9,820 research outputs found
Root and Vigor Response of Big Bluestem to Summer Grazing Strategies
Warm-season grasses e.g., big bluestem (Andropogon gerardii Vitman) are great potential sources of summer forage in eastern Nebraska. Frequent, intensive defoliation can reduce root mass and limit root distribution. Quantifying root structure response to multiple defoliation events in a grazing situation is critical to develop management plans for these types of grasses. This experiment aimed to quantify the cumulative effects of timing and frequency of grazing on root structure and organic reserve estimates in big bluestem pastures
Preheating after N-flation
We study preheating in N-flation, assuming the Mar\v{c}enko-Pastur mass
distribution, equal energy initial conditions at the beginning of inflation and
equal axion-matter couplings, where matter is taken to be a single, massless
bosonic field. By numerical analysis we find that preheating via parametric
resonance is suppressed, indicating that the old theory of perturbative
preheating is applicable. While the tensor-to-scalar ratio, the non-Gaussianity
parameters and the scalar spectral index computed for N-flation are similar to
those in single field inflation (at least within an observationally viable
parameter region), our results suggest that the physics of preheating can
differ significantly from the single field case.Comment: 14 pages, 14 figures, references added, fixed typo
Perturbed Three Vortex Dynamics
It is well known that the dynamics of three point vortices moving in an ideal
fluid in the plane can be expressed in Hamiltonian form, where the resulting
equations of motion are completely integrable in the sense of Liouville and
Arnold. The focus of this investigation is on the persistence of regular
behavior (especially periodic motion) associated to completely integrable
systems for certain (admissible) kinds of Hamiltonian perturbations of the
three vortex system in a plane. After a brief survey of the dynamics of the
integrable planar three vortex system, it is shown that the admissible class of
perturbed systems is broad enough to include three vortices in a half-plane,
three coaxial slender vortex rings in three-space, and `restricted' four vortex
dynamics in a plane. Included are two basic categories of results for
admissible perturbations: (i) general theorems for the persistence of invariant
tori and periodic orbits using Kolmogorov-Arnold-Moser and Poincare-Birkhoff
type arguments; and (ii) more specific and quantitative conclusions of a
classical perturbation theory nature guaranteeing the existence of periodic
orbits of the perturbed system close to cycles of the unperturbed system, which
occur in abundance near centers. In addition, several numerical simulations are
provided to illustrate the validity of the theorems as well as indicating their
limitations as manifested by transitions to chaotic dynamics.Comment: 26 pages, 9 figures, submitted to the Journal of Mathematical Physic
Oxytocin and the stress buffering effect of social company: A genetic study in daily life
Social relationships are a crucial determinant of both mental and physical health. This effect is partly due to social buffering of stress. Animal studies suggest that social buffering is mediated via the oxytocin system, while studies in humans are sparse and limited by the low ecological validity of laboratory settings. In the present study, participants (N = 326) completed smartphone questionnaires four times a day over 4 to 5 days, measuring stressors, negative affect, and social context to assess social buffering. We found that under stress, participants reported a higher need for social company. Further, the impact of prior stressful events on momentary negative affect was attenuated by the perceived pleasantness of current social company. This social buffering effect was moderated by haplotypes of the oxytocin receptor gene, based on two well-described single nucleotide polymorphisms (rs2268498, rs53576). Effects were robust when controlling for gender and age, applying different data quality criteria, and even apparent in genotype-based analyses. Our findings demonstrate that social buffering and its modulation by oxytocin system characteristics have implications for life as lived outside the laboratory
A case report of metastasis of malignant mesothelioma to the oral gingiva
Introduction:
Metastatic mesothelioma to the oral cavity arises from the pleura or peritoneum and distant hematogenous metastases are seen in more than half of cases but only a few cases are reported to the oral cavity
Case:
A 75 year old male suffering from metastatic mesothelioma presents an hyperplasia of the attached gingiva. Malignant mesothelioma is a rare tumour arising from pleura, pericardium or peritoneum.
Conclusion:
This article highlights the importance of biopsy and histopathological diagnosis of oral lesions especially in case of a malignant history
Facilitation of Psychiatric Advance Directives by Peers and Clinicians on Assertive Community Treatment Teams
OBJECTIVE: Psychiatric advance directives (PADs) provide a legal mechanism for competent adults to document care preferences and authorize a surrogate to make treatment decisions. In a controlled research setting, an evidence-based intervention, the facilitated psychiatric advance directive (FPAD), was previously shown to overcome most barriers to PAD completion. This study examined implementation of the FPAD intervention in usual care settings as delivered by peer support specialists and nonpeer clinicians on assertive community treatment (ACT) teams.
METHODS: A total of 145 ACT consumers were randomly assigned, within teams, to FPAD with facilitation by either a peer (N=71) or a clinician (N=74). Completion rates and PAD quality were compared with the previous study's standard and across facilitator type. Logistic regression was used to estimate effects on the likelihood of PAD completion.
RESULTS: The completion rate of 50% in the intent-to-treat sample (N=145) was somewhat inferior to the prior standard (61%), but the rate of 58% for the retained sample (those who completed a follow-up interview, N=116) was not significantly different from the standard. Rates for peers and clinicians did not differ significantly from each other for either sample. PAD quality was similar to that achieved in the prior study. Four consumer variables predicted completion: independent living status, problematic substance use, length of time served by the ACT team, and no perceived unmet need for hospitalization in crisis.
CONCLUSIONS: Peers and clinicians can play a crucial role in increasing the number of consumers with PADs, an important step toward improving implementation of PADs in mental health care
Controlling Effect of Geometrically Defined Local Structural Changes on Chaotic Hamiltonian Systems
An effective characterization of chaotic conservative Hamiltonian systems in
terms of the curvature associated with a Riemannian metric tensor derived from
the structure of the Hamiltonian has been extended to a wide class of potential
models of standard form through definition of a conformal metric. The geodesic
equations reproduce the Hamilton equations of the original potential model
through an inverse map in the tangent space. The second covariant derivative of
the geodesic deviation in this space generates a dynamical curvature, resulting
in (energy dependent) criteria for unstable behavior different from the usual
Lyapunov criteria. We show here that this criterion can be constructively used
to modify locally the potential of a chaotic Hamiltonian model in such a way
that stable motion is achieved. Since our criterion for instability is local in
coordinate space, these results provide a new and minimal method for achieving
control of a chaotic system
Hirota equation as an example of integrable symplectic map
The hamiltonian formalism is developed for the sine-Gordon model on the
space-time light-like lattice, first introduced by Hirota. The evolution
operator is explicitely constructed in the quantum variant of the model, the
integrability of the corresponding classical finite-dimensional system is
established.Comment: 10 pages, LaTe
"Medikamente sind Bomben" - zum Metapherngebrauch von Lungentransplantations-Patienten mit guter oder ungenĂĽgender Compliance
Fragestellung: Nach einer Organtransplantation finden komplexe psychologische Verarbeitungsprozesse statt. In der vorliegenden Studie wurde untersucht, welche Metaphern im Zusammenhang mit Transplantationserfahrungen verwendet werden, und ob Unterschiede zwischen Patienten mit guter bzw. ungenĂĽgender Compliance im Gebrauch dieser Metaphern bestehen.
Methode: 14 lungentransplantierte Patienten wurden in einem halbstrukturierten Interview zu ihren Transplantationserfahrungen befragt. Ihre Compliance wurde von den behandelnden Ärzten eingeschätzt. Die Auswertung der Interviews erfolgte anhand einer Metaphernanalyse, welche Hinweise auf vor- und unbewusste Vorstellungen der Patienten liefert. Die Interraterreliabilität über die Metapherngruppen war Cohen’s Kappa K = 0.8.
Ergebnisse: Die Patienten konzeptualisierten ihren Körper, aber auch ihr Selbst als ein “Gefäß”, dass sowohl materielle (z.B. die Lunge) wie immaterielle Objekte (z.B. Gedanken an den Spender, Affekte) enthält. Der wichtigste Unterschied zwischen den Compliance-Gruppen bestand darin, dass Patienten mit ungenügender Compliance eine grössere Distanz zur transplantierten Lunge erlebten. Auch konzeptualisierten sie ihren Körper bzw. ihr Selbst nicht als ein Gefäß, das die Lunge enthält.
Diskussion: Die Ergebnisse zeigen, dass gute Compliance mit einer erfolgreichen Organintegration assoziiert ist, welche die Zugehörigkeit der Lunge in einem als Gefäß konzeptualisierten Körper bzw. Selbst umfasst. Patienten mit ungenügender Compliance nehmen die Lunge eher als Fremdkörper wahr. Diese Verarbeitungsprozesse sind teils bewusster, teils vor- und unbewusster Natur
- …