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This paper develops and applies a numerical optimization procedure to compute broadband noise-adaptive weights for delay and sum beamforming that are conditioned to maximize the deflection coefficient at the output of a square law detector for a given set of underwater pressure measurements. The resulting optimal weights mitigate the effects of noise and interferers and maximize signal detection. Comparison of the optimal weights with minimum variance distortionless response weights show that the presented algorithm provides higher attenuation of interferers. We also use the noise-adaptive algorithm to find the optimal sparse array geometry for a given number of sensors and aperture. Comparison of the resulting optimal array with coprime, nested, and semi-coprime arrays shows that the proposed sparse array suppresses interferers more than the other sparse arrays.

Surface morphology is known to affect catalytic activity, as some surfaces show greater activity than others. One of the key challenges is to identify strategies to enhance the expression of such s...

Noise from a tactical aircraft can impact operations due to concerns regarding military personnel noise exposure and community annoyance and disturbance. The efficacy of mission planning can increase when the distinct, complex acoustic source mechanisms creating the noise are better understood. For each type of noise, equivalent acoustic source distributions are obtained from a tied-down F-35B operating at various engine conditions using the hybrid method for acoustic source imaging of Padois, Gauthier, and Berry [J. Sound Vib. 333, 6858-6868 (2014)]. The source distributions for the distinct noise types are obtained using different sections of a 71 element, ground-based linear array. Using a subarray close to the nozzle exit plane, source distributions are obtained for fine-scale turbulent mixing noise and broadband shock-associated noise, although grating lobes complicate interpretations at higher frequencies. Results for a subarray spanning the maximum sound region show that the multiple frequency peaks in tactical aircraft noise appear to originate from overlapping source regions. The observation of overlapping spatial extent of competing noise sources is supported by the coherence properties of the source distributions for the different subarrays.

Cerium dioxide CeO2 (ceria) is an important material in catalysis and energy applications. The intrinsic Frenkel and Schottky defects can impact a wide range of material properties including the oxygen storage capacity, the redox cycle, and the ionic and thermal transport. Here, we study the impact of Frenkel and Schottky defects on the structural dynamics and thermal properties of ceria using density functional theory. The phonon contributions to the free energy are found to reduce the defect formation free energies at elevated temperature. The phonon dispersions of defective CeO2 show significant broadening of the main branches compared to stoichiometric ceria. Phonon modes associated with the defects are identifiable in the infrared spectra through characteristic shoulders on the main features of the stoichiometric fluorite structure. Finally, the presence of Frenkel and Schottky defects are also found to reduce the thermal conductivity by up to 88% compared to stoichiometric CeO2.

Thorium dioxide (ThO²) is a promising alternative to mixed-oxide nuclear fuels due to its longer fuel cycle and resistance to proliferation. Understanding the thermal properties, in particular the thermal conductivity, under reactor conditions is critical to the success of any candidate fuel material. ThO2 has a higher thermal conductivity and thus a lower operating temperature than other fuel systems. However, the presence of defects in real materials directly influencesthe structural dynamics and physical properties, and the impact of defects on the properties of ThO2 are largely unexplored. We have employed densityfunctional theory calculations to study the structure and energetics of the intrinsic Schottky and Frenkel defects in ThO2 and their impact on the thermophysical properties. We identify the anion Frenkel defect to be the most stable, and we identify characteristic spectral signatures of the defects in the phonon dispersions and infrared spectra. We further employ two approximate models developed in previous work to assess the impact of the defects on the thermal transport and find that both types of defect are predicted significantly to reduce the thermal conductivity. The methodology we present facilitates prediction of thethermophysical and transport properties of defective materials at an atomistic level, and should be readily transferrable to other existing and in-development nuclear fuel systems.Keywords: nuclear fuels, thorium dioxide, defect chemistry, defect energetics, structural dynamics, phonon spectra, thermal transport

Radiolytic corrosion of actinide materials represent an issue for the long term storage and disposal of nuclear materials. Molecular species adsorbed at the surface of the actinides may impact the rate of radiolysis, and as the surfaces corrode, the soluble toxic and radioactive species leach into groundwater. It is therefore critical to characterise the surface composition of actinides. Here, we employ ab initio modelling to determine the surface composition of PuO2 with respect to adsorbed CO2. We found that CO2 interacts strongly with the surface forming carbonate species. By mapping the energetics of this interaction, we then calculate the temperature of desorption, finding that surface morphology has a strong impact on the adsorption of CO2, with the {100} being the most and the {111} the least affected by carbonation. Finally, we predict the effect of carbonation on the morphology of PuO2 nanoparticles as a function of temperature and pressure, finding that truncated octahedral is the preferred morphology. This modelling strategy helps characterise surface compensition and nanoparticle morphology, and we discuss the implication for radiolytically driven dispersal of material into the environment.

The presence of cubic PuH2 and PuH3, the products of hydrogen corrosion of Pu, during long-term storage is of concern because of the materials’ pyrophoricity and ability to catalyse the oxidation reaction of Pu to form PuO2. Here, we modelled cubic PuH2 and PuH3 using Density Functional Theory (DFT) and assessed the performance of the PBEsol+U+SOC (0 ≤ U ≤ 7 eV) including van der Waals dispersion using the Grimme D3 method and the hybrid HSE06sol+SOC. We investigated the structural, magnetic and electronic properties of the cubic hydride phases. We considered spin–orbit coupling (SOC) and non-collinear magnetism to study ferromagnetic (FM), longitudinal and transverse antiferromagnetic (AFM) orders aligned in the , and directions. The hybrid DFT confirmed that FM orders in the and directions were the most stable for cubic PuH2 and PuH3, respectively. For the standard DFT, the most stable magnetic order is dependent on the value of U used, with transitions in the magnetic order at higher U values (U > 5 eV) seen for both PuH2 and PuH3.

NASA will soon fly the X-59 aircraft over selected communities to evaluate community responses to shaped sonic booms. Community tests will include dozens of deployed acoustic sensors capable of measuring and detecting shaped sonic boom waveforms in situ for rapid onboard analysis. To this end, we present a sonic boom detector and classifier. The sonic boom detector identifies a shaped sonic boom within a measured acoustical waveform by calculating the cross-correlation with a template shaped sonic boom waveform. The sonic boom classifier determines whether the identified event is indeed a shaped sonic boom based on the correlation coefficient and the calculated noise exposure level. We evaluate these algorithms using simulations of on- and off-design X-59 sonic boom waveforms injected into previously measured 30 s ambient noise recordings. Results of this case study indicate that the detector identifies a sonic boom with an accuracy of ±100 ms in 99.98% of the cases. Furthermore, for a given 30 s measurement, the classifier shows true-positive rates of approximately 0.9999 when the false-positive rate is 10−3. The case study demonstrates that the recommended onboard sonic boom detector and classifier should be highly capable of identifying shaped sonic booms.

Crackle is a sound quality that can be identified in the jet noise of tactical aircraft and may contribute to perceived community noise levels in the vicinity of military airports. Crackle has been linked to the skewness of the waveform pressure derivative, or derivative skewness. Recently, listener trials quantified the perceptual relationships between derivative skewness, loudness, and annoyance. We present a method to calculate a crackle-based adjustment to aircraft noise levels derived from annoyance. This crackle adjustment is applied to a large sample set of community noise measurements in the vicinity of departing military aircraft. Finally, we develop an empirical model to apply crackle-based adjustments to community noise models of tactical aircraft departures. The empirical model allows airport planners to examine how aircraft flight paths, altitudes, and engine conditions affect the crackle adjustment, which is significant in the airport's immediate vicinity and along the aircraft departure path. [Work funded by an AFRL SBIR.]

Generalization of movements from experienced to novel situations is a critical aspect of motor learning. It has been demonstrated that the training period when a movement is learned influences the movement’s generalization to untrained situations. However, little is known about how healthy aging affects these processes. For example, young adults exhibit greater generalization of movements learned on a device (e.g. split-belt treadmill or robotic arm) to movements without it (e.g, overground walking or unconstrained reaching) when participants experience small vs. large perturbations on the training device. Here, we investigated whether a similar effect would be observed in older adults. To this end, we compared the generalization of split-belt adaptation to overground walking in older (75.9±4.8 years old) and young adults (24.7±5.9 years old) when adapted gradually (i.e., small perturbations) vs. abruptly (i.e., large perturbations). We found that both age groups adapted more to the abrupt condition compared to the gradual condition, which resulted in greater adaptation effects (i.e., aftereffects) on the treadmill in the abrupt than the gradual groups. We also found that older adults generalize more than young adults, regardless of the perturbation schedule (i.e., gradual or abrupt). Our results suggest that abrupt perturbations during adaptation do not limit the generalization of movement in older adults-perhaps because they are more likely to attribute them to their own faulty movements. These results suggest that large perturbations are better than small when training older clinical populations since abrupt disturbances would lead to more adaptation and generalization of corrected movements in older people.

Many nanoparticles show enhanced catalytic activity on particular surfaces. Hence, a key challenge is to identify strategies to control the expression of such surfaces and to avoid their disappearance over time. Here, we use density functional theory to explore the adsorption of carbon dioxide on the surfaces of Cerium oxide (CeO2), and its relationship with the resulting nanoparticle morphology under conditions of pressure and temperature. CeO2 is an important solid electrolyte in fuel cells, a catalyst, and enzyme mimetic agent in biomedicine, and has been shown to interact strongly with CO2. We demonstrate that the adsorption of CO2 as a carbonate ion is energetically favorable on the {111}, {110} and {100} surfaces of CeO2, and that the strength of this interaction is morphology and surface stoichiometry dependent. By predicting the surface stability as a function of temperature and pressure, we built surface phase diagrams and predict the surface dependent desorption temperatures of CO2. These temperatures of desorption follow the order {100} > {110} > {111} and are higher for surfaces containing oxygen vacancies compared to stoichiometric surfaces, indicating that surface oxidation processes can reduce the stability of surface carbonate groups. Finally, we propose a thermodynamic strategy to predict the evolution of nanoparticle morphology in the presence of CO2 as the external conditions of temperature and pressure change. We show that there is a thermodynamic driving force dependent on CO2 adsorption that should be considered when selecting nanoparticle morphologies in catalytic applications.

Radiolytic corrosion of actinide materials represent an issue for the long term storage and disposal of nuclear materials. Molecular species adsorbed at the surface of the actinides may impact the rate of radiolysis, and as the surfaces corrode, the soluble toxic and radioactive species leach into groundwater. It is therefore critical to characterise the surface composition of actinides. Here, we employ ab initio modelling to determine the surface composition of PuO2 with respect to adsorbed CO2. We found that CO2 interacts strongly with the surface forming carbonate species. By mapping the energetics of this interaction, we then calculate the temperature of desorption, finding that surface morphology has a strong impact on the adsorption of CO2, with the {100} being the most and the {111} the least affected by carbonation. Finally, we predict the effect of carbonation on the morphology of PuO2 nanoparticles as a function of temperature and pressure, finding that truncated octahedral is the preferred morphology. This modelling strategy helps characterise surface compensition and nanoparticle morphology, and we discuss the implication for radiolytically driven dispersal of material into the environment.

Many nanoparticles show enhanced catalytic activity on particular surfaces. Hence, a key challenge is to identify strategies to control the expression of such surfaces and to avoid their disappearance over time. Here, we use density functional theory to explore the adsorption of carbon dioxide on the surfaces of Cerium oxide (CeO2), and its relationship with the resulting nanoparticle morphology under conditions of pressure and temperature. CeO2 is an important solid electrolyte in fuel cells, a catalyst, and enzyme mimetic agent in biomedicine, and has been shown to interact strongly with CO2. We demonstrate that the adsorption of CO2 as a carbonate ion is energetically favorable on the {111}, {110} and {100} surfaces of CeO2, and that the strength of this interaction is morphology and surface stoichiometry dependent. By predicting the surface stability as a function of temperature and pressure, we built surface phase diagrams and predict the surface dependent desorption temperatures of CO2. These temperatures of desorption follow the order {100} > {110} > {111} and are higher for surfaces containing oxygen vacancies compared to stoichiometric surfaces, indicating that surface oxidation processes can reduce the stability of surface carbonate groups. Finally, we propose a thermodynamic strategy to predict the evolution of nanoparticle morphology in the presence of CO2 as the external conditions of temperature and pressure change. We show that there is a thermodynamic driving force dependent on CO2 adsorption that should be considered when selecting nanoparticle morphologies in catalytic applications.

This paper reports experiments investigating the reaction of H$_{2}$ with uranium metal-oxide bilayers. The bilayers consist of $\leq$ 100 nm of epitaxial $\alpha$-U (grown on a Nb buffer deposited on sapphire) with a UO$_{2}$ overlayer of thicknesses of between 20 and 80 nm. The oxides were made either by depositing via reactive magnetron sputtering, or allowing the uranium metal to oxidise in air at room temperature. The bilayers were exposed to hydrogen, with sample temperatures between 80 and 200 C, and monitored via in-situ x-ray diffraction and complimentary experiments conducted using Scanning Transmission Electron Microscopy - Electron Energy Loss Spectroscopy (STEM-EELS). Small partial pressures of H$_{2}$ caused rapid consumption of the U metal and lead to changes in the intensity and position of the diffraction peaks from both the UO$_{2}$ overlayers and the U metal. There is an orientational dependence in the rate of U consumption. From changes in the lattice parameter we deduce that hydrogen enters both the oxide and metal layers, contracting the oxide and expanding the metal. The air-grown oxide overlayers appear to hinder the H$_{2}$-reaction up to a threshold dose, but then on heating from 80 to 140 C the consumption is more rapid than for the as-deposited overlayers. STEM-EELS establishes that the U-hydride layer lies at the oxide-metal interface, and that the initial formation is at defects or grain boundaries, and involves the formation of amorphous and/or nanocrystalline UH$_{3}$. This explains why no diffraction peaks from UH$_{3}$ are observed. {\textcopyright British Crown Owned Copyright 2017/AWE}, Comment: Submitted for peer review

RESUMEN: Lobelia villaregalis es una especie endemica de Jalisco, Mexico. Se desconocen las caracteristicas del habitat donde se desarrolla, lo cual limita el establecimiento de estrategias de conservacion, asi como la determinacion de la distribucion potencial de la especie. En este estudio, caracterizamos el suelo y la vegetacion en una canada y un pequeno paredon, donde la planta crece. Encontramos que el suelo en las dos localidades es franco arenoso poco profundo (1.5 cm) y de baja fertilidad en el que establece bajos porcentajes de colonizacion por asociaciones micorrizicas del tipo arbuscular. La comunidad vegetal corresponde al bosque mixto de encino-pino donde la diversidad de la flora asociada consta de 140 taxa incluidos en 102 generos y 44 familias de plantas vasculares. Asteraceae incluye el 32% de los taxa registrados, seguida de Poaceae y Pteridaceae (6% y 5% respectivamente). El estrato herbaceo es el mas diverso, seguido del arboreo y el arbustivo. La composicion de especies y la baja proporcion de especies consideradas como maleza puede indicar que L. villaregalis prefiere habitats en buen estado de conservacion. Palabras clave: Lobelia , La Primavera, areas protegidas, micorrizas, conservacion.

Application of phased-array algorithms to acoustic measurements in the vicinity of a high-performance military aircraft yields equivalent source reconstructions over a range of engine conditions. Beamforming techniques for aeroacoustics applications have undergone significant advances over the past decade to account for difficulties that arise when traditional methods are applied to distributed sources such as those found in jet noise. The hybrid method, an inverse method approached via beamforming, is applied to jet noise measured along a 50 element, 30 m linear array to obtain equivalent source distributions. The source distribution extent decreases with increasing frequency or with a decrease in engine condition. A source coherence analysis along the axial dimension of the jet plume reveals that the source coherence lengths scale inversely with increasing engine condition. In addition, a method for extending the array bandwidth to frequencies beyond the spatial Nyquist frequency limit is also implemented. A directivity analysis of the beamforming results reveals that sources near the nozzle radiate to the sideline from a relatively stationary point irrespective of frequency, while the noise source origin of downstream radiating noise varies significantly with frequency.

A method is presented to suppress grating lobes in beamforming using phase unwrapping and array interpolation. When the phase of each cross spectrum is successfully unwrapped, the magnitude and phase of the cross spectral matrix may be interpolated; for cases where these quantities vary smoothly, interpolation is straightforward, even above the spatial Nyquist frequency. Two applications are presented: localization of a broadband source and characterization of a source with frequency-dependent location. In both cases, grating lobes are suppressed and the source is localized at frequencies up to at least 8 times the spatial Nyquist frequency.

Unmanned underwater vehicles (UUVs) are becoming more prevalent in industrial and scientific applications. A wide range of designs is available and many platforms are highly configurable, resulting in an ever-changing acoustic profile. Changes in the UUV’s noise may affect onboard sensors and potentially disturb the environment. An acoustic source imaging process is under development to provide a detailed analysis of the UUV noise in a rapid-turnaround environment. Measurements from a hydrophone array in the geometric near field of a UUV may be input to an acoustic inverse method [e.g., generalized inverse beamforming (GINV) or statistically optimized near-field acoustical holography (SONAH)] to spatially separate noise components and ascertain their levels. However, source resolution and accuracy are highly dependent on array design. Results of a recent numerical case study are presented towards the optimization of linear and planar array geometries. The array geometry is iterated and tuned based on the resultant beamwidth, sidelobe levels, and source localization accuracy for a range of octave frequency bands and source locations. The optimization results provide insight into the critical design factors for acoustical imaging techniques, as well as a suitable array geometry for improved UUV acoustic imaging.

Background. After the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Alaska, the incidence of invasive pneumococcal disease (IPD) due to non-vaccine serotypes, particularly serotype 19A, increased. The aim of this study was to describe the molecular epidemiology of IPD due to serotype 19A in Alaska. Methods. IPD data were collected from 1986 to 2010 through population-based laboratory surveillance. Isolates were serotyped by the Quellung reaction and MICs determined by broth microdilution. Genotypes were assessed by multilocus sequence typing. Results. Among 3,294 cases of laboratory-confirmed IPD, 2,926 (89%) isolates were available for serotyping, of which 233 (8%) were serotype 19A. Across all ages, the proportion of IPD caused by serotype 19A increased from 3.5% (63/1823) pre-PCV7 (1986–2000) to 15.4% (170/1103) post-PCV7 (2001–2010) (p

Meaningful use of the autocorrelation in jet noise analysis is examined. The effect of peak frequency on the autocorrelation function width is removed through a temporal scaling prior to making comparisons between measurements or drawing conclusions about source characteristics. In addition, a Hilbert transform-based autocorrelation envelope helps to define consistent characteristic time scales. Application of these processes to correlation functions based on large and fine-scale similarity spectra reveal that the large-scale noise radiation from an F-22A deviates from the similarity spectrum model.

Healthy aging impairs the ability to adapt movements to novel situations and to switch choices according to the context in cognitive tasks, indicating resistance to changes in motor and cognitive behaviors. Here we examined if this lack of “flexibility” in old subjects observed in motor and cognitive domains were related. To this end, we evaluated subjects’ performance in a motor task that required switching walking patterns and its relation to performance in a cognitive switching task. Specifically, a group of old (>73 years old) and young subjects learned a new locomotor pattern on a split-belt treadmill, which drives the legs at different speeds. In both groups, we assessed the ability to disengage the walking pattern learned on the treadmill when walking over ground. Then, we determined if this motor context-specificity was related to subjects’ cognitive ability to switch actions in a set-shift task. Motor and cognitive behaviors were tested twice on separate visits to determine if age-related differences were maintained with exposure. Consistent with previous studies, we found that old adults adapted slower and had deficits in retention. Most importantly, we found that older subjects could not switch locomotor patterns when transitioning across walking contexts. Interestingly, cognitive switching performance was inversely related to subjects’ ability to switch walking patterns. Thus, cognitive mediated switching interfered with locomotor switching. These findings were maintained across testing sessions. Our results suggest that distinct neural substrates mediate motor and cognitive action selection, and that these processes interfere with each other as we age.

Introduction to the 3rd Biennial Conference of the Society for Implementation Research Collaboration: advancing efficient methodologies through team science and community partnerships

In skin care, the axilla is a biologically unique site requiring specialized attention and care. This area of skin is often subject to hair removal techniques, such as shaving and plucking. These procedures damage the skin leading to erythema and dryness in the short term, and in some cases, post-inflammatory hyperpigmentation (PIHP) in the long term. This study will (i) briefly review the biology and unique properties of axillary skin, and (ii) describe the characteristics of the irritation and damage induced by contemporary skin care habits and resolution of these responses by the use of efficacious skin moisturizing technology. With respect to the latter, we propose that there are five groups of compounds, defined according to their mechanism of action, which are particularly relevant to the care of damaged axillary skin.

The bending stiffness in a homogeneous, isotropic, thin plate is experimentally derived from measurements of coincidence angles extracted from supercritical sound transmission versus frequency measurements. A computer controlled turn table rotates a plate sample and a receiver array, placed in the near field of the plate. The array is used to track the transmitted sound through the plate, generated by a far-field stationary source, using beam forming. The array technique enables measurement of plates measuring only one wavelength in width. Two examples are used for proof of concept, including an aluminum plate in air and an alumina plate under water.

High-performance military aircraft noise is created by multiple sound generation mechanisms that need to be understood to guide noise reduction efforts and for adequate sound field predictions. Phased-array methods can be used to produce frequency-dependent equivalent acoustic source models. The Hybrid (beamforming) method [Padois et al., J. Sound Vib. 333 (2014)] is applied to an acoustical measurement along a 71-microphone ground-based array, spanning 32 m, placed in the vicinity of a high-performance military aircraft as the engine was operated at different powers. Application of the Hybrid method to the full-array creates an overall equivalent source model that is sufficient for predicting overall field radiation but fails to separate the different noise sources. Applying the Hybrid method to subarrays separates broadband shock-associated noise from the main radiation lobes of turbulent mixing noise. Results show that the subarray-based equivalent source distributions for the different types of noise originate from overlapping source locations. Further analysis of the subarray-based equivalent noise sources using coherence and directionality from the unwrapped phase of the cross-spectral source reconstructions identifies overlapping, frequency-dependent source regions with characteristics unique to broadband shock-associated noise and turbulent mixing noise. [Work supported by an Air Force Research Laboratory SBIR.]

Conventional acoustic beamforming methods, while powerful for localizing acoustic sources, require an uncorrelated monopole assumption, depend on the input array location, and are unreliable in a complex source environment, such as jet engine noise. The complexities arise from the large, partially correlated, extended source region, the multiple types of noise sources, such as directional and omnidirectional, and partially correlated sources that violate the integral uncorrelated monopole assumption of beamforming. The complexity of these sources requires advanced beamforming methods. The aim of this research is to determine what advanced beamforming methods tell us about complex, full-scale jet noise sources. To learn about these sources, an array spanning the entire length of a jet from an F-35 aircraft is split into multiple subarrays. Application of the beamforming algorithm to a subarray in the maximum sound region localizes the directional sources present in jet noise; a subarray to the side of the engine characterizes more omnidirectional sources; and a subarray farther forward yields the approximate origin of broadband shock-associated noise. Using these advanced beamforming methods, combined with the subarray processing, opens new insights in this complex environment. [Work supported by the Air Force Research Laboratory; data courtesy of F-35 JPO.]Conventional acoustic beamforming methods, while powerful for localizing acoustic sources, require an uncorrelated monopole assumption, depend on the input array location, and are unreliable in a complex source environment, such as jet engine noise. The complexities arise from the large, partially correlated, extended source region, the multiple types of noise sources, such as directional and omnidirectional, and partially correlated sources that violate the integral uncorrelated monopole assumption of beamforming. The complexity of these sources requires advanced beamforming methods. The aim of this research is to determine what advanced beamforming methods tell us about complex, full-scale jet noise sources. To learn about these sources, an array spanning the entire length of a jet from an F-35 aircraft is split into multiple subarrays. Application of the beamforming algorithm to a subarray in the maximum sound region localizes the directional sources present in jet noise; a subarray to the side of the ...

Because jet noise consists of extended, partially correlated sources, a multi-wavepacket model is appropriate to simulate jet noise field levels as well as the appropriate spatial coherence properties within the field. Here, the Hybrid method is used to reconstruct the levels and coherence properties of the source region for multi-wavepacket numerical models. The beamforming source results are then propagated to the acoustic field, where they show good agreement with benchmark levels and coherence lengths. The Hybrid method is further applied to a planar measurement of noise near a high-performance military aircraft, and the beamforming results are propagated to a ground-based microphone array. Sound levels and coherence lengths generated by the beamforming results show good agreement with benchmark measurements over a range of frequencies that contribute significantly to the overall radiation. Results indicate that the multi-wavepacket representation is an improvement over single-wavepacket models, which do not incorporate spatiotemporal features of the radiation.

Mixing noise from a jet engine originates from an extended spatial region downstream of the nozzle and is partially correlated both spatially and temporally. Previously, the coherence properties in the downstream (axial) direction of the sound field of a tethered military aircraft were investigated, resulting in the identification of different spatial regions based on coherence length [B. M. Harker et al., AIAA J. 54, 1551-1566 (2016)]. In this study, a vertical array of microphones to the side of the jet plume is used to obtain the azimuthal coherence of the sound field. Although multipath interference effects and a limited angular aperture make coherence length calculation impossible, information about upper and lower bounds can be extracted. The measured azimuthal coherence as a function of downstream distance and frequency is then compared to that predicted by sound field reconstructions using multisource, statistically optimized near-field acoustical holography (M-SONAH) [A. T. Wall et al., J. Acoust...

The five-segment Space Launch System solid rocket motor was recently tested at Orbital ATK. Far-field acoustical measurements were performed at angles between 80° and 120° relative to the rocket exhaust at a distance of roughly 2500 m from the rocket, approximately 800 nozzle diameters. The angular aperture allows for evaluating spatial variation in acoustic properties and a comparison with similar tests in the past, including the 2015 test of the same rocket motor. Although terrain variations introduce uncertainty, an approximate 10 dB change in level is seen throughout the aperture, consistent with previous studies. In addition, at low frequencies a high degree of correlation is seen. Near the peak radiation direction high levels of derivative skewness indicate significant shock content and crackle. This dataset also presents the opportunity to test a new method for processing acoustic vector intensity. [Thomas et al., JASA 137, 3366-3376 (2015)] Comparison with the traditional method shows an increase ...

The Ce(III) anionic bis(pentalene) sandwich complex K[Ce{C 8H4(SiiPr3-1,4)2} 2] (1) has been prepared by treatment of CeCl3 with K 2[C8H4(SiiPr3-1,4) 2] and crystallographically characterized as its 18-crown-6 complex. Oxidation of 1 with Ag[BPh4] affords the neutral, formally Ce(IV) sandwich complex [Ce{C8H4(SiiPr 3-1,4)2)2] (2), whose molecular structure has also been determined. The electronic structure of 2 has been investigated in detail by a combination of magnetic studies, K-edge XANES measurements, gas-phase photoelectron spectroscopy, and density functional calculations.

This article illustrates the creation of a specialty specific portfolio that can be used by several different residency programs to document resident competence during a given rotation.Three different disciplines (anesthesiology, surgery and medicine) worked together to create a critical care medicine portfolio. We began by reviewing the curriculum requirements for critical care medicine and organized these requirements into the six ACGME core competencies. We then developed learner led exercises in each core competency that were specific to critical care. Each exercise includes assessment of resident knowledge and application, an evaluation of the exercise, a learner self-assessment of skill, and a review of performance by a faculty member. Portfolio entries are highlighted in a multi-disciplinary weekly conference and posted on a critical care web site at our University.Creation of specialty specific portfolio reduces redundancy between disciplines, allows for increased time to be spent on the development of exercises specific to rotation objectives, and aids program directors in the collection of portfolio entries for each resident over the course of a residency.

Full-scale tactical aircraft noise exhibits multiple radiation lobes not seen in laboratoryscale jets. These lobes have different radiation directions yet appear to have similar, overlapping source regions. Near-field acoustical holography (NAH) source reconstructions, in conjunction with partial field decomposition (PFD) methods that produce physically meaningful partial fields, are used in the current work to investigate the nature of these radiation patterns. First, it is shown that the two main radiation lobes are highly incoherent, suggesting independent partial sources. Second, these lobes are isolated as mutually orthogonal partial fields. In this representation, the lobes seem to be generated by independent yet spatially coincident extended partial sources. Source comparisons are made between non-afterburner and afterburner engine powers to investigate whether afterburner combustion produces any sources that are fundamentally different from those of nonafterburner operations. The current results show no qualitative changes occur due to the addition of the afterburner thrust aside from minor variations in source distribution, level, and the nature of the overlap between the multiple lobes.

The influence of oxygen-grown UO 2+ x films on the early (induction, acceleration) stages of the massive uranium–hydrogen reaction has been studied in a non-visual, constant-volume cell. The potential for (i) adsorbed small molecules (e.g., H 2 O) impeding the reaction and (ii) unintended oxide fracture has been reduced. Induction times were determined by pressure fall, while reaction site nucleation rates were determined by post-reaction visual analysis. Oxidation data from this work suggests that under these conditions the reaction exhibits break-away behaviour at ∼6 μg O 2 cm −2 (calculated mean oxide thickness ∼500 A). Hydriding results indicate that the induction time is related to the mean oxide thickness and increases with increase of oxygen consumption up to at least 25 μg O 2 cm −2 (calculated mean oxide thickness ∼2000 A). However, the hydriding induction time, unexpectedly, does not appear to plateau or reduce as the consumption exceeds 6 μg O 2 cm −2 . Results also indicate that, for any given oxide film, the nucleation rate, as calculated from post-reaction visual analysis, increases with exposure time to hydrogen. Also in general, for a fixed consumption of hydrogen per unit area, the thinnest oxide films result in more reaction sites and a higher mean nucleation rate. Conversely, the thickest oxide films result in fewer reaction sites and a lower mean nucleation rate. In a similar manner to the induction time results, the reaction site nucleation rate is influenced by the degree of prior oxidation, both pre- and post-break-away.

This article highlights work underway in three English local authorities to promote effective inter-agency collaboration around the education of looked after children. Insight drawn from these local authorities is used to review previous literature concerning inter-agency collaboration in a variety of contexts. The relevance of previous research to issues concerning the education of looked after children is discussed and key factors associated with effective collaboration are highlighted. Barriers which have served to obstruct joint working and strategies adopted to deal with these are also discussed.

Wavepacket models provide a convenient representation of jet noise source phenomena because of the extended, partially correlated nature of the turbulent mixing noise. When treated as an equivalent source model, they are useful to estimate features of both the radiated noise as well as the source characteristics to assist in jet noise reduction efforts. In this study, advanced cross-beamforming techniques are applied to measurements in the vicinity of a high-performance military aircraft. These results are then decomposed into an azimuthally-averaged multi-wavepacket representation of the data, which can then be treated as an equivalent source. Estimates of the field levels and coherence properties using the equivalent source are compared with measurements, and results from the multi-wavepacket model show good agreement with benchmark measurements over a range of frequencies that contribute significantly to the overall radiation. The capabilities and limitations of the model to estimate field properties a...

This paper documents the views of a sample of 80 children and young people, aged 10–18 years, living in foster and residential care placements in England, regarding their educational experience whilst being looked after. The children were interviewed as part of an ongoing evaluation of the Taking Care of Education project, a development programme designed to facilitate improvements in the education of looked after children, co-ordinated by the National Children's Bureau and funded by the Gatsby Charitable Foundation. Interviews with the sample asked children to assess their current educational progress and identify individuals who supported or hindered their education, as well as the availability of educational support in care placements. Teaching staff were frequently mentioned as providers of support, whilst social workers were often associated with hindering educational progress. Children and young people had access to a range of educational supports in care placements, and these were more widely available in residential settings than in foster care. Children offered a range of pertinent suggestions as to how the educational experience of those in the public care system might be improved.

Objectives: This study measured the extent to which a systematic approach was used to select criteria for audit, and identified problems in using such an approach with potential solutions. Design: A questionnaire survey using the Audit Criteria Questionnaire (ACQ), created, piloted, and validated for the purpose. Possible ACQ scores ranged from 0 to 1, indicating how systematically the criteria had been selected and how usable they were. Setting: A stratified random sample of 10 audit leads in each of 83 randomly selected NHS trusts and all practices in each of 11 randomly selected primary care audit group areas in England and Wales. Participants: Audit leads of ongoing audits in each organisation in which a first data collection had started less than 12 months earlier and a second data collection was not completed. Main outcome measures: ACQ scores, problems identified in the audit criteria selection process, and solutions found. Results: The mean ACQ score from all 83 NHS trusts and the 11 primary care audit groups was 0.52 (range 0.0–0.98). There was no difference between mean ACQ scores for criteria used in audits on clinical (0.51) and non-clinical (0.52) topics. The mean ACQ scores from nationally organised audits (0.59, n=33) was higher than for regional (0.51, n=21), local (0.53, n=77), or individual organisation (0.52, n=335) audits. The mean ACQ score for published audit protocols (0.56) was higher than for locally developed audits (0.49). There was no difference in ACQ scores for audits reported by general practices (0.49, n=83) or NHS trusts (0.53, n=383). Problems in criteria selection included difficulties in coordination of staff to undertake the task, lack of evidence, poor access to literature, poor access to high quality data, lack of time, and lack of motivation. Potential solutions include investment in training, protected time, improved access to literature, support staff and availability of published protocols. Conclusions: Methods of selecting review criteria were often less systematic than is desirable. Published usable audit protocols providing evidence based review criteria with information on their provenance enable appropriate review criteria to be selected, so that changes in practice based on these criteria lead to real improvement in quality rather than merely change. The availability and use of high quality audit protocols would be a valuable contribution to the evolution of clinical governance. The ACQ should be developed into a tool to help in selecting appropriate criteria to increase the effectiveness of audit.

Acoustical measurements were made in the very far field during a recent test firing of the five-segment QM-1 Space Launch System solid rocket motor at Orbital ATK. Data were taken using 6.35 mm and 12.7 mm type-1 microphones at three far-field locations to the sideline and aft of the nozzle at a range of 650-800 nozzle diameters. The experiment setup, including the appreciable terrain changes, is first discussed. Spectral and autocorrelation analyses highlight the variation of the noise with respect to observation angle. In addition, high-frequency spectral characteristics and waveform statistics are evidence of the significant nonlinear propagation over the propagation range. Terrain effects and data stationarity during the firing are discussed. This dataset is compared to measurements of other solid rocket motors at closer and farther ranges, including the GEM-60 and the four-segment Shuttle Reusable Solid Rocket Motor.

Social media is increasingly used to attract the attention of the public to research activities and to promote interest in science worldwide. A concerted effort has been made by the Acoustics Research Group at Brigham Young University to promote acoustics with various methods of enhanced communications. Web page articles were developed with lay-language introductions to the group's research activities, which can be shared directly to social media sites. The group's Facebook page and research Twitter account @BYUAcoustics provide information about current research meetings, publications, and acoustics in the news, which help network with students who may be interested in joining the acoustics program and which keep alumni informed of current events. In addition, local outreach efforts have been expanded through use of social media. A general audience Twitter account @SoundstoAstound has been utilized to connect with students in our descriptive class and K-12 teachers who bring their students to tour our facilities. The overall effectiveness of each system is assessed using webpage statistics, analytics, and perceived success in reaching target audiences. Successes, limitations, and lessons learned are summarized.

Silver carboxylates [Ag(O2CR): R=Me, tBu, 2,4,6-Me3C6H2], fluorocarboxlyates [Ag(O2CRf): Rf=C3F7, C6F13, C7F15] and their phosphine adducts [Ag(O2CR)·nPR3′: R=Me, tBu, 2,4,6-Me3C6H2, R′=Me, Ph, n=2; R=Me, R′=Me, n=3; Ag(O2CRf).2PPh3, Rf=C3F7, C6F13, C7F15] have been synthesised, characterised spectroscopically and used as precursors in the aerosol-assisted chemical vapour deposition of silver films. All the phosphine adducts produced films, though in general PMe3 adducts, proved more successful than PPh3 analogues. The fluoro-carboxylates and their PPh3 adducts all generated silver films, though the growth rate for the adducts was lower. All these latter films showed carbon impurities while fluorine was also evident in most cases. The X-ray structure of AgO2CC3F7·2PPh3 is also reported.

Advanced cross-beamforming methods improve upon traditional beamforming to reconstruct complex source information and to estimate their respective acoustic radiation. Regularization of the cross-beamforming matrix as part of the calculation procedure helps improve method robustness, but differences in implementation impact volume velocity source results and subsequent field predictions. This paper compares the abilities of four regularization-based, cross-beamforming methods: hybrid method, functional beamforming, generalized inverse beamforming, and mapping of acoustic sources (MACS), along with ordinary cross beamforming, in their ability to reproduce source and field characteristics for an extended, partially correlated numerical source that mimics key characteristics of supersonic jet noise radiation. The four methods that rely on regularization significantly outperform cross-beamforming results, yet the effectiveness of each of four methods is dependent on the individual regularization schemes, which...

Beamforming techniques for aeroacoustics applications have undergone significant advances over the past decade to account for difficulties that arise when traditional methods are applied to distributed sources such as those found in jet noise. Nevertheless, successful source reconstructions depend on array geometry and the assumed source model. The application of phased-array algorithms to ground array measurements of a fullscale tactical jet engine at military and afterburner engine conditions yield different source reconstructions. A deconvolution approach for the mapping of acoustic sources (DAMAS) is utilized to remove array effects seen in conventional beamforming and allows for improved interpretation of results. However, the distributed nature of the jet noise source, as well as large correlation lengths at low frequencies, can result in inaccurate source locations and/or amplitudes for both conventional beamforming and DAMAS. Results using DAMASC, an extension of DAMAS, indicate the degree of source correlation within the military aircraft noise. Source reconstructions on the jet centerline for different one-third octave band frequencies confirm the greater source correlation at low frequencies. These preliminary results represent the first implementation of DAMAS-C on full-scale jet noise data.

The reaction between [C8H6][Li(DME)]2 and chlorotrimethylsilane affords the trimethylsilyl-substituted dihydropentalene C8H6(SiMe3-1,4)2, which may be deprotonated with nBuLi in dimethoxyethane to give [C8H4(SiMe3-1,4)2][Li(DME)]2; the latter reacts with chlorotrimethylsilane to give C8H4(SiMe3-1,1',4,4')4. Similarly, treatment of [C8H6][Li(DME)]2 with triisopropylsilyl triflate gives C8H6(SiiPr3-1,4)2; deprotonation of the latter with KNH2 in diethyl ether affords [C8H4(SiiPr3-1,4)2][K]2, which has been crystallographically characterized and exhibits a chain structure in the solid state.

Triphenylphosphine adducts of silver β-diketonates [AgL(PPh 3 )] (L=acac, dpm, tfac, hfac, fod) and β-ketoiminates (L=hfacNhex, hfacNchex) have been synthesised and evaluated as precursors for the deposition of silver films using aerosol-assisted chemical vapour deposition methodology. The 1:1 stoichiometry of the adducts has been established by 31 P and 109 Ag NMR and a crystal structure of [Ag(hfac)(PPh 3 )]. The best films were obtained from the two β-ketoiminates, particularly L=hfacNhex. While [AgL(PPh 3 )] (L=acac, dpm) gave almost no deposition, the complex with L=tfac gave a film comparable with the two β-ketoiminates while other films showed poor reflectivity (L=hfac, fod).

Recrystallisation of [Ag(C6H4CH2NMe2-2)]41 in the presence of PPh3 has led to the isolation of a silver siloxide, {[Ag(PPh3)]2(µ4-OMe2SiOSiMe2O)}22, from interaction with the silicone grease used to assemble the glassware. Both compounds have been characterised crystallographically, and 2 represents the first structurally characterised silver siloxide. The organometallic is a planar tetramer containing both four- and six-co-ordinate silver. The disiloxide adopts a dimeric ‘step’ structure incorporating trigonal PO2Ag and tetrahedral PO3Ag centres.