Dynamic compensation in the central Pacific Ocean

The intermediate-wavelength geoid (lambda similar to 2000 km) and sea-floor topography fields in the central Pacific Ocean were studied in terms of static and dynamic compensation models. Topographic features on the sea-floor with lambda less than 1000 km were found to be compensated both regionally, by the elastic strength of the lithosphere, and locally, by displacing mantle material to reach isostatic adjustment. The larger-scale sea-floor topography and the corresponding geoid anomalies with lambda similar to 2000 km cannot be explained by either local or regional compensation. The topography and the resulting geoid anomaly at this wavelength were modeled by considering the dynamic effects arising from viscous stresses in a layer of fluid with a highly temperature-dependent viscosity for the cases of: (1) surface cooling, and (2) basal heating. In this model, the mechanical properties of the elastic part of the lithosphere were taken into account by considering an activation energy of about 520 kJ/mol in the Arrhenius law for the viscosity. Numerical predictions of the topography, total geoid anomaly, and admittance were obtained, and the results show that the thermal perturbation in the layer, which accounts for the mass deficit, must be located close to the surface to compensate the gravitational effect of the surface deformation. For the case of basal heating, the temperature dependence of viscosity results in a separation of the upper, quasi-rigid lid from the lower mobile fluid, hence inhibiting the development of a compensating thermal perturbation at shallow depths. The results clearly rule out small-scale, upper-mantle convection as the source of these anomalies. Instead, the geophysical observables can be well explained by a shallow, transient thermal perturbation

An investigation of diameter measurement repeatability using a coordinate measuring machine and a multi-baseline repeatability assessment methodology

The need for reliable and consistent measurement has become more acute with the use of statistical process control (SPC), gage repeatability and reproducibility (Gage R&R) assessment, and high precision, computer-controlled gaging systems. Although it is often overlooked, the inspection methodology under which various features are inspected has an impact on Gage R&R results. This notion was confirmed when a 1993 thesis study substantiated inspection methodology as a source of measurement variability in direct computer-controlled, coordinate measuring machines (DCC/CMMs). Although this study explored a methodology to bring measurement variability under statistical control, the tested assessment methodology--single baseline repeatability assessment--was not validated. This study was initiated to assess the effectiveness of multi-baseline repeatability assessment (MBRA) in (a) identifying diameter/probe hit categories with inherent stability in measurement repeatability on the XY, XZ, and YX planes and (b) generating planar inspection programs that yield improvements in diameter measurement repeatability on each of the three planes. The methodology of this study was based on a Brown & Sharpe Xcel 7•6•5 CMM, twenty-three circular test specimens of different diameters, an inspection methodology varying from 3-10 probe hits, and two repeatability determination methods--range and standard deviation. The results of this study indicated: (a) in general, diameter measurement repeatability can be improved by increasing the number of contact probe hits; (b) MBRA is an effective methodology for quantifying stability in measurement repeatability; and (c) MBRA is not an effective methodology for improving measurement repeatability (diameter/probe hit categories with the greatest stability did not necessarily possess the best repeatability). The principle implication presented by this study is that multi-baseline repeatability assessment gives CMM users an assessment tool that can be used to establish (a) inspection methodologies under which different features can be inspected with high precision, (b) part orientations (planes) under which circular features can be inspected with high precision, (c) machine signatures upon which machine wear can be monitored and tracked, and (d) machine signatures upon which repeatability comparison studies can be conducted

The delineation and interpretation of the earth's gravity field

A series of fluid dynamical experiments in variable viscosity fluid have been made and are in progress to study: (1) the onset of small scale convection relative to lithosphere growth rate; (2) the influence of paired fracture zones in modulating the horizontal scale of small scale convection; (3) the influence of the mantle vertical viscosity structure on determing the mode of small scale convection; and (4) the 3-D and temporal evolution of flows beneath a high viscosity lid. These experiments extend and amplify the present experimental work that has produced small scale convection beneath a downward-moving solidification front. Rapid growth of a high viscosity lid stifles the early onset of convection such that convection only begins once the lithosphere is older than a certain minimum age. The interplay of this convection with both the structure of the lithosphere and mantle provide a fertile field of investigation into the origin of geoid, gravity, and topographic anomalies in the central Pacific. These highly correlated fields of intermediate wavelength (approximately 200 to 2000 km), but not the larger wavelengths. It is the ultimate, dynamic origin of this class of anomalies that is sought in this investigation

Single Injection of Bupivacaine for Correction of Strabismus

To evaluate the effectiveness of a single injection of Bupivacaine (BPX) application for correction of eso/exodeviations this study has been performed. A retrospective review of 30 patients with eso/exodeviations less than 20 prism diopters (PD). Preoperative deviations were recorded in PD, using the alternate prism cover test. Postoperative angles at 1 and 3 months were measured in the same manner. The mean angle of deviation for near in all patients reduced significantly by 3.1 PD and 2.1 PD at 1 and 3 months. The mean angle of deviation for distance in all patients also decreased significantly by 2.3 PD and 1.9 PD at 1 and 3 months. As conclusions, single injection of BPX in a heterogeneous group of patients with horizontal strabismus caused a mild improvement in a qualitative success rate of 37%

Single Injection of Bupivacaine for Correction of Strabismus

To evaluate the effectiveness of a single injection of Bupivacaine (BPX) application for correction of eso/exodeviations this study has been performed. A retrospective review of 30 patients with eso/exodeviations less than 20 prism diopters (PD). Preoperative deviations were recorded in PD, using the alternate prism cover test. Postoperative angles at 1 and 3 months were measured in the same manner. The mean angle of deviation for near in all patients reduced significantly by 3.1 PD and 2.1 PD at 1 and 3 months. The mean angle of deviation for distance in all patients also decreased significantly by 2.3 PD and 1.9 PD at 1 and 3 months. As conclusions, single injection of BPX in a heterogeneous group of patients with horizontal strabismus caused a mild improvement in a qualitative success rate of 37%

When and how does labour lead to love? The ontogeny and mechanisms of the IKEA effect

We elevate our constructions to a special status in our minds. This ‘IKEA’ effect leads us to believe that our creations are more valuable than items that are identical, but constructed by another. This series of studies utilises a developmental perspective to explore why this bias exists. Study 1 elucidates the ontogeny of the IKEA effect, demonstrating an emerging bias at age 5, corresponding with key developmental milestones in self-concept formation. Study 2 assesses the role of effort, revealing that the IKEA effect is not moderated by the amount of effort invested in the task in 5-to-6-year olds. Finally, Study 3 examines whether feelings of ownership moderate the IKEA effect, finding that ownership alone cannot explain why children value their creations more. Altogether, results from this study series are incompatible with existing theories of the IKEA bias. Instead, we propose a new framework to examine biases in decision making. Perhaps the IKEA effect reflects a link between our creations and our self-concept, emerging at age 5, leading us to value them more positively than others’ creations

Modelling mid-crustal migmatite terrains as feeder zones for granite plutons: the competing dynamics of melt transfer by bulk versus porous flow

The common association of mid-crustal migmatites with an upper-level granite pluton could indicate that the migmatites are a feeder zone for the pluton. If magma from a deeper level pervasively intrudes a high temperature metamorphic complex, most of the intruded magma would not freeze because of the prevailing temperature. The interaction between the magma and country rocks, which could include partial melting and crystallisation of the magma passing through, would modify magma to a more granitic composition, as found in the higher-level pluton. The physical aspect of the magma transport through such a hot feeder zone is modelled by introducing a dimensionless melt transport (MT) number, which is the ratio of the rate of melt movement caused by the bulk flow of the entire mass (melt+solid) to that of porous media flow of melt only through the solid framework. The MT number is strongly dependent on the melt content of the melt-rich zone (MRZ), the diameter of the MRZ and typical particle size in the MRZ. The 300-Ma, diatexitic, Lauterbrunnen migmatites (LM) in the Aar massif, Swiss Alps, may be such a feeder zone for the nearby 303-Ma Gastern granite (GG). The chemical and field evidence indicates that the LM formed by an intrusion of intermediate composition magma, which interacted with country rocks to produce a magma of GG compos