bluuebunny/crossref_metadata_2025 huggingface dataset:
A subspace limited memory quasi-Newton algorithm for large-scale nonlinear bound constrained optimization
Authors: Ni Q. , Yuan Y.
Published: July 2002

In this paper we propose a subspace limited memory quasi-Newton method for solving large-scale optimization with simple bounds on the variables. The limited memory quasi-Newton method is used to update the variables with indices outside of the active set, while the projected gradient method is used to update the active variables. The search direction consists of three parts: a subspace quasi-Newton direction, and two subspace gradient and modified gradient directions. Our algorithm can be applied to large-scale problems as there is no need to solve any subproblems. The global convergence of the method is proved and some numerical results are also given.
A Polymer Model for Large-scale Chromatin Organization in Lower Eukaryotes
Authors: Ostashevsky Joseph
Published: July 2002

A quantitative model of large-scale chromatin organization was applied to nuclei of fission yeast Schizosaccharomyces pombe (meiotic prophase and G2 phase), budding yeastSaccharomyces cerevisiae (young and senescent cells),Drosophila (embryonic cycles 10 and 14, and polytene tissues) and Caenorhabditis elegans (G1 phase). The model is based on the coil-like behavior of chromosomal fibers and the tight packing of discrete chromatin domains in a nucleus. Intrachromosomal domains are formed by chromatin anchoring to nuclear structures (e.g., the nuclear envelope). The observed sizes for confinement of chromatin diffusional motion are similar to the estimated sizes of corresponding domains. The model correctly predicts chromosome configurations (linear, Rabl, loop) and chromosome associations (homologous pairing, centromere and telomere clusters) on the basis of the geometrical constraints imposed by nuclear size and shape. Agreement between the model predictions and literature observations supports the notion that the average linear density of the 30-nm chromatin fiber is ∼4 nucleosomes per 10 nm contour length.
Mammalian Ku86 protein prevents telomeric fusions independently of the length of TTAGGG repeats and the G‐strand overhang
Authors: Samper Enrique , Goytisolo Fermín A , Slijepcevic Predrag , van Buul Paul P W , Blasco María A
Published: July 2002

Ku86 together with Ku70, DNA‐PKcs, XRCC4 and DNA ligase IV forms a complex involved in repairing DNA double‐strand breaks (DSB) in mammals. Yeast Ku has an essential role at the telomere; in particular, Ku deficiency leads to telomere shortening, loss of telomere clustering, loss of telomeric silencing and deregulation of the telomeric G‐overhang. In mammals, Ku proteins associate to telomeric repeats; however, the possible role of Ku in regulating telomere length has not yet been addressed. We have measured telomere length in different cell types from wild‐type and Ku86‐deficient mice. In contrast to yeast, Ku86 deficiency does not result in telomere shortening or deregulation of the G‐strand overhang. Interestingly, Ku86−/− cells show telomeric fusions with long telomeres (>81 kb) at the fusion point. These results indicate that mammalian Ku86 plays a fundamental role at the telomere by preventing telomeric fusions independently of the length of TTAGGG repeats and the integrity of the G‐strand overhang.
The epidemiology of pneumococcal infection in children in the developing world
Authors: Greenwood Brian
Published: July 2002

Pneumonia causes about three million deaths a year in young children, nearly all of which are in developing countries.
Streptococcus pneumoniae
(the pneumococcus) is the most important bacterial cause of pneumonia in young children and so is likely to be responsible for a high proportion of these deaths. The pneumococcus is also responsible for a substantial proportion of the 100 000–500 000 deaths that occur from meningitis in children each year. The incidence of invasive pneumococcal disease in children in the developing world is several times higher than in industrialized countries. This discrepancy may, in part, be due to socio–economic differences but genetic factors may also play a role. Children with sickle cell disease have a substantially increased risk of invasive pneumococcal infection and a search is being made for other possible genetic risk factors. Infection with human immunodeficiency virus (HIV) also predisposes to invasive pneumococcal disease and so the incidence of this disease in young children is expected to rise as increasing numbers of African and Asian children are born with a perinatally acquired HIV infection. Until recently, pneumococcal infections could be treated effectively with penicillin, a cheap and safe antibiotic. However, pneumococci that are resistant to penicillin are becoming prevalent in many countries, necessitating a change to more costly antibiotics which may be beyond the reach of the health services of poor, developing counties. The spread of antibiotic resistance has provided an added stimulus to the development of vaccines that might be able to prevent pneumococcal disease in infants. Recently developed polysaccharide–protein conjugate vaccines show promise and are now undergoing field trials. How deployment of these vaccines will influence the balance between invasive pneumococcal infections and asymptomatic nasopharyngeal carriage of pneumococci is uncertain.
Bilateral receptive field neurons and callosal connections in the somatosensory cortex
Authors: Iwamura Yoshiaki
Published: July 2002

Earlier studies recording single neuronal activity with bilateral receptive fields in the primary somatosensory cortex of monkeys and cats agreed that the bilateral receptive fields were related exclusively to the body midline and that the ipsilateral information reaches the cortex via callosal connections since they are dense in the cortical region representing the midline structures of the body while practically absent in the regions representing the distal extremities. We recently found a substantial number of neurons with bilateral receptive fields on hand digits, shoulders–arms or legs–feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake Japanese monkeys (Macaca fuscata). I review these results, discuss the functional implications of this bilateral representation in the postcentral somatosensory cortex from a behavioural standpoint and give a new interpretation to the midline fusion theory.
Performance comparison of full‐field digital mammography to screen–film mammography in clinical practice
Authors: Berns Eric A. , Hendrick R. Edward , Cutter Gary. R.
Published: July 2002

Results of acceptance testing 18 full‐field digital mammography systems for clinical use and of conducting annual physics surveys of 38 screen–film mammography systems were compared in terms of exposure times, mean glandular breast doses, and image quality. These evaluations were made using the same test tools on all systems, with emphasis on assessing automatic exposure control performance and image quality on both digital and screen–film systems using clinical techniques. Survey results indicated that digital mammography systems performed similarly to screen–film systems in terms of exposure times and mean glandular doses for thin to intermediate breasts, but that digital mammography systems selected shorter exposure times and lower mean glandular doses for thicker breasts. For all breast thicknesses, digital mammography systems yielded mean contrast–detail scores higher than those for screen–film systems. For all breast thicknesses, the 18 digital mammography systems demonstrated less variance in terms of exposure times, mean glandular doses, and contrast–detail scores than did the 38 screen–film systems tested. These results indicate that the clinical use of digital mammography may generally improve image quality for equal or lower breast doses, while providing tighter control on exposures and image quality than screen–film mammography.
Analyzing linear and angular momentum conservation in digital videos of puck collisions
Authors: Williamson J. Charles , Torres-Isea Ramon O. , Kletzing Craig A.
Published: July 2002

We describe a new undergraduate mechanics laboratory experiment that illustrates principles of linear and angular momentum conservation. Students observe that angular momentum is conserved in systems where the initial conditions involve only translational motion, and yet the final conditions include rotational motion. To do this, students make a digital video of a two-object collision on an air table. One object has an asymmetric mass distribution and gains rotational kinetic energy as a result of the collision. Using their digital video, students create a stroboscopic image of the two objects’ trajectories and show that both linear and angular momentum are conserved to within a few percent, the limit of experimental uncertainty. Students also show that angular momentum conservation is independent of the choice of origin, that the center of mass of the asymmetric object follows a linear trajectory, and that the center of mass of the whole system follows a linear trajectory.
Deformation quantization in the teaching of quantum mechanics
Authors: Hirshfeld Allen C. , Henselder Peter
Published: July 2002

We discuss the deformation quantization approach for the teaching of quantum mechanics. This approach has certain conceptual advantages that make its consideration worthwhile. In particular, it sheds new light on the relation between classical and quantum mechanics. We demonstrate how it can be used to solve specific problems and clarify its relation to conventional quantization and path integral techniques. We also discuss its recent applications in relativistic quantum field theory.
B and H, the intensity vectors of magnetism: A new approach to resolving a century-old controversy
Authors: Roche John J.
Published: July 2002

The B and H controversy, which has persisted for more than a century, is at bottom a debate over the structure of the macroscopic magnetic field, both in a vacuum and in a magnetized body. It is also a controversy over units and notation. It is paralleled by the problem of D and E in dielectrics. Its origins are traced to a dual magnetic field concept of William Thomson, to an altogether different dual field concept of Faraday, and to Maxwell’s attempt to bind the concepts of Thomson and Faraday together. The author argues that severe ambiguities were inadvertently introduced to this subject during its foundational period and subsequently, and that many of these still remain embedded in the present-day interpretation of the subject. The article attempts to clear up a long history of misunderstanding by dealing with each difficulty in the same sequence in which it was introduced to electromagnetism.
Nonlinear interactions that could explain distortion product interference response areas
Authors: Fahey P. F. , Stagner B. B. , Lonsbury-Martin B. L. , Martin G. K.
Published: July 2002

Suppression and/or enhancement of third- and fifth-order distortion products by a third tone that can have a frequency more than an octave above and a level more than 40 dB below the primary tones have recently been measured by Martin et al. [Hear. Res. 136, 105–123 (1999)]. Contours of iso-suppression and iso-enhancement that are plotted as a function of third-tone frequency and level are called interference response areas. After ruling out order aliasing, two possible mechanisms for this effect have been developed, a harmonic mechanism and a catalyst mechanism. The harmonic mechanism produces distortion products by mixing a harmonic of one of the primary tones with the other primary tone. The catalyst mechanism produces distortion products by mixing one or more intermediate distortion products that are produced by the third tone with one or more of the input tones. The harmonic mechanism does not need a third tone and the catalyst mechanism does. Because the basilar membrane frequency response is predicted to affect each of these mechanisms differently, it is concluded that the catalyst mechanism will be dominant in the high-frequency regions of the cochlea and the harmonic mechanism will have significant strength in the low-frequency regions of the cochlea. The mechanisms are dependent on the existence of both even- and odd-order distortion, and significant even- and odd-order distortion have been measured in the experimental animals. Furthermore, the nonlinear part of the cochlear mechanical response must be well into saturation when input tones are 50 or more dB SPL.
The mode-coupling Liouville–Green approximation for a two-dimensional cochlear model
Authors: Watts Lloyd
Published: July 2002

The Liouville–Green [or Wentzel–Kramers–Brillouin (WKB)] approximation for the two-dimensional cochlear mechanics problem disagrees with the finite-difference solution in the region after the response peak. This disagreement has left doubts about the validity of the Liouville–Green approximation, and has never been satisfactorily explained. In this paper, it is shown that the Liouville–Green approximation fails to satisfy Laplace’s equation. A new solution is proposed, called the mode-coupling Liouville–Green approximation, in which energy is coupled into a second wave mode, so as to obey Laplace’s equation. The new approximation gives excellent quantitative agreement with the finite-difference solution. Furthermore, it may provide an explanation for a second vibration mode observed in biological cochleas. Also proposed is a high-order formulation of the stapes displacement term, which is necessary to obtain good agreement between the Liouville–Green approximation and finite-difference solutions at low frequencies.
On the upper cutoff frequency of the auditory critical-band envelope detectors in the context of speech perception
Authors: Ghitza Oded
Published: July 2002

Studies in neurophysiology and in psychophysics provide evidence for the existence of temporal integration mechanisms in the auditory system. These auditory mechanisms may be viewed as “detectors,” parametrized by their cutoff frequencies. There is an interest in quantifying those cutoff frequencies by direct psychophysical measurement, in particular for tasks that are related to speech perception. In this study, the inherent difficulties in synthesizing speech signals with prescribed temporal envelope bandwidth at the output of the listener’s cochlea have been identified. In order to circumvent these difficulties, a dichotic synthesis technique is suggested with interleaving critical-band envelopes. This technique is capable of producing signals which generate cochlear temporal envelopes with prescribed bandwidth. Moreover, for unsmoothed envelopes, the synthetic signal is perceptually indistinguishable from the original. With this technique established, psychophysical experiments have been conducted to quantify the upper cutoff frequency of the auditory critical-band envelope detectors at threshold, using high-quality, wideband speech signals (bandwidth of 7 kHz) as test stimuli. These experiments show that in order to preserve speech quality (i.e., for inaudible distortions), the minimum bandwidth of the envelope information for a given auditory channel is considerably smaller than a critical-band bandwidth (roughly one-half of one critical band). Difficulties encountered in using the dichotic synthesis technique to measure the cutoff frequencies relevant to intelligibility of speech signals with fair quality levels (e.g., above MOS level 3) are also discussed.
Concurrent vowel identification. III. A neural model of harmonic interference cancellation
Authors: Cheveigné Alain de
Published: July 2002

This paper presents a “neural cancellation filter” capable of segregating weak targets from competing harmonic backgrounds, and a model of concurrent vowel segregation based upon it. The elementary cancellation filter comprises a delay line and an inhibitory synapse. Filters within each peripheral channel are tuned to the period of the competing sound to suppress its correlates within the neural discharge pattern. In combination with a pattern matching model based on autocorrelation functions summed over channels, the cancellation filter forms a model of concurrent vowel identification. The model predicts the number of vowels reported for each stimulus (when subjects are allowed to report one or two) and identification rates. It belongs to the class of “harmonic cancellation” models that are supported by experimental evidence that vowel identification is better when competing sounds are harmonic than inharmonic. Two alternative schemes using the same filter are also considered. One derives a “place” representation from the magnitude of the filter output. The other uses the ratio of filter input/output to select channels.
Comparison between prediction and measurement of viscoelastic moduli in composite materials versus temperature using ultrasonic immersion technique with oil
Authors: Baudouin Sandrine , Hosten Bernard
Published: July 2002

An oil immersion ultrasonic method used for measuring elastic and viscoelastic properties of materials versus temperature is presented. From velocity and amplitude measurements, the complex viscoelastic tensor can be entirely determined from room temperature to temperatures near the glass transition temperature of the material. This tensor permits the computation of velocities and attenuations of heterogeneous or homogeneous modes in any direction of wave propagation. A micromechanics model is used to compare experimental results with theoretical ones and to analyze anisotropic elastic and viscoelastic behavior of composite materials.
Developmental weighting shifts for noise components of fricative-vowel syllables
Authors: Nittrouer Susan , Miller Marnie E.
Published: July 2002

Previous studies have convincingly shown that the weight assigned to vocalic formant transitions in decisions of fricative identity for fricative-vowel syllables decreases with development. Although these same studies suggested a developmental increase in the weight assigned to the noise spectrum, the role of the aperiodic-noise portions of the signals in these fricative decisions have not been as well-studied. The purpose of these experiments was to examine more closely developmental shifts in the weight assigned to the aperiodic-noise components of the signals in decisions of syllable-initial fricative identity. Two experiments used noises varying along continua from a clear /s/ percept to a clear /∫/ percept. In experiment 1, these noises were created by combining /s/ and /∫/ noises produced by a human vocal tract at different amplitude ratios, a process that resulted in stimuli differing primarily in the amplitude of a relatively low-frequency (roughly 2.2-kHz) peak. In experiment 2, noises that varied only in the amplitude of a similar low-frequency peak were created with a software synthesizer. Both experiments used synthetic /ɑ/ and /u/ portions, and efforts were made to minimize possible contributions of vocalic formant transitions to fricative labeling. Children and adults labeled the resulting stimuli as /s/ vowel or /∫/ vowel. Combined results of the two experiments showed that children’s responses were less influenced than those of adults by the amplitude of the low-frequency peak of fricative noises.
Vibrato extent and intonation in professional Western lyric singing
Authors: Prame Eric
Published: July 2002

Two important aspects of singers’ F0 control have been investigated: vibrato extent and intonation. From ten commercially available compact disc recordings of F. Schubert’s Ave Maria, 25 tones were selected for analysis. Fundamental frequency was determined by spectrograph analysis of a high overtone at each turning point of the vibrato undulations. It was found that the mean vibrato extent for individual tones ranged between ±34 and ±123 cent and that the mean across tones and singers amounted to ±71 cent. Informal measurements on Verdi opera arias showed much higher figures. With regard to intonation substantial departures from equally tempered tuning were found for individual tones. A tone’s vibrato extent was found to have a negative correlation with tone duration and a positive correlation with intonation.
Using joint geometry to determine the motion of the cricoarytenoid joint
Authors: Selbie W. Scott , Zhang Lei , Levine William S. , Ludlow Christy L.
Published: July 2002

Facet surfaces of the cricoarytenoid joints from two cadaver larynges were digitized. The data were used to compute the optimal axis of rotation for each of the joints in the sense that the computed axis minimized the variance of the joint gap over the full range of joint motion. The optimal axis corresponded to a rocking motion of the arytenoid on the corresponding cricoid. This motion was consistent with experimental data from digitized recordings of vocal fold movement. Using the rigid laryngoscopic view, a similarity in vocal process movement, over the range in motion, between the rocking axis and the vertical axis described in the literature was found, resolving the controversy between two conflicting views of motion of the vocal processes.
Low-level steady-state auditory evoked potentials: Effects of rate and sedation on detectability
Authors: Dobie Robert A. , Wilson Michael J.
Published: July 2002

Steady-state auditory evoked potentials (SSAEPs) in alert adults are most detectable at stimulus or modulation rates of about 40 Hz. Sedation reduces the detectability of 40-Hz SSAEPs and increases it for higher rate SSAEPs. This study examined whether rates higher than 40 Hz would be preferable for detecting responses to low-intensity tones in sedated adults. Fourteen normal adults listened to 640-Hz tones at modulation rates (and toneburst rates) of 20–160 Hz, in 10-Hz steps, at levels of 38 and 58 dB peak equivalent sound-pressure level (peSPL) (20 and 40 dB normal hearing level (nHL) for amplitude-modulated (AM) tones), both alert and sedated (1–2 g chloral hydrate). Sedation reduced both signal (SSAEP) power and noise power at all rates, but noise power reduction was greater for higher rates. Detectability in the alert condition was always greatest at 40 Hz. Under sedation, a second detectability peak was present at 90 Hz for 58-dB peSPL tones, approximately equal to that seen at 40 Hz. At 38 dB peSPL (sedated), peak detectability moved from 40 to 50 Hz. These results suggest that presentation/modulation rates around 40 Hz may be optimal for SSAEP detectability at low levels in adults, whether alert or sedated.
STV: Silencing goods traffic. Part 2: Demonstrating practical low noise solutions
Authors: Lub J.
Published: July 2002

The Dutch national project, Quiet Rail Traffic (Stiller Treinverkeer STV), aims at an overall A-weighted noise reduction of at least 10 dB for day-to-day goods traffic, with a maximum achievable reduction of 16 dB. The project has as goals the development of validated design and analysis methods, and the demonstration thereof by means of the construction and testing of two prototype quiet goods wagons and a prototype quiet track construction. Validation tests will be performed in November 1998. Static and pass-by noise and vibration tests are conducted with two prototype container carrying wagons, loaded with containers and a reference vehicle. The goods wagons are equipped with laser-cladded wheels, composite brake blocks, drum brakes, magnetic brakes, and wheel skirts. They are operated on a continuously laid slab track construction with embedded rail. The rail type is of a newly designed type, optimized for noise reduction and application in track designs with continuous rail support. Minibarriers and sound absorption material are applied to the track. A telemetry system is used for measuring wheel noise. The improvements achieved by the total prototype wagon/track combination and components are compared to the predicted noise reduction and data collected in the reference phase of the project.
Amplitude-modulation detection at low- and high-audio frequencies
Authors: Eddins David A.
Published: July 2002

Estimates of temporal acuity under comparable conditions at low- and high-audio frequencies are rare. The present study used the amplitude-modulation detection paradigm to estimate temporal acuity over a range of audio frequencies from 800 to 12 800 Hz. Amplitude-modulation detection was measured as a function of modulation frequency for bandlimited noise carriers, and the resulting temporal modulation-transfer functions were used to characterize temporal acuity. The most important result from the two experiments reported is that systematic manipulations of carrier upper-cutoff frequency produced estimates of temporal acuity that did not vary from 800 to 12 800 Hz. When the modulated noise bands were filtered after modulation to control for potential spectral cues, the low-pass cutoff of the modulation-transfer function varied with the carrier bandwidth. However, when the standard stimulus was a quasifrequency-modulated (QFM) noise and the signal was an unfiltered, amplitude-modulated noise, the low-pass cutoff of the modulation-transfer function was independent of carrier bandwidth. These results are consistent with a growing body of evidence demonstrating that auditory temporal acuity is constant throughout most of the audible frequency range.
Scattering properties of encapsulated gas bubbles at high ultrasound pressures
Authors: Frinking Peter J. A. , de Jong Nico , Céspedes E. Ignacio
Published: July 2002

Encapsulated types of contrast agents possess a specific acoustical signature. When the applied acoustic pressure exceeds a specific threshold, the scattering level increases abruptly for a short time. A “dualistic” character of the encapsulated gas bubbles explains this signature, observed for Quantison™ (air bubbles encapsulated by a shell of human albumin). For acoustic pressures below a threshold, the bubbles act as encapsulated gas bubbles and are stable linear or nonlinear scatterers, depending on the applied acoustic pressure. For acoustic pressures above the threshold, the bubbles rupture and release the contained gas, subsequently acting as free-gas bubbles. The effect is transient and lasts until the released free-gas bubbles are dissolved in the surrounding liquid. This explanation was investigated experimentally and evaluated by theoretical models. A 15–20-dB increase in scattering, the appearance of higher harmonics, and a finite duration of the effect could be measured and agreed with corresponding theory. Therefore, ultrasound in combination with this dualistic character suggests that encapsulated gas bubbles can be construed as a robust vehicle for localized delivery of free-gas bubbles, the ultimate ultrasound contrast agent.
Longitudinal endolymph movements and endocochlear potential changes induced by stimulation at infrasonic frequencies
Authors: Salt Alec N. , DeMott John E.
Published: July 2002

The inner ear is continually exposed to pressure fluctuations in the infrasonic frequency range (<20 Hz) from external and internal body sources. The cochlea is generally regarded to be insensitive to such stimulation. The effects of stimulation at infrasonic frequencies (0.1 to 10 Hz) on endocochlear potential (EP) and endolymph movements in the guinea pig cochlea were studied. Stimuli were applied directly to the perilymph of scala tympani or scala vestibuli of the cochlea via a fluid-filled pipette. Stimuli, especially those near 1 Hz, elicited large EP changes which under some conditions exceeded 20 mV in amplitude and were equivalent to a cochlear microphonic (CM) response. Accompanying the electrical responses was a cyclical, longitudinal displacement of the endolymph. The amplitude and phase of the CM varied according to which perilymphatic scala the stimuli were applied to and whether a perforation was made in the opposing perilymphatic scala. Spontaneously occurring middle ear muscle contractions were also found to induce EP deflections and longitudinal endolymph movements comparable to those generated by perilymphatic injections. These findings suggest that cochlear fluid movements induced by pressure fluctuations at infrasonic frequencies could play a role in fluid homeostasis in the normal state and in fluid disturbances in pathological states.
Loudness recalibration as a function of level
Authors: Mapes-Riordan Dan , Yost William A.
Published: July 2002

Recent research on loudness has focused on contextual effects on loudness, both assimilation and recalibration. The current experiments examined loudness recalibration [Marks, J. Exp. Psychol. 20, 382–396 (1994)]. In the first experiment, an adaptive tracking procedure was used to measure loudness recalibration as a function of standard- and recalibration-tone level. The standard-tone frequencies were 500 and 2500 Hz and the levels were 80-, 70-, 60-, and 40-dB SPL, and threshold. Seventeen dB of loudness recalibration was obtained (combined over both frequencies) in the 60-dB SPL condition. This amount of loudness recalibration, while substantial, is still less than that obtained by Marks (22 dB), using the method of paired comparisons. The second experiment sought to duplicate Marks’ earlier experiment [Marks, J. Exp. Psychol. 20, 382–396 (1994), experiment 2]. The results of this experiment (21 dB) were almost identical to those obtained by Marks. The results of experiment 1 indicate that loudness recalibration is maximum when the recalibration tone is moderately louder than the subsequent standard tones. Relatively little loudness recalibration is exhibited when the standard-tone level equals the recalibration-tone level. In addition, there is no loudness recalibration at threshold. The tracking procedure also identified that the onset of loudness recalibration is very rapid. The difference between the maximum loudness recalibration obtained at each frequency (11 dB at 500 Hz, 6 dB at 2500 Hz) suggests that loudness recalibration is dependent upon the frequency of the standard tone.
Rheological Factors Influencing Platelet Interaction with Vessel Surfaces
Authors: Turitto Vincent T. , Weiss Harvey J. , Baumgartner Hans R.
Published: July 2002

An in vitro perfusion system was used to investigate platelet interaction with subendothelium from rabbit aorta exposed to blood under controlled flow conditions. A morphological technique was used to measure platelet adhesion and thrombus formation. Classical mass transport theory modified to account for the dependence of platelet diffusivity on wall shear rate was used to analyze the results. Platelet adhesion increased with wall shear rate (10–650 sec−1), red cell concentration (10–70%), and platelet concentration (50–300 nl−1) and decreased with axial distance (0–20 mm) from the leading edge. Under these flow conditions platelet adhesion rate was determined predominantly by diffusional transport of platelets to the vessel surface. As shear rate increased to 10,000 sec−1, a transition from diffusion to a more kinetic rate limiting adhesion was observed. Few thrombi were observed at low values of platelet concentration (<150/ml), red cell concentration (<25%), or wall shear rate (<200 sec−1). The formation of thrombi increased continuously with increasing wall shear rate to 10,000 sec−1 even in the region where values of platelet adhesion became relatively independent of shear rate. Thrombus formation was enhanced by an increase in red cell or platelet concentration and was significantly greater on the upstream portions of vessel segments.
Segmental relaxation in miscible polymer blends
Authors: Roland C. M. , Ngai K. L.
Published: July 2002

Usually the shape of the glass transition dispersion in the mechanical or dielectric spectra of pure polymers is skewed toward higher frequencies. In miscible polymer blends not only is this peak broader than in pure polymers, the broadening is often asymmetric towards lower frequencies. Concentration fluctuations are the obvious source of the broadening; however, a simple distribution of relaxation times, corresponding to a distribution in local compositions, would not account for the reversal in the asymmetry of the dispersion. Miscible blends are also thermorheological complex, with the temperature dependence of segmental relaxation exhibiting idiosyncratic composition dependencies. A model to describe the composition dependence and shape of the relaxation spectra of miscible polymer blends in the glass transition zone is described. The fluctuations in local composition inherent to a miscible blend give rise to a distribution in both the relaxation time and degree of cooperativity of segmental relaxation. Generally, the intermolecular cooperativity will be amplified by a high relative abundance of the component of the blend with the higher glass transition temperature; at least for the blends studied herein, higher TG is associated with a stronger capacity for intermolecular coupling of the segments. At fixed blend composition this effect governs the shape of the dispersion, as well as being manifested in the composition dependence of the segmental relaxation time. Since the response at lower frequency reflects the contribution of segments residing in regions richer in the high TG component, it is anticipated that the glass transition dispersion in miscible blends will be asymmetrically broadened towards lower frequencies. Application of the model to some miscible blends, including poly(vinylethylene)/polyisoprene, polyvinylmethylether/polystyrene, and tetramethyl polycarbonate/polystyrene), is demonstrated to successfully describe their most prominent features.
Ambiguities in powder pattern indexing: A ternary lattice metric singularity
Authors: Mighell Alan D.
Published: July 2002

A lattice metric singularity occurs when unit cells defining two (or more) lattices yield the identical set of unique calculated d-spacings. The existence of such singularities, therefore, has a practical impact on the indexing of powder patterns. Lattice metric singularities often involve lattices that are in a derivative relationship one to another. A variety of types of singularities are possible depending on the number of different lattices involved (i.e., binary, ternary, quaternary), on the nature of the derivative lattice relationship (i.e., subcell/supercell, composite), on the Bravais type of each of the lattices, and on the the volume ratio(s) of primitive cells defining the lattices. In the laboratory, an encounter with a singularity can lead one into a trap; viz., the investigator using an indexing program, or by other means, may determine only one of the lattices with a high figure of merit. When this happens, it is critical to recognize that there exists more than one indexing solution. In a previous work, a binary singularity was described involving a monoclinic and a rhombohedral lattice. In the present work, we describe a second type of singularity—a ternary singularity—in which the two of the three lattices are in a derivative composite relationship.
Study Provides New Insight Into Female Sex Hormones and Migraines
Authors: Marcus Revital
Published: April 2023

This Medical News article discusses whether hormonal fluctuations and calcitonin gene-related peptide, or CGRP, may cause migraines in some women.
Living Alone and Drug Overdose Deaths in the US
Authors: Olfson Mark , Cosgrove Candace M. , Wall Melanie M. , Blanco Carlos
Published: April 2023

This cohort study examines the risk of drug overdose death in individuals who live alone.
Analyzing trait‐climate relationships within and among taxa using machine learning and herbarium specimens
Authors: Wilde Brendan C. , Bragg Jason G. , Cornwell William
Published: April 2023

Premise

Continental‐scale leaf trait studies can help explain how plants survive in different environments, but large data sets are costly to assemble at this scale. Automating the measurement of digitized herbarium collections could rapidly expand the data available to such studies. We used machine learning to identify and measure leaves from existing, digitized herbarium specimens. The process was developed, validated, and applied to analyses of relationships between leaf size and climate within and among species for two genera: Syzygium (Myrtaceae) and Ficus (Moraceae).

Methods

Convolutional neural network (CNN) models were used to detect and measure complete leaves in images. Predictions of a model trained with a set of 35 randomly selected images and a second model trained with 35 user‐selected images were compared using a set of 50 labeled validation images. The validated models were then applied to 1227 Syzygium and 2595 Ficus specimens digitized by the National Herbarium of New South Wales, Australia. Leaf area measurements were made for each genus and used to examine links between leaf size and climate.

Results

The user‐selected training method for Syzygium found more leaves (9347 vs. 8423) using fewer training masks (218 vs. 225), and found leaves with a greater range of sizes than the random image training method. Within each genus, leaf size was positively associated with temperature and rainfall, consistent with previous observations. However, within species, the associations between leaf size and environmental variables were weaker.

Conclusions

CNNs detected and measured leaves with levels of accuracy useful for trait extraction and analysis and illustrate the potential for machine learning of herbarium specimens to massively increase global leaf trait data sets. Within‐species relationships were weak, suggesting that population history and gene flow have a strong effect at this level. Herbarium specimens and machine learning could expand sampling of trait data within many species, offering new insights into trait evolution.
Harvest of the Sun: A cost effective solar thermal technology to simultaneously provide affordable energy and generate mass employment in developing Sun‐belt regions
Authors: Gharat Punit V. , Bhalekar Snehal S. , Biswas Deepankar , Dalvi Vishwanath H. , Shenoy Narendra V. , Panse Sudhir V. , Deshmukh Suresh P. , Joshi Jyeshtharaj B.
Published: April 2023

Here we report a cost effective solar harvestor based on parabolic trough collector (PTC) technology with three remarkable characteristics. First, unlike the expensive (~USD 170/m2‐aperture) state‐of‐the‐art PTCs which use large curved reflectors, this reflector is composed of a plurality of long rectangular mirrored strips of glass placed on laser‐cut parabolic ribs to yield an accurate reflecting shape giving a concentration ratio of 38 (comparable to the state‐of‐the‐art). Second, the entire assembly is on bolts. It can be delivered in boxes, and can easily be erected on desired site: in stark contrast to state‐of‐the art PTCs, which need to be fabricated in a specially equipped workshop and installed using cranes. Third, by incorporating several innovations guided by comprehensive optimization using finite element analysis and ray tracing, the cost of the system has been brought below USD 82/m2‐aperture (as per the recommendation of NAE). Taken together, this solution promises more cost‐effective base load electricity than Photovoltaics, hence goes a long way toward meeting the UN Sustainable Development Goal of Affordable Energy (SDG‐7). Further, it can be fabricated using industrial equipment that is readily available in the developing regions of the Sun‐belt and installed using unskilled labor. Hence, it can form the core of a massive, decentralized, micro‐CSP industry that can provide dignified employment to large numbers of people in developing regions (SDG‐8). We have termed this technology Harvest of the Sun.
Organocatalytic Enantioselective Vinylcyclopropane‐Cyclopentene (VCP‐CP) Rearrangement
Authors: Garay Gorka , Hurtado Josebe , Pedrón Manuel , García Lorena , Reyes Efraim , Sánchez‐Díez Eduardo , Tejero Tomás , Carrillo Luisa , Merino Pedro , Vicario Jose L.
Published: April 2023

We have demonstrated that the catalytic and enantioselective vinylcyclopropane‐cyclopentene rearrangement can be carried out on (vinylcyclopropyl)acetaldehydes through activation via enamine intermediates. The reaction makes use of racemic starting materials that, upon ring opening facilitated by the catalytic generation of a donor‐acceptor cyclopropane, deliver an acyclic iminium ion/dienolate intermediate in which all stereochemical information has been deleted. The final cyclization step forms the rearrangement product, showing that chirality transfer from the catalyst to the final compound is highly effective and leads to the stereocontrolled formation of a variety of structurally different cyclopentenes.
Photocatalytic Metal Hydride Hydrogen Atom Transfer Mediated Allene Functionalization by Cobalt and Titanium Dual Catalysis
Authors: Yan Huaipu , Liao Qian , Chen Yuqing , Gurzadyan Gagik G. , Lu Binghui , Wu Chao , Shi Lei
Published: April 2023

Catalytic metal hydride hydrogen atom transfer (MHAT) reactions have proven to be a powerful method for alkene functionalization. This work reports the discovery of Co‐porphines as highly efficient MHAT catalysts with a loading of only 0.01 mol % for unprecedented chemoselective allene functionalization under photoirradiation. Moreover, the newly developed bimetallic strategy by the combination of photo Co‐MHAT and Ti catalysis enabled the successful carbonyl allylation with a wide range of amino, oxy, thio, aryl, and alkyl‐allenes providing expedient access to valuable β‐functionalized homoallylic alcohols in over 100 examples with exceptional regio‐ and diastereoselectivity. Mechanism studies and DFT calculations supported that selectively transferring hydrogen atoms from cobalt hydride to allenes and generating allyl radicals is the key step in the catalytic cycle.
Anion‐Dependent Redox Chemistry of p‐Type Poly(vinyldimethylphenazine) Cathode Materials
Authors: Duan An , Wang Ziheng , Huang Xiaoyu , Li Yongjun
Published: April 2023

Metal‐free organic electrode materials have attracted vast research attention owing to their designable structures and tunable electrochemical properties. Although n‐type cathode materials could be used in various metal‐ion batteries, p‐type ones with high potential can deliver high energy density. Herein, we report a new p‐type polymeric cathode material, poly(2‐vinyl‐5,10‐dimethyl‐dihydrophenazine) (PVDMP), with a theoretical capacity of 227 mAh g−1. PVDMP featuring two‐step redox reaction will be doped by two anions to maintain electroneutrality during oxidation, which resulted in an anion‐dependent electrochemical behavior of PVDMP‐based cathode. The suitable dopant anion for PVDMP was selected and the doping mechanism was confirmed. Under the optimized condition, PVDMP cathode can deliver a high initial capacity of 220 mAh g−1 at 5 C and even remains 150 mAh g−1 after 3900 cycles. This work not only provides a new kind of p‐type organic cathode materials but also deepens the understanding of its anion‐dependent redox chemistry.
Mercaptoamine‐assisted Post‐encapsulation of Metal Nanoparticles within Preformed Zeolites and their Analogues for Hydroisomerization and Methane Decomposition
Authors: Song Minseok , Eom Eunji , Shin Jae Won , Cho Hae Sung , Kim Jeong‐Chul , Jo Changbum
Published: April 2023

We report a general synthetic strategy for post‐encapsulation of metal nanoparticles within preformed zeolites using post‐synthetic modification. Both anionic and cationic precursors to metal nanoparticle are supported on 8‐ and 10‐membered ring zeolites and analogues during wet impregnation using 2‐aminoethanethiol (AET) as a bi‐grafting agent. Thiol groups are coordinated to metal centers, whereas amine moieties are dynamically attached to micropore walls via acid‐base interactions. The dynamic acid‐base interactions cause the even distribution of the metal‐AET complex throughout the zeolite matrix. These processes encapsulate Au, Rh, and Ni precursors within the CHA, *MRE, MFI zeolite, and SAPO‐34 zeolite analogues, for which small channel apertures preclude the post‐synthesis impregnation of metal precursors. Sequential activation forms small and uniform nanoparticles (1–2.5 nm in diameter), as confirmed through electron microscopy and X‐ray absorption spectroscopy. Containment within the small micropores protected the nanoparticles against harsh thermal sintering conditions and prevented the fouling of the metal surface by coke, thus resulting in a high catalytic performance in n‐dodecane hydroisomerization and methane decomposition. The remarkable specificity of the thiol to metal precursors and the dynamic acid‐base interaction make these protocols extendable to various metal‐zeolite systems, suitable for shape‐selective catalysts in challenging chemical environments.
Using eDNA and SCUBA surveys for detection and monitoring of a threatened marine cryptic fish
Authors: Bessell Tyson J. , Appleyard Sharon A. , Stuart‐Smith Rick D. , Johnson Olivia J. , Ling Scott D. , Heather Freddie J. , Lynch Tim P. , Barrett Neville S. , Stuart‐Smith Jemina
Published: April 2023

Quantification of species’ spatial distributions and population trends is crucial for successful conservation efforts. Obtaining sufficient population data, however, is often difficult in the marine environment, especially for rare fish and invertebrate species that are small, cryptic and very difficult to detect.

This study sought to understand the effort required to search for undiscovered populations of small, cryptic, marine species in shallow vegetated coastal habitats and track population numbers, using the Critically Endangered red handfish (Thymichthys politus) as a representative species. A sampling strategy was designed using a combination of environmental DNA (eDNA) and structured underwater scuba surveys of life‐like 3D‐printed ‘handfish replicas’ to estimate detectability and ultimately determine whether current population monitoring is adequately covering the remaining habitat occupied by the species.

Tested over scales of hundreds of metres to kilometres, the eDNA assays performed relatively poorly in situ, detecting red handfish presence in only ~13% of samples collected from the centre of a known, yet low‐density, red handfish site. In contrast, underwater searches for independently placed handfish replicas by scuba divers indicated that mean detection probabilities at finer scales (~100 m) ranged from 57 to 97%. Near certain (95% probability) detection of an adult handfish was achievable with only one to three surveys (300 m2 belt transects), depending on the habitat complexity.

While other species will vary in detectability using eDNA and underwater searches, these findings give insight into the general effort required for the detection of small, rare species inhabiting vegetated coastal environments. Such knowledge not only helps to refine monitoring and conservation efforts for known threatened species, but may also assist in identifying other inconspicuous species whose population declines may otherwise go unnoticed.
Archaeology of animate ancestors and entanglement at Mayarnjarn in the Wellington Range region, Northern Territory
Authors: Wright Duncan , Nejman Ladislav , Skitmore Steve , Brennan Wayne , Parkes Rebecca , Lamilami Ronald , Taçon Paul S. C.
Published: April 2023

The Wellington Range region, in far Northern Australia, provides a remarkable record of cultural encounter. Cathedral‐sized rock art galleries include contact imagery referencing Macassan and European visitors while lithic artefact assemblages echo social mobility between Indigenous groups occurring from at least the mid Holocene period. In this paper, we continue the trajectory of archaeological research in this region by examining community entanglement over the longue durée, focusing on the Mayarnjarn rock‐shelter complex. Specifically, and following advice from traditional custodians, the authors complement archaeological excavation results with reflections on interactions between Traditional Mawng speaking Owners and archaeologists occurring during the 2016 and 2018 field seasons. This paper provides a cultural chronology built around both OSL and radiocarbon dates, a first for the region, indicating site activities dating from the terminal Pleistocene. An increase in exotic artefacts and presence of paintings belonging to a pan‐Arnhem land rock art tradition suggests widening social networks during the Holocene. Insight into the nuanced nature of interactions, also the role of animate objects as relationship referents, emerge through ethnography and experience as the field season unfolds.