3,403 research outputs found
Instrument manual for the retarding ion mass spectrometer on Dynamics Explorer-1
The retarding ion mass spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation
Boldness traits, not dominance, predict exploratory flight range and homing behaviour in homing pigeons
This study investigated whether consistent individual differences in behaviour (particularly exploratory tendency and object neophilia) were associated with the tendency to explore in free-ranging scenarios. This was tested in homing pigeons. The results showed that birds that were more likely to explore in the loft were also more likely to explore the local area during self-driven flights. When birds were released from a fixed release points, those which had explored less took more tortuous and longer routes back to the loft. This demonstrates the cost associated with lack of exploratory behaviour, and also links traits measured in laboratory scenarios to behaviour in free-ranging animals
Analysis of two-player quantum games in an EPR setting using geometric algebra
The framework for playing quantum games in an Einstein-Podolsky-Rosen (EPR)
type setting is investigated using the mathematical formalism of Clifford
geometric algebra (GA). In this setting, the players' strategy sets remain
identical to the ones in the classical mixed-strategy version of the game,
which is then obtained as proper subset of the corresponding quantum game. As
examples, using GA we analyze the games of Prisoners' Dilemma and Stag Hunt
when played in the EPR type setting.Comment: 20 pages, no figure, revise
Detecting Delamination via Nonlinear Wave Scattering in a Bonded Elastic Bar
In this paper we examine the effect of delamination on wave scattering, with
the aim of creating a control measure for layered waveguides of various bonding
types. Previous works have considered specific widths of solitary waves for the
simulations, without analysing the effect of changing the soliton parameters.
We consider two multi-layered structures: one containing delamination
"sandwiched" by perfect bonding and one containing delamination but
"sandwiched" by soft bonding. These structures are modelled by coupled
Boussinesq-type equations. Matched asymptotic multiple-scale expansions lead to
coupled Ostrovsky equations in soft bonded regions and Korteweg-De Vries
equations in the perfectly bonded and delaminated region. We use the Inverse
Scattering Transform to predict the behaviour in the delaminated regions. In
both cases, numerical analysis shows that we can predict the delamination
length by changes in the wave structure, and that these changes depend upon the
Full Width at Half Magnitude (FWHM) of the incident soliton. In the case of
perfect bonding, we derive a theoretical prediction for the change and confirm
this numerically. For the soft bonding case, we numerically identify a similar
relationship using the change in amplitude. Therefore we only need to compute
one curve to determine the behaviour for any incident solitary wave, creating a
framework for designing measurement campaigns for rigorously testing the
integrity of layered structures.Comment: 12 pages, 7 figure
The field theory of symmetrical layered electrolytic systems and the thermal Casimir effect
We present a general extension of a field-theoretic approach developed in
earlier papers to the calculation of the free energy of symmetrically layered
electrolytic systems which is based on the Sine-Gordon field theory for the
Coulomb gas. The method is to construct the partition function in terms of the
Feynman evolution kernel in the Euclidean time variable associated with the
coordinate normal to the surfaces defining the layered structure. The theory is
applicable to cylindrical systems and its development is motivated by the
possibility that a static van der Waals or thermal Casimir force could provide
an attractive force stabilising a dielectric tube formed from a lipid bilayer,
an example of which are t-tubules occurring in certain muscle cells. In this
context, we apply the theory to the calculation of the thermal Casimir effect
for a dielectric tube of radius and thickness formed from such a
membrane in water. In a grand canonical approach we find that the leading
contribution to the Casimir energy behaves like which gives
rise to an attractive force which tends to contract the tube radius. We find
that for the case of typical lipid membrane t-tubules. We
conclude that except in the case of a very soft membrane this force is
insufficient to stabilise such tubes against the bending stress which tend to
increase the radius. We briefly discuss the role of lipid membrane reservoir
implicit in the approach and whether its nature in biological systems may
possibly lead to a stabilising mechanism for such lipid tubes.Comment: 28 pages, 2 figures, LaTe
A mathematical model characterising Achilles tendon dynamics in flexion
The purpose of this study is to acquire mechanistic knowledge of the gastrocnemius muscle-Achilles tendon complex behaviour during specific movements in humans through mathematical modelling. Analysis of this muscle-tendon complex was performed to see if already existing muscle-tendon models of other parts of the body could be applied to the leg muscles, especially the gastrocnemius muscle-Achilles tendon complex, and whether they could adequately characterise its behaviour. Five healthy volunteers were asked to take part in experiments where dorsiflexion and plantar flexion of the foot were studied. A model of the Achilles tendon-gastrocnemius muscle was developed, incorporating assumptions regarding the mechanical properties of the muscle fibres and the tendinous tissue in series. Ultrasound images of the volunteers, direct measurements and additional mathematical calculations were used to parameterise the model. Ground reaction forces, forces on specific joints and moments and angles for the ankle were obtained from a Vicon 3D motion capture system. Model validation was performed from the experimental data captured for each volunteer and from reconstruction of the movements of specific trajectories of the joints, muscles and tendons involved in those movements
Upregulation of transmembrane endothelial junction proteins in human cerebral cavernous malformations
OBJECT: Cerebral cavernous malformations (CCMs) are among the most prevalent cerebrovascular malformations, and endothelial cells seem to play a major role in the disease. However, the underlying mechanisms, including endothelial intercellular communication, have not yet been fully elucidated. In this article, the authors focus on the endothelial junction proteins CD31, VE-cadherin, and occludin as important factors for functional cell-cell contacts known as vascular adhesion molecules and adherence and tight junctions. METHODS: Thirteen human CCM specimens and 6 control tissue specimens were cryopreserved and examined for the presence of VE-cadherin, occludin, and CD31 by immunofluorescence staining. Protein quantification was performed by triplicate measurements using western blot analysis. RESULTS: Immunofluorescent analyses of the CCM sections revealed a discontinuous pattern of dilated microvessels and capillaries as well as increased expression of occludin, VE-cadherin, and CD31 in the intima and in the enclosed parenchymal tissue compared with controls. Protein quantification confirmed these findings by showing upregulation of the levels of these proteins up to 2-6 times. CONCLUSIONS: A protocol enabling the molecular and morphological examination of the intercellular contact proteins in human CCM was validated. The abnormal and discontinuous pattern in these endothelial cell-contact proteins compared with control tissue explains the loose intercellular junctions that are considered to be one of the causes of CCM-associated bleeding or transendothelial oozing of erythrocytes. Despite the small number of specimens, this study demonstrates for the first time a quantitative analysis of endothelial junction proteins in human CCM
Testing the gravitational theory with short-period stars around our Galactic Center
Motion of short-period stars orbiting the supermassive black hole in our
Galactic Center has been monitored for more than 20 years. These observations
are currently offering a new way to test the gravitational theory in an
unexplored regime: in a strong gravitational field, around a supermassive black
hole. In this proceeding, we present three results: (i) a constraint on a
hypothetical fifth force obtained by using 19 years of observations of the two
best measured short-period stars S0-2 and S0-38 ; (ii) an upper limit on the
secular advance of the argument of the periastron for the star S0-2 ; (iii) a
sensitivity analysis showing that the relativistic redshift of S0-2 will be
measured after its closest approach to the black hole in 2018.Comment: 4 pages, 2 figures, proceedings of the 52nd Rencontres de Moriond,
Gravitation Sessio
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