Designing the edges of holes (with bias flow) to maximise acoustic damping

Circular holes with a mean bias flow passing through them can amplify or damp acoustic energy and this property is relevant for many industrial applications. In this work, we propose a methodology to design the edges of such holes so that the acoustic damping is maximised. The approach relies on a Bayesian optimisation framework and is illustrated in a short circular hole with a mean laminar bias flow. The acoustic response of the perforation is characterised numerically using a two-step approach where, first, a steady mean flow is computed as the solution of the incompressible Navier–Stokes equations. Second, small-amplitude acoustic perturbations are superimposed on this mean flow and their dynamics are obtained as the solution of the linearised compressible Navier–Stokes equations. Both the upstream and downstream edges of the hole are modified with 45°chamfers. The sizes of these two chamfers are the control parameters optimised to maximise the acoustic absorption coefficient. The results of this letter show that the careful design of the edges can dramatically increase the acoustic energy that holes can damp: the hole investigated here goes from one generating 55% more acoustic energy than incident upon it at a given frequency to one that damps 46% of this acoustic energy

An integrated sequence stratigraphic, palaeoenvironmental, and chronostratigraphic analysis of the Tangahoe Formation, southern Taranaki coast, with implications for mid-Pliocene (c. 3.4–3.0 Ma) glacio-eustatic sea-level changes

Sediments of the mid-Pliocene (c. 3.4–3.0 Ma) Tangahoe Formation exposed in cliffs along the South Taranaki coastline of New Zealand comprise a 270 m thick, cyclothemic shallow-marine succession that has been gently warped into a north to south trending, low angle anticline. This study examines the sedimentologic, faunal, and petrographic characteristics of 10 Milankovitch-scale (6th order), shallow-marine depositional sequences exposed on the western limb of the anticline. The sequences are recognised on the basis of the cyclic vertical stacking of their constituent lithofacies, which are bound by sharp wave cut surfaces produced during transgressive shoreface erosion. Each sequence comprises three parts: (1) a 0.2–2 m thick, deepening upwards, basal suite of reworked bioclastic lag deposits (onlap shellbed) and/or an overlying matrix supported, molluscan shellbed of offshore shelf affinity (backlap shellbed); (2) a 5–20 m thick, gradually shoaling, aggradational siltstone succession; and (3) a 5–10 m thick, strongly progradational, well sorted “forced regressive” shoreline sandstone. The three-fold subdivision corresponds to transgressive, highstand, and regressive systems tracts (TSTs, HSTs, and RSTs) respectively, and represents deposition during a glacio-eustatic sea-level cycle. Lowstand systems tract sediments are not recorded because the outcrop is situated c. 100 km east of the contemporary shelf edge and was subaerially exposed at that time. Well developed, sharp- and gradational-based forced regressive sandstones contain a variety of storm-emplaced sedimentary structures, and represent the rapid and abrupt basinward translation of the shoreline on to a storm dominated, shallow shelf during eustatic sea-level fall. Increased supply of sediment from north-west South Island during “forced regression” is indicated from petrographic analyses of the heavy mineralogy of the sandstones. A chronology based on biostratigraphy and the correlation of a new magnetostratigraphy to the magnetic polarity timescale allows: (1) identification of the Mammoth (C2An.2r) and Kaena (C2An.1r) subchrons; (2) correlation of the coastal section to the Waipipian Stage; and (3) estimation of the age of the coastal section as 3.36–3.06 Ma. Qualitative assessment of foraminiferal census data and molluscan palaeoecology reveals cyclic changes in water depth from shelf to shoreline environments during the deposition of each sequence. Seven major cycles in water depth of between 20 and 50m have been correlated to individual 40 ka glacio-eustatic sea-level cycles on the marine oxygen isotope timescale. The coastal Tangahoe Formation provides a shallow-marine record of global glacio-eustasy prior to the development of significant ice sheets on Northern Hemisphere continents, and supports evidence from marine δ18O archives that changes in Antarctic ice volume were occurring during the Pliocene

Variation of Acoustic Energy Across Sudden Area Expansions Sustaining a Subsonic Flow

The acoustic energy balance of a sudden area expansion is known to be altered in the presence of a mean flow. In this work, Ronneberger’s quasi-steady model describing the acoustic response of a sudden area expansion sustaining a subsonic mean flow of arbitrary Mach number is revisited using the acoustic absorption coefficient, shown to be a function of the inlet Mach number Mu, cross-sectional area ratio θ, and upstream acoustic reflection coefficient Ru. These analytical predictions are tested using a two-step numerical strategy, whereby the mean flow variables are obtained using Reynolds-averaged Navier–Stokes simulations and the fluctuating variables are computed using in-house linearized Navier–Stokes equations solvers. The agreement between the analytical model and the numerical results is found to be excellent for all geometries, mean flows, and acoustic boundary conditions investigated. The generation of acoustic energy by the flow expansion is observed analytically and numerically for high-Mach-number flows undergoing a slight sudden area increase for given acoustic boundary conditions. Conversely, it is found that substantial acoustic energy damping occurs across sudden area expansions characterized by a wide range of parameters (Mu,θ,Ru). Moreover, entropy and vorticity fluctuations are found to be generated at the sudden area expansion, but entropy fluctuations are shown to have a negligible impact on the acoustic response of the area expansion at low and intermediate Mach numbers. Finally, the analytical model is found to be reasonably accurate up to Helmholtz numbers He∼0.05–0.1, corresponding to the frequency range of many industrial applications

Petrogenesis of diachronous mixed siliciclastic-carbonate megafacies in the cool-water Oligocene Tikorangi Formation, Taranaki Basin, New Zealand

The Oligocene (Whaingaroan-Waitakian) Tikorangi Formation is a totally subsurface, lithostratigraphically complex, mixed siliciclastic-limestone-rich sequence forming an important fracture reservoir within Taranaki Basin, New Zealand. Petrographically the formation comprises a spectrum of interbedded rock types ranging from calcareous mudstone to wackestone to packstone to clean sparry grainstone. Skeletal and textural varieties within these rock types have aided in the identification of three environmentally distinctive megafacies for the Tikorangi Formation rocks-shelfal, foredeep, and basinal. Data from these megafacies have been used to detail previous conclusions on the petrogenesis and to further refine depositional paleoenvironmental models for the Tikorangi Formation in the central eastern Taranaki Basin margin.Shelfal Megafacies 1 rocks (reference well Hu Road-1A) are latest Oligocene (early Waitakian) in age and formed on or proximal to the Patea-Tongaporutu-Herangi basement high. They are characterised by coarse, skeletal-rich, pure sparry grainstone comprising shallow water, high energy taxa (bryozoans, barnacles, red algae) and admixtures of coarse well-rounded lithic sand derived from Mesozoic basement greywacke. This facies type has previously gone unrecorded in the Tikorangi Formation. Megafacies 2 is a latest Oligocene (early Waitakian) foredeep megafacies (formerly named shelfal facies) formed immediately basinward and west of the shelfal basement platform. It accumulated relatively rapidly (>20 cm/ka) from redeposition of shelfal megafacies biota that became intermixed with bathyal taxa to produce a spectrum of typically mudstone through to sparry grainstone. The resulting skeletal mix (bivalve, echinoderm, planktic and benthic foraminiferal, red algal, bryozoan, nannofossil) is unlike that in any of the age-equivalent limestone units in neighbouring onland King Country Basin. Megafacies 3 is an Oligocene (Whaingaroan-Waitakian) offshore basinal megafacies (formerly termed bathyal facies) of planktic foraminiferal-nannofossil-siliciclastic wackestone and mudstone formed away from redepositional influences. The siliciclastic input in this distal basinal setting (sedimentation rates <7 mm/ka) was probably sourced mainly from oceanic currents carrying suspended sediment from South Island provenances exposed at this time.Tikorangi Formation rocks record the Taranaki Basin’s only period of carbonate-dominated sedimentation across a full range of shelfal, foredeep, and basinal settings. Depositional controls on the three contrasting megafacies were fundamentally the interplay of an evolving and complex plate tectonic setting, including development of a carbonate foredeep, changes in relative sea level within an overall transgressive regime, and changing availability, sources, and modes of deposition of both bioclastic and siliciclastic sediments. The mixed siliciclastic-carbonate nature of the formation, and its skeletal assemblages, low-Mg calcite mineralogy, and delayed deep burial diagenetic history, are features consistent with formation in temperate-latitude cool waters

On the scattering of entropy waves at sudden area expansions

In this work, we investigate both numerically and theoretically the sound generated by entropy waves passing through sudden area expansions. This is a canonical configuration representing internal flows with flow separation and stagnation pressure losses. The numerical approach is based on a triple decomposition of the flow variables into a steady mean, a small-amplitude coherent part, and a stochastic turbulent part. The coherent part contains acoustic, vortical, and entropy waves. The mean flow is obtained as the solution of the Reynolds-Averaged Navier–Stokes (RANS) equations. The equations governing the coherent perturbations are linearised and solved in the frequency domain. To account for the effect of turbulence on the coherent perturbations, a frozen eddy viscosity model is employed. When entropy fluctuations pass through the area expansion, the generated entropy noise behaves as a low-pass filter. The numerical predictions of the noise at low frequencies are compared to the predictions of compact, quasi-one-dimensional, and isentropic theory and large discrepancies are observed. An alternative model for the generated entropy noise tailored for area expansions is then proposed. Such model is based on the conservation of mass, momentum, and energy written in integral form. The model assumes zero frequency and the one-dimensionality of the flow variables far upstream and downstream of the expansion. The predictions of this model agree well with the numerical simulations across a range of finite subsonic Mach numbers including low, intermediate, and high Mach numbers. The contributions of this work are both numerical and theoretical. Numerically, a triple decomposition adapted to high-Mach-number, compressible flows is introduced for the first time in the context of acoustic simulations. From a theoretical point of view, the quasi-steady model proposed here correctly captures the low-frequency entropy noise generated at sudden area expansions, including at high subsonic Mach numbers

The acoustics of short circular holes with reattached bias flow

One of the most important parameters influencing the acoustic response of holes that sustain a low-Mach-number bias flow is their length-to-diameter ratio. For sufficiently short holes, the bias flow is detached within the hole’s length, while in long holes the bias flow reattaches. The acoustic behaviour of each class is different and separate modelling approaches exist in the literature. For many technical applications, however, the length-to-diameter ratio falls in the range , where is not clear if the holes behave acoustically as short or long holes. In this work, the acoustics of such medium holes are explored numerically and analytically. The numerical approach is based on the linearisation of the compressible Navier–Stokes equations (LNSE) around a Reynolds-averaged mean flow. Medium holes are shown to whistle at higher Strouhal numbers than short holes although the mean flow reattaches within them. The underlying physics are further investigated by incorporating selected flow features of the LNSE results into a semi-analytical model accounting for vortex-sound interaction. It is shown that the perturbation field is determined by the three-way coupling of the two vortex sheets shed from the inlet and outlet edges of the hole with the acoustic field. Furthermore, the modelling of the growth of vorticity inside the hole is shown to be crucial to enable whistling in the semi-analytical model

Plasmalemmal Na+/Ca2+ exchanger modulates Ca2+-dependent exocytotic release of glutamate from rat cortical astrocytes

Astroglial excitability operates through increases in Ca2+cyt (cytosolic Ca2+), which can lead to glutamatergic gliotransmission. In parallel fluctuations in astrocytic Na+cyt (cytosolic Na+) control metabolic neuronal-glial signalling, most notably through stimulation of lactate production, which on release from astrocytes can be taken up and utilized by nearby neurons, a process referred to as lactate shuttle. Both gliotransmission and lactate shuttle play a role in modulation of synaptic transmission and plasticity. Consequently, we studied the role of the PMCA (plasma membrane Ca2+-ATPase), NCX (plasma membrane Na+/Ca2+ exchanger) and NKA (Na+/K+-ATPase) in complex and coordinated regulation of Ca2+cyt and Na+cyt in astrocytes at rest and upon mechanical stimulation. Our data support the notion that NKA and PMCA are the major Na+ and Ca2+ extruders in resting astrocytes. Surprisingly, the blockade of NKA or PMCA appeared less important during times of Ca2+ and Na+ cytosolic loads caused by mechanical stimulation. Unexpectedly, NCX in reverse mode appeared as a major contributor to overall Ca2+ and Na+ homoeostasis in astrocytes both at rest and when these glial cells were mechanically stimulated. In addition, NCX facilitated mechanically induced Ca2+-dependent exocytotic release of glutamate from astrocytes. These findings help better understanding of astrocyte-neuron bidirectional signalling at the tripartite synapse and/or microvasculature. We propose that NCX operating in reverse mode could be involved in fast and spatially localized Ca2+-dependent gliotransmission, that would operate in parallel to a slower and more widely distributed gliotransmission pathway that requires metabotropically controlled Ca2+ release from the ER (endoplasmic reticulum)

Injection-Coupling Instabilities in the BKD Combustor: Acoustic Analysis of the Isolated Injectors

Injection coupling is a well-known cause of high-frequency combustion instability in hydrogen/liquid oxygen (H2/LOX) rocket engines. This type of instability is commonly explained by the two-way coupling between the dynamics of the combustion chamber and the injection system. Recent experimental studies of the BKD combustor, however, suggest that the LOX injector could be self-excited and driving the acoustic mode of the combustion chamber. To assess the feasibility of this mechanism, here, we study both experimentally and theoretically the acoustic stability of the LOX injector isolated from the combustion chamber. The experimental study was performed in a water facility mimicking the conditions of a single LOX injector. The water injector was then modeled using an acoustic network analysis, where the transfer matrix of the LOX injector inlet orifice was computed numerically using a linear approach. The analysis successfully predicts the experimental peak in unsteady pressure, revealing that the LOX injector can be self-excited. The instability was found to be driven by the whistling of the orifice at the inlet of the injector coupled with the second longitudinal acoustic mode of the LOX post tube

Textural variations in Neogene pelagic carbonate ooze at DSDP Site 593, southern Tasman Sea, and their paleoceanographic implications

Changes in Neogene sediment texture in pelagic carbonate-rich oozes on the Challenger Plateau, southern Tasman Sea, are used to infer changes in depositional paleocurrent velocities. The most obvious record of textural change is in the mud:sand ratio. Increases in the sand content are inferred to indicate a general up-core trend towards increasing winnowing of sediments resulting from increasing flow velocity of Southern Component Intermediate Water (SCIW), the forerunner of Antarctic Intermediate Water. In particular, the intervals c. 19-14.5 Ma, c. 9.5-8 Ma, and after 5 Ma are suggested to be times of increased SCIW velocity and strong sediment winnowing. Within the mud fraction, the fine silt to coarse clay sizes from 15.6 to 2 µm make the greatest contribution to the sediments and are composed of nannofossil plates. During extreme winnowing events it is the fine silt to very coarse clay material (13-3 µm) within this range that is preferentially removed, suggesting the 10 µm cohesive silt boundary reported for siliciclastic sediments does not apply to calcitic skeletal grains. The winnowed sediment comprises coccolithophore placoliths and spheres, represented by a mode at 4-7 µm. Further support for seafloor winnowing is gained from the presence in Hole 593 of a condensed sedimentary section from c. 18 to 14 Ma where the sand content increases to c. 20% of the bulk sample. Associated with the condensed section is a 6 m thick orange unit representing sediments subjected to particularly oxygen-rich, late early to early middle Miocene SCIW. Together these are inferred to indicate increased SCIW velocity resulting in winnowed sediment associated with faster arrival of oxygen-rich surface water subducted to form SCIW. Glacial development of Antarctica has been recorded from many deep-sea sites, with extreme glacials providing the mechanism to increase watermass flow. Miocene glacial zones Mi1b-Mi6 are identified in an associated oxygen isotope record from Hole 593, and correspond with times of particularly invigorated paleocirculation, bottom winnowing, and sediment textural changes

Quality of Life During Treatment With Chemohormonal Therapy: Analysis of E3805 Chemohormonal Androgen Ablation Randomized Trial in Prostate Cancer

Purpose Chemohormonal therapy with docetaxel and androgen deprivation therapy (ADT+D) for metastatic hormone-sensitive prostate cancer improves overall survival as compared with androgen deprivation therapy (ADT) alone. We compared the quality of life (QOL) between patients with metastatic hormone-sensitive prostate cancer who were treated with ADT+D and those who were treated with ADT alone. Methods Men were randomly assigned to ADT+ D (six cycles) or to ADT alone. QOL was assessed by Functional Assessment of Cancer Therapy-Prostate (FACT-P), FACT-Taxane, Functional Assessment of Chronic Illness Therapy-Fatigue, and the Brief Pain Inventory at baseline and at 3, 6, 9, and 12 months. The Wilcoxon signed rank test was used to examine changes over time. Mixed-effect models compared the QOL between arms at each time point. Results Seven hundred ninety men were randomly assigned (ADT+D [n = 397] and ADT[ n = 393]) and completed FACT-P (90% at baseline, 86% at 3 months, 83% at 6 months, 78% at 9 months, and 77% at 12 months). ADT+D patients reported a statistically significant decline in FACT-P at 3 months (P \u3c .001) but FACT-P did not differ significantly between baseline and 12 months (P = .38). ADT+D FACT-P scores were significantly lower at 3 months (P = .02) but significantly higher at 12 months (P = .04) when compared with ADT FACT-P scores. Differences did not exceed the minimal clinically important difference at any time point. ADT+D patients reported significantly lower Functional Assessment of Chronic Illness Therapy-Fatigue scores at 3 months than did ADT patients (P \u3c .001). Over time, both arms reported significantly poorer FACT-Taxane scores (P \u3c .001) when compared with baseline. Brief Pain Inventory scores were similar between arms. Conclusion Although ADT+D was associated with statistically worse QOL at 3 months, QOL was better at 12 months for ADT+D patients than for ADT patients. Both arms reported a similar minimally changed QOL over time, suggesting that ADT+D is not associated with a greater long-term negative impact on QOL