31,197 research outputs found
Optimal Capacity of the Blume-Emery-Griffiths perceptron
A Blume-Emery-Griffiths perceptron model is introduced and its optimal
capacity is calculated within the replica-symmetric Gardner approach, as a
function of the pattern activity and the imbedding stability parameter. The
stability of the replica-symmetric approximation is studied via the analogue of
the Almeida-Thouless line. A comparison is made with other three-state
perceptrons.Comment: 10 pages, 8 figure
Fermion confinement via Quantum Walks in 2D+1 and 3D+1 spacetime
We analyze the properties of a two and three dimensional quantum walk that
are inspired by the idea of a brane-world model put forward by Rubakov and
Shaposhnikov [1]. In that model, particles are dynamically confined on the
brane due to the interaction with a scalar field. We translated this model into
an alternate quantum walk with a coin that depends on the external field, with
a dependence which mimics a domain wall solution. As in the original model,
fermions (in our case, the walker), become localized in one of the dimensions,
not from the action of a random noise on the lattice (as in the case of
Anderson localization), but from a regular dependence in space. On the other
hand, the resulting quantum walk can move freely along the "ordinary"
dimension.Comment: 5 pages, 6 figure
Ultrasonic cavity solitons
We report on a new type of localized structure, an ultrasonic cavity soliton,
supported by large aspect-ratio acoustic resonators containing viscous media.
The spatio-temporal dynamics of this system is analyzed on the basis of a
generalized Swift-Hohenberg equation, derived from the microscopic equations
under conditions close to nascent bistability. These states of the acoustic and
thermal fields are robust structures, existing whenever a spatially uniform
solution and a periodic pattern coexist. An analytical solution for the
ultrasonic cavity soliton is also presented
Convolutional Goppa Codes
We define Convolutional Goppa Codes over algebraic curves and construct their
corresponding dual codes. Examples over the projective line and over elliptic
curves are described, obtaining in particular some Maximum-Distance Separable
(MDS) convolutional codes.Comment: 8 pages, submitted to IEEE Trans. Inform. Theor
Exact Effective action for (1+1)-dimensional fermions in an Abelian background at finite temperature and chemical potential
In this paper we study the effects of a nonzero chemical potential in the
effective action for massless fermions in (1+1) dimensions in an abelian gauge
field background at finite temperature. We calculate the n-point function and
show that the structure of the amplitudes corresponds to a generalization of
the structure noted earlier in a calculation without a chemical potential (the
associated integrals carry the dependence on the chemical potential). Our
calculation shows that the chiral anomaly is unaffected by the presence of a
chemical potential at finite temperature. However, unlike the earlier
calculation (in the absence of a chemical potential) odd point functions do not
vanish. We trace this to the fact that in the presence of a chemical potential
the generalized charge conjugation symmetry of the theory allows for such
amplitudes. In fact, we find that all the even point functions are even
functions of the chemical potential while the odd point functions are odd
functions of it which is consistent with this generalized charge conjugation
symmetry. We show that the origin of the structure of the amplitudes is best
seen from a formulation of the theory in terms of left and right handed
spinors. The calculations are also much simpler in this formulation and it
clarifies many other aspects of the theory
Reliability of the Omron HBF-500 Body Composition Monitor
The Omron HBF-500 incorporates both hand-to-hand and foot-to-foot electrical impedance technology. At this time, the authors are not aware of any studies examining the consistency of this monitor. PURPOSE: To assess the reliability of the Omron HBF-500 body composition monitor. METHODS: Twelve men and six women signed an informed consent and participated in the study (32.4±8.7 years, 169.9±7.5 cm, 81.4±15.9 kg, 28.2±5.5 kg.m-2). Participants reported to the laboratory on three separate occasions separated by at least one day and within one week. Participants were asked to refrain from exercise and caffeine on the days of testing and, were asked to not eat a heavy meal three hours prior and to remain normally hydrated. For each trial, height was measured on a Seca 214 portable height rod (Hamburg, Germany) and weight on a Detecto DR 400 digital platform scale (Webb City, MO) without shoes or socks and with one layer of light clothing. Participants then had their body weight and body fat percent (BF%) assessed on the Omron HBF-500 body composition monitor. On the second day of testing, body BF% was also assessed using a Biodynamics 450 bioimpedance analyzer (Seattle, WA). RESULTS: There were no significant differences between the trials for weight assessed on the digital platform scale, F(2,17) = 1.2, p = 0.308, and on the Omron HBF-500, F(2,17) = 2.6, p = 0.086 (Table 1). There were also no significant differences between the trials for body fat assessed on the Omron F(2,17) = 1.0, p = 0.351. Reliability assessed with Cronbachâs alpha was high between the trials of each of the measures (Digital scale (kg), α = 0.999, Omron (kg), α = 0.999, Omron (BF%), α = 0.998). A dependent t-test indicated a significant difference in BF% between the Omron and Biodynamics analyzer (34.2±9.6 and 38.8±12.8, respectively), t(15) = -2.9, p = 0.011. Finally, dependent t-tests revealed body weight measured by the Omron was significantly greater than the Detecto scale in trial 2, t(17) = -6.9, p = 0.001, and in trial 3, t(17) = -7.9, p = 0.001. CONCLUSIONS: The Omron HBF-500 seems to consistently measure body weight and body composition. Although the HBF-500 can be questioned as an accurate measure of body composition, it seems to be a useful tool if one is interested in tracking changes in body weight and BF%
On the ongoing multiple blowout in NGC 604
Several facts regarding the structure of NGC 604 are examined here. The three
main cavities, produced by the mechanical energy from massive stars which in
NGC 604 are spread over a volume of 10 pc, are shown here to be
undergoing blowout into the halo of M33. High resolution long slit spectroscopy
is used to track the impact from massive stars while HST archive data is used
to display the asymmetry of the nebula.
NGC 604 is found to be a collection of photoionized filaments and sections of
shells in direct contact with the thermalized matter ejected by massive stars.
The multiple blowout events presently drain the energy injected by massive
stars and thus the densest photoionized gas is found almost at rest and is
expected to suffer a slow evolution.Comment: 15 pages (11 text), 4 figures. To be published in Ap
Effect of self-healing additions on the development of mechanical strength of cement paste
Important research efforts have been recently focused on the development of self-healing cement composites. The healing mechanism, implemented within the material, must be automatically initiated as soon as the first signs of damage appear at the micro-scale. For doing so, two different additions have been developed to incorporate them simultaneously into the cementitious matrix: silica microcapsules containing an epoxy sealing compound (CAP) and nanosilica particles functionalized with amine groups (NS). As a first step to the development of a self-healing concrete with these two additions, their pozzolanic activity has been measured by an accelerated test. The high values of fixed lime obtained at 28 days (85% for CAP, 93% for NS and 88% for a mix of them) suggest that they are suitable for construction materialsâ applications. Furthermore, the behaviour of the additions in an ordinary Portland cement paste with 20 wt.% of commercial micro-silica has been studied, considering the partial substitution of micro-silica by CAP, NS and their mix. High values of compressive strength (>60 MPa) have been obtained in all cases after 28 days of hydration. However, while the addition of CAP induces a reduction of the compressive strength of the 24% with respect to the reference material, the addition of NS gives rise to a slight enhancement of the strength (5%) due to a pozzolanic reaction confirmed by X-ray diffraction data. Finally, in the presence of both CAP and NS, the beneficial effect of the nanosilica is counteracted by the microcapsules and a reduction of 28% is obtained for the compressive strength
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