Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes

We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M_w > 7.5 do not reliably predict available geodetic data. In particular, we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic (teleseismic and two strong motion stations) or geodetic (InSAR and GPS) data. The differences might be related to postseismic deformation or, more likely, the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties. The earthquakes studied here follow the pattern of earthquake directivity along the coast of western South America, north of 5°S, earthquakes rupture to the north; south of about 12°S, directivity is southerly; and in between, earthquakes are bilateral. The predicted deformation at the Arequipa GPS station from the seismic-only slip model for the 7 July 2001 aftershock is not consistent with significant preseismic motion

Cryptography based on neural networks - analytical results

Mutual learning process between two parity feed-forward networks with discrete and continuous weights is studied analytically, and we find that the number of steps required to achieve full synchronization between the two networks in the case of discrete weights is finite. The synchronization process is shown to be non-self-averaging and the analytical solution is based on random auxiliary variables. The learning time of an attacker that is trying to imitate one of the networks is examined analytically and is found to be much longer than the synchronization time. Analytical results are found to be in agreement with simulations

Cohesin cleavage by separase is enhanced by a substrate motif distinct from the cleavage site.

Chromosome segregation begins when the cysteine protease, separase, cleaves the Scc1 subunit of cohesin at the metaphase-to-anaphase transition. Separase is inhibited prior to metaphase by the tightly bound securin protein, which contains a pseudosubstrate motif that blocks the separase active site. To investigate separase substrate specificity and regulation, here we develop a system for producing recombinant, securin-free human separase. Using this enzyme, we identify an LPE motif on the Scc1 substrate that is distinct from the cleavage site and is required for rapid and specific substrate cleavage. Securin also contains a conserved LPE motif, and we provide evidence that this sequence blocks separase engagement of the Scc1 LPE motif. Our results suggest that rapid cohesin cleavage by separase requires a substrate docking interaction outside the active site. This interaction is blocked by securin, providing a second mechanism by which securin inhibits cohesin cleavage

Training a perceptron in a discrete weight space

On-line and batch learning of a perceptron in a discrete weight space, where each weight can take $2 L+1$ different values, are examined analytically and numerically. The learning algorithm is based on the training of the continuous perceptron and prediction following the clipped weights. The learning is described by a new set of order parameters, composed of the overlaps between the teacher and the continuous/clipped students. Different scenarios are examined among them on-line learning with discrete/continuous transfer functions and off-line Hebb learning. The generalization error of the clipped weights decays asymptotically as $exp(-K \alpha^2)$/$exp(-e^{|\lambda| \alpha})$ in the case of on-line learning with binary/continuous activation functions, respectively, where $\alpha$ is the number of examples divided by N, the size of the input vector and $K$ is a positive constant that decays linearly with 1/L. For finite $N$ and $L$, a perfect agreement between the discrete student and the teacher is obtained for $\alpha \propto \sqrt{L \ln(NL)}$. A crossover to the generalization error $\propto 1/\alpha$, characterized continuous weights with binary output, is obtained for synaptic depth $L > O(\sqrt{N})$.Comment: 10 pages, 5 figs., submitted to PR

Beyond a "woman's problem" : the role of relationship processes in female genital pain

Female genital pain is a prevalent condition that can disrupt the psychosexual and relational well-being of affected women and their romantic partners. Despite the intimate context in which the pain can be elicited (i.e., during sexual intercourse), interpersonal correlates of genital pain and sexuality have not been widely studied in comparison to other psychosocial factors. This review describes several prevailing theoretical models explaining the role of the partner in female genital pain: the operant learning model, cognitive-behavioral and communal coping models, and intimacy models. The review includes a discussion of empirical research on the interpersonal and partner correlates of female genital pain and the impact of genital pain on partners’ psychosexual adjustment. Together, this research highlights a potential reciprocal interaction between both partners’ experiences of female genital pain. The direction of future theoretical, methodological, and clinical research is discussed with regard to the potential to enhance understanding of the highly interpersonal context of female genital pai

Trends in aerosol abundances and distributions

The properties of aerosols that reside in the upper atmosphere are described. Special emphasis is given to the influence these aerosols have on ozone observation systems, mainly through radiative effects, and on ambient ozone concentrations, mainly through chemical effects. It has long been appreciated that stratospheric particles can interfere with the remote sensing of ozone distribution. The mechanism and magnitude of this interference are evaluated. Separate sections deal with the optical properties of upper atmospheric aerosols, long-term trends in stratospheric aerosols, perturbations of the stratospheric aerosol layer by volcanic eruptions, and estimates of the impacts that such particles have on remotely measured ozone concentrations. Another section is devoted to a discussion of the polar stratospheric clouds (PSC's). These unique clouds, recently discovered by satellite observation, are now thought to be intimately connected with the Antarctic ozone hole. Accordingly, interest in PSC's has grown considerably in recent years. This chapter describes what we know about the morphology, physical chemistry, and microphysics of PSC's

The conservation of energy-momentum and the mass for the graviton

In this work we give special attention to the bimetric theory of gravitation with massive gravitons proposed by Visser in 1998. In his theory, a prior background metric is necessary to take in account the massive term. Although in the great part of the astrophysical studies the Minkowski metric is the best choice to the background metric, it is not possible to consider this metric in cosmology. In order to keep the Minkowski metric as background in this case, we suggest an interpretation of the energy-momentum conservation in Visser's theory, which is in accordance with the equivalence principle and recovers naturally the special relativity in the absence of gravitational sources. Although we do not present a general proof of our hypothesis we show its validity in the simple case of a plane and dust-dominated universe, in which the `massive term' appears like an extra contribution for the energy density.Comment: 9 pages, accepted for publishing in GR

V405 Aurigae: A High Magnetic Field Intermediate Polar

Our simultaneous multicolor (UBVRI) circular polarimetry has revealed nearly sinusoidal variation over the WD spin cycle, and almost symmetric positive and negative polarization excursions. Maximum amplitudes are observed in the B and V bands (+-3 %). This is the first time that polarization peaking in the blue has been discovered in an IP, and suggests that V405 Aur is the highest magnetic field IP found so far. The polarized flux spectrum is similar to those found in polars with magnetic fields in the range B ~ 25-50 MG. Our low resolution circular spectropolarimetry has given evidence of transient features which can be fitted by cyclotron harmonics n = 6, 7, and 8, at a field of B = 31.5 +- 0.8 MG, consistent with the broad-band polarized flux spectrum. Timings of the circular polarization zero crossovers put strict upper limits on WD spin period changes and indicate that the WD in V405 Aur is currently accreting closely at the spin equilibrium rate, with very long synchronization timescales, T_s > 10^9 yr. For the observed spin to orbital period ratio, P_{spin}/P_{orb} = 0.0365, and P_{orb} ~ 4.15 hr, existing numerical accretion models predict spin equilibrium condition with B ~ 30 MG if the mass ratio of the binary components is q_1 ~ 0.4. The high magnetic field makes V405 Aur a likely candidate as a progenitor of a polar.Comment: To appear in The Astrophysical Journal, September 1 Issue (2008), 9 pages, 10 figure

Teleparallel Energy-Momentum Distribution of Static Axially Symmetric Spacetimes

This paper is devoted to discuss the energy-momentum for static axially symmetric spacetimes in the framework of teleparallel theory of gravity. For this purpose, we use the teleparallel versions of Einstein, Landau-Lifshitz, Bergmann and M$\ddot{o}$ller prescriptions. A comparison of the results shows that the energy density is different but the momentum turns out to be constant in each prescription. This is exactly similar to the results available in literature using the framework of General Relativity. It is mentioned here that M$\ddot{o}$ller energy-momentum distribution is independent of the coupling constant $\lambda$. Finally, we calculate energy-momentum distribution for the Curzon metric, a special case of the above mentioned spacetime.Comment: 14 pages, accepted for publication in Mod. Phys. Lett.