•Stochastic and deterministic models both describe motor-driven filament transport.•Comparing stochastic and deterministic forms assesses the impact of intrinsic noise.•Discrepancies between ...multi-stable deterministic and stochastic models emerge.•Intrinsic noise helps coordinate polarized transport of filament ensemble.•In biological systems, motor binding properties are a major regulatory mechanism.
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Noise affects all biological processes from molecules to cells, organisms and populations. Although the effect of noise on these processes is highly variable, evidence is accumulating which shows natural stochastic fluctuations (noise) can facilitate biological functions. Herein, we investigate the effect of noise on the transport of intermediate filaments in cells by comparing the stochastic and deterministic formalizations of the bidirectional transport of intermediate filaments, long elastic polymers transported along microtubules by antagonistic motor proteins (Dallon et al., 2019; Portet et al., 2019). By numerically exploring discrepancies in timescales and attractors between both formalizations, we characterize the impact of stochastic fluctuations on the individual and ensemble transport. Biologically, we find that noise promotes the collective movement of intermediate filaments and increases the efficiency of its regulation by the biochemical properties of motor-cargo interactions. While stochastic fluctuations reduce the impact of the initial distributions of motor proteins in cells, the number of binding sites and the affinity of motor-cargo interactions are the key parameters controlling transport efficiency and efficacy.
TUG-OF-WAR AND THE INFINITY LAPLACIAN PERES, YUVAL; SCHRAMM, ODED; SHEFFIELD, SCOTT ...
Journal of the American Mathematical Society,
01/2009, Letnik:
22, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We prove that every bounded Lipschitz function
F
F
on a subset
Y
Y
of a length space
X
X
admits a
tautest
extension to
X
X
, i.e., a unique Lipschitz extension
u
:
X
→
R
u:X \rightarrow \mathbb {R}
...for which
Lip
U
u
=
Lip
∂
U
u
\operatorname {Lip}_U u =\operatorname {Lip}_{\partial U} u
for all open
U
⊂
X
∖
Y
U \subset X\smallsetminus Y
. This was previously known only for bounded domains in
R
n
\mathbb {R}^n
, in which case
u
u
is
infinity harmonic
; that is, a viscosity solution to
Δ
∞
u
=
0
\Delta _\infty u = 0
, where
\
Δ
∞
u
=
|
∇
u
|
−
2
∑
i
,
j
u
x
i
u
x
i
x
j
u
x
j
.
\Delta _\infty u = |\nabla u|^{-2} \sum _{i,j} u_{x_i} u_{x_ix_j} u_{x_j}.
\
We also prove the first general uniqueness results for
Δ
∞
u
=
g
\Delta _{\infty } u = g
on bounded subsets of
R
n
\mathbb {R}^n
(when
g
g
is uniformly continuous and bounded away from
0
0
) and analogous results for bounded length spaces. The proofs rely on a new game-theoretic description of
u
u
. Let
u
ε
(
x
)
u^\varepsilon (x)
be the value of the following two-player zero-sum game, called
tug-of-war
: fix
x
0
=
x
∈
X
∖
Y
x_0=x\in X \smallsetminus Y
. At the
k
t
h
k^{\mathrm {th}}
turn, the players toss a coin and the winner chooses an
x
k
x_k
with
d
(
x
k
,
x
k
−
1
)
>
ε
d(x_k, x_{k-1})> \varepsilon
. The game ends when
x
k
∈
Y
x_k \in Y
, and player
I
’s payoff is
F
(
x
k
)
−
ε
2
2
∑
i
=
0
k
−
1
g
(
x
i
)
F(x_k) - \frac {\varepsilon ^2}{2}\sum _{i=0}^{k-1} g(x_i)
. We show that
‖
u
ε
−
u
‖
∞
→
0
\|u^\varepsilon - u\|_{\infty } \to 0
. Even for bounded domains in
R
n
\mathbb {R}^n
, the game theoretic description of infinity harmonic functions yields new intuition and estimates; for instance, we prove power law bounds for infinity harmonic functions in the unit disk with boundary values supported in a
δ
\delta
-neighborhood of a Cantor set on the unit circle.
Timed Up and Go (TUG) test is one of the most popular clinical tools aimed at the assessment of functional mobility and fall risk in older adults. The automation of the analysis of TUG movements is ...of great medical interest not only to speed up the test but also to maximize the information inferred from the subjects under study. In this context, this article describes a dataset collected from a cohort of 69 experimental subjects (including 30 adults over 60 years), during the execution of several repetitions of the TUG test. In particular, the dataset includes the measurements gathered with four wearables devices embedding four sensors (accelerometer, gyroscope magnetometer and barometer) located on four body locations (waist, wrist, ankle and chest). As a particularity, the dataset also includes the same measurements recorded when the young subjects repeat the test while wearing a commercial geriatric simulator, consisting of a set of weighted vests and other elements intended to replicate the limitations caused by aging. Thus, the generated dataset also enables the investigation into the potential of such tools to emulate the actual dynamics of older individuals.
The transverse upper gracilis (TUG) flap provides a good alternative to the gold standard DIEP in breast reconstruction. However, flap volume estimates are subjective, making preoperative planning ...potentially challenging.
To derive a reliable, accurate, and reproducible mathematical algorithm for the preoperative calculation of TUG flap volumes.
Nineteen consecutive patients with 30 TUG flaps were prospectively included. On the assumption that the TUG flap resembles two isosceles prisms, the formula of the volume of a prism was used to calculate their preoperative flap weights. These were then intraoperatively compared to the actual flap weights. A regression equation was calculated from the correlation analysis of 10 random flaps. This was then applied to the remaining 20 flaps to assess for improved reliability and weight prediction accuracy.
The prism volume equation used to clinically calculate flap volumes was: Geometric flap weight = (h1bT)/2+ (h2bT)/2, (h = height, b = base, T = flap thickness); all in centimetres. Geometric and actual flap weights were found to be significantly correlated (r2 = 0.977) generating the following regression formula: predicted TUG weight = 0.924 × geometric weight + 26.601. When this was applied to the remaining 20 flaps, no significant difference was found (p = 0.625) between predicted and actual flap weights, demonstrating an increased accuracy of predicting flap volume.
The proposed formula provides the clinician with a more accurate and reliable estimation of available TUG flap volume and may potentially aid with preoperative planning and patient consultations.
Particle motion at the microscale is an incessant tug-of-war between thermal fluctuations and applied forces on one side and the strong resistance exerted by fluid viscosity on the other. Friction is ...so strong that completely neglecting inertia--the overdamped approximation--gives an excellent effective description of the actual particle mechanics. In sharp contrast to this result, here we show that the overdamped approximation dramatically fails when thermodynamic quantities such as the entropy production in the environment are considered, in the presence of temperature gradients. In the limit of vanishingly small, yet finite, inertia, we find that the entropy production is dominated by a contribution that is anomalous, i.e., has no counterpart in the overdamped approximation. This phenomenon, which we call an entropic anomaly, is due to a symmetry breaking that occurs when moving to the small, finite inertia limit. Anomalous entropy production is traced back to futile phase-space cyclic trajectories displaying a fast downgradient sweep followed by a slow upgradient return to the original position.
In this paper, we study value functions of time-dependent tug-of-war games. We first prove the existence and uniqueness of value functions and verify that these game values satisfy a dynamic ...programming principle. Using the arguments in the proof of existence of game values, we can also deduce asymptotic behavior of game values when T→∞. Furthermore, we investigate boundary regularity for game values. Thereafter, based on the regularity results for value functions, we deduce that game values converge to viscosity solutions of the normalized parabolic p-Laplace equation.
Resumo Com o intuito de verificar a compreensão de gráficos cinemática de um grupo de estudantes de ensino médio, é recomendável utilizar um instrumento que possua tanto uma validade de conteúdo por ...parte de especialistas, quanto uma validação estatística. Nesse sentido, foi escolhida a nova versão do Test of Understanding Graphs in Kinematics (TUG-K), proposta em 2017 por Zavala e originalmente criado por Beichner, em 1994. O TUG-K foi elaborado para medir o conhecimento de gráficos em cinemática de alunos universitários, majoritariamente. Logo, para que possa ser usado na educação básica, é preciso saber se possui validade estatística nesse contexto. Portanto, foi realizada uma análise estatística do teste, após ser aplicado em dois momentos distintos, em estudantes de ensino médio de uma escola federal do Rio de Janeiro. Os parâmetros medidos foram os mesmos utilizados por Zavala. O principal resultado deste artigo foi demonstrar a validação do TUG-K nesse grupo. Como complemento, mostrou-se que o ganho de aprendizagem normalizado de Hake desses estudantes submetidos a aulas expositivas de cinemática foi de 17%, valor esperado para o ensino tradicional. A perspectiva subjacente é difundir e incentivar o uso do TUG-K no ensino médio.
Abstract In order to verify the kinematics graphs comprehension for a group of high school students, it is recommended to use an instrument that has a content valid by experts and a statistical validation. In this sense, was chosen the updated version of Test of Understanding Graphs in Kinematics (TUG-K), proposed in 2017 by Zavala and originally created by Beichner, in 1994. The TUG-K was elaborated to measure the understanding of graphs in kinematics of university students, mostly. Therefore, for this test to be used in basic education, it is necessary to know if it has statistical validity in this context. Consequently, a statistical analysis of the test was performed, after being applied at two different moments, with upper secondary level students of a federal school in Rio de Janeiro. The measured parameters were the same used by Zavala. The main result of this article was to demonstrate that TUG-K validity in this group. As a complement, it was shown that Hake's normalized learning gain from this group of students exposed to kinematics lectures was 17%, a value that is expected to be in traditional teaching. The underlying perspective is to disseminate and encourage the use of TUG-K in high school.
•Tug scheduling for hinterland transportation of barging cargos.•Mixed-integer programming model that captures realistic factors.•Tailor branch-and-price algorithm with accelerating techniques.
In a ...hinterland barge transport system, barges are usually not self-propelled and need to be towed or pushed by tugs. This study investigates a tug-scheduling problem at a seaport that is located at a river mouth and that connects the hinterland ports along the river with the global maritime transportation network. A mixed-integer programming model is proposed to optimize the assignment of barges to tugs as well as the time when the tugs depart from the seaport and go to the hinterland ports. Some properties of the model are also investigated. Moreover, an exact solution method based on a branch-and-price approach is developed to solve the proposed model. Numerical experiments are also conducted to validate the effectiveness of the proposed model and the efficiency of the proposed solution method.
Inertial measurement units (IMU) are used diagnostically in the movement analysis of Parkinson’s disease (PD) patients, allowing an objective way to assess biomechanical motion and gait parameters. ...The Timed Up and Go (TUG) is a standardized clinical gait test widely used in the monitoring of patient fall risk and disease progression. Gait tests performed at home have been applied as part of movement monitoring protocols, enabling a link to clinical supervised reference assessments. However, unsupervised gait tests in a real-world data context present challenges, mainly regarding the interaction between participants and the recording system. Therefore, we developed and evaluated a novel algorithmic pipeline called unsupervised TUG (uTUG). Our contribution is the automatic detection and decomposition of TUG tests into their subphases, performed at home with no clinician supervision. In contrast to related studies, we used only foot-mounted IMU with no additional markers or manual annotations, allowing the detection of TUG test frames for subsequent classification by machine learning Support Vector Machine (SVM), Random Forest (RF) and Naïve Bayes Classifier (NBC) algorithms. The evaluation comprised 96 daily recordings of real-world gait data and 81 clinical visits accumulating 300 real TUG test samples processed from 32 PD patients. A prefiltering sensitivity of 98.6%, followed by the precision of 90.6%, recall of 88.5%, and Fl-score of 89.6% for TUG test detection were achieved using RF for the automatic classification in continuous real-world gait data. Thus, uTUG simplifies the test for patients and avoids manual annotations for clinicians, automatically detecting TUG tests.
•Automatic detection of unsupervised Timed Up and Go tests in a real-world context.•Automatic decomposition of unsupervised Timed Up and Go tests into their subphases.•Inertial measurement units support the movement analysis of Parkinson’s disease patients.•Foot-mounted Inertial Measurement Units with no additional markers or annotations.•Abstraction of software interaction, helping the patient focus on the test execution.
•Men demonstrated superior TUG, gait speed, and 5TSTS test results across different age groups.•Age, sex, and height were significantly associated with poor physical performance.•We highly recommend ...the utilization of age-, sex-, and nationality-specific reference values for these tests.
To determine normative values and identify contributing factors for physical performance tests in older, Thai, community-dwelling adults.
Nationwide cross-sectional study.
Thai older community-dwelling adults.
Thai older community-dwelling adults aged ≥60 years who had no major health problems (N=1430) between March 2021 and August 2022.
Not applicable.
Normative values for the timed Up and Go (TUG) test, gait speed test, and 5-times sit-to-stand (5TSTS) test were determined for sex and age groups. Multivariable quantile regression analysis was employed to evaluate the participants, considering factors that may influence physical performance, such as height, and Charlson comorbidity index (CCI).
The study included 1430 eligible participants. Their mean age was 68.4±5.8 years, and 58.5% were women. Men demonstrated superior physical performance in the medians (p50) of the TUG (10.0 s vs 11.0 s), gait speed (0.98 m/s vs 0.91 m/s), and 5TSTS (14.0 s vs 16.1 s) tests compared with women. These differences were consistently observed across age groups. Moreover, age, sex, and height were significantly associated with poor physical performance.
This study observed variations in the normative values of TUG, gait speed, and 5TSTS tests among different age groups of older, Thai, community-dwelling adults. Additionally, our findings identified age, sex, and height as significant contributing factors to physical performance in this population.
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