352 research outputs found
Multi-layer Gaussian-based multi-configuration time-dependent Hartree (ML-GMCTDH) simulations of ultrafast charge separation in a donor–acceptor complex
We report on first applications of the Multi-Layer Gaussian-based Multi-Configuration Time-Dependent Hartree (ML-GMCTDH) method [Römer et al., J. Chem. Phys. 138, 064106 (2013)] beyond its basic two-layer variant. The ML-GMCTDH scheme provides an embedding of a variationally evolving Gaussian wavepacket basis into a hierarchical tensor representation of the wavefunction. A first-principles parameterized model Hamiltonian for ultrafast non-adiabatic dynamics in an oligothiophene–fullerene charge transfer complex is employed, relying on a two-state linear vibronic coupling model that combines a distribution of tuning type modes with an intermolecular coordinate that also modulates the electronic coupling. Efficient ML-GMCTDH simulations are carried out for up to 300 vibrational modes using an implementation within the QUANTICS program. Excellent agreement with reference ML-MCTDH calculations is obtained
Spitzer-IRAC survey of molecular jets in Vela-D
We present a survey of H2 jets from young protostars in the Vela-D molecular
cloud (VMR-D), based on Spitzer -IRAC data between 3.6 and 8.0 micron. Our
search has led to the identification of 15 jets and about 70 well aligned knots
within 1.2 squared degree. We compare the IRAC maps with observations of the H2
1-0 S(1) line at 2.12 micron, with a Spitzer-MIPS map at 24 and 70 micron, and
with a map of the dust continuum emission at 1.2 mm. We find a association
between molecular jets and dust peaks. The jet candidate exciting sources have
been searched for in the published catalog of the Young Stellar Objects of
VMR-D. We selected all the sources of Class II or earlier which are located
close to the jet center and aligned with it.The association between jet and
exciting source was validated by estimating the differential extinction between
the jet opposite lobes. We are able to find a best-candidate exciting source in
all but two jets. Four exciting sources are not (or very barely) observed at
wavelengths shorter than 24 micron, suggesting they are very young protostars.
Three of them are also associated with the most compact jets. The exciting
source Spectral Energy Distributions have been modeled by means of the
photometric data between 1.2 micron and 1.2 mm. From SEDs fits we derive the
main source parameters, which indicate that most of them are low-mass
protostars. A significant correlation is found between the projected jet length
and the [24] - [70] color, which is consistent with an evolutionary scenario
according to which shorter jets are associated with younger sources. A rough
correlation is found between IRAC line cooling and exciting source bolometric
luminosity, in agreement with the previous literature. The emerging trend
suggests that mass loss and mass accretion are tightly related phenomena and
that both decrease with time.Comment: Accepted by The Astrophysical Journa
A RANDOMIZED, DOUBLE-BLIND, CROSS-OVER STUDY COMPARING A LEVOSULPIRIDE-BASED AND A METOCLOPRAMIDE-BASED COMBINATION IN THE PREVENTION OF PROMECE-CYTABOM-INDUCED EMESIS
Background. To test two different antiemetic regimens for preventing nausea and vomiting in patients with non-Hodgkin's lymphoma (NHL) undergoing systemic chemotherapy (CT) with ProMECE-CytaBOM (P-C). Patients and Methods. Twenty consecutive untreated adult outpatients with histologically confirmed NHL and scheduled to receive P-C chemotherapy were registered in a randomized, double-blind, cross-over study to compare the antiemetic efficacy of a levosulpiride (LS)-based and metoclopramide (MTC)-based regimen. Results. Complete protection from vomiting was recorded in 93% (62/67) of courses with the LS-regimen and in 89% (62/70) with the MTC-regimen (p = 0.428). No nausea was observed in 84% (56/67) of courses with the LS-regimen and in 74% (52/70) with the MTC-regimen (p = 0.183). No differences in prevention of emesis were recorded when patients crossed to the other regimen. Both regimens were well tolerated; however, on day 8 of chemotherapy, when both antiemetic regimens were administered at a higher dose, the LS-based combination showed significantly lower toxicity (p = 0.035). Conclusions. ProMECE-CytaBOM-induced emesis can be prevented in most cases with appropriate, specifically designed antiemetic therapy. Both the LS- and MTC-based combinations resulted in a high percentage of complete protection from emesis, but the higher incidence of side effects observed with MTC makes the LS-based regimen preferable for patients receiving P-C chemotherapy
Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing
High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  1019 cm−3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  1020 cm−3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved
XMM-Newton observation of MACHO 104.20906.960: a dwarf nova candidate with a 2 h period
The binaries known as cataclysmic variables are particular binary systems in
which the primary star (a white dwarf) accretes material from a secondary via
Roche-lobe mechanism. Usually, these objects have orbital period of a few hours
so that a detailed temporal analysis can be performed. Here, we present Chandra
-Newton observations of a dwarf nova candidate identified in the
past by optical observations towards the galactic Bulge and labeled as MACHO
104.20906.960. After a spectral analysis, we used the Lomb-Scargle technique
for the period search and evaluated the confidence level using Monte-Carlo
simulations. In this case, we found that the -ray source shows a period of
hours (3 error) so that it is most likely a
system of interacting objects. The modulation of the signal was found with a
confidence level of 99%. The spectrum can be described by a two thermal
plasma components with X-ray flux in the 0.3--10 keV energy band of
erg s cm. We find that the
distance of the source is approximately 1 kpc thus corresponding to a
luminosity erg s.Comment: 2008, in press on New Astronomy,
(http://www.elsevier.com/wps/find/journaldescription.cws_home/601274/description#description);
XMM-Newton observation of MACHO 104.20906.960: a dwarf nova candidate with a
2 h perio
The YSO Population in the Vela-D Molecular Cloud
We investigate the young stellar population in the Vela Molecular Ridge,
Cloud-D (VMR-D), a star forming (SF) region observed by both Spitzer/NASA and
Herschel/ESA space telescope. The point source, band-merged, Spitzer-IRAC
catalog complemented with MIPS photometry previously obtained is used to search
for candidate young stellar objects (YSO), also including sources detected in
less than four IRAC bands. Bona fide YSO are selected by using appropriate
color-color and color-magnitude criteria aimed to exclude both Galatic and
extragalactic contaminants. The derived star formation rate and efficiency are
compared with the same quantities characterizing other SF clouds. Additional
photometric data, spanning from the near-IR to the submillimeter, are used to
evaluate both bolometric luminosity and temperature for 33 YSOs located in a
region of the cloud observed by both Spitzer and Herschel. The
luminosity-temperature diagram suggests that some of these sources are
representative of Class 0 objects with bolometric temperatures below 70 K and
luminosities of the order of the solar luminosity. Far IR observations from the
Herschel/Hi-GAL key project for a survey of the Galactic plane are also used to
obtain a band-merged photometric catalog of Herschel sources aimed to
independently search for protostars. We find 122 Herschel cores located on the
molecular cloud, 30 of which are protostellar and 92 starless. The global
protostellar luminosity function is obtained by merging the Spitzer and
Herschel protostars. Considering that 10 protostars are found in both Spitzer
and Herschel list it follows that in the investigated region we find 53
protostars and that the Spitzer selected protostars account for approximately
two-thirds of the total.Comment: 40 pages, 12 figures, accepted for publication in Ap
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