11,465 research outputs found
Fully anharmonic infrared cascade spectra of polycyclic aromatic hydrocarbons
The infrared (IR) emission of polycyclic aromatic hydrocarbons (PAHs)
permeates our universe; astronomers have detected the IR signatures of PAHs
around many interstellar objects. The IR emission of interstellar PAHs differs
from their emission as seen under conditions on Earth, as they emit through a
collisionless cascade down through their excited vibrational states from high
internal energies. The difficulty in reproducing interstellar conditions in the
laboratory results in a reliance on theoretical techniques. However, the size
and complexity of PAHs requires careful consideration when producing the
theoretical spectra. In this work we outline the theoretical methods necessary
to lead to a fully theoretical IR cascade spectra of PAHs including: an
anharmonic second order vibrational perturbation theory (VPT2) treatment; the
inclusion of Fermi resonances through polyads; and the calculation of
anharmonic temperature band shifts and broadenings (including resonances)
through a Wang--Landau approach. We also suggest a simplified scheme to
calculate vibrational emission spectra that retains the essential
characteristics of the full IR cascade treatment and can directly transform low
temperature absorption spectra in IR cascade spectra. Additionally we show that
past astronomical models were in error in assuming a 15 cm correction
was needed to account for anharmonic emission effects
Laboratory gas-phase infrared spectra of two astronomically relevant PAH cations: diindenoperylene, CH and dicoronylene, CH
The first gas-phase infrared spectra of two isolated astronomically relevant
and large PAH cations - diindenoperylene (DIP) and dicoronylene (DC) - in the
5301800 cm (18.95.6 m) range - are presented. Vibrational
band positions are determined for comparison to the aromatic infrared bands
(AIBs). The spectra are obtained via infrared multiphoton dissociation (IRMPD)
spectroscopy of ions stored in a quadrupole ion trap (QIT) using the intense
and tunable radiation of the free electron laser for infrared experiments
(FELIX). DIP shows its main absorption peaks at 737 (13.57), 800 (12.50),
1001 (9.99), 1070 (9.35), 1115 (8.97), 1152 (8.68), 1278 (7.83), 1420 (7.04)
and 1550 (6.45) cm(m), in good agreement with DFT calculations that
are uniformly scaled to take anharmonicities into account. DC has its main
absorption peaks at 853 (11.72), 876 (11.42), 1032 (9.69), 1168 (8.56), 1300
(7.69), 1427 (7.01) and 1566 (6.39) cm(m), that also agree well
with the scaled DFT results presented here.
The DIP and DC spectra are compared with the prominent infrared
features observed towards NGC 7023. This results both in matches and clear
deviations. Moreover, in the 11.014.0 m region, specific bands can be
linked to CH out-of-plane (oop) bending modes of different CH edge structures
in large PAHs. The molecular origin of these findings and their astronomical
relevance are discussed
Holographic duals of 6d RG flows
A notable class of superconformal theories (SCFTs) in six dimensions is
parameterized by an integer , an ADE group , and two nilpotent elements
in . Nilpotent elements have a natural partial ordering,
which has been conjectured to coincide with the hierarchy of
renormalization-group flows among the SCFTs. In this paper we test this
conjecture for , where AdS duals exist in IIA. We work
with a seven-dimensional gauged supergravity, consisting of the gravity
multiplet and two non-Abelian vector multiplets. We show that
this theory has many supersymmetric AdS vacua, determined by two nilpotent
elements, which are naturally interpreted as IIA AdS solutions. The BPS
equations for domain walls connecting two such vacua can be solved
analytically, up to a Nahm equation with certain boundary conditions. The
latter admit a solution connecting two vacua if and only if the corresponding
nilpotent elements are related by the natural partial ordering, in agreement
with the field theory conjecture.Comment: 33 pages, 2 figure
Mothers and fathers with Binge Eating Disorder and their 18-36 months old children: a longitudinal study on parent-infant interactions and offspring\u2019s emotional-behavioral profiles
Maternal Binge Eating Disorder (BED) has been suggested to be associated with poor parent\u2013infant interactions during feeding and with children\u2019s emotional and behavioral problems during infancy (Blissett and Haycraft, 2011). The role of fathers has received increasing consideration in recent years, yet the research has not focused on interactional patterns between fathers with BED and their children. The present study aimed to longitudinally investigate the in\ufb02uence of BED diagnosis, in one or both parents, on parent\u2013infant feeding interactions and on children\u2019s emotional\u2013behavioral functioning. 612 subjects (408 parents; 204 children), recruited in mental health services and pre-schools in Central Italy, were divided into four groups: Group 1 included families with both parents diagnosed with BED, Group 2 and 3 included families with one parent diagnosed with BED, Group 0 was a healthy control. The assessment took place at T1 (18 months of age of children) and T2 (36 months of age of children):
feeding interactions were assessed through the Scale for the Assessment of Feeding Interactions (SVIA) while child emotional\u2013behavioral functioning was evaluated with the Child Behavior Check-List (CBCL). When compared to healthy controls, the groups with one or both parents diagnosed with BED showed higher scores on the SVIA and on the CBCL internalizing and externalizing scales, indicating poorer adult\u2013child feeding interactions and higher emotional\u2013behavioral dif\ufb01culties. A direct in\ufb02uence of parental psychiatric diagnosis on the quality of mother\u2013infant and father\u2013infant interactions was also found, both at T1 and T2. Moreover, dyadic feeding interactions mediated the in\ufb02uence of parental diagnosis on children\u2019s psychological functioning. The presence of BED diagnosis in one or both parents seems to in\ufb02uence the severity of maladaptive
parent\u2013infant exchanges during feeding and offspring\u2019s emotional\u2013behavioral problems over time, consequently affecting different areas of children\u2019s psychological functioning. This is the \ufb01rst study to demonstrate the speci\ufb01c effects of maternal and paternal BED on infant development. These results could inform prevention and intervention programs in families with one or both parents diagnosed with BED
Intensity correlations, entanglement properties and ghost imaging in multimode thermal-seeded parametric downconversion: Theory
We address parametric-downconversion seeded by multimode pseudo-thermal
fields. We show that this process may be used to generate multimode pairwise
correlated states with entanglement properties that can be tuned by controlling
the seed intensities. Multimode pseudo-thermal fields seeded
parametric-downconversion represents a novel source of correlated states, which
allows one to explore the classical-quantum transition in pairwise correlations
and to realize ghost imaging and ghost diffraction in regimes not yet explored
by experiments.Comment: 9 pages, 3 figure
Regional Sea Level Rise Along the United States Coasts
Over the past several years, there has been several studies focused on reconstructing global mean sea level (GMSL) for the 20th century, along with projecting rates out into the future. Of greater importance for mitigation and adaptation plans, however, is the rate of local or regional sea level (RSL) rise. Ocean dynamics along with changes in Earth’s gravitational field can cause RSL to deviate from the change in GMSL. During the satellite altimeter era covering the past two decades, RSL trends can be four times the global average, with much of this spatial variation due to internal climate variability. Isolating the long-term signal that may be expected to persist into the future, or from which an acceleration can be estimated, is a challenge with the short satellite record. Prior to the satellite altimeter era, tide gauges must be used to study past sea level variability. Tide gauges suffer from sampling challenges that make regional studies difficult, and as a result, there has been relatively little discussion and few comprehensive efforts on reproducing long-term RSL trends.
This work aims to determine the 20th century regional pattern of sea level rise by reducing the tide gauge data to a usable subset and taking into account the factors that cause spatial variability in trends on long time-scales. This provides an estimate of secular changes leading to RSL rise associated with anthropogenic affects. Either exacerbating or suppressing these regional trends is natural internal climate variability. By determining the frequency and magnitude of these inter-annual to decadal events, we can determine a baseline of future RSL along the East and West coast of the United states. This is an important step for mitigation and adaptation plans, since high frequency events such as storms and high tides will be coupled with RSL rise, causing increased flooding and inundation. As such, we will determine future nuisance flooding in Norfolk, VA, arising from a combination of sea level contributors from tides to internal climate variability
An improved effective-one-body Hamiltonian for spinning black-hole binaries
Building on a recent paper in which we computed the canonical Hamiltonian of
a spinning test particle in curved spacetime, at linear order in the particle's
spin, we work out an improved effective-one-body (EOB) Hamiltonian for spinning
black-hole binaries. As in previous descriptions, we endow the effective
particle not only with a mass m, but also with a spin S*. Thus, the effective
particle interacts with the effective Kerr background (having spin S_Kerr)
through a geodesic-type interaction and an additional spin-dependent
interaction proportional to S*. When expanded in post-Newtonian (PN) orders,
the EOB Hamiltonian reproduces the leading order spin-spin coupling and the
spin-orbit coupling through 2.5PN order, for any mass-ratio. Also, it
reproduces all spin-orbit couplings in the test-particle limit. Similarly to
the test-particle limit case, when we restrict the EOB dynamics to spins
aligned or antialigned with the orbital angular momentum, for which circular
orbits exist, the EOB dynamics has several interesting features, such as the
existence of an innermost stable circular orbit, a photon circular orbit, and a
maximum in the orbital frequency during the plunge subsequent to the inspiral.
These properties are crucial for reproducing the dynamics and
gravitational-wave emission of spinning black-hole binaries, as calculated in
numerical relativity simulations.Comment: 22 pages, 9 figures. Minor changes to match version accepted for
publication in PR
Performance and genome-centric metagenomics of thermophilic single and two-stage anaerobic digesters treating cheese wastes
The present research is the first comprehensive study regarding the thermophilic anaerobic degradation of cheese wastewater, which combines the evaluation of different reactor configurations (i.e. single and two-stage continuous stirred tank reactors) on the process efficiency and the in-depth characterization of the microbial community structure using genome-centric metagenomics. Both reactor configurations showed acidification problems under the tested organic loading rates (OLRs) of 3.6 and 2.4 g COD/L-reactor day and the hydraulic retention time (HRT) of 15 days. However, the two-stage design reached a methane yield equal to 95% of the theoretical value, in contrast with the single stage configuration, which reached a maximum of 33% of the theoretical methane yield. The metagenomic analysis identified 22 new population genomes and revealed that the microbial compositions between the two configurations were remarkably different, demonstrating a higher methanogenic biodiversity in the two-stage configuration. In fact, the acidogenic reactor of the serial configuration was almost solely composed by the lactose degrader Bifidobacterium crudilactis UC0001. The predictive functional analyses of the main population genomes highlighted specific metabolic pathways responsible for the AD process and the mechanisms of main intermediates production. Particularly, the acetate accumulation experienced by the single stage configuration was mainly correlated to the low abundant syntrophic acetate oxidizer Tepidanaerobacter acetatoxydans UC0018 and to the absence of aceticlastic methanogens
The quantum-classical transition in thermally seeded parametric downconversion
We address the pair of conjugated field modes obtained from
parametric-downconversion as a convenient system to analyze the
quantum-classical transition in the continuous variable regime. We explicitly
evaluate intensity correlations, negativity and entanglement for the system in
a thermal state and show that a hierarchy of nonclassicality thresholds
naturally emerges in terms of thermal and downconversion photon number. We show
that the transition from quantum to classical regime may be tuned by
controlling the intensities of the seeds and detected by intensity
measurements. Besides, we show that the thresholds are not affected by losses,
which only modify the amount of nonclassicality. The multimode case is also
analyzed in some detail.Comment: 12 pages, 3 figure
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