1,154 research outputs found
Rocking Subdiffusive Ratchets: Origin, Optimization and Efficiency
We study origin, parameter optimization, and thermodynamic efficiency of
isothermal rocking ratchets based on fractional subdiffusion within a
generalized non-Markovian Langevin equation approach. A corresponding
multi-dimensional Markovian embedding dynamics is realized using a set of
auxiliary Brownian particles elastically coupled to the central Brownian
particle (see video on the journal web site). We show that anomalous
subdiffusive transport emerges due to an interplay of nonlinear response and
viscoelastic effects for fractional Brownian motion in periodic potentials with
broken space-inversion symmetry and driven by a time-periodic field. The
anomalous transport becomes optimal for a subthreshold driving when the driving
period matches a characteristic time scale of interwell transitions. It can
also be optimized by varying temperature, amplitude of periodic potential and
driving strength. The useful work done against a load shows a parabolic
dependence on the load strength. It grows sublinearly with time and the
corresponding thermodynamic efficiency decays algebraically in time because the
energy supplied by the driving field scales with time linearly. However, it
compares well with the efficiency of normal diffusion rocking ratchets on an
appreciably long time scale
Three-body treatment of the penetration through the Coulomb field of a two-fragment nucleus
On the basis of the Faddeev integral equations method and the Watson-
Feshbach concept of the effective (optical) interaction potential, the first
fully consistent three-body approach to the description of the penetration of a
charged particle through the Coulomb field of a two-particle bound complex
(composed of one charged and one neutral particles) has been developed. A
general formalism has been elaborated and on its basis, to a first
approximation in the Sommerfeld parameter, the influence of the nuclear
structure on the probability of the penetration of a charged particle (the
muon, the pion, the kaon and the proton) through the Gamow barrier of a
two-fragment nucleus (the deuteron and the two lightest lambda hypernuclei,
lambda hypertriton and lambda hyperhelium-5, has been calculated and studied.Comment: LaTeX, 30 pages, 4 eps figure
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Assessing Software Vulnerabilities and Recovery Time Using Open Resources: Elements Of Technique And Results
Modern vulnerability resources are considered, their content security and recovery time of different software products are analyzed. To make the process smoother and more efficient three main stages are distinguished: source overview, general security and severity analysis, and more detailed vulnerability consideration including recovery time. The proposed approach is universal and can be used almost for any software projects and systems
Класифікація ЕКГ сигналів методами машинного навчання
The importance of electrocardiogram (ECG) analysis is difficult to overestimate. Rhythm of life, stress and other factors affect the frequency of diseases and their early appearance. At the same time, the technologization (digitalization) of life and hardware-software complexes, such as mobile electronic cardiographs and wearable devices in general, which are rapidly developing, open new opportunities for rapid analysis of human state by certain indicators, as well as allow to diagnose on the new higher level in almost real time.
There are many methods for analyzing cardiograms. In this paper, the authors propose a new approach based on an ensemble of individual classifiers, which effectively solves the problem of ECG analysis. The study is based on the PhysioNet Computing in Cardiology Challenge 2017 and the MIT-BIH Arrhythmia Database. The algorithm consists of the following stages: data filtering using moving average and Butterworth filters, R-peak localization via threshold and grouping method, ECG resampling for the better comparability, “Noisy” vs “NotNoisy” classification as the most hard-to-identify class, final classification as “Normal”, “Atrial Fibrillation”, “Other” using an ensemble of 1D CNN classifiers and a final classifier of selection using logistic regression, random forest or support vector machine (SVM).
The proposed method shows high accuracy by the metric F1, so it gives the background for further research, optimization and implementation. This way this algorithm could help to save human’s life by in-time detection of problems with cardiovascular system (CVS) at early stage.
Pages of the article in the issue: 70 - 77
Language of the article: UkrainianВажливість аналізу електрокардіограм (ЕКГ) важко переоцінити. Ритм життя, стреси та інші фактори впливають на частоту захворювань та їх ранні прояви. Разом з тим, технологізація (цифровізація) життя та апаратно-програмних комплекси, такі як мобільні електронні кардіографи та носимі пристрої загалом, що бурхливо розвиваються останнім часом, відкривають нові можливості для швидкого аналізу стану людини за певними показниками, а також дозволяють проводити діагностику на новому рівні практично у реальному часі.
Існує багато методів для аналізу кардіограм. В даній роботі авторами запропоновано новий підхід, що ефективно розв’язує задачу аналізу ЕКГ. Дослідження базується на наборі даних PhysioNetComputing in Cardiology Challenge 2017 та MIT-BIH Arrhythmia Database. Алгоритм складається зтаких етапів: фільтрація даних, локалізація R піків, передискретизація ЕКГ, визначення класу ЕКГ задопомогою ансамблю з 1D CNN та підсумкового класифікатора.
Запропонований метод показує високу точність за метрикою F1, тому являє собою цінність дляподальших досліджень, оптимізації та впровадження
Galactic Rotation Parameters from Data on Open Star Clusters
Currently available data on the field of velocities Vr, Vl, Vb for open star
clusters are used to perform a kinematic analysis of various samples that
differ by heliocentric distance, age, and membership in individual structures
(the Orion, Carina--Sagittarius, and Perseus arms). Based on 375 clusters
located within 5 kpc of the Sun with ages up to 1 Gyr, we have determined the
Galactic rotation parameters
Wo =-26.0+-0.3 km/s/kpc,
W'o = 4.18+-0.17 km/s/kpc^2,
W''o=-0.45+-0.06 km/s/kpc^3, the system contraction parameter K = -2.4+-0.1
km/s/kpc, and the parameters of the kinematic center Ro =7.4+-0.3 kpc and lo =
0+-1 degrees. The Galactocentric distance Ro in the model used has been found
to depend significantly on the sample age. Thus, for example, it is 9.5+-0.7
kpc and 5.6+-0.3 kpc for the samples of young (50 Myr)
clusters, respectively. Our study of the kinematics of young open star clusters
in various spiral arms has shown that the kinematic parameters are similar to
the parameters obtained from the entire sample for the Carina-Sagittarius and
Perseus arms and differ significantly from them for the Orion arm. The
contraction effect is shown to be typical of star clusters with various ages.
It is most pronounced for clusters with a mean age of 100 Myr, with the
contraction velocity being Kr = -4.3+-1.0 km/s.Comment: 14 pages, 4 figures, 2 table
Shape parameters of Galactic open clusters
(abridged) In this paper we derive observed and modelled shape parameters
(apparent ellipticity and orientation of the ellipse) of 650 Galactic open
clusters identified in the ASCC-2.5 catalogue. We provide the observed shape
parameters of Galactic open clusters, computed with the help of a
multi-component analysis. For the vast majority of clusters these parameters
are determined for the first time. High resolution ("star by star") N-body
simulations are carried out with the specially developed GRAPE code
providing models of clusters of different initial masses, Galactocentric
distances and rotation velocities. The comparison of models and observations of
about 150 clusters reveals ellipticities of observed clusters which are too low
(0.2 vs. 0.3), and offers the basis to find the main reason for this
discrepancy. The models predict that after Myr clusters reach an
oblate shape with an axes ratio of , and with the major axis
tilted by an angle of with respect to the
Galactocentric radius due to differential rotation of the Galaxy. Unbiased
estimates of cluster shape parameters require reliable membership determination
in large cluster areas up to 2-3 tidal radii where the density of cluster stars
is considerably lower than the background. Although dynamically bound stars
outside the tidal radius contribute insignificantly to the cluster mass, their
distribution is essential for a correct determination of cluster shape
parameters. In contrast, a restricted mass range of cluster stars does not play
such a dramatic role, though deep surveys allow to identify more cluster
members and, therefore, to increase the accuracy of the observed shape
parameters.Comment: 13 pages, 12 figures, accepted for publication in Astronomy and
Astrophysic
Long-range behavior of the optical potential for the elastic scattering of charged composite particles
The asymptotic behavior of the optical potential, describing elastic
scattering of a charged particle off a bound state of two charged, or
one charged and one neutral, particles at small momentum transfer
or equivalently at large intercluster distance
, is investigated within the framework of the exact three-body
theory. For the three-charged-particle Green function that occurs in the exact
expression for the optical potential, a recently derived expression, which is
appropriate for the asymptotic region under consideration, is used. We find
that for arbitrary values of the energy parameter the non-static part of the
optical potential behaves for as
. From this we derive for the
Fourier transform of its on-shell restriction for the behavior , i.e.,
dipole or quadrupole terms do not occur in the coordinate-space asymptotics.
This result corroborates the standard one, which is obtained by perturbative
methods. The general, energy-dependent expression for the dynamic
polarisability is derived; on the energy shell it reduces to the
conventional polarisability which is independent of the energy. We
emphasize that the present derivation is {\em non-perturbative}, i.e., it does
not make use of adiabatic or similar approximations, and is valid for energies
{\em below as well as above the three-body dissociation threshold}.Comment: 35 pages, no figures, revte
Синтез, реакційна здатність та антимікробна активність заміщених тієно[2,3-d]піримідин-4(3Н)-тіо(селено)нів
A new series of R1,R2-thieno[2,3-d]pyrimidine-4(3H)-one, thione and selenone derivatives have been synthesized; the reaction of alkylation of the compounds obtained has been studied. Their structures have been confirmed by the NMR 1H and mass spectra, and elemental analysis. The antibacterial and antifungal activities in vitro against three bacterial and two fungal pathogens have been revealed using the stiff plate agar diffusion method and the serial dilution method. The minimal bactericidal, fungicidal and bacteriostatic concentrations have been obtained. The pharmacological screening has shown that some of the compounds obtained possess a good antimicrobial activity. The culture of S.aureus. appeared to be the most sensitive to compound 10a. The best fungistatic indicators against A.niger have been found for compounds 4a and 9a.Синтезирован ряд новых производных R1,R2-тиено[2,3-d]пиримидин-4(3Н)-онов, тионов и селенонов, изучена реакция алкилирования полученных соединений. Структуры полученных соединений установлены с помощью данных ЯМР 1Н и масс-спектров, а также данных элементного анализа. Антибактериальная и фунгистатическая активность in vitro против трёх видов бактерий и двух видов грибов была обнаружена с помощью метода диффузии вещества в агар и метода серийного разведения. Определены минимальные концентрации бактериальной, фунгицидной и бактериостатической активности. Фармакологическое исследование подтвердило, что некоторые из полученных продуктов проявляют хорошую антимикробную активность. Культура бактерии S.aureus наиболее чувствительна к соединению 10а. Наилучшие фунгистатические показатели против цвелевого гриба A.niger определены для соедине-ний 4а и 9а.Синтезовано ряд нових похідних R1,R2-тієно[2,3-d]піримідин-4(3Н)-онів, тіонів і селенонів та вивчено реакцію алкілування отриманих продуктів. Структури отриманих продуктів встановлені за допомогою даних ЯМР 1Н та мас-спектрів і даних елементного аналізу. Антибактеріальну і фунгістатичну активність in vitro проти 3 культур бактерій і двох видів грибів було встановлено за допомогою методу дифузії речовини в агар і методу серійних розведень. Були визначені мінімальні концентрації бактеріальної, фунгістатичної і бактеріостатичної активності. Фармакологічне дослідження підтвердило, що деякі з отриманих продуктів проявляють добру антимікробну активність. Культура бактерії S.aureus. найбільш чутлива до сполуки 10а. Найкращі фунгістатичні показники проти цвільового гриба A.niger виявлені для сполук 4а і 9а
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