8,124 research outputs found
Investigation of compounds essential for the origin of life
Nucleic acid sequencing as a technique to determine the chemical and biological evolution of certain prokaryotic metabolic pathways is discussed. Protein in data and a microbiological organization of the prokaryotes is included
Online identification and nonlinear control of the electrically stimulated quadriceps muscle
A new approach for estimating nonlinear models of the electrically stimulated quadriceps muscle group under nonisometric conditions is investigated. The model can be used for designing controlled neuro-prostheses. In order to identify the muscle dynamics (stimulation pulsewidth-active knee moment relation) from discrete-time angle measurements only, a hybrid model structure is postulated for the shank-quadriceps dynamics. The model consists of a relatively well known time-invariant passive component and an uncertain time-variant active component. Rigid body dynamics, described by the Equation of Motion (EoM), and passive joint properties form the time-invariant part. The actuator, i.e. the electrically stimulated muscle group, represents the uncertain time-varying section. A recursive algorithm is outlined for identifying online the stimulated quadriceps muscle group. The algorithm requires EoM and passive joint characteristics to be known a priori. The muscle dynamics represent the product of a continuous-time nonlinear activation dynamics and a nonlinear static contraction function described by a Normalised Radial Basis Function (NRBF) network which has knee-joint angle and angular velocity as input arguments. An Extended Kalman Filter (EKF) approach is chosen to estimate muscle dynamics parameters and to obtain full state estimates of the shank-quadriceps dynamics simultaneously. The latter is important for implementing state feedback controllers. A nonlinear state feedback controller using the backstepping method is explicitly designed whereas the model was identified a priori using the developed identification procedure
Rehabilitation following first-time patellar dislocation: a randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises.
Purpose: Define whether distal vastus medialis (VM) muscle strengthening improves functional outcomes compared to general quadriceps muscles strengthening following first-time patellar dislocation (FTPD). Methods: Fifty patients post-FTPD were randomised to either a general quadriceps exercise or rehabilitation programme (n=25) or to a specific-VM exercise and rehabilitation regime (n=25). Primary outcome was the Lysholm Knee Score, secondary outcomes included the Tegner Level of Activity Scale, the Norwich Patellar Instability (NPI) Score, and isometric knee extensions strength at various knee flexion ranges of motion. Outcomes were assessed at baseline, six weeks, six months and 12 months. Results: There were statistically significant differences in functional outcome and activity levels through the Lysholm Knee Score and Tegner Level of Activity Scale at 12 months in the general quadriceps exercise group compared to the VM group (p=0.05; 95% CI: -14.0 to 0.0/p=0.04; 95% CI: -3.0 to 0.0). This did not reach a clinically important difference. There was no statistically significant difference between the groups for the NPI Score and isometric strength at any follow-up interval. The trial experienced substantial participant attrition (52% at 12 months). Conclusions: Whilst there was a statistical difference in Lysholm Knee Score and Tegner Level of Activity Score between general quadriceps and VM exercise groups at 12 months, this may not have necessarily been clinically important. This trial highlights that the recruitment and retention of participants from this population is a challenge and should be considered during the design of future trials in this populatio
Effect of certain adsorbents and mineral mixtures on the availability of riboflavin and other B-vitamins in (synthetic and natural) rations
Age of high-grade gneisses south of Grand Lake, Newfoundland
Crystalline rocks of the Steel Mountain Subzone of the Humber Zone in southwest Newfoundland give an age for granulite-grade metamorphism of 1498+9/-8 Ma, similar to ages from the Long Range inlier and northwestern Cape Breton Island. Peralkaline leucogranite was emplaced at 608 Ā± 4 Ma. The emplacement of anorthosite-gabbro complexes and amphibolite-grade metamorphism took place between these dates. The southern part of the Dunnage Zone (Central Gneiss Subzone), in contact with the Steel Mountain Subzone at the Long Range Fault, lacks Precambrian crystalline rocks, but was intruded by charnockitic plutons and metamorphosed to granulite facies at 460 Ā±10 Ma. This subzone was exhumed before 435 Ma. In the Meelpaeg Subzone of the Gander Zone, which is in contact with the Central Gneiss Subzone along the Victoria River Fault, the oldest intrusive component of a granoblastic migmatitic gneiss was emplaced at 418 Ā± 4 Ma.
These data demonstrate that both the Long Range and Victoria River faults form major tectonic boundaries. Subzones appear to have been thrust westward in Silurian or later time.
RÉSUMÉ
Les roches cristallines de la sous-zone du mont Steel, dans la zone de Humber du sud-ouest de Terre-Neuve, ont donné des âges de 1498+9/-8 Ma pour le métamorphisme de haul grade, similaires à ceux de la boutonnière de Long Range et du nord de l'ile-du-Cap-Breton. Un leucogranite peralcalin s'est mis en place à 608 Ā± 4 Ma. L'intrusion des complexes à anorthosite-gabbro et le métamorphisme au faciès amphibolite se sont produits entre ces deux évènements. La partie sud de la zone de Dunnage (sous-zone de gneiss centrale), en contact avec la sous-zone du mont Steel a la faille de Long Range, ne contient pas de roches cristallines précambriennes mais à 616 recouped par des plutons charnockitiques et à 616 métamorphisée au faciès granulite à 460 Ā± 10 Ma. Cette sous-zone a été exhumge avant 435 Ma. Dans la sous-zone Mulpaeg de la zone de Gander, qui est mise en contact avec la sous-zone de gneiss centrale par la faille de la rivière Victoria, la phase intrusive la plus ancienne d'un gneiss migmatitique et granoblastique s'est mise en place à 418 Ā± 4 Ma.
Ces données démontrent que les failles de Long Range et de la rivière Victoria sont des frontières tectoniques majeures. Les sous-zones semblent avoir subi un chevauchement vers l'ouest au plus tard au Silurien.
[Traduit par le journal
Ferromagnetism below the Stoner limit in La-doped SrB_6
Spin-polarized band calculations for LaSr_7B_{48} show a weak ferro-magnetic
state. This is despite a low density-of-states (DOS) and a low Stoner factor.
The reason for the magnetic state is found to be associated with a gain in
potential energy in addition to the exchange energy, as a spin-splitting is
imposed. An impurity like La DOS is essential for this effect. It makes a
correction to the Stoner factor, and provides an explanation of the recently
observed weak ferro-magnetism in doped hexaborides.Comment: 6 pages, 2 tables, 1 figur
Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy
The gas circulation loop LOOPINO has been set up and commissioned at Tritium
Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium
mixtures under conditions similar to the inner loop system of the neutrino-mass
experiment KATRIN, which is currently under construction. A custom-made
interface is used to connect the tritium containing measurement cell, located
inside a glove box, with the Raman setup standing on the outside. A tritium
sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more
than three weeks with a total throughput of 770 g of tritium. Compositional
changes in the sample and the formation of tritiated and deuterated methanes
CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen
isotope exchange reactions and gas-wall interactions, due to tritium {\beta}
decay. A precision of 0.1% was achieved for the monitoring of the T_2
Q_1-branch, which fulfills the requirements for the KATRIN experiment and
demonstrates the feasibility of high-precision Raman measurements with tritium
inside a glove box
Water Dynamics at Protein Interfaces: Ultrafast Optical Kerr Effect Study
The behavior of water molecules surrounding a protein can have an important bearing on its structure and function. Consequently, a great deal of attention has been focused on changes in the relaxation dynamics of water when it is located at the protein surface. Here we use the ultrafast optical Kerr effect to study the H-bond structure and dynamics of aqueous solutions of proteins. Measurements are made for three proteins as a function of concentration. We find that the water dynamics in the first solvation layer of the proteins are slowed by up to a factor of 8 in comparison to those in bulk water. The most marked slowdown was observed for the most hydrophilic protein studied, bovine serum albumin, whereas the most hydrophobic protein, trypsin, had a slightly smaller effect. The terahertz Raman spectra of these protein solutions resemble those of pure water up to 5 wt % of protein, above which a new feature appears at 80 cmā1, which is assigned to a bending of the protein amide chain
17O NMR study of q=0 spin excitations in a nearly ideal S=1/2 1D Heisenberg antiferromagnet, Sr2CuO3, up to 800 K
We used 17O NMR to probe the uniform (wavevector q=0) electron spin
excitations up to 800 K in Sr2CuO3 and separate the q=0 from the q=\pm\pi/a
staggered components. Our results support the logarithmic decrease of the
uniform spin susceptibility below T ~ 0.015J, where J=2200 K. From measurement
of the dynamical spin susceptibility for q=0 by the spin-lattice relaxation
rate 1/T_{1}, we demonstrate that the q=0 mode of spin transport is ballistic
at the T=0 limit, but has a diffusion-like contribution at finite temperatures
even for T << J.Comment: Submitted to Phys. Rev. Lett. 4 pages, 4 figure
iRGD peptide conjugation potentiates intraperitoneal tumor delivery of paclitaxel with polymersomes
Polymersomes are versatile nanoscale vesicles that can be used for cytoplasmic delivery of payloads. Recently, we demonstrated that pH-sensitive polymersomes exhibit an intrinsic selectivity towards intraperitoneal tumor lesions. A tumor homing peptide, iRGD, harbors a cryptic C-end Rule (CendR) motif that is responsible for neuropilin-1 (NRP-1) binding and for triggering extravasation and tumor penetration of the peptide. iRGD functionalization increases tumor selectivity and therapeutic efficacy of systemic drug-loaded nanoparticles in many tumor models. Here we studied whether intraperitoneally administered paclitaxel-loaded iRGD-polymersomes show improved efficacy in the treatment of peritoneal carcinomatosis. First, we demonstrated that the pH-sensitive polymersomes functionalized with RPARPAR (a prototypic CendR peptide) or iRGD internalize in the cells that express NRP-1, and that internalized polymersomes release their cargo inside the cytosol. CendR-targeted polymersomes loaded with paclitaxel were more cytotoxic on NRP-1-positive cells than on NRP-1-negative cells. In mice bearing peritoneal tumors of gastric (MKN-45P) or colon (CT26) origin, intraperitoneally administered RPARPAR and iRGD-polymersomes showed higher tumor-selective accumulation and penetration than untargeted polymersomes. Finally, iRGD-polymersomes loaded with paclitaxel showed improved efficacy in peritoneal tumor growth inhibition and in suppression of local dissemination compared to the pristine paclitaxel-polymersomes or Abraxane. Our study demonstrates that iRGD-functionalization improves efficacy of paclitaxel-polymersomes for intraperitoneal treatment of peritoneal carcinomatosis
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