1,721,032 research outputs found
Integrability of close encounters in the spatial restricted three-body problem
Full text linkWe extend to the spatial case a technique of integration of the close encounters formulated by Tullio Levi-Civita for the planar restricted three-body problem. We consider the Hamiltonian introduced in the Kustaanheimo-Stiefel regularization and construct a complete integral of the related Hamilton-Jacobi equation by means of a series convergent in a neighborhood of the collisions with the primary or secondary body
The risk of gastric dysplasia in medical long-term treatment of peptic ulcer disease.
No full textThere have been recent findings of gastric cancer in patients treated with cimetidine but too soon after treatment for that drug to have had a pathogenetic role. Ranitidine has been shown to induce slight changes in the gastric mucosa. In 117 patients with gastric ulcer followed-up in some cases for 24 months, five cases of cancer were detected, one after more than a year of follow-up. The numbers were too small to allow any conclusion to be drawn regarding relationships with medication. No significant differences in incidence of gastric epithelial dysplasia between control patients and patients treated with cimetidine or ranitidine were found. No dysplastic lesions were seen during a brief follow-up of 19 duodenal ulcer patients and a few gastric ulcer patients treated with pirenzepine but the data is too limited to allow conclusions to be drawn
Branching structures emerging from a continuous optimal transport model
Full text linkRecently a Dynamic-Monge-Kantorovich formulation of the PDE-based [Formula presented]-optimal transport problem was presented. The model considers a diffusion equation enforcing the balance of the transported masses with a time-varying conductivity that evolves proportionally to the transported flux. In this paper we present an extension of this model that considers a time derivative of the conductivity that grows as a power-law of the transport flux with exponent β>0. A sub-linear growth (01) favors flux intensity and promotes concentrated transport, leading to the emergence of steady-state “singular” and “fractal-like” configurations that resemble those of Branched Transport Problems. We derive a numerical discretization of the proposed model that is accurate, efficient, and robust for a wide range of scenarios. For β>1 the numerical model is able to reproduce highly irregular and fractal-like formations without any a-priory structural assumption
Control problems with differential constraints of higher order
Full text linkWe consider cost minimising control problems, in which the dynamical system is constrained by higher order differential equations of Euler–Lagrange type. Following ideas from a previous paper, we prove that a curve of controls uo(t) and a set of initial conditions σo give an optimal solution for a control problem of the considered type if and only if an appropriate double integral is greater than or equal to zero along any homotopy (u(t,s),σ(s)) of control curves and initial data starting from uo(t)=u(t,0) and σo=σ(0). This property is called Principle of Minimal Labour. From this principle we derive a generalisation of the classical Pontryagin Maximum Principle that holds under higher order differential constraints of Euler–Lagrange type and without the hypothesis of fixed initial data
A weak KAM approach to the periodic stationary Hartree equation
Full text linkWe present, through weak KAM theory, an investigation of the stationary Hartree equation in the periodic setting. More in details, we study the Mean Field asymptotics of quantum many body operators thanks to various integral identities providing the energy of the ground state and the minimum value of the Hartree functional. Finally, the ground state of the multiple-well case is studied in the semiclassical asymptotics thanks to the Agmon metric
Cauchy problems for stationary Hamilton-Jacobi equations under mild regularity assumptions
No full textHow do general practitioners rate their relationship with gastroenterologists?
No full textBackground. Relations between general practitioners and the hospital consultants are often considered difficult, and occasionally generate conflicts. potentially affecting the patient management and healthcare system organisation. These views, however, have partly been contradicted by structured surveys and qualitative Studies.
Aims. We conducted a survey on the general practitioners opinions regarding their relations with the gastroenterological-endoscopy services in order to explore current attitudes, any negative aspects and assess scope for improvement.
Subjects and methods. Structured questionnaires were sent to 22 1 general practitioners in the Veneto region of Italy; the questionnaire was based on 26 questions concerning their Subjective relations with the gastroenterologists, expertise in the gastroenterological problems and perceived efficiency of gastroenterological services.
Results. As many as 106 doctors answered the postal questionnaire (mean: 15 per province; range 5-20). Responses to the structured questions totalled to 2339 items. out of which 1234 (53%) presented positive responses, particularly with regard to admissions' management and the adequacy of referral reports. Many general practitioners reported of their participation in the meetings on gastroenterological problems. Homecare referrals were limited in number, even for the patients With tube feeding,
Conclusions. Relations between the general practitioners in Veneto and local gastroenterological services were generally good, possibly reflecting the well-developed Outreach network. This liaison could be further improved via closer interrelations based not only on the patient referrals but also on the professional and information exchange to promote successful practice
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