Evidence of a high-velocity ionized outflow in a second narrow-line quasar PG 0844+349

Following the discovery of X-ray absorption in a high-velocity outflow from the bright quasar PG 1211 + 143 we have searched for similar features in XMM–Newton archival data of a second (high accretion rate) quasar PG 0844+349. Evidence is found for several faint absorption lines in both the EPIC and RGS spectra, whose most likely identification with resonance transitions in H-like Fe, S and Ne implies an origin in highly ionized matter with an outflow velocity of order ∼0.2c. The line equivalent widths require a line-of-sight column density of   N _H∼ 4 × 10²³ cm⁻²  , at an ionization parameter of log  ξ∼ 3.7  . Assuming a radial outflow being driven by radiation pressure from the inner accretion disc, as suggested previously for PG 1211 + 143, the flow in PG 0844+349 is also likely to be optically thick, in this case within ∼25 Schwarzschild radii. Our analysis suggests that a high-velocity, highly ionized outflow is likely to be a significant component in the mass and energy budgets of active galactic nuclei accreting at or above the Eddington rate.     

Motion on the Kaparelli fault (Greece) prior to the 1981 earthquake sequence determined from 36Cl cosmogenic dating

ABSTRACT In February and March 1981, three successive destructive earthquakes occurred at the eastern end of the Gulf of Corinth. The third shock (March, 4, Ms ≈ 6.4) ruptured the Kaparelli fault. About 40 cm of a limestone fault scarp was exhumed by the earthquake. Each major prehistoric earthquake has added new surface to this cumulative scarp exposing fresh material to cosmic-ray bombardment. Using ³⁶Cl cosmic ray exposure dating we have obtained the continuous exposure history for this 4–5-m-high limestone surface at two sites about 50 m apart. The results suggest that the Kaparelli fault has ruptured three times prior to 1981 at 20 ± 3 ka, 14.5 ± 0.5 ka and 10.5 ± 0.5 ka with slip amplitudes between 0.6 m and 2.1 m. The Kaparelli fault appears to have been inactive for 10 thousand years prior to the 1981 event.     

The H i opacity of the intergalactic medium at redshifts 1.6 < z < 3.2

We use high-quality echelle spectra of 24 quasi-stellar objects to provide a calibrated measurement of the total amount of Lyα forest absorption (DA) over the redshift range  2.2 < z < 3.2  . Our measurement of DA excludes absorption from metal lines or the Lyα lines of Lyman-limit systems and damped Lyα systems. We use artificial spectra with realistic flux calibration errors to show that we are able to place continuum levels that are accurate to better than 1 per cent. When we combine our results with our previous results between  1.6 < z < 2.2  , we find that the redshift evolution of DA is well described over  1.6 < z < 3.2  as   A (1 + z )^γ  , where   A = 0.0062  and  γ= 2.75  . We detect no significant deviations from a smooth power-law evolution over the redshift range studied. We find less H  i absorption than expected at   z = 3  , implying that the ultraviolet background is  ∼40  per cent higher than expected. Our data appears to be consistent with an H  i ionization rate of  Γ∼ 1.4 × 10⁻¹² s⁻¹  .     

Force generation for locomotion of vertebrates: skeletal muscle overview

Locomotion is essential for vertebrate survival. Forces required for movement are generated by skeletal muscle. Skeletal muscle shortening and/or force generation occur via parallel sliding of two protein filaments: actin and myosin. This is driven by the cycling of cross-bridges, whose unitary nanometer length change and picoNewton force output are fueled by conversion of chemical energy, stored in the form of adenosine triphosphate, into a change in myosin protein configuration. The range of force and length changes of a muscle is determined by factors such as muscle cross section, fiber angle, tendon attachment, and lever geometry, but also by the metabolic pathways available for adenosine triphosphate synthesis and by enzymes involved in cross-bridge cycling. In addition, muscle mechanical activity is affected by the extent of actin and myosin filament overlap. Force output can be graded by selective recruitment of motor units and/or by variation of force output from individual units. The cost of locomotion is subject to species differences and is affected by the environment and form of movement, with an energy efficiency of up to 0.4. Overall, design principles of vertebrate skeletal muscle may serve as an interesting reference point for novel actuator technologies.     

Pedosedimentary development of part of a Late Quaternary loess‐palaeosol sequence in northwest Argentina

The field properties, magnetic susceptibility, particle size, calcium carbonate content, soil micromorphology and optical luminescence ages of the upper 6.1 m and lowermost 4.7 m of the 45 m loess–palaeosol sequence at El Lambedero in the Tafí del Valle region of Tucumán Province (Sierras Pampeanas, northwest Argentina) have been used to set up a partial stratigraphy and chronology, as well as a basic pedosedimentary model of loess accumulation, palaeosol development, reworking and erosion for the site. The minimum ages derived from the basal part of the section suggest that loess began to accumulate some time before 165 ka. A thick and well‐developed pedocomplex in the upper profile is correlated with at least the latter part of marine isotope stage (MIS) 5, whereas the overlying palaeosol may be attributable to pedogenic activity during MIS 3. The absence of material younger than 33 ka close to the surface of this rounded spur landform is probably the result of either non‐deposition or erosional stripping in response to climatic change, or episodic uplift in this seismically active region. Copyright © 2004 John Wiley & Sons, Ltd.     

Enceladus' south polar sea

Recent observations of the south pole of Saturn's moon Enceladus by the Cassini spacecraft have revealed an active world, powered by internal heat. In this paper, we propose that localized subsurface melting on Enceladus has produced an internal south polar sea. Evidence for this localized sea comes from the shape of Enceladus, which does not match a differentiated body at its current orbital position. We show that melting induced by the observed heat flow at the south pole produces a large enough pit to match the shape of Enceladus with a differentiated rock and ice interior. Numerical modeling of melting and ice flow shows that the sea produced beneath the south pole is stable against inflow of ductile ice from its surroundings for the duration of the heating. The shape modification due to melting also produces a negative degree-two gravity anomaly, which can reorient the spin axis of Enceladus in order to place the sea at the pole.