bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced cross‐talk correction technique for simultaneous dual‐isotope imaging: A TL‐201/Tc‐99m myocardial perfusion SPECT dog study
Authors: Knešaurek Karin , Machac Josef
Published: July 2002

A newly developed cross‐talk correction method for simultaneous dual‐isotope SPECT imaging was tested in a canine model. The method is based on the assumption that the transformations, which modify the primary energy window images into the scatter images as viewed in the other energy windows, are known. These transformations were found by measuring the point spread functions (PSFs) in two different energy windows for both isotopes in water. The dual‐isotope correction method is described by two convolution equations which were applied in frequency space. The equations take into account the different spatial distributions of the primary and scatter cross‐talk photons. The new enhancement of the method was in applying restoration filters to the resulting corrected images. Three separate studies were acquired in our dog study: two single‐isotope and one dual‐isotope study. The single isotope images were used as references. The contrast between the left ventricle cavity (LVC) and the myocardium was used in transaxial and short‐axis slices as a parameter to evaluate results of dual‐isotope correction method with restoration. The change in contrast in the dual‐isotope corrected images in both energy windows, i.e., Tc‐99m primary window (140 keV) and Tl‐201 primary window (70 keV), was significant. The only exception was for the short‐axis Tc‐99m window images. The corrected 140 keV dual‐isotope short‐axis slice had the contrast of 0.60 vs 0.58, which was the value in the noncorrected dual‐isotope short‐axis slice. For dual‐isotope 140 keV transaxial slice, the contrast changed from 0.72 to 0.82 after correction. In comparison, for single‐isotope Tc‐99m 140 keV transaxial slice, contrast changed from 0.62 to 0.84 after restoration correction. There was less change in contrast in the short‐axis Tc‐99m 140 keV slice, i.e., from 0.56 to 0.61. In the Tl‐201 primary window for the transaxial slices the improvement of contrast was from 0.38 to 0.64, and for short‐axis slices from 0.22 to 0.32 after correction. In the same 70 keV energy window for single‐isotope Tl‐201 images, contrast improved from 0.61 to 0.69 and from 0.35 to 0.38 for transaxial and short‐axis slice, respectively, after applying restoration correction. In conclusion, the presented dual‐isotope correction method with restoration improves the quality of the simultaneous rest Tl‐201/stress Tc‐99m sestamibi SPECT imaging.
An iterative approach to the beam hardening correction in cone beam CT
Authors: Hsieh Jiang , Molthen Robert C. , Dawson Christopher A. , Johnson Roger H.
Published: July 2002

In computed tomography (CT), the beam hardening effect has been known to be one of the major sources of deterministic error that leads to inaccuracy and artifact in the reconstructed images. Because of the polychromatic nature of the x‐ray source used in CT and the energy‐dependent attenuation of most materials, Beer's law no longer holds. As a result, errors are present in the acquired line integrals or measurements of the attenuation coefficients of the scanned object. In the past, many studies have been conducted to combat image artifacts induced by beam hardening. In this paper, we present an iterative beam hardening correction approach for cone beam CT. An algorithm that utilizes a tilted parallel beam geometry is developed and subsequently employed to estimate the projection error and obtain an error estimation image, which is then subtracted from the initial reconstruction. A theoretical analysis is performed to investigate the accuracy of our methods. Phantom and animal experiments are conducted to demonstrate the effectiveness of our approach.
Comment on “Nonlocal character of quantum theory,” by Henry P. Stapp [Am. J. Phys. 65 (4), 300–304 (1997)]
Authors: Shimony Abner , Stein Howard
Published: July 2002

A 1997 paper by Henry Stapp attempts to achieve a definitive argument for his long-sustained thesis that quantum mechanics implies a nonlocality inconsistent with the locality of relativity theory. His argument assumes both the validity of counterfactual reasoning under certain circumstances and the free choice of performance of experiments, and it specifically refrains from any assumptions about “elements of physical reality” as understood by Einstein, Podolsky, and Rosen. In Sec. I we drastically condense his argument but retain his central principle of inference, called “LOC2,” which he claims is a consequence of relativistic locality. By careful attention to counterfactual reasoning we then throw doubt upon this claim and hence upon his argument as a whole. In Sec. II we answer Stapp’s reply to our critique of the 1997 paper. Section III is a postscript, commenting briefly on Stapp’s answer to Sec. II.
A new microcomputer-based laboratory version of the Rüchardt experiment for measuring the ratio γ=Cp/Cv in air
Authors: Torzo Giacomo , Delfitto Giorgio , Pecori Barbara , Scatturin Pietro
Published: July 2002

We describe a new version of the Rüchardt experiment in which we record the time evolution of temperature, pressure, and volume oscillating around an equilibrium value. We use a portable microcomputer-based laboratory made of a graphic calculator, an interface, two commercial sensors (sonar and barometric sensor), and a homemade temperature sensor.
Stochastic models of jitter
Authors: Schoentgen Jean
Published: July 2002

This study presents stochastic models of jitter. Jitter designates small, random, involuntary perturbations of the glottal cycle lengths. Jitter is a base-line phenomenon that may be observed in all voiced speech sounds. Knowledge of its properties is therefore relevant to the acoustic modeling, analysis, and synthesis of voice quality. Also, models of jitter are conceptual frameworks that enable experimenters and clinicians to distinguish jitter in particular from aperiodic cycle length patterns in general. Vocal jitter is modeled by means of the ribbon model of the glottal vibration combined with stochastic models of the disturbances of the instantaneous frequency. The disturbance model comprises correlation-free noise and vocal microtremor. Properties of jitter that are simulated are the stochasticity, stationarity, and normality of the decorrelated cycle length perturbations, the size of decorrelated jitter, the correlation between the perturbations of neighboring glottal cycles, the modulation level and modulation frequency owing to microtremor, the asynchrony between external disturbances and glottal cycles, the dependence of the size of jitter on the average glottal cycle length, and the relation between jitter and laryngeal pathologies. Modeled jitter is discussed in the light of measured jitter, as well as the physiological and statistical plausibility of the model parameters.
Visualization of pass-by noise by means of moving frame acoustic holography
Authors: Park Soon-Hong , Kim Yang-Hann
Published: July 2002

The noise generated by pass-by test (ISO 362) was visualized. The moving frame acoustic holography was improved to visualize the pass-by noise and predict its level. The proposed method allowed us to visualize tire and engine noise generated by pass-by test based on the following assumption; the noise can be assumed to be quasistationary. This is first because the speed change during the period of our interest is negligible and second because the frequency change of the noise is also negligible. The proposed method was verified by a controlled loud speaker experiment. Effects of running condition, e.g., accelerating according to ISO 362, cruising at constant speed, and coasting down, on the radiated noise were also visualized. The visualized results show where the tire noise is generated and how it propagates.
A low-frequency directional flextensional transducer and line array
Authors: Butler Stephen C. , Butler John L. , Butler Alexander L. , Cavanagh George H.
Published: July 2002

A unique low-frequency (900 Hz) class IV flextensional transducer that produces an enhanced far-field pressure on one side and canceled far-field pressure on the other side has been developed. The transducer radiating surface consists of a thick-walled elliptical aluminum shell and a U.S. Navy type III piezoelectric stack along its major axis with two active sections and one inactive section. The directionality is achieved by simultaneously exciting the shell into an omnidirectional and dipole operation by driving stack into both extensional and bending modes. Both measurements and modeling on this device show a front to back pressure ratio of more than 30 dB, producing cardioid-type radiation patterns over an octave band, for a single transducer element. The transducers measured mechanical Q is 8, coupling coefficient is 0.25, and electroacoustic efficiency is 80% and produced a source level of 215 dB re: 1 μPa at 1 m when driven at a field limit of 394 kV/m (10 kV/in.) at resonance. The uniqueness of this transducer is its directional beam patterns (directivity index=3.4 dB) and high acoustic output power from a small (less than a third of a wavelength) single element. Six of these transducers were placed in a closely packed line array two-wavelengths long. The array successfully produced narrow directional sound beams (directivity index=8.7 dB) with a front to back ratio greater than 30 dB and a source level of 225 dB re: 1 μPa at 1 m.
Modulations of detectable pulse response time spread in shallow water resulting from a combination of sound-speed variability and bottom loss
Authors: Monjo Charles L. , Nguyen Hien , Deferrari Harry A.
Published: July 2002

Reciprocal transmission tomography experiments in the Florida Straits have yielded a month-long time history of reciprocal pulse responses over three ranges approximately 22 km in length and 250 m in depth. A transmitted pulse of 8.75 ms in duration is spread out approximately 150 ms. The detectable time spread, or pulse width, is observed to vary by as much as 120 ms over time scales on the order of days. In a previous paper a strong correlation was reported between the sound-speed gradient at mid-depth and the total pulse width. A plausible explanation that changes in the sound-speed profile shape was causing the ray arrivals to focus and defocus in time was set forth as a hypothesis for this study, to be examined with range-dependent ray and PE models. The models predict a different and unexpected relation. Variations in the sound-speed profile from the average profile shape to a more convex profile increase the bottom grazing angle to the early arrivals. This results in an attenuation of the early arriving portion of the pulse below ambient noise and therefore an apparent narrowing of the pulse. Likewise, changes in the sound-speed profile from the average profile shape to a linear profile, produce smaller bottom grazing angles for the fastest arrivals, less loss, and an overall wider appearing pulse.
Linking auto- and cross-correlation functions with correlation equations: Application to estimating the relative travel times and amplitudes of multipath
Authors: Spiesberger John L.
Published: July 2002

A location problem is considered where the sound which propagates along multipath are impractical to model because the environment is poorly known. The acoustic bandwidth is assumed to be large enough so that the cross-correlation functions between pairs of receivers contain multiple peaks from multipath. The highest peak may not correspond to the difference in path lengths between the source and the receivers. Using similarities in the patterns of peaks in auto- and cross-correlation functions, an algorithm is developed to identify which cross-correlation peak corresponds to the difference in first arrivals, which can be used for locating the source if these arrivals are straight. The similarities are expressed with new “correlation equations.” The number of lag-type correlation equations is O(R2N2), where N is the typical number of multipath at each of R receivers. The correlation equations may be impractical to solve exactly. Accurate solutions are found in simulations for the numbers, relative travel times, and amplitudes of all the multipath with the aid of a new “augmented-template correlation function” which is a cross-correlation of nonnegative lags of an auto-correlation function with lags from a cross-correlation function. The technique relies on time series which are filtered to yield one dominant source.
Comparison of electrohydraulic lithotripters with rigid and pressure-release ellipsoidal reflectors. I. Acoustic fields
Authors: Bailey Michael R. , Blackstock David T. , Cleveland Robin O. , Crum Lawrence A.
Published: July 2002

The most common lithotripter, a Dornier HM-3, utilizes an underwater spark to generate an acoustic pulse and a rigid ellipsoidal reflector to focus the pulse on the kidney stone to be comminuted. The pulse measured in water with a PVDF membrane hydrophone at the external focus of the ellipsoid was a 1-μs positive-pressure spike followed by a 3-μs negative-pressure trough. When we replaced the rigid reflector in our experimental lithotripter with a pressure-release reflector, the pulse was a 1.6-μs trough followed by a 0.6-μs positive spike. The waveforms are nearly time inverses (i.e., their spikes and troughs are reversed). The frequency spectra, the maximum peak positive pressures P+ (42 MPa, rigid and 43 MPa, pressure-release), and the maximum peak negative pressures P− (−12 MPa and −14 MPa) are comparable. The maximum P− occurred 20 mm closer to the reflector than did the maximum P+, for both reflectors. However, the spatial maxima of the peak pressures (P+ and P−) produced by the pressure-release reflector were located 20 mm nearer to the reflector than those produced by the rigid reflector. Qualitative explanation of the waveforms and the location of pressure maxima as well as comparison to previous theoretical and experimental results is given. The alternate waveform produced by the pressure-release reflector may be a tool in determining the role of cavitation in lithotripsy because cavitation is highly sensitive to waveform.
Perception of microphone noise in hearing instruments
Authors: Lee Lidia W. , Geddes Earl R.
Published: July 2002

In a well-designed instrument the noise level is reduced until it is dominated by the front end noise. In a hearing instrument this is the microphone noise. This paper examines the perception of noise in a hearing instrument by both normal-hearing and hearing-impaired listeners. The noise levels are specified as input-referred values in one-third octave bands. Two sets of measurements, the just-objectionable level (JOL) and the just-audible level (JAL), were assessed in third octave bands from 250 to 5000 Hz. The data indicated that the use of a subjectively described acceptability of noise, JOL, is an unreliable measure due to a very large variability across listeners. It is recommended that mean values for the noise threshold level, the JAL, be used as a guide in the optimization of microphone noise design.
An improved moving frame acoustic holography for coherent bandlimited noise
Authors: Park Soon-Hong , Kim Yang-Hann
Published: July 2002

The moving frame acoustic holography method, which can increase the aperture size and spatial resolution of a hologram was recently proposed [H.-S. Kwon and Y.-H. Kim, J. Acoust. Soc. Am. 103, 1734–1742 (1998)]. This method continuously sweeps a stationary sound field by using a line array of microphones so that the hologram of a scanned plane can be obtained. This method enables us to visualize the noise generated by moving noise sources based on near-field acoustic holography. However, a drawback is that it can be applied only to sinusoidal components. This limits its practical application. In practice, bandlimited and transient noise, as well as a sinusoidal component, must be dealt with in order to effectively control the noise generated by the moving noise sources. This paper addresses a way to improve the moving frame acoustic holography method so that it can be applied not only to sinusoidal components, but also to a coherent bandlimited noise. The practical applicability of the improved method is also verified by experiments.
Active noise and vibration control for turboprop aircraft
Authors: Rohde Thomas , Borchers Ingo U. , Häusler Sigurd , Möser Michael
Published: July 2002

Interior noise in modern turboprop aircraft is a serious problem as it is directly related to passenger comfort, crew performance, and aircraft weight. For turboprop aircraft the most important noise sources are the propellers generating intense low-frequency noise which is, in general, difficult to reduce by passive measures. Therefore, extensive work has been conducted on active noise control using loudspeakers as secondary sources and microphones as error sensors. In addition, new control techniques have been investigated applying structural actuators for controlling the structural fuselage modes coupling to the critical acoustical modes. The present paper demonstrates the feasibility of using the new structural actuator technique in turboprop aircraft. Multiple piezoceramics have been attached to the structure of the Acoustic Test Cell (ATC) based on the Dornier 328 turboprop aircraft. The ceramics are driven according to a theoretical optimization process based on measured transfer functions. Noise reduction for the first three BPFs has been calculated and measured for different piezo configurations. The achieved results are compared and discussed. It is shown that the new technique of active vibration control is a powerful tool not only to control vibrations but also to significantly reduce the interior noise levels in modern turboprop aircraft.
Monostatic and bistatic reverberation statistics west of the Mid-Atlantic Ridge
Authors: Dorfman Yevgeniy Y. , Dyer Ira
Published: July 2002

Monostatic and bistatic reverberation of highly resolved signals from very rough bottoms at one site is statistically analyzed. Scattering at a mean frequency of about 230 Hz from a large number of bottom footprints is considered. The reverberation envelope is found to be non-Rayleigh, with the degree of departure from Rayleigh dependent upon the bottom grazing angle for two cases considered, θg≈5° and 40°, and upon the bistatic angle in the entire range, φ≈0° to 180°. These rough bottom observations can be explained by adopting a continuous scattering model having a Rayleigh envelope, added to a discrete scattering model (arising from a small number of individual features within the sonar footprint) having a distinctly non-Rayleigh envelope. These models, plus a heuristic mechanism of self-selection within the discrete scattering model, arguably explain the observed angle dependence of the reverberation statistics.
Waveform interactions and the segregation of concurrent vowels
Authors: de Cheveigné Alain
Published: July 2002

Two experiments investigated the effects of small values of fundamental frequency difference (ΔF0) on the identification of concurrent vowels. As ΔF0’s get smaller, mechanisms that exploit them must necessarily fail, and the pattern of breakdown may tell which mechanisms are used by the auditory system. Small ΔF0’s also present a methodological difficulty. If the stimulus is shorter than the beat period, its spectrum depends on which part of the beat pattern is sampled. A different starting phase might produce a different experimental outcome, and the experiment may lack generality. The first experiment explored the effects of ΔF0’s as small as 0.4%. The smallest ΔF0 conditions were synthesized with several starting phases obtained by gating successive segments of the beat pattern. An improvement in identification was demonstrated for ΔF0’s as small as 0.4% for all segments. Differences between segments (or starting phase) were also observed, but when averaged over vowel pairs they were of small magnitude compared to ΔF0 effects. The nature of ΔF0-induced waveform interactions and the factors that affect them are discussed in detail in a tutorial section, and the hypothesis that the improvement in identification is the result of such interactions (beat hypothesis) is examined. It is unlikely that this hypothesis can account for the effects observed. The reduced benefit of ΔF0 for identification at smaller ΔF0’s more likely reflects the breakdown of the same F0-guided segregation mechanism that operates at larger ΔF0’s.
Imaging in the ocean with ambient noise: the ORB experiments
Authors: Epifanio Chad L. , Potter John R. , Deane Grant B. , Readhead Mark L. , Buckingham Michael J.
Published: July 2002

Acoustic daylight imaging is a new technique that has been proposed for creating pictorial images of objects in the ocean from the ensonification provided by the incident ambient noise field. To investigate the feasibility of the technique, a series of experiments was performed from the research platform ORB, moored in San Diego Bay, Southern California. Central to these experiments was an acoustic receiver known as ADONIS (acoustic daylight ocean noise imaging system), which consists of a spherical reflector, 3 m in diameter, with an elliptical array of 130 hydrophones at the focal surface. This system, which is broadband, operating between 8 and 80 kHz, forms a total of 126 receive-only beams spanning the vertical and horizontal. The ambient noise power in each beam is mapped into a pixel on a VDU. Various types of targets were used in the experiments, including planar panels and cylindrical, polyethylene drums containing wet sand, seawater or syntactic foam (essentially air), and most of the experiments were conducted with the targets at ranges between 20 and 40 m. At the time of the experiments the noise field in the area was created primarily by snapping shrimp. Moving, color images of the object space were successfully created with ADONIS. Some representative static images from the moving sequences are presented and discussed in the paper.
Impedance-matched absorbers for finite-difference parabolic equation algorithms
Authors: Yevick David , Thomson David J.
Published: July 2002

In this paper, a perfectly matched layer (PML) absorber, recently introduced into the electromagnetic propagation literature by Bérenger [J. Comput. Phys. 114, 185–200 (1994)], is adapted for use with both paraxial and wide-angle acoustic parabolic equations (PEs). Our procedure incorporates an imaginary component into the transverse coordinate that mimics the introduction of a fictitious absorber on the edge of the computational grid. Use of such an impedance-matched layer can significantly reduce spurious reflections compared to physical absorbing layer methods and thus allows a smaller number of boundary points to be employed in PE calculations. Numerical results obtained with several higher-order propagator approximations confirm that such impedance-matched absorbers efficiently eliminate reflections.
Localized vibration modes in free anisotropic wedges
Authors: Shuvalov A. L. , Krylov V. V.
Published: July 2002

Propagation of flexural localized vibration modes along edges of anisotropic wedges is considered in the framework of the geometrical-acoustics approach. Its application allows for straightforward evaluation of the wedge-mode velocities in the general case of arbitrary elastic anisotropy. The velocities depend on the wedge apex angle and on the mode number in the same way as in the isotropic case, but there appears to be additional dependence on elastic coefficients. The velocities in tetragonal wedges (with the midplane orthogonal to the four-fold axis) and in “weakly” monoclinic wedges are explicitly calculated and analyzed. Bounds of the wedge-wave velocity variation in tetragonal materials are established.
Exact solutions to one-dimensional acoustic fields with temperature gradient and mean flow
Authors: Karthik B. , Kumar B. Manoj , Sujith R. I.
Published: July 2002

An exact solution for one-dimensional acoustic fields in ducts in the presence of an axial mean temperature gradient and mean flow is presented in this paper. The analysis is valid for mean Mach numbers such that the square of the mean Mach number is much less than one. The one-dimensional wave equation for ducts with axial mean temperature gradient and mean flow is derived. By appropriate transformations, the wave equation is reduced to an analytically solvable hypergeometric differential equation for the case of a linear mean temperature profile. The developed solution is applied to investigate the dependence of sound propagation in a duct on factors such as temperature gradient and mean flow. The results obtained using the analytical solution compare very well with the numerical results. The developed solution is also compared with an existing analytical solution.
Acoustically derived ice-fracture velocity in central Arctic pack ice
Authors: Stamoulis Catherine , Dyer Ira
Published: July 2002

Sounds radiated by fractures in Arctic ice (called acoustic events) are used to estimate fracture velocity. Both speed and orientation are obtained by measuring Doppler shifts induced by source motion. Data from the SIMI experiment of 1994 in the central Arctic are used in the frequency window 10 to 350 Hz. The estimation procedure assumes that each fracture propagates unilaterally, i.e., unidirectionally. Results for a population of 186 events show fracture propagation speed to be mostly subsonic, in the range 100 to 1100 m/s, significantly lower than the Rayleigh wave speed (1700 m/s for sea ice) assumed in previous studies. The wide range of speeds observed indicates either the presence of distinct multiple fractures in each event, or of a single mechanism at different stages in its propagation.
The Shear-Rate Dependence of Viscosity in Concentrated Solutions of Narrow-Distribution Polystyrene
Authors: Graessley William W. , Hazleton Ronald L. , Lindeman Louis R.
Published: July 2002

Viscosity was measured as a function of shear rate for a series of concentrated solutions of polystyrene in n-butyl benzene, using a plate-cone viscometer. The polymers had narrow distributions of molecular weight (Mw/Mn=1.01–1.20) with Mw ranging from 19,800 to 2,400,000. Polymer concentrations ranged from 0.20 to 0.55 g/cc and temperatures from 30 to 60°C. A master curve of reduced viscosity versus reduced shear rate was prepared and found to be similar to one recently predicted for monodisperse entangling polymers. An experimental relaxation time τ0 was deduced for each solution by superposition with the theoretical master curve. The values ranged from 0.0024 to 9.1 sec and were always of the order of the Rouse relaxation time, τr=(6/π2)(η0M/cRT), calculated for the solution. Residual variations in the ratio τ0/τr with both concentration and molecular weight were noted however, although a single curve was formed when τ0/τr was plotted as a function of the product cM. This suggested that the number of chain entanglements per molecule influences the course of the relaxation process. A very simple equation correlated all the data, yielding τ0=(const.) η0M/cT at low values of the entanglement density and τ0=(const.) η0/c2T at high values.
Intrinsic Errors for Pressure Measurements in a Slot along a Flow
Authors: Kearsley Elliot A.
Published: July 2002

Any rectilinear flow dynamically possible for a Newtonian fluid is shown to be possible also for a second order fluid. The stress which satisfies the condition of equilibrium is explicitly calculated. The component of stress normal to a wall bounding a shear flow is expressed in terms of the reading of a pressure gauge connected to a narrow slot in the wall, oriented in the direction of flow.
The Bulk Response of Viscoelastic Solids
Authors: Nunziato J. W. , Schuler K. W. , Walsh E. K.
Published: July 2002

Here the dilatational response of polymeric solids is considered. Such response is an important factor in the description of many dynamic situations including shock and acceleration wave propagation. Since such materials exhibit both instantaneous and equilibrium elasticity, as well as rate-effects, it is assumed that polymers can be characterized as finite linear viscoelastic solids and their dilatational behavior is described in terms of an instantaneous and equilibrium hydrostat. These functions represent the bulk response to hydrostatic loads applied over very short and very long time periods; and here a technique for determining these functions from quasi-static and ultrasonic wave propagation experiments is presented. To illustrate the results, the instantaneous and equilibrium hydrostats are given for the solid polymer, polymethyl methacrylate.
The Effect of Strain History on the Crystallization Behavior of Bulk Poly(ethylene Terephthalate)
Authors: Spruiell J. E. , McCord D. E. , Beuerlein R. A.
Published: July 2002

The crystallization of bulk tensile samples of glassy, amorphous poly(ethylene terephthalate) was studied as a function of various deformation and annealing treatments. Per cent crystallinity, orientation function, crystallite size, and long period spacing were measured to characterize the samples. Crystallization, necking, and orientation occurred during straining when, at a given temperature, the strain rate was sufficient to generate a critical stress level within the material. During subsequent annealing crystallization was nucleated by the crystallites formed during deformation. The observed behavior was consistent with a model proposed by Dismore and Statton for drawn nylon 66 yarns and which was previously discussed by Dumbleton for the case of poly(ethylene terephthalate).
Flow Instabilities in a Capillary Rheometer for an Elastic Polymer Solution
Authors: Rama Murthy A. V.
Published: July 2002

A modified capillary rheometer and a motion-picture camera are used to simultaneously record the pressure at the inlet to the tube, the flow rate through the tube, and the flow patterns in the barrel prior to the entry to the tube. Measured flow curves, employing tubes in the range 14.7⩽L/D⩽36.7 for a medicinal grade liquid paraffin in the range 200⩽γ⩽4000 sec−1 and a highly elastic solution of Separan AP 30 in the range 100⩽γ⩽1500 sec−1, agreed well with the data obtained using a Haake Rotovisco cup and bob viscometer. Motion pictures of the flow patterns in the barrel for the Separan solution showed that the stable converging flow field at low flow rates developed a spiraling instability whose intensity increased with increasing flow rates until a complete breakdown of the flow field occurred at high flow rates prior to a second stage stability. Representative flow patterns in the range 40⩽4Q/ΠR3⩽5154 sec−1 are presented for L/D=36.7 which show the behavior over the entire spectrum of shear rates including the second-stage stability. The similarities of the flow patterns to those observed for polymer melts during extrusion are discussed in detail.
Small and large deformation studies of protein gels
Authors: Stading Mats , Langton Maud , Hermansson Anne-Marie
Published: July 2002

The rheological behavior of protein gels with different network and strand structures has in a series of studies been investigated to elucidate how the structure of the gel influences its rheological properties. Nondestructive viscoelastic measurements and fracture techniques were used and the different types of structures studied were fine-stranded gels and particulate gels. The influence of spatial inhomogeneities in the network structure was also investigated. The protein gel chosen as the model system was β-lactoglobulin which forms gels on heating and develops different structures depending on pH: a particulate network at intermediate pH (4–6) and a fine-stranded network below and above this interval. It can also form inhomogeneous networks depending on pH or heating rate. The fine-stranded and the particulate gels had totally different mechanical properties. It was shown that the strand structure influenced both the modulus as well as the fracture properties of both fine-stranded and particulate gels. Inhomogeneities induced by a slow heating rate also changed the mechanical properties the gels.
Rheology and phase separation in a model upper critical solution temperature polymer blend
Authors: Vlassopoulos D. , Koumoutsakos A. , Anastasiadis S. H. , Hatzikiriakos S. G. , Englezos P.
Published: July 2002

The viscoelastic properties of a model binary polymer blend exhibiting an upper critical solution temperature phase diagram were investigated by utilizing small amplitude oscillatory and steady shear measurements. A mixture of unentangled monodisperse polystyrene and poly(phenyl methyl siloxane), exhibiting Newtonian shear viscosity, was used, and its phase diagram was established by turbidity and dynamic light scattering measurements. In the miscible region, the concentration dependence of the viscosity was adequately described by a mixing rule accounting for the surface fractions instead of volume fractions. Near the phase separation temperature and far from the glass transition, critical concentration fluctuations dominated the linear viscoelastic response and were responsible for the observed thermorheological complexity. An appropriate quantitative account of these fluctuations resulted in the accurate rheological determination of both the binodal and spinodal temperatures, extending thus the applicability of the relevant procedure earlier applied to lower critical solution temperature blends involving higher molecular weight entangled polymers. In the phase separated regime, the normal stress of the dispersed phase undergoing spinodal decomposition followed a recent scaling proposed for molecular mixtures with large viscosity difference.
Accurate simulation of linear viscoelastic properties by variance reduction through the use of control variates
Authors: Wagner Norman J. , Öttinger Hans Christian
Published: July 2002

An algorithm is demonstrated to yield accurate linear viscoelastic properties in a nonequilibrium stochastic simulation by variance reduction. For noninteracting polymer dumbbells, multiple orders of magnitude improvements in computational accuracy for nonequilibrium viscoelastic properties are easily realized. This simple and robust control variate scheme uses control variables defined as the viscoelastic properties obtained from a parallel, equilibrium simulation. Results for strongly interacting colloidal particles demonstrate some advantages as well as limitations of the method.
Electrorheological effect in immiscible polymer blends
Authors: Tajiri Kozo , Ohta Keiichi , Nagaya Tomoyuki , Orihara Hiroshi , Ishibashi Yoshihiro , Doi Masao , Inoue Akio
Published: July 2002

A new model of the electrorheological (ER) effect for immiscible polymer blends is proposed on the basis of microscopic observations. In the absence of an electric field the polymer with high viscosity is dispersed as droplets in the other polymer with low viscosity, while in the presence of an electric field, the droplets stretch and coalesce to form bridges between electrodes, resulting in the increase of the macroscopic viscosity. A few experimental results are given to confirm the validity of this model.
CD44‐Targeting Drug Delivery System of Exosomes Loading Forsythiaside A Combats Liver Fibrosis via Regulating NLRP3‐Mediated Pyroptosis
Authors: Gong Lihong , Zhou Honglin , Zhang Shenglin , Wang Cheng , Fu Ke , Ma Cheng , Zhang Yafang , Peng Cheng , Li Yunxia
Published: January 2023

Liver fibrosis is a progressive pathological process induced by various stimuli and may progress to liver cirrhosis and cancer. Forsythiaside A (FA) is an active ingredient extracted from traditional Chinese medicine Forsythiae Fructus and has prominent hepatoprotective activities. However, the unsatisfactory pharmacokinetic properties restrict its clinical application. In this study, the nanocarrier of CD44‐specific ligand Hyaluronic acid (HA)‐modified milk‐derived exosomes (mExo) encapsulated with FA (HA‐mExo‐FA) is developed. As a result, HA modification could deliver drug‐loaded exosomes to the target cells and form a specific ligand‐receptor interaction with CD44, thus improving the anti‐liver fibrosis effect of FA. In vitro findings indicate that HA‐mExo‐FA could inhibit TGF‐β1‐induced LX2 cell proliferation, reduce α‐SMA and collagen gene and protein levels, and promote the apoptosis of activated LX2 cells. In vivo results demonstrate that HA‐mExo‐FA could improve liver morphology and function changes in zebrafish larvae. The anti‐liver fibrosis mechanism of HA‐mExo‐FA may be attributed to the inhibition of NLRP3‐mediated pyroptosis. In addition, the effect of HA‐mExo‐FA on TAA‐induced increase in NLRP3 production is attenuated by NLRP3 inhibitor MCC950. Collectively, this study demonstrates the promising application of HA‐mExo‐FA in drug delivery with high specificity and provides a powerful and novel delivery platform for liver fibrosis therapy.
Y‐Type Non‐Fullerene Acceptors with Outer Branched Side Chains and Inner Cyclohexane Side Chains for 19.36% Efficiency Polymer Solar Cells
Authors: Deng Min , Xu Xiaopeng , Duan Yuwei , Yu Liyang , Li Ruipeng , Peng Qiang
Published: January 2023

Raising the lowest unoccupied molecular orbital (LUMO) energy level of Y‐type non‐fullerene acceptors can increase the open‐circuit voltage (Voc) and thus the photovoltaic performance of the current top performing polymer solar cells (PSCs). One of the viable routes is demonstrated by the successful Y6 derivative of L8‐BO with the branched alkyl chains at the outer side. This will introduce steric hindrance and reduce intermolecular aggregation, thus open up the bandgap and raise the LUMO energy level. To take further advantages of the steric hindrance influence on optoelectronic properties of Y6 derivatives, two Y‐type non‐fullerene acceptors of BTP‐Cy‐4F and BTP‐Cy‐4Cl are designed and synthesized by adopting outer branched side chains and inner cyclohexane side chains. An outstanding Voc of 0.937 V is achieved in the D18:BTP‐Cy‐4F binary blend devices along with a power conversion efficiency (PCE) of 18.52%. With the addition of BTP‐eC9 to extend the absorption spectral coverage, a remarkable PCE of 19.36% is realized finally in the related ternary blend devices, which is one of the highest values for single‐junction PSCs at present. The results illustrate the great potential of cyclohexane side chains in constructing high‐performance non‐fullerene acceptors and their PSCs.
Mutant KRAS Drives Immune Evasion by Sensitizing Cytotoxic T‐Cells to Activation‐Induced Cell Death in Colorectal Cancer
Authors: Liu Huashan , Liang Zhenxing , Cheng Sijing , Huang Liang , Li Wenxin , Zhou Chi , Zheng Xiaobin , Li Shujuan , Zeng Ziwei , Kang Liang
Published: January 2023

The roles of oncogenic KRAS in tumor immune evasion remain poorly understood. Here, mutant KRAS is identified as a key driver of tumor immune evasion in colorectal cancer (CRC). In human CRC specimens, a significant reduction in cytotoxic CD8+ T‐cell tumor infiltration is found in patients with mutant versus wild type KRAS. This phenomenon is confirmed by preclinical models of CRC, and further study showed KRAS mutant tumors exhibited poor response to anti‐PD‐1 and adoptive T‐cell therapies. Mechanistic analysis revealed lactic acid derived from mutant KRAS‐expressing tumor cells sensitized tumor‐specific cytotoxic CD8+ T‐cells to activation‐induced cell death via NF‐κB inactivation; this may underlie the inverse association between intratumoral cytotoxic CD8+ T‐cells and KRAS mutation. Importantly, KRAS mutated tumor resistance to immunotherapies can be overcome by inhibiting KRAS or blocking lactic acid production. Together, this work suggests the KRAS‐mediated immune program is an exploitable therapeutic approach for the treatment of patients with KRAS mutant CRC.
Anisotropic Growth of Centimeter‐Size CsCu2I3 Single Crystals with Ultra‐Low Trap Density for Aspect‐Ratio‐Dependent Photodetectors
Authors: Han Sancan , Quan Jiale , Wang Ding , Li Huijun , Liu Xinya , Xu Jingcheng , Zhang Yixin , Li Ziqing , Wu Limin , Fang Xiaosheng
Published: January 2023

Low‐dimensional ternary copper iodide metal halide with strong quantum confinement effects has made great progress in optoelectronic fields. However, efficient regulation of anisotropic growth of metal halides single crystal still remains a great challenge. Herein, 2 cm size CsCu2I3 single crystals with tunable aspect ratio and the trap states (ntrap) as low as 5.38 × 109 cm−3 are fabricated by optimized anti‐solvent vapor‐assisted method, in which the growth cycle is shortened by half. Evidenced by real‐time observation and the LaMer growth model, the rapid and anisotropic growth mechanism is ascribed to preferential 1D growth, promoted by high concentration and fast vapor rate. Furthermore, the aspect‐ratio‐dependent optoelectronic performance is observed, the on–off ratio for 2 cm CsCu2I3 single crystal are enhanced 350 times compared with those of short and thick single crystal, which shows ultrahigh on‐off ratio of 1570, D* of 1.34 × 1012 Jones, Rλ of 276.94 mA W−1, t rise /t decay of 0.37 and 1.08 ms, and EQE of 95.53%, which are clearly at very high level among lead‐free perovskite‐based photodetectors. This study not only provides a new strategy for overcoming anisotropic growth limitations of low‐dimensional metal halides, but also paves a way for high‐performance optoelectronic applications.
Effective SEI Formation via Phosphazene‐Based Electrolyte Additives for Stabilizing Silicon‐Based Lithium‐Ion Batteries
Authors: Ghaur Adjmal , Peschel Christoph , Dienwiebel Iris , Haneke Lukas , Du Leilei , Profanter Laurin , Gomez‐Martin Aurora , Winter Martin , Nowak Sascha , Placke Tobias
Published: January 2023

Silicon, as potential next‐generation anode material for high‐energy lithium‐ion batteries (LIBs), suffers from substantial volume changes during (dis)charging, resulting in continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), as well as from consumption of electrolyte and active lithium, which negatively impacts long‐term performance and prevents silicon‐rich anodes from practical application. In this work, fluorinated phosphazene compounds are investigated as electrolyte additives concerning their SEI‐forming ability for boosting the performance of silicon oxide (SiOx)‐based LIB cells. In detail, the electrochemical performance of NCM523 || SiOx/C pouch cells is studied, in combination with analyses regarding gas evolution properties, post‐mortem morphological changes of the anode electrode and the SEI, as well as possible electrolyte degradation. Introducing the dual‐additive approach in state‐of‐the‐art electrolytes leads to synergistic effects between fluoroethylene carbonate and hexafluorocyclotriphosphazene‐derivatives (HFPN), as well as enhanced electrochemical performance. The formation of a more effective SEI and increased electrolyte stabilization improves lifetime and results in an overall lower cell impedance. Furthermore, gas chromatography‐mass spectrometry measurements of the aged electrolyte with HFPN‐derivatives as an additive compound show suppressed ethylene carbonate and ethyl methyl carbonate decomposition, as well as reduced trans‐esterification and oligomerization products in the aged electrolyte.
No association between developmental instability as a general measure of stress and2D:4Ddigit ratios in a non‐western sample
Authors: Ertuğrul Berna , Aydık Muhammet Fatih
Published: January 2023

Objective

Random deviation from perfect symmetry of organisms is defined as fluctuating asymmetry. Fluctuating asymmetry is widely considered to be a marker of developmental instability, developmental noise and phenotypic quality at the population level. In this study, we investigated hypothesized relationship between 2D:4D digit ratios as a proxy measure of prenatal sex hormones and developmental instability levels in young adult humans.

Materials and Methods

In the study, seven bilateral traits were measured for fluctuating asymmetry, as well as second and fourth digit lengths on both hands of 185 individuals, 87 men (mean age: 22.42 ± 3.37) and 97 women (mean age: 22.88 ± 3.87). The second digit length was divided by the fourth digit length and the resulting value was used as the digit ratio (2D:4D). Composite fluctuating asymmetry was calculated using five bilateral traits displaying fluctuating asymmetry.

Results

Only the right hand 2D:4D ratio is lower in men than in women. However, this difference disappears when the effect of digit lengths is controlled. Composite fluctuating asymmetry results reveal that men are more asymmetrical than women. There was no significant relationship between digit ratios and composite fluctuating asymmetry.

Conclusion

In this study, the 2D:4D digit ratios appear to be influenced (at least in humans) by different digit lengths. This study also confirms previous studies that digit ratios as a proxy measure of exposure to either high testosterone or estrogen levels during early development does not appear to affect levels of developmental instability.
Iridium‐Catalyzed ortho‐Selective Borylation of Aromatic Amides Enabled by 5‐Trifluoromethylated Bipyridine Ligands
Authors: Marcos‐Atanes Daniel , Vidal Cristian , Navo Claudio D. , Peccati Francesca , Jiménez‐Osés Gonzalo , Mascareñas José L.
Published: January 2023

Iridium‐catalyzed borylations of aromatic C−H bonds are highly attractive transformations because of the diversification possibilities offered by the resulting boronates. These transformations are best carried out using bidentate bipyridine or phenanthroline ligands, and tend to be governed by steric factors, therefore resulting in the competitive functionalization of meta and/or para positions. We have now discovered that a subtle change in the bipyridine ligand, namely, the introduction of a CF3 substituent at position 5, enables a complete change of regioselectivity in the borylation of aromatic amides, allowing the synthesis of a wide variety of ortho‐borylated derivatives. Importantly, thorough computational studies suggest that the exquisite regio‐ and chemoselectivity stems from unusual outer‐sphere interactions between the amide group of the substrate and the CF3‐substituted aryl ring of the bipyridine ligand.
Ultrathin CuF2‐Rich Solid‐Electrolyte Interphase Induced by Cation‐Tailored Double Electrical Layer toward Durable Sodium Storage
Authors: Song Keming , Wang Xiang , Xie Zhengkun , Zhao Zhiwei , Fang Zhe , Zhang Zhengfeng , Luo Jun , Yan Pengfei , Peng Zhangquan , Chen Weihua
Published: January 2023

Solid‐electrolyte interphase (SEI) seriously affects battery's cycling life, especially for high‐capacity anode due to excessive electrolyte decomposition from particle fracture. Herein, we report an ultrathin SEI (3–4 nm) induced by Cu+‐tailored double electrical layer (EDL) to suppress electrolyte consumption and enhance cycling stability of CuS anode in sodium‐ion batteries. Unique EDL with SO3CF3‐Cu complex absorbing on CuS in NaSO3CF3/diglyme electrolyte is demonstrated by in situ surface‐enhanced Raman, Cyro‐TEM and theoretical calculation, in which SO3CF3‐Cu could be reduced to CuF2‐rich SEI. Dispersed CuF2 and F‐containing compound can provide good interfacial contact for formation of ultrathin and stable SEI film to minimize electrolyte consumption and reduce activation energy of Na+ transport. As a result, the modified CuS delivers high capacity of 402.8 mAh g−1 after 7000 cycles without capacity decay. The insights of SEI construction pave a way for high‐stability electrode.