bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel method of assessing the effectiveness of protective gloves—results from a pilot study
Authors: Creely K.S. , Cherrie J.W.
Published: July 2002

We have devised a novel method for evaluating the effectiveness of protective gloves and have undertaken a small study to assess this approach. Three types of glove were tested in a standardised simulation test with a permethrin-based pesticide. Prewashed cotton gloves were used to collect the samples. One was worn over the protective glove on one hand to measure the potential deposition of pesticide on the hands had the gloves not been worn. A second was placed under the protective glove on the opposite hand to measure the actual deposition of permethrin on the hands when the gloves were worn. This regime was reversed half way through each test in an attempt to prevent bias. Measurable inner glove contamination occurred on 25 out of 30 occasions. Geometric mean protection factors were calculated from the ratio of outer and inner sampling glove contamination, with average protection factors of 470, 200 and 96 being obtained for the two nitrile and PVC gloves, respectively. The PVC gloves were the least effective in preventing inner glove contamination, probably because the glove was thick and fairly inflexible, causing more pesticide to enter the glove around the cuff. Although the tasks were standardised, variability occurred due to worker behaviour and equipment failure. The spray pump failed on five occasions, resulting in higher levels of inner glove contamination and a geometric mean protection factor of 32. On the occasions when the pump worked correctly, the level of protection provided by the gloves rose dramatically with mean protection factors of 220 and 450 being obtained for workers categorised as “messy” and “tidy”, respectively.
Acyl group specificity at the active site of tetrahydridipicolinate N‐succinyltransferase
Authors: Beaman Todd W. , Vogel Kurt W. , Drueckhammer Dale G. , Blanchard John S. , Roderick Steven L.
Published: July 2002

Tetrahydrodipicolinate N‐succinyltransferase (DapD) catalyzes the succinyl‐CoA‐dependent acylation of L‐2‐amino‐6‐oxopimelate to 2‐N‐succinyl‐6‐oxopimelate as part of the succinylase branch of the meso‐diaminopimelate/lysine biosynthetic pathway of bacteria, blue‐green algae, and plants. This pathway provides meso‐diaminopimelate as a building block for cell wall peptidoglycan in most bacteria, and is regarded as a target pathway for antibacterial agents. We have solved the X‐ray crystal structures of DapD in ternary complexes with pimelate/succinyl‐CoA and L‐2‐aminopimelate with the nonreactive cofactor analog, succinamide‐CoA. These structures define the binding conformation of the cofactor succinyl group and its interactions with the enzyme and place its thioester carbonyl carbon in close proximity to the nucleophilic 2‐amino group of the acceptor, in support of a direct attack ternary complex mechanism. The acyl group specificity differences between homologous tetrahydrodipicolinate N‐acetyl‐ and N‐succinyltransferases can be rationalized with reference to at least three amino acids that interact with or give accessible active site volume to the cofactor succinyl group. These residues account at least in part for the substrate specificity that commits metabolic intermediates to either the succinylase or acetylase branches of the meso‐diaminopimelate/lysine biosynthetic pathway.
A real vessel phantom for imaging experimentation
Authors: Dabrowski W. , Dunmore‐Buyze J. , Rankin R. N. , Holdsworth D. W. , Fenster A.
Published: July 2002

Vascular phantoms are used to evaluate imaging techniques such as ultrasound (US), CT, and angiography. They are expected to mimic the vasculature, surrounding tissue, and blood, and therefore must meet specific requirements on the mimicking materials, with respect to x‐ray attenuation and acoustic properties (velocity, attenuation). In the past, researchers have used a variety of vessel models, including walled (typically latex tube) and wall‐less phantoms (obtained by moulding a lumen in a block of agar). These models lacked the exact geometry of human vessels as well as pathologic features such as plaques and calcifications. To overcome these disadvantages, this paper describes a real vessel phantom for US and x‐ray studies. The phantom consists of an agar‐filled acrylic box containing a formaldehyde fixed section of a real human vessel (obtained at autopsy) cannulated onto two acrylic tubes. This phantom was evaluated by comparing the images obtained with x‐ray angiography, CT, and 3‐D B‐mode US. The images show good overall correlation based on the location of the geometrical features within the phantom, such as lumen, plaques, and calcifications. Discrepancies, artifacts, and difficulties were minor, and are discussed. The use of a real vessel, with its natural geometry and pathology, makes this phantom attractive for evaluation of imaging techniques including projection radiography, CT and US, and for extending its use to MR and US based flow studies.
Theoretical study of temperature elevation at muscle/bone interface during ultrasound hyperthermia
Authors: Lin Win‐Li , Liauh Chihng‐Tsung , Chen Yung‐Yaw , Liu Hwa‐Chang , Shieh Ming‐Jium
Published: July 2002

This paper examines the distributions of the SAR (specific absorption rate) ratio and temperature elevation when an ultrasound beam propagates through the interface of muscle and bone. This interface is regarded as a flat boundary to partition the energy of the ultrasound beam, and the analytical solution of temperature distribution is based on the steady‐state bio‐heat transfer equation. The parameters considered are the incident angle of ultrasound beam, the ultrasound frequency, the acoustic attenuation coefficients of refracted longitudinal and shear waves in bone, and the blood perfusion in muscle. The results show that the peak of the SAR ratio is always at the interface of muscle and bone, while the peak of temperature is located in the bone region beyond the interface. A muscle with lower perfusion or a bone with higher acoustic attenuation results in the shifting of the temperature peak closer to the interface. It is more difficult to heat a higher perfused muscle in front of a bone using a lower frequency ultrasound since the temperature elevation for bone relative to muscle is greater.
Time in quantum mechanics
Authors: Hilgevoord Jan
Published: July 2002

Time is often said to play an essentially different role from position in quantum mechanics: whereas position is represented by a Hermitian operator, time is represented by a c-number. This difference is puzzling and has given rise to a vast literature and many efforts at a solution. It is argued that the problem is only apparent and that there is nothing in the formalism of quantum mechanics that forces us to treat position and time differently. The apparent problem is caused by the dominant role point particles play in physics and can be traced back to classical mechanics.
Quantum mechanics of periodic systems
Authors: Garrison John C.
Published: July 2002

The quantum description of a periodic system can be naturally embedded in an auxiliary problem with an extended configuration space. Standard methods applied to the solution of the extended Schrödinger equation yield the results usually obtained by the use of group theory or extensions of Floquet’s theorem. This method is used to prove Bloch’s theorem and to construct a multimode Floquet method for the semiclassical theory of lasers interacting with atoms.
Seismic detection of sonic booms
Authors: Cates Joseph E. , Sturtevant Bradford
Published: July 2002

The pressure signals from a sonic boom will produce a small, but detectable, ground motion. The extensive seismic network in southern California, consisting of over 200 sites covering over 50 000 square kilometers, is used to map primary and secondary sonic boom carpets. Data from the network is used to analyze three supersonic overflights in the western United States. The results are compared to ray-tracing computations using a realistic model of the stratified atmospheric at the time of the measurements. The results show sonic boom ground exposure under the real atmosphere is much larger than previously expected or predicted by ray tracing alone. Finally, seismic observations are used to draw some inferences on the origin of a set of “mystery booms” recorded in 1992–1993 in southern California.
Relative loudness of low- and high-frequency bands of speech-shaped babble, including the influence of bandwidth and input level
Authors: Keidser Gitte , Katsch Richard , Dillon Harvey , Grant Frances
Published: July 2002

In a balancing test, ten normal-hearing listeners adjusted filtered speech-shaped babble-noise to equally loud levels. On average, they selected about 10 dB less gain for bands below 1 kHz than for bands above and including 1 kHz. The findings applied to two bandwidths (octave and equivalent rectangular bandwidth) and two levels (65 and 85 dB SPL). The outcome suggests that hearing aid fitting procedures aiming to equalize loudness of speech bands should prescribe less low-frequency gain than procedures aiming to normalize loudness of speech bands. A significant interaction was found between bandwidth and input level for the high-frequency bands.
Auditory filter nonlinearity in mild/moderate hearing impairment
Authors: Baker Richard J. , Rosen Stuart
Published: July 2002

Sensorineural hearing loss has frequently been shown to result in a loss of frequency selectivity. Less is known about its effects on the level dependence of selectivity that is so prominent a feature of normal hearing. The aim of the present study is to characterize such changes in nonlinearity as manifested in the auditory filter shapes of listeners with mild/moderate hearing impairment. Notched-noise masked thresholds at 2 kHz were measured over a range of stimulus levels in hearing-impaired listeners with losses of 20–50 dB. Growth-of-masking functions for different notch widths are more parallel for hearing-impaired than for normal-hearing listeners, indicating a more linear filter. Level-dependent filter shapes estimated from the data show relatively little change in shape across level. The loss of nonlinearity is also evident in the input/output functions derived from the fitted filter shapes. Reductions in nonlinearity are clearly evident even in a listener with only 20-dB hearing loss.
Characterization of ultrasonic transducers by means of double-exposure holographic interferometry
Authors: Tello Lucio N. , Black Truman D. , Cudmore Don P. , Magnusson Robert
Published: July 2002

Double-exposure holographic interferometry is applied to measure the surface displacements of ultrasonic transducers. Interferograms revealing detail surface displacements are produced using iron-doped lithium niobate crystals as the recording medium. Lead zirconate titanate disks poled in the longitudinal thickness mode possessing deposited, shaped electrodes are examined. Transducers with circular, strip, rectangular, and rosette electrode shapes are investigated. The displacement measurements reveal that the electrode “drags” the rest of the transducer surface. Thus the unmetallized portion of the transducer also contributes to the acoustic field. Pressure field calculations using the experimentally measured displacements are performed. It is shown that proper geometrical design of the electrode yields reduction of the sidelobes in the far field and smoothing of the maxima and minima in the near field, and improved focusing via reduced acoustic beam divergence. Most importantly, this work reveals that the unmetallized portion of the transducer contributes significantly to the displacement and to the resulting pressure fields.
Sound propagation from a dipole source near an impedance plane
Authors: Li Kai Ming , Taherzadeh Shahram , Attenborough Keith
Published: July 2002

A closed-form analytic solution has been derived for an arbitrarily oriented dipole placed above an impedance plane. Asymptotic approximations for the total sound field can be written in a form similar to the classical formula for a monopole. Analytic approximations derived for horizontal and vertical dipoles give predictions that agree well with those obtained from a program of the fast field type. The asymptotic results have been confirmed also by laboratory measurements. Compared with numerical methods, the analytic approximations offer the combined advantages of easier physical interpretation and a much reduced computational time. It is found that the variation of the sound-pressure level from a vertical dipole above an impedance plane differs significantly from that due to a monopole above this plane, particularly as a result of differences in the ground wave component. However, the excess attenuation due to a horizontal dipole is found to be rather similar to that for a monopole except for source and receiver heights that are comparable with range.
Comment on “Modal analysis of a structure in a compressible fluid using a finite element/boundary element approach” [J. Acoust. Soc. Am. 99, 1949–1957 (1996)]
Authors: Pathak Ardhendu G. , Jalihal Purnima
Published: July 2002

An approach to solve for the resonance frequency of fluid-loaded structures was recently suggested by McCollum and Siders [J. Acoust. Soc. Am. 99, 1949–1957 (1996)]. An iterative procedure was suggested to solve for eigenfrequencies by reducing the problem to the standard eigenvalue problem. Using an example of a single degree of freedom system with a piston radiating in fluid, it is shown that the proposed method can lead to incorrect results.
Stoneley wave excitation by a bounded beam at the down-step of a thin layer on a substrate
Authors: Briers R. , Leroy O. , Shkerdin G.
Published: July 2002

The mode conversion of a bulk wave into a Stoneley wave at the downward step of a thin layer partially covering a solid substrate is studied. An analytical expression for the amplitude of the excited Stoneley wave is derived by applying mode theory. The excitation amplitude has two pronounced maxima: at grazing and at Rayleigh angle incidence of the bulk wave. The latter maximum is almost independent of the material characteristics of the thin layer.
A modeling technique for active control design studies with application to spacecraft microvibrations
Authors: Aglietti G. S. , Gabriel S. B. , Langley R. S. , Rogers E.
Published: July 2002

Microvibrations, at frequencies between 1 and 1000 Hz, generated by on board equipment, can propagate throughout a spacecraft structure and affect the performance of sensitive payloads. To investigate strategies to reduce these dynamic disturbances by means of active control systems, realistic yet simple structural models are necessary to represent the dynamics of the electromechanical system. In this paper a modeling technique which meets this requirement is presented, and the resulting mathematical model is used to develop some initial results on active control strategies. Attention is focused on a mass loaded panel subjected to point excitation sources, the objective being to minimize the displacement at an arbitrary output location. Piezoelectric patches acting as sensors and actuators are employed. The equations of motion are derived by using Lagrange’s equation with vibration mode shapes as the Ritz functions. The number of sensors/actuators and their location is variable. The set of equations obtained is then transformed into state variables and some initial controller design studies are undertaken. These are based on standard linear systems optimal control theory where the resulting controller is implemented by a state observer. It is demonstrated that the proposed modeling technique is a feasible realistic basis for in-depth controller design/evaluation studies.
Inversion of bottom/subbottom statistical parameters from acoustic backscatter data
Authors: Turgut Altan
Published: July 2002

Inversion of statistical parameters of a bottom/subbottom scattering model is investigated by using genetic algorithms for both synthetic and real data. The bottom/subbottom scattering model used in the calculations is a modified version of Lyons, Anderson, and Dwan [J. Acoust. Soc. Am. 79, 1410–1422 (1986)] in which correlation between subbottom density, compressibility, and sound-speed fluctuations is established through Wood’s equation [A Textbook of Sound (Macmillan, New York, 1941)], and volume inhomogeneities are described by von Karman type autocorrelation functions [T. von Karman, J. Mar. Res. 7, 252–264 (1948)]. The inversion is posed as an optimization problem which is solved (by a controlled Monte Carlo search using genetic algorithms) to find the optimum set of statistical parameters that minimizes the quadratic deviation between measured and calculated backscatter data. A posteriori probabilities calculated at the end of the search are used for error estimation and indication of relative importance of model parameters. This information helps to further assess the relative importance of two major scattering mechanisms due to bottom roughness and subbottom inhomogeneities. Such assessment is successfully demonstrated by using synthetic and real backscatter data for sandy, silty, and muddy sediments. Finally, inverted statistical parameters for a sandy site at Biscayne Bay, Florida confirm the results of simultaneous tomographic measurements indicating that scattering by subbottom inhomogeneities plays a minor role for this particular site.
Leaky waves and the elastic wave resonance reflection on a crystal-thin solid layer interface. II. Leaky waves given rise to by exceptional bulk waves
Authors: Darinskii A. N.
Published: July 2002

A study is made of the elastic wave resonance reflection in a crystal-thin solid layer structure near the velocity of a leaky wave which originates from an exceptional bulk wave. The latter is a homogeneous mode with group velocity parallel to the boundary of a medium which satisfies the condition of the mechanically free surface. On the surface coated with a thin layer, the exceptional bulk wave can transform into the leaky wave and then there arises a narrow interval of incident angles where the coefficients of mode conversion suffer abrupt and strong variations in phase and magnitude. A criterion of occurence of the leaky wave is found. Approximate expressions describing the behavior of the coefficients of mode conversion within the resonance interval of incident angles are derived and analyzed.
Evaluation of the effect of speech-rate slowing on speech intelligibility in noise using a simulation of cochlear hearing loss
Authors: Nejime Yoshito , Moore Brian C. J.
Published: July 2002

The effect of digital processing, which slows the speed of speech (speech-rate) without changing its pitch, has been examined. The processing is intended to make speech communication easier by allowing more time for cognitive processing when the listening situation is difficult, for example, when listening to a foreign language, or when the user has a hearing loss. The speech-rate slowing makes use of a pitch-synchronous partial expansion of the waveform in the time domain. The processing was evaluated using a simulation of hearing loss which has been shown to lead to reduced intelligibility for normally hearing subjects. The simulation included the major consequences of cochlear hearing loss; loudness recruitment, threshold elevation, and reduced frequency selectivity. Two simulations were used: a moderate flat hearing loss with auditory filters broadened by a constant factor of three (B3R2); and the same loss with linear amplification applied prior to the simulation processing (B3R2+). Two expansion rates were used for the speech-rate slowing, 1.25 and 1.50. The intelligibility of sentences in speech-shaped noise was measured. For both simulation conditions, the speech-rate slowing did not give any improvement in intelligibility. Rather, in condition B3R2+ the slowing produced statistically significant deleterious effects on intelligibility. The results suggest that artificial speech-rate slowing will not improve the intelligibility of speech in noise for hearing-impaired people who have the type of cochlear damage simulated in this test.
Impulse noise metrics and their application to noise from low-flying military jet aircraft
Authors: Kerry G. , Wheeler P. D. , Hempstock T. I. , James D. J.
Published: July 2002

It is recognized that noise from fast low-flying military jet aircraft is a major factor in the public concern over military low-flying training operations. While much research has been carried out worldwide, potential health risks from noise and environmental noise nuisance remain poorly understood. Part of the difficulties arise in quantifying the exposure and in selecting appropriate risk or tolerability criteria. Much depends on the nature of the noise. This review investigates the definitions and characteristics of impulsive noise and the various metrics in current use for assessing both hearing hazards and environmental annoyance and considers their application to noise from low-flying military jets.
Analytical expressions for the envelope correlation of narrow-band stimuli used in CMR and BMLD research
Authors: van de Par Steven , Kohlrausch Armin
Published: July 2002

Analytical solutions are presented for the correlation between the envelopes of certain narrow-band stimuli that are typically used in experiments on binaural unmasking and on Comodulation Masking Release (CMR). These stimuli consist of two maskers with identical envelopes and a signal that is added to one of the maskers. If the two maskers have the same center frequency and are presented to the right and left ear, the stimulus resembles a binaural MoSm condition. If the two maskers have different center frequencies, we have a CMR condition with one flanking band. The solutions for the envelope correlation differ depending on whether the envelope correlation is expressed as normalized cross correlation or as normalized cross covariance (Pearson product-moment correlation). The envelope correlation depends on the statistics of the masker and the signal whereas the waveform correlation depends on neither. This influence only disappears for the normalized envelope cross correlation provided that the masker level is much higher than the signal level. In this case the envelope cross correlation is approximately equal to the square root of the waveform correlation. It is argued that the different properties of both types of envelope correlation are of relevance for CMR research.
Playback of acoustic thermometry of ocean climate (ATOC) -like signal to bony fishes to evaluate phonotaxis
Authors: Klimley A. Peter , Beavers Sallie C.
Published: July 2002

The aim of this study was to evaluate whether acoustic thermometry of ocean climate (ATOC) signals have a positive or negative phonotactic effect on the behavior of fish present near the sound source at Pioneer Seamount off Central California. We played back an ATOC-like signal to three species of rockfish kept within a 15×2-m field enclosure in Bodega Bay, California. Each subject was observed during a 25-min “silent” control period followed immediately by a test period comprised of a 5-min “ramp-up,” in which the sound level increased gradually to a peak level, and a 20-min period at constant peak level. The amount of time that each subject spent in 15 zones, each 1 m wide, at increasing distances from the sound transducer, was observed. It was suspended in midwater at the center of zone 1, the deepest portion of the enclosure. We observed little movement by fish in response to the playback of the ATOC signal. The subjects remained in zones 1 and 2, despite sound pressure levels present of 145.1–153.0 dB re: 1 μPa. Little difference existed in the behavior of fish during sound playback period and the “silent” control period. The median time interval that fishes occupied zone 1 was 100% of the experiment duration for both test and control periods (i.e., 6 of 11 subjects in the former remained exclusively within that zone versus 7 of 11 subjects in the latter).
Thickness vibrations of rotating piezoelectric plates
Authors: Yang J. S. , Fang H. , Jiang Q.
Published: July 2002

Thickness vibrations of a piezoelectric plate rotating at a constant angular velocity about its normal are studied using the equations of linear piezoelectricity. The transcendental equation that determines the resonant frequencies is derived for materials with general anisotropy and solved for specific materials of polarized ceramics and rotated Y-cut quartz. The results are useful in the understanding and analysis of plate piezoelectric gyroscopes.
Frequency and concentration dependence of the backscatter coefficient of the ultrasound contrast agent Albunex®
Authors: Marsh Jon N. , Hughes Michael S. , Hall Christopher S. , Lewis Stephen H. , Trousil Rebecca L. , Brandenburger Gary H. , Levene Harold , Miller James G.
Published: July 2002

A broadband ultrasonic measurement system has been utilized to characterize the concentration and frequency dependence of in vitro suspensions of Albunex® microspheres at concentrations ranging from 1.7×105 to 2.1×107 microspheres/mL and over a bandwidth of 1–16 MHz. The apparent backscattered power (not compensated for effects due to attenuation) was shown to increase with dose for lower concentrations of microspheres, but then to decrease rapidly with increasing concentration where attenuation effects become significant. Measurements of signal loss demonstrated that the attenuation grew exponentially with increasing concentration, so that a doubling of the number of microspheres led to a doubling of the value of the attenuation coefficient measured in dB/cm. This relationship was demonstrated over the entire system bandwidth. Compensation of the apparent backscattered power for the attenuation yielded the backscatter transfer function. This quantity was shown to be linearly proportional to concentration, so that a doubling of the number of microspheres led to a 3-dB increase in the backscatter transfer function. A broadband data reduction technique was used to further reduce the data to backscatter coefficient, an absolute parameter describing the intrinsic scattering efficiency of the Albunex® microsphere suspensions. The backscatter coefficient was shown to be linearly proportional to microsphere concentration at all concentrations investigated and over all the usable bandwidth. This suggests that, with appropriate compensation for attenuation and equipment parameters, perfusion or flow quantification techniques which assume a linear dependence of backscatter with contrast agent concentration should be applicable. The backscatter coefficient exhibits a rapid rise with frequency below 3 MHz, and appears to approach a frequency independent limit above 3 MHz. The relationships of the attenuation coefficient and backscatter transfer function to concentration were generally consistent with predictions from a simple scattering model. These relationships appear to be valid within the usable bandwidth of our measurement system for all concentrations investigated.
Acoustical imaging through a multiple scattering medium using a time-reversal mirror
Authors: Roux Philippe , Derode Arnaud , Peyre Aymeric , Tourin Arnaud , Fink Mathias
Published: July 2002

Acoustical imaging is based on the ability to focus an acoustic beam inside the zone of interest. This remains an issue through a high-order multiple scattering medium because the electronic delay lines that enable one to focus through a multiple scattering medium are a priori unknown. Using time-reversal principles, we show that images can be obtained through a very disordered medium. Surprisingly, the images are better than those obtained in a homogeneous medium with a classical imaging device.
Calculation of acoustic radiation using equivalent-sphere methods
Authors: Bouchet Laurent , Loyau Thierry , Hamzaoui Nacer , Boisson Claude
Published: July 2002

Among the methods generally used to solve a problem in the domain of acoustic radiation, the equivalent sources method offers an interesting alternative. It consists in replacing the vibrating surface with a distribution of acoustic sources placed inside the structure. The contribution of each source is determined in such a way that the acoustic field radiated by these sources verifies the same boundary conditions on the structure. The number of unknowns in the problem is no longer directly linked to the number of mesh points on the structure, as with boundary elements methods, but to the number of equivalent sources employed in the model. The equivalent source method is therefore of major interest if the acoustic radiation of the structure can be approximated with a sufficiently low number of sources. This paper proposes its application when the equivalent source is a sphere. In this case, the number of unknowns is equal to the number of modes. In contrast to the one-point multipole, the sphere has a surface surrounding a closed volume to express the boundary conditions. Although sphere/multipole equivalence has been demonstrated, the surface of the sphere allows normalization of the functions used, leading to stabilization of the system to be resolved. First, the main acoustic radiation characteristics of a sphere and of the linear system verified by the modal coefficients of an equivalent sphere are presented. The different parameters of the model are then studied: position and radius of the equivalent sphere, truncation of the series, and influence of the spatial sampling (mesh). In the same vein, a second approach is presented. It consists of making each point of the structure correspond to a point of the sphere, and the vibrating field at the surface of the sphere is deduced from that of the structure by simple geometric projection. Results can be obtained very quickly as no matrix inversion is required. The accuracy of the results depends on the distance between the sphere and the structure. Finally, an experimental validation that uses both methods is presented and shows interesting results when the structure is closed, and when its shape is not too far removed from a sphere.
The Rheology of Inorganic Glasses
Authors: Goldstein Martin
Published: July 2002

The purpose of this review is to inform those whose interests have been primarily in the rheology of organic polymers and simple liquids as to the similarities and differences between the inorganic glasses and these substances. The inorganic glasses act more like molecular liquids than like polymers; although there have been some reports of a yield stress for flow in the high-viscosity range, these have not been widely confirmed, and the best available evidence is that the inorganic glasses are Newtonian liquids under the usual stress levels used to measure viscosity (106–1010dynes/cm2 near, but above, T0). In the transformation range the viscosity is time-dependent as volume (or more generally structural) relaxation occurs. Study of these processes permit two conclusions: a single internal ordering variable is insufficient to describe the state, and the free volume concept for viscosity is inadequate, at least in its original form. Of the various equations for viscosity so far proposed, that due Adam and Gibbs appears to offer the widest range of satisfactory agreement. It is based on a reintroduction of the concept of an activation energy for flow, and in the author's view, such a picture offers the best hope of explaining not only the ordinary rheology of glass but the highly nonlinear and presumably related phenomenona of cold flow in polymers and plasticity in inorganic glasses.
Frailty and Effects of a Multidomain Physical Rehabilitation Intervention Among Older Patients Hospitalized for Acute Heart Failure
Authors: Pandey Ambarish , Kitzman Dalane W. , Nelson M. Benjamin , Pastva Amy M. , Duncan Pamela , Whellan David J. , Mentz Robert J. , Chen Haiying , Upadhya Bharathi , Reeves Gordon R.
Published: January 2023

Importance

Frailty is common among older patients with acute decompensated heart failure (ADHF) and is associated with worse quality of life (QOL) and a higher risk of clinical events. Frailty can also limit recovery and response to interventions. In the Rehabilitation Therapy in Older Acute Heart Failure Patients (REHAB-HF) trial, a 3-month innovative, early, transitional, tailored, multidomain physical rehabilitation intervention improved physical function and QOL (vs usual care) in older patients with ADHF.

Objective

To evaluate whether baseline frailty modified the benefits of the physical rehabilitation intervention among patients with ADHF enrolled in the REHAB-HF trial and to assess the association between changes in frailty with the risk of adverse clinical outcomes on follow-up.

Design, Setting, and Participants

This prespecified secondary analysis of the REHAB-HF trial, a multicenter randomized clinical trial, included 337 patients 60 years and older hospitalized for ADHF. Patients were enrolled from September 17, 2014, through September 19, 2019. Participants were stratified across baseline frailty strata as assessed using modified Fried criteria. Data were analyzed from July 2021 to September 2022.

Interventions

Physical rehabilitation intervention or attention control.

Main Outcomes and Measures

Primary outcome was the Short Physical Performance Battery (SPPB) score at 3 months. Clinical outcomes included all-cause hospitalization or mortality at 6 months.

Results

This prespecified secondary analysis included 337 participants; 181 (53.7%) were female, 167 (49.6%) were Black, and the mean (SD) age was 72 (8) years. A total of 192 (57.0%) were frail and 145 (43.0%) were prefrail at baseline. A significant interaction was observed between baseline frailty status and the treatment arm for the primary trial end point of overall SPPB score, with a 2.6-fold larger improvement in SPPB with intervention among frail patients (2.1; 95% CI, 1.3-2.9) vs prefrail patients (0.8; 95% CI, −0.1 to 1.6; P for interaction = .03). Trends consistently favored a larger intervention effect size, with significant improvement among frail vs prefrail participants for 6-minute walk distance, QOL, and the geriatric depression score, but interactions did not achieve significance.

Conclusions and Relevance

In this prespecified secondary analysis of the REHAB-HF trial, patients with ADHF with worse baseline frailty status had a more significant improvement in physical function in response to an innovative, early, transitional, tailored, multidomain physical rehabilitation intervention than those who were prefrail.

Trial Registration

Clinical Trials.gov Identifier: NCT02196038
Development of a Machine Learning Model for Sonographic Assessment of Gestational Age
Authors: Lee Chace , Willis Angelica , Chen Christina , Sieniek Marcin , Watters Amber , Stetson Bethany , Uddin Akib , Wong Jonny , Pilgrim Rory , Chou Katherine , Tse Daniel , Shetty Shravya , Gomes Ryan G.
Published: January 2023

Importance

Fetal ultrasonography is essential for confirmation of gestational age (GA), and accurate GA assessment is important for providing appropriate care throughout pregnancy and for identifying complications, including fetal growth disorders. Derivation of GA from manual fetal biometry measurements (ie, head, abdomen, and femur) is operator dependent and time-consuming.

Objective

To develop artificial intelligence (AI) models to estimate GA with higher accuracy and reliability, leveraging standard biometry images and fly-to ultrasonography videos.

Design, Setting, and Participants

To improve GA estimates, this diagnostic study used AI to interpret standard plane ultrasonography images and fly-to ultrasonography videos, which are 5- to 10-second videos that can be automatically recorded as part of the standard of care before the still image is captured. Three AI models were developed and validated: (1) an image model using standard plane images, (2) a video model using fly-to videos, and (3) an ensemble model (combining both image and video models). The models were trained and evaluated on data from the Fetal Age Machine Learning Initiative (FAMLI) cohort, which included participants from 2 study sites at Chapel Hill, North Carolina (US), and Lusaka, Zambia. Participants were eligible to be part of this study if they received routine antenatal care at 1 of these sites, were aged 18 years or older, had a viable intrauterine singleton pregnancy, and could provide written consent. They were not eligible if they had known uterine or fetal abnormality, or had any other conditions that would make participation unsafe or complicate interpretation. Data analysis was performed from January to July 2022.

Main Outcomes and Measures

The primary analysis outcome for GA was the mean difference in absolute error between the GA model estimate and the clinical standard estimate, with the ground truth GA extrapolated from the initial GA estimated at an initial examination.

Results

Of the total cohort of 3842 participants, data were calculated for a test set of 404 participants with a mean (SD) age of 28.8 (5.6) years at enrollment. All models were statistically superior to standard fetal biometry–based GA estimates derived from images captured by expert sonographers. The ensemble model had the lowest mean absolute error compared with the clinical standard fetal biometry (mean [SD] difference, −1.51 [3.96] days; 95% CI, −1.90 to −1.10 days). All 3 models outperformed standard biometry by a more substantial margin on fetuses that were predicted to be small for their GA.

Conclusions and Relevance

These findings suggest that AI models have the potential to empower trained operators to estimate GA with higher accuracy.
Social Work Staffing and Use of Palliative Care Among Recently Hospitalized Veterans
Authors: Cornell Portia Y. , Halladay Christopher W. , Montano Anna-Rae , Celardo Caitlin , Chmelka Gina , Silva Jennifer W. , Rudolph James L.
Published: January 2023

Importance

Palliative care improves quality of life for patients and families but may be underused.

Objective

To assess the association of an intervention to increase social work staffing in Veterans Health Administration primary care teams with use of palliative care among veterans with a recent hospitalization.

Design, Setting, and Participants

This cohort study used differences-in-differences analyses of the change in palliative care use associated with implementation of the Social Work Patient Aligned Care Team (PACT) staffing program, conducted from October 1, 2016, to September 30, 2019. The study included 71 VA primary care sites serving rural veterans. Participants were adult veterans who received primary care services from a site enrolled in the program and who received inpatient hospital care. Data were analyzed from January 2020 to August 2022.

Exposures

The PACT staffing program was a clinic-level intervention that provided 3-year seed funding to Veterans Health Administration medical centers to hire 1 or more additional social workers in primary care teams. Staggered timing of the intervention enabled comparison of mean outcomes across sites before and after the intervention.

Main Outcomes and Measures

The primary outcome was the number of individuals per 1000 veterans who had any palliative care use in 30 days after an inpatient hospital stay.

Results

The analytic sample included 43 200 veterans (mean [SD] age, 65.34 [13.95] years; 37 259 [86.25%] men) and a total of 91 675 episodes of inpatient hospital care. Among the total cohort, 8611 veterans (9.39%) were Black, 77 069 veterans (84.07%) were White, and 2679 veterans (2.92%) were another race (including American Indian or Alaskan Native, Asian, and Native Hawaiian or other Pacific Islander). A mean of 14.5 individuals per 1000 veterans (1329 individuals in all) used palliative care after a hospital stay. After the intervention, there was an increase of 15.6 (95% CI, 9.2-22.3) individuals per 1000 veterans using palliative or hospice care after a hospital stay, controlling for national time trends and veteran characteristics—a 2-fold difference relative to the mean.

Conclusions and Relevance

This cohort study found significant increases in use of palliative care for recently hospitalized veterans whose primary care team had additional social work staffing. These findings suggest that social workers may increase access to and/or use of palliative care. Future work should assess the mechanism for this association and whether the increase in palliative care is associated with other health or health care outcomes.
Organization factors influencing quality of work life among seniors’ care workers with severe low back pain
Authors: Iwakiri Kazuyuki , Sotoyama Midori , Takahashi Masaya , Liu Xinxin
Published: January 2023

Objectives

The prevalence of work-related low back pain (LBP) is high among care workers and can negatively affect quality of work life (QWL). To improve workplace satisfaction, this study aimed to identify factors influencing QWL among seniors’ care workers with severe LBP.

Methods

A questionnaire survey including items on demographics, qualifications, basic job responsibilities, job stressors, LBP severity, QWL, and job satisfaction was conducted in 2018. In total, 1000 senior care facilities were selected via random sampling and eight care workers per institution were asked to complete the survey. Multiple logistic regression analysis was used to identify independent factors influencing QWL of care workers with and without severe LBP.

Results

Data from 1247 care workers with severe LBP and 2009 with nonsevere LBP were included in the analysis. Overall QWL was lower in the severe LBP group than in the nonsevere LBP group. In both groups, human relationships, workplace support, discretionary responsibility level, and working hours or time off were identified as common factors influencing QWL. In the severe LBP group, the salary was also a significant influence on QWL, while in the nonsevere LBP group, the number of workers, promotion or official position, and caregiving technique were identified as significant QWL factors.

Conclusions

The QWL of care workers with severe LBP was strongly influenced by salary. Since care workers suffering from severe LBP are working for a salary while enduring the pain and do not have found a worth doing, they need to prevent LBP and get job satisfaction and self-progress.
Cervical spinal cord atrophy in amyotrophic lateral sclerosis across disease stages
Authors: Nigri Anna , Dalla Bella Eleonora , Ferraro Stefania , Medina Carrion Jean Paul , Demichelis Greta , Bersano Enrica , Consonni Monica , Bischof Antje , Stanziano Mario , Palermo Sara , Lauria Giuseppe , Bruzzone Maria Grazia , Papinutto Nico
Published: January 2023

Objective

Spinal cord degeneration is a hallmark of amyotrophic lateral sclerosis. The assessment of gray matter and white matter cervical spinal cord atrophy across clinical stages defined using the King's staging system could advance the understanding of amyotrophic lateral sclerosis progression.

Methods

We assessed the in vivo spatial pattern of gray and white matter atrophy along cervical spinal cord (C2 to C6 segments) using 2D phase‐sensitive inversion recovery imaging in a cohort of 44 amyotrophic lateral sclerosis patients, evaluating its change across the King's stages and the correlation with disability scored by the amyotrophic lateral sclerosis functional rating scale revised (ALSFRS‐R) and disease duration. A mathematical model inferring the potential onset of cervical gray matter atrophy was developed.

Results

In amyotrophic lateral sclerosis patients at King's stage 1, significant cervical spinal cord alterations were mainly identified in gray matter, whereas they involved both gray and white matter in patients at King's stage ≥ 2. Gray and white matter areas correlated with clinical disability at all cervical segments. C3–C4 level was the segment showing early gray matter atrophy starting about 7 to 20 months before symptom onset according to our model.

Interpretation

Our findings suggest that cervical spinal cord atrophy spreads from gray to white matter across King's stages in amyotrophic lateral sclerosis, making spinal cord magnetic resonance imaging an in vivo assessment tool to measure the progression of the disease.
Intracranial plaque with large lipid core is associated with embolic stroke of undetermined source
Authors: Tao Lin , Wang Xin‐Hong , Li Xiao‐Qiu , Dai Ying‐Jie , Yang Ben‐Qiang , Chen Hui‐Sheng
Published: January 2023

Objective

To investigate an association between percentage lipid‐rich necrotic core (LRNC) and an index ischemic stroke in an embolic stroke of undetermined source (ESUS) cohort.

Methods

A total of 167 ESUS patients with 259 non‐stenotic intracranial plaques including 155 ipsilateral and 104 contralateral to stroke were finally enrolled in the current analysis. The multi‐dimensional parameters involving remodeling index (RI), plaque burden (PB), LRNC, discontinuity of plaque surface (DPS), intraplaque hemorrhage (IPH), and vulnerable plaque defined as presence of complicated plaque were evaluated by high‐resolution magnetic resonance imaging.

Results

We found that %LRNC was an independent predictor for ESUS in model 1 (OR: 2.574, 95% CI: 1.854–3.573, P < 0.001), and model 2 (OR: 2.550, 95% CI: 1.835–3.545, P < 0.001), but the association was not seen in PB. In receiver operating characteristic curve analysis, the discrimination of LRNC for ESUS was significantly superior to that of PB (absolute difference: 0.121, 95% CI: 0.056–0.205, P < 0.001). Importantly, a significantly positive synergy between the remodeling pattern and LRNC in response to plaque vulnerability was found by Sankey diagram (P for interaction = 0.001).

Conclusion

This is the first report that LRNC, beyond PB, may be correlated with an index ESUS, and a synergistic effect between positive remodeling and larger LRNC could promote plaque vulnerability. The findings suggest that a potential target subgroup may benefit from stroke prevention with intensive statin, although this must be confirmed in future.
Design and Development of Extracellular Matrix Protein‐Based Microcapsules as Tools for Bacteria Investigation
Authors: Pashapour Sadaf , Seneca Senne , Schröter Martin , Frischknecht Friedrich , Platzman Ilia , Spatz Joachim
Published: January 2023

The extracellular matrix (ECM) plays an immense role in the homeostasis of tissues and organs, can function as a barrier for infectious agents, but is also exploited by pathogens during infection. Therefore, the development of well‐defined 3D ECM models in the form of microcapsules to elucidate the interactions between ECM components and pathogens in confinement and study disease infectivity is important, albeit challenging. Current limitations are mainly attributed to the lack of biocompatible methods for the production of protein‐based microcapsules. Herein, hollow ECM‐based microcapsules from laminin‐111 or laminin‐111/collagen IV are generated to investigate the behavior of organisms within confined 3D extracellular matrices. Microcapsules are created using water‐in‐oil emulsion droplets stabilized by block copolymer surfactants as templates for the charge‐mediated attraction of laminin or laminin‐collagen proteins to the droplets’ inner periphery, allowing for the formation of modular ECM‐based microcapsules with tunable biophysical and biochemical properties and organism encapsulation. The release of E. coli‐laden ECM‐based protein microcapsules into a physiological environment revealed differences in the dynamic behavior of E. coli depending on the constitution of the surrounding ECM protein matrix. The developed ECM‐based protein microcapsules have the potential to be implemented in several biomedical applications, including the design of in vitro infection models.