1,156 research outputs found
Evidence of environmental strains on charge injection in silole based organic light emitting diodes
Using d. functional theory (DFT) computations, the authors demonstrated a
substantial skeletal relaxation when the structure of
2,5-bis-[4-anthracene-9-yl-phenyl]-1,1-dimethyl-3,4-diphenyl-silole (BAS) is
optimized in the gas-phase comparing with the mol. structure detd. from
monocrystal x-ray diffraction. The origin of such a relaxation is explained by
a strong environmental strains induced by the presence of anthracene entities.
Also, the estn. of the frontier orbital levels showed that this structural
relaxation affects mainly the LUMO that is lowered of 190 meV in the gas phase.
To check if these theor. findings would be confirmed for thin films of BAS, the
authors turned to UV photoemission spectroscopy and/or inverse photoemission
spectroscopy and electrooptical measurements. The study of the c.d. or voltage
and luminance or voltage characteristics of an ITO/PEDOT/BAS/Au device clearly
demonstrated a very unusual temp.-dependent behavior. Using a thermally
assisted tunnel transfer model, this behavior likely originated from the
variation of the electronic affinity of the silole deriv. with the temp. The
thermal agitation relaxes the mol. strains in thin films as it is shown when
passing from the cryst. to the gas phase. The relaxation of the intramol. thus
induces an increase of the electronic affinity and, as a consequence, the more
efficient electron injection in org. light-emitting diodes
Covalent triazine frameworks based on the first pseudo-octahedral hexanitrile monomer via nitrile trimerization: Synthesis, porosity, and CO gas sorption properties
M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]2H2O
The structure of the light-induced metastable state SII of
Na2[Fe(CN)5NO]2H2O 14 was investigated by transmission M\"ossbauer
spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear
inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density
functional theory (DFT) calculations. The DFT and TMS results 17 strongly
support the view that the NO group in SII takes a side-on molecular orientation
18 and, further, is dynamically displaced from one eclipsed, via a staggered,
to a second 19 eclipsed orientation. The population conditions for generating
SII are optimal for 20 measurements by TMS, yet they are modest for
accumulating NIS spectra. Optimization 21 of population conditions for NIS
measurements is discussed and new NIS experiments on 22 SII are proposed
Control Software for the SST-1M Small-Size Telescope prototype for the Cherenkov Telescope Array
The SST-1M is a 4-m Davies--Cotton atmospheric Cherenkov telescope optimized
to provide gamma-ray sensitivity above a few TeV. The SST-1M is proposed as
part of the Small-Size Telescope array for the Cherenkov Telescope Array (CTA),
the first prototype has already been deployed. The SST-1M control software of
all subsystems (active mirror control, drive system, safety system,
photo-detection plane, DigiCam, CCD cameras) and the whole telescope itself
(master controller) uses the standard software design proposed for all CTA
telescopes based on the ALMA Common Software (ACS) developed to control the
Atacama Large Millimeter Array (ALMA). Each subsystem is represented by a
separate ACS component, which handles the communication to and the operation of
the subsystem. Interfacing with the actual hardware is performed via the OPC UA
communication protocol, supported either natively by dedicated industrial
standard servers (PLCs) or separate service applications developed to wrap
lower level protocols (e.g. CAN bus, camera slow control) into OPC UA. Early
operations of the telescope without the camera were already carried out. The
camera is fully assembled and is capable to perform data acquisition using
artificial light source.Comment: In Proceedings of the 35th International Cosmic Ray Conference
(ICRC2017), Busan, Korea. All CTA contributions at arXiv:1709.0348
Quest for barley canopy architecture genes in the hortillus population and whealbi germplasm collection
Barley grains are predominantly used for animal feed and malting, and breeding traditionally focused on increase of grain yield by partitioning biomass from straw to grains. The increasing demand for renewable energy sources makes straw, and specially barley straw characterized by the largest content of carbohydrates among the cereals, a valuable product for its potential conversion into biofuels and other products. The BarPLUS project aims at finding genes, alleles and candidate lines related to barley canopy architecture and photosynthesis, to maximize barley biomass and yield (https://barplus.wordpress.com/). In this framework, our research group focuses on identifying genes and alleles controlling tillering, leaf size and leaf angle traits in barley by exploiting both induced and natural allelic variation. Using a forward genetics approach, we screened the HorTILLUS population (Szurman-Zubrzycka et al., 2018) under both field and controlled conditions, identifying 5 mutants with increased tillering and/or erect leaves. After crossing with four reference cultivars, pools of F2 wild-type and mutant plants were selected to map and identify the underlying genes by exome sequencing (Mascher et al., 2014). In parallel, TILLING of the HorTILLUS population identified four lines carrying mutations in the LBO (Lateral branching oxidoreductase) gene involved in tiller number. In order to explore also natural genetic variation, we are taking advantage of the \u2018WHEALBI\u2019 germplasm collection, which includes 403 exome sequenced diverse accessions (BustosKorts et al., 2019): a field trial on a subset of 240 lines (Fiorenzuola d\u2019Arda, Italy) allowed us to conduct a preliminary genome wide association study based on high-throughput phenotyping for leaf angle (PocketPlant3D smartphone app) and quantitative image-analysis for leaf size. Results will be compared with those from a greenhouse experiment on the same 240 accessions to analyze a wide range of morphological traits and identify associated markers and genomic regions
Philosophy and Science in Leibniz
This paper explores the question of Leibniz’s contribution to the rise of modern ‘science’. To be sure, it is now generally agreed that the modern category of ‘science’ did not exist in the early modern period. At the same time, this period witnessed a very important stage in the process from which modern science eventually emerged. My discussion will be aimed at uncovering the new enterprise, and the new distinctions which were taking shape in the early modern period under the banner of the old Aristotelian terminology. I will argue that Leibniz begins to theorize a distinction between physics and metaphysics that tracks our distinction between the autonomous enterprise of science in its modern meaning, and the enterprise of philosophy. I will try to show that, for Leibniz, physics proper is the study of natural phenomena in mathematical and mechanical terms without recourse for its explanations to metaphysical notions. This autonomy, however, does not imply for Leibniz that physics can say on its own all that there is to be said about the natural world. Quite the opposite. Leibniz inherits from the Aristotelian tradition the view that physics needs metaphysical roots or a metaphysical grounding. For Leibniz, what is ultimately real is reached by metaphysics, not by physics. This is, in my view, Leibniz’s chief insight: the new mathematical physics is an autonomous enterprise which offers its own kind of explanations but does not exhaust what can (and should) be said about the natural world
Detailed spectral and morphological analysis of the shell type SNR RCW 86
Aims: We aim for an understanding of the morphological and spectral
properties of the supernova remnant RCW~86 and for insights into the production
mechanism leading to the RCW~86 very high-energy gamma-ray emission. Methods:
We analyzed High Energy Spectroscopic System data that had increased
sensitivity compared to the observations presented in the RCW~86 H.E.S.S.
discovery publication. Studies of the morphological correlation between the
0.5-1~keV X-ray band, the 2-5~keV X-ray band, radio, and gamma-ray emissions
have been performed as well as broadband modeling of the spectral energy
distribution with two different emission models. Results:We present the first
conclusive evidence that the TeV gamma-ray emission region is shell-like based
on our morphological studies. The comparison with 2-5~keV X-ray data reveals a
correlation with the 0.4-50~TeV gamma-ray emission.The spectrum of RCW~86 is
best described by a power law with an exponential cutoff at TeV and a spectral index of ~. A static
leptonic one-zone model adequately describes the measured spectral energy
distribution of RCW~86, with the resultant total kinetic energy of the
electrons above 1 GeV being equivalent to 0.1\% of the initial kinetic
energy of a Type I a supernova explosion. When using a hadronic model, a
magnetic field of ~100G is needed to represent the measured data.
Although this is comparable to formerly published estimates, a standard
E spectrum for the proton distribution cannot describe the gamma-ray
data. Instead, a spectral index of ~1.7 would be required, which
implies that ~erg has been transferred into
high-energy protons with the effective density cm^-3. This
is about 10\% of the kinetic energy of a typical Type Ia supernova under the
assumption of a density of 1~cm^-3.Comment: accepted for publication by A&
Characterizing the gamma-ray long-term variability of PKS 2155-304 with H.E.S.S. and Fermi-LAT
Studying the temporal variability of BL Lac objects at the highest energies
provides unique insights into the extreme physical processes occurring in
relativistic jets and in the vicinity of super-massive black holes. To this
end, the long-term variability of the BL Lac object PKS 2155-304 is analyzed in
the high (HE, 100 MeV 200 GeV)
gamma-ray domain. Over the course of ~9 yr of H.E.S.S observations the VHE
light curve in the quiescent state is consistent with a log-normal behavior.
The VHE variability in this state is well described by flicker noise
(power-spectral-density index {\ss}_VHE = 1.10 +0.10 -0.13) on time scales
larger than one day. An analysis of 5.5 yr of HE Fermi LAT data gives
consistent results ({\ss}_HE = 1.20 +0.21 -0.23, on time scales larger than 10
days) compatible with the VHE findings. The HE and VHE power spectral densities
show a scale invariance across the probed time ranges. A direct linear
correlation between the VHE and HE fluxes could neither be excluded nor firmly
established. These long-term-variability properties are discussed and compared
to the red noise behavior ({\ss} ~ 2) seen on shorter time scales during
VHE-flaring states. The difference in power spectral noise behavior at VHE
energies during quiescent and flaring states provides evidence that these
states are influenced by different physical processes, while the compatibility
of the HE and VHE long-term results is suggestive of a common physical link as
it might be introduced by an underlying jet-disk connection.Comment: 11 pages, 16 figure
The exceptionally powerful TeV gamma-ray emitters in the Large Magellanic Cloud
The Large Magellanic Cloud, a satellite galaxy of the Milky Way, has been
observed with the High Energy Stereoscopic System (H.E.S.S.) above an energy of
100 billion electron volts for a deep exposure of 210 hours. Three sources of
different types were detected: the pulsar wind nebula of the most energetic
pulsar known N 157B, the radio-loud supernova remnant N 132D and the largest
non-thermal X-ray shell - the superbubble 30 Dor C. The unique object SN 1987A
is, surprisingly, not detected, which constrains the theoretical framework of
particle acceleration in very young supernova remnants. These detections reveal
the most energetic tip of a gamma-ray source population in an external galaxy,
and provide via 30 Dor C the unambiguous detection of gamma-ray emission from a
superbubble.Comment: Published in Science Magazine (Jan. 23, 2015). This ArXiv version has
the supplementary online material incorporated as an appendix to the main
pape
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