bluuebunny/crossref_metadata_2025 huggingface dataset:
An inducible helix–Gly–Gly–helix motif in the N‐terminal domain of histone H1e: A CD and NMR study
Authors: Vila Roger , Ponte Imma , Jiménez M. Angeles , Rico Manuel , Suau Pedro
Published: July 2002

Knowledge of the structural properties of linker histones is important to the understanding of their role in higher‐order chromatin structure and gene regulation. Here we study the conformational properties of the peptide Ac‐EKTPVKKKARKAAGGAKRKTSG‐NH2 (NE‐1) by circular dichroism and 1H‐NMR. This peptide corresponds to the positively charged region of the N‐terminal domain, adjacent to the globular domain, of mouse histone H1e (residues 15–36). This is the most abundant H1 subtype in many kinds of mammalian somatic cells. NE‐1 is mainly unstructured in aqueous solution, but in the presence of the secondary‐structure stabilizer trifluoroethanol (TFE) it acquires an α‐helical structure. In 90% TFE solution the α‐helical population is ∼40%. In these conditions, NE‐1 is structured in two α‐helices that comprise almost all the peptide, namely, from Thr17 to Ala27 and from Gly29 to Thr34. Both helical regions are highly amphipathic, with the basic residues on one face of the helix and the apolar ones on the other. The two helical elements are separated by a Gly–Gly motif. Gly–Gly motifs at equivalent positions are found in many vertebrate H1 subtypes. Structure calculations show that the Gly–Gly motif behaves as a flexible linker between the helical regions. The wide range of relative orientations of the helical axes allowed by the Gly–Gly motif may facilitate the tracking of the phosphate backbone by the helical elements or the simultaneous binding of two nonconsecutive DNA segments in chromatin.
In vivo assessment of trabecular bone structure at the distal radius from high‐resolution magnetic resonance images
Authors: Gordon Christopher L. , Webber Colin E. , Christoforou Nicholas , Nahmias Claude
Published: July 2002

In this study a method of assessing trabecular bone structure at the distal end of the radius from high‐resolution magnetic resonance images is described. Trabecular bone is segmented from the marrow and soft tissue background using an adaptive threshold, a region growth, and a skeletonization step. From the processed image we measured the connectivity and orientation of the trabecular bone network. Connectivity was assessed by a proposed connectivity index (CI) and marrow space was quantitated by a mean hole area Significant age‐related changes in CI and were observed in a mixed group of normal volunteers. CI decreased at a rate of and increased at a rate of Gradient analysis was used to examine trabecular orientation, and revealed that the individual trabeculae at the distal end of the radius are organized anisotropically along the bone. These findings suggest that clinical magnetic resonance scanners can be used to assess trabecular bone structure in vivo.
Designing accelerator‐based epithermal neutron beams for boron neutron capture therapy
Authors: Bleuel D. L. , Donahue R. J. , Ludewigt B. A. , Vujic J.
Published: July 2002

Thereaction has been investigated as an accelerator‐driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials,andhave been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte CarloN‐particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth‐dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator‐based neutron source withoras moderator material can produce depth‐dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to ∼50% higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and amoderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy‐Eq.
Identification of lung regions in chest radiographs using Markov random field modeling
Authors: Vittitoe Neal F. , Vargas‐Voracek Rene , Floyd Carey E.
Published: July 2002

The authors present an algorithm utilizing Markov random field modeling for identifying lung regions in a digitized chest radiograph (DCR). Letxrepresent the classifications of each pixel in a DCR as either lung or nonlung. We modelxas a realization of a spatially varying Markov random field. This model is developed utilizing spatial and textural information extracted from samples of lung and nonlung region‐types in a training set of DCRs. With this model, the technique of Iterated Conditional Modes is used to determine the optimal classification of each pixel in a DCR. The algorithm's ability to identify lung regions is evaluated on a testing set of DCRs. The algorithm performs well yielding a sensitivity ofa specificity ofand an accuracy ofIn an attempt to gain insight into the meaning and level of the algorithm's performance numbers, the results are compared to those of some easily implemented classification algorithms.
Image feature extraction for mass detection in digital mammography: Influence of wavelet analysis
Authors: Qian Wei , Li Lihua , Clarke Laurence P.
Published: July 2002

Rationale and objectives. The objective of this work is to evaluate the importance of image preprocessing, using multiresolution and multiorientation wavelet transforms (WTs), on the performance of a previously reported computer assisted diagnostic (CAD) method for breast cancer screening, using digital mammography. Method: An analysis of the influence of WTs on image feature extraction for mass detection is achieved by comparing the discriminant ability of features extracted with and without the wavelet‐based image preprocessing using computed ROC. Three indexes are proposed to assess the segmentation of the mass area with comparison to the ground truth. Data was analyzed on the region‐of‐interest (ROI) database that included mass and normal regions from digitized mammograms with the ground truth. Results: The metrics for the measurement of segmentation of the mass clearly demonstrated the importance of image preprocessing methods. Similarly, the relative improvement in performance was observed in feature extraction based on the evaluation of the ROC curves, where the Az values are increased, for example, from 0.71 to 0.75 for a pixel intensity feature and from 0.72 to 0.85 for a morphological feature of the Normalized Deviation of Radial Length. The improvement, therefore, depends on the feature characteristics, being large for boundary‐related features while small for intensity‐related features. Conclusion: The use of image preprocessing modules using wavelet transforms results in a significant improvement in feature extraction for the previously proposed CAD detection method. We are therefore exploring additional improvement in wavelet‐based image preprocessing methods, including adaptive methods, to achieve a further improvement in performance and an evaluation on larger image databases.
Necessary conditions for a maximum likelihood estimate to become asymptotically unbiased and attain the Cramer–Rao Lower Bound. Part I. General approach with an application to time-delay and Doppler shift estimation
Authors: Naftali Eran , Makris Nicholas C.
Published: July 2002

Analytic expressions for the first order bias and second order covariance of a general maximum likelihood estimate (MLE) are presented. These expressions are used to determine general analytic conditions on sample size, or signal-to-noise ratio (SNR), that are necessary for a MLE to become asymptotically unbiased and attain minimum variance as expressed by the Cramer–Rao lower bound (CRLB). The expressions are then evaluated for multivariate Gaussian data. The results can be used to determine asymptotic biases, variances, and conditions for estimator optimality in a wide range of inverse problems encountered in ocean acoustics and many other disciplines. The results are then applied to rigorously determine conditions on SNR necessary for the MLE to become unbiased and attain minimum variance in the classical active sonar and radar time-delay and Doppler-shift estimation problems. The time-delay MLE is the time lag at the peak value of a matched filter output. It is shown that the matched filter estimate attains the CRLB for the signal’s position when the SNR is much larger than the kurtosis of the expected signal’s energy spectrum. The Doppler-shift MLE exhibits dual behavior for narrow band analytic signals. In a companion paper, the general theory presented here is applied to the problem of estimating the range and depth of an acoustic source submerged in an ocean waveguide.
Conversion of a Stoneley wave at the extremity of a fluid loaded plate
Authors: Briers R. , Leroy O. , Shkerdin G. N.
Published: July 2002

A theoretical model, based on mode theory, is presented in order to study the behavior of the Stoneley wave when it reaches the extremity of a thick plate immersed in a liquid. The superposition of two phenomena is established: the first one being the simple forward diffraction of the Stoneley wave in the liquid and the second one being its conversion into two generalized Rayleigh waves which propagate on the same plane as the incident Stoneley wave or along the vertical end face of the solid support. The theoretical analysis is in good agreement with the experimental observations of Tinel [Ph.D. Thesis, Université Le Havre, France (1991)].
Auditory filters measured at neighboring center frequencies
Authors: Fagelson Marc A. , Champlin Craig A.
Published: July 2002

Auditory filters were derived in 20 normal-hearing human listeners at center frequencies (CFs) of 913, 1095, 3651, and 4382 Hz using the roex (p,r) method. Comparisons were made between slopes of the filters’ skirts at the neighboring CFs with filter output levels of 45 and 70 dB. The same comparisons were made with regard to filter equivalent rectangular bandwidth (ERB). In the 1000-Hz region, the low-frequency slopes (Pl) of filters centered at 913 and 1095 Hz were significantly correlated at both stimulus levels, while the high-frequency slopes (Pu) were similar only at the high test level. In the 4000-Hz region, for sinusoids of 3651 and 4382 Hz, the level effect was clearer as both Pu and Pl values diverged at the low level but were related at high levels. The ERBs centered at the same CFs displayed a similar level dependence. At the stimulus level most likely to be affected by an active feedback mechanism, auditory filters centered at nearly the same frequency displayed quite distinct frequency selectivity, and this trend was stronger in the 4000-Hz region than the 1000-Hz region. The findings suggest that a saturating, active cochlear mechanism may not be distributed evenly, or contribute to peripheral tuning with equal effectiveness throughout the length of the partition.
Goupillaud inverse problem with arbitrary input
Authors: Ning Wang , JunXuan Lin , Sadayuki Ueha
Published: July 2002

A new impulse inverse formula and it’s generalization including arbitrary input, are proposed. The new generalized inverse formula has the advantage of not being necessary to specify the first digital value of the input. Numerical instability of the inverse formula for arbitrary input is investigated carefully. An analysis of the perturbed stability and Lyapunov exponent are carried out. As the result of this analysis, it is shown that the estimated error is sensitive to the experimental error and previously estimated error as a sequential algorithm. Simulation using experimental data is also shown in the paper.
Comparisons of exact and approximate convection of plane waves in a simple shear flow
Authors: Leep-Apolloni Laurine , Dowling David R.
Published: July 2002

In aero- and environmental-acoustic problems, propagation of sound waves through a medium with a nonuniform mean flow has commonly been treated by several different approximate techniques typically involving integral transforms, geometrical acoustics, or other approximate methods. An effectively exact solution technique that properly incorporates the vector character of mean-flow convection has been found [L. Nijs and C. P. A. Wapenaar, J. Acoust. Soc. Am. 87, 1987–1998 (1990)]. However, the formal and numerical complexity of these techniques, typically coupled with nontrivial impedance boundary conditions, has prevented detailed comparisons of acoustic field variables with and without exact treatment of convection. This paper presents results and comparisons between exact and approximate treatments of acoustic plane waves propagating in a simple shear flow. The solution of the linearized time- and space-dependent equations of inviscid fluid motion, as nondimensionalized herein, depends on two-dimensionless parameters, m/f and ft, where m is the convecting flow’s shear rate, f is the acoustic frequency, and t is the length of time that the plane waves interact with the shear flow. The exact treatment involves numerical solution of the governing equations. The approximate treatment is handled with a WKB solution valid for m/f≪1. A comparison of results shows that the approximate treatment of convection produces only single digit percentage errors when (m/f )(ft)=mt≲0.5. However, pressure amplitude differences increase rapidly beyond mt≈0.5 and are found to grow approximately as exp{+0.4(mt)2}. In addition, the computed results display phenomena that are completely absent from the WKB solution such as: (i) dynamic misalignment of the acoustic-velocity vector and the wave front normal; and (ii) the existence of significant acoustic perturbation vorticity.
Inherent background coefficients for acoustic resonance scattering from submerged, multilayered, cylindrical structures
Authors: Joo Young-Sang , Ih Jeong-Guon , Choi Myoung-Seon
Published: July 2002

For the scattering of acoustic waves by an elastic shell, the acoustical background coefficients are inherent in the scattering coefficients. The background coefficients for elastic empty shells, named the inherent background, can be obtained from the zero frequency limit of the modal accelerance in the scattering coefficients for analogous liquid shells. In this work, the concept of obtaining the inherent background is applied to multilayered elastic cylindrical structures. The inherent background manifests itself in the sound scattering by the liquid structures. The scattering S-function and the modal accelerance for the liquid system are determined by considering the incoming and outgoing waves. The accelerance of liquid layers is generalized so that the scattering function can be obtained by the recurrence relation for the accelerances of the adjacent liquid layers. From the zero frequency limit of the generalized accelerance of liquid structures, the constant modal accelerance is extracted and the general expression for the inherent background coefficients is obtained. The background coefficients depend on the densities of the layers and ambient fluid medium, the relative thickness of each layer, and the normal mode number. The acoustical background coefficients for solid cylinders, empty shells, fluid-filled shells, and double-layered shells can be obtained by the appropriate limit of the density ratio and the relative thickness of layers in the generalized inherent background coefficients. The usefulness of the proposed background is demonstrated for several examples of layered structures.
A broadband acoustic fish identification system
Authors: Denny Gerald , Simpson Patrick
Published: July 2002

A broadband fish identification system has been built and tested in the Great Lakes, Prince William Sound, and the Bering Sea. Unique signatures have been obtained on free swimming and captive animals. These signatures include jellyfish, euphausiids, Pacific Rockfish, and Walleye Pollock. Acoustic characteristics and utilization of the system will be discussed, as well as results of in situ data collection.
Complex acoustic waveforms excited with multiple picosecond transient gratings formed using specially designed phase-only beam-shaping optics
Authors: Rogers John A.
Published: July 2002

This paper describes a method for using a pulsed laser and specialized low cost beam-shaping optics to launch complex acoustic waveforms with user-definable geometries; diffraction of a continuous wave probe laser from these waveforms reveals their temporal evolution in real time. Methods are introduced for designing and fabricating simple binary phase optics for beam-shaping that is useful for high-frequency measurements on thin films. Experiments on films of platinum on silicon demonstrate the approach.
Scattering by an elastic sphere embedded in an elastic isotropic medium
Authors: Sessarego Jean-Pierre , Sageloli Jean , Guillermin Régine , Überall H.
Published: July 2002

The scattering of acoustic waves by an elastic sphere embedded in an elastic isotropic medium is investigated. Expressions for the scattered waves are given in terms of monostatic and bistatic scattering cross sections. The resonances of the solid sphere were determined numerically in the individual normal mode amplitudes; dispersion curves for the phase velocities of the circumferential waves were also obtained. Computations and experimental results for an aluminum sphere embedded in Plexiglas were in good agreement.
On the use of stair steps to approximate bathymetry changes in ocean acoustic models
Authors: Jensen Finn B.
Published: July 2002

Stair-step discretization criteria have been established for accurately representing smoothly varying bathymetry in numerical models. It is shown that the strictest criterion applies to backscatter calculations, where the horizontal stair-step size must be a small fraction of an acoustic wavelength (Δx⩽λ/4). The forward scatter problem—assuming that backscatter is weak—can be accurately solved with an order-of-magnitude larger step sizes. A coupled-mode approach is used to illustrate solution convergence by computing backscattering from a single bottom facet as well as backscattering in the benchmark wedge used for checking ocean acoustic models in the 1987 benchmark session of the Acoustical Society of America (ASA). Published field solutions for the ASA wedge are used to illustrate forward scatter results.
Robust control of a sensorless bass-enhanced moving-coil loudspeaker system
Authors: Bai Mingsian R. , Wu Hsinping
Published: July 2002

Moving-coil loudspeakers generally exhibit poor response in the low-frequency range because the diaphragms are unable to produce sufficient volume velocity. To alleviate the problem, this study focuses on enhancing the low-frequency performance of loudspeakers by means of modern control techniques. A self-sensing velocity observer is utilized for producing the cone velocity signal required by the controller. Feedback H∞ robust control and feedforward H2 model matching control are employed to simultaneously achieve robust stabilization and tracking performance. The proposed controller is implemented using a combined digital signal processor and operational amplifier circuitry.
Measurements of nanometer scale interface diffusion between tungsten and niobium thin films using high frequency laser based ultrasound
Authors: Richardson C. J. K. , Ehrlich M. J. , Wagner J. W.
Published: July 2002

This article presents the use of a quantitative analysis technique to describe time-resolved acoustic spectroscopy (high frequency laser based ultrasound) measurements of atomic diffusion on nanometer length scales occurring at the interface between sputter-deposited tungsten and niobium films. The extent of diffusion at the tungsten-niobium interface is determined by comparing experimental, simulated, and theoretical transfer functions between acoustic arrivals. The experimental and simulated transfer functions use the spectral content of successive reflected acoustic waves and the theoretical transfer function is based on the transfer matrix of an equivalent stratified interface region. This combination of theoretical, simulated, and experimental analyses makes it possible to separate signals with distinct differences between the as-deposited interface and those interfaces diffused to an experimentally determined 0.8-nm and 1.4-nm extent. Comparison of predicted and measured diffusion depths for this diffusion couple indicates that bulk diffusivities are not appropriate for describing nanometer scale interface diffusion.
Thickness shearing vibration of the tangentially polarized piezoelectric ceramic thin circular ring
Authors: Shuyu Lin
Published: July 2002

The thickness shearing vibration of the tangentially polarized piezoelectric ceramic thin circular ring is studied. The electrical and mechanical characteristics of the ring are analyzed in detail. The electro-mechanical equivalent circuit, the input electrical impedance, and the frequency equations for the resonance and anti-resonance frequencies are derived. A new concept that is characterized by the cross sectional shape and dimension is presented. An important conclusion is obtained that the thickness shearing vibration of the tangentially polarized piezoelectric ceramic ring is different from the traditional thickness extensional and radial extensional vibrations in that the electro-mechanical conversion coefficient, the electro-mechanical coupling coefficient, and the resonance frequency equation depend not only on the material parameters and the longitudinal dimension, but also on the lateral dimension, such as the cross sectional radius. It is shown that the measured resonance frequencies are in agreement with the theoretically calculated results, and the theoretical relationship between the resonance frequency and the cross sectional radius is also verified.
A Method for Measuring Normal Stresses in Dilute Polymer Solutions
Authors: James David F.
Published: July 2002

A new technique to measure normal stresses in dilute polymer solutions is described. The apparatus developed for this method essentially consists of two closely spaced disks in relative rotation. Fluid is slowly introduced at the center of the disks so that there is a small radial flow superposed on the circumferential motion, and the normal stresses induced in the circumferential direction are detected by measuring the retardation of the radial flow. From such measurements, a fluid relaxation time can be found for each sample and data with dilute Polyox solutions indicate some agreement with predictions from the molecular theory of Rouse.
Stress Wave Propagation in an RTV Rubber
Authors: Sutherland Herbert J.
Published: July 2002

The response of a “rubbery” polymer, Dow Corning Silastic J Mold Making Silicone Rubber, to high-amplitude, short-duration loading is studied using acoustic waves and high-amplitude stress waves. The acoustic experiments measured the phase velocity of a 1 MHz wave over a temperature range of −30°C to +65°C. These measurements were used to deduce the zero-strain slope of the instantaneous and equilibrium stress-strain curves for this material. Flyer-plate impact experiments were used to study the high-amplitude response. Two instrumentation techniques were used in this phase of the study. The first employed a quartz gauge in the “direct-impact” configuration to obtain information about the equilibrium stress-strain curve. The second employed velocity interferometer techniques to observed transmitted wave profiles and thereby obtain information about both the instantaneous and equilibrium curves. From these data, stress-strain curves were determined for the Silastic J up to 0.8 GPa. Using this material characterization, the transmitted wave experiments were simulated using a one-dimensional wave propagation code. The results of the calculations compare favorably with the transmitted wave profiles observed in the actual experiments.
Surface Elasticity and Viscosity of Red Cell Membrane
Authors: Hochmuth R. M. , Hampel W. L.
Published: July 2002

Force-deformation curves are measured for individual human red blood cells by applying an equal and opposite force at diametrically opposite “points” on the red cell rim. Upon release of a cell, it rapidly recovers its unstressed disklike shape in approximately 0.3 sec. This deformation and subsequent recovery process is analyzed with a constitutive equation which describes the finite deformation at constant area of a two-dimensional viscoelastic solid. From the analysis and the experimental results, values obtained for the “shear modulus of surface elasticity” and “coefficient of surface viscosity” are on the order of 4×10−3 dyn/cm and 5×10−4 dyn sec/cm (P cm), respectively.
The density dependence of fluid properties and non-Newtonian flows: The Weissenberg effecta)
Authors: Rainwater J. C. , Hanley H. J. M. , Narayan A.
Published: July 2002

Two approaches which describe the Weissenberg effect (height profile of a non-Newtonian fluid between rotating vertical concentric cylinders) are discussed. The first is based on an earlier calculation with rheological properties of a simple liquid obtained from nonequilibrium molecular dynamics (NEMD). The calculation is redone here using new results on the density dependence of the normal pressure differences. The NEMD calculations are restricted to Couette flow, but describe specifically, in a consistent manner, the effects of finite compressibility. The pressure, viscosity, and normal pressure differences are all found from NEMD to be sensitive functions of density, which requires that the equations of motion be solved iteratively and self-consistently, and a sample calculation is presented for the soft sphere fluid. The second approach is that of Joseph and Fosdick. Their assumptions and techniques are examined and compared with the NEMD calcula- tions.
Thermodynamic approach to rheological modeling and simulations at the configuration space level of description
Authors: Jongschaap R. J. J. , Denneman A. I. M. , Conrads W.
Published: July 2002

The so-called matrix model is a general thermodynamic framework for microrheological modeling. This model has already been proven to be applicable for a wide class of systems, in particular to models formulated at the configuration tensor level of description. For models formulated at the configuration space level of description a matrix formulation is readily obtained, but for the subsequent analysis one still needs an explicit solution of the configuration space distribution functions. In the present paper we describe an approach in which this problem is solved by combining the matrix model with a Lagrangian simulation method in configuration space developed recently by Szeri and Leal. The result is a consistent and unified formulation of stress tensor expressions, including the stress averaging, and the evolution equations. This formulation is also suited for numerical simulations. In this way, the range of applicability of the matrix model is extended substantially. In order to clarify the principles of the method and some aspects of its implementation, a simple example is discussed in some detail.
Nonlinear shear and extensional rheology of long-chain randomly branched polybutadiene
Authors: Kasehagen Leo J. , Macosko Christopher W.
Published: July 2002

We present nonlinear shear and uniaxial extensional measurements on a series of polybutadienes with varying amounts of long-chain, random branching. Startup of steady shear experiments is used to evaluate the damping function of the melts. The damping function is found to show a trend toward decreased dependency on strain with increasing branching content. Interior chains, which are believed to be responsible for changing the damping function, are calculated to comprise less than 3 wt % of the melt. Extensional measurements are used to investigate the role of branching in strain hardening. We show that samples with increased branch contents do show larger deviations of the transient Trouton ratio from the linear viscoelastic limit of three. However, we also show that the extensional data can be fit using parameters determined solely by the shear measurements. Furthermore, we show that the changes in the damping function seen in shear have little impact on extensional behavior. The extensional behavior of the melt is found to be most affected by changes in the relaxation spectra which can result from both branching and increases in the high end of the molecular weight distribution. This statement runs contrary to the often expressed view that strain hardening behavior in extension is exclusively produced by branching.
Brownian dynamics simulations of a DNA molecule in an extensional flow field
Authors: Larson R. G. , Hu Hua , Smith D. E. , Chu S.
Published: July 2002

The unraveling dynamics of long, isolated, molecules of DNA subjected to an extensional flow in a crossed-slot device [, “Single polymer dynamics in an elongational flow,” Science 276, 2016–2021 (1997); “Response of Flexible Polymers to a Sudden Elongational Flow,” Science 281, 1335–1340 (1998)] are predicted by Brownian dynamics simulations using measured elastic and viscous properties of the DNA as the only inputs. Quantitative agreement is obtained both in the percentages of various unraveling states, such as “folds,” “kinks,” “dumbbells,” half-dumbbells,” and “coils,” and in the ensemble-averaged stretch and rate of stretch. Under fast flows (De≳10), unraveling is initially nearly affine, but for fractional stretch greater than ≈1/3, stretching is delayed to an extent that varies widely from molecule to molecule by flow-induced folded states, which are far-from-equilibrium kinetic hindrances not predicted by dumbbell models. From the computer simulations, the source of the high molecule-to-molecule heterogeneity in the experiments is traced to variability in the initial polymer configuration, which sets the unraveling path the molecule must take at De≳10. Formation of folds and kinks during unraveling can be predicted fairly reliably just by examining the initial state. The high-De unraveling behavior is consistent with the predictions of one-dimensional “kink dynamics” simulations.
Influence of the chemical nature of various geometries on the rheological behavior of a lamellar lyotropic phase
Authors: Jager-Lézer N. , Feutelais Y. , Doucet J. , Tranchant J. F. , Alard V. , Baszkin A. , Grossiord J. L.
Published: July 2002

The influence of the chemical nature of the substrate was studied in order to determine its impact on the rheological behavior of lyotropic lamellar phases. Small-angle x-ray diffraction analysis established that the plastic behavior of the samples could be explained by the large disorganization of the lamellar layers in the vicinity of surfaces as stainless steel, gold, tin, copper, and bismuth. On the other hand, layer alignment was almost perfect on quartz, and the lamellar samples displayed a dominant viscous behavior induced by the flow of the lamellar layers in the vicinity of the surfaces. On zinc sulfide, an in between behavior was observed and the lamellar sample showed two yield stress: one is necessary to induce local alignment of layers in the vicinity of the surfaces, and the other must align the layers of the lamellar sandwich in the flow direction. Assumptions as to the origin of the complex and varied organization have been studied by considering the surface free energy and the surface topology. However, no obvious relationship could be established between surface free energy and liquid crystal alignment. Similarly, no influence of the topology on lamellar orientation could be brought to the fore.
Wide QRS Complex Transient Pattern in a Patient With Severe COVID-19
Authors: Pham Richard , Tsushima Takahiro , Sahadevan Jayakumar
Published: March 2023

This case report describes a patient in their 60s with shortness of breath who tested positive for COVID-19.
Initiatives to improve living conditions in the U.K. around World War I
Authors: Ohtsubo Akira
Published: March 2023

The movement to provide government subsidies to public housing arose in the U.K., in the early 20th century. Housing environment and dwelling unit environment were improved through this movement. This study examines improvements in the provisions of housing Acts and housing estates around World War I (WWI). Major findings of this study are as follows: Government subsidies or loans, dwelling unit density, and relaxation of byelaws were established in the provisions of the housing Acts. Further,—improvements to living conditions were realized in housing estates during WWI, and many other improvements suggested in the recommendation of Tudor Walters report were realized after WWI.
A Smart MMP13‐Responsive Injectable Hydrogel with Inflammatory Diagnostic Logic and Multiphase Therapeutic Ability to Orchestrate Cartilage Regeneration
Authors: Tianyuan Zhao , Haoyuan Deng , Jianwei Li , Songlin He , Xu Li , Hao Li , Zhen Yang , Haotian Deng , Peiqi Li , Xiang Sui , Shuangpeng Jiang , Quanyi Guo , Shuyun Liu
Published: March 2023

Despite numerous attempts to engineer cartilage tissue in recent years, significant challenges remain regarding hyaline cartilage regeneration. One main reason is that the overactivated inflammatory response after injury suppresses inherent cartilage regenerative capabilities. Since the arthritic microenvironment is constantly changing during posttraumatic stress, an inflammatory diagnostic logic‐based hydrogel for cartilage regeneration is developed for the first time through cross‐linking of 4‐arm poly(ethylene glycol)‐vinyl sulfone (PEG‐VS) and specific matrix metalloproteinase (MMP) 13‐sensitive peptides. The hydrogel exhibits diagnostic logic to identify the pathological cue MMP13 and accordingly determine drug release kinetics in an inflammatory microenvironment. Additionally, multiphase therapeutic ability is designed to program different cargo release behaviors to match the inflammation‐chondrogenesis cascade for better cartilage regeneration. Here, it is first proposed that MMP13 is a suitable diagnostic biomarker to modulate the inflammatory microenvironment in the early stage of cartilage injury. In vitro and in vivo studies show that the hydrogel has good injectability, on‐demand anti‐inflammation, and immunomodulation capabilities. Ultimately, loaded with multiple therapeutic factors, the hydrogel shows both microenvironmental modulation and chondrogenesis therapeutic ability, resulting in satisfactory hyaline cartilage regeneration. This study provides critical insight into the design and biological mechanism of both diagnostic and therapeutic ability‐based cartilage tissue engineering strategies.
New Polymerized Small Molecular Acceptors with Non‐Aromatic π‐Conjugated Linkers for Efficient All‐Polymer Solar Cells
Authors: Zhang Zhe , Li Zhixiang , Wang Peiran , Chen Hongbin , Ma Kangqiao , Zhang Yunxin , Duan Tainan , Li Chenxi , Yao Zhaoyang , Kan Bin , Wan Xiangjian , Chen Yongsheng
Published: March 2023

Developing new polymerized small molecular acceptor (PSMA) is pivotal for improving the performance of all‐polymer solar cells. On the basis of this newly developed CH‐series small molecule acceptors, two PSMAs are reported herein (namely PZC16 and PZC17, respectively). To reduce the molecular torsion caused by the traditional aromatic π‐bridges, non‐aromatic conjugated units (ethynyl for PZC16 and vinylene for PZC17) are adopted as the linkers and their effect on the photo‐physical properties as well as the device performance are systematically investigated. Both polymer acceptors exhibit co‐planar molecular conformation, along with broad absorption ranges and suitable energy levels. In comparison with the PM6:PZC16 film, the PM6:PZC17 film exhibits more uniform phase separation in morphology with a distinct bi‐continuous network and better crystallinity. The PM6:PZC17‐binary‐based devices exhibit a satisfactory PCE of 16.33%, significantly higher than 9.22% of the PZC16‐based devices. Impressively, PM6:PZC17‐based large area device (ca. 1 cm2) achieves an excellent PCE of 15.14%, which is among the top performance for reported all‐polymer solar cells (all‐PSCs).
Regulating the Unhybridized O 2p Orbitals of High‐Performance Li‐Rich Mn‐Based Layered Oxide Cathode by Gd‐Doping Induced Bulk Oxygen Vacancies
Authors: Xu Jia , Wan Jing , Zhang Wen , Li Yuyu , Cheng Fangyuan , Cheng Zexiao , Xu Yue , Sun Shixiong , Li Qing , Fang Chun , Han Jiantao
Published: March 2023

Li‐rich Mn‐based layered oxides (LRLOs) with ultrahigh specific capacities are promising cathode materials for high energy density lithium‐ion batteries. Nevertheless, severe irreversible oxygen release, structure degradation, capacity and voltage attenuation hinder their commercialization due to the uncontrollable oxygen redox chemistry originated from unhybridized O 2p orbitals. Herein, a strategy to generate bulk oxygen vacancies is proposed. And bulk oxygen vacancies are constructed by lowering the formation energy of oxygen vacancies in LRLOs via Gd‐doping. The energy level and the amount of unhybridized O 2p states are reduced to partly inhibit the oxygen redox activity. Surprisingly, the oxygen redox is not fully activated in the first cycle and is further activated in the second cycle. Moreover, the reduced oxygen redox activity significantly suppresses the oxygen release, lattice volume change, layered‐to‐spinel phase transition. As a result, the amount of oxygen gas release is reduced from 98.80 to ≈0 nmol mg−1 in the first cycle. Superior cycle stability of 90.4% capacity retention after 300 cycles and small voltage decay of only 1.013 mV per cycle are achieved. This study provides a valuable bulk oxygen vacancies strategy to regulate the unhybridized O 2p orbitals for designing high‐performance Li‐rich Mn‐based layered oxide cathode materials.
Toward High Conversion Efficiency of Thermoelectric Modules through Synergistical Optimization of Layered Materials
Authors: Li Wenjie , Poudel Bed , Kishore Ravi Anant , Nozariasbmarz Amin , Liu Na , Zhang Yu , Priya Shashank
Published: March 2023

Waste‐heat electricity generation using high‐efficiency solid‐state conversion technology can significantly decrease dependence on fossil fuels. Here, a synergistical optimization of layered half‐Heusler (hH) materials and module to improve thermoelectric conversion efficiency is reported. This is realized by manufacturing multiple thermoelectric materials with major compositional variations and temperature‐gradient‐coupled carrier distribution by one‐step spark plasma sintering. This strategy provides a solution to overcome the intrinsic concomitants of the conventional segmented architecture that only considers the matching of the figure of merit (zT) with the temperature gradient. The current design is dedicated to temperature‐gradient‐coupled resistivity and compatibility matching, optimum zT matching, and reducing contact resistance sources. By enhancing the quality factor of the materials by Sb‐vapor‐pressure‐induced annealing, a superior zT of 1.47 at 973 K is achieved for (Nb, Hf)FeSb hH alloys. Along with the low‐temperature high‐zT hH alloys of (Nb, Ta, Ti, V)FeSb, the single stage layered hH modules are developed with efficiencies of ≈15.2% and ≈13.5% for the single‐leg and unicouple thermoelectric modules, respectively, under ΔT of 670 K. Therefore, this work has a transformative impact on the design and development of next‐generation thermoelectric generators for any thermoelectric material families.
Efficient and Stable Perovskite Solar Cells by Tailoring of Interfaces
Authors: Xia Jianxing , Sohail Muhammad , Nazeeruddin Mohammad Khaja
Published: March 2023

The interface tailoring is crucial for the efficiency and stability of Perovskite Solar Cells (PSCs). The reported interface engineering primarily focuses on the energy level turning and trap state passivation to improve the photovoltaic performance of PSCs. In this review, molecule modifications are classified according to the basics of electron transfer mechanisms for the interface tailoring of materials. An in‐depth analysis of energy level modification and trap passivation, as well as the universal Density Functional Theory (DFT) method employed in interface tailoring. In addition, strategies to address environmental protection and large‐scale mini‐modules fabrication by interface engineering are also discussed. This review can guide the researchers in understanding interface engineering to design interface materials for efficient, stable, and eco‐friendly PSCs.
Two Functions from a Single Photoresist: Tuning Microstructure Degradability from Light‐Stabilized Dynamic Materials
Authors: Gauci Steven C. , Ehrmann Katharina , Gernhardt Marvin , Tuten Bryan , Blasco Eva , Frisch Hendrik , Jayalatharachchi Vishakya , Blinco James P. , Houck Hannes A. , Barner‐Kowollik Christopher
Published: March 2023

A photoresist—based on a light‐stabilized dynamic material driven by an out‐of‐equilibrium photo‐Diels–Alder reaction of triazolinediones with naphthalenes—whose ability to intrinsically degrade postprinting can be tuned by a simple adjustment of laser intensity during 3D laser lithography is introduced. The resist's ability to form stable networks under green light irradiation that degrade in the dark is transformed into a tunable degradable 3D printing material platform. In‐depth characterization of the printed microstructures via atomic force microscopy before and during degradation reveals the high dependency of the final structures’ properties on the writing parameters. Upon identifying the ideal writing parameters and their effect on the network structure, it is possible to selectively toggle between stable and fully degradable structures. This simplifies the direct laser writing manufacturing process of multifunctional materials significantly, which typically requires the use of separate resists and consecutive writing efforts to achieve degradable and nondegradable material sections.
Achieving Ferroelectricity in a Centrosymmetric High‐Performance Semiconductor by Strain Engineering
Authors: Wu Mengqi , Lou Zhefeng , Dai Chen‐Min , Wang Tao , Wang Jiaqi , Zhu Ziye , Xu Zhuokai , Sun Tulai , Li Wenbin , Zheng Xiaorui , Lin Xiao
Published: March 2023

Phase engineering by strain in 2D semiconductors is of great importance for a variety of applications. Here, a study of the strain‐induced ferroelectric (FE) transition in bismuth oxyselenide (Bi2O2Se) films, a high‐performance (HP) semiconductor for next‐generation electronics, is presented. Bi2O2Se is not FE at ambient pressure. At a loading force of ≳400 nN, the piezoelectric force responses exhibit butterfly loops in magnitude and 180° phase switching. By carefully ruling out extrinsic factors, these features are attributed to a transition to the FE phase. The transition is further supported by the appearance of a sharp peak in optical second‐harmonic generation under uniaxial strain. In general, solids with paraelectrics at ambient pressure and FE under strain are rare. The FE transition is discussed using first‐principles calculations and theoretical simulations. The switching of FE polarization acts as a knob for Schottky barrier engineering at contacts and serves as the basis for a memristor with a huge on/off current ratio of 106. This work adds a new degree of freedom to HP electronic/optoelectronic semiconductors, and the integration of FE and HP semiconductivity paves the way for many exciting functionalities, including HP neuromorphic computing and bulk piezophotovoltaics.
Design and Modification of Janus Polyvinylidene Fluoride/Deacetylated Cellulose Acetate Nanofiber Membrane and its Multifunctionality
Authors: Si Junhui , Zhao Mingliang , Marcelle Sansi seukep alix , Wang Qianting , Cui Zhixiang , Liu Xiaolong
Published: March 2023

A novel type of Janus polyvinylidene fluoride/deacetylated cellulose acetate (PVDF/D‐CA) nanofiber membrane with multifunctional application is successfully fabricated by sequential electrospinning. The morphology, chemical composition, surface wettability, oil–water separation performance, and unidirectional liquid transmission capability have been systematically analyzed. It has asymmetric wettability property in air and in liquid systems for its bottom and top sides. It can be used as a water‐removing, or oil‐removing substance for oil–water mixture and emulsion under a harsh environment only under gravity driving force (DF) by simply switching the different sides. It possesses on‐demand water and oil collection ability, and moisture‐wicking performance due to its switchable permeation and unidirectional liquid transmission capability. Its multifunction application can be easy to control by adjusting the thickness of the top and bottom sides through controlling the electrospinning time. Its excellent mechanical property, chemical stability, durability under harsh environment and outstanding anti‐pollution ability endow the membrane with powerful cyclic stability and reusability.
Role of Tellurium Ions for Electrochemically Synthesized Zinc Telluride 2D Structures on Nonconductive Substrate
Authors: Seo Jinmyeong , Yoon Sanghwa , Park Kimoon , Park Jung‐Joon , Kim Jiwon , Yoo Bongyoung
Published: March 2023

Although electrodeposition has emerged as a promising approach to make metal chalcogenide nanostructures, it has an underlying issue of exfoliating the deposits affixed to a conductive substrate, which is inevitable to transfer electrons for a reduction reaction, for precise characterization and advanced device fabrication. Herein, direct electrodeposition of metal chalcogenides on a silicon dioxide (SiO2) insulator and its device applications for a back‐gated field‐effect‐transistor and a nitrogen dioxide gas sensor are investigated. Tellurium metal nanorods are deposited on SiO2 by the redox reaction of tellurium substances in the electrolyte. Using underpotential deposition, zinc telluride (ZnTe) is propagated onto tellurium sites, which has deposited on SiO2, bridging the microgap electrode on SiO2. The growth mechanisms of ZnTe on the SiO2 are also explored. This finding addresses the major challenge associated with the electrodeposition by the successful deposition of complex chalcogenides on an insulating substrate that expands its applications in fields for advanced electronics.
Electrochemical Lithium Insertion into TiO2 Anatase ALD Thin Films for Li‐Ion Microbatteries: An Atomic‐Scale Picture Provided by Raman Spectroscopy
Authors: Bhatia Ankush , Hallot Maxime , Leviel Clément , Roussel Pascal , Pereira‐Ramos Jean‐Pierre , Lethien Christophe , Baddour‐Hadjean Rita
Published: March 2023

Electrochemical lithium (de)intercalation in an atomic layer deposited (ALD) TiO2 anatase thin film deposited on a planar Si /Al2O3/Pt substrate is investigated by Raman spectroscopy. An initial discharge capacity of 63 µAh cm−2 µm−1 (0.5 Li+ mole−1) is reached at C/10 rate, which increases up to 77 µAh cm−2 µm−1 upon further cycles. An excellent capacity retention is achieved over at least 100 cycles, showing the good adherence of the ALD thin film. Raman spectra of LixTiO2 (0 ≤ x ≤ 0.5) thin film electrodes point to the nucleation of the orthorhombic lithiated titanate (LT) Li0.5TiO2 phase from x = 0.1. This LT phase coexists with tetragonal TiO2 in the 0.1 ≤ x ≤ 0.4 composition domain to be pure for x = 0.5. A fully reversible transformation from orthorhombic LT to tetragonal TiO2 is observed upon the charge. The high quality of the Raman spectra allows identifying for the first time 12 modes in the 100–800 cm−1 region for the electrochemically formed LT phase. Furthermore, an appropriate Raman spectra analysis allows a reliable and quantitative determination of the thin film composition during discharge and charge. These results illustrate Raman spectroscopy is a powerful probe to scrutinize the Li insertion/extraction mechanism in TiO2 thin films.