A Test for the Origin of Quasar Redshifts

It is commonly accepted that quasar redshifts have a cosmological character and that most of the quasars are at Gigaparsec distances. However, there are some cases where several quasars with completely different redshifts and a nearby active galaxy are aligned in a certain way or occupy a very small patch on the sky, which is claimed by some authors to be unlikely to happen by chance. Is there a small subset of quasars with non-cosmological redshifts? For quasars apparently associated with galaxies, we consider two scenarios for the origin of their redshift: 1. a standard, cosmological scenario, 2. a velocity-induced Doppler shift of a nearby object's spectrum (local, ejection scenario). We argue for a simple astrometric test which can distinguish between these two sources of quasar redshifts by constraining their proper motions. We give the predictions for the maximum possible proper motions of a quasar for the cosmological and local scenarios of the origin of their redshifts. We apply these theoretical results to the Bukhmastova (2001) catalog, which contains more than 8000 close QSO-galaxy associations. In the standard interpretation of quasar redshifts, their typical proper motions are a fraction of micro arc-second, and beyond the reach of planned astrometric missions like GAIA and SIM. On the other hand, the quasars ejected from local AGNs at velocities close to the speed of light would have proper motions 5-6 orders of magnitude larger, which would easily be measurable with future astrometric missions. The distributions of proper motions for the cosmological and local scenarios are very well separated. Moreover, the division corresponds nicely to the expected accuracy from GAIA and SIM.Comment: results unchanged, minor additions, 10 pages, 6 figures, 1 table, accepted to MNRA

Crustal structure of the central Lesser Antilles island arc : seismic near-vertical and wide-angle profiling

In the context of the EU funded THALES project active seismic investigations were conducted along the Lesser Antilles subduction zone, using both, wide-angle and near-vertical techniques. The structure of the Caribbean plate and the subducting Atlantic plate was determined through a combined analysis of ocean bottom seismometer and multi-channel seismic data along a transect between 15°N and 17°N. A detailed analysis of a priori and a posteriori information of a Monte Carlo based tomography scheme with a subsequent structural evaluation by forward modeling are applied to a 2-d seismic profile south of Guadeloupe. The island arc crust of the Caribbean plate has an average thickness of 28±2 km and overrides the approximately 8 km thick late cretaceous (80 Ma) Atlantic crust. The island arc crust shows two distinct reflections, which are interpreted as an intracrustal and Moho discontinuity, respectively. To a depth of 40 km the Atlantic lithosphere subducts at an average angle of 40°. The accretionary prism gains a thickness of more than 10 km and shows high energy attenuation in the middle prism. A backstop structure is imaged by a strong lateral increase of the vertical velocity gradient superimposed on structural heterogeneities. The decollement zone reaches a thickness of up to 1.8 km and shows no seismic phase polarity change. The slow convergence rate and the subduction of the Tiburon and Barracuda ridges make this subduction zone a prime candidate for major earthquakes. Between 15°N and 17°N, the seismogenic rupture area is approximated by the contact zone between the backstop and the mantle wedge. Accordingly, this area is capable of triggering an earthquake of a magnitude of Mw 7.6 and indeed makes this active European subduction zone a place of major telluric risk

Statistical separation strategy to analyze velocity structure obtained by seismic tomography

General solutions of inverse problems often can be obtained by introducing probability distributions to sample the model space. We have developed a simple approach to define an a priori space in a tomographic study and retrieve the velocity/depth posterior distribution by a Monte Carlo method. Utilizing a fitting routine designed for very low statistics to set up and analyze the obtained tomography results, we can statistically separate the velocity/depth model space derived from inverting seismic refraction data. A profile acquired in the Lesser Antilles subduction zone reveals the effectiveness of this approach. Resolution analysis of the structural heterogeneity includes a divergence analysis that can dissect long, wide-angle profiles for deep crust and upper mantle studies. The complete information of any parameterized physical system is contained in the a posteriori distribution. Methods for analyzing and displaying key properties of the a posteriori distributions of highly nonlinear inverse problems are therefore essential in the scope of any interpretation. It is possible to map velocity variations in their extent and structure by measuring the total as well as relative divergence of the velocity structure in the a posteriori space. We have applied the divergence analysis to a part of the transect where a backstop structure has been identified, and the method resolves shallow features and returns information concerning the confidence level of results. Assuming a relationship between forearc and backstop, we can obtain a structural image in accordance with previous interpretations. ©2010 Society of Exploration Geophysicist

Development and Evaluation of an Interface with Four-Finger Pitch Selection

In this paper we present an interface for digital musical instruments which is primarily designed for playing mono-phonic melody synthesizers. The hand-held device allows the pitch selection with four valve-like metal mechanics and three octave switches. Note events are triggered with a wooden excitation pad, operated with the second hand. Another feature is the advanced aftertouch of the four me- chanics and the pad, which enables expressive playing. In a user experiment, the controller is compared to a classic MIDI keyboard, regarding the time needed for responding to simple visual stimuli and the mean error rate produced in that task. The results show no significant difference in the response time but a higher error rate for the novel in- terface for untrained users. Outcome of this work is a list of necessary improvements, as well as a plan for further experiments

The Sedimentary Sequences of the Lesser Antilles Arc South of Guadeloupe FromWide-Angle and Reflection Seismic Data

The Lesser Antilles Island Arc is a European active subduction zone prone to major earthquakes. Huge sedimentary input by the South American rivers, namely Amazon and Orinoco, has formed one of the largest accretionary complexes in the world. In the framework of the THALES project, several coincident wide-angle and multichannel seismic (MCS) profiles (15.5N and 16.5N) have been collected on the accretionary prism beetween the Barracuda and Tiburon Ridges in the Lesser Antilles. We present the analysis results of these data in order to construct a structural model. Preliminary results of 7 different MCS profiles are discussed. The data consist of 1 strike and 6 cross lines. The sedimentary layers imaged on deep-penetrating MCS data were used as a priori information for the wide angle modelling. A total of 16 OBH/OBS (Ocean Bottom Hydrophone/Seismometer) was deployed on a 130 km long wide-angle seismic profile. Seismic velocity models were obtained by a forward modelling of refracted and reflected phases. The final velocity model shows the geometry of the Antilles subduction zone with a sediment thickness of up to 2.6 km. The shallowest layer has a fill velocity of 1.8-2.2 km/s, whereas an older more compacted sediment layer in the deeper portion shows velocities ranged from 2.5 to 3.5 km/s with sediment thickness till 4.3 km. The sedimentary succession marked topographic irregularity and different directional fault system. These layers overlie oceanic crust having velocities in excess 6 km/s with depth of 14-15 km. From the coincident MCS seismic profiles, we incorporated the well resolved sedimentary portions into our model

The Parkinson's disease-linked Leucine-rich repeat kinase 2 (LRRK2) is required for insulin-stimulated translocation of GLUT4

Mutations within Leucine-rich repeat kinase 2 (LRRK2) are associated with late-onset Parkinson's disease. The physiological function of LRRK2 and molecular mechanism underlying the pathogenic role of LRRK2 mutations remain uncertain. Here, we investigated the role of LRRK2 in intracellular signal transduction. We find that deficiency of Lrrk2 in rodents affects insulin-dependent translocation of glucose transporter type 4 (GLUT4). This deficit is restored during aging by prolonged insulin-dependent activation of protein kinase B (PKB, Akt) and Akt substrate of 160 kDa (AS160), and is compensated by elevated basal expression of GLUT4 on the cell surface. Furthermore, we find a crucial role of Rab10 phosphorylation by LRRK2 for efficient insulin signal transduction. Translating our findings into human cell lines, we find comparable molecular alterations in fibroblasts from Parkinson's patients with the known pathogenic G2019S LRRK2 mutation. Our results highlight the role of LRRK2 in insulin-dependent signalling with potential therapeutic implications