6,759 research outputs found
Semiflow selection and Markov selection theorems
The deterministic analog of the Markov property of a time-homogeneous Markov
process is the semigroup property of solutions of an autonomous differential
equation. The semigroup property arises naturally when the solutions of a
differential equation are unique, and leads to a semiflow. We prove an abstract
result on measurable selection of a semiflow for the situations without
uniqueness. We outline applications to ODEs, PDEs, differential inclusions,
etc. Our proof of the semiflow selection theorem is motivated by N. V. Krylov's
Markov selection theorem. To accentuate this connection, we include a new
version of the Markov selection theorem related to more recent papers of
Flandoli & Romito and Goldys et al.Comment: In this revised version we have added a new abstract result in Sec.
2. It is used to correct the Navier-Stokes example in application
Anharmonic Self-Energy of Phonons: Ab Initio Calculations and Neutron Spin Echo Measurements
We have calculated (ab initio) and measured (by spin-echo techniques) the
anharmonic self-energy of phonons at the X-point of the Brillouin zone for
isotopically pure germanium. The real part agrees with former, less accurate,
high temperature data obtained by inelastic neutron scattering on natural
germanium. For the imaginary part our results provide evidence that transverse
acoustic phonons at the X-point are very long lived at low temperatures, i.e.
their probability of decay approaches zero, as a consequence of an unusual
decay mechanism allowed by energy conservation.Comment: 8 pages, 2 figures, pdf fil
Predictive validity of the CriSTAL tool for short-term mortality in older people presenting at Emergency Departments: a prospective study
© 2018, The Author(s). Abstract: To determine the validity of the Australian clinical prediction tool Criteria for Screening and Triaging to Appropriate aLternative care (CRISTAL) based on objective clinical criteria to accurately identify risk of death within 3 months of admission among older patients. Methods: Prospective study of ≥ 65 year-olds presenting at emergency departments in five Australian (Aus) and four Danish (DK) hospitals. Logistic regression analysis was used to model factors for death prediction; Sensitivity, specificity, area under the ROC curve and calibration with bootstrapping techniques were used to describe predictive accuracy. Results: 2493 patients, with median age 78–80 years (DK–Aus). The deceased had significantly higher mean CriSTAL with Australian mean of 8.1 (95% CI 7.7–8.6 vs. 5.8 95% CI 5.6–5.9) and Danish mean 7.1 (95% CI 6.6–7.5 vs. 5.5 95% CI 5.4–5.6). The model with Fried Frailty score was optimal for the Australian cohort but prediction with the Clinical Frailty Scale (CFS) was also good (AUROC 0.825 and 0.81, respectively). Values for the Danish cohort were AUROC 0.764 with Fried and 0.794 using CFS. The most significant independent predictors of short-term death in both cohorts were advanced malignancy, frailty, male gender and advanced age. CriSTAL’s accuracy was only modest for in-hospital death prediction in either setting. Conclusions: The modified CriSTAL tool (with CFS instead of Fried’s frailty instrument) has good discriminant power to improve prognostic certainty of short-term mortality for ED physicians in both health systems. This shows promise in enhancing clinician’s confidence in initiating earlier end-of-life discussions
Isotope effects on the lattice parameter of cubic SiC
Path-integral molecular dynamics simulations in the isothermal-isobaric (NPT)
ensemble have been carried out to study the dependence of the lattice parameter
of 3C-SiC upon isotope mass. This computational method allows a quantitative
and nonperturbative study of such anharmonic effect. Atomic nuclei were treated
as quantum particles interacting via a tight-binding-type potential. At 300 K,
the difference Delta a between lattice parameters of 3C-SiC crystals with 12C
and 13C amounts to 2.1 x 10^{-4} A. The effect due to Si isotopes is smaller,
and amounts to 3.5 x 10^{-5} A when replacing 28Si by 29Si. Results of the PIMD
simulations are interpreted in terms of a quasiharmonic approximation for the
lattice vibrations.Comment: 4 pages, 3 figure
Health-related quality of life in patients with Gilles de la Tourette syndrome at the transition between adolescence and adulthood
Gilles de la Tourette syndrome (GTS) is a neurodevelopmental
condition characterised by tics and comorbid
behavioural problems, affecting predominantly
male patients. Tic severity typically fluctuates over time,
with a consistent pattern showing improvement after adolescence
in a considerable proportion of patients. Both tics
and behavioural co-morbidities have been shown to have
the potential to affect patients’ health-related quality of life
(HR-QoL) in children and adults with persisting symptoms.
In this study, we present the results of the first investigation
of HR-QoL in patients with Gilles de la Tourette syndrome
at the transition between adolescence and adulthood using
a disease-specific HR-QoL measure, the Gilles de la
Tourette Syndrome-Quality of Life-Children and Adolescents
scale. Our results showed that patients with GTS and
more severe co-morbid anxiety symptoms reported lower
HR-QoL across all domains, highlighting the impact of
anxiety on patient’s well-being at a critical stage of
development. Routine screening for anxiety symptoms is
recommended in all patients with GTS seen at transition
clinics from paediatric to adult care, to implement effective
behavioural and pharmacological interventions as
appropriate
Physical requirements for modeling stellar atmospheres according to the different spectral features observed
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