1,025 research outputs found
A Second Mortuary Hiatus on Lake Baikal in Siberia and the Arrival of Small-Scale Pastoralism
Peer reviewedPublisher PD
Collisional excitation of doubly and triply deuterated ammonia NDH and ND by H
The availability of collisional rate coefficients is a prerequisite for an
accurate interpretation of astrophysical observations, since the observed media
often harbour densities where molecules are populated under non--LTE
conditions. In the current study, we present calculations of rate coefficients
suitable to describe the various spin isomers of multiply deuterated ammonia,
namely the NDH and ND isotopologues. These calculations are based on
the most accurate NH--H potential energy surface available, which has
been modified to describe the geometrical changes induced by the nuclear
substitutions. The dynamical calculations are performed within the
close--coupling formalism and are carried out in order to provide rate
coefficients up to a temperature of = 50K. For the various
isotopologues/symmetries, we provide rate coefficients for the energy levels
below 100 cm. Subsequently, these new rate coefficients are used
in astrophysical models aimed at reproducing the NHD, NDH and ND
observations previously reported towards the prestellar cores B1b and 16293E.
We thus update the estimates of the corresponding column densities and find a
reasonable agreement with the previous models. In particular, the
ortho--to--para ratios of NHD and NHD are found to be consistent with
the statistical ratios
Ultrafast preparation and strong-field ionization of an atomic Bell-like state
Molecules are many body systems with a substantial amount of entanglement
between their electrons. Is there a way to break the molecular bond of a
diatomic molecule and obtain two atoms in their ground state which are still
entangled and form a Bell-like state? We present a scheme that allows for the
preparation of such entangled atomic states from single oxygen molecules on
femtosecond time scales. The two neutral oxygen atoms are entangled in the
magnetic quantum number of their valence electrons. In a time-delayed probe
step, we employ non-adiabatic tunnel ionization, which is a magnetic quantum
number-sensitive mechanism. We then investigate correlations by comparing
single and double ionization probabilities of the Bell-like state. The
experimental results agree with the predictions for an entangled state.Comment: 20 pages, 7 figures, 1 tabl
Dimensional structure of bodily panic attack symptoms and their specific connections to panic cognitions, anxiety sensitivity and claustrophobic fears
Background. Previous studies of the dimensional structure of panic attack symptoms have mostly identified a respiratory and a vestibular/mixed somatic dimension. Evidence for additional dimensions such as a cardiac dimension and the allocation of several of the panic attack symptom criteria is less consistent. Clarifying the dimensional structure of the panic attack symptoms should help to specify the relationship of potential risk factors like anxiety sensitivity and fear of suffocation to the experience of panic attacks and the development of panic disorder.
Method. In an outpatient multicentre study 350 panic patients with agoraphobia rated the intensity of each of the ten DSM-IV bodily symptoms during a typical panic attack. The factor structure of these data was investigated with nonlinear confirmatory factor analysis (CFA). The identified bodily symptom dimensions were related to panic cognitions, anxiety sensitivity and fear of suffocation by means of nonlinear structural equation modelling (SEM).
Results. CFA indicated a respiratory, a vestibular/mixed somatic and a cardiac dimension of the bodily symptom criteria. These three factors were differentially associated with specific panic cognitions, different anxiety sensitivity facets and suffocation fear.
Conclusions. Taking into account the dimensional structure of panic attack symptoms may help to increase the specificity of the associations between the experience of panic attack symptoms and various panic related constructs
Light scattering by ultracold atoms in an optical lattice
We investigate theoretically light scattering of photons by ultracold atoms
in an optical lattice in the linear regime. A full quantum theory for the
atom-photon interactions is developed as a function of the atomic state in the
lattice along the Mott-insulator -- superfluid phase transition, and the
photonic scattering cross section is evaluated as a function of the energy and
of the direction of emission. The predictions of this theory are compared with
the theoretical results of a recent work on Bragg scattering in time-of-flight
measurements [A.M. Rey, {\it et al.}, Phys. Rev. A {\bf 72}, 023407 (2005)]. We
show that, when performing Bragg spectroscopy with light scattering, the photon
recoil gives rise to an additional atomic site to site hopping, which can
interfere with ordinary tunneling of matter waves and can significantly affect
the photonic scattering cross section.Comment: 13 pages, 6 fig, (accepted in PRA
Rural Rickets: Vitamin D Deficiency in a Post-Medieval Farming Community from the Netherlands
ABSTRACT Rickets is caused by vitamin D deficiency as a result of limited exposure to sunlight and inadequate diet. In the 19 th century, rickets was endemic in most northern European cities. In post-Medieval Netherlands, rickets is documented in low frequencies in a few urban samples, but has not been studied in contemporaneous rural populations. Beemster is a rural farming community in the Netherlands that was established in the 17 th century upon drained land, with the Middenbeemster cemetery in use until 1866 AD. Ninety-five individuals from the ages of 32 weeks in utero to 15 years were examined for rickets in order to understand factors that can cause vitamin D deficiency in rural, non-industrialized populations. To identify rickets in the Beemster sample, ten features were scored, with bending deformities of the lower limb and one other feature, or at least three non-bending features, having to be present in order for diagnosis. Nine individuals (9.5%) had evidence of rickets-a high prevalence, especially for a rural community where ample sunlight was available. The two and three year old Beemster infants were most heavily affected with an age-specific prevalence of 30.4%. Two three-month-old infants also had rickets. Some of the affected may have developed rickets secondarily, as a result of a different illness, but cultural practices including prolonged swaddling, occlusive clothing, and keeping the young indoors, are suggested to have contributed to this high rickets prevalence. Dietary variables including poor weaning foods and common episodes of malnutrition may have also contributed to vitamin D deficiency. This study demonstrates the value of careful analysis of pathological conditions in subadults and highlights that rickets was not only a disease of cities, but affected populations that would appear to have been at low risk, because of maladaptive cultural practices
Dimensional structure of bodily panic attack symptoms and their specific connections to panic cognitions, anxiety sensitivity and claustrophobic fears
This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Background.
Previous studies of the dimensional structure of panic attack symptoms have mostly identified a respiratory and a vestibular/mixed somatic dimension. Evidence for additional dimensions such as a cardiac dimension and the allocation of several of the panic attack symptom criteria is less consistent. Clarifying the dimensional structure of the panic attack symptoms should help to specify the relationship of potential risk factors like anxiety sensitivity and fear of suffocation to the experience of panic attacks and the development of panic disorder.
Method.
In an outpatient multicentre study 350 panic patients with agoraphobia rated the intensity of each of the ten DSM-IV bodily symptoms during a typical panic attack. The factor structure of these data was investigated with nonlinear confirmatory factor analysis (CFA). The identified bodily symptom dimensions were related to panic cognitions, anxiety sensitivity and fear of suffocation by means of nonlinear structural equation modelling (SEM).
Results.
CFA indicated a respiratory, a vestibular/mixed somatic and a cardiac dimension of the bodily symptom criteria. These three factors were differentially associated with specific panic cognitions, different anxiety sensitivity facets and suffocation fear.
Conclusions.
Taking into account the dimensional structure of panic attack symptoms may help to increase the specificity of the associations between the experience of panic attack symptoms and various panic related constructs.Peer Reviewe
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