Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Notch”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed2002

Low-frequency reflection characteristics of the s0 lamb wave from a rectangular notch in a plate.

An analysis of the reflection of the fundamental Lamb mode s0 from surface-breaking rectangular notches in isotropic plates is presented. The results are obtained from finite element time domain simulations together with experimental measurements. Very good agreement is found between the simulations and the measurements. Results are shown for a range of notch widths and depths, including the special case of a crack, defined as a zero-width notch. An interference phenomenon is identified which explains the periodic nature of the reflection coefficient when plotted as a function of notch width. Finally, an analysis using the S-parameter approach and both low and high frequency asymptotic analyses yields physical explanations of the nature of the reflection behavior from the cracks. It is found that the low frequency (quasistatic) approximation may be used accurately for cracks up to about a quarter of the plate thickness, provided that the quasistatic crack-opening function is chosen such that bending of the plate is omitted. At higher frequencies and depths the functions tend towards the high frequency (ray theory) predictions but these are never accurate models within the nondispersive frequency range of the s0 mode.

Humans↗
PubMed2003

The reflection of the fundamental torsional mode from cracks and notches in pipes.

A quantitative study of the reflection of the T(0,1) mode from defects in pipes in the frequency range 10-300 kHz has been carried out, finite element predictions being validated by experiments on selected cases. Both cracklike defects with zero axial extent and notches with varying axial extents have been considered. The results show that the reflection coefficient from axisymmetric cracks increases monotonically with depth at all frequencies and increases with frequency at any given depth. In the frequency range of interest there is no mode conversion at axisymmetric defects. With nonaxisymmetric cracks, the reflection coefficient is a roughly linear function of the circumferential extent of the defect at relatively high frequencies, the reflection coefficient at low circumferential extents falling below the linear prediction at lower frequencies. With nonaxisymmetric defects, mode conversion to the F(1,2) mode is generally seen, and at lower frequencies the F(1,3) mode is also produced. The depth and circumferential extent are the parameters controlling the reflection from cracks; when notches having finite axial extent, rather than cracks, are considered, interference between the reflections from the start and the end of the notch causes a periodic variation of the reflection coefficient as a function of the axial extent of the notch. The results have been explained in terms of the wave-number-defect size product, ka. Low frequency scattering behavior is seen when ka < 0.1, high frequency scattering characteristics being seen when ka > 1.

Journal Article↗
PubMed2004

The temporal effect with notched-noise maskers: analysis in terms of input-output functions.

This study examines whether a temporal masking effect may be consistent with a decrease in gain at the masker frequency during the course of the masker. Threshold level of a long-duration notched-noise masker needed to mask a 1- or 4-kHz signal was measured for three conditions: a short-duration signal with a short delay or a long delay from masker onset, and a long-duration signal. The difference between threshold for the long-delay signal and the short-delay signal was defined as the temporal effect. The size of the temporal effect depended on signal frequency, signal level, and masker notch width. Filters estimated from the data had narrower bandwidths for the long-delay condition than for the short-delay condition or the long-duration condition, which seems inconsistent with the hypothesis of a decrease in gain. However, modeling of the data in terms of basilar-membrane input-output functions is consistent with a decrease in gain in the masker frequency region during the course of the masker. For a notch width of 0.0 the results are consistent with a decrease in gain at the signal frequency. For a relative notch width of 0.4, the decrease in gain at the masker frequency may cause a decrease in the suppression of the signal. This decrease in suppression could explain the decrease in filter bandwidth with signal delay.

Adult↗
PubMed2006

Effect of modulation maskers on the detection of second-order amplitude modulation with and without notched noise.

The mechanisms underlying the detection of second-order amplitude modulation (AM) were explored. The detectability of second-order AM (fixed depth for each subject) was measured for first- and second-order modulation rates of 16 and 2 Hz, respectively (slow-rate pair), and 50 and 10 Hz, respectively (fast-rate pair), with no masker, a low-band modulation masker (centered at 2 or 10 Hz), and a high-band modulation masker (centered at 16 or 50 Hz). This was done in the absence and presence of an audio-frequency notched noise centered at the carrier frequency of 4000 Hz. Both modulation maskers were "low-noise" noises, to prevent overmodulation. In the absence of notched noise, both modulation maskers impaired performance for the slow-rate pair, but only the low-band masker impaired performance for the fast-rate pair. When notched noise was present, the low-band masker had no significant effect for either rate pair and the high-band masker had an effect only for the slow-rate pair. These results suggest that second-order AM detection is mediated both by an envelope distortion component at the second-order rate and by slow fluctuations in the output of a modulation filter tuned to the first-order rate. When notched noise is present, the distortion component plays little role.

Adult↗
PubMed2006

Internal wave effects on the ambient noise notch in the East China Sea: model/data comparison.

The vertical directivity pattern of the ambient noise field observed in shallow water is typically anisotropic with a trough in the horizontal. This trough, often called the ambient noise notch, develops because downward refraction steepens all rays emanating from near the sea surface. Variability in the environment has the potential to redistribute the noise into shallower angles and thereby fill the notch. In the present work, a model for the width and depth of the ambient noise notch is developed. Transport theory for acoustic propagation is combined with a shallow water internal wave model to predict the average output of a beamformer. Ambient noise data from the East China Sea are analyzed in the 1-to-5-kHz band. Good agreement between the model and the data for both the width and depth of the ambient noise notch is obtained at multiple frequencies, suggesting that internal wave effects are significant.

Acoustics↗
PubMed1983

Monaural and binaural auditory frequency resolution measured using bandlimited noise and notched-noise masking.

Several studies using bandlimited masking noise have indicated that NOSO frequency resolution is better than that for NOS pi. The present study examined NOSO and NOS pi frequency resolution with two different masking methods: bandlimited noise and notched noise. Noise spectrum levels of 10, 30, and 50 dB/Hz were used. Thresholds were determined for a 500-Hz signal, using a three-alternative forced-choice adaptive procedure, as a function of masker bandwidth and notchwidth. For NOSO presentation, 3-dB down points were comparable for the notched-noise and bandlimiting methods. For NOS pi presentation, 3-dB down points were generally greater for the bandlimiting method than the notched noise method. Furthermore, for NOS pi presentation, the 3-dB down estimate increased as noise level increased for the bandlimiting method, but stayed constant for the notched-noise method. It is suggested that the two masking methods measured different aspects of binaural processing.

Acoustic Stimulation↗
PubMed1992

The effects of notched noise on intensity discrimination under forward masking.

Zeng et al. [Hear. Res. 55, 223-230 (1991)] reported that at moderate levels there is an increase in the intensity jnd for 25-ms sinusoidal pedestals presented 100 ms after an intense narrow-band noise. They suggested that this effect is related to the finding that low spontaneous rate (SR) auditory-nerve neurons take a considerable time to recover from adaptation [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215-222 (1991)]: 100 ms after the noise, the low-SR neurons still have elevated thresholds. Therefore, the intensity of a pedestal falling between the saturation level of the high-SR neurons and the elevated threshold of the low-SR neurons will be poorly represented in neutral firing rates, and the jnd will be high. A problem with this interpretation is that subjects may listen "off frequency." Theoretically, it should always be possible to choose a frequency channel for which the pedestal level is within the dynamic range of the high-SR neurons. In the present study, the experiment of Zeng et al. was replicated but with the pedestal presented in the temporal center of a notched noise to prevent off-frequency listening. Surprisingly, the notched noise substantially decreased the jnd at mid levels, removing or severely reducing the mid-level jnd elevation. This was true for pedestal frequencies of 1 and 6 kHz. It was also found that even if the notched noise was terminated before pedestal onset the jnd elevation was reduced. This suggests that the effect of the notched noise is not due to suppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The development of frequency resolution in humans as revealed by the auditory brain-stem response recorded with notched-noise masking.

Studies of tuning in infants have reported that auditory brain-stem response (ABR) tuning curves generated using low-frequency probes are adultlike by 3 months of age while high-frequency tuning curves remain immature [Folsom and Wynne, J. Acoust. Soc. Am. 81, 412-417 (1987)]. Behavioral studies have similarly reported adultlike low-frequency psychoacoustic tuning curves by 3 months with high-frequency tuning curves immature until approximately 6 months of age [L. Olsho, Infant Behav. Dev. 8, 371-384 (1985); Spetner and Olsho, Child Dev. 61, 632-652 (1990); Schneider et al., J. Exp. Psych.: Human Percept. Perform. 16, 642-652 (1990)]. Prior to this experiment, there have been no ABR studies of the development of frequency resolution for infants older than 3 months. In this study, notched-noise tuning functions were constructed from wave-V amplitude data for 3-month-old, 6-month-old, and adult subjects. Tone-pip stimuli at 1000, 4000, and 8000 Hz (50 dB nHL) were presented simultaneously with notched-noise masking centered at frequencies related to the tone-pip frequency (1/3-oct intervals above and below the probe frequency). By plotting wave-V amplitude across notched-noise center frequency, isointensity tuning functions were generated for the three subject groups at the three probe frequencies. Auditory filter width (Q) and slope (dB/oct) were measured from each notched-noise tuning function in order to qualify degree of tuning. Consistent with previous studies, results showed that 3-month-old infants do not have adultlike tuning for high-frequency stimulation (8000 Hz). In contrast, by 6 months of age, tuning-function width (Q) is adultlike for both high- and low-frequency probes. These results, combined with previously reported evidence that the human cochlea is fully tuned at birth [Abdala et al., submitted to Hear. Res. (1995); Bargones and Burns, J. Acoust. Soc. Am. 83, 1809-1816 (1988)], suggest that immaturities in the auditory-neural system contribute to the broad high-frequency tuning consistently observed in 3-month-old human infants.

Adolescent↗
PubMed1998

Beneficial effects of notched noise on intensity discrimination in the region of the "severe departure".

Intensity discrimination for a 6-kHz sinusoidal pedestal was measured in quiet and in the presence of a noise background. In the first experiment, the level of a 30-ms pedestal was fixed at 45 dB SPL and presented in the temporal and spectral center of a 110-ms notched noise. For a noise spectrum level of between 0 and 15 dB the noise produced a substantial reduction in the Weber fraction, i.e., an improvement in detectability, compared to the condition without the noise. The second experiment showed that, unlike the situation with notched noise, narrow-noise produced no performance improvement, suggesting that the effect is dependent on noise frequency components outside the critical band of the pedestal. The third experiment showed that the improvement also occurred for a 6-ms pedestal presented in a 10-ms gap between two bursts of notched noise. The experiment rules out an explanation for the effect of the noise in terms of suppression on the basilar membrane. Finally, the effect was shown to decrease as the gap between the noise bursts was increased, in a manner at least broadly consistent with the decay of the temporal excitation pattern. It is suggested that the improvement in intensity discrimination in notched noise is due to an across-frequency comparison mechanism similar to "profile analysis," perhaps operating on a temporally smoothed central representation of the stimulus.

Auditory Perception↗
PubMed1990

Xotch, the Xenopus homolog of Drosophila notch.

During the development of a vertebrate embryo, cell fate is determined by inductive signals passing between neighboring tissues. Such determinative interactions have been difficult to characterize fully without knowledge of the molecular mechanisms involved. Mutations of Drosophila and the nematode Caenorhabditis elegans have been isolated that define a family of related gene products involved in similar types of cellular inductions. One of these genes, the Notch gene from Drosophila, is involved with cell fate choices in the neurogenic region of the blastoderm, in the developing nervous system, and in the eye-antennal imaginal disc. Complementary DNA clones were isolated from Xenopus embryos with Notch DNA in order to investigate whether cell-cell interactions in vertebrate embryos also depend on Notch-like molecules. This approach identified a Xenopus molecule, Xotch, which is remarkably similar to Drosophila Notch in both structure and developmental expression.

Amino Acid Sequence↗
PubMed1998

NF-kappaB2 is a putative target gene of activated Notch-1 via RBP-Jkappa.

NF-kappaB2 (p100/p52), a member of the NF-kappaB/Rel family of transcription factors, is involved in the regulation of a variety of genes important for immune function. Previously, we have shown that the NF-kappaB2 gene is regulated in a positive and a negative manner. Two kappaB elements within the NF-kappaB2 promoter mediate tumor necrosis factor alpha-inducible transactivation. In addition, we have shown that there exists a transcriptional repression in the absence of NF-kappaB. To identify a DNA binding activity responsible for this transcriptional repression, we have partially purified a nuclear complex, named Rep-kappaB. Here we further analyze this putative repressive binding activity. Detailed examination of Rep-kappaB-DNA interaction revealed the sequence requirements for binding to be almost identical to those of recombination signal binding protein Jkappa (RBP-Jkappa), the mammalian homolog of the protein encoded by Drosophila suppressor of hairless [Su(H)]. In addition, in electromobility shift assays, Rep-kappaB binding activity is recognized by an antibody directed against RBP-Jkappa. By performing transient-transfection assays, we show that human RBP-Jkappa represses basal as well as RelA (p65)-stimulated NF-kappaB2 promoter activity. Studies in Drosophila melanogaster have shown that Su(H) is implicated in the Notch signaling pathway regulating cell fate decisions. In transient-transfection assays we show that truncated Notch-1 strongly induces NF-kappaB2 promoter activity. In summary, our data clearly demonstrate that Rep-kappaB is closely related or identical to RBP-Jkappa. RBP-Jkappa is a strong transcriptional repressor of NF-kappaB2. Moreover, this repression can be overcome by activated Notch-1, suggesting that NF-kappaB2 is a novel putative Notch target gene.

DNA↗
PubMed1986

Sequence of the notch locus of Drosophila melanogaster: relationship of the encoded protein to mammalian clotting and growth factors.

The Notch locus is essential for proper differentiation of the ectoderm in Drosophila melanogaster. Notch corresponds to a 37-kilobase transcription unit that codes for a major 10.4-kilobase polyadenylated RNA. The DNA sequence of this transcription unit is presented, except for portions of the two largest intervening sequences. DNA sequences also were obtained from three Notch cDNA clones, allowing the 5' and 3' ends of the gene to be mapped, and the structures and locations of nine RNA coding regions to be determined. The major Notch transcript encodes a protein of 2,703 amino acids. The protein is probably associated with cell surfaces and carries an extracellular domain composed of 36 cysteine-rich repeating units, each of about 38 amino acids. The gene appears to have evolved by repeated tandem duplications of the DNA coding for the 38-amino-acid-long protein segments, followed by insertion of intervening sequences. These repeating protein segments are quite homologous to portions of mammalian clotting factors IX and X and to the product of the Caenorhabditis elegans developmental gene lin-12. They are also similar to mammalian growth hormones, typified by epidermal growth factor.

Amino Acid Sequence↗
PubMed2001

Shape of the intercondylar notch of the human femur: a comparison of osteoarthritic and non-osteoarthritic bones from a skeletal sample.

OBJECTIVES: To compare objectively the shape of the intercondylar notch in human osteoarthritic and non-osteoarthritic femora. METHODS: A sample of 96 human femora from a large skeletal population were selected for study. These femora included subjects with evidence of late stage osteoarthritis (that is, with eburnation present) and subjects with no such evidence. The distal end of the femur, viewed axially, was recorded with a video camera, and digitised computer images were produced. The outline of the intercondylar notch was extracted and represented mathematically as two functions. A functional principal components analysis was used to identify important modes of shape variation. These variations in shape were compared between eburnated and non-eburnated femora. RESULTS: A statistically significant difference in the shape of the intercondylar notch was found between the two groups. The difference related mostly to the shape of the edge of the medial condyle: in the non-osteoarthritic group this tended to exhibit a concavity; in the osteoarthritic group it tended to be straight. CONCLUSIONS: This observed difference may be a predisposing factor to the development of osteoarthritis. The morphology of the intercondylar notch is related to the functioning of and possible damage to the cruciate ligaments, and damage to the cruciate ligaments is a known risk factor for osteoarthritis. Alternatively, this difference may be due to bony remodelling secondary to the onset of osteoarthritis, perhaps in response to altered biomechanics.

Adult↗
PubMedDate not supplied

Are 'notched' uterine arterial waveforms of prognostic value for hypertensive and growth disorders of pregnancy?

In a case-control controlled study of 86 women identified as having bilaterally 'notched' uterine arterial waveform patterns at 18 weeks, the presence of bilateral 'notched' uterine arterial waveforms at that time was associated with the subsequent development of hypertension and small-for-gestational-age infants, but the predictive value was poor. For those women in whom the bilateral uterine 'notches' were observed to persist to 24 weeks, the relative risk of developing proteinuric hypertension increased 14 times, and in these women the positive predictive value for the subsequent development of hypertension increased to 58.6% when compared with their matched controls. The identification of women with persistent bilateral uterine 'notches' provides a means of identifying women at significant risk of hypertensive and growth disorders at a stage when therapeutic intervention aimed at limiting the severity of the disease and its associated complications could be commenced.

Arteries↗
PubMedDate not supplied

The natural history of the intercondylar notch after notchplasty.

Ten patients who underwent anterior cruciate ligament reconstruction by one surgeon using autologous patellar tendon grafts were evaluated. A standardized technique of performing a notchplasty was done to remove at least 5 mm of bone at the anterior outlet of the intercondylar notch. Computed tomography scans were done preoperatively, within 1 week postoperatively, and after 1 year of follow-up. There were no statistically significant differences in the measured dimensions of the intercondylar notch between 1 week and 1 year postoperatively. While previous investigations have evaluated the relationship between intercondylar notch dimensions and risk of anterior cruciate ligament injury, we believe this is the first statistical study that addresses the natural history of the intercondylar notch in humans after bone resection. We believe that the data reported here may enhance our understanding and treatment of patients who have undergone previously failed anterior cruciate ligament reconstructions.

Adolescent↗
PubMed2006

Assessment of a bovine viral diarrhea virus antigen capture ELISA and a microtiter virus isolation ELISA using pooled ear notch and serum samples.

To reduce the cost of whole herd screening for bovine viral diarrhea virus persistently infected animals, the sensitivity and specificity of an antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) and a microtiter virus isolation ELISA using saline from ear notch samples or pooled serum was determined. Pooled saline from ear notch samples, assayed by AC-ELISA, gave a sensitivity and specificity of 98% and 94%, respectively, for pools containing 2 samples and 72% and 100%, respectively, for pools of 5. The sensitivity of pooled ear notch or serum samples for bovine viral diarrhea virus detection by microtiter virus isolation (sensitivity < 5%) or serum samples for detection by AC-ELISA (sensitivity < 15%) is too low to be used for whole herd screening. Pooling saline from ear notch samples from 2 animals tested by AC-ELISA, however, could provide a less expensive, reliable method for whole herd screening for bovine viral diarrhea virus.

Animals↗
PubMed2005

Dose-dependent effects of the Notch ligand Delta1 on ex vivo differentiation and in vivo marrow repopulating ability of cord blood cells.

Although significant advances have been made over the last decade with respect to our understanding of stem cell biology, progress has been limited in the development of successful techniques for clinically significant ex vivo expansion of hematopoietic stem and progenitor cells. We here describe the effect of Notch ligand density on induction of Notch signaling and subsequent cell fate of human CD34+CD38- cord blood progenitors. Lower densities of Delta1(ext-IgG) enhanced the generation of CD34+ cells as well as CD14+ and CD7+ cells, consistent with early myeloid and lymphoid differentiation, respectively. However, culture with increased amounts of Delta1(ext-IgG) induced apoptosis of CD34+ precursors resulting in decreased cell numbers, without affecting generation of CD7+ cells. RNA interference studies revealed that the promotion of lymphoid differentiation was primarily mediated by Delta1 activation of Notch1. Furthermore, enhanced generation of NOD/SCID repopulating cells was seen following culture with lower but not higher densities of ligand. These studies indicate critical, quantitative aspects of Notch signaling in affecting hematopoietic precursor cell-fate outcomes and suggest that density of Notch ligands in different organ systems may be an important determinant in regulating cell-fate outcomes. Moreover, these findings contribute to the development of methodology for manipulation of hematopoietic precursors for therapeutic purposes.

Cell Differentiation↗
PubMed1995

Hemangiopericytoma of the sciatic notch presenting as sciatica in a young healthy man: case report.

A case of hemangiopericytoma of the sciatic notch presenting with sciatica in a healthy 33-year-old man is presented. Tumors of the sciatic notch are exceedingly rare, and few data pertaining to the entity are found in the literature. A few series have been published on neurogenic tumors of the sciatic nerve, and one series of hemangiopericytomas mentions a case in which the sciatic nerve in the thigh is involved with tumor. To our knowledge, this is the first case in the literature detailing a hemangiopericytoma spanning the sciatic notch. Hemangiopericytomas are well known to neurosurgeons as durally based lesions and have been categorized as a subtype of meningioma. However, hemangiopericytomas are vascular sarcomas that most commonly occur in the pelvis and thigh. A brief discussion of the symptoms of sciatic notch lesions and hemangiopericytomas is included.

Adult↗