1,011 research outputs found
Structureâfunction analysis of the RNA polymerase cleft loops elucidates initial transcription, DNA unwinding and RNA displacement.
The active center clefts of RNA polymerase (RNAP) from the archaeon Pyrococcus furiosus (Pfu) and of yeast RNAP II are nearly identical, including four protruding loops, the lid, rudder, fork 1 and fork 2. Here we present a structureâfunction analysis of recombinant Pfu RNAP variants lacking these cleft loops, and analyze the function of each loop at different stages of the transcription cycle. All cleft loops except fork 1 were required for promoter-directed transcription and efficient elongation. Unprimed de novo transcription required fork 2, the lid was necessary for primed initial transcription. Analysis of templates containing a pre-melted bubble showed that rewinding of upstream DNA drives RNA separation from the template. During elongation, downstream DNA strand separation required template strand binding to an invariant arginine in switch 2, and apparently interaction of an invariant arginine in fork 2 with the non-template strand
Changing and unchanging on Tadpole domination number in G â e, G + e graphs
In this paper, the effect of âTadpole dominationâ change is examined, which is one of the domination types, when a graph is modified, by deleting or adding an edge in G. This edge deletion may represent a cut in a network. The occurrence of any interruption in connections of this network may lead to the pause of data transmission in the network and thus affect the work of the entire network, as well as the need to create new necessary connections within the network or excluding others for the possibility of reducing the cost. Based on these criteria âTadpole domination numberâ change has been examined. The increase, decrease, and non-increase or decrease was determined for this number, in case of deletion or addition, and we have proved some basic cases for this domination change.Publisher's Versio
Molecular Dynamics Simulation of Semiflexible Polyampholyte Brushes - The Effect of Charged Monomers Sequence
Planar brushes formed by end-grafted semiflexible polyampholyte chains, each
chain containing equal number of positively and negatively charged monomers is
studied using molecular dynamics simulations. Keeping the length of the chains
fixed, dependence of the average brush thickness and equilibrium statistics of
the brush conformations on the grafting density and the salt concentration are
obtained with various sequences of charged monomers. When similarly charged
monomers of the chains are arranged in longer blocks, the average brush
thickness is smaller and dependence of brush properties on the grafting density
and the salt concentration is stronger. With such long blocks of similarly
charged monomers, the anchored chains bond to each other in the vicinity of the
grafting surface at low grafting densities and buckle toward the grafting
surface at high grafting densities.Comment: 8 pages,7 figure
Kualitas Semen Segar Itik Mojosari (Anas Platyrhyncos javanicus) pada Pembatasan Pemberian Pakan
The high quality of semen is important to support fertilization and semen collection for the insemination. One of the factors influencing the semen quality is feed. The feed shortages and the excess of feed, both of them affect on the semen production and its quality. So the aim of this study was to evaluate the effect of feed restriction on the semen characteristics of Mojosari duck. 60 Mojosari ducks(male) were used. They were reared from 4-39 weeks age. This experiment used complete randomize design.As treatment was the restriction on feeding, that consist of four levels : ad libitum (100%) for starter-layer period (P1), feed on starter-grower 100%, layer 85% (P2), feed on starter-grower85%, layer 100% (P3), and feed on starter-layer 85% (P4). The result of this study showed that the treatments did not significantly affect on volume semen per ejaculat, spermatozoa concentration, total spermatozoa per ejaculat, motility, viability, and percentage of spermatozoa abnormality. Spermatozoa without tail on P1 was higher significant than those on another treatments (P2, P3, and P4). This study indicated that feed restriction (85% adlibitum) from starter-layer period (P4) on the Mojosari duck was sufficient to produce semen with high quality
Role of Multipoles in Counterion-Mediated Interactions between Charged Surfaces: Strong and Weak Coupling
We present general arguments for the importance, or lack thereof, of the
structure in the charge distribution of counterions for counterion-mediated
interactions between bounding symmetrically charged surfaces. We show that on
the mean field or weak coupling level, the charge quadrupole contributes the
lowest order modification to the contact value theorem and thus to the
intersurface electrostatic interactions. The image effects are non-existent on
the mean-field level even with multipoles. On the strong coupling level the
quadrupoles and higher order multipoles contribute additional terms to the
interaction free energy only in the presence of dielectric inhomogeneities.
Without them, the monopole is the only multipole that contributes to the strong
coupling electrostatics. We explore the consequences of these statements in all
their generality.Comment: 12 pages, 3 figure
The one dimensional Coulomb lattice fluid capacitor
22 pages, 18 figures, RevTexInternational audienceThe one dimensional Coulomb lattice fluid in a capacitor configuration is studied. The model is formally exactly soluble via a transfer operator method within a field theoretic representation of the model. The only interactions present in the model are the one dimensional Coulomb interaction between cations and anions and the steric interaction imposed by restricting the maximal occupancy at any lattice site to one particle. Despite the simplicity of the model, a wide range of intriguing physical phenomena arise, some of which are strongly reminiscent of those seen in experiments and numerical simulations of three dimensional ionic liquid based capacitors. Notably we find regimes where over-screening and density oscillations are seen near the capacitor plates. The capacitance is also shown to exhibit strong oscillations as a function of applied voltage. It is also shown that the corresponding mean field theory misses most of these effects. The analytical results are confirmed by extensive numerical simulations
Sensory substitution for force feedback recovery: A perception experimental study
Robotic-assisted surgeries are commonly used today as a more efficient alternative to traditional surgical options. Both surgeons and patients benefit from those systems, as they offer many advantages, including less trauma and blood loss, fewer complications, and better ergonomics. However, a remaining limitation of currently available surgical systems is the lack of force feedback due to the teleoperation setting, which prevents direct interaction with the patient. Once the force information is obtained by either a sensing device or indirectly through vision-based force estimation, a concern arises on how to transmit this information to the surgeon. An attractive alternative is sensory substitution, which allows transcoding information from one sensory modality to present it in a different sensory modality. In the current work, we used visual feedback to convey interaction forces to the surgeon. Our overarching goal was to address the following question: How should interaction forces be displayed to support efficient comprehension by the surgeon without interfering with the surgeonâs perception and workflow during surgery? Until now, the use the visual modality for force feedback has not been carefully evaluated. For this reason, we conducted an experimental study with two aims: (1) to demonstrate the potential benefits of using this modality and (2) to understand the surgeonsâ perceptual preferences. The results derived from our study of 28 surgeons revealed a strong positive acceptance of the users (96%) using this modality. Moreover, we found that for surgeons to easily interpret the information, their mental model must be considered, meaning that the design of the visualizations should fit the perceptual and cognitive abilities of the end user. To our knowledge, this is the first time that these principles have been analyzed for exploring sensory substitution in medical robotics. Finally, we provide user-centered recommendations for the design of visual displays for robotic surgical systems.Peer ReviewedPostprint (author's final draft
Ionic Cloud Distribution close to a Charged Surface in the Presence of Salt
Despite its importance, the understanding of ionic cloud distribution close
to a charged macroion under physiological salt conditions has remained very
limited especially for strongly coupled systems with, for instance, multivalent
counterions. Here we present a formalism that predicts both counterion and
coion distributions in the vicinity of a charged macroion for an arbitrary
amount of added salt and in both limits of mean field and strong coupling. The
distribution functions are calculated explicitly for ions next to an infinite
planar charged wall. We present a schematic phase diagram identifying different
physical regimes in terms of electrostatic coupling parameter and bulk salt
concentration.Comment: 6 pages, 2 figure
Strong Coupling Electrostatics in the Presence of Dielectric Inhomogeneities
We study the strong-coupling (SC) interaction between two like-charged
membranes of finite thickness embedded in a medium of higher dielectric
constant. A generalized SC theory is applied along with extensive Monte-Carlo
simulations to study the image charge effects induced by multiple dielectric
discontinuities in this system. These effects lead to strong counterion
crowding in the central region of the inter-surface space upon increasing the
solvent/membrane dielectric mismatch and change the membrane interactions from
attractive to repulsive at small separations. These features agree
quantitatively with the SC theory at elevated couplings or dielectric mismatch
where the correlation hole around counterions is larger than the thickness of
the central counterion layer.Comment: 4 pages, 3 figure
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