Group theoretic dimension of stationary symmetric \alpha-stable random fields

The growth rate of the partial maximum of a stationary stable process was first studied in the works of Samorodnitsky (2004a,b), where it was established, based on the seminal works of Rosi\'nski (1995,2000), that the growth rate is connected to the ergodic theoretic properties of the flow that generates the process. The results were generalized to the case of stable random fields indexed by Z^d in Roy and Samorodnitsky (2008), where properties of the group of nonsingular transformations generating the stable process were studied as an attempt to understand the growth rate of the partial maximum process. This work generalizes this connection between stable random fields and group theory to the continuous parameter case, that is, to the fields indexed by R^d.Comment: To appear in Journal of Theoretical Probability. Affiliation of the authors are update

From Cooperative Scans to Predictive Buffer Management

In analytical applications, database systems often need to sustain workloads with multiple concurrent scans hitting the same table. The Cooperative Scans (CScans) framework, which introduces an Active Buffer Manager (ABM) component into the database architecture, has been the most effective and elaborate response to this problem, and was initially developed in the X100 research prototype. We now report on the the experiences of integrating Cooperative Scans into its industrial-strength successor, the Vectorwise database product. During this implementation we invented a simpler optimization of concurrent scan buffer management, called Predictive Buffer Management (PBM). PBM is based on the observation that in a workload with long-running scans, the buffer manager has quite a bit of information on the workload in the immediate future, such that an approximation of the ideal OPT algorithm becomes feasible. In the evaluation on both synthetic benchmarks as well as a TPC-H throughput run we compare the benefits of naive buffer management (LRU) versus CScans, PBM and OPT; showing that PBM achieves benefits close to Cooperative Scans, while incurring much lower architectural impact.Comment: VLDB201

Time Delays in the Synchronization of Chaotic Coupled Systems with Feedback

The synchronized excitable behavior of two coupled chaotic diode lasers with feedback was experimental and numerically studied. We determine the relation between the observed delay times in synchronized Low Frequency Fluctuation spikes and the coupling and the feedback times in the lasers.Comment: 5 pages, 6 figure

Magnetic field near the central region of the Galaxy: Rotation measure of extragalactic sources

To determine the properties of the Faraday screen and the magnetic field near the central region of the Galaxy, we measured the Faraday rotation measure (RM) towards 60 background extragalactic source components through the -6 deg < l <6 deg, -2 deg < b < 2 deg region of the Galaxy using the 4.8 and 8.5 GHz bands of the ATCA and VLA. Here we use the measured RMs to estimate the systematic and the random components of the magnetic fields. The measured RMs are found to be mostly positive for the sample sources in the region. This is consistent with either a large scale bisymmetric spiral magnetic fields in the Galaxy or with fields oriented along the central bar of the Galaxy. The outer scale of the RM fluctuation is found to be about 40 pc, which is much larger than the observed RM size scales towards the non-thermal filaments (NTFs). The RM structure function is well-fitted with a power law index of 0.7 +/- 0.1 at length scales of 0.3 to 100 pc. If Gaussian random processes in the ISM are valid, the power law index is consistent with a two dimensional Kolmogorov turbulence. If there is indeed a strong magnetic field within 1 degree (radius 150 pc) from the GC, the strength of the random field in the region is estimated to be 20 microGauss. Given the highly turbulent magnetoionic ISM in this region, the strength of the systematic component of the magnetic fields would most likely be close to that of the random component. This suggests that the earlier estimated milliGauss magnetic field near the NTFs is localised and does not pervade the central 300 pc of the Galaxy.Comment: 9 pages, 6 figures, accepted for publication in A&

Small solid renal masses: Characterization by diffusion-weighted MRI at 3 T

AIM: To describe the appearance of small solid renal lesions ( 643 cm) on diffusion-weighted magnetic resonance imaging (MRI) and to determine whether ADC measurements may help to differentiate benign from malignant small solid renal masses. METHODS AND MATERIALS: Thirty-five patients with 47 small renal masses (23 malignant, 24 benign) who underwent 3 T MRI of the kidney using diffusion-weighted sequences (b values of 0 and 1000 s/mm(2)) were retrospectively evaluated. Qualitative and quantitative analysis of diffusion-weighted images was performed. RESULTS: Most lesions were hyperintense to kidney on high b-value diffusion-weighted images and hypointense on apparent diffusion coefficient (ADC) map. The mean ADC of the lesions was significantly lower than that of kidney (1.22 \ub1 0.3 versus 1.85 \ub1 0.12 mm(2)/s; p < 0.005). The mean ADC was significantly different between renal cell carcinomas (1.2 \ub1 0.01 mm(2)/s), metastases (1.25 \ub1 0.04 mm(2)/s), angiomyolipoma (1.07 \ub1 0.3 mm(2)/s) and oncocytomas (1.56 \ub1 0.08 mm(2)/s; p < 0.05). The mean ADC of clear cell renal cell carcinomas was significantly different from that of non-clear cell renal cell carcinomas (1.38 \ub1 0.34 versus 0.83 \ub1 0.34 mm(2)/s; p < 0.005). No significant difference was found between mean ADC of fat containing and minimal fat angiomyolipomas (1.06 \ub1 0.48 versus 1.11 \ub1 0.33 mm(2)/s). CONCLUSION: Small solid renal masses are hyperintense on high b value and have different ADC values

Single chargino production via gluon-gluon fusion in a supersymmetric theory with an explicit R-parity violation

We studied the production of single chargino$\tilde{\chi}_1^{\pm}$ accompanied by $\mu^{\mp}$ lepton via gluon-gluon fusion at the LHC. The numerical analysis of their production rates is carried out in the mSUGRA scenario with some typical parameter sets. The results show that the cross sections of the $\tilde{\chi}_1^{\pm}\mu^{\mp}$ productions via gluon-gluon collision are in the order of $1 \sim 10^{2}$ femto barn quantitatively at the CERN LHC, and can be competitive with production mechanism via quark-antiquark annihilation process.Comment: LaTex file, 18 pages, 4 EPS file

The curious case of J113924.74+164144.0: a possible new group of galaxies at z = 0.0693

J113924.74+164144.0 is an interesting galaxy at z = 0.0693, i.e. D_L ~ 305 Mpc, with tidal-tail-like extended optical features on both sides. There are two neighbouring galaxies, a spiral galaxy J113922.85+164136.3 which has a strikingly similar 'tidal' morphology, and a faint galaxy J113923.58+164129.9. We report HI 21 cm observations of this field to search for signatures of possible interaction. Narrow HI emission is detected from J113924.74+164144.0, but J113922.85+164136.3 shows no detectable emission. The total HI mass detected in J113924.74+164144.0 is 7.7 x 10^9 M_solar. The HI emission from the galaxy is found to be extended and significantly offset from the optical position of the galaxy. We interpret this as signature of possible interaction with the neighbouring spiral galaxy. There is also a possible detection of HI emission from another nearby galaxy J113952.31+164531.8 at z = 0.0680 at a projected distance of 600 kpc, and with a total HI mass of 5.3 x 10^9 M_solar, suggesting that all these galaxies form a loose group at z ~ 0.069.Comment: 5 pages, 1 table, 6 figures. Accepted for publication in MNRAS Letters. The definitive version will be available at http://www.blackwell-synergy.com

A new analysis of πK\pi K scattering from Roy and Steiner type equations

With the aim of generating new constraints on the OZI suppressed couplings of chiral perturbation theory a set of six equations of the Roy and Steiner type for the $S$- and $P$-waves of the $\pi K$ scattering amplitudes is derived. The range of validity and the multiplicity of the solutions are discussed. Precise numerical solutions are obtained in the range E\lapprox 1 GeV which make use as input, for the first time, of the most accurate experimental data available at $E > 1$ GeV for both $\pi K\to\pi K$ and $\pi\pi\to K\bar{K}$ amplitudes. Our main result is the determination of a narrow allowed region for the two S-wave scattering lengths. Present experimental data below 1 GeV are found to be in generally poor agreement with our results. A set of threshold expansion parameters, as well as sub-threshold parameters are computed. For the latter, matching with the SU(3) chiral expansion at NLO is performed.Comment: 45 pages, 17 figures. v2: New title, minor correction

Pain-avoidance versus reward-seeking: an experimental investigation

According to fear-avoidance models, a catastrophic interpretation of a painful experience may give rise to pain-related fear and avoidance, leading to the development and maintenance of chronic pain problems in the long term. However, little is known about how exactly motivation and goal prioritization play a role in the development of pain-related fear. This study investigates these processes in healthy volunteers using an experimental context with multiple, competing goals. In a differential human fear-conditioning paradigm, 57 participants performed joystick movements. In the control condition, one movement (conditioned stimulus; CS+) was followed by a painful electrocutaneous unconditioned stimulus (pain-US) in 50% of the trials, whereas another movement (nonreinforced conditioned stimulus; CS-) was not. In the experimental condition, a reward in the form of lottery tickets (reward-US) accompanied the presentation of the pain-US. Participants were classified into 3 groups, as a function of the goal, they reported to be the most important: (1) pain-avoidance, (2) reward-seeking, and (3) both goals being equally important. Results indicated that neither the reward co-occurring with pain nor the prioritized goal modulated pain-related fear. However, during subsequent choice trials, participants selected the painful movement more often when the reward was presented compared with the context in which the reward was absent. The latter effect was dependent on goal prioritization, with more frequent selections in the reward-seeking group, and the least selections in the pain-avoidance group. Taken together, these results underscore the importance of competing goals and goal prioritization in the attenuation of avoidance behavior