Vorticity and non-coaxiality in progressive deformations

A measure of the non-coaxiality involved in progressive deformation histories is proposed in the form of the kinematical vorticity number, W_k. This number is a measure of the relative effects of rotation of material lines (relative to the instantaneous stretching axes) and of stretching of these material lines. As such, W_k, is a measure of the instantaneous degree of non-coaxiality. A detailed example is first presented in the form of a progressive simple shearing in which the shear plane rotates relative to an external coodinate system. This is followed by examples of more complicated deformation histories. Three specific types of progressive, isochoric (constant volume) deformation histories are recognized. Those for which 0 ≤ W_k < 1 correspond to deformation histories where no line that has been extended is shortened in future increments; W_k > 0 is a special case of these corresponding to a coaxial history. Histories with W_k > 0 are non-coaxial. Those histories with W_k = 1 correspond to progressive simple shearing. Those histories with 1 < W_k < ∞ are pulsating and lines that have been extended may be shortened in future increments.     

Some problems in digital heat-flow measurement

The most accurate method of digitizing a resistance requires that a bridge be brought to null balance by means of digital steps. Satisfactory circuits of reasonable complexity require irregular electrical dissipation in the sensors, and a relatively wide frequency bandwidth in the detector. This combination places considerably greater demands on sensor quality than do conventional electromechanical recorders, and this has been strikingly confirmed during the initial use at sea of a newly developed digital resistance recorder with a sensitivity of 10^?5. Mounted on a coring tool, with miniature outrigger sensors to measure geothermal gradients in the pelagic sediment, the recorder produces sensor readings with considerable scatter even when the sensor probes are buried in sediment. These contrast sharply to the steady reading of the calibration arm. An additional symptom with some sensors is the shunning of certain numbers in the low decades of the digital readings. The reading scatter varies sharply among different sensor types and can be satisfactorily explained by the production of a high level of white noise when the sensors are biased with excitation current. No adequate explanation has been found for the preferential reading of certain numbers, and it is necessary to speculate about obscure contact effects in those sensors.     

Studies of oceanic tectonics utilizing detailed surveying and stratigraphy

The sea floor off the coasts of Washington and southern British Columbia consists of two major features: the Cascadia Basin and the chain of seamounts to the west of it, called the Cobb Rise. The Basin is magnetically featureless and appears to be a syncline deeply filled by sediment. Clues to the tectonic history of the region are therefore more likely to be found on and beyond the Cobb Rise, which forms the western boundary of the Basin and interrupts the westward flow of terrigenous sediment. A program of detailed topographic and magnetic surveving, complemented by heat-flow coring and seismic profiling, is underway to attempt to determine the structure and history of the abyssal hills on the seaward side of Cobb Rise. Knowledge of the stratigraphy and the topography of the basement-sediment interface is expected to reveal the approximate age of the sea floor in this area and possibly the nature of the basement itself. The magnetic and geothermal data may provide direct evidence of the subcrustal structure associated with Cobb Rise, particularly if the transition zone between the high heat flow on the rise and the low heat flow west of it can be studied in detail. A small seamount has been discovered at 47°N, 132°W and has been intensively surveyed as the nucleus of the future survey area. It rises 630 meters above the surrounding bumpy plain and has extremely steep faces to the south and east. Heat flow near the seamount is somewhat below the oceanic average and the several long gravity cores obtained in the area show some correlable layering in the pelagic ooze.     

The spread of subducted lithospheric material along the mid-mantle boundary

Studies of phase transitions in silicate minerals at high temperatures and pressures suggest that the bulk density of subducted lithosphere at the mid-mantle boundary is intermediate between the densities of the upper and lower mantle. We argue that, if this is the case, then the lithospheric material will intrude along the mid-mantle boundary driven by buoyancy forces resulting from the compositional density differences between the intrusion and its surroundings. The rate of spread of the intrusion is given by a balance between these buoyancy forces and the viscous resistance of the mantle to motion. Using results from our recent studies of the fluid mechanics of such viscous gravity currents, we find that lithospheric material can propagate between one thousand and two thoudand kilometres in a hundred million years and can cover the entire boundary in one to six billion years. This spreading may be reflected in the global distribution of the isotopic characteristics of oceanic basalts.     

THE PREPARATION OF THREE BASE-METAL REFERENCE MATERIALS: LEAD CONCENTRATE, IGS-42, ZINC CONCENTRATE, IGS-43 AND COPPER MATTE, IGS-44

Three base-metal concentrates, each weighing 25 kg, were ground to -175 mesh (90 μm) and homogenised. They were then sub-sampled into foil-lined envelopes and sealed under argon before being issued to 27 participating laboratories for analysis. Over 4000 analytical results were returned and, after evaluation, a total of 37 elements within the three samples have been given recommended or more cautious probable values. The high standard of precision attained has enabled clear-cut distinctions to be made between methods for the determination of some elements. The most important of these is between titrimetry and electrogravimetry in the determination of copper.     

Structural history of high-pressure metamorphic rocks in the southern vanoise massif,french alps,and their relation to alpine tectonic events

A nappe of amphibolite-facies metamorphic rocks of pre-Permian age in the southern Vanoise massif (the Arpont schist) has been affected by an Alpine HP/LT metamorphism. The first mesoscopically recognizable deformation (D₁) post-dated the high-pressure peak (jadeitic pyroxene + quartz, glaucophane + ?lawsonite), and was associated with glaucophane + epidote. D₁ produced a flat-lying schistosity and a NW-trending glaucophane lineation, and was probably associated with nappe displacement involving NW-directed subhorizontal shear. D₂ formed small-scale folds and a foliation associated with chlorite + albite. The changing parageneses during the period pre-D₁ to D₁ to D₂ suggest decreasing pressure, so that the deformation appears to have been related to the uplift history, rather than to the process of tectonic burial. D₂ was followed by a static metamorphism (green biotite + chlorite + albite), possibly of Lepontine age. SE-directed backthrusting and folding (D₃), and later differential uplift along steep faults, took place under low-grade conditions.     

Late quaternary sediments in Lake Zürich,Switzerland

Lake Zürich occupies a glacially overdeepened perialpine trough in the northern Middlelands of Switzerland. A total of 154.4 m of Quaternary sediments and 47.3 m of Tertiary Molasse bedrock has been cored from the deepest part of the lake, some 10 km south of the city of Zürich. Some 16.8 m of gravels and sands directly overlying the bedrock include basal till and probably earliest subglacial fluvial and lacustrine deposits. These are overlain by 98.6 m of fine-grained, glacial-aged sediments comprising completely deformed proglacial and/or subglacial lacustrine muds, separated by four basal mud tills. The lack of interglacial sediments, fossils, and other datable material, and the presence of severe sediment deformation and unknown amounts of erosion prevent the establishment of an exact chronostratigraphy for sediments older than the upper mud till. Above it some 8.6 m of lacustrine muds were deposited, folded, faulted, and tilted during the final opening of the lake at about 17,500–17,000 years ago. Superimposed are 30.4 m of final Würm and post-glacial sediments comprising (from oldest): cyclic proglacial mud, thick-bedded and laminated mud, a complex transition zone, laminated carbonate, laminated marl, and diatom-calcite varves. These sediments reflect changing catchment and lacustrine conditions including: glacial proximity, catchment stability, lake inflow characteristics, thermal structure, chemistry, and bed stability. Average sedimentation rates ranged from 11 cm yr⁻¹ immediately after glacier withdrawal, to as low as 0.4 mm yr⁻¹ as the environment stabilized. The lack of coarse outwash deposits separating the fine-grained glaciolacustrine sediments from a corresponding underlying basal till suggests that deglaciation of the deep northern basin of Lake Zürich was by stagnation-zone retreat rather than by retreat of an active ice-front.     

An early-time infrared and optical study of the Type Ia Supernova 1998bu in M96

We present first-season infrared (IR) and optical photometry and spectroscopy of the Type Ia Supernova 1998bu in M96. We also report optical polarimetry of this event. SN 1998bu is one of the closest type Ia supernovae of modern times, and the distance of its host galaxy is well determined. We find that SN 1998bu is both photometrically and spectroscopically normal. However, the extinction to this event is unusually high, with     We find that SN 1998bu peaked at an intrinsic     Adopting a distance modulus of 30.25 (Tanvir et al.) and using Phillips et al.'s relations for the Hubble constant, we obtain     Combination of our IR photometry with those of Jha et al. provides one of the most complete early-phase IR light curves for a SN Ia published so far. In particular, SN 1998bu is the first normal SN Ia for which good pre- t _{B max} IR coverage has been obtained. It reveals that the J , H and K light curves peak about 5 days earlier than the flux in the B -band curve.     

Doppler imaging of BD+22°4409 (LO Peg) using least-squares deconvolution

We present maximum-entropy reconstructions of the rapidly rotating dwarf single star BD+22°4409 (LO Peg) from observations at the William Herschel Telescope in 1993 August. Since this star is too faint to use the conventional single- or three-line Doppler imaging methods, we make use of the novel method of least-squares deconvolution, which utilizes the large number of photospheric lines in an echelle spectrum to produce a single high signal-to-noise ratio profile.
The star-spot distributions from the image reconstructions show cool features at both high and low latitudes, in contradiction to recent theoretical predictions of the dynamo behaviour in rapidly rotating stars. Cross-correlation of the images from consecutive nights shows a good correlation from the small-scale structures, but no evidence of surface differential rotation. From the cross-correlation of the high-latitude spot we are able to reject the period of 9.22 h of Jeffries et al. in favour of their preferred period of 10.17 h, confirming the result of Robb & Cardinal.     

RoboNet‐II: Follow‐up observations of microlensing events with a robotic network of telescopes

RoboNet‐II uses a global network of robotic telescopes to perform follow‐up observations of microlensing events in the Galactic Bulge. The current network consists of three 2 m telescopes located in Hawaii and Australia (owned by Las Cumbres Observatory) and the Canary Islands (owned by Liverpool John Moores University). In future years the network will be expanded by deploying clusters of 1 m telescopes in other suitable locations. A principal scientific aim of the RoboNet‐II project is the detection of cool extra‐solar planets by the method of gravitational microlensing. These detections will provide crucial constraints to models of planetary formation and orbital migration. RoboNet‐II acts in coordination with the PLANET microlensing follow‐up network and uses an optimization algorithm (“web‐PLOP”) to select the targets and a distributed scheduling paradigm (eSTAR) to execute the observations. Continuous automated assessment of the observations and anomaly detection is provided by the ARTEMiS system (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)