bluuebunny/crossref_metadata_2025 huggingface dataset:
Intestinal permeability and contractility in murine colitis
Authors: van Meeteren M. E. , van Bergeijk J. D. , van Dijk A. P. M. , Tak C. J. A. M. , Meijssen M. A. C. , Zijlstra F. J.
Published: July 2002

We developed an in vitro organ bath method to measure permeability and contractility simultaneously in murine intestinal segments. To investigate whether permeability and contractility are correlated and influenced by mucosal damage owing to inflammation, BALB/c mice were exposed to a 10% dextran sulphate sodium (DSS) solution for 8 days to induce colitis. The effect of pharmacologically induced smooth muscle relaxation and contraction on permeability was tested in vitro. Regional permeability differences were observed in both control and 10% DSS‐treated mice. Distal colon segments were less permeable to 3H‐mannitol and 14C‐PEG 400 molecules compared with proximal colon and ileum. Intestinal permeability in control vs. 10% DSS mice was not altered, although histologic inflammation score and IFN‐γ pro‐inflammatory cytokine levels were significantly increased in proximal and distal colon. IL1β levels were enhanced in these proximal and distal segments, but not significantly different from controls. Any effect of pharmacologically induced contractility on intestinal permeability could not be observed. In conclusion, intestinal permeability and contractility are not correlated in this model of experimentally induced colitis in mice. Although simultaneous measurement in a physiological set‐up is possible, this method has to be further validated.
Somatostatin does not attenuate intestinal injury in dextran sodium sulphate‐induced subacute colitis
Authors: van Bergeijk J. D. , van Meeteren M. E. , Tak C. J. A. M. , van Dijk A. P. M. , Meijssen M. A. C. , Wilson J. H. P. , Zijlstra F. J.
Published: July 2002

From several in vitro and in vivo studies involvement of som atostatin (SMS) in intestinal inflammation emerge. Acute colitis induced in rats is attenuated by the long‐acting SMS analogue octreotide. We studied the potential beneficial effect of SMS on non‐acute experimental colitis. BALB/c mice received either saline, SMS‐14 (36 or 120 μg daily) or octreotide (3 μg daily) subcutaneously delivered by implant osmotic pumps. A non‐acute colitis was induced by administration of dextran sodium sulphate (DSS) 10% in drinking water during 7 days. DSS evoked a mild, superficial pancolitis, most characterized by mucosal ulceration and submucosal influx of neutrophils. Neither SMS‐14 nor octreotide reduced mucosal inflammatory score or macroscopical disease activity, although reduction of intestinal levels of interleukin1 β (IL‐1 β), IL‐6 and IL‐10 during DSS was augmented both by SMS and octreotide. A slight increase of neutrophil influx was seen during SMS administration in animals not exposed to DSS. In conclusion, SMS or its long‐acting analogue did not reduce intestinal inflammation in non‐acute DSS‐induced colitis. According to the cytokine profile observed, SMS‐14 and octreotide further diminished the reduction of intestinal macrophage and Th2 lymphocyte activity.
Acute induction of interleukin‐6 and biphasic changes of serum complement C3 by carrageenan in mice
Authors: Tateda K. , Matsumoto T. , Yamaguchi K.
Published: July 2002

Carrageenan has been widely used as an irritant to evoke inflamm ation in animals or to selectively deplete m acrophages in vivo. Although precise understanding of carrageenan activity is a prerequisite for the experimental use of this polysaccharide, the effects of this agent on host‐biological systems are still poorly understood. We investigated the effect of carrageenan on serum concentrations of complement C3 and interleukin (IL)‐6, a potent complementinducing factor. Intraperitoneal administration of carrageenan (4 mg) in mice resulted in an initial fall in serum C3 (70% of control, p < 0.05) between 3 and 6 h, but was followed by a significant rise (180% of the control, p < 0.05) at 24 h. Prior to the rise in complement C3, a sharp peak of serum IL‐6 was observed at 6 h after carrageenan treatment. These results indicate potential of carrageenan to enhance host complement systems, which may be associated with, at least in part, an acute induction of IL‐6.
Lymphocytes Apoptosis in Patients with Acute Exacerbation of Asthma
Authors: Hamzaoui Agnès , Hamzaoui Kamel , Salah Habib , Chabbou Abdellatif
Published: July 2002

Asthma is characterized by airway inflammation, which can be now assessed by the analysis of induced sputum . Ten patients with asthma were investigated during acute exacerbation for the quantification of apoptosis, for Bcl‐2 and Fas expression, in induced sputum lymphocytes. They were compared to 12 patients with chronic obstructive pulmonary disease (COPD), and 10 healthy controls. Spontaneous apoptosis was determined by staining nuclei with propidium iodide, and analyzed with a FACScan. Bcl‐2 was measured by Western blotting, and results were obtained by densitometric scanning, done by the gel proanalyser. The investigation of Fas was performed using the streptavidin‐biotin preroxidase‐complex method. Patients with asthma and patients with COPD exhibited a significant increase of cellularity, percentage of neutrophils, eosinophils and lymphocytes when compared to healthy controls. Apoptosis in induced sputum mononuclear cells was found decreased in patients with asthma compared to COPD patients and healthy controls. The quantification of apoptosis was measured after exposure to anticytokine antibodies. Anti‐TNF‐α antibody blocked the apoptosis in both patients groups and healthy controls, suggesting that TNF‐α acted as an inducer of apoptosis. Anti‐IL‐10 blocked apoptosis completely exclusively in patients with asthma. Bcl‐2 expression was found to be increased in induced sputum mononuclear cells from patients with asthma, compared to healthy controls and patients with COPD. Expression of Fas could be detected in patients with asthma, at a lower level than COPD patients and healthy controls. Distinct mechanisms of apoptosis were found in patients with asthma and patients with COPD, characterized by different levels of Bcl‐2 and Fas expression. Induction of apoptosis should be a beneficial process in allergic inflammation traduced in induced sputum mononuclear cells. The apoptosis process is assumed by two different mechanisms in asthma and COPD. Our findings indicated that in asthmatic patients, activated lymphocytes accumulate in the bronchi; because of their prolonged survival that maintains inflammation.
Identification of a Transactivation Motif in the CLN3 Protein
Authors: Leung K. Y. , Greene N. D. E. , Munroe P. B. , Mole S. E.
Published: July 2002

A transactivation motif has been identified in the neurodegenerative disease protein, CLN3. The C‐terminal domain (residues 394‐438) of CLN3 can function as a transcriptional activator when fused to the DNA binding domain, LexA. A series of deletion and substitution constructs have been generated to identify the essential region for transactivation. A similar motif is also present in the POU domain transcription factor, nubbin. However, this domain alone does not activate transcription, allowing further localisation of the critical residues in CLN3 required for activity.
XCTK2: A Kinesin-related Protein That Promotes Mitotic Spindle Assembly in Xenopus laevis Egg Extracts
Authors: Walczak Claire E. , Verma Suzie , Mitchison Timothy J.
Published: July 2002

We used a peptide antibody to a conserved sequence in the motor domain of kinesins to screen a Xenopus ovary cDNA expression library. Among the clones isolated were two that encoded a protein we named XCTK2 for Xenopus COOH-terminal kinesin 2. XCTK2 contains an NH2-terminal globular domain, a central α-helical stalk, and a COOH-terminal motor domain. XCTK2 is similar to CTKs in other organisms and is most homologous to CHO2. Antibodies raised against XCTK2 recognize a 75-kD protein in Xenopus egg extracts that cosediments with microtubules. In Xenopus tissue culture cells, the anti-XCTK2 antibodies stain mitotic spindles as well as a subset of interphase nuclei. To probe the function of XCTK2, we have used an in vitro assay for spindle assembly in Xenopus egg extracts. Addition of antibodies to cytostatic factor- arrested extracts causes a 70% reduction in the percentage of bipolar spindles formed. XCTK2 is not required for maintenance of bipolar spindles, as antibody addition to preformed spindles has no effect. To further evaluate the function of XCTK2, we expressed XCTK2 in insect Sf-9 cells using the baculovirus expression system. When purified (recombinant XCTK2 is added to Xenopus egg extracts at a fivefold excess over endogenous levels) there is a stimulation in both the rate and extent of bipolar spindle formation. XCTK2 exists in a large complex in extracts and can be coimmunoprecipitated with two other proteins from extracts. XCTK2 likely plays an important role in the establishment and structural integrity of mitotic spindles.
A Novel Regulatory Mechanism of Map Kinases Activation and Nuclear Translocation Mediated by Pka and the Ptp-Sl Tyrosine Phosphatase
Authors: Blanco-Aparicio Carmen , Torres Josema , Pulido Rafael
Published: July 2002

Protein tyrosine phosphatase PTP-SL retains mitogen-activated protein (MAP) kinases in the cytoplasm in an inactive form by association through a kinase interaction motif (KIM) and tyrosine dephosphorylation. The related tyrosine phosphatases PTP-SL and STEP were phosphorylated by the cAMP-dependent protein kinase A (PKA). The PKA phosphorylation site on PTP-SL was identified as the Ser231 residue, located within the KIM. Upon phosphorylation of Ser231, PTP-SL binding and tyrosine dephosphorylation of the MAP kinases extracellular signal–regulated kinase (ERK)1/2 and p38α were impaired. Furthermore, treatment of COS-7 cells with PKA activators, or overexpression of the Cα catalytic subunit of PKA, inhibited the cytoplasmic retention of ERK2 and p38α by wild-type PTP-SL, but not by a PTP-SL S231A mutant. These findings support the existence of a novel mechanism by which PKA may regulate the activation and translocation to the nucleus of MAP kinases.
A Novel 14-Kilodalton Protein Interacts with the Mitogen-Activated Protein Kinase Scaffold Mp1 on a Late Endosomal/Lysosomal Compartment
Authors: Wunderlich Winfried , Fialka Irene , Teis David , Alpi Arno , Pfeifer Andrea , Parton Robert G. , Lottspeich Friedrich , Huber Lukas A.
Published: July 2002

We have identified a novel, highly conserved protein of 14 kD copurifying with late endosomes/lysosomes on density gradients. The protein, now termed p14, is peripherally associated with the cytoplasmic face of late endosomes/lysosomes in a variety of different cell types.

In a two-hybrid screen with p14 as a bait, we identified the mitogen-activated protein kinase (MAPK) scaffolding protein MAPK/extracellular signal–regulated kinase (ERK) kinase (MEK) partner 1 (MP1) as an interacting protein. We confirmed the specificity of this interaction in vitro by glutathione S-transferase pull-down assays and by coimmunoprecipitation, cosedimentation on glycerol gradients, and colocalization. Moreover, expression of a plasma membrane–targeted p14 causes mislocalization of coexpressed MP1. In addition, we could reconstitute protein complexes containing the p14–MP1 complex associated with ERK and MEK in vitro.

The interaction between p14 and MP1 suggests a MAPK scaffolding activity localized to the cytoplasmic surface of late endosomes/lysosomes, thereby combining catalytic scaffolding and subcellular compartmentalization as means to modulate MAPK signaling within a cell.
Intracellular Aggregation of Polypeptides with Expanded Polyglutamine Domain Is Stimulated by Stress-Activated Kinase Mekk1
Authors: Meriin Anatoli B. , Mabuchi Katsuhide , Gabai Vladimir L. , Yaglom Julia A. , Kazantsev Alex , Sherman Michael Y.
Published: July 2002

Abnormal proteins, which escape chaperone-mediated refolding or proteasome-dependent degradation, aggregate and form inclusion bodies (IBs). In several neurodegenerative diseases, such IBs can be formed by proteins with expanded polyglutamine (polyQ) domains (e.g., huntingtin). This work studies the regulation of intracellular IB formation using an NH2-terminal fragment of huntingtin with expanded polyQ domain. We demonstrate that the active form of MEKK1, a protein kinase that regulates several stress-activated signaling cascades, stimulates formation of the IBs. This function of MEKK1 requires kinase activity, as the kinase-dead mutant of MEKK1 cannot stimulate this process. Exposure of cells to UV irradiation or cisplatin, both of which activate MEKK1, also augmented the formation of IBs. The polyQ-containing huntingtin fragment exists in cells in two distinct forms: (a) in a discrete soluble complex, and (b) in association with insoluble fraction. MEKK1 strongly stimulated recruitment of polyQ polypeptides into the particulate fraction. Notably, a large portion of the active form of MEKK1 was associated with the insoluble fraction, concentrating in discrete sites, and polyQ-containing IBs always colocalized with them. We suggest that MEKK1 is involved in a process of IB nucleation. MEKK1 also stimulated formation of IBs with two abnormal polypeptides lacking the polyQ domain, indicating that this kinase has a general effect on protein aggregation.
Noncytopathic Clearance of Lymphocytic Choriomeningitis Virus from the Hepatocyte
Authors: Guidotti Luca G. , Borrow Persephone , Brown Amy , McClary Heike , Koch Rick , Chisari Francis  V.
Published: July 2002

We have previously shown that interferon and tumor necrosis factor noncytopathically abolish hepatitis B virus (HBV) replication from the hepatocyte and kidney tubular epithelial cells in vivo. Here we show that a persistent lymphocytic choriomeningitis virus (LCMV) infection is cleared from the hepatocyte noncytopathically when the same cytokines are induced in the liver by antigen-nonspecific stimuli. These results indicate that, like HBV, LCMV is also susceptible to intracellular inactivation by cytokine-induced antiviral mechanisms that are operative in the hepatocyte. In contrast, LCMV is not cleared from intrahepatic nonparenchymal cells or splenocytes, indicating that, unlike the hepatocyte, these cells do not produce the factors required to inactivate LCMV. Antiviral mechanisms like these may have evolved to maintain the functional integrity of vital organs in the face of massive infection.
Methylation-Dependent Gene Silencing Induced by Interleukin 1β via Nitric Oxide Production
Authors: Hmadcha Abdelkrim , Bedoya Francisco J. , Sobrino Francisco , Pintado Elizabeth
Published: July 2002

Interleukin (IL)-1β is a pleiotropic cytokine implicated in a variety of activities, including damage of insulin-producing cells, brain injury, or neuromodulatory responses. Many of these effects are mediated by nitric oxide (NO) produced by the induction of NO synthase (iNOS) expression. We report here that IL-1β provokes a marked repression of genes, such as fragile X mental retardation 1 (FMR1) and hypoxanthine phosphoribosyltransferase (HPRT), having a CpG island in their promoter region. This effect can be fully prevented by iNOS inhibitors and is dependent on DNA methylation. NO donors also cause FMR1 and HPRT gene silencing. NO-induced methylation of FMR1 CpG island can be reverted by demethylating agents which, in turn, produce the recovery of gene expression. The effects of IL-1β and NO appear to be exerted through activation of DNA methyltransferase (DNA MeTase). Although exposure of the cells to NO does not increase DNA MeTase gene expression, the activity of the enzyme selectively increases when NO is applied directly on a nuclear protein extract. These findings reveal a previously unknown effect of IL-1β and NO on gene expression, and demonstrate a novel pathway for gene silencing based on activation of DNA MeTase by NO and acute modification of CpG island methylation.
Atp Regulation of Recombinant Type 3 Inositol 1,4,5-Trisphosphate Receptor Gating
Authors: Mak Don-On Daniel , McBride Sean , Foskett J. Kevin
Published: July 2002

A family of inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) Ca2+ release channels plays a central role in Ca2+ signaling in most cells, but functional correlates of isoform diversity are unclear. Patch-clamp electrophysiology of endogenous type 1 (X-InsP3R-1) and recombinant rat type 3 InsP3R (r-InsP3R-3) channels in the outer membrane of isolated Xenopus oocyte nuclei indicated that enhanced affinity and reduced cooperativity of Ca2+ activation sites of the InsP3-liganded type 3 channel distinguished the two isoforms. Because Ca2+ activation of type 1 channel was the target of regulation by cytoplasmic ATP free acid concentration ([ATP]i), here we studied the effects of [ATP]i on the dependence of r-InsP3R-3 gating on cytoplasmic free Ca2+ concentration ([Ca2+]i). As [ATP]i was increased from 0 to 0.5 mM, maximum r-InsP3R-3 channel open probability (Po) remained unchanged, whereas the half-maximal activating [Ca2+]i and activation Hill coefficient both decreased continuously, from 800 to 77 nM and from 1.6 to 1, respectively, and the half-maximal inhibitory [Ca2+]i was reduced from 115 to 39 μM. These effects were largely due to effects of ATP on the mean closed channel duration. Whereas the r-InsP3R-3 had a substantially higher Po than X-InsP3R-1 in activating [Ca2+]i (<1 μM) and 0.5 mM ATP, the Ca2+ dependencies of channel gating of the two isoforms became remarkably similar in the absence of ATP. Our results suggest that ATP binding is responsible for conferring distinct gating properties on the two InsP3R channel isoforms. Possible molecular models to account for the distinct regulation by ATP of the Ca2+ activation properties of the two channel isoforms and the physiological implications of these results are discussed. Complex regulation by ATP of the types 1 and 3 InsP3R channel activities may enable cells to generate sophisticated patterns of Ca2+ signals with cytoplasmic ATP as one of the second messengers.
Absorbing boundary conditions for electromagnetic wave propagation
Authors: Feng Xiaobing
Published: July 2002

In this paper, the theoretical perfectly absorbing boundary condition on the boundary of a half–space domain is developed for the Maxwell system by considering the system as a whole instead of considering each component of the electromagnetic fields individually. This boundary condition allows any wave motion generated within the domain to pass through the boundary of the domain without generating any reflections back into the interior. By approximating this theoretical boundary condition a class of local absorbing boundary conditions for the Maxwell system can be constructed. Well–posedness in the sense of Kreiss of the Maxwell system with each of these local absorbing boundary conditions is established, and the reflection coefficients are computed as a plane wave strikes the artificial boundary. Numerical experiments are also provided to show the performance of these local absorbing boundary conditions
Metric minimizing surfaces
Authors: Petrunin Anton
Published: July 2002

Consider a two-dimensional surface in an Alexandrov space of curvature bounded above by

k
k

. Assume that this surface does not admit contracting deformations (a particular case of such surfaces is formed by area minimizing surfaces). Then this surface inherits the upper curvature bound, that is, this surface has also curvature bounded above by

k
k

, with respect to the intrinsic metric induced from its ambient space.
An analysis of the Protein Data Bank in search of temporal and global trends.
Authors: Weissig H , Bourne P E
Published: July 2002

MOTIVATION: Biological databases, with their rapidly expanding contents, are indispensable tools in the quest to understand more about biological function. However, a serious user of a database that comprises a large collection of data, collected over a long period, will likely be struck by the inconsistency in reporting individual items of data. This paper takes a critical look at the Protein Data Bank (PDB) to explore the seriousness of the problem in one particular data set and to explore the implications to those actively engaged in comparative analysis of these data. RESULTS: Averaged over the complete corpus, the stereochemical quality of atomic models has, in the past few years, moved towards ideal values. At the same time, there are inconsistencies in how data are reported. Water content is not reported consistently and the percent of data collected when reporting the high-resolution shell varies, detracting from the value of resolution as a yardstick for assessing the quality of a structure. A more detailed analysis of these inconsistencies is hampered by the lack of machine-readable experimental data. To the user of macromolecular structure data, this suggests that structural details beyond the standard quality measures of resolution and R value should be considered when using coordinate sets for further derivation or in inferring biological function. To the curators of the PDB, this suggests the need to capture more of the experimental data associated with the experiment in a way that permits straightforward parsing.
Pattern formation in epithelial development: the vertebrate limb and feather bud spacing
Authors: Wolpert Lewis
Published: July 2002

The ectoderm of the vertebrate limb and feather bud are epithelia that provide good models for epithelial patterning in vertebrate development. At the tip of chick and mouse limb buds is a thickening, the apical ectodermal ridge, which is essential for limb bud outgrowth. The signal from the ridge to the underlying mesoderm involves fibroblast growth factors. The non–ridge ectoderm specifies the dorsoventral pattern of the bud and Wnt7a is a dorsalizing signal. The development of the ridge involves an interaction between dorsal cells that express radical fringe and those that do not. There are striking similarities between the signals and genes involved in patterning the limb ectoderm and the epithelia of theDrosophilaimaginal disc that gives rise to the wing. The spacing of feather buds involves signals from the epidermis to the underlying mesenchyme, which again include Wnt7a and fibroblast growth factors.
Whorl morphogenesis in the dasycladalean algae: the pattern formation viewpoint
Authors: Dumais Jacques , Harrison Lionel G.
Published: July 2002

The dasycladalean algae produce diverse whorled structures, among which the best known are the vegetative and reproductive whorls of Acetabularia acetabulum . In this paper, we review the literature pertaining to the origin of these structures. The question is addressed in terms of the necessary patternforming events and the possible mechanisms involved, an outlook we call the pattern formation viewpoint. The pattern–forming events involved in the morphogenesis of the vegetative and reproductive whorls of Acetabularia have been used to define five and six morphogenetic stages, respectively. We discuss three published mechanisms which account, at least in part, for the pattern–forming events. The mechanisms are mechanical buckling of the cell wall, reaction–diffusion of morphogen molecules along the cell membrane, and mechanochemical interactions between Ca2+ions and the cytoskeleton in the cytosol. The numerous differences between these mechanisms provide experimental grounds to test their validity. To date, the results of these experiments point towards reaction–diffusion as the most likely patterning mechanism. Finally, we consider the evolutionary origin of the vegetative and reproductive whorls and provide mechanistic explanations for some of the major evolutionary advances.
Reverse genetics approach towards understanding pathogenesis of H5N1 Hong Kong influenza A virus infection
Authors: Hatta Masato , Neumann Gabriele , Kawaoka Yoshihiro
Published: July 2002

In 1990, Palese and colleagues established a method (reverse genetics) that allowed one to generate influenza virus containing a gene segment derived from cloned cDNA. Although this method contributed tremendously to our understanding of influenza pathogenesis, the requirement of helper viruses limited its use in many experimental settings. Recently, we and others established systems for the generation of influenza viruses entirely from cloned cDNAs. These systems require only DNA cloning and transfection techniques, and can therefore be easily implemented by laboratories working in the fields of molecular biology and virology. Thus, for the first time, a system is now available that allows highly efficient generation of influenza virus without technical limitations. Using this technology, we generated the same strain of H5N1 influenza viruses that caused an outbreak in Hong Kong in 1997, killing six people.
Probing the surface of a sweet protein: NMR study of MNEI with a paramagnetic probe
Authors: Niccolai Neri , Spadaccini Roberta , Scarselli Maria , Bernini Andrea , Crescenzi Orlando , Spiga Ottavia , Ciutti Arianna , Di Maro Daniela , Bracci Luisa , Dalvit Claudio , Temussi Piero A.
Published: July 2002

The design of safe sweeteners is very important for people who are affected by diabetes, hyperlipemia, and caries and other diseases that are linked to the consumption of sugars. Sweet proteins, which are found in several tropical plants, are many times sweeter than sucrose on a molar basis. A good understanding of their structure–function relationship can complement traditional SAR studies on small molecular weight sweeteners and thus help in the design of safe sweeteners. However, there is virtually no sequence homology and very little structural similarity among known sweet proteins. Studies on mutants of monellin, the best characterized of sweet proteins, proved not decisive in the localization of the main interaction points of monellin with its receptor. Accordingly, we resorted to an unbiased approach to restrict the search of likely areas of interaction on the surface of a typical sweet protein. It has been recently shown that an accurate survey of the surface of proteins by appropriate paramagnetic probes may locate interaction points on protein surface. Here we report the survey of the surface of MNEI, a single chain monellin, by means of a paramagnetic probe, and a direct assessment of bound water based on an application of ePHOGSY, an NMR experiment that is ideally suited to detect interactions of small ligands to a protein. Detailed surface mapping reveals the presence, on the surface of MNEI, of interaction points that include residues previously predicted by ELISA tests and by mutagenesis.
Interior near-field acoustical holography in flight
Authors: Williams Earl G. , Houston Brian H. , Herdic Peter C. , Raveendra S. T. , Gardner Bryce
Published: July 2002

In this paper boundary element methods (BEM) are mated with near-field acoustical holography (NAH) in order to determine the normal velocity over a large area of a fuselage of a turboprop airplane from a measurement of the pressure (hologram) on a concentric surface in the interior of the aircraft. This work represents the first time NAH has been applied in situ, in-flight. The normal fuselage velocity was successfully reconstructed at the blade passage frequency (BPF) of the propeller and its first two harmonics. This reconstructed velocity reveals structure-borne and airborne sound-transmission paths from the engine to the interior space.
Independence of frequency channels in auditory temporal gap detection
Authors: Phillips Dennis P. , Hall Susan E.
Published: July 2002

The ability of listeners to detect a temporal gap in a 1600-Hz-wide noiseband (target) was studied as a function of the absence and presence of concurrent stimulation by a second 1600-Hz-wide noiseband (distractor) with a nonoverlapping spectrum. Gap detection thresholds for single noisebands centered on 1.0, 2.0, 4.0, and 5.0 kHz were in the range from 4 to 6 ms, and were comparable to those described in previous studies. Gap thresholds for the same target noisebands were only modestly improved by the presence of a synchronously gated gap in a second frequency band. Gap thresholds were unaffected by the presence of a continuous distractor that was either proximate or remote from the target frequency band. Gap thresholds for the target noiseband were elevated if the distractor noiseband also contained a gap which “roved” in time in temporal proximity to the target gap. This effect was most marked in inexperienced listeners. Between-channel gap thresholds, obtained using leading and trailing markers that differed in frequency, were high in all listeners, again consistent with previous findings. The data are discussed in terms of the levels of the auditory perceptual processing stream at which the listener can voluntarily access auditory events in distinct frequency channels.
Backscattering of transients by tilted truncated cylindrical shells: Time-frequency identification of ray contributions from measurements
Authors: Morse Scot F. , Marston Philip L.
Published: July 2002

Impulse backscattering measurements by a thick-walled finite cylindrical shell are examined in the time-frequency domain to identify and characterize individual ray contributions from generalized Lamb waves excited on the shell. Previous experiments and analysis in the frequency-aspect angle domain [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)] indicate that large backscattering enhancements occur in the midfrequency region for the shell tilted at large angles. Presently this experimental data is examined in the time-frequency domain for selected angles of incidence. Individual ray contributions are evident and their evolution over aspect angle is discussed. The most prominent contribution is due to the meridional ray of the a0 leaky Lamb wave. This feature distinctly highlights the truncation of the shell and is found over a range of aspect angles spanning 200° for the frequencies examined. Also observed are periodic features corresponding to end-reflected helical waves of the a0−. These scattering features are significantly different from those reported for thin-walled finite cylinders at low frequencies. The present results may be useful for target identification and localization and as a comparison tool for high-frequency computational scattering models.
Why fluid loading has an opposite effect on the velocity of dilatational waves in thin plates and rods
Authors: Hassan Waled , Nagy Peter B.
Published: July 2002

From almost every respect, the lowest-order dilatational waves in thin plates and rods are very similar. Therefore, it is rather intriguing that fluid loading increases the phase velocity of such waves in a plate, but decreases it in a rod. Although this difference can be easily demonstrated by inspection of the well-known exact dispersion equations, the underlying physics remains somewhat obscure. Simple physical models are introduced for thin immersed rods and plates that provide a better insight into the fundamental difference causing the opposite behavior of these otherwise analogous modes of wave propagation. It is shown that the inverse effect of fluid loading is caused by the fact that the radiation impedance exerted by the fluid on plates is purely real while it is dominantly imaginary in the case of thin rods.
A numerical approach to determining the transient response of nonrectangular bars subjected to transverse elastic impact
Authors: Lin Yiching , Lai Wei-Kuang , Lin Kuo-Lung
Published: July 2002

The objectives of the studies presented in this paper are to propose an efficient numerical approach to determining the transient response of nonrectangular bars subjected to transverse elastic impact. It is shown that the response of nonrectangular bars, such as T- and I-beams, subjected to transverse impact is composed of frequencies corresponding to the cross-sectional modes of vibration of the nonrectangular bar. In this study, eigenvalue analyses of plane-strain finite-element models of T- and I-sections were performed first to solve for the cross-sectional mode shapes and the corresponding natural frequencies. Three-dimensional resonant analyses were used to verify the existence of the cross-sectional modes obtained from the eigenvalue analyses. Three-dimensional finite-element models were also used to determine the transient response of T- and I-beams subjected to transverse elastic point impact. Numerical results were verified by experimental studies on a 0.5-m-deep concrete T-beam and a 0.72-m-deep concrete I-beam. Good agreement was obtained between the numerical and experimental results. It is concluded that the proposed numerical models are valid and efficient for determining the transient response of nonrectangular bars subjected to transverse impact.
Acoustic shape sensitivity analysis using the boundary integral equation
Authors: Koo Bon-Ung , Ih Jeong-Guon , Lee Byung-Chai
Published: July 2002

Boundary integral equations are formulated for the shape sensitivity analysis of the acoustic problems. The concept of the material derivative is employed in deriving the sensitivity equations. Since the equation is derived by the direct differentiation of the boundary integrals containing the field values, it is expected that the sensitivity would be computed more effectively and accurately than the conventional finite difference method. In addition, the equation has the potential to be applied to many complex acoustic problems, because the derived equation is regularized by using the integral identity that incorporates the one-dimensional propagating wave and its material derivative. The validity of the formulations is demonstrated through examples having regular shapes such as the three-dimensional pulsating sphere and the one-dimensional duct, for which the analytical solutions are available. As an example for an irregular domain, the two-dimensional model of an automotive interior cavity is dealt with in the view point of the noise level at the passenger’s ear position. The results show that the present method can be an effective tool for the shape optimization in designing the desired sound field. It is noted that the present method permits accurate sensitivities of the acoustic pressure on the boundary as well as at the field points. The present method is thought to be an alternative to the previous finite difference techniques for computing the shape sensitivity using the boundary element method and the formal derivative method using the finite element method.
Dual temporal pitch percepts from acoustic and electric amplitude-modulated pulse trains
Authors: McKay Colette M. , Carlyon Robert P.
Published: July 2002

Two experiments examined the perception of unmodulated and amplitude-modulated pulse trains by normally hearing listeners and cochlear implantees. Four normally hearing subjects listened to acoustic pulse trains, which were band-pass filtered between 3.9 and 5.3 kHz. Four cochlear implantees, all postlinguistically deaf users of the Mini System 22 implant, listened to current pulse trains produced at a single electrode position. In the first experiment, a set of nine loudness-balanced unmodulated stimuli with rates between 60 and 300 Hz were presented in a multidimensional scaling task. The resultant stimulus spaces for both subject groups showed a single dimension associated with the rate of the stimuli. In the second experiment, a set of ten loudness-balanced modulated stimuli was constructed, with carrier rates between 140 and 300 Hz, and modulation rates between 60 and 150 Hz. The modulation rates were integer submultiples of the carrier rates, and each modulation period consisted of one higher-intensity pulse and one or more identical lower-intensity pulses. The modulation depth of each stimulus was adjusted so that its pitch was judged to be higher or lower 50% of the time than that of an unmodulated pulse train having a rate equal to the geometric mean of the carrier and modulation rates. A multidimensional scaling task with these ten stimuli resulted in two-dimensional stimulus spaces, with dimensions corresponding to carrier and modulation rates. A further investigation with one normally hearing subject showed that the perceptual weighting of the two dimensions varied systematically with modulation depth. It was concluded that, when filtered appropriately, acoustic pulse trains can be used to produce percepts in normal listeners that share common features with those experienced by subjects listening through one channel of a cochlear implant, and that the central auditory system can extract two temporal patterns arising from the same cochlear location.
Performance of some linear time-varying systems in control of acoustic feedback
Authors: Nielsen Johan L. , Svensson U. Peter
Published: July 2002

Some linear time-varying (LTV) components used to control feedback in sound systems were tested experimentally in real-time simulators and rooms with and without external reverberation. Gain before instability (GBI) was measured in single channels employing frequency shifting (FS), phase modulation (PM), and delay modulation (DM) implemented on a digital signal processor. FS performed according to the established theory. For PM GBI increased almost monotonically with modulation index β, except for cases with large loop gain irregularities which displayed a reduced GBI for values of β that corresponded to low carrier suppression. Also, GBI was practically independent of the modulation frequency fm already from 0.5 Hz even when this was much lower than the correlation distance of the loop gain transfer function. Rooms with different reverberation times gave different initial (time-invariant) GBI values but these differences decreased by the use of modulation. The GBI increase was larger for cases with external reverberation than for cases without due to increased loop gain irregularity, and the GBI results depended on fm. Since the possible GBI increase is determined by the initial GBI, LTV system performance should be measured in terms of GBI and not GBI increase alone. Robustness increased by equalizing the loop gain before employing LTV components. DM gave little protection for low frequencies but was efficient at high frequencies.
Design of an optimal wave-vector filter for enhancing the resolution of reconstructed source field by near-field acoustical holography (NAH)
Authors: Kim Bong-Ki , Ih Jeong-Guon
Published: July 2002

In near-field acoustical holography using the boundary element method, the reconstructed field often diverges due to the presence of small measurement errors. In order to handle this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the determination of an optimal truncation order is difficult. In this article, an iterative inverse solution technique is suggested in which the mean-square error prediction is used. A statistical estimation of the minimum mean-square error between measured pressures and the model solution is required for yielding the optimal number of iterations. The continuous curve of an optimal wave-vector filter is designed, for suppressing the high-order modes that can produce large reconstruction errors. Experimental results from a baffled radiator reveal that the reconstruction errors can be reduced by this form of regularization, by at least 48% compared to those without any regularization. In comparison to results using the optimal truncation method of regularization, the new scheme is shown to give further reductions of truncation error of between 7% and 39%, for the example in this article.
Unsteady Flow of an Oldroyd Fluid in a Circular Tube
Authors: Etter Irwin , Schowalter W. R.
Published: July 2002

Solutions to the equation of motion have been obtained for a viscoelastic fluid which obeys an Oldroyd three-constant constitutive equation. The solutions apply to a fluid at rest which at zero time is subjected to (1) a step change in pressure gradient or (2) a sinusoidally varying pressure gradient. From these results one can predict the response of the fluid to an arbitrary time-dependent pressure gradient. Curves are presented which show how the flow of a viscoelastic fluid, when subjected to a step change in pressure, can overshoot the final steady-state flow. Amplitude and phase relationships between different variables are presented for a sinusoidally varying pressure gradient. Comparisons are made with available experimental data.
Linear Viscoelastic Response to a Deformation at Constant Rate: Derivation of Physical Properties of a Densely Crosslinked Elastomer
Authors: Smith Thor L.
Published: July 2002

The stress-time response, σ(t), to a constant rate of strain, ε̇, followed by a constant strain is discussed. The Boltzmann superposition principle is used to obtain the stress-relaxation modulus E(t) from the modulus F(t)≡σ(t)/ε(t) that represents the linear viscoelastic response to the ramp function ε(t)=ε̇t. To illustrate the utility of F(t) obtained from only several tests, the stress-time response to a strain rate of 0.25 min−1 was measured on a densely crosslinked elastomer (an epoxy resin whose T0 is 27°C) at 50, 60, and 90°C and at ε⩽0.10. The data in conjunction with the WLF equation yielded: 1) the linear viscoelastic properties, represented by either F(t) or E(t) over five decades of time; 2) the equilibrium (elastic) modulus; and 3) an acceptable value for T0. To show that the experimental results in fact represent linear viscoelastic behavior, stress-relaxation data measured at 50°C immediately after a specimen had been stretched at ε̇=0.25 min−1 to ε=0.10 were converted into E(t) by a derived equation and found to agree with that obtained from F(t). The data along with results from ancillary tests at 10, 20, and 30°C gave the isochronous modulus F(0.015 min) over the rubber-to-glass dispersion zone.
Peripheral Auditory Function in Tanzanian Children Living With HIV With Clinically Normal Hearing
Authors: Niemczak Christopher E. , Ealer Christin , Fellows Abigail , Magohe Albert , Gui Jiang , Rieke Catherine , Nicol Trent , Massawe Enica R. , Kraus Nina , Buckey Jay C.
Published: March 2023

Importance

Despite normal audiometry, adults living with HIV have lower distortion product otoacoustic emissions (DPOAEs) compared with HIV-negative controls, but the degree of these differences in children living with HIV is unknown. If subclinical auditory deficits are present, results could affect developmental outcomes in children living with HIV (CLWH).

Objective

To compare DPOAEs and auditory brainstem responses (ABR) between 2 age- and sex-matched groups of younger children with normal audiometry, 1 infected with HIV and the other uninfected.

Design, Setting, and Participants

Cohort study in an infectious disease center in Dar es Salaam, Tanzania. Participants included 340 Tanzanian children aged 3 to 9 years with clinically normal hearing, type A tympanograms bilaterally, and air-conduction thresholds of 20 dB HL or less from 0.5 to 8 kHz. Participants in the cohort repeated testing approximately every 6 months (approximately 2.2 sessions per participant) for a total of 744 total observations. Data were analyzed from March 2020 to January 2022.

Main Outcomes and Measures

DPOAE amplitudes from 1.5 to 8 kHz using an f2 to f1 ratio of 1.2 and L1/L2 values of 65/55 dB sound pressure level and click-evoked ABR using a slow (21.1/s) and fast (61.1/s) click rate.

Results

A total of 141 CLWH (70 female participants [49.3%]; mean [SD] age, 7.24 [1.67] years) and 199 HIV-negative individuals (99 female participants [49.7%]; mean [SD] age, 7.26 [1.44] years) participated in the study. The groups did not differ significantly in age, static immittance, or air-conduction thresholds. HIV status was independently associated with approximately 1.4 dB (95% CI, −3.28 to 0.30 dB) to 3.8 dB (95% CI, 6.03 to −1.99 dB) lower DPOAE amplitudes at 6 and 8 kHz bilaterally and 0.28 μV (95% CI, 0.01 to 0.33 μV) lower ABR wave V amplitudes in the right ear.

Conclusions and Relevance

Consistent with previous findings in young adults, CLWH had slightly, but reliably, lower DPOAEs and ABR wave V amplitudes than HIV-negative controls. The magnitude of these differences was small, but results suggest an early and consistent association between HIV infection or treatment and outer hair cell and auditory brainstem responses in children as young as 3 years. These subclinical changes suggest tracking both auditory function and development outcomes in CLWH is warranted.
Recommendation for Cannabis Use Disorder Diagnosis in a Context of Cannabis for Therapeutic Purposes
Authors: Chung Tammy , Steinberg Marc L. , Bridgeman Mary Barna
Published: March 2023

This Viewpoint proposes a model of cannabis use disorder diagnosis in the context of cannabis for therapeutic purposes that is based on DSM-5 model of diagnosing substance use disorder in the context of prescribed medication use
Microstructure Evolution and Mechanical Behaviors of P92 Steel Welded Joint with Repetitive Post Tempering
Authors: Wang Yu , Jian Yongxin , Xu Rongbo , Wang Quansheng , Zhang Xiaoming , Dang Wenjing , Huang Zhifu
Published: March 2023

The microstructure evolution and mechanical properties of P92 steel welded joint have been systematically investigated relating to the number of tempering cycles. Martensite laths, M23C6 precipitates, and tiny MX phase have been characterized in P92 base metal (BM). Likewise, the heat‐affected zone (HAZ), fusion zone (FZ), and weld metal (WM) show the similar feature of phase composition to the BM. However, δ‐ferrite patches can be found in FZ. With the increasing number of tempering cycles, the area fraction and average size of M23C6 precipitates gradually increase in HAZ and FZ despite that microstructure has little change. Consequently, the hardness, ultimate tensile strength, and yield strength tend to decrease, while the elongation can be improved in some degree. The reduction in solution strengthening, grain refinement strengthening, and precipitation strengthening is responsible for the strength degeneration of P92 steel welded joint with reduplicative tempering.
Dynamic Stabilization of Metastable States in Triple‐Well Ferroelectric Sn2P2S6
Authors: Neumayer Sabine M. , Bauer Nora , Basun Sergey , Conner Benjamin S. , Susner Michael A. , Lavrentovich Maxim O. , Maksymovych Petro
Published: March 2023

Polarization dynamics in ferroelectric materials is governed by the effective potential energy landscape of the order parameter. The unique aspect of ferroelectrics compared to many other transitions is the possibility of more than two potential wells, leading to complicated energy landscapes with new fundamental and functional properties. Here, direct dynamic evidence is revealed of a triple‐well potential in the metal thiophosphate Sn2P2S6 compound using multivariate scanning probe microscopy combined with theoretical simulations. The key finding is that the metastable zero polarization state can be accessed through a gradual switching process and is stabilized over a broad range of electric fields. Simulations confirm that the observed zero polarization state originates from a kinetic stabilization of the nonpolar state of the triple‐well, as opposed to domain walls. Dynamically, the triple‐well of Sn2P2S6 becomes equivalent to antiferroelectric hysteresis loops. Therefore, this material combines the robust and well‐defined domain structure of a proper ferroelectric with dynamic hysteresis loops present in antiferroelectrics. Moreover, the triple‐well enhances mem‐capacitive effects in Sn2P2S6, which are forbidden for ideal double‐well ferroelectrics. These findings provide a path to tunable electronic elements for beyond binary high‐density computing devices and neuromorphic circuits based on dynamic properties of the triple‐well.