus, a magnetized NS nature of the compact object is strongly favoured.
KW  - stars: individual: 4U1700-37
KW  - V*V884 Sco
KW  - X-rays: binaries
Y1  - 2017
U6  - https://doi.org/10.1093/mnrasl/slx165
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 1
SP  - L74
EP  - L78
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Willner, Sven N.
A1  - Levermann, Anders
A1  - Zhao, Fang
A1  - Frieler, Katja
T1  - Adaptation required to preserve future high-end river flood risk at present levels
JF  - Science Advances
N2  - Earth’s surface temperature will continue to rise for another 20 to 30 years even with the strongest carbon emission reduction currently considered. The associated changes in rainfall patterns can result in an increased flood risk worldwide. We compute the required increase in flood protection to keep high-end fluvial flood risk at present levels. The analysis is carried out worldwide for subnational administrative units. Most of the United States, Central Europe, and Northeast and West Africa, as well as large parts of India and Indonesia, require the strongest adaptation effort. More than half of the United States needs to at least double their protection within the next two decades. Thus, the need for adaptation to increased river flood is a global problem affecting industrialized regions as much as developing countries.
Y1  - 2018
U6  - https://doi.org/10.1126/sciadv.aao1914
SN  - 2375-2548
VL  - 4
IS  - 1
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Thiede, Tobias
A1  - Cabeza, Sandra
A1  - Mishurova, Tatiana
A1  - Nadammal, Naresh
A1  - Kromm, Arne
A1  - Bode, Johannes
A1  - Haberland, Christoph
A1  - Bruno, Giovanni
T1  - Residual Stress in Selective Laser Melted Inconel 718
BT  - Influence of the Removal from Base Plate and Deposition Hatch Length
JF  - Materials performance and characterization
N2  - The residual stress distribution in IN718 elongated prisms produced by selective laser melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed from the base plate (RE) were characterized. While surface stress fields seem constant for the AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e., with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the base plate.
KW  - residual stress
KW  - IN718
KW  - neutron diffraction
KW  - laboratory x-ray diffraction
KW  - additive manufacturing
KW  - selective laser melting
KW  - coordinate measurement machine
Y1  - 2018
U6  - https://doi.org/10.1520/MPC20170119
SN  - 2379-1365
SN  - 2165-3992
VL  - 7
IS  - 4
SP  - 717
EP  - 735
PB  - American Society for Testing and Materials
CY  - West Conshohocken
ER  - 
TY  - JOUR
A1  - Kretschmer, Marlene
A1  - Coumou, Dim
A1  - Agel, Laurie
A1  - Barlow, Mathew
A1  - Tziperman, Eli
A1  - Cohen, Judah
T1  - More-Persistent weak stratospheric polar vortex states linked to cold extremes
JF  - Bulletin of the American Meteorological Society
N2  - The extratropical stratosphere in boreal winter is characterized by a strong circumpolar westerly jet, confining the coldest temperatures at high latitudes. The jet, referred to as the stratospheric polar vortex, is predominantly zonal and centered around the pole; however, it does exhibit large variability in wind speed and location. Previous studies showed that a weak stratospheric polar vortex can lead to cold-air outbreaks in the midlatitudes, but the exact relationships and mechanisms are unclear. Particularly, it is unclear whether stratospheric variability has contributed to the observed anomalous cooling trends in midlatitude Eurasia. Using hierarchical clustering, we show that over the last 37 years, the frequency of weak vortex states in mid- to late winter (January and February) has increased, which was accompanied by subsequent cold extremes in midlatitude Eurasia. For this region, 60% of the observed cooling in the era of Arctic amplification, that is, since 1990, can be explained by the increased frequency of weak stratospheric polar vortex states, a number that increases to almost 80% when El Nino-Southern Oscillation (ENSO) variability is included as well.
Y1  - 2018
U6  - https://doi.org/10.1175/BAMS-D-16-0259.1
SN  - 0003-0007
SN  - 1520-0477
VL  - 99
IS  - 1
SP  - 49
EP  - 60
PB  - American Meteorological Soc.
CY  - Boston
ER  - 
TY  - JOUR
A1  - Ryll, Britta
A1  - Schmitz, Andreas
A1  - de Boor, Johannes
A1  - Franz, Alexandra
A1  - Whitfield, Pamela S.
A1  - Reehuis, Manfred
A1  - Hoser, Andreas
A1  - Müller, Eckhard
A1  - Habicht, Klaus
A1  - Fritscht, Katharina
T1  - Structure, phase composition, and thermoelectric properties of YbxCo4Sb12 and their dependence on synthesis method
JF  - ACS applied energy materials
N2  - We present a combined microscopic and macroscopic study of YbxCo4Sb12 skutterudites for a range of nominal filling fractions, 0.15 < x < 0.75. The samples were synthesized using two different methods — a melt–quench–annealing route in evacuated quartz ampoules and a non-equilibrium ball-mill route — for which we directly compare the crystal structure and phase composition as well as the thermoelectric properties. Rietveld refinements of high-quality neutron powder diffraction data reveal about a 30–40% smaller Yb occupancy on the crystallographic 2a site than nominally expected for both synthesis routes. We observe a maximum filling fraction of at least 0.439(7) for a sample synthesized by the ball-mill routine, exceeding theoretical predictions of the filling fraction limit of 0.2–0.3. A single secondary phase of CoSb2 is observed in ball-mill-synthesized samples, while two secondary phases, CoSb2 and YbSb2, are detected for samples prepared by the ampoule route. A detrimental influence of the secondary phases on the thermoelectric properties is observed for secondary-phase fractions larger than 8 wt % regardless of the kind of secondary phase. The largest figure of merit of all samples with a ZT ∼ 1.0 at 723 K is observed for the sample with a refined Yb content of x2a = 0.159(3), synthesized by the ampoule route.
KW  - thermoelectric materials
KW  - skutterudite
KW  - melt-quench-anneal
KW  - ball mill
KW  - neutron powder diffraction
KW  - thermoelectric properties
KW  - figure of merit
Y1  - 2017
U6  - https://doi.org/10.1021/acsaem.7b00015
SN  - 2574-0962
VL  - 1
IS  - 1
SP  - 113
EP  - 122
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kretschmer, Marlene
A1  - Cohen, Judah
A1  - Matthias, Vivien
A1  - Runge, Jakob
A1  - Coumou, Dim
T1  - The different stratospheric influence on cold-extremes in Eurasia and North America
JF  - npj Climate and Atmospheric Science
N2  - The stratospheric polar vortex can influence the tropospheric circulation and thereby winter weather in the mid-latitudes. Weak vortex states, often associated with sudden stratospheric warmings (SSW), have been shown to increase the risk of cold-spells especially over Eurasia, but its role for North American winters is less clear. Using cluster analysis, we show that there are two dominant patterns of increased polar cap heights in the lower stratosphere. Both patterns represent a weak polar vortex but they are associated with different wave mechanisms and different regional tropospheric impacts. The first pattern is zonally symmetric and associated with absorbed upward-propagating wave activity, leading to a negative phase of the North Atlantic Oscillation (NAO) and cold-air outbreaks over northern Eurasia. This coupling mechanism is well-documented in the literature and is consistent with the downward migration of the northern annular mode (NAM). The second pattern is zonally asymmetric and linked to downward reflected planetary waves over Canada followed by a negative phase of the Western Pacific Oscillation (WPO) and cold-spells in Central Canada and the Great Lakes region. Causal effect network (CEN) analyses confirm the atmospheric pathways associated with this asymmetric pattern. Moreover, our findings suggest the reflective mechanism to be sensitive to the exact region of upward wave-activity fluxes and to be state-dependent on the strength of the vortex. Identifying the causal pathways that operate on weekly to monthly timescales can pave the way for improved sub-seasonal to seasonal forecasting of cold spells in the mid-latitudes.
Y1  - 2018
U6  - https://doi.org/10.1038/s41612-018-0054-4
SN  - 2397-3722
VL  - 1
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Aydiner, Ekrem
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Wealth distribution, Pareto law, and stretched exponential decay of money
BT  - Computer simulations analysis of agent-based models
JF  - Physica : europhysics journal ; A, Statistical mechanics and its applications
N2  - We study by Monte Carlo simulations a kinetic exchange trading model for both fixed and distributed saving propensities of the agents and rationalize the person and wealth distributions. We show that the newly introduced wealth distribution – that may be more amenable in certain situations – features a different power-law exponent, particularly for distributed saving propensities of the agents. For open agent-based systems, we analyze the person and wealth distributions and find that the presence of trap agents alters their amplitude, leaving however the scaling exponents nearly unaffected. For an open system, we show that the total wealth – for different trap agent densities and saving propensities of the agents – decreases in time according to the classical Kohlrausch–Williams–Watts stretched exponential law. Interestingly, this decay does not depend on the trap agent density, but rather on saving propensities. The system relaxation for fixed and distributed saving schemes are found to be different.
KW  - Econophysics
KW  - Wealth and income distribution
KW  - Pareto law
KW  - Scaling exponents
Y1  - 2017
U6  - https://doi.org/10.1016/j.physa.2017.08.017
SN  - 0378-4371
SN  - 1873-2119
VL  - 490
SP  - 278
EP  - 288
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Davidzon, Iary
A1  - Ilbert, Olivier
A1  - Faisst, Andreas L.
A1  - Sparre, Martin
A1  - Capak, Peter L.
T1  - An Alternate Approach to Measure Specific Star Formation Rates at 2 < z < 7
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We trace the specific star formation rate (sSFR) of massive star-forming galaxies (greater than or similar to 10(10)M(circle dot)) from z similar to 2 to 7. Our method is substantially different from previous analyses, as it does not rely on direct estimates of star formation rate, but on the differential evolution of the galaxy stellar mass function (SMF). We show the reliability of this approach by means of semianalytical and hydrodynamical cosmological simulations. We then apply it to real data, using the SMFs derived in the COSMOS and CANDELS fields. We find that the sSFR is proportional to (1 + z)(1.1) (+/-) (0.2) at z > 2, in agreement with other observations but in tension with the steeper evolution predicted by simulations from z similar to 4 to 2. We investigate the impact of several sources of observational bias, which, however, cannot account for this discrepancy. Although the SMF of high-redshift galaxies is still affected by significant errors, we show that future large-area surveys will substantially reduce them, making our method an effective tool to probe the massive end of the main sequence of star-forming galaxies.
KW  - galaxies: evolution
KW  - galaxies: high-redshift
KW  - galaxies: star formation
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aaa19e
SN  - 0004-637X
SN  - 1538-4357
VL  - 852
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -