445 research outputs found
Growing condensate in two-dimensional turbulence
We report a numerical study, supplemented by phenomenological explanations,
of ``energy condensation'' in forced 2D turbulence in a biperiodic box.
Condensation is a finite size effect which occurs after the standard inverse
cascade reaches the size of the system. It leads to emergence of a coherent
vortex dipole. We show that the time growth of the dipole is self-similar, and
it contains most of the injected energy, thus resulting in an energy spectrum
which is markedly steeper than the standard one. Once the coherent
component is subtracted, however, the remaining fluctuations have a spectrum
close to . The fluctuations decay slowly as the coherent part grows.Comment: 4 pages, 4 figures. This version includes some additional
phenomenological explanations of the results, additional references and
improved figure
Risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review of the literature
Objectives: To estimate the risk of miscarriage after amniocentesis or chorionic villus sampling (CVS) based on a systematic review of the literature.
Methods: A search of MEDLINE, EMBASE, and The Cochrane Library (2000-2017) was carried out to identify studies reporting complications following CVS or amniocentesis. The inclusion criteria for the systematic review were studies reporting results from large controlled studies (n1,000 invasive procedures) and those reporting data for pregnancy loss prior to 24 weeksâ gestation. Data for cases that had invasive procedure and controls were inputted in contingency tables and risk of miscarriage was estimated for each study. Summary statistics were calculated after taking into account the weighting for each study included in the systematic review. Procedure-related risk of miscarriage was estimated as a weighted risk difference from the summary statistics for cases and controls.
Results: The electronic search from the databases yielded 2,465 potential citations of which 2,431 were excluded, leaving 34 studies for full-text review. The final review included 10 studies for amniocentesis and 6 studies for CVS, which were used to estimate risk of miscarriage in pregnancies that had an invasive procedure and the control pregnancies that did not. The procedure-related risk of miscarriage following amniocentesis was 0.35% (95% confidence interval [CI]: 0.07 to 0.63) and that following CVS was 0.35% (95%C CI: -0.31 to 1.00).
Conclusion: The procedure-related risks of miscarriage following amniocentesis and CVS are lower than currently quoted to women
Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers
Control of spatiotemporal chaos is achieved in the catalytic oxidation of CO on Pt(110) by localized modification of the kinetic properties of the surface chemical reaction. In the experiment, a small temperature heterogeneity is created on the surface by a focused laser beam. This heterogeneity constitutes a pacemaker and starts to emit target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos that is present in the absence of control. We compare this experimental result with a numerical study of the KrischerâEiswirthâErtl model for CO oxidation on Pt(110). We confirm the experimental findings and identify regimes where complete and partial controls are possible
Controlling spatiotemporal chaos in oscillatory reaction-diffusion systems by time-delay autosynchronization
Diffusion-induced turbulence in spatially extended oscillatory media near a
supercritical Hopf bifurcation can be controlled by applying global time-delay
autosynchronization. We consider the complex Ginzburg-Landau equation in the
Benjamin-Feir unstable regime and analytically investigate the stability of
uniform oscillations depending on the feedback parameters. We show that a
noninvasive stabilization of uniform oscillations is not possible in this type
of systems. The synchronization diagram in the plane spanned by the feedback
parameters is derived. Numerical simulations confirm the analytical results and
give additional information on the spatiotemporal dynamics of the system close
to complete synchronization.Comment: 19 pages, 10 figures submitted to Physica
Pusat Fasilitas Wisata Tamblingan Di Desa Wisata Munduk (Pendekatan Arsitektur Neo-Vernakular)
Desa Wisata Munduk memiliki Danau Tamblingan sebagai destinasi wisata utama dengan pengembangan ke arah wisata alam dan spiritual. Sebagai dukungan akomodasi perlu adanya sebuah pusat fasilitas yang berbasis pada masyarakat, budaya dan lingkungan sesuai dengan kriteria desa wisata. Pencapaian kriteria tersebut ditunjukkan dengan perancangan yang berkarakter lokal, ramah lingkungan dan menyesuaikan kondisi saat ini. Hal ini dapat diproses dengan pendekatan arsitektur neo-vernakular yang mengkinikan arsitektur vernakular setempat dengan transformasi berdasarkan makna dan fungsi. Metode kajian diarahkan pada metode deskriptif kualitatif yang disusun secara programatik dengan penekanan ideologi dari arsitektur neo-vernakular. Fungsi yang diwadahi dalam Pusat Fasilitas Wisata Tamblingan terbagi dalam fungsi wisata (informasi, edukasi dan rekreasi) dan fungsi kemasyarakatan (sarana pembinaan dan organisasi masyarakat). Karakter arsitektur neo-vernakular pada skala tapak ditunjukkan dengan aplikasi pola zonasi berdasarkan hirarki, pola lansekap mengadaptasi konsep natah, konsep sirkulasi kombinasi Arsitektur Bali yang dimodifikasi dan sistem utilitas ramah lingkungan. Pada skala bangunan, bentuk aplikasinya adalah tipe bangunan tropis, material alami dan sistem struktur ekspos yang dikembangkan sesuai fungsi, tatanan masa majemuk serta adaptasi karakter tipologi bentuk dan tampilan bangunan setempat
Universal features of cell polarization processes
Cell polarization plays a central role in the development of complex
organisms. It has been recently shown that cell polarization may follow from
the proximity to a phase separation instability in a bistable network of
chemical reactions. An example which has been thoroughly studied is the
formation of signaling domains during eukaryotic chemotaxis. In this case, the
process of domain growth may be described by the use of a constrained
time-dependent Landau-Ginzburg equation, admitting scale-invariant solutions
{\textit{\`a la}} Lifshitz and Slyozov. The constraint results here from a
mechanism of fast cycling of molecules between a cytosolic, inactive state and
a membrane-bound, active state, which dynamically tunes the chemical potential
for membrane binding to a value corresponding to the coexistence of different
phases on the cell membrane. We provide here a universal description of this
process both in the presence and absence of a gradient in the external
activation field. Universal power laws are derived for the time needed for the
cell to polarize in a chemotactic gradient, and for the value of the smallest
detectable gradient. We also describe a concrete realization of our scheme
based on the analysis of available biochemical and biophysical data.Comment: Submitted to Journal of Statistical Mechanics -Theory and Experiment
Modeling cell crawling strategies with a bistable model: From amoeboid to fan-shaped cell motion
Eukaryotic cell motility involves a complex network of interactions between
biochemical components and mechanical processes. The cell employs this network
to polarize and induce shape changes that give rise to membrane protrusions and
retractions, ultimately leading to locomotion of the entire cell body. The
combination of a nonlinear reaction-diffusion model of cell polarization, noisy
bistable kinetics, and a dynamic phase field for the cell shape permits us to
capture the key features of this complex system to investigate several motility
scenarios, including amoeboid and fan-shaped forms as well as intermediate
states with distinct displacement mechanisms. We compare the numerical
simulations of our model to live cell imaging experiments of motile {\it
Dictyostelium discoideum} cells under different developmental conditions. The
dominant parameters of the mathematical model that determine the different
motility regimes are identified and discussed
Analysis of protrusion dynamics in amoeboid cell motility by means of regularized contour flows
Amoeboid cell motility is essential for a wide range of biological processes including wound healing, embryonic morphogenesis, and cancer metastasis. It relies on complex dynamical patterns of cell shape changes that pose long-standing challenges to mathematical modeling and raise a need for automated and reproducible approaches to extract quantitative morphological features from image sequences. Here, we introduce a theoretical framework and a computational method for obtaining smooth representations of the spatiotemporal contour dynamics from stacks of segmented microscopy images. Based on a Gaussian process regression we propose a one-parameter family of regularized contour flows that allows us to continuously track reference points (virtual markers) between successive cell contours. We use this approach to define a coordinate system on the moving cell boundary and to represent different local geometric quantities in this frame of reference. In particular, we introduce the local marker dispersion as a measure to identify localized membrane expansions and provide a fully automated way to extract the properties of such expansions, including their area and growth time. The methods are available as an open-source software package called AmoePy, a Python-based toolbox for analyzing amoeboid cell motility (based on time-lapse microscopy data), including a graphical user interface and detailed documentation. Due to the mathematical rigor of our framework, we envision it to be of use for the development of novel cell motility models. We mainly use experimental data of the social amoeba Dictyostelium discoideum to illustrate and validate our approach
High frequency periodic forcing of the oscillatory catalytic CO oxidation on Pt(110)
Resonant periodic forcing is applied to catalytic CO oxidation on platinum (110) in the oscillatory regime. The external parameters are chosen such that the unperturbed system spontaneously develops chemical turbulence. By periodically modulating the CO partial pressure, changes in the spatiotemporal behaviour of the system can be induced: the turbulent behaviour is suppressed and frequency locked patterns with sub-harmonic entrainment develop. A novel gas-driving compressor has been implemented to perform the experimental work
Spontaneous transitions between amoeboid and keratocyte-like modes of migration
The motility of adherent eukaryotic cells is driven by the dynamics of the
actin cytoskeleton. Despite the common force-generating actin machinery,
different cell types often show diverse modes of locomotion that differ in
their shape dynamics, speed, and persistence of motion. Recently, experiments
in Dictyostelium discoideum have revealed that different motility modes can be
induced in this model organism, depending on genetic modifications,
developmental conditions, and synthetic changes of intracellular signaling.
Here, we report experimental evidence that in a mutated D. discoideum cell line
with increased Ras activity, switches between two distinct migratory modes, the
amoeboid and fan-shaped type of locomotion, can even spontaneously occur within
the same cell. We observed and characterized repeated and reversible switchings
between the two modes of locomotion, suggesting that they are distinct
behavioral traits that coexist within the same cell. We adapted an established
phenomenological motility model that combines a reaction-diffusion system for
the intracellular dynamics with a dynamic phase field to account for our
experimental findings.Comment: Some references pointing at figures in the supplement and therefore
are not correctly displayed. The supplement is available at zenodo.or
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