bluuebunny/crossref_metadata_2025 huggingface dataset:
The labile brain. I. Neuronal transients and nonlinear coupling
Authors: Friston Karl J.
Published: July 2002

In this, the first of three papers, the nature of, and motivation for, neuronal transients is described in relation to characterizing brain dynamics. This paper deals with some basic aspects of neuronal dynamics, interactions, coupling and implicit neuronal codes. The second paper develops neuronal transients and nonlinear coupling in the context of dynamic instability and complexity, and suggests that instability or lability is necessary for adaptive self–organization. The final paper addresses the role of neuronal transients through information theory and the emergence of spatio–temporal receptive fields and functional specialization.

By considering the brain as an ensemble of connected dynamic systems one can show that a sufficient description of neuronal dynamics comprises neuronal activity at a particular time and its recent history. This history constitutes a neuronal transient. As such, transients represent a fundamental metric of neuronal interactions and, implicitly, a code employed in the functional integration of brain systems. The nature of transients, expressed conjointly in distinct neuronal populations, reflects the underlying coupling among populations. This coupling may be synchronous (and possibly oscillatory) or asynchronous. A critical distinction between synchronous and asynchronous coupling is that the former is essentially linear and the latter is nonlinear. The nonlinear nature of asynchronous coupling enables the rich, context–sensitive interactions that characterize real brain dynamics, suggesting that it plays a role in functional integration that may be as important as synchronous interactions. The distinction between linear and nonlinear coupling has fundamental implications for the analysis and characterization of neuronal interactions, most of which are predicated on linear (synchronous) coupling (e.g. crosscorrelograms and coherence). Using neuromagnetic data it is shown that nonlinear (asynchronous) coupling is, in fact, more abundant and can be more significant than synchronous coupling.
Measurement of bacterial gene expression in vivo
Authors: Hautefort Isabelle , Hinton Jay C. D.
Published: July 2002

The complexities of bacterial gene expression during mammalian infection cannot be addressed byin vitroexperiments. We know that the infected host represents a complex and dynamic environment, which is modified during the infection process, presenting a variety of stimuli to which the pathogen must respond if it is to be successful. This response involves hundreds ofivi(in vivo– induced) genes which have recently been identified in animal and cell culture models using a variety of technologies including in vivo expression technology, differential fluorescence induction, subtractive hybridization and differential display. Proteomic analysis is beginning to be used to identify IVI proteins, and has benefited from the availability of genome sequences for increasing numbers of bacterial pathogens. The patterns of bacterial gene expression during infection remain to be investigated. Areivigenes expressed in an organ–specific or cell–type–specific fashion ? New approaches are required to answer these questions. The uses of the immunologically based in vivo antigen technology system,in situPCR and DNA microarray analysis are considered. This review considers existing methods for examining bacterial gene expression in vivo, and describes emerging approaches that should further our understanding in the future.
Technologies for the study of gene and protein expression in
Plasmodium
Authors: Carucci Daniel J.
Published: July 2002

With the imminent completion of the genome sequences of several species of
Plasmodium
, attention is now turning to the exploitation of these genomic sequence data for vaccine, drug and diagnostic development. Several technologies have been developed over the past decade to assist in the determination of gene and protein expression on a global scale. Of these, DNA microarrays, novel high–throughput proteomic technologies and recombinational cloning technologies are lowering the barrier to functional genomic studies in
Plasmodium
. Of equal importance is the capacity to manipulate, store, retrieve and analyse the tremendous quantity of data generated from these genomic studies. This paper will address the use of these technologies as well as some of the computational tools that will be ultimately required to adequately study gene and protein expression in
Plasmodium
.
kuzbanian-mediated cleavage of Drosophila Notch
Authors: Lieber Toby , Kidd Simon , Young Michael W.
Published: July 2002

Loss of Kuzbanian, a member of the ADAM family of metalloproteases, produces neurogenic phenotypes in Drosophila. It has been suggested that this results from a requirement forkuzbanian-mediated cleavage of the Notch ligand Delta. Using transgenic Drosophila expressing transmembrane Notch proteins, we show that kuzbanian, independent of any role in Delta processing, is required for the cleavage of Notch. We show that Kuzbanian can physically associate with Notch and that removal ofkuzbanian activity by RNA-mediated interference inDrosophila tissue culture cells eliminates processing of ligand-independent transmembrane Notch molecules. Our data suggest that in Drosophila, kuzbanian can mediate S2 cleavage of Notch.
On the involvement of electron transfer reactions in the fluorescence decay kinetics heterogeneity of proteins
Authors: Ababou Abdessamad , Bombarda Elisa
Published: July 2002

Time‐resolved fluorescence study of single tryptophan‐containing proteins, nuclease, ribonuclease T1, protein G, glucagon, and mastoparan, has been carried out. Three different methods were used for the analysis of fluorescence decays: the iterative reconvolution method, as reviewed and developed in our laboratory, the maximum entropy method, and the recent method that we called “energy transfer” method. All the proteins show heterogeneous fluorescence kinetics (multiexponential decay). The origin of this heterogeneity is interpreted in terms of current theories of electron transfer process, which treat the electron transfer process as a radiationless transition. The theoretical electron transfer rate was calculated assuming the peptide bond carbonyl as the acceptor site. The good agreement between experimental and theoretical electron‐transfer rates leads us to suggest that the electron‐transfer process is the principal quenching mechanism of Trp fluorescence in proteins, resulting in heterogeneous fluorescence kinetics. Furthermore, the origin of apparent homogeneous fluorescence kinetics (monoexponential decay) in some proteins also can be explained on the basis of electron‐transfer mechanism.
Crystal structure of the transcription factor sc‐mtTFB offers insights into mitochondrial transcription
Authors: Schubot Florian D. , Chen Chun‐Jung , Rose John P. , Dailey Tamara A. , Dailey Harry A. , Wang Bi‐Cheng
Published: July 2002

Although it is commonly accepted that binding of mitochondrial transcription factor sc‐mtTFB to the mitochondrial RNA polymerase is required for specific transcription initiation in Saccharomyces cerevisiae, its precise role has remained undefined. In the present work, the crystal structure of sc‐mtTFB has been determined to 2.6 Å resolution. The protein consists of two domains, an N‐terminal α/β‐domain and a smaller domain made up of four α‐helices. Contrary to previous predictions, sc‐mtTFB does not resemble Escherichia coli σ‐factors but rather is structurally homologous to rRNA methyltransferase ErmC'. This suggests that sc‐mtTFB functions as an RNA‐binding protein, an observation standing in contradiction to the existing model, which proposed a direct interaction of sc‐mtTFB with the mitochondrial DNA promoter. Based on the structure, we propose that the promoter specificity region is located on the mitochondrial RNA polymerase and that binding of sc‐mtTFB indirectly mediates interaction of the core enzyme with the promoter site.
Persistently conserved positions in structurally similar, sequence dissimilar proteins: Roles in preserving protein fold and function
Authors: Friedberg Iddo , Margalit Hanah
Published: July 2002

Many protein pairs that share the same fold do not have any detectable sequence similarity, providing a valuable source of information for studying sequence‐structure relationship. In this study, we use a stringent data set of structurally similar, sequence‐dissimilar protein pairs to characterize residues that may play a role in the determination of protein structure and/or function. For each protein in the database, we identify amino‐acid positions that show residue conservation within both close and distant family members. These positions are termed “persistently conserved”. We then proceed to determine the “mutually” persistently conserved (MPC) positions: those structurally aligned positions in a protein pair that are persistently conserved in both pair mates. Because of their intra‐ and interfamily conservation, these positions are good candidates for determining protein fold and function. We find that 45% of the persistently conserved positions are mutually conserved. A significant fraction of them are located in critical positions for secondary structure determination, they are mostly buried, and many of them form spatial clusters within their protein structures. A substitution matrix based on the subset of MPC positions shows two distinct characteristics: (i) it is different from other available matrices, even those that are derived from structural alignments; (ii) its relative entropy is high, emphasizing the special residue restrictions imposed on these positions. Such a substitution matrix should be valuable for protein design experiments.
The distinctive functions of the two structural calcium atoms in bovine pancreatic deoxyribonuclease
Authors: Chen Ching‐Ying , Lu Shao‐Chun , Liao Ta‐Hsiu
Published: July 2002

The two amino acid residues, Asp 99 and Asp 201, involved in the coordination of the two calcium atoms in the X‐ray structure of bovine pancreatic (bp) DNase, were individually changed by site‐directed mutagenesis. The two altered proteins, brDNase(D99A) and brDNase(D201A) were expressed in Escherichia coli and purified by anion exchange chromatography. Equilibrium dialysis showed that mutation destroyed one Ca2+‐binding site each in brDNase(D99A) and brDNase(D201A). Compared with bpDNase, the Vmax value for brDNase(D99A) remained unchanged and that for brDNase(D201A) was decreased, whereas the Km values for the two variants were increased two‐ to threefold when the DNA hydrolytic hyperchromicity assay was used. Like bpDNase, brDNase(D99A) was able to make double scission on duplex DNA with Mg2+ plus Ca2+ and was effectively protected by Ca2+ from the trypsin inactivation. But under the same conditions, brDNase(D201A) lost the double‐scission ability and was not protected by Ca2+. Nevertheless, the two variant proteins retained the characteristics of the Ca2+‐induced conformational changes and the Ca2+ protection against the β‐mercaptoethanol disruption of the essential disulfide bond, suggesting that other weaker Ca2+‐binding sites not found in the X‐ray structure were responsible for these properties. Therefore, the two structural calcium atoms are not for maintaining the overall conformation of the active DNase, as it has been indicated in the X‐ray analysis, but rather play the role in the fine‐tuning of the DNase activity.
Crystal structure of a cyanobacterial phytochrome response regulator
Authors: Im Young Jun , Rho Seong‐Hwan , Park Chung‐Mo , Yang Song‐Sook , Kang Jeong‐Gu , Lee Jae Young , Song Pill‐Soon , Eom Soo Hyun
Published: July 2002

The two‐component signal transduction pathway widespread in prokaryotes, fungi, molds, and some plants involves an elaborate phosphorelay cascade. Rcp1 is the phosphate receiver module in a two‐component system controlling the light response of cyanobacteria Synechocystis sp. via cyanobacterial phytochrome Cph1, which recognizes Rcp1 and transfers its phosphoryl group to an aspartate residue in response to light. Here we describe the crystal structure of Rcp1 refined to a crystallographic R‐factor of 18.8% at a resolution of 1.9 Å. The structure reveals a tightly associated homodimer with monomers comprised of doubly wound five‐stranded parallel β‐sheets forming a single‐domain protein homologous with the N‐terminal activator domain of other response regulators (e.g., chemotaxis protein CheY). The three‐dimensional structure of Rcp1 appears consistent with the conserved activation mechanism of phosphate receiver proteins, although in this case, the C‐terminal half of its regulatory domain, which undergoes structural changes upon phosphorylation, contributes to the dimerization interface. The involvement of the residues undergoing phosphorylation‐induced conformational changes at the dimeric interface suggests that dimerization of Rcp1 may be regulated by phosphorylation, which could affect the interaction of Rcp1 with downstream target molecules.
Modeling of the bacterial luciferase‐flavin mononucleotide complex combining flexible docking with structure‐activity data
Authors: Lin Leo Yen‐Cheng , Sulea Traian , Szittner Rose , Vassilyev Vladislav , Purisima Enrico O. , Meighen Edward A.
Published: July 2002

Although the crystal structure of Vibrio harveyi luciferase has been elucidated, the binding sites for the flavin mononucleotide and fatty aldehyde substrates are still unknown. The determined location of the phosphate‐binding site close to Arg 107 on the α subunit of luciferase is supported here by point mutagenesis. This information, together with previous structure‐activity data for the length of the linker connecting the phosphate group to the isoalloxazine ring represent important characteristics of the luciferase‐bound conformation of the flavin mononucleotide. A model of the luciferase–flavin complex is developed here using flexible docking supplemented by these structural constraints. The location of the phosphate moiety was used as the anchor in a flexible docking procedure performed by conformation search by using the Monte Carlo minimization approach. The resulting databases of energy‐ranked feasible conformations of the luciferase complexes with flavin mononucleotide, ω‐phosphopentylflavin, ω‐phosphobutylflavin, and ω‐phosphopropylflavin were filtered according to the structure‐activity profile of these analogs. A unique model was sought not only on energetic criteria but also on the geometric requirement that the isoalloxazine ring of the active flavin analogs must assume a common orientation in the luciferase‐binding site, an orientation that is also inaccessible to the inactive flavin analog. The resulting model of the bacterial luciferase–flavin mononucleotide complex is consistent with the experimental data available in the literature. Specifically, the isoalloxazine ring of the flavin mononucleotide interacts with the Ala 74–Ala 75 cis‐peptide bond as well as with the Cys 106 side chain in the α subunit of luciferase. The model of the binary complex reveals a distinct cavity suitable for aldehyde binding adjacent to the isoalloxazine ring and flanked by other key residues (His 44 and Trp 250) implicated in the active site.
Transthyretin slowly exchanges subunits under physiological conditions: A convenient chromatographic method to study subunit exchange in oligomeric proteins
Authors: Schneider Frank , Hammarström Per , Kelly Jeffery W.
Published: July 2002

Transthyretin (TTR) subunits were labeled with a charge‐modifying tag to evaluate the possibility of subunit exchange between tetramers under physiological conditions. Starting with a mixture of two TTR homotetramers, one having all subunits tagged at the N termini and the other composed of untagged subunits, heterotetramer formation as a function of time and temperature was evaluated using ion exchange chromatography. The data indicate that the subunit exchange can occur under native conditions at physiological pH in vitro, albeit slowly. Wild‐type TTR exchanges subunits on a timescale of days at 37°C and on a timescale of hours at 4°C. The familial amyloid polyneuropathy‐associated variant V30M exchanges subunits at the same rate as wild‐type TTR at 4°C but slower and less efficiently at 37°C. Small molecule tetramer stabilizers abolish TTR subunit exchange, supporting a dissociative mechanism.
Temperature dependence of commercially available diode detectors
Authors: Saini Amarjit S. , Zhu Timothy C.
Published: July 2002

Temperature dependence of commercially available n‐ and p‐type diodes were studied experimentally under both high instantaneous dose rate (pulsed) and low dose rate (continuous) radiation. The sensitivity versus temperature was measured at or 100 cm, and 5 cm depth in a water phantom between 10 °C and 35 °C. The response was linear for all the diode detectors. The temperature coefficient (or sensitivity variation with temperature, svwt) was dose rate independent for preirradiated diodes. They were and for QED p‐type, EDP p‐type, and Isorad n‐type diodes, respectively. The temperature coefficient for unirradiated n‐type diodes was different under low dose rate [(0.16 to 0.45)%/°C, continuous, cobalt] and high instantaneous dose rate pulsed radiation]. Moreover, the temperature coefficient varies among individual diodes. Similarly, the temperature coefficient for a special unirradiated QED p‐type diode was different under low dose rate (0.34%/°C, cobalt) and high instantaneous dose rate pulsed radiation]. Sufficient preirradiation can eliminate dose rate dependence of the temperature coefficient. On the contrary, preirradiation cannot eliminate dose rate dependence of the diode sensitivity itself.
A consistent set of neutron kerma coefficients from thermal to 150 MeV for biologically important materials
Authors: Chadwick M. B. , Barschall H. H. , Caswell R. S. , DeLuca P. M. , Hale G. M. , Jones D. T. L. , MacFarlane R. E. , Meulders J. P. , Schuhmacher H. , Schrewe U. J. , Wambersie A. , Young P. G.
Published: July 2002

Neutron cross sections for nonelastic and elastic reactions on a range of elements have been evaluated for incident energies up to 150 MeV. These cross sections agree well with experimental cross section data for charged‐particle production as well as neutron and photon production. Therefore they can be used to determine kerma coefficients for calculations of energy deposition by neutrons in matter. Methods used to evaluate the neutron cross sections above 20 MeV, using nuclear model calculations and experimental data, are described. Below 20 MeV, the evaluated cross sections from the ENDF/B‐VI library are adopted. Comparisons are shown between the evaluated charged‐particle production cross sections and measured data. Kerma coefficients are derived from the neutron cross sections, for major isotopes of H, C, N, O, Al, Si, P, Ca, Fe, Cu, W, Pb, and for ICRU‐muscle, A‐150 tissue‐equivalent plastic, and other compounds important for treatment planning and dosimetry. Numerous comparisons are made between our kerma coefficients and experimental kerma coefficient data, to validate our results, and agreement is found to be good. An important quantity in neutron dosimetry is the kerma coefficient ratio of ICRU‐muscle to A‐150 plastic. When this ratio is calculated from our kerma coefficient data, and averaged over the neutron energy spectra for higher‐energy clinical therapy beams [three beams, and a beam], a value of is obtained. Kerma ratios for water to A‐150 plastic, and carbon to oxygen, are also compared with measurements where available.
Anomalies in quantum mechanics: The 1/r2 potential
Authors: Coon Sidney A. , Holstein Barry R.
Published: July 2002

An anomaly is said to occur when a symmetry that is valid classically becomes broken as a result of quantization. Although most manifestations of this phenomenon are in the context of quantum field theory, there are at least two cases in quantum mechanics—the two-dimensional delta function interaction and the 1/r2 potential. The former has been treated in this journal; in this article we discuss the physics of the latter together with experimental consequences.
Above, below and beyond Brownian motion
Authors: Shlesinger Michael F. , Klafter Joseph , Zumofen Gert
Published: July 2002

Brownian motion represents simple diffusion random walk processes. More complex random walk processes also can occur when probability distributions describing the random jump distances and times have infinite moments. We explore the manner in which these distributions can arise and how they underlie various scaling laws that play an important role in both random and deterministic systems.
Monaural and binaural detection of sinusoidal phase modulation of a 500-Hz tone
Authors: Witton Caroline , Green Gary G. R. , Rees Adrian , Henning G. Bruce
Published: July 2002

The detectability of phase modulation was measured for three subjects in two-alternative temporal forced-choice experiments. In experiment 1, the detectability of sinusoidal phase modulation in a 1500-ms burst of an 80-dB (SPL), 500-Hz sinusoidal carrier presented to the left ear (monaural condition) was measured. The experiment was repeated with an 80-dB, 500-Hz static (unmodulated) tone at the right ear (dichotic condition). At a modulation rate of 1 Hz, subjects were an order of magnitude more sensitive to phase modulation in the dichotic condition than in the monaural condition. The dichotic advantage decreased monotonically with increasing modulation rate. Subjects ceased to detect movement in the dichotic stimulus above 10 Hz, but a dichotic advantage remained up to a modulation rate of 40 Hz. Thus, although sound movement detection is sluggish, detection of internal phase modulation is not. In experiment 2, thresholds for detecting 2-Hz phase modulation were measured in the dichotic condition as a function of the level of the pure tone in the right ear. The dichotic advantage persisted even when the level of the pure tone was reduced by 50 dB or more. The findings demonstrate a large dichotic advantage which persists to high modulation rates and which depends very little on interaural level differences.
Target strength measurements of Hawaiian mesopelagic boundary community animals
Authors: Benoit-Bird Kelly J. , Au Whitlow W. L.
Published: July 2002

A 200-kHz echosounder modified to digitize the envelope of the received echoes directly into a computer was used to measure the ex situ target strength (TS) of live animals from the Hawaiian mesopelagic boundary community as a function of animal size, tilt and roll angle, and biological classification. Dorsal aspect TS (in dB//1 m) at 200 kHz was related to the animal’s length: myctophid fish TS=20 log (standard length in cm)−58.8, r2=0.91, squid TS=18.8 log (mantle length in cm)−61.7, r2=0.81, shrimp TS=19.4 log (length in cm)−74.1, r2=0.83. Tilting the fish 5° and 10° changed the measured TS by up to 3.0 dB, decreasing TS as the fish was tilted forward and increasing TS as the fish was tilted backwards. In shrimp, forward tilt increased TS while backward tilt decreased TS by up to 3.3 dB. No consistent trend in squid TS change was observed with tilt angle. Roll angles of 5° and 10° increased the TS of all groups by up to 3.0 dB. Myctophid lateral aspect TS was consistently about 6 dB higher than the dorsal TS. Physiological analysis of the fishes’ swimbladders revealed that the swimbladder is not the dominant scattering mechanism in the myctophid fishes studied.
Basilar-membrane nonlinearity and the growth of forward masking
Authors: Plack Christopher J. , Oxenham Andrew J.
Published: July 2002

Forward masking growth functions were measured for pure-tone maskers and signals at 2 and 6 kHz as a function of the silent interval between the masker and signal. The inclusion of conditions involving short signals and short masker-signal intervals ensured that a wide range of signal thresholds were recorded. A consistent pattern was seen across all the results. When the signal level was below about 35 dB SPL the growth of masking was shallow, so that signal threshold increased at a much slower rate than masker level. When the signal level exceeded this value, the masking function steepened, approaching unity (linear growth) at the highest masker and signal levels. The results are inconsistent with an explanation for forward-masking growth in terms of saturating neural adaptation. Instead the data are well described by a model incorporating a simulation of the basilar-membrane response at characteristic frequency (which is almost linear at low levels and compressive at higher levels) followed by a sliding intensity integrator or temporal window. Taken together with previous results, the findings suggest that the principle nonlinearity in temporal masking may be the basilar membrane response function, and that subsequent to this the auditory system behaves as if it were linear in the intensity domain.
Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms
Authors: Stanton Timothy K. , Chu Dezhang , Wiebe Peter H. , Martin Linda V. , Eastwood Robert L.
Published: July 2002

The acoustic scattering properties of live individual zooplankton from several gross anatomical groups have been investigated. The groups involve (1) euphausiids (Meganyctiphanes norvegica) whose bodies behave acoustically as a fluid material, (2) gastropods (Limacina retroversa) whose bodies include a hard elastic shell, and (3) siphonophores (Agalma okeni or elegans and Nanomia cara) whose bodies contain a gas inclusion (pneumatophore). The animals were collected from ocean waters off New England (Slope Water, Georges Bank, and the Gulf of Maine). The scattering properties were measured over parts or all of the frequency range 50 kHz to 1 MHz in a laboratory-style pulse-echo setup in a large tank at sea using live fresh specimens. Individual echoes as well as averages and ping-to-ping fluctuations of repeated echoes were studied. The material type of each group is shown to strongly affect both the overall echo level and pattern of the target strength versus frequency plots. In this first article of a two-part series, the dominant scattering mechanisms of the three animal types are determined principally by examining the structure of both the frequency spectra of individual broadband echoes and the compressed pulse (time series) output. Other information is also used involving the effect on overall levels due to (1) animal orientation and (2) tissue in animals having a gas inclusion (siphonophores). The results of this first paper show that (1) the euphausiids behave as weakly scattering fluid bodies and there are major contributions from at least two parts of the body to the echo (the number of contributions depends upon angle of orientation and shape), (2) the gastropods produce echoes from the front interface and possibly from a slow-traveling circumferential (Lamb) wave, and (3) the gas inclusion of the siphonophore dominates the echoes, but the tissue plays a role in the scattering and is especially important when analyzing echoes from individual animals on a ping-by-ping basis. The results of this paper serve as the basis for the development of acoustic scattering models in the companion paper [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998)].
Vocal tract area functions for an adult female speaker based on volumetric imaging
Authors: Story Brad H. , Titze Ingo R. , Hoffman Eric A.
Published: July 2002

Magnetic resonance imaging (MRI) was used to acquire vocal tract shapes of ten vowels /i, ɪ, ɛ, æ, ʌ, ɑ, ɔ, o, ʊ, u/ and two liquid approximants /ɝ, l/ for a 27-year-old adult female. These images were complemented with additional images acquired with electron beam computed tomography (CT) of /i/ and /ɑ/. Each 3-D shape was condensed into a set of cross-sectional areas of oblique sections perpendicular to the centerline of the vocal tract’s long axis, resulting in an “area function.” Formant frequencies computed for each area function showed reasonable similarity to those determined from the natural (recorded) speech of the imaged subject, but differences suggest that some of the imaged vocal tract shapes were articulated differently during imaging than during recording of natural speech, and also that imaging procedures may have compromised some accuracy for a few shapes. The formant calculations also confirmed the significant effect that the piriform sinus can have on lowering the formant frequencies. A comparison is made between area functions derived using both MRI and CT methods for the vowels /i/ and /ɑ/. Additionally, the area functions reported in this study are compared with those from two previous studies and demonstrate general similarities in shape but also obvious differences that can be attributed to anatomical differences of the imaged subjects and to differences in imaging techniques and image processing methods.
Changes in otoacoustic emissions in a transsexual male during treatment with estrogen
Authors: McFadden Dennis , Pasanen Edward G. , Callaway Narriman Lee
Published: July 2002

Otoacoustic emissions (OAEs) were monitored in two human males undergoing estrogen treatment prior to sex-reversal surgery. In one subject, multiple spontaneous emissions (SOAEs) appeared where none had been evident previously. One reasonable interpretation is that (in this male, at least) androgens normally produced a suppressive effect on the cochlear mechanisms responsible for SOAEs, and that the decline in androgen levels produced by the estrogenic drug led to a reduction in that suppression.
Syllable intelligibility for temporally filtered LPC cepstral trajectories
Authors: Arai Takayuki , Pavel Misha , Hermansky Hynek , Avendano Carlos
Published: July 2002

The intelligibility of syllables whose cepstral trajectories were temporally filtered was measured. The speech signals were transformed to their LPC cepstral coefficients, and these coefficients were passed through different filters. These filtered trajectories were recombined with the residuals and the speech signal reconstructed. The intelligibility of the reconstructed speech segments was then measured in two perceptual experiments for Japanese syllables. The effect of various low-pass, high-pass, and bandpass filtering is reported, and the results summarized using a theoretical approach based on the independence of the contributions in different modulation bands. The overall results suggest that speech intelligibility is not severely impaired as long as the filtered spectral components have a rate of change between 1 and 16 Hz.
Analysis of lateral vibration behavior of railway track at high frequencies using a continuously supported multiple beam model
Authors: Wu T. X. , Thompson D. J.
Published: July 2002

The lateral vibration of railway track at high frequencies is a more difficult research topic, compared with the vertical vibration, because the complex cross-sectional deformation of the rail has to be taken into account. The commonly used models for the lateral vibration are based on the FEM/FSM or a derivation of the FEM. It is inconvenient to calculate responses of the rail to external excitation by these models, especially when the discrete supports of the rail are taken into account. To overcome this barrier a new model for studying the lateral vibration behavior of railway track is developed in this paper. It is a simple model consisting of two infinite Timoshenko beams connected by an array of finite beams. Detailed investigation of the lateral vibration for a free rail and a continuously supported rail has been carried out efficiently using this model. The free wave dispersion relation calculated using this model has been shown to be in good agreement with a FE model. Quite good agreement between the predictions and the measurement data has also been reached in terms of accelerances.
Vibration of beads placed on the basilar membrane in the basal turn of the cochlea
Authors: Cooper Nigel P.
Published: July 2002

Interferometric recordings of sound-evoked vibrations in the basal turn and hook regions of the guinea-pig cochlea are used to show that reflective microbeads (i) follow the motion of the structures on which they are placed, and (ii) do not affect this motion dramatically. Extrapolating these findings to other types of reflective or radioactive material lends support to the findings of numerous studies of cochlear mechanics.
Phonemes, intensity and attention: Differential effects on the mismatch negativity (MMN)
Authors: Szymanski Michael D. , Yund E. William , Woods David L.
Published: July 2002

Auditory event-related potentials (ERPs) to speech sounds were recorded in a demanding selective attention task to measure how the mismatch negativity (MMN) was affected by attention, deviant feature, and task relevance, i.e., whether the feature was target or nontarget type. With vowel-consonant-vowel (VCV) disyllables randomly presented to the right and left ears, subjects attended to the VCVs in one ear. In different conditions, the subjects responded to either intensity or phoneme deviance in the consonant. The position of the deviance within the VCV also varied, being in the first (VC), second (CV), or both (VC and CV) formant-transition regions. The MMN amplitudes were larger for deviants in the attended ear. Task relevance affected the MMNs to intensity and phoneme deviants differently. Target-type intensity deviants yielded larger MMNs than nontarget types. For phoneme deviants there was no main effect of task relevance, but there was a critical interaction with deviance position. The both position gave the largest MMN amplitudes for target-type phoneme deviants, as it did for target- and nontarget-type intensity deviants. The MMN for nontarget-type phoneme deviants, however, showed an inverse pattern such that the MMN for the both position had the smallest amplitude despite its greater spectro-temporal deviance and its greater detectability when it was the target. These data indicate that the MMN reflects differences in phonetic structure as well as differences in acoustic spectral-energy structure of the deviant stimuli. Furthermore, the task relevance effects demonstrate that top-down controls not only affect the amplitude of the MMN, but can reverse the pattern of MMN amplitudes among different stimuli.
Source levels and estimated yellowfin tuna (Thunnus albacares) detection ranges for dolphin jaw pops, breaches, and tail slaps
Authors: Finneran James J. , Oliver Charles W. , Schaefer Kurt M. , Ridgway Sam H.
Published: July 2002

Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dolphin (Stenella and Delphinus) and yellowfin tuna (Thunnus albacares) to locate and capture the tuna. Identification of a mechanism which facilitates the tuna/dolphin bond may provide a means of exploiting the bond and capturing tuna without catching dolphin. To investigate if tuna may be attracted to low-frequency sounds produced by dolphins, source levels of bottlenose dolphin (Tursiops truncatus) jaw pops, breaches, and tail slaps were experimentally measured and used to estimate the maximum range at which yellowfin could detect similar sounds produced by pelagic species. The effective acoustic stimulus to the tuna was defined as the maximum one-third-octave level between 200 and 800 Hz, the frequency range where T. albacares is most sensitive. Spherical spreading was assumed to predict transmission loss with range. Breaches and jaw pops produced maximum one-third-octave source levels between 200 and 800 Hz of 153 (±4) and 163 (±2) dB re: 1 μPa-m, respectively, which resulted in estimated detection ranges of 340–840 and 660–1040 m, respectively. Tail slaps had lower source levels [max. 141 (±3) dB re: 1 μPa-m] and a maximum detection range of approximately 90–180 m.
Rigid piston approximation for computing the transfer function and angular response of a fiber-optic hydrophone
Authors: Krücker Jochen F. , Eisenberg Alexander , Krix Martin , Lötsch Ralf , Pessel Martin , Trier Hans-Georg
Published: July 2002

The transfer function of a fiber-optic hydrophone (FOH) is computed for various fiber core radii. The hydrophone is modeled as a rigid disk, with plane waves impinging at normal or oblique incidence. The total sound field is written as the sum of the incident field and the field diffracted from the hydrophone. The diffracted field is approximated by the field generated by a vibrating planar piston in an infinite rigid baffle. For normal incidence and a pointlike fiber core, an analytical solution is presented. For finite fiber core radii, and for oblique incidence, the transfer functions are computed numerically. The calculated transfer functions exhibit an oscillatory frequency dependency that is most pronounced for small fiber cores. The solution for a core radius of 2.5 μm can be very well approximated by the analytical solution for a pointlike core at frequencies of up to 30 MHz. The results for normal incidence can be directly employed to deconvolute ultrasonic pressure signals measured with an FOH. From the transfer functions for oblique incidence, the angular response of the hydrophone is calculated. The angular response obtained here differs significantly from the model commonly used for piezoelectric hydrophones. The effective hydrophone radius derived from the angular response shows a strong frequency dependency. For low frequencies, it is found to be larger than the outer fiber radius, whereas it generally lies between the outer radius and the fiber core radius for frequencies above 10 MHz.
Dynamic Investigations of Polymer Solutions in an Extended Range of Frequencies
Authors: Philippoff W.
Published: July 2002

Investigations of the dynamic properties of several polystyrene solutions in the viscous solvent Aroclor 1248 were made, comparing the lower frequency results obtained with the Birnboim instrument with the higher ones in the ultrasonic range using the torsional crystal of Mason. Both sets of values merge well in the overlapping range of reduced frequencies, giving a considerably larger combined range. The viscosity η1 of all the solutions at higher frequencies did not approach that of the solvent but reached a higher asymptotic value, not predicted by theory. This causes cot δ (with δ the “loss angle”) to have a maximum at intermediate frequencies and explains former ultrasonic results. The influence of the polydispersity on the dynamic properties is not large for the loss modulus G″, but is much larger, as theoretically predicted, for the storage modulus G′.
A model for slip at polymer/solid interfaces
Authors: Yarin Alexander L. , Graham Michael D.
Published: July 2002

A steady-state dependence of slip velocity on shear stress at polymer/solid surfaces is derived from a molecular model that includes effects of drag on polymer chains, disentanglement, and detachment and reattachment of chains from the solid surface. The dependence includes two turning points and thus a region where slip velocity is a multivalued function of shear stress. This behavior is consistent with experimental observations of abrupt and hysteretic transitions between regimes of small and large slip. Parameters involved in the model are estimated and a reasonable comparison with experiment is obtained.
X-ray diffraction analysis of ultrathin platinum silicide films deposited on (100) silicon
Authors: Blanton T. N. , Hoople C. R.
Published: July 2002

X-ray diffraction methods have been used successfully for the analysis of platinum silicide films of 100 Å or less in thickness. Conventional X-ray diffraction was utilized for phase identification, planar orientation, and crystalline size determination. Low-angle X-ray specular reflectivity analysis measured film thickness. As the nominal film thickness approached 100 Å, it was observed that the deposited platinum film thickness was larger than expected and longer anneal times would be required to ensure homogeneous platinum silicide phase composition.
Diffusion tensor imaging metrics in diagnosis of HTLV‐1‐associated myelopathy
Authors: Liberato de Matos Sheila N. F. , Ladeia‐Rocha Giovanna , Neto José Abraão Carneiro , de Oliveira Cassius J. V. , Neto César Araújo , Passos Lúcia , Oliveira‐Filho Jamary , Carvalho Edgar M.
Published: March 2022

Objective

In the diagnosis of HTLV‐1‐associated myelopathy (HAM), while magnetic resonance imaging (MRI) is essential to exclude other diseases, its power is limited regarding HAM diagnosis, as only 30% of affected patients present with spinal cord atrophy. Diffusion tensor imaging (DTI) may enable the detection of damage in the white matter microstructure. Here, we quantitatively assess spinal cord damage using DTI and evaluate conventional MRI parameters of the spinal cord in HTLV‐1‐infected individuals.

Methods

This cross‐sectional study involved 33 HTLV‐1 carriers, 28 patients with definite‐HAM, and 11 seronegative healthy subjects (HS). Region‐of‐interest (ROI)‐based fractional anisotropy (FA) and mean diffusivity (MD) measurements were performed in the upper thoracic and lumbar regions of the spinal cord. Thoracic index was defined as 1/ (anteroposterior diameter × transverse diameter) measured at the fifth 5th vertebral level. Receiver operating characteristic (ROC) curve analysis was used to determine optimal cutoff FA, MD, and thoracic index values.

Results

Spinal cord atrophy was observed in 15 (53.6%) patients with definite‐HAM. The area under the ROC curve in the thoracic spinal cord was 0.824 (95% CI, 0.716–0.932), 0.839 (95% CI: 0.736–0.942), and 0.838 (95% CI: 0.728–0.949) for FA, MD, and the thoracic index, respectively. Lower FA and higher MD values were observed in the definite‐HAM group compared to HTLV‐1 carriers and HS at the T5 vertebral level (p < 0.01).

Interpretation

Complementary to conventional MRI, DTI analysis of the spinal cord and thoracic index determination can offer additional insight that may prove useful in the diagnosis of HAM.
The Core‐Shell Magnetic Mesoporous Microspheres Immobilized NHC‐Palladacycles: An Efficient and Recyclable Catalyst for Suzuki‐Miyaura Cross‐Coupling of Pharmaceutical Synthesis
Authors: Zuo Bin , Shao Han , Zheng Yan , Ma Yunhua , Li Wanfang , Huang Mingxian , Deng Qinyue
Published: March 2022

The core‐shell magnetic mesoporous microspheres immobilized NHC‐palladacycles (NHC=N‐heterocyclic carbene) catalyst with constrained aliphatic linker group (Fe3O4@mSiO2@NHC−Pd) were readily prepared by the well‐designed method, which showed higher palladium loading (0.20 mmol g−1) and higher catalytic activity than the non‐mesoporous catalysts (Fe3O4@SiO2@NHC−Pd) prepared by the same process in the Suzuki‐Miyaura cross‐coupling reactions of aryl chlorides and aryl boronic acids. Herein, Fe3O4@mSiO2@NHC−Pd could be used 12 times without significant activity loss, and no palladium leakage was detected in both the product and catalytic residue, highlighting the efficiency of our strategy for immobilizing the catalyst. Remarkably, this approach allows the synthesis of important drug intermediates 2‐aryl‐4‐aminoquinazolines and o‐tolylbenzonitrile (OTBN).
Recent Advances in the Functionalization of Terminal and Internal Alkynes
Authors: Ramani Arti , Desai Bhargav , Patel Monak , Naveen Togati
Published: March 2022

Alkynes are one of the most fundamental and diverse functional groups utilized in organic synthesis. Over the past few years, the development of efficient synthetic methodologies for the functionalization of alkynes has been an active area of research. A plethora of alkyne functionalization reactions have been reported in the literature to construct functionalized alkynes and alkene scaffolds, which are important building blocks in many natural products, pharmaceuticals, and key intermediates in various synthetic transformations. In this review, we describe the most recent advances in the functionalization of alkynes with an emphasis on substrate scope, limitations, regioselectivity control and applications of these reactions. This review covers the literature from 2016 to 2021.
Dietary protein source matters for changes in inflammation measured by urinaryC‐reactiveprotein in rural polish women
Authors: Ban Hayley E. , Lee Katharine M. N. , Rogers‐LaVanne Mary P. , Zabłocka‐Słowińska Katarzyna , Galbarczyk Andrzej , Jasienska Grazyna , Clancy Kathryn B. H.
Published: March 2022

Objectives

Multiple macronutrients have been shown to affect systemic inflammation, a well‐known predictor of chronic disease. Less often, varying sources of these macronutrients are examined. Different subsistence environments lead to varying access to protein sources which, combined with physical activity patterns, may lead to different relationships than among more typically studied sedentary, industrialized populations. This study hypothesizes an association between dietary protein intake and urinary C‐reactive protein (CRP) concentration in women from a rural, agrarian Polish community.

Materials and Methods

We assessed protein intake and their sources for 80 nonsmoking, premenopausal Polish women who were not pregnant, nursing, or on hormonal birth control during the study or within the previous 6 months. Each participant completed multiple 24‐hr dietary recalls during one menstrual cycle. Participants collected morning void urinary samples daily over one menstrual cycle for urinary CRP analysis. We analyzed relationships between plant and animal protein intake and CRP over the menstrual cycle by multiple linear regression.

Results

Plant protein in cereal foods was significantly positively associated with cycle‐average urinary CRP concentrations (p < 0.05) after controlling for body fat percent, total energy intake, and dietary fiber. Foods containing animal protein were not significantly associated with CRP.

Discussion

Contents of this population's main plant and animal protein sources differ from those of more commonly studied industrialized populations. Within the context of a population's typical diet, more emphasis may need to be placed on particular source of protein consumed, beyond plant versus animal, in order to understand relationships with CRP.
Association of Cardiac Biomarkers With Cardiovascular Outcomes in Patients With Psoriatic Arthritis and Psoriasis: A Longitudinal Cohort Study
Authors: Colaco Keith , Lee Ker‐Ai , Akhtari Shadi , Winer Raz , Welsh Paul , Sattar Naveed , McInnes Iain B. , Chandran Vinod , Harvey Paula , Cook Richard J. , Gladman Dafna D. , Piguet Vincent , Eder Lihi
Published: March 2022

Objective

In patients with psoriatic disease (PsD), we determined whether cardiac troponin I (cTnI) and N‐terminal pro–brain natriuretic peptide (NT‐proBNP) were associated with carotid plaque burden and the development of cardiovascular events independent of the Framingham Risk Score (FRS).

Methods

Among 1,000 patients with PsD, carotid total plaque area (TPA) was measured in 358 participants at baseline. Cardiac troponin I and NT‐proBNP were measured using automated clinical assays. The association between cardiac biomarkers and carotid atherosclerosis was assessed by multivariable regression after adjusting for cardiovascular risk factors. Improvement in the prediction of cardiovascular events beyond the FRS was tested using measures of risk discrimination and reclassification.

Results

In univariate analyses, cTnI (β coefficient 0.52 [95% confidence interval (95% CI) 0.3, 0.74], P < 0.001) and NT‐proBNP (β coefficient 0.24 [95% CI 0.1, 0.39], P < 0.001) were associated with TPA. After adjusting for cardiovascular risk factors, the association remained statistically significant for cTnI (adjusted β coefficient 0.21 [95% CI 0, 0.41], P = 0.047) but not for NT‐proBNP (P = 0.21). Among the 1,000 patients with PsD assessed for cardiovascular risk prediction, 64 patients had incident cardiovascular events. When comparing a base model (with the FRS alone) to expanded models (with the FRS plus cardiac biomarkers), there was no improvement in predictive performance.

Conclusion

In patients with PsD, cTnI may reflect the burden of atherosclerosis, independent of traditional cardiovascular risk factors. Cardiac troponin I and NT‐proBNP are associated with incident cardiovascular events independent of the FRS, but further study of their role in cardiovascular risk stratification is warranted.