bluuebunny/crossref_metadata_2025 huggingface dataset:
A survey of clinical factors and patient dose in mammography
Authors: Kruger Randell L. , Schueler Beth A.
Published: July 2002

A survey was conducted to estimate the mean glandular dose (MGD) for women undergoing mammography and to report the distribution of doses, compressed breast thickness, glandular tissue content, and mammographic technique factors used. From 24 471 mammograms, of 6006 women, clinical data were collected. The survey data included mammograms from seven modern units using a molybdenum (Mo) anode and either Mo or rhodium (Rh) filter. Exposure factors for each mammogram were recorded automatically onto a floppy disk on each unit. All mammography units were calibrated individually using breast tissue equivalent attenuation slabs of varying glandular content, so the breast glandular content could be estimated on the basis of exposure factors and compressed breast thickness. The MGD was estimated for each mammogram based on the normalized glandular dose and calculated entrance exposure in air. The survey found a median MGD of 2.6 mGy. The median breast glandular tissue content was 28% and the median compressed breast thickness was 5.1 cm. Also, patient attenuation data were converted to equivalent BR‐12 and acrylic thickness to help determine appropriate phantom thicknesses required for mammography unit automatic exposure control performance assessment.
A method for measuring the presampled MTF of digital radiographic systems using an edge test device
Authors: Samei Ehsan , Flynn Michael J. , Reimann David A.
Published: July 2002

The modulation transfer function (MTF) of radiographic systems is frequently evaluated by measuring the system's line spread function (LSF) using narrow slits. The slit method requires precise fabrication and alignment of a slit and high radiation exposure. An alternative method for determining the MTF uses a sharp, attenuating edge device. We have constructed an edge device from a 250‐μm‐thick lead foil laminated between two thin slabs of acrylic. The device is placed near the detector and aligned with the aid of a laser beam and a holder such that a polished edge is parallel to the x‐ray beam. A digital image of the edge is processed to obtain the presampled MTF. The image processing includes automated determination of the edge angle, reprojection, sub‐binning, smoothing of the edge spread function (ESF), and spectral estimation. This edge method has been compared to the slit method using measurements on standard and high‐resolution imaging plates of a digital storage phosphor (DSP) radiography system. The experimental results for both methods agree with a mean MTF difference of 0.008. The edge method provides a convenient measurement of the presampled MTF for digital radiographic systems with good response at low frequencies.
Using refractive index gradients to measure diffusivity between liquids
Authors: Gaffney C. , Chau Cheuk-Kin
Published: July 2002

One most commonly thinks of refraction occurring when light strikes at an angle to an interface separating two regions with different refractive indices. However, a light ray traveling normal to such an interface will also be refracted, if the second region has a refractive index gradient parallel to the interface plane. If liquid–liquid interdiffusion produces such a gradient in the second region, then one can infer the diffusivity of solute particles by measuring the time-dependent refraction. We have performed such diffusion experiments with three different aqueous solutions and found reasonably good agreement with diffusivity values given in the literature. The experimental setup and data analysis are simple enough for an undergraduate student to complete in a few weeks, making this investigation ideal for inclusion in an advanced laboratory course.
A wormhole with a special shape function
Authors: Kuhfittig Peter K. F.
Published: July 2002

This paper presents a wormhole solution using a special shape function. The solution suggests that, at least mathematically, the region requiring exotic matter can be made arbitrarily small.
Complex modal statistics in a reverberant dissipative body
Authors: Lobkis O. I. , Weaver R. L.
Published: July 2002

The statistics of the ultrasonic resonance peaks of a finite elastic body are investigated. The distribution of peak phases, and the normalized variance of peak amplitudes, are shown to be consistent with a hypothesis that the modes themselves are complex Gaussian random numbers. A value q=0.33 for the ratio of the standard deviations of the imaginary and real parts of the modes is found to fit the data, and to bring recent theory of power variances into better accord with measurements.
𝕊-matrix theory applied to acoustic scattering by asymmetrically fluid-loaded elastic isotropic plates
Authors: Franklin H. , Danila E. , Conoir J.-M.
Published: July 2002

Exact and approximate formalisms describing the interactions of acoustic plane waves with an elastic isotropic plate immersed between two different fluids (asymmetrically fluid-loaded plate) are presented. This constitutes an extension of the Fiorito, Madigosky, and Überall (FMU) [R. Fiorito et al., J. Acoust. Soc. Am. 66, 181 (1979)] theory, refined later by Freedman [A. Freedman, J. Sound Vib. 82, 181 (1982); ibid. 82, 197 (1982)]. The method, based upon the multichannel resonant scattering theory derived from quantum physics [A. Bohm, Quantum Mechanics, Foundations, and Applications (Springer, New York, 1993)], consists of two parts. First, a 2×2 scattering 𝕊-matrix in which the diagonal elements are the two reflection coefficients and the off-diagonal elements are the two transmission coefficients, is built. Second, in order to compare our results with the FMU theory, resonant approximations are given for these coefficients, assuming light fluids when compared to the plate. The approximated coefficients show that the resonance widths are the sum of two independent partial widths, each of them being related to one fluid and to the plate physical properties. Of importance in this extension is the fact that the eigenvalues of the matrix, which reveal all the resonant features of the immersed plate, allow the separation between antisymmetrical and symmetrical modes, contrary to the reflection and transmission coefficients. The eigenvalues also allow the analysis of resonances despite the overlapping phenomenon. For the computations, the exact coefficients and eigenvalues, rather than their approximate forms, are used. This allows us to check the validity of the exact part of the theory under any fluid loading and not especially for light fluid loading.
Reduction of noise transmission through an aperture using active feedforward noise control
Authors: Romeu J. , Jiménez S. , Capdevila R. , Dı́az N.
Published: July 2002

A local active noise control technique has been applied to reduce noise emission through an aperture in the wall of the enclosure. Pressure cancellation was effected at the center of an aperture of 0.3×0.3 m2 for an enclosure of 2 m3 volume, and the reduction in sound was measured at various locations at the aperture and at some distance from the enclosure. The results showed that sound pressure cancellation at the window implies emission attenuation through itself, and a relationship between attenuation at the window and outside the enclosure is confirmed. The behavior of attenuation results at the window is related to frequency, to the modal density of the sound field in the enclosure, and to the distance between the error microphone and secondary source.
Seafloor acoustic backscattering from different geological provinces in the Atlantic Natural Laboratory
Authors: Greaves Robert J. , Stephen Ralph A.
Published: July 2002

The characteristics of acoustic signals backscattered from inside-corner and outside-corner oceanic crust are investigated using acoustic reverberation data from the 1993 Acoustic Reverberation Special Research Program (ARSRP) Acoustics Cruise. Specifically, the seafloor dip distribution, as measured from Hydrosweep bathymetry data is compared in areas of each crustal type and a correlation between seafloor dip and seafloor scattering strength is sought. Beamformed and match-filtered acoustic data from the site A (run 1) monostatic, wideband, LFM (linear frequency modulated) experiment are used to find the scattering strength corresponding to specific areas of the seafloor. Scattering strength is determined as the average of intersecting beams from different source locations in order to reduce the left–right ambiguity inherent in beamsteering of a linear array. When overlaid on the bathymetry map, high-scattering strengths are found to correspond to steep flanks of seafloor features and can be used to determine their shape and orientation. Some of these feature shapes are characteristic of specific crustal regions. Cross-plotting scattering strength with true grazing angle or seafloor dip shows a trend increasing at a rate of about 0.1 dB/deg. This trend is not, however, sufficiently constrained to be a useful predictor. It is concluded that the seafloor dip, on the scale of a few hundreds of meters, that can be resolved with Hydrosweep bathymetry data, influences but does not determine, scattering strength. Since, in detail, the observed variations in scattering strength are larger than can be explained by data error or seafloor dip, it is suggested that other characteristics of steeply dipping areas, such as subsurface properties or smaller scale surface features, strongly affect the level of backscattered signals.
Prosodic features at discourse boundaries of different strength
Authors: Swerts Marc
Published: July 2002

This paper presents the design and the evaluation of a method to study prosodic features of discourse structure in unrestricted spontaneous speech. Past work has indicated that one of the major difficulties that discourse prosody analysts have to overcome is finding an independent specification of hierarchical discourse structure as to avoid circularity. Previous studies have tried to solve this problem by constraining the discourse or by basing segmentations on a specific discourse theory. The current investigation first explores the possibility of experimentally determining discourse boundaries in unrestricted speech. In a next stage, it is investigated to what extent boundaries obtained in this way correlate with specific prosodic variables: the features pause, pitch range, and type of boundary tone are studied as a function of discourse structure.
Diffuse transmission of structure-borne sound at periodic junctions of semi-infinite plates
Authors: Bosmans I. , Vermeir G.
Published: July 2002

Vibration attenuation at junctions of point connected plates is an important aspect of structure-borne sound transmission in many realistic structures. The vibrational response of point connected plates can be predicted using statistical energy analysis (SEA), where coupling loss factors are calculated based on mobility formulations. However, in the process of deriving the coupling loss factors for point connected systems, a number of assumptions and simplifications were introduced. In this paper, a more advanced calculation model, based on a wave approach for elastically coupled semi-infinite plates, is presented. Local rigid connections are modeled using an elastic interlayer characterized by a space-dependent stiffness. Periodic boundary conditions are assumed at the junction and the plate response is described using a Fourier decomposition technique. Calculation results obtained for two different junction geometries demonstrate the influence of the distance between the point connections on the structure-borne sound transmission. Finally, a comparison between a number of numerical and experimental results illustrates the ability of the model to predict the influence of the density and the width of the point connections with good accuracy.
Simulation of the effect of threshold elevation and loudness recruitment combined with reduced frequency selectivity on the intelligibility of speech in noise
Authors: Nejime Yoshito , Moore Brian C. J.
Published: July 2002

The effect of loudness recruitment and threshold elevation together with reduced frequency selectivity have been simulated to examine the combined effect of the two major consequences of cochlear hearing loss on the intelligibility of speech in speech-shaped noise. In experiment 1, four conditions were simulated: a moderate flat loss with auditory filters broadened by a factor of three (B3R2); a moderate-to-severe sloping loss with auditory filters broadened by a constant factor of three (B3RX); and these conditions with linear amplification applied prior to the simulation processing (B3R2+, B3RX+). For conditions B3R2 and B3RX, performance was markedly worse than for a control condition (normal hearing, condition R1) tested in a previous study. For conditions B3R2+ and B3RX+, linear amplification improved performance considerably. However, performance remained below that for condition R1 by between 5% and 19%. In experiment 2 the broadening of the auditory filters was made more realistic by making it a function of the absolute threshold at the center frequency of the auditory filter. Three different hearing losses were simulated: a moderate-to-severe sloping loss with variable broadening of the auditory filters (BXRX); the same moderate-to-severe sloping loss with linear amplification (BXRX+); and the same broadening of the auditory filters but without the simulation of loudness recruitment and threshold elevation (BX). For condition BXRX, performance was markedly worse than in condition R1, while performance in condition BX was somewhat worse than for condition R1. For condition BXRX+, linear amplification according to the NAL procedure improved performance to a large extent but it remained worse than for condition R1. The results are consistent with previous evidence indicating that only part of the decrease of performance produced by actual cochlear hearing loss can be compensated by conventional linear hearing aids.
The effects of a soluble surfactant on quadrupole shape oscillations and dissolution of air bubbles in water
Authors: Asaki Thomas J. , Marston Philip L.
Published: July 2002

Single air bubbles were ultrasonically trapped in aqueous solutions of the soluble surfactant Triton X-100. Quadrupole shape oscillations were induced by modulation of the radiation pressure and the free decay was recorded using an optical extinction technique. The frequency and damping were found to be maximal at a bulk surfactant concentration which only weakly affects the surface tension. At higher concentrations the frequency is reduced due to surface tension depression and the damping approaches a value several times that expected for a clean interface. These results are in qualitative agreement with theoretical predictions based on interfacial viscoelastic considerations. Bubble size and dissolution curves were obtained through the use of digitized bubble images. Dissolution rates are shown to be significantly enhanced by the presence of the surfactant.
A simplified formula for viscous and chemical absorption in sea water
Authors: Ainslie Michael A. , McColm James G.
Published: July 2002

A simplified expression is presented for predicting the absorption of sound in sea water, retaining the essential dependence on temperature, pressure, salinity, and acidity of the more complicated formula on which it is based [R. E. Francois and G. R. Garrison, “Sound absorption based on ocean measurements. Part II: Boric acid contribution and equation for total absorption,” J. Acoust. Soc. Am. 72, 1879–1890 (1982)]. The accuracy of the simplified formula is demonstrated by comparison with the original one for a range of oceanographic conditions and frequencies between 100 Hz and 1 MHz.
Acoustical properties of end-initiated explosive line charges
Authors: Marshall William J.
Published: July 2002

Acoustic radiation produced by end-fired explosive line charges is examined experimentally and theoretically. Three explosive compositions are studied: PETN detonating cord, RDX detonating cord, and thin ribbons of HLX. Specific output levels are formulated for each of the three explosive materials over the four 1-oct bands spanning 50–800 Hz. Bubble period relationships are derived for each material and compared to previous studies. In terms of directivity effects, long line charges are found to behave like beam-steered continuous arrays over moderately wide bands. A math model is developed which predicts acoustic levels and spectrum shapes for the shock wave component over a wide range of view angles and linear charge densities. This model is driven by two parameters which are extracted from the experimental data for the three compositions studied. The result is a practical means of designing explosive line arrays to desired source levels, bandwidths, and beam patterns.
Dichotic pitches as illusions of binaural unmasking. I. Huggins’ pitch and the “binaural edge pitch”
Authors: Culling John F. , Summerfield A. Quentin , Marshall David H.
Published: July 2002

The two most salient dichotic pitches, the Huggins pitch (HP) and the binaural edge pitch (BEP), are produced by applying interaural phase transitions of 360 and 180 degrees, respectively, to a broadband noise. This paper examines accounts of these pitches, concentrating on a “central activity pattern” (CAP) model and a “modified equalization-cancellation” (mE-C) model. The CAP model proposes that a dichotic pitch is heard at frequency f when an individual across-frequency scan in an interaural cross-correlation matrix contains a sharp peak at f. The mE-C model proposes that a dichotic pitch is heard when a plot of interaural decorrelation against frequency contains a peak at f. The predictions of the models diverge for the BEP at very narrow transition bandwidths: the mE-C model predicts that salience is sustained, while the CAP model predicts that salience declines and that the dominant percept is of the in-phase segment of the noise. Experiment 1 showed that the salience of the BEP was sustained at the narrowest bandwidths that could be generated (0.5% of the transition frequency). Experiment 2 confirmed that the pitch of a BEP produced by a 0.5% transition bandwidth was close to the frequency of the transition band. Experiment 3 showed that pairs of simultaneous narrow 180-degree transitions, whose frequencies corresponded to vowel formants, were perceived as the intended vowels. Moreover, the same vowels were perceived whether the in-phase portion of the noise lay between the two transition frequencies or on either side of them. In contrast, different patterns of identification responses were made to diotic band-pass and band-stop noises whose cutoff frequencies corresponded to the same formants. Thus, the vowel-identification responses made to the dichotic stimuli were not based on hearing the in-phase portions of the noise as formants. These results are not predicted by the CAP model but are consistent with the mE-C model. It is argued that the mE-C model provides a more coherent and parsimonious account of many aspects of the HP and the BEP than do alternative models.
Some physical models for estimating scattering of underwater sound by algae
Authors: Shenderov Evgeni L.
Published: July 2002

A theoretical study of scattering of underwater sound waves by algae has been performed. The dependenies of sound level in reflected waves on parameters of algae (sizes, biomass) are determined. To this purpose, the physical models corresponding to typical algae species are developed. Scattering of sound by algae is treated as diffraction of a sound wave on a random system of three-dimensional bent elastic bodies. Sound pressure in the waves scattered by acoustically semitransparent bent plates and rods corresponding to alga leaves and stems is computed. The statistical properties of algae (roughness, inclination) are taken into account. The theoretical estimations are compared with experimental values. The obtained results can be used for the development of the methods of exploration of the continental shelf and also for the assessment algae resources.
Padé approximants for the acoustical properties of rigid frame porous media with pore size distributions
Authors: Horoshenkov K. V. , Attenborough Keith , Chandler-Wilde S. N.
Published: July 2002

Expressions for the viscosity correction function, and hence bulk complex impedance, density, compressibility, and propagation constant, are obtained for a rigid frame porous medium whose pores are prismatic with fixed cross-sectional shape, but of variable pore size distribution. The low- and high-frequency behavior of the viscosity correction function is derived for the particular case of a log-normal pore size distribution, in terms of coefficients which can, in general, be computed numerically, and are given here explicitly for the particular cases of pores of equilateral triangular, circular, and slitlike cross-section. Simple approximate formulae, based on two-point Padé approximants for the viscosity correction function are obtained, which avoid a requirement for numerical integration or evaluation of special functions, and their accuracy is illustrated and investigated for the three pore shapes already mentioned.
Demographic and attitudinal factors that modify annoyance from transportation noise
Authors: Miedema Henk M. E. , Vos Henk
Published: July 2002

The effect of demographic variables (sex, age, education level, occupational status, size of household, homeownership, dependency on the noise source, and use of the noise source) and two attitudinal variables (noise sensitivity and fear of the noise source) on noise annoyance is investigated. It is found that fear and noise sensitivity have a large impact on annoyance (DNL equivalent equal to [at most] 19 and 11 dB, respectively). Demographic factors are much less important. Noise annoyance is not related to gender, but age has an effect (DNL equivalent equal to 5 dB). The effects of the other demographic factors on noise annoyance are (very) small, i.e., the equivalent DNL difference is equal to 1–2 dB, and, in the case of dependency, 3 dB. The results are based on analyses of the original data from various previous field surveys of response to noise from transportation sources (number of cases depending on the variable between 15 000 and 42 000).
Aeroelastic structural acoustic control
Authors: Clark Robert L. , Frampton Kenneth D.
Published: July 2002

Static, constant-gain, output-feedback control compensators were designed to increase the transmission loss across a panel subjected to mean flow on one surface and a stationary, acoustic half-space on the opposite surface. The multi-input, multi-output control system was based upon the use of an array of colocated transducer pairs. The performance of the static-gain, output-feedback controller was compared to that of the full state-feedback controller using the same control actuator arrays, and was found to yield comparable levels of performance for practical limitations on control effort. Additionally, the resulting static compensators proved to be dissipative in nature, and thus the design varied little as a function of the aeroelastic coupling induced by the fluid–structure interaction under subsonic flow conditions. Several parametric studies were performed, comparing the effects of control-effort penalty as well as the number of transducer pairs used in the control system.
Multifrequency acoustical volume backscattering patterns in the Arabian Sea—265 kHz to 3 MHz
Authors: McGehee Duncan E. , Greenlaw Charles F. , Holliday D. V. , Pieper Richard. E.
Published: July 2002

High-frequency acoustical volume backscattering was examined during three periods of the annual cycle of winds in the Arabian Sea—the Winter Northeast (NE) Monsoon, the Summer Southwest (SW) Monsoon, and the Fall Intermonsoon—using a multifrequency acoustic profiling system deployed on an undulating towed body. This system measured acoustical volume backscattering strengths at six frequencies ranging from 265 kHz to 3.0 MHz. Measurements were made from near the surface to 250 m depth along a ship track that paralleled the coast of Oman, then proceeded away from the coast towards the middle of the Arabian Sea. At all frequencies, volume backscattering strength was highest near the surface, decreasing with increasing depth. Contrary to expectation, backscattering was generally lower during the Summer SW Monsoon than during the Winter NE Monsoon. Also contrary to expectation, backscattering was not appreciably higher near the coast than it was offshore during the Summer SW Monsoon, although it was higher near the coast during the Winter NE Monsoon. Generally speaking, regional and seasonal differences were smaller than expected, and much smaller than the fine-scale spatial and temporal variability, particularly at frequencies below 1 MHz. There was a daily pattern of increased nighttime backscattering in the upper 100 m at 265 and 420 kHz. This pattern was less evident at 1.1 MHz and above.
Traction-free vibration of layered elastic and piezoelectric rectangular parallelepipeds
Authors: Heyliger Paul
Published: July 2002

A variational method is developed to study the traction-free vibration of layered rectangular elastic and piezoelectric parallelepipeds. The weak form of the equations of motion and the charge equation are formulated in rectangular Cartesian coordinates. Approximate solutions to these equations are sought in a form that combines piecewise linear or quadratic Lagrange basis functions through the layered dimension of the solid with continuous global polynomial or trigonometric functions in the plane. This allows for the necessary discontinuity in the shear strain and normal potential gradient across the interface between layers caused by the mismatch in material properties. Numerical results compare very well with those computed by other techniques for layered elastic and piezoelectric plates with simple support and homogeneous parallelepipeds under stress-free conditions. New results are presented for layered systems.
Limits of time-reversal focusing through multiple scattering: Long-range correlation
Authors: Derode Arnaud , Tourin Arnaud , Fink Mathias
Published: July 2002

Experimental results of time-reversal focusing in a high-order multiple scattering medium are presented and compared to theoretical predictions based on a statistical model. The medium consists of a random collection of parallel steel rods. An ultrasonic source (3.2 MHz) transmits a pulse that undergoes multiple scattering and is recorded on an array. The time-reversed waves are sent by the array back to the source through the scattering medium. The quality of temporal focusing is very well predicted by a simple statistical model. However, for thicker samples, persistent temporal side-lobes appear. We interpret these side-lobes as a consequence of the growing number of crossing paths in the sample due to high-order multiple scattering. As to spatial focusing, the resolution is practically independent from the array’s aperture. With a 16-element array, the resolution was found to be 30 times finer than in a homogeneous medium. Resolutions of the order of the wavelength (0.5 mm) were attained. These results are discussed in relation with the statistical properties of time-reversal mirrors in a random medium.
Structural study of cadmium hydroxide sulfates. VI. The layer structure of Cd4SO4(OH)6.1.5H2O studied from X-ray powder and single-crystal diffraction data
Authors: Louër D. , Rius J. , Bénard-Rocherullé P. , Louër M.
Published: July 2002

The crystal structure of the layered cadmium hydroxide sulfate Cd4SO4(OH)6.1.5H2O has been solved from X-ray powder diffraction data. The compound crystallizes with hexagonal symmetry,a=9.145(1) Å,c=15.099(3) Å,V=1093.5 Å3,Z=4, space groupP63. Due to the unusual environment of one cadmium atom and to the fact that a suitable thin tabular crystal could be found later, a single-crystal X-ray diffraction experiment was also carried out. In both cases the structure was solved applying direct-methods. The refinements converged to the residual factorsRwp=0.152 andRF=0.059 from the powder data andR1=0.058 andwR=0.165 for the single crystal data case. The structure is built from brucite-type layers based on CdO6octahedra, in which one-seventh of the octahedral sites are empty. Directly above and below these empty sites, two additional octahedrically coordinated Cd atoms are located. The crystal chemistry of the cadmium hydroxide sulfate family is discussed.
Trends in Supply of Nursing Home Beds, 2011-2019
Authors: Miller Katherine E. M. , Chatterjee Paula , Werner Rachel M.
Published: March 2023

Importance

Nursing homes play a vital role in providing postacute and long-term care for individuals whose needs cannot be met in the home or community. Whether the supply of nursing home beds and, specifically, the supply of high-quality beds has kept pace with the growth of the older adult population is unknown.

Objective

To describe changes in the supply of population-adjusted nursing home beds from 2011 to 2019.

Design, Setting, and Participants

This cross-sectional study examines changes in the population-adjusted supply of nursing home beds across all US counties from 2011 to 2019 and describes county and nursing home characteristics where the supply of nursing home beds has increased vs decreased.

Main Outcomes and Measures

Number of nursing home beds adjusted per 10 000 adults aged 65 years and older.

Results

The population-adjusted supply of nursing home beds declined from 2011 to 2019 for 86.4% of US counties, by a mean (SD) of 129.9 (123.8) beds per 10 000 adults aged 65 years or older per county from a baseline mean (SD) of 552.5 (274.4) beds per 10 000 adults aged 65 years or older per county in 2011. The share of beds that were high quality (4- or 5-star ratings) also declined, which was driven by a small number of counties where nursing home bed supply increased due to a proliferation of lower-quality beds. Simultaneously, metropolitan counties with declining numbers of nursing home beds also experienced declining number of senior housing residential beds (−11.3 [54.6] beds per 10 000 adults aged 65 years or older per county from a baseline mean [SD] of 354.8 [222.3]).

Conclusions and Relevance

The findings of this cross-sectional study suggest that the supply of nursing home beds, specifically high-quality nursing home beds, and senior residential housing beds have not kept pace with the demographics of an aging population. Understanding the supply of high-quality nursing home beds and associated geographic variation can inform targeted policies to best support older adults requiring nursing home care.
Impact of electronic portal image quality on Elekta AQUA® collimator isocenter
Authors: Norvill Craig A. J.
Published: March 2023

Purpose

The collimator radiation isocenter position determined in AQUA® v3.0 [Elekta AB, Stockholm, Sweden] software test “MLC Leaf and Jaw Position” was independently validated using an in‐house MATLAB [Natick, MA: The MathWorks Inc.] script.

Methods

The AQUA test determines radiation isocenter using the mean field center of nine 4 cm × 4 cm electronic portal imager (EPID) exposures at equidistant collimator angles. Impact of EPID image quality on AQUA reported isocenter for thirteen Elekta linear accelerators with Agility MLC heads were evaluated.

Results

Of the thirteen, three had visually and quantitatively identifiable artifacts. For the ten good EPID's there was a systematic 0.25 mm offset of the MATLAB calculated mean field center relative to AQUA in the X‐axis and Y‐axis. This corresponds to one image pixel and was found to be due to differences in software co‐ordinate convention. After subtracting this offset there was no significant difference in AQUA and MATLAB calculated isocenter.

Conclusions

For the three machines with poor image quality there was a demonstrated variation in AQUA calculated field center and therefore radiation isocenter relative to MATLAB. Restricting the region of interest (ROI) in AQUA software to only the irradiated section of the EPID brought AQUA and MATLAB result for these three machines into agreement.
Factory quality assurance of passive radiotherapy intensity modulators for electrons using kilovoltage x‐ray imaging
Authors: McGuffey Andrew S. , Pitcher Garrett M. , Guidry Rebecca L. , Erhart Kevin J. , Hogstrom Kenneth R.
Published: March 2023

Purpose

This work developed an x‐ray‐based method for performing factory quality assurance (QA) of Passive Radiotherapy Intensity Modulators for Electrons (PRIME) device fabrication. This method measures errors in position, diameter, and orientation of cylindrical island blocks on a hexagonal grid that comprises PRIME devices and the impact of such errors on the underlying intensity distribution.

Methods

X‐ray images were acquired of six PRIME devices, which modeled three error cases (small random, large random, and systematic errors) for two island block diameters (0.158 and 0.352 cm). Island blocks in each device, 0.6 cm long tungsten cylinders of constant diameter, were spaced 0.6 cm on a hexagonal grid over approximately 8 cm square. Using a 50 kVp x‐ray image, each island block projected a racetrack, whose perimeter was fit to a function that allowed determination of its position, diameter, and angular orientation (θ, ϕ). These measured parameters were input into a pencil beam algorithm (PBA) dose calculation performed in water (16 MeV, SSD = 103 cm) for each device. PBA calculated intensity distributions using measured and planned (exact) island block parameters were compared.

Results

Θ distributions for the 0.158 and 0.352 cm devices were nearly identical for each error case, with θ values for most island blocks being within 3.2°, 8.5°, and 7.5° for the small random, large random, and systematic error PRIME devices, respectively. Corresponding intensity differences between using measured and planned island block parameters were within 1.0% and 2.8% (small random), 2.2% and 4.8% (large random), and 3.2% and 6.7% (systematic) for the 0.158 and 0.352 cm devices, respectively.

Conclusion

This approach provides a viable and economical method for factory QA of fabricated PRIME devices by determining errors in their planned intensity distribution from which their quality can be assessed prior to releasing to the customer.
Woven Fibrous Photodetectors for Scalable UV Optical Communication Device
Authors: Deng Xiaolei , Li Ziqing , Cao Fa , Hong Enliu , Fang Xiaosheng
Published: March 2023

Fibrous photodetectors (FPDs) have attracted great interest in wearable and consumer electronics, which is a lightweight and flexible tools to achieve efficient light information transmission. However, there is a necessary compromise between high optoelectronic performance and high‐level integration. Herein, a woven optoelectronic keyboard consisting of 40 PD button units is extended and integrated from four individual FPDs, with the integration level expanding by 1000%. Each FPD is based on uniform type‐II TiO2/Cs3Cu2I5 heterojunction, which exhibits greatly reduced dark current by eight orders of magnitudes, large rectification ratio up to 33306@± 5V, high on–off ratio of 2.8 × 104@−1 V and self‐powered responsivity of 26.9 mA W−1. The vacuum‐deposited Cs3Cu2I5 nanoparticles finely passivate the massive defects and serve as a p‐type hole transport layer to improve hole transfer efficiency, which greatly promotes the radial transport and collection of photogenerated electrons. Moreover, the photocurrent remains highly stable after bending and twisting states. Intriguingly, the woven optoelectronic keyboards successfully realize logic AND/OR, further identifying the UV light signal as a keying text signal (“A–Z” letters, “0–9” numbers, and four punctuations). This work not only provides a scalable strategy to reduce device redundancy but also shows the great potential of fibrous photodetectors for wearable optical communication.
Integrated and Bifunctional Bilayer 3D Printing Scaffold for Osteochondral Defect Repair
Authors: Li Cairong , Zhang Wei , Nie Yangyi , Jiang Dongchun , Jia Jingyi , Zhang Wenjing , Li Long , Yao Zhenyu , Qin Ling , Lai Yuxiao
Published: March 2023

Bioinspired scaffolds with two distinct regions resembling stratified anatomical architecture provide potential strategies for osteochondral defect repair and are studied in preclinical animals. However, delamination of the two layers often causes tissue disjunction between the regenerated cartilage and subchondral bone, leading to few commercially available clinical applications. This study develops an integrated poly(ε‐caprolactone) (PCL)‐based scaffold for repairing osteochondral defects. An extracellular matrix (ECM)‐incorporated 3D printing composite scaffold (ECM/PCL) coated with ECM hydrogel (E‐co‐E/PCL) is fabricated as the upper layer, and magnesium oxide nanoparticles coated with polydopamine (MgO@PDA)‐incorporated composite scaffold (MD/PCL) is fabricated using 3D printing as the bottom layer. The physicochemical and mechanical properties of the bilayer scaffold meet the requirements in designing and fabricating the osteochondral scaffold, especially a strong interface possessed between the two layers. By in vitro study, the integrated scaffold stimulates proliferation, chondrogenic differentiation, and osteogenic differentiation of human bone mesenchymal stem cells. Moreover, the integrated bilayer scaffold exhibits well repair ability to facilitate simultaneous regeneration of cartilage and subchondral bone after implanting into the osteochondral defect in rats. In addition, cartilage “tidemarks” completely regenerated after 12 weeks of implantation of the bilayer scaffold, which indicates no tissue disjunctions formed between the regenerated cartilage and subchondral bone.
YAP‐Suppressive Nanodrug Crosslinked Self‐Immunoregulatory Polysaccharide Injectable Hydrogel for Attenuating Cardiac Fibrosis to Treat Myocardial Infarction
Authors: Sun Yage , Zhang Xiaoping , Wu Tengling , Zhang Zhuodan , Yang Rong , Liu Wenguang
Published: March 2023

The cardiac fibrosis caused by excessive deposition of collagen and the fibro‐inflammatory cascade reaction severely impedes the cardiac regenerative efficiency after myocardial infarction (MI) so that the onefold treating target is far from satisfying therapeutic efficacy. Herein, a yes‐associated protein (YAP)‐suppressive nanodrug‐crosslinked self‐immunoregulatory polysaccharide injectable hydrogel is fabricated for the first time. To this end, cationic liposomes loading YAP inhibitor verteporfin (Lipo‐VP) is prepared and coated with oxidized fucoidan (OFu), a unique anti‐inflammation polysaccharide, to form anti‐fibrotic and immunoregulatory nanodrug (OFu‐Lipo‐VP). The coated fucoidan itself acts as a reactive oxygen species (ROS) scavenger and inflammation regulator, thus facilitating angiogenesis function by eliciting endogenous vascular endothelial growth factor secretion of macrophages. Then an injectable hydrogel (termed as OFu‐Lipo‐VP‐PGA) is formed through addition reaction between the aldehyde groups of OFu‐Lipo‐VP and the thiol groups of thiol‐modified poly(γ‐glutamic acid) (PGA‐SH), where the thiol groups can also aid in eliminating ROS. The acute MI models are established and the infarcted male rats are treated with this injectable OFu‐Lipo‐VP‐PGA hydrogel after MI. The outcomes at 28 days post‐surgery indicate efficient restoration of cardiac functions and attenuation of cardiac fibrosis. This study opens up a new possibility for MI treatment with immunoregulatory and antifibrotic injectable polysaccharide‐based hydrogel.
Carbazole‐Based Anion Ionic Water‐Soluble Two‐Photon Initiator for Achieving 3D Hydrogel Structures
Authors: Bin Fan‐Chun , Guo Min , Li Teng , Zheng Yong‐Chao , Dong Xian‐Zi , Liu Jie , Jin Feng , Zheng Mei‐Ling
Published: March 2023

3D hydrogel structures fabricated by two‐photon polymerization (TPP) have become attractive in biomedical fields. Generally, conventional organic solvents are toxic and the residues left in the fabricated 3D structures are harmful to cells. Hence, anion ionic carbazole‐based water‐soluble two‐photon initiator (TPI) 3,6‐bis[2‐(1‐methylpyridinium)vinyl]‐9‐methylcarbazole ditosylate (BT) is proposed to construct arbitrary 3D hydrogel structures. Cucurbit[7]uril (CB7) and BT form a host‐guest complex (CB7/BT) with a binding ratio of 1:1, which further improves the water solubility, biocompatibility and nonlinear absorption property of TPI. A water‐soluble photoresist consisting of photoinitiator CB7/BT and monomer poly(ethylene glycol) diacrylate is prepared to explore the TPP fabrication capacity. The electron paramagnetic resonance measurement shows that CB7/BT initiates photopolymerization by alkyl radicals. The laser threshold power of the photoresist is 6.3 mW and the feature size is 127 nm in TPP at 780 nm. The initiator with p‐toluenesulfonate anion exhibits higher binding energy, larger two‐photon absorption cross‐section and two‐photon fabrication resolution compared with the previous work using iodide as an anion, indicating a promising way to improve the fabrication capacity of water‐soluble TPI through changing the anion ionic group. The proposed strategy will provide high potential for the further application in the biomedical field.
Strain‐Sensitive Flexible Magnetoelectric Ceramic Nanocomposites
Authors: Kim Minsoo , Kim Donghoon , Aktas Buse , Choi Hongsoo , Puigmartí‐Luis Josep , Nelson Bradley J. , Pané Salvador , Chen Xiang‐Zhong
Published: March 2023

Magnetoelectric (ME) oxide materials can convert magnetic input into electric output and vice versa, making them excellent candidates for advanced sensing, data storage, and communication. However, their application has been limited to rigid devices due to their brittle nature. Here, flexible ME oxide composite (BaTiO3/CoFe2O4) thin film nanostructures with distinct ME coupling coefficients are reported. In contrast to rigid bulk counterparts, these ceramic nanostructures display a flexible behavior after being released from the substrate, and can be transferred onto a stretchable substrate such as polydimethylsiloxane. These ceramic films possess high ME coefficients due to minimized clamping effect and preferred crystalline orientation, and exhibit reversibly tunable ME coupling via mechanical stretching thanks to their large elasticity (>4%). It is believed that the study can open up new avenues for integrating ceramic ME composites into micro‐/nanoelectromechanical system and soft robotic devices.
Effect of physical activity intervention on cognitive function in China: A cluster randomized trial
Authors: Li Nanyan , Deng Qian , Yang Qingyuan , Wang Yufei , Hu Julinling , Zhao Xing , Zhou Junmin
Published: March 2023

INTRODUCTION

Current randomized trial evidence on the effect of physical activity (PA) intervention on cognitive function is scarce and mainly found in well‐educated populations, limiting its generalizability. Furthermore, the modification effect of education levels remains understudied. We conducted a cluster randomized trial to evaluate the effects of PA intervention on cognitive function in a general older population, and whether education modifies such effects.

METHODS

Eight villages were randomized to the intervention (four villages, n = 240) or the control (four villages, n = 271). The intervention group received an 8‐week multilevel PA intervention based on a socio‐ecological model, while the control did not. The intervention has been condensed to three levels with activities occurring at the individual (telephone counseling, printed material, and training sessions), interpersonal (peer group), and community levels (group sharing and coaching). The primary outcome was changes in global cognition (overall cognitive function) measured by the Telephone Interview for Cognitive Status (TICS‐10) at 12‐month follow‐up. Repeated measurements were modeled using the linear mixed model, which assumed that the missing values were missing at random.

RESULTS

The mean age was 70.94 years (standard deviation 5.71) and 55.6% were women. Compared to the control, the orientation improved from baseline at 12‐month follow‐up (0.24 points [95% confidence interval (CI), 0.03 to 0.46 points; P = 0.03]). Stratified analysis showed that the global cognition and orientation improved at 12‐month follow‐up among illiterate participants in the intervention (for global cognition, mean difference, 0.57 points [95% CI, 0.03 to 1.10], P = 0.04; for orientation, mean difference, 0.31 points [95% CI, 0.04 to 0.58], P = 0.03).

DISCUSSION

These results confirm the improvements in orientation in older adults, as well as in global cognition and orientation in the illiterate at 12‐month follow‐up.
The bioelectrical properties of bone tissue
Authors: Heng Boon Chin , Bai Yunyang , Li Xiaochan , Meng Yanze , Lu Yanhui , Zhang Xuehui , Deng Xuliang
Published: March 2023

Understanding the bioelectrical properties of bone tissue is key to developing new treatment strategies for bone diseases and injuries, as well as improving the design and fabrication of scaffold implants for bone tissue engineering. The bioelectrical properties of bone tissue can be attributed to the interaction of its various cell lineages (osteocyte, osteoblast and osteoclast) with the surrounding extracellular matrix, in the presence of various biomechanical stimuli arising from routine physical activities; and is best described as a combination and overlap of dielectric, piezoelectric, pyroelectric and ferroelectric properties, together with streaming potential and electro‐osmosis. There is close interdependence and interaction of the various electroactive and electrosensitive components of bone tissue, including cell membrane potential, voltage‐gated ion channels, intracellular signaling pathways, and cell surface receptors, together with various matrix components such as collagen, hydroxyapatite, proteoglycans and glycosaminoglycans. It is the remarkably complex web of interactive cross‐talk between the organic and non‐organic components of bone that define its electrophysiological properties, which in turn exerts a profound influence on its metabolism, homeostasis and regeneration in health and disease. This has spurred increasing interest in application of electroactive scaffolds in bone tissue engineering, to recapitulate the natural electrophysiological microenvironment of healthy bone tissue to facilitate bone defect repair.
Auroral oval reconstruction for historical geomagnetic storms in the 18th and 19th century
Authors: Wagner D. , Neuhäuser R. , Arlt R.
Published: March 2023

The investigation of extreme space weather events can yield important information about the solar activity. Here, we present the reconstruction of the auroral oval position and size based on Bayesian inference for nine historical geomagnetic storms between 1716 and 1882, including the Carrington event in 1859, by using ground‐based observations, which enables us to derive the Kp index for historical events for the first time. The results for the latter show a very high level of geomagnetic disturbance (8.2 Kp 8.7, −929 nT Dst −1327 nT). Furthermore, we were able to derive the position of the pole in corrected geomagnetic coordinates, where especially the longitude is in good agreement with the position derived from the gufm1 model (Jackson et al., 2000). For the eight other historical storms, the Kp and Dst indices have been calculated here for the first time. In all cases, a very high Kp index was derived. The only exception is the geomagnetic storm from March 1716, which is, with a Kp index of , comparable with the St. Patrick's Day storm in 2015.