bluuebunny/crossref_metadata_2025 huggingface dataset:
A working mechanical model for first- and second-order phase transitions and the cusp catastrophe
Authors: Mancuso Richard V.
Published: July 2002

We have modified a toy to demonstrate first- and second-order phase transitions. The toy consists of a ball constrained to move on a rotating hoop. Analysis of the equilibrium positions of the ball as a function of the angular velocity and location of the axis of rotation shows that this system contains a cusp catastrophe.
Analysis of a water-propelled rocket: A problem in honors physics
Authors: Finney G. A.
Published: July 2002

The air-pumped, water-propelled rocket is a common child’s toy, yet forms a reasonably complicated system when carefully analyzed. A lab based on this system was included as the final laboratory project in the honors version of General Physics I at the USAF Academy. The numerical solution for the height of the rocket is presented, as well as several analytic approximations. Five out of six lab groups predicted the maximum height of the rocket within experimental error.
Education in a rapidly advancing technology: Accelerators and beams
Authors: Month Mel
Published: July 2002

The field of accelerators and beams (A&B) is one of today’s fast changing technologies. Because university faculties have not been able to keep pace with the associated advancing knowledge, universities have not been able to play their traditional role of educating the scientists and engineers needed to sustain this technology for use in science, industry, commerce, and defense. This problem for A&B is described and addressed. The solution proposed, a type of “distance” education, is the U.S. Particle Accelerator School (USPAS) created in the early 1980s. USPAS provides the universities with a means of serving the education needs of the institutions using A&B, primarily but not exclusively the national laboratories. The field of A&B is briefly summarized. The need for education outside the university framework, the raison d’être for USPAS, the USPAS method, program structure, and curriculum, and particular USPAS–university connections are explained. The management of USPAS is analyzed, including its unique administrative structure, its institutional ties, and its operations, finance, marketing, and governmental relations. USPAS performance over the years is documented and a business assessment is made. Finally, there is a brief discussion of the future potential for this type of educational program, including possible extrapolation to new areas and/or different environments, in particular, its extra-government potential and its international possibilities.
Areas of the event horizon and stationary limit surface for a Kerr black hole
Authors: Pickett C. A. , Zund J. D.
Published: July 2002

We present an elementary evaluation of the surface areas of the event horizon and stationary limit surface for an uncharged Kerr black hole. The latter appears not to have been previously given in the literature, and permits us to suggest new geometrical/physical interpretations of these areas.
Observation of nonlinear acoustic effects at isotropic solid–solid interfaces
Authors: Chen Jianjun , Jiang Wenhua , Shui Yongan
Published: July 2002

The second harmonic generation of SV shear waves at isotropic solid–solid interfaces is experimentally studied. The amplitude of shear waves is measured for the interfaces of glass–air, glass–iron, glass–copper, and glass–aluminum. The measured angular relation of amplitude of the second harmonic wave is compared with theory and the agreement is reasonably good. The influence of the physical state of the interface on second harmonic generation is also observed. It is found that the second harmonic generation is sensitive to the interface state.
Influence of fundamental frequency on stop-consonant voicing perception: A case of learned covariation or auditory enhancement?
Authors: Holt Lori L. , Lotto Andrew J. , Kluender Keith R.
Published: July 2002

For stimuli modeling stop consonants varying in the acoustic correlates of voice onset time (VOT), human listeners are more likely to perceive stimuli with lower f0’s as voiced consonants—a pattern of perception that follows regularities in English speech production. The present study examines the basis of this observation. One hypothesis is that lower f0’s enhance perception of voiced stops by virtue of perceptual interactions that arise from the operating characteristics of the auditory system. A second hypothesis is that this perceptual pattern develops as a result of experience with f0-voicing covariation. In a test of these hypotheses, Japanese quail learned to respond to stimuli drawn from a series varying in VOT through training with one of three patterns of f0-voicing covariation. Voicing and f0 varied in the natural pattern (shorter VOT, lower f0), in an inverse pattern (shorter VOT, higher f0), or in a random pattern (no f0-voicing covariation). Birds trained with stimuli that had no f0-voicing covariation exhibited no effect of f0 on response to novel stimuli varying in VOT. For the other groups, birds’ responses followed the experienced pattern of covariation. These results suggest f0 does not exert an obligatory influence on categorization of consonants as [VOICE] and emphasize the learnability of covariation among acoustic characteristics of speech.
Scattering from a partially fluid-filled, elastic-shelled sphere
Authors: Fawcett J. A.
Published: July 2002

In this article a sphere is taken to be partially filled with fluid so that its interior is part fluid and part air. A set of basis of functions, based upon an origin at the fluid/air interface, is used for the interior and a set of basis functions based upon the center of the sphere is used for the shell and exterior of the sphere. These sets of basis functions are coupled at the shell/interior interface and the resulting coupled system of equations solved to yield the scattered field. Numerical computations using this approach are presented for varying amounts of fluid-fill and for varying incident plane waves.
Ultrasound detection by clupeiform fishes
Authors: Mann David A. , Higgs Dennis M. , Tavolga William N. , Souza Marcy J. , Popper Arthur N.
Published: July 2002

It has previously been shown that at least one species of fish (the American shad) in the order clupeiforms (herrings, shads, and relatives) is able to detect sounds up to 180 kHz. However, it has not been clear whether other members of this order are also able to detect ultrasound. It is now demonstrated, using auditory brainstem response (ABR), that at least one additional species, the gulf menhaden (Brevoortia patronus), is able to detect ultrasound, while several other species including the bay anchovy (Anchoa mitchilli), scaled sardine (Harengula jaguana), and Spanish sardine (Sardinella aurita) only detect sounds to about 4 kHz. ABR is used to confirm ultrasonic hearing in the American shad. The results suggest that ultrasound detection may be limited to one subfamily of clupeiforms, the Alosinae. It is suggested that ultrasound detection involves the utricle of the inner ear and speculate as to why, despite having similar ear structures, only one group may detect ultrasound.
An adaptive decentralized multiuser receiver for deep-water acoustic telemetry
Authors: Zvonar Zoran , Brady David , Catipovic Josko
Published: July 2002

An acoustic local area network has been deployed for multipoint-to-point telemetry between ocean bottom sensors and a surface receiver in deep-water areas. A major obstacle for coherent communications in this channel is strong multiple-access interference from other acoustic modems, which affects a common narrowband request channel of the network protocol. The network throughput and packet delay depend on the capability of the receiver to resolve collisions between request packets. In this paper a multiuser receiver for joint channel parameter estimation, multiple-access interference suppression and signal detection is proposed. The receiver is fully adaptive, requiring no side information about the channel conditions or the signal parameters of the interfering users in the network. Receiver performance is demonstrated through experiments in a deep-water acoustic channel.
Response to “Comments on ‘Analysis of the numerically implemented angular spectrum approach based on the evaluation of two-dimensional acoustic fields. Part I and Part II”’ [J. Acoust. Soc. Am. 101, 3800 (1997)]
Authors: Wu Ping , Kazys Rymantas , Stepinski Tadeusz
Published: July 2002

The authors respond to the comments of Assaad and Rouvaen.
Group velocity formulas for the symmetry planes of a stressed anisotropic elastic solid
Authors: Yul Kim Kwang , Wu Tsung-Tsong , Sachse Wolfgang
Published: July 2002

This paper presents analytic formulas for the group velocity of quasilongitudinal, quasitransverse, and shear-horizontally (SH) polarized pure-transverse modes propagating in an arbitrary direction on the symmetry planes of a stressed anisotropic elastic medium with orthotropic or higher symmetry. The group velocity equations are expressed in terms of the thermodynamic elastic stiffness coefficients and stresses acting on the medium. An example is provided with a (001) silicon crystal compressed at uniaxial stress.
Transient wave propagation in a circular annulus subjected to transient excitation on its outer surface
Authors: Liu Guoli , Qu Jianmin
Published: July 2002

The objective of this work is to investigate the propagation of guided transient waves in the circumferential direction of annular structural components. For this purpose, a two-dimensional circular annulus is considered. It is assumed that the inner surface of the annulus is traction free and the outer surface of the annulus is subjected to a time-dependent transient excitation. The guided circumferential waves induced by this transient excitation are studied in detail to understand the propagation characteristics of various wave modes. The method of eigenfunction expansion is used to solve the transient wave propagation problem. To this end, the problem of time harmonic, steady-state circumferential waves is solved first as the eigenfunctions. The time-dependent response of the annulus is then obtained by superimposing all eigenfunctions over all possible frequencies. Several numerical examples are given to illustrate the method of solution and to provide some guidelines on using guided waves to detect radial cracks in annular structural components.
The arccos and Lommel formulations—Approximate closed-form diffraction corrections
Authors: Daly Charles J. , Rao N. A. H. K
Published: July 2002

A closed-form frequency-domain formalism for spatially integrated diffraction corrections is proposed. Spatially integrated diffraction corrections are necessary when trying to characterize material with ultrasonic probing. In the case of piston transducers and point receivers, the Lommel diffraction formulation is used when the excitation is monochromatic, and the arccos diffraction formulation is used when the excitation is impulsive. The Lommel and arccos formulations are usually treated separately; here, they are connected. Specifically, the arccos diffraction formulation and Lommel diffraction formulation are shown to form an approximate Fourier transform pair. Since the Lommel formulation is amenable to closed-form spatial integration, Lommel functions are used to derive diffraction corrections for unfocused piston transducers operating in receiveonly (one-way) mode or transmit/receive (two-way) mode. Results obtained from the proposed closed-form frequency-domain formalism are qualitatively compared with results based on the closed-form time-domain or impulse-response formalism. It will be shown that the proposed frequency-domain formalism has theoretical and practical value. Finally, specific computational considerations are discussed as necessary.
Working gases in thermoacoustic engines
Authors: Belcher James R. , Slaton William V. , Raspet Richard , Bass Henry E. , Lightfoot Jay
Published: July 2002

The best working gases for thermoacoustic refrigeration have high ratios of specific heats and low Prandtl numbers. These properties can be optimized by the use of a mixture of light and heavy noble gases. In this paper it is shown that light noble gas–heavy polyatomic gas mixtures can result in useful working gases. In addition, it is demonstrated that the onset temperature of a heat driven prime mover can be minimized with a gas with large Prandtl number and small ratio of specific heats. The gas properties must be optimized for the particular application of thermoacoustics; it cannot be assumed that high specific heat ratio and low Prandtl number are always desirable.
Influence of visco-inertial effects on the ultrasonic properties of monodisperse silica suspensions
Authors: Herrmann Norbert , McClements D. Julian
Published: July 2002

The measured ultrasonic velocity and attenuation spectra (0.5–150 MHz) of colloidal suspensions containing monodisperse silica particles (φ=5%, r=190 nm) dispersed in a series of water–glycerol mixtures (0% to 80% glycerol) were in good agreement with predictions of multiple scattering theory. The major cause of excess attenuation and velocity dispersion was visco-inertial dissipation losses, which arose because of the density contrast between the silica particles and surrounding liquid. There was a maximum in the attenuation spectra that decreased in height and shifted to higher frequencies as the glycerol concentration was increased because of the reduction in density contrast and increase in continuous phase viscosity (1 to 60 mPa.s). These results suggest that ultrasound could be used to measure continuous phase viscosities in colloidal suspensions.
Loss mechanisms in piezoelectrics and resonance/antiresonance
Authors: Uchino Kenji , Zheng Jiehui , Chen Yun-Han , Du Xiaohang , Hirose Seiji
Published: July 2002

Losses in piezoelectrics are considered in general to have three different mechanisms: dielectric, mechanical and piezoelectric losses. This paper deals with the phenomenology of losses, first, then how to measure these losses experimentally. We will discuss two methods for measuring the electrical, mechanical, and piezoelectric coupling losses separately: (1) strain versus stress and field and displacement versus stress and field curves, and (2) a resonance/antiresonance technique. Also, one can measure heat generation at an off-resonance frequency to obtain a total loss. By combining the above methods, we can investigate the loss mechanisms in practical piezoelectric materials and their consequences in devices. It will be shown that heat generation is caused mainly by the dielectric loss, not by the mechanical loss. Furthermore, a drastic decrease in mechanical Q with an increase of vibration level is observed in resonant piezoelectric ceramic devices, a result not observable using conventional impedance analyzers at low power. Based on this loss knowledge, we will discuss the differing situations between piezoelectric resonance and antiresonance states. In particular, since the mechanical quality factor at an antiresonance frequency is larger than that at a resonance frequency the antiresonance mode seems to be superior for high-power applications.
Viscoelastic shear properties of human vocal fold mucosa: Theoretical characterization based on constitutive modeling
Authors: Chan Roger W. , Titze Ingo R.
Published: July 2002

The viscoelastic shear properties of human vocal fold mucosa (cover) were previously measured as a function of frequency [, J. Acoust. Soc. Am. 106, 2008–2021 (1999)], but data were obtained only in a frequency range of 0.01–15 Hz, an order of magnitude below typical frequencies of vocal fold oscillation (on the order of 100 Hz). This study represents an attempt to extrapolate the data to higher frequencies based on two viscoelastic theories, (1) a quasilinear viscoelastic theory widely used for the constitutive modeling of the viscoelastic properties of biological tissues [Biomechanics (Springer-Verlag, New York, 1993), pp. 277–292], and (2) a molecular (statistical network) theory commonly used for the rheological modeling of polymeric materials [24, 1007–1018 (1991)]. Analytical expressions of elastic and viscous shear moduli, dynamic viscosity, and damping ratio based on the two theories with specific model parameters were applied to curve-fit the empirical data. Results showed that the theoretical predictions matched the empirical data reasonably well, allowing for parametric descriptions of the data and their extrapolations to frequencies of phonation.
Drop Shapes in Shear from a Second-Order Theory
Authors: Turner Brian M. , Chaffey Charles E.
Published: July 2002

The recent second-order theory of Chaffey and Brenner for the deformation of a drop suspended in an immiscible liquid undergoing slow steady shear flow has a narrow range of validity. The deformation parameter DI (proportional to the product of the velocity gradient, the drop radius, the suspending liquid’s viscosity and the reciprocal of the interfacial tension) must be less than 0.24 if the predicted deformation of drops of low viscosity in Couette flow is to be realistic; for highly viscous drops DI must not exceed 0.1. For all drops in hyperbolic flow and hyperbolic-radial flow DI must be less than 0.22 and 0.24, respectively. The second-order approximation, DII, to the observable deformation ratio D (the difference between the drop’s length and width, divided by their sum) exceeds DI for viscous drops in Couette flow but is slightly smaller than DI for drops of low viscosity. Calculated values of DII deviate from experimental data on D. The second-order theory does predict the lengthening in hyperbolic flow of one drop axis and the shortening of the other two. A new first-order theory by Cox has a much wider range of validity but does not conflict with the second-order theory.
Resistance of Erythrocyte Flow into Pores
Authors: Blackshear Perry L. , Christianson Todd J. , Majerle Randall J. , Vargas Fernando F.
Published: July 2002

A method is presented for filtering dilute red blood cell suspensions through polycarbonate filters which avoids buildup of deposits on the pores and allows the determination of relative resistance of flow, with and without cells. In the small size range (pores 2.6–3 μm), the relative resistance falls from a high value at low ΔPs to an asymptotic value that depends on hematocrit at high ΔP. Using a model for cell flow in the pores, an estimate for the apparent membrane viscosity is attained which is a function of shear rate. The large pore sieves (4.15–5 μm) displayed little sensitivity of relative resistance to imposed ΔP. The possible importance of the results for understanding precapillary sphincter control of red blood cell distribution in capillary beds is discussed.
The measurement of viscosity by tuning-fork vibration mechanism (abstract)
Authors: Ishiwata Shosuke , Hayashi Mitsuro , Ohshima Hideaki , Suzuki Osamu
Published: July 2002

We developed an unique device for measuring the viscosity of the liquids, using the mechanism of the tuning-fork vibration. This device has a pair of plate springs with a circular plate mounted on the end. When a pair of circular plates is operated in a sample by a resonance vibration in a reverse phase at a constant frequency, its amplitude is inversely proportional to the viscosity of the sample. So the viscosity can be obtained by measuring the amplitude. This device uses the standard liquid for calibration, and stores the calibration curve of the relationship between the amplitude value and the viscosity of standard sample. The rheological complicated materials can also be characterized by using this device.
Thermal conductivity and flocculated structure of suspension of carbon black (abstract)
Authors: Wei Xianfu , Amari Takeshi , Watanabe Koichiro
Published: July 2002

A modified concentric cylinder viscometer was used for the simultaneous measurement of thermal conductivity and apparent viscosity. The thermal conductivity of disperse medium is 100 times higher than that of carbon black particles, suggesting the particles behave as obstacles to thermal conductance. In flow field, heat transfer is mainly caused by forced convection and the effect of particle orientation on the thermal conductivity of the system becomes large. After cessation of shear flow, the thermal conductivity decreases drastically depending on the rate of shear before the cessation of flow, and recovers gradually with elapsed time. The process of thermal conductance at rest state is by radiation. The thermal conductivity of the disperse system where the particles are dispersed uniformly agents. The thermal conductivity of the system containing a small amount of dispersing is comparatively low, but aggregation of particles results in an increase of conductance because of the path for thermal conductance. In the disperse system, aggregation of particles is depressed by the addition of dispersing agents. The thermal conductivity of the system containing a small amount of dispersing agent does not change with time. With increasing concentration of disperse particles, the thermal conductivity of the system is reduced. The concentration dependence of thermal conductivity can be expressed by Hamilton’s theory, qualitatively. However, in the higher concentration region, the experimental values of thermal conductivity are larger than the theoretical values, because highly developed flocculated structures are constructed.
Diffusion and viscoelasticity of polystyrene-dibutyl phthalate solutions (abstract)
Authors: Nemoto Norio , Inoue Tadashi , Osaki Kunihiro , Kishine Masahiro , Kojima Takaharu , Kurata Michio
Published: July 2002

This paper summarizes recent works in which the entanglement effect on diffusion and viscoelasticity was mainly studied on solutions of narrow-distribution polystyrene (PS) in dibutylphthalate (DBP) over a wide range of temperature T, concentration C, and molecular weight M. The temperature dependence of the self-diffusion coefficient Ds and the tracer diffusion coefficient Dtr was described by the WLF equation with values of the WLF coefficients the same as found for the solution viscosity η. The effects of entanglements on the self-diffusion behavior and the viscoelastic behavior were examined from data analysis in terms of the two parameters, the effective friction coefficient of a segment ζ and the molecular weight between entanglements Me. The product Dsη/C was close to the theoretical prediction based on the free Rouse chain up to M/Me∼1 and, for M/Me≳10, showed universal behavior characterized by the linear proportionality to M/Me. The ratio of the two characteristic times for viscoelasticity and diffusion took approximately a constant value of 0.15±0.05 over the whole range of M/Me studied. Reduction of diffusion data on the basis of the two-parameter scheme was so successful that one master curve was obtained for each set of Ds and Dtr∞ data. Both the master curves were proportional to (M/Me)−2.5 in the highly entangled region, being not in harmony with either the prediction of the reptation theory or the observation for PS melts. The tracer diffusion behavior in the unentangled concentrated solution was described by the partial-draining model.
Self diffusion and viscoelasticity of aqueous detergent solutions II. Effect of salt concentration (abstract)
Authors: Yamamura Takeshi , Nemoto Norio , Shikata Toshiyuki , Osaki Kunihiro
Published: July 2002

Diffusion of rod-like micelles of cetyltrimethylammonium bromide (CTAB) in aqueous sodium salicylate (NaSal) solutions were studied by varying CTAB concentration CD and NaSal concentration CS. For solutions with CD=0.01 and 0.1 M, a ratio CS/CD ranged from 1.0 to 41 and from 0.70 to 6.0, respectively. For measurement of the diffusion coefficient D, the forced Rayleigh scattering technique was employed at 25 °C. Plots of D against CS/CD gave very complicated behavior such that D took a maximum and afterward took a minimum with increasing CS/CD. CS/CD values of the maximum and minimum for solutions with CD=0.01 M was very different from that for CD=0.1 M. But the magnitude of D was of the same order of 10−9 cm2 s−1 for both solutions. Diffusion data could be reduced to one master curve by plotting D against the concentration CS* of free salicylate ion Sal− in the low CS* region. The CS* dependence of D at low CS* was found to roughly correspond to that of the relaxation time τ obtained in earlier investigations from a fit of the complex shear modulus data of the same solutions to a Maxwell model with one relaxation time. At high CS*, however, D appeared to increase more rapidly for solutions with CD=0.01 M than those with CD=0.1 M. The diffusion mechanism of rod-like micelles was interpreted in terms of a theory of Brownian motion of a rod in the semidilute region at low CS* and the breaking and reforming process of network strands at high CS*.
A two-fluid model for inconsistency of observations in capillary rheometry of thermotropic copolyesters
Authors: Wissbrun Kurt F.
Published: July 2002

Capillary rheometry of liquid-crystalline polymers is described in terms of the stratified laminar flow of two fluids. The fluid entering the capillary is assumed to have a low viscosity because it has been oriented, except in a thin peripheral shear layer, by the converging entry flow. In the course of its transit through the die the orientation is lost as the fluid is sheared. It is assumed that the oriented fluid is ‘‘transformed’’ to a fluid with power-law viscosity behavior when it has been subjected to some critical value of total shear strain. The interface between the two fluids migrates radially towards the center of the capillary as the flow progresses. With physically reasonable magnitudes for the model parameters the model can account for the experimentally observed concave-upward nonlinearity of Bagley plots and for die diameter dependence of nominal viscosity. Arguments on the effects of deformation on texture and viscosity are proposed to account for other observations of shapes of Bagley plots and of diameter dependence of viscosity.
Thixotropic behavior of clay dispersions: Combinations of scattering and rheometric techniques
Authors: Pignon Frédéric , Magnin Albert , Piau Jean-Michel
Published: July 2002

The thixotropic behavior of a colloidal dispersion of clay consisting of disk-shaped particles was studied by means of a combination of rheometric measurements, static light scattering, and small-angle neutron scattering. At rest, the structure of the gel consists of dense micrometer-sized aggregates assembled into a fractal mass of dimension D. Under shear, in the case of volume fractions with (1⩽D⩽1.2) at rest, a butterfly-type light scattering pattern is observed. This is attributed to the formation of rollers within the dispersion, which align themselves on average perpendicular to the direction of shearing. This produces a fall in resistance to flow and in viscosity. The influence of shear rate on this disaggregation process was studied and linked to the rheometric measurements. Under shear flow conditions, the fall in viscosity is due to orientation and disaggregation processes occurring at length scales on the order of 1 μm. During recovery, the two time scales identified correspond, respectively, to a rapid relaxation of the particle orientations and a slow aggregation process. Thixotropic behavior is identified as being mainly a reversible aggregation process, for which large length scales on the order of a micrometer associated with a fractal arrangement play a decisive role.
Linear response of regular asphalts to external harmonic fields
Authors: Stastna J. , Zanzotto L.
Published: July 2002

Dielectric permittivity and mechanical complex compliance of regular asphalts, at T=323 K, are studied. Both the loss compliance and the loss of permittivity functions can be decomposed into two parts. The first part represents the viscous deformation and the ohmic conductivity, respectively. The second part then describes a “pure” response of the material to external harmonic fields. By this decomposition one can observe a relatively strong transition of regular asphalts into their relaxed state. A simple fractional model of the response function can be applied to both mechanical and dielectric transitions.
The rheology and microstructure of concentrated, aggregated colloids
Authors: Silbert L. E. , Melrose J. R. , Ball R. C.
Published: July 2002

The rheology of concentrated, aggregated colloidal suspensions is determined through particulate simulations. Aggregating systems experience a large viscous enhancement over nonaggregating systems, this being due to the increase in the component of the viscosity arising from the repulsive colloid (thermodynamic) forces when attractive forces are present. The shear behavior of aggregating systems, for colloid volume fraction 0.47⩽φc⩽0.57, is characterized in the steady state regime over a wide range in shear rate, and is found to be power law, shear thinning η∼f(φc)γ̇−α, where the shear thinning index α=0.84±0.01. The effect of volume fraction enters as f(φc)=(1−φc/φmax)−1, with φmax=0.64, the value of random close packing; similarly, the viscosity also scales with the potential well depth as a power law, of index α. Consequently, we are able to deduce the full constitutive relation for this power law behavior. The associated structural features which emerge as a result of the imposed shear are identified with the rheology. The shear thinning regime crosses over into a state of ordered phase flow at high shear rates likewise simulations of hard sphere fluids. We also show that the high-shear ordered configurations appear to be a function of colloid concentration, with a transition from string phase order through to layered phases as φc increases.
Nonhomogenous patterns with core defects in elongational flows of liquid crystal polymers
Authors: Forest M. Gregory , Wang Qi , Zhou Hong
Published: July 2002

The interaction between flow and orientation of liquid crystalline polymers (LCPs) creates remarkable heterogeneous patterns in which defects, or singular solutions, serve to mediate a confluence of ordered nematic phases. The origin of defects remains a mystery. It is therefore valuable to have models for LCP flows that provide some evidence of defects, and of the corresponding physical competition between flow and LCP properties. In this direction, the flow-orientation moment-averaged Doi model is studied with an imposed elongational flow. Nonhomogeneous, biaxial nematic patterns are discovered in both axial and planar elongation. These exact solutions consist of spatially varying directors in the plane orthogonal to the flow axis, coupled with homogeneous biaxial order parameter equilibria fixed by the LCP concentration (N) and elongation rate (ν). For each (N,ν), the following patterns coexist all with identical order parameter values: the homogeneous patterns of [Macromol. Theory Simul. 4, 857872 (1995)]; radially symmetric director patterns; and finally, director patterns periodic in the cylindrical azimuthal angle. The nonhomogeneous structures are distinguished by the presence of core defects along the axis of flow symmetry, characterized by a logarithmic pressure singularity at the core.
Phosphorus‐Fixed Stable Interfacial Nonflammable Gel Polymer Electrolyte for Safe Flexible Lithium‐Ion Batteries
Authors: Mu Xiaowei , Li Xingjun , Liao Can , Yu Hen , Jin Yi , Yu Bin , Han Longfei , Chen LeiKan , Kan Yongchun , Song Lei , Hu Yuan
Published: June 2022

A high content of flame retardant in non‐combustible electrolytes leads to deterioration of the electrochemical performance of lithium‐ion batteries (LIBs). Besides, fire hazard of most non‐flammable electrolytes is studied in coin cell, for which it is impossible to reveal real performance. Thus, the stable interfacial, phosphorus‐fixed nonflammable gel polymer electrolyte (GPE) with low content of flame retardant (7.5 wt.%) has been designed by in situ polymerization of tri(acryloyloxyethyl) phosphate and triethylene glycol dimethacrylate in electrolyte. After being heated by fire for >10 s, the GPE is still not ignited. The average capacity attenuation rate of graphite//GPE//Li (0.008%) is much lower than that of the liquid electrolyte (0.039%). Besides, the nonflammable GPE based pouch cell with good flexibility and excellent fire safety is prepared. No fire, no thermal runaway and no electrolyte leakage occur for 1 Ah flexible pouch cell with 100% SOC. The mechanism for high safety of pouch cell has also been revealed. First the amount of combustible pyrolysis products from thermal degradation of GPE is reduced through forming P and F containing char. Second, the combustion of GPE is extinguished through OH free radical quenching effect of flame retardant molecular. This work provides a guideline for designing high‐safety LIBs.
Boosting Surface‐Dominated Sodium Storage of Carbon Anode Enabled by Coupling Graphene Nanodomains, Nitrogen‐Doping, and Nanoarchitecture Engineering
Authors: Huang Si , Yang Dongjie , Qiu Xueqing , Zhang Wenli , Qin Yanlin , Wang Caiwei , Yi Conghua
Published: June 2022

The development of high‐performance carbon anode for sodium‐ion batteries is limited by the sluggish kinetics and structural instability. Expanded interlayer spacing, nitrogen doping, and mesoporous structure engineering have emerged as promising strategies to overcome these challenges. Simultaneously achieving graphene nanodomains construction, high‐efficient nitrogen doping, and rational mesoporous structure engineering is challenging. Herein, a strategy of pyrolyzing SiO2@ lignin amine urea‐formaldehyde resin is proposed for deliberate manipulation of graphene nanodomains, edge‐nitrogen doping, and specific mesoporous distribution in amorphous lignin‐derived carbon based on polycondensation‐template. The obtained carbon material exhibits a nitrogen‐doping level of 6.03 at% with a high edge‐nitrogen ratio of up to 84.4%, high‐ connectivity mesoporous structure, and graphene nanodomains with expanded interlayer spacing. The optimized carbon material delivers a reversible capacity of 234 mAh g−1 at 100 mA g−1, superior rate capability of 129 mAh g−1 at 2 A g−1, and excellent cycling stability. In addition, the surface‐dominated sodium‐ion storage mechanism is identified by in situ electrochemical impedance spectroscopy. Furthermore, the optimized carbon can function as an outstanding anode for full cells. This work proposes a new avenue for designing high‐performance carbon for low‐cost and high‐rate sodium‐ion batteries.
Directed Particle Transport via Reconfigurable Fiber Networks
Authors: Cu Katharina , Steier Anke , Klaiber Marvin , Franzreb Matthias , Lahann Joerg
Published: June 2022

Mass transport limitations of particulates within conventional microanalytical systems are often cited as the root cause for low sensitivity but can be overcome by directed analyte transport, such as via biomolecular motors or gradient surfaces. An ongoing challenge is the development of materials that are passive in nature (i.e., no external power source required), but can reconfigure to perform work, such as transporting particle‐based analytes. Mimicking biology's concepts of autonomous and reconfigurable materials systems, like the Drosera capensis leaf, reconfigurable fiber networks that effectively concentrate particulates within a localized spot that can act as a detection patch are developed. These networks, prepared by electrohydrodynamic co‐jetting, draw their reconfigurability from a bicompartmental fiber architecture. Upon exposure to neutral pH, a differential swelling of both fiber compartments gives rise to interfacial tension and ultimately results in shape reconfiguration of the fiber network. Compared to free particles, the reconfigurable fiber networks display a 57‐fold increase in analyte detectability, average transport efficiencies of 91.9 ± 2.4%, and separation selectivity between different surface properties of 95 ± 3%. The integration of biomimetic materials into microanalytical systems, exemplified in this study, offers ample opportunities to design novel and effective detection schemes that circumvent mass transport limitations.
Recent Progress in Mixed A‐Site Cation Halide Perovskite Thin‐Films and Nanocrystals for Solar Cells and Light‐Emitting Diodes
Authors: Byranvand Mahdi Malekshahi , Otero‐Martínez Clara , Ye Junzhi , Zuo Weiwei , Manna Liberato , Saliba Michael , Hoye Robert L. Z. , Polavarapu Lakshminarayana
Published: June 2022

Over the past few years, lead‐halide perovskites (LHPs), both in the form of bulk thin films and colloidal nanocrystals (NCs), have revolutionized the field of optoelectronics, emerging at the forefront of next‐generation optoelectronics. The power conversion efficiency (PCE) of halide perovskite solar cells has increased from 3.8% to over 25.7% over a short period of time and is very close to the theoretical limit (33.7%). At the same time, the external quantum efficiency (EQE) of perovskite LEDs has surpassed 23% and 20% for green and red emitters, respectively. Despite great progress in device efficiencies, the photoactive phase instability of perovskites is one of the major concerns for the long‐term stability of the devices and is limiting their transition to commercialization. In this regard, researchers have found that the phase stability of LHPs and the reproducibility of the device performance can be improved by A‐site cation alloying with two or more species, these are named mixed cation (double, triple, or quadruple) perovskites. This review provides a state‐of‐the‐art overview of different types of mixed A‐site cation bulk perovskite thin films and colloidal NCs reported in the literature, along with a discussion of their synthesis, properties, and progress in solar cells and LEDs.
Unprecedented Superhigh‐Rate and Ultrastable Anode for High‐Power Battery via Cationic Disordering
Authors: Wu Wei , Liu Mingxian , Pei Yi , Li Wenjin , Lin Wang , Huang Qiyao , Wang Man , Yang Haitao , Deng Libo , Yao Lei , Zheng Zijian
Published: June 2022

High‐power lithium‐ion batteries (LIBs) are critical for power‐intensive applications; however, their development is largely hindered by the lack of anode materials that have stability and high capacity at high charging/discharging rates. Herein, a cationic disordering strategy is reported to build an ideal high‐power anode with boosted intercalation kinetics and a stable framework. A novel titanium niobate (TiNb2O7) anode with unique predistorted Nb(Ti)O6 octahedrons (pd‐TNO) is developed by introducing cation disorder, which allows ultrafast Li+ storage within seconds and exceptional stability over long cycling at high rates. The pd‐TNO delivers an outstanding specific capacity of 153 mAh g−1 at 100 C, 20 times higher than that of conventional TNO anodes without cationic disordering, and retains 42.8% of the capacity after 15,000 cycles. Using the pd‐TNO anode, a high‐power LIB with an unprecedented power density of 91,197 W kg−1 at 200 C, which is approximately eight times higher than that of the advanced commercial high‐power anode Li4Ti5O12 (11,813 W kg−1 at 50 C), is demonstrated. Importantly, the pd‐TNO is prepared under ambient conditions via a high‐throughput process, and it exhibits considerable potential for scalability for practical applications.
Impact of autologous hematopoietic cell transplantation on disease burden quantified by next‐generation sequencing in multiple myeloma treated with quadruplet therapy
Authors: Bal Susan , Dhakal Binod , Silbermann Rebecca W. , Schmidt Timothy M. , Dholaria Bhagirathbhai , Giri Smith , Chhabra Saurabh , Medvedova Eva , Godby Kelly N. , D'Souza Anita , Hall Aric C. , Hardwick Pamela , Omel Jim , Cornell Robert F. , Hari Parameswaran , Callander Natalie S. , Costa Luciano J.
Published: June 2022

The incremental impact of autologous hematopoietic cell transplantation (AHCT) on disease burden with quadruplet induction in newly diagnosed multiple myeloma (NDDM) can be reappraised with the serial assessment of minimal residual disease (MRD). We describe the impact of AHCT on MM burden assessed by next‐generation sequencing (NGS) for patients enrolled in a clinical trial utilizing quadruplet induction, AHCT, followed by MRD‐adapted consolidation. We describe quantitative changes in MRD burden with AHCT and explore patient and disease features influencing the magnitude of MRD reduction with AHCT. Among 123 included patients, 109 underwent AHCT and had MRD assessment pre and post AHCT. Forty percent achieved MRD < 10−5 post‐induction, increasing to 70% after AHCT. Of the 65 patients (60%) who remained MRD positive post‐induction, 54 (83%) had a reduction in MRD burden with AHCT. The median reduction in MRD with AHCT was 1.10 log10 (range, −1.26 to 3.41). Patients with high‐risk cytogenetic abnormalities (HRCA) had greater reduction in MRD burden (p = .02) after AHCT. Median relative reduction was 0.91 log10 (range, −0.75 to 2.14), 1.26 log10 (range, −0.21 to 3.26) and 1.34 log10 (range, −1.28 to 3.41) for patients with 0, 1 and 2+ HRCA, respectively. The presence of HRCA was the only factor associated with greater than 1 log10 reduction in MRD burden with AHCT. Serial NGS MRD demonstrates the incremental effect of AHCT in MM marrow burden in the context of quadruplet induction, particularly in high‐risk MM.
Autophagy and autophagy‐related molecules in neurodegenerative diseases
Authors: Dou Changsong , Zhang Yu , Zhang Ling , Qin Chuan
Published: June 2022

Autophagy is one of the degradation pathways to remove proteins or damaged organelles in cells that plays an important role in neuroprotection. Different stages of autophagy are regulated by autophagy‐related genes, and many molecules such as transcription factor EB (TFEB) are involved. The complete autophagy process plays an important role in maintaining the dynamic balance of autophagy and is crucial to the homeostasis of intracellular substance and energy metabolism. Autophagy balance is disrupted in neurodegenerative diseases, accounting for a variety of degeneration disorders. These impairments can be alleviated or treated by the regulation of autophagy through molecules such as TFEB.
All‐Optical Generation of Multifunctional and Tunable Longitudinal Magnetization Textures
Authors: Zhou Zhilong , Liu Xiaofei , Nie Zhongquan , Lin Han , Guo Chunsheng , Jia Baohua
Published: June 2022

An all‐optical strategy for creating multifunctional and tunable longitudinal magnetization textures is demonstrated. This is realized by flexibly engineering the coherent interferences of two counter‐propagating azimuthally polarized vortex beams possessing on‐demand phase and amplitude encoding in a 4π optical microscopic setup. In doing so, one can access not only the regular longitudinal magnetization patterns including bright spheroid/needle, dark cage/channel, and bright‐dark alternating chain/comb, but also the exotic twisted counterparts with controllable number of turns, thereby making versatile magnetization on the targeted magneto‐optical media with integrated footprint possible. The presented research findings may hold tremendous potential in multidimensional high density and low energy consumption optomagnetic storage and photonics of spin, and beyond.
Synthesis of a CCC‐NHC pincer Re complex: An air stable catalyst for coupling ketones with primary alcohols via borrowing hydrogen
Authors: Pham Hoang H. , Donnadieu Bruno , Hollis T. Keith
Published: June 2022

To date, no CCC‐NHC pincer complexes of Re have been reported in the literature. The first CCC‐NHC pincer complex of Re is reported. It was fully characterized by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, mass spectroscopy, elemental analysis, and X‐ray crystallographic methods to determine the molecular structure. It was synthesized via transmetallation from an isolated Zr precursor and was found to be air stable. The catalytic activity of the CCC‐NHC Re(I) pincer complex was demonstrated for the borrowing hydrogen coupling reaction between benzylic ketones and primary alcohols to generate a new C–C bond in an environmentally friendly catalysis requiring no activating groups for the alcohol functionality. This borrowing hydrogen coupling reaction produced a stoichiometric amount of water as the only by‐product and did not require the conversion of the primary alcohol to a leaving group. A broad range of substrates was examined, and isolated yields from 53% to 92% were obtained. A catalytic cycle for the CCC‐NHC Re(I) pincer complex catalyzed borrowing hydrogen coupling reaction is proposed.
Construction of pH‐responsive core crosslinked micelles via thiol‐yne click reaction
Authors: Niu Yile , Lu Yanbing
Published: June 2022

Polycarbonate‐based micelles possessed enormous potential for hydrophobic drug delivery. To improve micelle stability and prevent premature leakage during blood circulation, photo‐induced thiol‐yne click reaction was utilized to construct polycarbonate‐based core crosslinked micelles (CCLMs), which avoided the use of toxic copper catalyst. The introduced β‐thiopropionate linkage in the core was demonstrated to endow the CCLMs with pH‐responsiveness. The obtained CCLMs showed good dilution stability against DMF and water. Further MTT assays demonstrated excellent biocompatibility and low toxicity of the CCLMs in HeLa/MCF‐7 cells. Moreover, DOX‐encapsulated CCLMs showed good anticancer effects and excellent internalization efficiency in HeLa cells. The pH‐responsive polycarbonate‐based CCLMs by thiol‐yne click reaction have potential used as smart delivery systems for controlled drug release.
Covalent organic framework‐poly(acrylic acid)‐modified poly(vinylidene fluoride) ultrafiltration membranes towards enhanced antifouling properties and low hydrophilic material leaching
Authors: Xu Wentao , Zhuang Huaqiang , Chen Wenjie , Liu Wei , Pan Xiaoyang
Published: June 2022

The hydrophilicity is acknowledged critically to raise anti‐fouling of membranes conferring a leaching problem over a prolonged operation. To decrease the leaching of hydrophilic material in modified membranes, poly(vinylidene fluoride) (PVDF) ultrafiltration membranes is herein presented using covalent organic framework (COF)‐poly(acrylic acid) (PAA) modifier via PAA‐catalyzed in‐situ COF synthesis method. The modified PVDF membrane with an optimized COF‐PAA content showed higher water flux (95 L/m2 h), greater bovine serum albumin rejection, and superior antifouling properties to sodium alginate (95% FRR values). The stability test conducted on COF‐PAA‐modified PVDF membrane gave a lower leaching rate of PAA than that of the PAA‐modified counterpart. The membrane containing COF‐PAA compared with the COF‐free counterpart showed a smaller water contact angle down to 55°. The morphologies of the COF‐modified membranes and the COF‐free counterpart studied with scanning electron microscope found that the COF in tight bonding to PAA was homogeneously bonded to the membrane surface. The surface modification contributes to greater stability and anti‐fouling properties of the membrane. The enhanced properties can associate with the reduced pore size of PVDF membrane via in‐situ COF synthesis using the catalyst PAA. This work provides a novel strategy towards the further development of efficient composite membranes with enhanced antifouling properties and water flux.