183 research outputs found
Sensitivity of GPS and GLONASS orbits with respect to resonant geopotential parameters
The Center for Orbit Determination in Europe (CODE) has been involved in the processing of combined GPS/GLONASS data during the International GLONASS Experiment (IGEX). The resulting precise orbits were analyzed using the program SORBDT. Introducing one satellite's positions as pseudo-observations, the program is capable of fitting orbital arcs through these positions using an orbit improvement procedure based on the numerical integration of the satellite's orbit and its partial derivative with respect to the orbit parameters. For this study, the program was enhanced to estimate selected parameters of the Earth's gravity field. The orbital periods of the GPS satellites are âin contrast to those of the GLONASS satellites - 2:1 commensurable (P Sid:P GPS) with the rotation period of the Earth. Therefore, resonance effects of the satellite motion with terms of the geopotential occur and they influence the estimation of these parameters. A sensitivity study of the GPS and GLONASS orbits with respect to the geopotential coefficients reveals that the correlations between different geopotential coefficients and the correlations of geopotential coefficients with other orbit parameters, in particular with solar radiation pressure parameters, are the crucial issues in this context. The estimation of the resonant geopotential terms is, in the case of GPS, hindered by correlations with the simultaneously estimated radiation pressure parameters. In the GLONASS case, arc lengths of several days allow the decorrelation of the two parameter types. The formal errors of the estimates based on the GLONASS orbits are a factor of 5 to 10 smaller for all resonant term
Quark mean field model with density dependent couplings for finite nuclei
The quark mean field model, which describes the nucleon using the constituent
quark model, is applied to investigate the properties of finite nuclei. The
couplings of the scalar and vector mesons with quarks are made density
dependent through direct coupling to the scalar field so as to reproduce the
relativistic Brueckner-Hartree-Fock results of nuclear matter. The present
model provides satisfactory results on the properties of spherical nuclei, and
predicts an increasing size of the nucleon as well as a reduction of the
nucleon mass in the nuclear environmentComment: 8 pages, REVTeX, 8 ps figures, accepted for publication in Phys. Rev.
Neutron star properties with relativistic equations of state
We study the properties of neutron stars adopting relativistic equations of
state of neutron star matter, calculated in the framework of the relativistic
Brueckner-Hartree-Fock approximation for electrically charge neutral neutron
star matter in beta-equilibrium. For higher densities more baryons (hyperons
etc.) are included by means of the relativistic Hartree- or Hartree-Fock
approximation. The special features of the different approximations and
compositions are discussed in detail. Besides standard neutron star properties
special emphasis is put on the limiting periods of neutron stars, for which the
Kepler criterion and gravitation-reaction instabilities are considered.
Furthermore the cooling behaviour of neutron stars is investigated, too. For
comparison we give also the outcome for some nonrelativistic equations of
state.Comment: 43 pages, 22 ps-figures, to be published in the International Journal
of Modern Physics
Nuclei, Superheavy Nuclei and Hypermatter in a chiral SU(3)-Modell
A model based on chiral SU(3)-symmetry in nonlinear realisation is used for
the investigation of nuclei, superheavy nuclei, hypernuclei and multistrange
nuclear objects (so called MEMOs). The model works very well in the case of
nuclei and hypernuclei with one Lambda-particle and rules out MEMOs. Basic
observables which are known for nuclei and hypernuclei are reproduced
satisfactorily. The model predicts Z=120 and N=172, 184 and 198 as the next
shell closures in the region of superheavy nuclei. The calculations have been
performed in self-consistent relativistic mean field approximation assuming
spherical symmetry. The parameters were adapted to known nuclei.Comment: 19 pages, 11 figure
Stress deficits in reward behaviour are associated with and replicated by dysregulated amygdala-nucleus accumbens pathway function in mice
Reduced reward interest/learning and reward-to-effort valuation are distinct, common symptoms in neuropsychiatric disorders for which chronic stress is a major aetiological factor. Glutamate neurons in basal amygdala (BA) project to various regions including nucleus accumbens (NAc). The BA-NAc neural pathway is activated by reward and aversion, with many neurons being monovalent. In adult male mice, chronic social stress (CSS) leads to reduced discriminative reward learning (DRL) associated with decreased BA-NAc activity, and to reduced reward-to-effort valuation (REV) associated, in contrast, with increased BA-NAc activity. Chronic tetanus toxin BA-NAc inhibition replicates the CSS-DRL effect and causes a mild REV reduction, whilst chronic DREADDs BA-NAc activation replicates the CSS effect on REV without affecting DRL. This study provides evidence that stress disruption of reward processing involves the BA-NAc neural pathway; the bi-directional effects implicate opposite activity changes in reward (learning) neurons and aversion (effort) neurons in the BA-NAc pathway following chronic stress
Application of the density dependent hadron field theory to neutron star matter
The density dependent hadron field (DDRH) theory, previously applied to
isospin nuclei and hypernuclei is used to describe -stable matter and
neutron stars under consideration of the complete baryon octet. The
meson-hyperon vertices are derived from Dirac-Brueckner calculations of nuclear
matter and extended to hyperons. We examine properties of density dependent
interactions derived from the Bonn A and from the Groningen NN potential as
well as phenomenological interactions. The consistent treatment of the density
dependence introduces rearrangement terms in the expression for the baryon
chemical potential. This leads to a more complex condition for the
-equilibrium compared to standard relativistic mean field (RMF)
approaches. We find a strong dependence of the equation of state and the
particle distribution on the choice of the vertex density dependence. Results
for neutron star masses and radii are presented. We find a good agreement with
other models for the maximum mass. Radii are smaller compared to RMF models and
indicate a closer agreement with results of non-relativistic Brueckner
calculations.Comment: 28 pages, 11 figure
Deflating the deep brain stimulation causes personality changes bubble: the authors reply
To conclude that there is enough or not enough evidence demonstrating that deep brain stimulation (DBS) causes unintended postoperative personality changes is an epistemic problem that should be answered on the basis of established, replicable, and valid data. If prospective DBS recipients delay or refuse to be implanted because they are afraid of suffering from personality changes following DBS, and their fears are based on unsubstantiated claims made in the neuroethics literature, then researchers making these claims bear great responsibility for prospective recipients' medical decisions and subsequent well-being. Our article âDeflating the âDBS causes personalityâ bubbleâ reported an increase in theoretical neuroethics publications suggesting putative DBS-induced changes to personality, identity, agency, autonomy, authenticity and/or self (PIAAAS) and a critical lack of supporting primary empirical studies. This special issue of Neuroethics brings together responses to our initial publication, with our own counter-responses organized according to common themes. We provide a brief summary for each commentary and its main criticisms as well as a discussion of the way in which these responses can: 1) help clarify the meaning of PIAAAS, suggesting supplementary frameworks for understanding the impact of DBS on PIAAAS; 2) provide further empirical evidence of PIAAAS by presenting results from the researchersâ own work; and/or 3) offer a critique of our research approach and/or findings. Unintended postoperative putative changes to PIAAAS remain a critical ethical concern. It is beyond dispute that we need to develop reliable empirical and conceptual instruments able to measure complex cognitive, affective, and behavioural changes in order to investigate whether they are attributable to DBS alone
Ethnic inequalities and pathways to care in psychosis in England: a systematic review and meta-analysis
© The Author(s). 2018Background: As part of a national programme to tackle ethnic inequalities, we conducted a systematic review and meta-analysis of research on ethnic inequalities in pathways to care for adults with psychosis living in England and/or Wales. Methods: Nine databases were searched from inception to 03.07.17 for previous systematic reviews, including forward and backward citation tracking and a PROSPERO search to identify ongoing reviews. We then carried forward relevant primary studies from included reviews (with the latest meta-analyses reporting on research up to 2012), supplemented by a search on 18.10.17 in MEDLINE, Embase, PsycINFO and CINAHL for primary studies between 2012 and 2017 that had not been covered by previous meta-analyses. Results: Forty studies, all conducted in England, were included for our updated meta-analyses on pathways to care. Relative to the White reference group, elevated rates of civil detentions were found for Black Caribbean (OR = 3.43, 95% CI = 2.68 to 4.40, n = 18), Black African (OR = 3.11, 95% CI = 2.40 to 4.02, n = 6), and South Asian patients (OR = 1.50, 95% CI 1.07 to 2.12, n = 10). Analyses of each Mental Health Act section revealed significantly higher rates for Black people under (civil) Section 2 (OR = 1.53, 95% CI = 1.11 to 2.11, n = 3). Rates in repeat admissions were significantly higher than in first admission for South Asian patients (between-group difference p < 0.01). Some ethnic groups had more police contact (Black African OR = 3.60, 95% CI = 2.15 to 6.05, n = 2; Black Caribbean OR = 2.64, 95% CI = 1.88 to 3.72, n = 8) and criminal justice system involvement (Black Caribbean OR = 2.76, 95% CI = 2.02 to 3.78, n = 5; Black African OR = 1.92, 95% CI = 1.32 to 2.78, n = 3). The White Other patients also showed greater police and criminal justice system involvement than White British patients (OR = 1.49, 95% CI = 1.03 to 2.15, n = 4). General practitioner involvement was less likely for Black than the White reference group. No significant variations over time were found across all the main outcomes. Conclusions: Our updated meta-analyses reveal persisting but not significantly worsening patterns of ethnic inequalities in pathways to psychiatric care, particularly affecting Black groups. This provides a comprehensive evidence base from which to inform policy and practice amidst a prospective Mental Health Act reform. Trial registration: CRD42017071663Peer reviewedFinal Published versio
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