bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscoelastic properties of collagen: synchrotron radiation investigations and structural model
Authors: Puxkandl R. , Zizak I. , Paris O. , Keckes J. , Tesch W. , Bernstorff S. , Purslow P. , Fratzl P.
Published: July 2002

Collagen type I is the most abundant structural protein in tendon, skin and bone, and largely determines the mechanical behaviour of these connective tissues. To obtain a better understanding of the relationship between structure and mechanical properties, tensile tests and synchrotron X–ray scattering have been carried out simultaneously, correlating the mechanical behaviour with changes in the microstructure. Because intermolecular cross–links are thought to have a great influence on the mechanical behaviour of collagen, we also carried out experiments using cross–link–deficient tail–tendon collagen from rats fed with β–APN, in addition to normal controls.

The load–elongation curve of tendon collagen has a characteristic shape with, initially, an increasing slope, corresponding to an increasing stiffness, followed by yielding and then fracture. Cross–link–deficient collagen produces a quite different curve with a marked plateau appearing in some cases, where the length of the tendon increases at constant stress. With the use of
in situ
X–ray diffraction, it was possible to measure simultaneously the elongation of the collagen fibrils inside the tendon and of the tendon as a whole. The overall strain of the tendon was always larger than the strain in the individual fibrils, which demonstrates that some deformation is taking place in the matrix between fibrils. Moreover, the ratio of fibril strain to tendon strain was dependent on the applied strain rate. When the speed of deformation was increased, this ratio increased in normal collagen but generally decreased in cross–link–deficient collagen, correlating to the appearance of a plateau in the force–elongation curve indicating creep.

We proposed a simple structural model, which describes the tendon at a hierarchical level, where fibrils and interfibrillar matrix act as coupled viscoelastic systems. All qualitative features of the strain–rate dependence of both normal and cross–link–deficient collagen can be reproduced within this model. This complements earlier models that considered the next smallest level of hierarchy, describing the deformation of collagen fibrils in terms of changes in their molecular packing.
Activator-mediated disruption of sequence-specific DNA contacts by the general transcription factor TFIIB
Authors: Evans Rachel , Fairley Jennifer A. , Roberts Stefan G.E.
Published: July 2002

The transcription factor TFIIB plays a central role in preinitiation complex assembly, providing a bridge between promoter-bound TFIID and RNA Polymerase II. TFIIB possesses sequence-specific DNA-binding ability and interacts with the TFIIB-recognition element (BRE), present in many promoters. Here we show that the BRE suppresses the basal level of transcription elicited by a core promoter, which increases the amplitude of transcriptional stimulation in the presence of an activator protein. Further, we find that an activator can disrupt the TFIIB–BRE interaction within a promoter-bound complex. Our results reveal a novel function for activators in the modulation of core promoter recognition by TFIIB.
A complex containing CstF-64 and the SL2 snRNP connects mRNA 3′ end formation and trans-splicing in C. elegans operons
Authors: Evans Donald , Perez Ismael , MacMorris Margaret , Leake Devin , Wilusz Carol J. , Blumenthal Thomas
Published: July 2002

Polycistronic pre-mRNAs from Caenorhabditis elegans are processed by 3′ end formation of the upstream mRNA and SL2-specifictrans-splicing of the downstream mRNA. These processes usually occur within an ∼100-nucleotide region and are mechanistically coupled. In this paper, we report a complex in C. elegansextracts containing the 3′ end formation protein CstF-64 and the SL2 snRNP. This complex, immunoprecipitated with αCstF-64 antibody, contains SL2 RNA, but not SL1 RNA or other U snRNAs. Using mutational analysis we have been able to uncouple SL2 snRNP function and identity. SL2 RNA with a mutation in stem/loop III is functional in vivo as atrans-splice donor, but fails to splice to SL2-acceptingtrans-splice sites, suggesting that it has lost its identity as an SL2 snRNP. Importantly, stem/loop III mutations prevent association of SL2 RNA with CstF-64. In contrast, a mutation in stem II that inactivates the SL2 snRNP still permits complex formation with CstF-64. Therefore, SL2 RNA stem/loop III is required for both SL2 identity and formation of a complex containing CstF-64, but not fortrans-splicing. These results provide a molecular framework for the coupling of 3′ end formation and trans-splicing in the processing of polycistronic pre-mRNAs from C. elegans operons.
Systematic Identification of Novel Protein Domain Families Associated with Nuclear Functions
Authors: Doerks Tobias , Copley Richard R. , Schultz Jörg , Ponting Chris P. , Bork Peer
Published: July 2002

A systematic computational analysis of protein sequences containing known nuclear domains led to the identification of 28 novel domain families. This represents a 26% increase in the starting set of 107 known nuclear domain families used for the analysis. Most of the novel domains are present in all major eukaryotic lineages, but 3 are species specific. For about 500 of the 1200 proteins that contain these new domains, nuclear localization could be inferred, and for 700, additional features could be predicted. For example, we identified a new domain, likely to have a role downstream of the unfolded protein response; a nematode-specific signalling domain; and a widespread domain, likely to be a noncatalytic homolog of ubiquitin-conjugating enzymes.
Complex behavior in solution of homodimeric SecA
Authors: Woodbury Ronald L. , Hardy Simon J.S. , Randall Linda L.
Published: July 2002

SecA, a homodimeric protein involved in protein export in Escherichia coli, exists in the cell both associated with the membrane translocation apparatus and free in the cytosol. SecA is a multifunctional protein involved in protein localization and regulation of its own expression. To carry out these functions, SecA interacts with a variety of proteins, phospholipids, nucleotides, and nucleic acid and shows two enzymic activities. It is an ATPase and a helicase. Its role during protein localization involves interaction with the precursor polypeptides to be exported, the cytosolic chaperone SecB, and the SecY subunit of the membrane‐associated translocase, as well as with acidic phospholipids. At the membrane, SecA undergoes a cycle of binding and hydrolysis of ATP coupled to conformational changes that result in translocation of precursors through the cytoplasmic membrane. The helicase activity of SecA and its affinity for its mRNA are involved in regulation of its own expression. SecA has been reported to exist in at least two conformational states during its functional cycle. Here we have used analytical centrifugation, as well as column chromatography coupled with multiangle light scatter, to show that in solution SecA undergoes at least two monomer‐dimer equilibrium reactions that are sensitive to temperature and to concentration of salt.
Toward a final design for the Birmingham boron neutron capture therapy neutron beam
Authors: Allen D. A. , Beynon T. D. , Green S. , James N. D.
Published: July 2002

This paper is concerned with the proposed Birmingham accelerator‐based epithermal neutron beam for boron neutron capture therapy (BNCT). Details of the final moderator design, such as beam delimiter, shield, and beam exit surface shape are considered. Monte Carlo radiation transport simulations with a head and body phantom have shown that a simple flat moderator beam exit surface is preferable to the previously envisioned spherical design. Dose rates to individual body organs during treatment have been calculated using a standard MIRD phantom. We have shown that a simple polyethylene shield, doped with natural lithium, is sufficient to provide adequate protection to the rest of the body during head irradiations. The effect upon the head phantom dose distributions of the use of such a shield to delimit the therapy beam has been evaluated.
Dynamics of the baseball–bat collision
Authors: Nathan Alan M.
Published: July 2002

A model is developed for the collision between the baseball and bat, taking into account the transverse bending vibrations of the bat. By coupling the flexible bat to the ball via a parametrized force that each mutually exerts on the other, a complete description of the collision process is obtained, including the exit speed of the ball vf. It is shown that vibrations play an important role in determining vf. The model is in excellent agreement with experimental data at low impact velocities. At the higher velocities more appropriate to the game of baseball, vf is shown to coincide with the rigid-body value only over a very small region in the barrel of the bat and to drop off sharply for impacts removed from that region. Some interesting insights into the collision process are obtained, including the observation that for impacts in the barrel of the bat, the momentum transferred to the ball is essentially complete by the time the elastic wave first arrives at the handle and that any clamping action of the hands will affect the bat at the impact point only after the ball and bat have separated. This suggests that vf is independent of the size, shape, and method of support of the bat at distances far from the impact location.
Measurements of the horizontal coefficient of restitution for a superball and a tennis ball
Authors: Cross Rod
Published: July 2002

When a ball is incident obliquely on a flat surface, the rebound spin, speed, and angle generally differ from the corresponding incident values. Measurements of all three quantities were made using a digital video camera to film the bounce of a tennis ball incident with zero spin at various angles on several different surfaces. The maximum spin rate of a spherical ball is determined by the condition that the ball commences to roll at the end of the impact. Under some conditions, the ball was found to spin faster than this limit. This result can be explained if the ball or the surface stores energy elastically due to deformation in a direction parallel to the surface. The latter effect was investigated by comparing the bounce of a tennis ball with that of a superball. Ideally, the coefficient of restitution (COR) of a superball is 1.0 in both the vertical and horizontal directions. The COR for the superball studied was found to be 0.76 in the horizontal direction, and the corresponding COR for a tennis ball was found to vary from −0.51 to +0.24 depending on the incident angle and the coefficient of sliding friction.
The bounce of a ball
Authors: Cross Rod
Published: July 2002

In this paper, the dynamics of a bouncing ball is described for several common ball types having different bounce characteristics. Results are presented for a tennis ball, a baseball, a golf ball, a superball, a steel ball bearing, a plasticene ball, and a silly putty ball. The plasticene ball was studied as an extreme case of a ball with a low coefficient of restitution (in fact zero, since the collision is totally inelastic) and the silly putty ball was studied because it has unusual elastic properties. The first three balls were studied because of their significance in the physics of sports. For each ball, a dynamic hysteresis curve is presented to show how energy is lost during and after the collision. The measurement technique is quite simple, it is suited for undergraduate laboratory experiments, and it may provide a useful method to test and approve balls for major sporting events.
Backscatter of high-frequency (200 kHz) acoustic wavefields from ocean turbulence
Authors: Orr Marshall H. , Haury Loren R. , Wiebe Peter H. , Briscoe Melbourne G.
Published: July 2002

Near space and time coincident 200-kHz acoustic backscatter and CTD measurements were taken during an interdisciplinary study of the internal wave packets that propagate through Massachusetts Bay. The data strongly support the contention that acoustic wavefields can be backscattered from turbulent mixing events (microstructure) associated with the internal wave packets.
The use of visible speech cues for improving auditory detection of spoken sentences
Authors: Grant Ken W. , Seitz Philip-Franz
Published: July 2002

Classic accounts of the benefits of speechreading to speech recognition treat auditory and visual channels as independent sources of information that are integrated fairly early in the speech perception process. The primary question addressed in this study was whether visible movements of the speech articulators could be used to improve the detection of speech in noise, thus demonstrating an influence of speechreading on the ability to detect, rather than recognize, speech. In the first experiment, ten normal-hearing subjects detected the presence of three known spoken sentences in noise under three conditions: auditory-only (A), auditory plus speechreading with a visually matched sentence (AVM) and auditory plus speechreading with a visually unmatched sentence (AVUM). When the speechread sentence matched the target sentence, average detection thresholds improved by about 1.6 dB relative to the auditory condition. However, the amount of threshold reduction varied significantly for the three target sentences (from 0.8 to 2.2 dB). There was no difference in detection thresholds between the AVUM condition and the A condition. In a second experiment, the effects of visually matched orthographic stimuli on detection thresholds was examined for the same three target sentences in six subjects who participated in the earlier experiment. When the orthographic stimuli were presented just prior to each trial, average detection thresholds improved by about 0.5 dB relative to the A condition. However, unlike the AVM condition, the detection improvement due to orthography was not dependent on the target sentence. Analyses of correlations between area of mouth opening and acoustic envelopes derived from selected spectral regions of each sentence (corresponding to the wide-band speech, and first, second, and third formant regions) suggested that AVM threshold reduction may be determined by the degree of auditory-visual temporal coherence, especially between the area of lip opening and the envelope derived from mid- to high-frequency acoustic energy. Taken together, the data (for these sentences at least) suggest that visual cues derived from the dynamic movements of the fact during speech production interact with time-aligned auditory cues to enhance sensitivity in auditory detection. The amount of visual influence depends in part on the degree of correlation between acoustic envelopes and visible movement of the articulators.
Optimal focusing by spatio-temporal inverse filter. I. Basic principles
Authors: Tanter M. , Aubry J.-F. , Gerber J. , Thomas J.-L. , Fink M.
Published: July 2002

A focusing technique based on the inversion of the propagation operator relating an array of transducers to a set of control points inside a medium was proposed in previous work [Tanter et al., J. Acoust. Soc. Am. 108, 223–234 (2000)] and is extended here to the time domain. As the inversion of the propagation operator is achieved both in space and time, this technique allows calculation of the set of temporal signals to be emitted by each element of the array in order to optimally focus on a chosen control point. This broadband inversion process takes advantage of the singular-value decomposition of the propagation operator in the Fourier domain. The physical meaning of this decomposition is explained in a homogeneous medium. In particular, a definition of the number of degrees of freedom necessary to define the acoustic field generated by an array of limited aperture in a focal plane of limited extent is given. This number corresponds to the number of independent signals that can be created in the focal area both in space and time. In this paper, this broadband inverse-focusing technique is compared in homogeneous media with the classical focusing achieved by simple geometrical considerations but also with time-reversal focusing. It is shown that, even in a simple medium, slight differences appear between these three focusing strategies. In the companion paper [Aubry et al., J. Acoust. Soc. Am. 110, 48–58 (2001)] the three focusing techniques are compared in heterogeneous, absorbing, or complex media where classical focusing is strongly degraded. The strong improvement achieved by the spatio-temporal inverse-filter technique emphasizes the great potential of multiple-channel systems having the ability to apply completely different signal waveforms on each transducer of the array. The application of this focusing technique could be of great interest in various ultrasonic fields such as medical imaging, nondestructive testing, and underwater acoustics.
Active control of road booming noise in automotive interiors
Authors: Oh Shi-Hwan , Kim Hyoun-suk , Park Youngjin
Published: July 2002

An active feedforward control system has been developed to reduce the road booming noise that has strong nonlinear characteristics. Four acceleration transducers were attached to the suspension system to detect reference vibration and two loudspeakers were used to attenuate the noise near the headrests of two front seats. A leaky constraint multiple filtered-X LMS algorithm with an IIR-based filter that has fast convergence speed and frequency selective controllability was proposed to increase the control efficiency in computing power and memory usage. During the test drive on the rough asphalt and turtle-back road at a constant speed of 60 km/h, we were able to achieve a reduction of around 6 dB of A-weighted sound pressure level in the road booming noise range with the proposed algorithm, which could not be obtained with the conventional multiple filtered-X LMS algorithm.
Real-time nondestructive evaluation of fiber composite laminates using low-frequency Lamb waves
Authors: Dı́az Valdés Sergio H. , Soutis Costas
Published: July 2002

Amid the nondestructive evaluation techniques available for the inspection of composite materials, only a few are suitable for implementation while the component is in service. The investigation examines the application of Lamb waves at low-frequency–thickness products for the detection of delaminations in thick composite laminates. Surface-mounted piezoelectric devices were excited with a tone burst to generate elastic waves in the structure. Experiments were carried out on composite beam specimens where wave propagation distances over 2 m were achieved and artificially induced delaminations as small as 1 cm2 were successfully identified. The feasibility of employing piezoelectric devices for the development of smart structures, where a small and lightweight transducer system design is required, has been demonstrated. The resonance spectrum method, which is based on the study of spectra obtained by forced mechanical resonance of samples using sine-sweep excitation, has been proposed as a technique for measuring the Ao Lamb mode phase velocity. The finite-element method was also used to investigate qualitatively the dynamic response of laminates to wave propagation. Several locations and spatial distribution of the actuators were examined showing the advantages of using transducers arrays for the inspection of large structures.
The schlieren image of two-dimensional ultrasonic fields and cavity resonances
Authors: Chinnery Paul A. , Humphrey Victor F. , Beckett Carolyn
Published: July 2002

The schlieren technique can be used to visualize the two-dimensional ultrasonic standing wave fields associated with circular cylindrical shells under resonance conditions. However, the interpretation of the schlieren image is not simple due to the complex relationship between the acoustic and optical fields. A model for predicting the optical image in an ideal schlieren system is presented and used to investigate the influence of the acoustic pressure and optical spatial filtering on the resultant image, demonstrating the conditions under which the image is a meaningful representation of the acoustic wave field. A low-frequency (>100 kHz), wide-aperture, laboratory schlieren system is used to image the fluid column resonances of a circular cylindrical shell. Experimental results agree well with the predictions, validating the theory. Although the schlieren image is two-dimensional, limiting investigations to targets having translational symmetry, the technique is noninvasive and can potentially provide greater insight into the acoustic resonance behavior of more complex scattering geometries.
Coarticulatory stability in American English /r/
Authors: Boyce Suzanne , Espy-Wilson Carol Y.
Published: July 2002

A number of different researchers have reported a substantial degree of variability in how American English /r/ coarticulates with neighboring segments. Acoustic and articulatory data were used to investigate this variability for speakers of “rhotic” American English dialects. Three issues were addressed: (1) the degree to which the F3 trajectory is affected by segmental context and stress, (2) to what extent the data support a “coproduction” versus a “spreading” model of coarticulation, and (3) the degree to which the major acoustic manifestation of American English /r/—the time course of F3—reflects tongue movement for /r/. The F3 formant trajectory durations were measured by automatic procedure and compared for nonsense words of the form /’waCrav/ and /wa’Crav/, where C indicates a labial, alveolar, or velar consonant. These durations were compared to F3 trajectory durations in /’warav/ and /wa’rav/. In addition, formant values in initial syllables of words with and without /r/ were examined for effects of intervening consonant contexts. Results indicated similar F3 trajectory durations across the different consonant contexts, and to a lesser degree across stress, suggesting that coarticulation of /r/ can be achieved by overlap of a stable /r/-related articulatory trajectory with movements for neighboring sounds. This interpretation, and the concordance of F3 time course with tongue movement for /r/, was supported by direct measures of tongue movement for one subject.
Nonlinear distortion of short pulses radiated by plane and focused circular pistons
Authors: Averkiou Michalakis A. , Hamilton Mark F.
Published: July 2002

Detailed measurements of finite-amplitude pulses radiated by plane and focused circular pistons in water are presented. Comparisons of time waveforms and frequency spectra, both on and off axis, are made with numerical calculations based on the nonlinear parabolic wave equation. Emphasis is on nonlinear distortion of amplitude- and frequency-modulated tone bursts. Use of short pulses enabled resolution of the direct and diffracted waves prior to their coalescence and subsequent shock formation along the axis of the source. Because of its relevance to investigations of cavitation inception, attention is devoted to variation of the peak positive (p+) and negative (p−) pressures along the axis of a focused source. It is shown that with increasing source amplitude, the maximum of each shifts away from the focal plane, toward the source. This effect is more pronounced for p−than for p+.
The effects of sensory hearing loss on cochlear filter times estimated from auditory brainstem response latencies
Authors: Don Manuel , Ponton Curtis W. , Eggermont Jos J. , Kwong Betty
Published: July 2002

Derived-band auditory brainstem responses (ABRs) were obtained in 43 normal-hearing and 80 cochlear hearing-impaired individuals using clicks and high-pass noise masking. The response times across the cochlea [the latency difference between wave V’s of the 5.7- and 1.4-kHz center frequency (CF) derived bands] were calculated for five levels of click stimulation ranging from 53 to 93 dB p.-p.e. SPL (23 to 63 dB nHL) in 10-dB steps. Cochlear response times appeared to shorten significantly with hearing loss, especially when the average pure tone (1 to 8 kHz) hearing loss exceeded 30 dB. Examination of derived-band latencies indicates that this shortening is due to a dramatic decrease of wave V latency in the lower CF derived band. Estimates of cochlear filter times in terms of the number of periods to maximum response (Nmax) were calculated from derived-band latencies corrected for gender-dependent cochlear transport and neural conduction times. Nmax decreased as a function of hearing loss, especially for the low CF derived bands. The functions were similar for both males and females. These results are consistent with broader cochlear tuning due to peripheral hearing loss. Estimating filter response times from ABR latencies enhances objective noninvasive diagnosis and allows delineation of the differential effects of pathology on the underlying cochlear mechanisms involved in cochlear transport and filter build-up times.
Speech recognition with altered spectral distribution of envelope cues
Authors: Shannon Robert V. , Zeng Fan-Gang , Wygonski John
Published: July 2002

Recognition of consonants, vowels, and sentences was measured in conditions of reduced spectral resolution and distorted spectral distribution of temporal envelope cues. Speech materials were processed through four bandpass filters (analysis bands), half-wave rectified, and low-pass filtered to extract the temporal envelope from each band. The envelope from each speech band modulated a band-limited noise (carrier bands). Analysis and carrier bands were manipulated independently to alter the spectral distribution of envelope cues. Experiment I demonstrated that the location of the cutoff frequencies defining the bands was not a critical parameter for speech recognition, as long as the analysis and carrier bands were matched in frequency extent. Experiment II demonstrated a dramatic decrease in performance when the analysis and carrier bands did not match in frequency extent, which resulted in a warping of the spectral distribution of envelope cues. Experiment III demonstrated a large decrease in performance when the carrier bands were shifted in frequency, mimicking the basal position of electrodes in a cochlear implant. And experiment IV showed a relatively minor effect of the overlap in the noise carrier bands, simulating the overlap in neural populations responding to adjacent electrodes in a cochlear implant. Overall, these results show that, for four bands, the frequency alignment of the analysis bands and carrier bands is critical for good performance, while the exact frequency divisions and overlap in carrier bands are not as critical.
Fiber movements and sound attenuation in glass wool
Authors: Tarnow Viggo
Published: July 2002

Propagation of a plane harmonic sound wave in fiber materials such as glass wool is studied theoretically and experimentally. Wave equations are set up that take into account the movement of the fiber skeleton. The attenuation of the sound wave in slabs of glass wool was calculated and measured. The main new result is that the experimental attenuation of a low-frequency propagating wave is lower when the fibers move. For a wave with frequency 100 Hz in glass wool of density 30 kg/m3, the attenuation of a layer of thickness 0.20 m is 4 dB if the fibers move, and 12 dB if they do not move. The attenuation was computed from the fiber diameters and their density, which was found from the mass density. Measured attenuation is lower than the values calculated. Nevertheless, if the density is adjusted, a complete fit is obtained between experimental and theoretical values for frequencies 50–5000 Hz.
Constrained adaptation for feedback cancellation in hearing aids
Authors: Kates James M.
Published: July 2002

In feedback cancellation in hearing aids, an adaptive filter is used to model the feedback path. The output of the adaptive filter is subtracted from the microphone signal to cancel the acoustic and mechanical feedback picked up by the microphone, thus allowing more gain in the hearing aid. In general, the feedback-cancellation filter adapts on the hearing-aid input signal, and signal cancellation and coloration artifacts can occur for a narrow-band input. In this paper, two procedures for LMS adaptation with a constraint on the magnitude of the adaptive weight vector are derived. The constraints greatly reduce the probability that the adaptive filter will cancel a narrow-band input. Simulation results are used to demonstrate the efficacy of the constrained adaptation.
A self-consistent theory for seabed volume scattering
Authors: Tracey Brian H. , Schmidt Henrik
Published: July 2002

A self-consistent perturbation method for three-dimensional acoustic scattering due to sound speed and density fluctuations is developed below. This method allows calculation of mean-field attenuation due to scattering, as well as second-moment statistics of the scattered field. Scattering from an inhomogeneous sediment bottom in shallow water is considered as an application. The power spectral density of the scattered field is calculated and used to study the effects of fluctuation statistics. Modal attenuation due to scattering is then calculated for several shallow-water scenarios. The scattering loss calculation is straightforward and is suitable for use with standard normal-mode codes. Numerical results show the influence of the statistical model used to represent bottom randomness and demonstrate the importance of scattering into the continuous spectrum. Scattering loss predictions are shown to agree well with a previous wave number-integration approach.
Adaptation by normal listeners to upward spectral shifts of speech: Implications for cochlear implants
Authors: Rosen Stuart , Faulkner Andrew , Wilkinson Lucy
Published: July 2002

Multi-channel cochlear implants typically present spectral information to the wrong “place” in the auditory nerve array, because electrodes can only be inserted partway into the cochlea. Although such spectral shifts are known to cause large immediate decrements in performance in simulations, the extent to which listeners can adapt to such shifts has yet to be investigated. Here, the effects of a four-channel implant in normal listeners have been simulated, and performance tested with unshifted spectral information and with the equivalent of a 6.5-mm basalward shift on the basilar membrane (1.3–2.9 octaves, depending on frequency). As expected, the unshifted simulation led to relatively high levels of mean performance (e.g., 64% of words in sentences correctly identified) whereas the shifted simulation led to very poor results (e.g., 1% of words). However, after just nine 20-min sessions of connected discourse tracking with the shifted simulation, performance improved significantly for the identification of intervocalic consonants, medial vowels in monosyllables, and words in sentences (30% of words). Also, listeners were able to track connected discourse of shifted signals without lipreading at rates up to 40 words per minute. Although we do not know if complete adaptation to the shifted signals is possible, it is clear that short-term experiments seriously exaggerate the long-term consequences of such spectral shifts.
Modified impulse method for the measurement of the frequency response of acoustic filters to weakly nonlinear transient excitations
Authors: Payri F. , Desantes J. M. , Broatch A.
Published: July 2002

In this paper, a modified impulse method is proposed which allows the determination of the influence of the excitation characteristics on acoustic filter performance. Issues related to nonlinear propagation, namely wave steepening and wave interactions, have been addressed in an approximate way, validated against one-dimensional unsteady nonlinear flow calculations. The results obtained for expansion chambers and extended duct resonators indicate that the amplitude threshold for the onset of nonlinear phenomena is related to the geometry considered.
A high-precision magnetoencephalographic study of human auditory steady-state responses to amplitude-modulated tones
Authors: Roß Bernhard , Borgmann Christian , Draganova Rossitza , Roberts Larry E. , Pantev Christo
Published: July 2002

The cerebral magnetic field of the auditory steady-state response (SSR) to sinusoidal amplitude-modulated (SAM) tones was recorded in healthy humans. The waveforms of underlying cortical source activity were calculated at multiples of the modulation frequency using the method of source space projection, which improved the signal-to-noise ratio (SNR) by a factor of 2 to 4. Since the complex amplitudes of the cortical source activity were independent of the sensor position in relation to the subject’s head, a comparison of the results across experimental sessions was possible. The effect of modulation frequency on the amplitude and phase of the SSR was investigated at 30 different values between 10 and 98 Hz. At modulation frequencies between 10 and 20 Hz the SNR of harmonics near 40 Hz were predominant over the fundamental SSR. Above 30 Hz the SSR showed an almost sinusoidal waveform with an amplitude maximum at 40 Hz. The amplitude decreased with increasing modulation frequency but was significantly different from the magnetoencephalographic (MEG) background activity up to 98 Hz. Phase response at the fundamental and first harmonic decreased monotonically with increasing modulation frequency. The group delay (apparent latency) showed peaks of 72 ms at 20 Hz, 48 ms at 40 Hz, and 26 ms at 80 Hz. The effects of stimulus intensity, modulation depth, and carrier frequency on amplitude and phase of the SSR were also investigated. The SSR amplitude decreased linearly when stimulus intensity or the modulation depth were decreased in logarithmic steps. SSR amplitude decreased by a factor of 3 when carrier frequency increased from 250 to 4000 Hz. From the phase characteristics, time delays were found in the range of 0 to 6 ms for stimulus intensity, modulation depth, and carrier frequency, which were maximal at low frequencies, low intensities, or maximal modulation depth.
Borderline Personality Disorder
Authors: Jin Jill
Published: February 2023

This JAMA Patient Page describes borderline personality disorder, its signs and symptoms, possible causes, diagnosis, and treatment options.
A Triboelectric Nanocomposite for Sterile Sensing, Energy Harvesting, and Haptic Diagnostics in Interventional Procedures from Surgical Gloves
Authors: Salvadores Fernandez Carmen , Jaufuraully Shireen , Bagchi Biswajoy , Chen Wenqing , Datta Priyankan , Gupta Priya , David Anna L. , Siassakos Dimitrios , Desjardins Adrien , Tiwari Manish K.
Published: February 2023

Advanced interfacial engineering has the potential to enable the successful realization of three features that are particularly important for a variety of healthcare applications: wettability control, antimicrobial activity to reduce infection risks, and sensing of physiological parameters. Here, a sprayable multifunctional triboelectric coating is exploited as a nontoxic, ultrathin tactile sensor that can be integrated directly on the fingertips of surgical gloves. The coating is based on a polymer blend mixed with zinc oxide (ZnO) nanoparticles, which enables antifouling and antibacterial properties. Additionally, the nanocomposite is superhydrophobic (self‐cleaning) and is not cytotoxic. The coating is also triboelectric and can be applied directly onto surgical gloves with printed electrodes. The sensorized gloves so obtained enable mechanical energy harvesting, force sensing, and detection of materials stiffness changes directly from fingertip, which may complement proprioceptive feedback for clinicians. Just as importantly, the sensors also work with a second glove on top offering better reassurance regarding sterility in interventional procedures. As a case study of clinical use for stiffness detection, the sensors demonstrate successful detection of pig anal sphincter injury ex vivo. This may lead to improving the accuracy of diagnosing obstetric anal sphincter injury, resulting in prompt repair, fewer complications, and improved quality of life.
A Polypyrrole‐Polycarbonate Polyurethane Elastomer Alleviates Cardiac Arrhythmias via Improving Bio‐Conductivity
Authors: Fadle Aziz Monir Riasad , Wlodarek Lukasz , Alibhai Faisal , Wu Jun , Li Shuhong , Sun Yu , Santerre J. Paul , Li Ren‐Ke
Published: February 2023

Myocardial fibrosis, resulting from myocardial infarction (MI), significantly alters cardiac electrophysiological properties. As fibrotic scar tissue forms, its resistance to incoming action potentials increases, leading to cardiac arrhythmia, and eventually sudden cardiac death or heart failure. Biomaterials are gaining increasing attention as an approach for addressing post‐MI arrhythmias. The current study investigates the hypothesis that a bio‐conductive epicardial patch can electrically synchronize isolated cardiomyocytes in vitro and rescue arrhythmic hearts in vivo. A new conceived biocompatible, conductive, and elastic polyurethane composite bio‐membrane, referred to as polypyrrole‐polycarbonate polyurethane (PPy‐PCNU), is developed, in which solid‐state conductive PPy nanoparticles are distributed throughout an electrospun aliphatic PCNU nanofiber patch in a controlled manner. Compared to PCNU alone, the resulting biocompatible patch demonstrates up to six times less impedance, with no conductivity loss over time, as well as being able to influence cellular alignment. Furthermore, PPy‐PCNU promotes synchronous contraction of isolated neonatal rat cardiomyocytes and alleviates atrial fibrillation in rat hearts upon epicardial implantation. Taken together, epicardially‐implanted PPy‐PCNU could potentially serve as a novel alternative approach for the treatment of cardiac arrhythmias.
Piezoelectric Bioactive Glasses Composite Promotes Angiogenesis by the Synergistic Effect of Wireless Electrical Stimulation and Active Ions
Authors: Li Changhao , Zhang Siyu , Yao Yichen , Wang Yanlan , Xiao Cairong , Yang Bo , Huang Jingyan , Li Weichang , Ning Chengyun , Zhai Jinxia , Yu Peng , Wang Yan
Published: February 2023

Insufficient angiogenesis frequently occurs after the implantation of orthopedic materials, which greatly increases the risk of bone defect reconstruction failure. Therefore, the development of bone implant with improved angiogenic properties is of great importance. Mimicking the extracellular matrix clues provides a more direct and effective strategy to modulate angiogenesis. Herein, inspired by the bioelectrical characteristics of the bone microenvironment, a piezoelectric bioactive glasses composite (P‐KNN/BG) based on the incorporation of polarized potassium sodium niobate is constructed, which could effectively promote angiogenesis. It is found that P‐KNN/BG has exceptional wireless electrical stimulation performance and sustained active ions release. In vitro cell experiments reveal that P‐KNN/BG enhances endothelial cell adhesion, migration, and differentiation via activating the eNOS/NO signaling pathway, which might be contributed to cell membrane hyperpolarization induced by wireless electrical stimulation increase the influx of active ions into the cells. In vivo chick chorioallantoic membrane experiment demonstrates that P‐KNN/BG shows excellent pro‐angiogenic capacity and biocompatibility. This work broadens the current understanding of bioactive materials with bionic electrical properties, which brings new insights into the clinical treatment of bone defect repair.
Manipulation of Arbitrary Polarizations and Phases Based on Metasurfaces
Authors: Liu Wei , Zhang Lei , Ke Jun Chen , Liang Jing Cheng , Dai Jun Yan , Cheng Qiang , Cui Tie Jun
Published: February 2023

Polarization and phase are two essential properties of electromagnetic (EM) waves. A transmissive metasurface is proposed that can simultaneously manipulate the polarization and phase of the EM waves. The design has a powerful capability of rotating the polarization to any desired azimuth direction for a linearly polarized (LP) wave and achieving the cross‐polarization conversion for a circularly polarized (CP) wave. Meanwhile, the transmission phase of the cross‐polarization can be dynamically controlled for the CP wave. The proposed metasurface is composed of two types of substrate‐integrated waveguides (SIW) in a cross arrangement, which has an insertion loss of less than 0.3 dB from 9.7 to 10.3 GHz. Some samples are fabricated and measurements are performed, which are in satisfactory agreement with the theoretical and simulated results, indicating the feasibility of the proposed method. It is believed that the proposed design has many potential applications in the fields of imaging, communication, and radar systems.
Advancements in the Preparation of 4H‐Chromenes: An Overview
Authors: Wen Zhong , Yang Kai‐Cheng , Deng Jun‐Feng , Chen Long
Published: February 2023

Functionalized 4H‐chromenes represent one class of the most important structural scaffolds in both synthetic and medicinal chemistry. They often appear in an arrange of biological natural products, pharmaceutical agents and drug candidates. The significance has stimulated the development of efficient methodologies for the synthesis of such compounds. In this review, a comprehensive discussion on different synthetic approaches to 4H‐chromenes has been presented with an emphasis on reaction features and mechanisms. Three main categories are outlined: 1) nucleophilic addition to 2H‐chromene derivatives, 2) 4H‐chromene ring formation involved cycloaddition or cyclization reactions, and 3) miscellaneous reactions.

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A Pathway into Metaverse: Gesture Recognition Enabled by Wearable Resistive Sensors
Authors: Duan Shengshun , Zhao Fangzhi , Yang Huiying , Hong Jianlong , Shi Qiongfeng , Lei Wei , Wu Jun
Published: February 2023

Hand gesture recognition is of great importance for human–Metaverse interaction. The human hand is relatively smaller, with very complex articulations than the entire human body. Therefore, precise hand gesture recognition, especially in complicated environments, is still a great challenge. Wearable resistive sensors that could directly characterize joint movements are one of the most promising technologies for hand gesture recognition due to their easy integration, low cost, and simple signal acquisition. Here, we summarize common categories of wearable resistive sensors for hand gesture recognition and review the recent advances. Besides, common strategies for improving waterproofness (molecular design, material modification, and interfacial encapsulation) are also outlined. Perspectives on the advantages of combining machine vision and resistive sensors for accurate hand gesture recognition and dynamic hand gesture tracking are then provided. We hope this review could inspire future research in wearable technologies for human–Metaverse systems.
Synthesis of Erythrocyte Nanodiscs for Bacterial Toxin Neutralization
Authors: Sun Lei , Wang Dan , Noh Ilkoo , Fang Ronnie H. , Gao Weiwei , Zhang Liangfang
Published: February 2023

Nanodiscs are a compelling nanomedicine platform due to their ultrasmall size and distinct disc shape. Current nanodisc formulations are made primarily with synthetic lipid bilayers and proteins. Here, we report a cellular nanodisc made with human red blood cell (RBC) membrane (denoted “RBC‐ND”) and show its effective neutralization against bacterial toxins. In vitro, RBC‐ND neutralizes the hemolytic activity and cytotoxicity caused by purified α‐toxin or complex whole secreted proteins (wSP) from methicillin‐resistant Staphylococcus aureus bacteria. In vivo, RBC‐ND confers significant survival benefits for mice intoxicated with α‐toxin or wSP in both therapeutic and prevention regimens. Moreover, RBC‐ND shows good biocompatibility and biosafety in vivo. Overall, RBC‐ND distinguishes itself by inheriting the biological functions of the source cell membrane for bioactivity. The design strategy of RBC‐ND can be generalized to other types of cell membranes for broad applications.
Giving Gold Wings: Ultrabright and Fragmentation Free Mass Spectrometry Reporters for Barcoding, Bioconjugation Monitoring, and Data Storage
Authors: Dominique Nathaniel L. , Jensen Isabel M. , Kaur Gurkiran , Kotseos Chandler Q. , Boggess William C. , Jenkins David M. , Camden Jon P.
Published: February 2023

The widespread application of laser desorption/ionization mass spectrometry (LDI‐MS) highlights the need for a bright and multiplexable labeling platform. While ligand‐capped Au nanoparticles (AuNPs) have emerged as a promising LDI‐MS contrast agent, the predominant thiol ligands suffer from low ion yields and extensive fragmentation. In this work, we develop a N‐heterocyclic carbene (NHC) ligand platform that enhances AuNP LDI‐MS performance. NHC scaffolds are tuned to generate barcoded AuNPs which, when benchmarked against thiol‐AuNPs, are bright mass tags and form unfragmented ions in high yield. To illustrate the transformative potential of NHC ligands, the mass tags were employed in three orthogonal applications: monitoring a bioconjugation reaction, performing multiplexed imaging, and storing and reading encoded information. These results demonstrate that NHC‐nanoparticle systems are an ideal platform for LDI‐MS and greatly broaden the scope of nanoparticle contrast agents.
Effect of CeO2 NPs on stability of regenerated silk fibroin against UV‐aging
Authors: Jiang Lei , Wu Chengkun , Yao Lu , Dong Qiuxia , Wu Guohua
Published: February 2023

Regenerated silk fibroin (RSF) fibers have great application prospects in medicine, textiles, optoelectronics, and other fields. However, under the synergistic action of ultraviolet, oxygen, and water, RSF will inevitably become brittle, which will greatly shorten the service life of RSF. Therefore, it is urgent to find some methods to protect RSF from aging damage. Cerium dioxide nanoparticles have a strong ultraviolet absorption and antioxidant capacity and have been used as an anti‐aging component for other biomaterials. Thus, the RSF/CeO2 NPs hybrid fibers were successfully prepared, and a series of artificial aging tests were carried out. Mechanical property is an important index to measure the aging degree. After aging, compared with RSF, the stress of RSF/CeO2 NPs hybrid fibers was increased by 130.47 ± 4.78 MPa, and the strain of RSF/CeO2 NPs hybrid fibers was increased by 69.89% ± 1.37%. The results of Fourier transform infrared spectroscopy, UV–Vis, sodium dodecyl sulfate polyacrylamide gel electrophoresis discussed the protective mechanism of CeO2 NPs, which prevent the transition from β‐sheet to α‐helix/random coil and the disorder of structure. Furthermore, RSF/CeO2 NPs hybrid fibers have an excellent antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria; the antioxidant activity of RSF/CeO2 NPs hybrid fibers is gradually enhanced in the presence of UV‐light.
MED26‐containing Mediator may orchestrate multiple transcription processes through organization of nuclear bodies
Authors: Suzuki Hidefumi , Furugori Kazuki , Abe Ryota , Ogawa Shintaro , Ito Sayaka , Akiyama Tomohiko , Horiuchi Keiko , Takahashi Hidehisa
Published: February 2023

Mediator is a coregulatory complex that plays essential roles in multiple processes of transcription regulation. One of the human Mediator subunits, MED26, has a role in recruitment of the super elongation complex (SEC) to polyadenylated genes and little elongation complex (LEC) to non‐polyadenylated genes, including small nuclear RNAs (snRNAs) and replication‐dependent histone (RDH) genes. MED26‐containing Mediator plays a role in 3′ Pol II pausing at the proximal region of transcript end sites in RDH genes through recruitment of Cajal bodies (CBs) to histone locus bodies (HLBs). This finding suggests that Mediator is involved in the association of CBs with HLBs to facilitate 3′ Pol II pausing and subsequent 3′‐end processing by supplying 3′‐end processing factors from CBs. Thus, we argue the possibility that Mediator is involved in the organization of nuclear bodies to orchestrate multiple processes of gene transcription.