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The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.

Recent observational studies have provided detailed descriptions of double‐diffusive staircases in the Beaufort Sea, characterized by well‐mixed intrusions between high‐gradient interfaces. These structures result from double‐diffusive convection, occurring when cooler fresh water lies atop the warmer saltier Atlantic water layer. In the present study, we investigate the spatial structure of such layers, by analyzing combined high resolution data from a subsurface mooring, a ship‐towed profiling conductivity‐temperature‐depth/ADCP package, and a free‐falling microstructure profiler. At large scale, the modular microstructure profiler data suggest a horizontal "ragged edge" of the layered water masses near the basin boundary. At smaller scales, the mooring data indicate that, in the 300–400 m depth interval, regions of layers abruptly appear. This laterally sharp (of the order of 100 m) interface is advected southwards, as shown by the shallow water integrated mapping system survey conducted nearby. Neither disruption nor formation of layers is directly observed in our data, and we thus interpret our observations as the stable and possibly recent abutment of a layered and an unlayered water masses, now globally advected southwards by a large scale flow. Plain Language Summary: Double‐diffusive layers, that is, a vertical alternating of constant and varying density layers in the stratification, are seen in the Arctic, but their exact generation and destruction mechanisms are still unknown. Their study is of primary importance since they set heat transfer rates in the Arctic Ocean. Using high resolution measurements, we document a watermass boundary between a layered and an unlayered regions, drifting southwards past our site due to a large scale mean flow. The edges are laterally sharp and have complicated structure. Neither formation of layers nor active destruction is detected in our measurements, and the sharp boundary is constant on time scales of days–weeks while being advected. Key Points: High resolution measurements show a sharp boundary between regions with and without double diffusive staircases in southeast Canada BasinThe transition from regions with to without staircases occurs on length scales of order 100 mNeither formation of layers nor active disruption is directly observed at the interface [ABSTRACT FROM AUTHOR]

When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom water passes through the Samoan Passage, where it is hydraulically controlled, while the remainder is diverted around the Manihiki Plateau and is not controlled. These observations raise a number of questions concerning the dynamics necessary to support such a regime in the steady state, the nature of upstream influence and the usefulness of rotating hydraulic theory to predict the partitioning of volume transport between the two paths, which assumes the controlled branch is inviscid. Through the use of a theory for constant potential vorticity flow and accompanying numerical model, we show that a steady-state regime similar to what is observed is dynamically possible provided that sufficient bottom friction is present in the uncontrolled branch. In this case, the upstream influence that typically exists for rotating channel flow is transformed into influence into how the flow is partitioned. As a result, the partitioning of volume flux can still be reasonably well predicted with an inviscid theory that exploits the lack of upstream influence. [ABSTRACT FROM AUTHOR]

It is well established that small-scale cross-density (diapycnal) turbulent mixing induced by breaking of overturns in the interior of the ocean plays a significant role in sustaining the deep ocean circulation and in regulating tracer budgets such as those of heat, carbon and nutrients. There has been significant progress in the fluid mechanical understanding of the physics of breaking internal waves. Connection of the microphysics of such turbulence to the larger scale dynamics, however, is significantly underdeveloped. We offer a hybrid theoretical-statistical approach, informed by observations, to make such a link. By doing so, we define a bulk flux coefficient, ΓB, which represents the partitioning of energy available to an 'ocean box' (such as a grid cell of a coarse resolution climate model), from winds, tides, and other sources, into mixing and dissipation. Here, ΓB depends on both the statistical distribution of turbulent patches and the flux coefficient associated with individual patches, Γi. We rely on recent parametrizations of Γi and the seeming universal characteristics of statistics of turbulent patches to infer ΓB, which is the essential quantity for representation of turbulent diffusivity in climate models. By applying our approach to climatology and global tidal estimates, we showthat, on a basin scale, energeticmixing zones exhibit moderately efficientmixing that induces significant vertical density fluxes, while quiet zones (with small background turbulence levels), although highly efficient in mixing, exhibitminimal vertical fluxes. The transition between the less energetic to more energetic zones marks regions of intense upwelling and downwelling of deep waters. We suggest that such upwelling and downwelling may be stronger than previously estimated, which in turn has direct implications for the closure of the deep branch of the ocean meridional overturning circulation as well as for the associated tracer budgets. [ABSTRACT FROM AUTHOR]

Double diffusion refers to a variety of turbulent processes in which potential energy is released into kinetic energy, made possible in the ocean by the difference in molecular diffusivities between salinity and temperature. Here, we present a new method for estimating the kinetic energy dissipation rates forced by double‐diffusive convection using temperature and salinity data alone. The method estimates the up‐gradient diapycnal buoyancy flux associated with double diffusion, which is hypothesized to balance the dissipation rate. To calculate the temperature and salinity gradients on small scales we apply a canonical scaling for compensated thermohaline variance (or 'spice') on sub‐measurement scales with a fixed buoyancy gradient. Our predicted dissipation rates compare favorably with microstructure measurements collected in the Chukchi Sea. Fine et al. (2018), https://doi.org/10.1175/jpo-d-18-0028.1, showed that dissipation rates provide good estimates for heat fluxes in this region. Finally, we show the method maintains predictive skill when applied to a sub‐sampling of the Conductivity, Temperature, Depth (CTD) data. Plain Language Summary: Understanding the transport of heat in the Arctic Ocean is vital for predicting the fate of sea‐ice in the decades to come. Small‐scale turbulence is an important driver of heat transport and one of the major forms of this turbulence is known as 'double‐diffusive convection'. This is where gradients in temperature and salinity drive turbulence. It is only possible because salinity diffuses significantly slower than temperature, hence the name 'double‐diffusive'. The most direct measurements of ocean mixing require sampling velocity or temperature gradients on scales <1 mm, so‐called microstructure measurements. Here we present a new method for estimating the energy dissipated by double‐diffusive convection using temperature and salinity measurements on larger scales (100s–1000s of metres). We apply the method to a high‐resolution survey of temperature and salinity through a subsurface Arctic eddy and compare the results with simultaneous microstructure measurements. The new technique can reproduce up to 72% of the observed dissipation rates to within the measurement uncertainty. This suggests the method could be used to estimate the dissipation and so heat fluxes associated with double‐diffusive convection in regions without microstructure measurements. The method also performs well when applied to data sub‐sampled on larger scales. Key Points: We develop a method for estimating dissipation rates due to double‐diffusive convection from temperature and salinity data using an energetic argumentThe method reproduces the patterns and magnitude of dissipation rates and heat fluxes from microstructure measurements across an arctic eddyThe technique performs well even when applied to lower resolution Conductivity, Temperature, Depth (CTD) data [ABSTRACT FROM AUTHOR]

Particular pathological features of cells seen under the microscope tend to be associated with particular clinical disorders. Therefore, when a pathologist examines brain tissue from a patient with Alzheimer's disease, he should expect to observe neurofibrillary tangles (tangles of nerve cells) and deposits of amyloid, which are the characteristic findings for that disease. Similarly, Lewy bodies might be anticipated from the brain a patient with Parkinson's disease. Lewy bodies are tiny structures which seem to be accumulating within the cell bodies of nerve cells. In patients with Parkinson's disease, they are most common in the substantia nigra and the locus ceruleus, two areas of the brain important in dopamine regulation. A careful examination of the brain tissues of 36 patients with Alzheimer's disease has revealed that Lewy bodies may be present in this disorder more commonly than has been previously suspected. Thirteen of the patients were found to have Lewy bodies in the cerebral cortex upon microscopic examination of tissue from that region. Twelve of these 13 patients also had Lewy bodies in the substantia nigra and at least one other structure beneath the cerebral cortex. Furthermore, a review of the case records of the patients with the Lewy bodies suggests that perhaps such patients may constitute a distinct type of Alzheimer's disease. The patients with the Lewy bodies were found to have greater deficits in attention, linguistic fluency, and the processing of visual and spatial information. While there was an increase in tremor, mild neck rigidity, and slow movement in the Lewy body patients, there were no symptoms which had the severe character associated with Parkinson's disease. Curiously, the brains of nine of the Lewy body patients also had signs of spongiform degeneration in the cortex; this degeneration gets its name from the hole-filled 'spongy' appearance of the tissue. It is suspected that Lewy bodies may be often overlooked in the brains of patients with Alzheimer's disease, since they are more difficult to recognize than other more readily observable features (such as senile plaques). The presence of Lewy bodies in the brains of patients with Alzheimer's disease may constitute a distinct subtype of this neurological disorder. (Consumer Summary produced by Reliance Medical Information, Inc.)

Recent work demonstrates that high-resolution global models forced simultaneously by atmospheric fields and the astronomical tidal potential contain a partial internal (gravity) wave (IW) spectral continuum. Regional simulations of the MITgcm forced at the horizontal boundaries by a global run that carries a partial IW continuum spectrum are performed at the same grid spacing as the global run and at finer grid spacings in an attempt to fill out more of the IW spectral continuum. Decreasing only the horizontal grid spacing from 2 to 0.25km greatly improves the frequency spectra and slightly improves the vertical wavenumber spectra of the horizontal velocity. Decreasing only the vertical grid spacing by a factor of 3 does not yield any significant improvements. Decreasing both horizontal and vertical grid spacings yields the greatest degree of improvement, filling the frequency spectrum out to 72 cpd. Our results suggest that improved IW spectra in regional models are possible if they are run at finer grid spacings and are forced at their lateral boundaries by remotely generated IWs. Additionally, consistency relations demonstrate that improvements in the spectra are indeed due to the existence of IWs at higher frequencies and vertical wavenumbers when remote IWforcing is included and model grid spacings decrease. By being able to simulate an IWspectral continuum to 0.25km scales, these simulations demonstrate that one may be able to track the energy pathways of IWs from generation to dissipation and improve the understanding of processes such as IW-driven mixing. Plain Language Summary Models of internal waves (IWs) may help us to better understand the spatial geography of mixing in the ocean and are playing an increasingly important role in the planning of satellite missions. Following recent work showing that high-resolution global models contain a partial IW spectrum, this paper describes further improvements in the spectrum seen in a high-resolution regional model forced at the boundaries by a previously performed global IW simulation. Decreasing only the horizontal grid spacing greatly improves the frequency spectra and slightly improves the vertical wavenumber spectra of velocity. Increasing only the number of vertical levels does not yield any significant improvements. Decreasing both horizontal and vertical grid spacings yields the greatest improvement in both spectra. Our results suggest that regional models can exhibit improved IW spectra over global models if two conditions are met—they must have higher horizontal and vertical resolutions, and they must have remotely generated IWs at their boundaries. Application of the so-called consistency relations demonstrates that the model is indeed carrying a field of high-frequency IWs. Being able to simulate a fuller IW spectrum demonstrates that one may be able to use these models to improve the understanding of IW-driven processes and energy pathways. [ABSTRACT FROM AUTHOR]

A model devised by Thorpe & Li (J. Fluid Mech., vol. 758, 2014, pp. 94–120) that predicts the conditions in which stationary turbulent hydraulic jumps can occur in the flow of a continuously stratified layer over a horizontal rigid bottom is applied to, and its results compared with, observations made at several locations in the ocean. The model identifies two positions in the Samoan Passage at which hydraulic jumps should occur and where changes in the structure of the flow are indeed observed. The model predicts the amplitude of changes and the observed mode 2 form of the transitions. The predicted dissipation of turbulent kinetic energy is also consistent with observations. One location provides a particularly well-defined example of a persistent hydraulic jump. It takes the form of a 390 m thick and 3.7 km long mixing layer with frequent density inversions separated from the seabed by some 200 m of relatively rapidly moving dense water, thus revealing the previously unknown structure of an internal hydraulic jump in the deep ocean. Predictions in the Red Sea Outflow in the Gulf of Aden are relatively uncertain. Available data, and the model predictions, do not provide strong support for the existence of hydraulic jumps. In the Mediterranean Outflow, however, both model and data indicate the presence of a hydraulic jump. [ABSTRACT FROM AUTHOR]

Global maps of the mesoscale eddy available potential energy (EAPE) field at a depth of 500 m are created using potential density anomalies in a high-resolution 1/12.5° global ocean model. Maps made from both a free-running simulation and a data-assimilative reanalysis of the HYbrid Coordinate Ocean Model (HYCOM) are compared with maps made by other researchers from density anomalies in Argo profiles. The HYCOM and Argo maps display similar features, especially in the dominance of western boundary currents. The reanalysis maps match the Argo maps more closely, demonstrating the added value of data assimilation. Global averages of the simulation, reanalysis, and Argo EAPE all agree to within about 10%. The model and Argo EAPE fields are compared to EAPE computed from temperature anomalies in a data set of 'moored historical observations' (MHO) in conjunction with buoyancy frequencies computed from a global climatology. The MHO data set allows for an estimate of the EAPE in high-frequency motions that is aliased into the Argo EAPE values. At MHO locations, 15-32% of the EAPE in the Argo estimates is due to aliased motions having periods of 10 days or less. Spatial averages of EAPE in HYCOM, Argo, and MHO data agree to within 50% at MHO locations, with both model estimates lying within error bars observations. Analysis of the EAPE field in an idealized model, in conjunction with published theory, suggests that much of the scatter seen in comparisons of different EAPE estimates is to be expected given the chaotic, unpredictable nature of mesoscale eddies. [ABSTRACT FROM AUTHOR]

Submarine canyons are common features of the coastal ocean. Although they are known to be hotspots of turbulence that enhance diapycnal transport in their stratified waters, the dynamics of canyon mixing processes are poorly understood. Most studies of internal wave dynamics within canyons have focused on a handful of canyons with along-axis slopes less steep than semidiurnal (D2) internal wave characteristics (subcritical). Here, we present the first tidally resolving observations within a canyon with a steeply sloping axis (supercritical). A process study consisting of two 24 h shipboard stations and a profiling mooring was conducted in the La Jolla Canyon off the coast of La Jolla, CA. Baroclinic energy flux is oriented up-canyon and decreases from 182 ±18 W m−1 at the canyon mouth to [ABSTRACT FROM AUTHOR]

Observational evidence is presented for transfer of energy from the internal tide to near-inertial motions near 29°N in the Pacific Ocean. The transfer is accomplished via parametric subharmonic instability (PSI), which involves interaction between a primary wave (the internal tide in this case) and two smaller-scale waves of nearly half the frequency. The internal tide at this location is a complex superposition of a low-mode waves propagating north from Hawaii and higher-mode waves generated at local seamounts, making application of PSI theory challenging. Nevertheless, a statistically significant phase locking is documented between the internal tide and upward- and downward-propagating near-inertial waves. The phase between those three waves is consistent with that expected from PSI theory. Calculated energy transfer rates from the tide to near-inertial motions are modest, consistent with local dissipation rate estimates. The conclusion is that while PSI does befall the tide near a critical latitude of 29°N, it does not do so catastrophically. [ABSTRACT FROM AUTHOR]

Turbulent mixing rates are inferred from measurements spanning 25°-37°N in the Pacific Ocean. The observations were made as part of the Internal Waves Across the Pacific experiment, designed to investigate the long-range fate of the low-mode internal tide propagating north from Hawaii. Previous and companion results argue that, near a critical latitude of 29°N, the internal tide loses energy to high-mode near-inertial motions through parametric subharmonic instability. Here, the authors estimate mixing from several variations of the finescale shear-strain parameterization, as well as Thorpe-scale analysis of overturns. Though all estimated diffusivities are modest in magnitude, average diffusivity in the top kilometer shows a factor of 2-4 elevation near and equatorward of 29°N. However, given intrinsic uncertainty and the strong temporal variability of diffusivity observed in long mooring records, the meridional mixing pattern is found to be near the edge of statistical significance. [ABSTRACT FROM AUTHOR]

Four instances of persistent intrusive deformation of the North Pacific Subtropical Front were tagged individually by a Lagrangian float and tracked for several days. Each feature was mapped in three dimensions using repeat towed observations referenced to the float. Isohaline surface deformations in the frontal zone included sheetlike folds elongated in the alongfront direction and narrow tongues extending across the front. All deformations appeared as protrusions of relatively cold, and fresh, water across the front. No corresponding features of the opposite sign or isolated lenslike structures were observed. The sheets were O(10 m) thick, protruded about 10 km into the warm saline side of the front, and were coherent for 10–30 km along the front. Having about the same thickness and cross-frontal extent as the sheets, tongues extended less than 5 km along the front. All of the intrusions persisted as long as they were followed, several days to one week. Their structures evolved on both inertial (23 h) and subinertial (∼10 days) time scales in response to differential lateral advection. The water mass surrounding the intrusions participated in gradual anticyclonic rotation as a part of a mesoscale meander of the subtropical front. The intrusions may be interpreted as a manifestation of three-dimensional submesoscale turbulence of the frontal zone, driven by the mesoscale. Absence of large features of the opposite sign may be indicative of the asymmetry of the underlying dynamics. [ABSTRACT FROM AUTHOR]

A depth-cycling towed conductivity–temperature–depth (CTD) and vessel-mounted acoustic Doppler current profiler (ADCP) were used to obtain four-dimensional measurements of the restratification of the surface mixed layer (SML) at a submesoscale lateral density gradient near the subtropical front. With the objective of studying the role of horizontal processes in restratification, the thermohaline and velocity fields were monitored for 33 h by 16 small-scale (≤15 km2) surveys centered on a drogued float. Daytime warming by insolation caused a unidirectional displacement of the initially vertical isopycnals toward increasing density. Across the entire SML (50-m vertical scale), solar insolation accounted for 60% of observed restratification, but over 10-m scales, the percentage decreased with depth from 80% at 25–35 m to ≤25% at 55–65 m. Below 35 m, stratification was enhanced by the vertically sheared horizontal advection of the lateral density gradient due to a near-inertial wave of ∼100-m vertical wavelength that rotated anticyclonically at the inertial frequency. The phase and similar period (25.4 h) of the local inertial period to the diurnal cycle ensured constructive interference with isopycnal displacements due to insolation. Restratification by sheared advection matched that predicted due to vertically sheared inertial oscillations generated during the geostrophic adjustment of a density front, but direct wind forcing may also have generated the wave that was subsequently modified by interaction with mesoscale vorticity associated with a nearby large-scale front. By further including the effects of lateral uncompensated thermohaline inhomogeneity, the authors can account for 100% ± 20% of the observed N 2 during daytime restratification. No detectable restratification due to the slumping of horizontal density gradients under gravity alone was found. [ABSTRACT FROM AUTHOR]

The structural formulae in the literature are usually applicable only to a narrow range of the many and complex fabric types available commercially. The scope of such formulae, which are usually based on some simple geometrical model, can be appreciably extended if the formulae are used for making comparisons of fabric parameters in terms of ratios rather than for calculating absolute constructions from basic parameters. This technique is considered particularly suitable for the establishment of minimum specifications for quality control of fabric performance. [ABSTRACT FROM AUTHOR]

The article reports on tricel's properties, manufacturing, development, and end-uses. The cellulose is formed from repeat units known as cellobiose residues which contains two linked glucose residues. Once chemical reactions are excluded and the three hydroxyl groups are fully substituted by acetyl groups, the cellulose triacetate is formed. An average of estimated two and half acetyl groups per glucose residue is the contain of the commercial acetone-soluble secondary acetate, thus it does not have a unique chemical composition.

The article discusses the paper about the structure ratio, E, and its application in fabrics, which was presented in the Diamond Jubilee Conference of the Textile Institute. Structure ratio, E, is a ratio of stitch length and the geometrical mean length of the two sides of the unit pattern cell enclosing the stitch. The geometrical nature of E is significant in the knitted structures of locknit fabrics. Likewise, two theoretical models were presented representing the two states of fabric, relaxation and stretch.