1,805 research outputs found
Spatiotemporal symmetries in the disynaptic canal-neck projection
Get PDFThe vestibular system in almost all vertebrates, and in particular in humans, controls
balance by employing a set of six semicircular canals, three in each inner ear, to detect angular
accelerations of the head in three mutually orthogonal coordinate planes. Signals from the canals are
transmitted to eight (groups of) neck motoneurons, which activate the eight corresponding muscle
groups. These signals may be either excitatory or inhibitory, depending on the direction of head
acceleration. McCollum and Boyle have observed that in the cat the relevant network of neurons
possesses octahedral symmetry, a structure that they deduce from the known innervation patterns
(connections) from canals to muscles. We rederive the octahedral symmetry from mathematical
features of the probable network architecture, and model the movement of the head in response to
the activation patterns of the muscles concerned. We assume that connections between neck muscles
can be modeled by a ācoupled cell network,ā a system of coupled ODEs whose variables correspond
to the eight muscles, and that this network also has octahedral symmetry. The network and its
symmetries imply that these ODEs must be equivariant under a suitable action of the octahedral
group. It is observed that muscle motoneurons form natural āpush-pull pairsā in which, for given
movements of the head, one neuron produces an excitatory signal, whereas the other produces an
inhibitory signal. By incorporating this feature into the mathematics in a natural way, we are led
to a model in which the octahedral group acts by signed permutations on muscle motoneurons.
We show that with the appropriate group actions, there are six possible spatiotemporal patterns of
time-periodic states that can arise by Hopf bifurcation from an equilibrium representing an immobile
head. Here we use results of Ashwin and Podvigina. Counting conjugate states, whose physiological
interpretations can have significantly different features, there are 15 patterns of periodic oscillation,
not counting left-right reflections or time-reversals as being different. We interpret these patterns
as motions of the head, and note that all six types of pattern appear to correspond to natural head
motions
Construction And Verification Of Distributed Medical DatabasećUsing Resource Description Framework
Get PDFCARS 2015: Computer Assisted Radiology and Surgery --
Proceedings of the 29th International Congress and Exhibition,
Barcelona, Spain, June 24 - 27, 2015conference pape
Percolation on the average and spontaneous magnetization for q-states Potts model on graph
Full text linkWe prove that the q-states Potts model on graph is spontaneously magnetized
at finite temperature if and only if the graph presents percolation on the
average. Percolation on the average is a combinatorial problem defined by
averaging over all the sites of the graph the probability of belonging to a
cluster of a given size. In the paper we obtain an inequality between this
average probability and the average magnetization, which is a typical extensive
function describing the thermodynamic behaviour of the model
Recent X-ray measurements of the accretion-powered pulsar 4U 1907+09
Get PDFX-ray observations of the accreting X-ray pulsar 4U~1907+09, obtained during
February 1996 with the Proportional Counter Array on the Rossi X-ray Timing
Experiment (RXTE), have enabled the first measurement of the intrinsic pulse
period Ppulse since 1984: Ppulse=440.341[+0.012,-0.017] s. 4U 1907+09 is in a
binary system with a blue supergiant. The orbital parameters were solved and
this enabled the correction for orbital delay effects of a measurement of
Ppulse obtained in 1990 with Ginga. Thus, three spin down rates could be
extracted from four pulse periods obtained in 1983, 1984, 1990, and 1996. These
are within 8% equal to a value of dPpulse/dt=+0.225 s/yr. This suggest that the
pulsar is perhaps in a monotonous spin down mode since its discovery in 1983.
Furthermore, the RXTE observations show transient ~18 s oscillations during a
flare that lasted about 1 hour. The oscillations may be interpreted as
Keplerian motion of an accretion disk near the magnetospheric radius. This, and
the notion that the co-rotation radius is much larger than any conceivable
value for the magnetospheric radius (because of the long spin period), renders
it unlikely that this pulsar spins near equilibrium like is suspected for other
slowing accreting X-ray pulsars. We suggest as an alternative that perhaps the
frequent occurrence of a retrograde transient accretion disk may be
consistently slowing the pulsar down. Further observations of flares can
provide more evidence of this.Comment: 26 pages, 11 figures, to be published in Astrophysical Journal part I
on March 20, 199
Analysis for Plasma Wall Interactions in LHD and Characterizations of Co-deposited Carbon Film Using Material Probes
Get PDFSpontaneous magnetization of the Ising model on the Sierpinski carpet fractal, a rigorous result
Full text linkWe give a rigorous proof of the existence of spontaneous magnetization at
finite temperature for the Ising spin model defined on the Sierpinski carpet
fractal. The theorem is inspired by the classical Peierls argument for the two
dimensional lattice. Therefore, this exact result proves the existence of
spontaneous magnetization for the Ising model in low dimensional structures,
i.e. structures with dimension smaller than 2.Comment: 14 pages, 8 figure
Measurement of forward photon production cross-section in proton-proton collisions at = 13 TeV with the LHCf detector
Full text linkIn this paper, we report the production cross-section of forward photons in
the pseudorapidity regions of and ,
measured by the LHCf experiment with proton--proton collisions at =
13 TeV. The results from the analysis of 0.191 of data
obtained in June 2015 are compared to the predictions of several hadronic
interaction models that are used in air-shower simulations for
ultra-high-energy cosmic rays. Although none of the models agree perfectly with
the data, EPOS-LHC shows the best agreement with the experimental data among
the models.Comment: 21 pages, 4 figure
Termination of Downward-Oriented Gamma-Ray Glow by Normal-Polarity In-Cloud Discharge Activity
Full text linkWada Y., Wu T., Wang D., et al. (2023), Termination of Downward-Oriented Gamma-Ray Glow by Normal-Polarity In-Cloud Discharge Activity, Journal of Geophysical Research: Atmospheres, 128(15), e2023JD038606, 10.1029/2023JD038606. To view the published open abstract, go tohttps://doi.org/10.1029/2023JD038606.A gamma-ray glow, a minute-lasting burst of high-energy photons from a thundercloud, was detected by ground-based apparatus at Kanazawa University, Japan, in a winter thunderstorm on 18 December 2018. The gamma-ray glow was quenched by a lightning flash within a brief time window of 40Ā ms. The lightning flash produced several low-frequency (LF) E-change pulses that were temporally coincident with the termination of the gamma-ray glow, and that were located within 0.5Ā km from the observation site by the Fast Antenna Lightning Mapping Array. The LF pulses had the same polarity as a positive cloud-to-ground current and a normal-polarity in-cloud current. Since this polarity is against the upward electric field for producing the gamma-ray glow (accelerating electrons to the ground), we infer that the glow was terminated by a normal-polarity in-cloud discharge activity between a middle negative layer and an upper positive layer
The Optimal Exponent Base for emPAI Is 6.5
Get PDFExponentially Modified Protein Abundance Index (emPAI) is an established method of estimating protein abundances from peptide counts in a single LC-MS/MS experiment. EmPAI is defined as 10PAI minus one, where PAI (Protein Abundance Index) denotes the ratio of observed to observable peptides. EmPAI was first proposed by Ishihama et al [1] who found that PAI is approximately proportional to the logarithm of absolute protein concentration. I define emPAI65ā=ā6.5PAI-1 and show that it performs significantly better than emPAI, while it is equally easy to compute. The higher accuracy of emPAI65 is demonstrated by analyzing three data sets, including the one used in the original study [1]. I conclude that emPAI65 ought to be used instead of the original emPAI for protein quantitation
Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution
Get PDFRecent ground networks and satellite remote-sensing observations have
provided useful data related to spatial and vertical distributions of
mineral dust particles in the atmosphere. However, measurements of temporal
variations and spatial distributions of mineral dust deposition fluxes are
limited in terms of their duration, location, and processes of deposition.
To ascertain temporal variations and spatial distributions of mineral dust
deposition using wet and dry processes, weekly deposition samples were
obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo
(Okinawa) in Japan during October 2008āDecember 2010 using automatic wet
and dry separating samplers. Mineral dust weights in water-insoluble residue
were estimated from Fe contents measured using an X-ray fluorescence
analyser. Wet and dry deposition fluxes of mineral dusts were both high in
spring and low in summer, showing similar seasonal variations to frequency
of aeolian dust events (Kosa) in Japan. For wet deposition, highest and lowest
annual dust fluxes were found at Toyama (9.6 g m<sup>ā2</sup> yr<sup>ā1</sup>) and at
Cape Hedo (1.7 g m<sup>ā2</sup> yr<sup>ā1</sup>) as average values in 2009 and 2010.
Higher wet deposition fluxes were observed at Toyama and Tottori, where
frequent precipitation (> 60% days per month) was observed
during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and
Cape Hedo, the highest and lowest annual dust fluxes were found respectively
at Fukuoka (5.2 g m<sup>ā2</sup> yr<sup>ā1</sup>) and at
Cape Hedo (2.0 g m<sup>ā2</sup> yr<sup>ā1</sup>)
as average values in 2009 and 2010. The average ratio of wet and
dry deposition fluxes was the highest at Toyama (3.3) and the lowest at Hedo
(0.82), showing a larger contribution of the dry process at western sites,
probably because of the distance from desert source regions and because of
the effectiveness of the wet process in the dusty season.
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Size distributions of refractory dust particles were obtained using
four-stage filtration: > 20, > 10, > 5, and > 1 Ī¼m diameter. Weight fractions of the sum of
> 20 Ī¼m and 10ā20 Ī¼m (giant fraction) were
higher than 50% for most of the event samples. Irrespective of the
deposition type, the giant dust fractions generally decreased with increasing
distance from the source area, suggesting the selective depletion of larger
giant particles during atmospheric transport. Based on temporal variations of
PM<sub>c</sub> (2.5 < <i>D</i> < 10 Ī¼m),
ground-based lidar, backward air trajectories, and vertical profiles of
potential temperatures, transport processes of dust particles are discussed
for events with high-deposition and low-deposition flux with high
PM<sub>c</sub>. Low dry dust depositions with high PM<sub>c</sub>
concentrations were observed under stronger (5 K km<sup>ā1</sup>) stratification
of potential temperature with thinner and lower (< 2 km)
dust distributions because the PM<sub>c</sub> fraction of dust particles
only survived after depletion of giant dust particles by rapid gravitational
settling at the time they reach Japan. In contrast, transport through a
thicker (> 2 km) dust layer with weak vertical gradient of
potential temperature carry more giant dust particles to Japan. Because giant
dust particles are an important mass fraction of dust accumulation,
especially in the North Pacific, which is known as a high-nutrient,
low-chlorophyll (HNLC) region, the transport height and fraction of giant
dust particles are important factors for studying dust budgets in the
atmosphere and their role in biogeochemical cycles
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