241 research outputs found
Transfering Targeted Maximum Likelihood Estimation for Causal Inference into Sports Science
Although causal inference has shown great value in estimating effect sizes in, for instance, physics, medical studies, and economics, it is rarely used in sports science. Targeted Maximum Likelihood Estimation (TMLE) is a modern method for performing causal inference. TMLE is forgiving in the misspecification of the causal model and improves the estimation of effect sizes using machine-learning methods. We demonstrate the advantage of TMLE in sports science by comparing the calculated effect size with a Generalized Linear Model (GLM). In this study, we introduce TMLE and provide a roadmap for making causal inference and apply the roadmap along with the methods mentioned above in a simulation study and case study investigating the influence of substitutions on the physical performance of the entire soccer team (i.e., the effect size of substitutions on the total physical performance). We construct a causal model, a misspecified causal model, a simulation dataset, and an observed tracking dataset of individual players from 302 elite soccer matches. The simulation dataset results show that TMLE outperforms GLM in estimating the effect size of the substitutions on the total physical performance. Furthermore, TMLE is most robust against model misspecification in both the simulation and the tracking dataset. However, independent of the method used in the tracking dataset, it was found that substitutes increase the physical performance of the entire soccer team
Modelling and experiments of self-reflectivity under femtosecond ablation conditions
We present a numerical model which describes the propagation of a single
femtosecond laser pulse in a medium of which the optical properties dynamically
change within the duration of the pulse. We use a Finite Difference Time Domain
(FDTD) method to solve the Maxwell's equations coupled to equations describing
the changes in the material properties. We use the model to simulate the
self-reflectivity of strongly focused femtosecond laser pulses on silicon and
gold under laser ablation condition. We compare the simulations to experimental
results and find excellent agreement.Comment: 11 pages, 8 figure
Coherent vibrations of submicron spherical gold shells in a photonic crystal
Coherent acoustic radial oscillations of thin spherical gold shells of
submicron diameter excited by an ultrashort optical pulse are observed in the
form of pronounced modulations of the transient reflectivity on a subnanosecond
time scale. Strong acousto-optical coupling in a photonic crystal enhances the
modulation of the transient reflectivity up to 4%. The frequency of these
oscillations is demonstrated to be in good agreement with Lamb theory of free
gold shells.Comment: Error in Eqs.2 and 3 corrected; Tabl. I corrected; Fig.1 revised; a
model that explains the dependence of the oscillation amplitude of the
transient reflectivity with wavelength adde
Pulmonary arterial wall distensibility assessed by intravascular ultrasound in children with congenital heart disease: an indicator for pulmonary vascular disease?
BACKGROUND: Both pulmonary hypertension and pulmonary overflow are
associated with functional and structural changes of the pulmonary
arterial wall. Current techniques to evaluate the pulmonary vasculature
neglect the pulsatile nature of pulmonary flow. STUDY OBJECTIVES: To
determine whether the dynamic properties of the pulmonary arterial wall
are altered in patients with abnormal pulmonary hemodynamics due to
congenital heart defects, and whether these changes are associated with
the progression of pulmonary vascular disease (PVD). PATIENTS AND METHODS:
In 43 children with PVD due to congenital heart defects and 12 control
subjects, pulmonary arterial pulsatility (the relative increase in vessel
area during the cardiac cycle) and distensibility (the inverse of the
stress/strain elastic modulus) were determined with intravascular
ultrasound. Results were correlated with clinical and hemodynamic
parameters. RESULTS: Pulsatility correlated with pulmonary pulse pressure
(p < 0.001), pulmonary-to-systemic vascular resistance ratio (PVR/SVR) [p
= 0.001], and hemoglobin concentration (p = 0.01). However, when corrected
for these variables, pulsatility did not differ between patients and
control subjects. In contrast, arterial wall distensibility decreased with
the severity of PVD and correlated independently with
pulmonary-to-systemic arterial pressure ratio (p < 0.001) and PVR/SVR (p =
0.03), and with hemoglobin concentration (p < 0.01). Adjusted for
hemodynamic variables, distensibility was still decreased in patients with
PVD compared to control subjects. CONCLUSIONS: These results demonstrate
that pulmonary arterial wall distensibility is progressively decreased in
PVD; moreover, this decreased distensibility is, in part, related to
increased distending pressure as a result of pulmonary hypertension but
also, in part, to stiffening of the arterial wall during the disease
process. Arterial wall distensibility may be of additional value in the
evaluation of pulmonary vasculature and ventricular workload
Розвиток історико-краєзнавчої бібліографії в Криму (20–30-ті роки ХХ століття)
Викладені передумови розвитку краєзнавчої бібліографії в Кримській АРСР, виділені її відмінні риси. Схарактеризована діяльність видатного історика, ученого-краєзнавця А. І. Маркевича. Висвітлений внесок у розвиток історико-краєзнавчої бібліографії Криму бібліографів В. В. Симоновського, Д. М. Єгорова, Д. С. Спиридонова, Ф. П. Максименка та ін.Изложены предпосылки развития краеведческой библиографии в Крымской АССР, выделены ее отличительные черты. Рассмотрена деятельность выдающегося историка, ученого-краеведа А. И. Маркевича. Дан анализ его фундаментального труда “TAURICA”, который является одним из ключевых историко-краеведческих пособий, созданных в период существования Крымской АССР.The prerequisites of the development of regional bibliography in the Crimean ASSR are presented, its distinguishing features are allocated. The activity of the outstanding historian, scientist- student of local lore A. I. Markevich is examined. There is the analysis of its fundamental work “TAURICA”, which is one of the key historic- regional textbook, created in the time of Crimean ASSR. There is the characteristic of indicators by V. V. Simonovskiy — “bibliography of krymovedeniya”. The contribution to development of the historic- regional bibliography of Crimea the bibliographers D. N. Yegorov, D. S. Spiridonov, F. F. Maksimenko and others is illuminated
Investigating the current knowledge and needs concerning a follow-up for long-term cardiovascular risks in Dutch women with a preeclampsia history:a qualitative study
Background There is increasing evidence that a history of preeclampsia is an important risk factor for future cardiovascular events. Awareness of this risk could provide opportunities for identification of women at risk, with opportunities for prevention and / or early intervention. A standardized follow-up has not yet been implemented in the north of the Netherlands. The objective of this qualitative study was to explore the opinions and wishes among women and physicians about the follow-up for women with a history of preeclampsia. Methods Semi-structured interviews with 15 women and 14 physicians (5 obstetricians, 4 general practitioners, 3 vascular medicine specialists and 2 cardiologists) were performed and addressed topics about knowledge on CVR, current - and future follow-up. Women were approached through the HELLP foundation and their physicians. Physicians were approached by email. The interviews were recorded, typed and coded using ATLAS.ti software. A theoretical-driven thematic analysis was performed. Results Women had some knowledge about the association between preeclampsia and the increased CVR, but missed information from their health care providers. Specialists were aware of the association, but the information and advice they provided to their patients was minimal and inconsistent according to themselves. Whereas some general practitioners regarded their own knowledge as limited. There was a clear desire among women for a more extensive follow-up with specific attention to both emotional and physical consequences of preeclampsia. Physicians indicated that they preferred to see a follow up program concerning the CVR at the general practitioner as part of the already existent cardiovascular risk management (CVRM) program. Conclusion Women and medical specialists consider it important to improve aftercare for women after a pregnancy complicated by preeclampsia. Introducing these women into the CVRM program at the general practitioner is regarded as a preferred first step. Further research is warranted to establish an evidence-based guideline for the follow-up of these women
Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon
We present a microscopic theory of the low-frequency voltage noise (known as
"1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This
theory traces the noise back to the long-range fluctuations of the Coulomb
potential produced by deep defects, thereby predicting the absolute noise
intensity as a function of the distribution of defect activation energies. The
predictions of this theory are in very good agreement with our own experiments
in terms of both the absolute intensity and the temperature dependence of the
noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added,
but no conceptual revision
Correlated terahertz acoustic and electromagnetic emission in dynamically screened InGaN/GaN quantum wells
We investigate acoustic and electromagnetic emission from optically excited strained piezoelectric In0.2Ga0.8N/GaN multiple quantum wells (MQWs), using optical pump-probe spectroscopy, time-resolved Brillouin scattering, and THz emission spectroscopy. A direct comparison of detected acoustic signals and THz electromagnetic radiation signals demonstrates that transient strain generation in InGaN/GaN MQWs is correlated with electromagnetic THz generation, and both types of emission find their origin in ultrafast dynamical screening of the built-in piezoelectric field in the MQWs. The measured spectral intensity of the detected Brillouin signal corresponds to a maximum strain amplitude of generated acoustic pulses of 2%. This value coincides with the static lattice-mismatch-induced strain in In0.2Ga0.8N/GaN, demonstrating the total release of static strain in MQWs via impulsive THz acoustic emission. This confirms the ultrafast dynamical screening mechanism in MQWs as a highly efficient method for impulsive strain generatio
Ioffe Physical-Technical Institute
Abstract We present results of pump-probe anti-Stokes Raman experiments at 1.8 K on the generation of nonequilibrium phonons in a-Si:H following intense optical excitation. We obtained a decay time of &70 ns for the TO phonons in all samples studied. In plasma deposited samples we observed an additional slowly decaying ( <100 ns) contribution to the Raman signal, which was not seen in hot-wire deposited samples. We propose a model to explain the additional phonons as resulting from fast nonradiative recombination of free carriers with carriers localized in the tail states
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