6,086 research outputs found
Encapsulation process sterilizes and preserves surgical instruments
Ethylene oxide is blended with an organic polymer to form a sterile material for encapsulating surgical instruments. The material does not bond to metal and can be easily removed when the instruments are needed
Process for preparing sterile solid propellants Patent
Using ethylene oxide in preparation of sterilized solid rocket propellants and encapsulating material
A framework for quantification and physical modeling of cell mixing applied to oscillator synchronization in vertebrate somitogenesis
In development and disease, cells move as they exchange signals. One example is found in vertebrate development, during which the timing of segment formation is set by a ‘segmentation clock’, in which oscillating gene expression is synchronized across a population of cells by Delta-Notch signaling. Delta-Notch signaling requires local cell-cell contact, but in the zebrafish embryonic tailbud, oscillating cells move rapidly, exchanging neighbors. Previous theoretical studies proposed that this relative movement or cell mixing might alter signaling and thereby enhance synchronization. However, it remains unclear whether the mixing timescale in the tissue is in the right range for this effect, because a framework to reliably measure the mixing timescale and compare it with signaling timescale is lacking. Here, we develop such a framework using a quantitative description of cell mixing without the need for an external reference frame and constructing a physical model of cell movement based on the data. Numerical simulations show that mixing with experimentally observed statistics enhances synchronization of coupled phase oscillators, suggesting that mixing in the tailbud is fast enough to affect the coherence of rhythmic gene expression. Our approach will find general application in analyzing the relative movements of communicating cells during development and disease.Fil: Uriu, Koichiro. Kanazawa University; JapónFil: Bhavna, Rajasekaran. Max Planck Institute of Molecular Cell Biology and Genetics; Alemania. Max Planck Institute for the Physics of Complex Systems; AlemaniaFil: Oates, Andrew C.. Francis Crick Institute; Reino Unido. University College London; Reino UnidoFil: Morelli, Luis Guillermo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación en Biomedicina de Buenos Aires - Instituto Partner de la Sociedad Max Planck; Argentina. Max Planck Institute for Molecular Physiology; Alemania. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de FÃsica; Argentin
Pillars and Buttes: A Petrologic Comparison of Modern and Ancient Hydrocarbon Seep Rock
Purpose: Literature on the formation of authigenic rock at cold seeps focuses on the role of microbes in creating geochemically favorable environment for the precipitation of carbonate and barite minerals. Less understood is the pathway that lithified microbial patches of seafloor sediment follow to become rock formations that are identified in strata dating back to the Silurian. In this study I will compare Holocene seep rock from the Gulf of Mexico to Cretaceous carbonates that have been identified as seep rock. Through the study of rock in its early stages of formation to rock that has likely undergone multiple phases of diagenesis I aim to establish a hypothetical sequence of formation of the Cretaceous seep rocks
Nonlinearity arising from noncooperative transcription factor binding enhances negative feedback and promotes genetic oscillations
We study the effects of multiple binding sites in the promoter of a genetic
oscillator. We evaluate the regulatory function of a promoter with multiple
binding sites in the absence of cooperative binding, and consider different
hypotheses for how the number of bound repressors affects transcription rate.
Effective Hill exponents of the resulting regulatory functions reveal an
increase in the nonlinearity of the feedback with the number of binding sites.
We identify optimal configurations that maximize the nonlinearity of the
feedback. We use a generic model of a biochemical oscillator to show that this
increased nonlinearity is reflected in enhanced oscillations, with larger
amplitudes over wider oscillatory ranges. Although the study is motivated by
genetic oscillations in the zebrafish segmentation clock, our findings may
reveal a general principle for gene regulation.Comment: 11 pages, 8 figure
Pillars and Buttes: A Petrologic Comparison of Modern and Ancient Hydrocarbon Seep Rock
Purpose: Literature on the formation of authigenic rock at cold seeps focuses on the role of microbes in creating geochemically favorable environment for the precipitation of carbonate and barite minerals. Less understood is the pathway that lithified microbial patches of seafloor sediment follow to become rock formations that are identified in strata dating back to the Silurian. In this study I will compare Holocene seep rock from the Gulf of Mexico to Cretaceous carbonates that have been identified as seep rock. Through the study of rock in its early stages of formation to rock that has likely undergone multiple phases of diagenesis I aim to establish a hypothetical sequence of formation of the Cretaceous seep rocks
Synchronization in the presence of distributed delays
We study systems of identical coupled oscillators introducing a distribution
of delay times in the coupling. For arbitrary network topologies, we show that
the frequency and stability of the fully synchronized states depend only on the
mean of the delay distribution. However, synchronization dynamics is sensitive
to the shape of the distribution. In the presence of coupling delays, the
synchronization rate can be maximal for a specific value of the coupling
strength.Comment: 6 pages, 3 figure
Optimal cellular mobility for synchronization arising from the gradual recovery of intercellular interactions
Cell movement and intercellular signaling occur simultaneously during the
development of tissues, but little is known about how movement affects
signaling. Previous theoretical studies have shown that faster moving cells
favor synchronization across a population of locally coupled genetic
oscillators. An important assumption in these studies is that cells can
immediately interact with their new neighbors after arriving at a new location.
However, intercellular interactions in cellular systems may need some time to
become fully established. How movement affects synchronization in this
situation has not been examined. Here we develop a coupled phase oscillator
model in which we consider cell movement and the gradual recovery of
intercellular coupling experienced by a cell after movement, characterized by a
moving rate and a coupling recovery rate respectively. We find (1) an optimal
moving rate for synchronization, and (2) a critical moving rate above which
achieving synchronization is not possible. These results indicate that the
extent to which movement enhances synchrony is limited by a gradual recovery of
coupling. These findings suggest that the ratio of time scales of movement and
signaling recovery is critical for information transfer between moving cells.Comment: 18 single column pages + 1 table + 5 figures + Supporting Informatio
- …