3,313 research outputs found
Ac magnetic susceptibility of a molecular magnet submonolayer directly patterned onto a microSQUID sensor
We report the controlled integration, via Dip Pen Nanolithography, of
monolayer dots of ferritin-based CoO nanoparticles (12 Bohr magnetons) into the
most sensitive areas of a microSQUID sensor. The nearly optimum flux coupling
between these nanomagnets and the microSQUID improves the achievable
sensitivity by a factor 100, enabling us to measure the linear susceptibility
of the molecular array down to very low temperatures (13 mK). This method opens
the possibility of applying ac susceptibility experiments to characterize
two-dimensional arrays of single molecule magnets within a wide range of
temperatures and frequencies.Comment: 4 pages 3 figure
Actividad ovina y diversificación de los modos de vida rurales en la alta montaña mexicana
UnpublishedTomo I . Sección: Sistemas Ganaderos-Economía y Gestión. Sesión: Sostenibilidad. Ponencia nº 3
Time dependence of breakdown in a global fiber-bundle model with continuous damage
A time-dependent global fiber-bundle model of fracture with continuous damage
is formulated in terms of a set of coupled non-linear differential equations. A
first integral of this set is analytically obtained. The time evolution of the
system is studied by applying a discrete probabilistic method. Several results
are discussed emphasizing their differences with the standard time-dependent
model. The results obtained show that with this simple model a variety of
experimental observations can be qualitatively reproduced.Comment: APS style, two columns, 4 figures. To appear in Phys. Rev.
Instability of scale-free networks under node-breaking avalanches
The instability introduced in a large scale-free network by the triggering of
node-breaking avalanches is analyzed using the fiber-bundle model as conceptual
framework. We found, by measuring the size of the giant component, the
avalanche size distribution and other quantities, the existence of an abrupt
transition. This test of strength for complex networks like Internet is more
stringent than others recently considered like the random removal of nodes,
analyzed within the framework of percolation theory. Finally, we discuss the
possible implications of our results and their relevance in forecasting
cascading failures in scale-free networks.Comment: 4 pages, 4 figures, final version to be published in Europhys. Let
Bounds for the time to failure of hierarchical systems of fracture
For years limited Monte Carlo simulations have led to the suspicion that the
time to failure of hierarchically organized load-transfer models of fracture is
non-zero for sets of infinite size. This fact could have a profound
significance in engineering practice and also in geophysics. Here, we develop
an exact algebraic iterative method to compute the successive time intervals
for individual breaking in systems of height in terms of the information
calculated in the previous height . As a byproduct of this method,
rigorous lower and higher bounds for the time to failure of very large systems
are easily obtained. The asymptotic behavior of the resulting lower bound leads
to the evidence that the above mentioned suspicion is actually true.Comment: Final version. To appear in Phys. Rev. E, Feb 199
Probabilistic Approach to Time-Dependent Load-Transfer Models of Fracture
A probabilistic method for solving time-dependent load-transfer models of
fracture is developed. It is applicable to any rule of load redistribution,
i.e, local, hierarchical, etc. In the new method, the fluctuations are
generated during the breaking process (annealed randomness) while in the usual
method, the random lifetimes are fixed at the beginning (quenched disorder).
Both approaches are equivalent.Comment: 13 pages, 4 figures. To appear in Phys.Rev.
Comparative study of PCR-sexing procedures using bovine embryos fertilized with sex-sorted spermatozoa
Sex determination in bovine embryos is a useful tool in reproductive biotechnology. This work compares two techniques of embryo sexing by polymerase chain reaction (PCR. Embryos were produced in vitro with sex-sorted sperm and two techniques of DNA lysis were tested (proteinase K versus heat shock). Subsequently, halves of each lysed sample was amplified both by amelogenin and BRY4a/SAT1 primers. Male embryos treated by both digestion methods and amplified by BRY4a/SAT1 gave higher rates of false negatives. Amelogenin amplification failed with embryos previously digested by proteinase K. In contrast, the lysis method allowed obtaining the best accuracy in terms of sex verification when using amelogenin amplification
Transmission of light through periodic arrays of square holes: From a metallic wire mesh to an array of tiny holes
J. Bravo-Abad, L. Martín-Moreno, F. J. García-Vidal, Euan Hendry, and J. Gómez Rivas, Physical Review B, Vol. 76, article 241102(R) (2007). "Copyright © 2007 by the American Physical Society."A complete landscape is presented of the electromagnetic coupling between square holes forming a two-dimensional periodic array in a metallic film. By combining both experimental and theoretical results along with a first-principles Fano model, we study the crossover between the physics of metallic wire meshes (when holes occupy most of the unit cell) and the phenomenon of extraordinary optical transmission, which appears when the size of the holes is very small in comparison with the period of the array
On the system performance of DFT-S-OFDM and CP-OFDM for 5G Uplink in mmWave band
Both conventional Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) and Discrete Fourier Transform Spread OFDM (DFT-S-OFDM) have been adopted for their use in the Physical Uplink Shared Channel (PUSCH) in the 5G New Radio (NR) standard. While CP-OFDM can better exploit the frequency characteristics of the channel, DFTS-OFDM has the advantage of a lower peak-to-average power ratio (PAPR). Due to the interactions between PAPR and power amplifier (PA) non-linearity, users adopting DFT-S-OFDM waveform may benefit from a potentially higher PA efficiency and extend their coverage by increasing their transmit power. In this paper we study the uplink performance of both waveforms and their interaction with non-linear PA and uplink power control in the millimeter-wave (mmWave) band to determine their optimal operational range
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