Ideal soliton environment using parametric band gaps

Simultaneous solitary wave solutions for laser propagation in nonlinear parametric media with up to (3 + 1) dimensions are proved to exist. The combination of the large dispersion of a Bragg grating and the strong nonlinearity of chi((2)) optical material results in stable behavior with short interaction distances and low power requirements. The solutions are obtained by using the effective mass approximation to reduce the coupled propagation equations to those describing a dispersive parametric nonlinear waveguide, and are verified by solving the complete set of coupled band-gap equations numerically.

A compact shock-assisted free-piston driver for impulse facilities

A free-piston driver that employs entropy-raising shock processes with diaphragm rupture has been constructed, which promises significant theoretical advantages over isentropic compression. Results from a range of conditions with helium and argon driver gases are reported. Significant performance gains were achieved in some test cases. Heat losses are shown to have a strong effect on driver processes. Measurements compare well with predictions from a quasi-one-dimensional numerical code.

Late Auditory evoked potentials in individuals with tinnitus

Long latency auditory evoked potentials (LLAEP) alterations in individuals with tinnitus are suggestive of dysfunction in the central auditory pathways at a cortical level. Aim: to characterize the LLAEP in individuals with and without tinnitus exposed to occupational noise. Method: Cross-sectional contemporary cohort, prospective study. Sixty subjects exposed to occupational noise, ranging in age from 29 to 50 years underwent LLAEP assessment; 30 of them had tinnitus complaint and 30 did not have tinnitus. Results: we observed significant statistical difference regarding the mean values of latencies of waves N1 (p<0.001), P2 (p=0.002) and P300 (p=0.039) when we compared individuals with and without tinnitus. In individuals with tinnitus we also noticed a greater number of altered results concerning components N1 (60%) and P2 (66.7%), although only component P2 presented significant statistical difference (p=0.010). For the LLAEP, the latency increase was the only type of alteration found (p=1.000). We found a greater association between bilateral tinnitus and bilateral alteration for all components N1(73%), P2(73%) and P300(50%). Conclusion: It is relevant to study LLAEP in individuals with tinnitus exposed to high occupational sound pressure levels.

Stuttering treatment control using P300 event-related potentials

Positron emission tomography studies during speech have indicated a failure to show the normal activation of auditory cortical areas in stuttering individuals. In the present study, P300 event-related potentials were used to investigate possible effects of behavioral treatment on the pattern of signal amplitude and latency between waves. In order to compare variations in P300 measurements, a control group paired by age and gender to the group of stutterers, was included in the study. Findings suggest that the group of stutterers presented a significant decrease in stuttering severity after the fluency treatment program. Regarding P300 measurements, stutterers and their controls presented results within normal limits in all testing situations and no significant statistical variations between pre and post treatment testing. When comparing individual results between the testing situations, stutterers presented a higher average decrease in wave latency for the right ear following treatment. The results are discussed in light of previous P300 event-related potentials and functional imaging studies with stuttering adults. Educational objectives: The reader will learn about and be able to describe the: (1) use of P300 event-related potentials in the study of stuttering; (2) differences between stuttering and non-stuttering adults; and (3) effects of behavioral fluency treatment on cerebral activity in stuttering speakers. (C) 2011 Elsevier Inc. All rights reserved.

Spatiotemporal solitons in multidimensional optical media with a quadratic nonlinearity

We consider solutions to the second-harmonic generation equations in two-and three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stability of the solutions to be predicted. Then, we directly simulate the two-dimensional case, taking the initial configuration as suggested by the variational approximation. We thus demonstrate that spatiotemporal solitons indeed exist and are stable. Furthermore, they are not, in the general case, equivalent to the previously known cylindrical spatial solitons. Direct simulations generate solitons with some internal oscillations. However, these oscillations neither grow nor do they exhibit any significant radiative damping. Numerical solutions of the stationary version of the equations produce the same solitons in their unperturbed form, i.e., without internal oscillations. Strictly stable solitons exist only if the system has anomalous dispersion at both the fundamental harmonic and second harmonic (SH), including the case of zero dispersion at SH. Quasistationary solitons, decaying extremely slowly into radiation, are found in the presence of weak normal dispersion at the second-harmonic frequency.

Use of Acoustic Doppler Sonography to Ascertain the Feasibility of the Pedicled Nasoseptal Flap After Prior Bilateral Sphenoidotomy

Objectives/Hypothesis: Blood supply to the Hadad-Bassagasteguy pedicled nasoseptal flap may be interrupted by surgery of the pterygopalatine fossa, posterior septectomy, or large sphenoidotomies. This would preclude its use for reconstruction of skull base defects after expanded endonasal approaches (EEA). We present a novel method to ascertain the patency of the nasoseptal artery after prior surgery, and consequently the availability of the nasoseptal flap, using acoustic Doppler sonography. Study Design: Retrospective clinical review. Methods: Four patients who underwent EEAs were evaluated intraoperatively with acoustic Doppler sonography. The mucosa that covers the inferior aspect of the rostrum of the sphenoid sinus was scanned with the tip of the probe. Reflection of sound waves representing intravascular blood flow was assessed. Results: In three patients, the artery was identified in at least one side. One remaining patient showed no acoustic signal suggesting loss of the nasoseptal artery bilaterally, therefore necessitating the use of a fat graft for the reconstruction. Conclusions: Acoustic Doppler sonography seems to be a feasible and effective way to ascertain the availability of the nasoseptal artery. It is a relatively inexpensive and simple technique that can be performed by any endoscopic surgeon.

Fetal tricuspid valve Doppler at 11-13 weeks and 6 days: reference values and reproducibility

Objective To determine normal blood flow velocities across the fetal tricuspid valve (TV) at 11-13 weeks and 6 days of gestation and to examine the reproducibility of these measurements. Methods A prospective study involving 166 normal singleton pregnancies examined at 11-13 weeks and 6 days was carried out. Descriptive analysis of E- and A-waves` maximum velocities, E/A ratio, duration of the cardiac cycle (C) and diastole (D) and D/C ratio were calculated. Intraobserver and interobserver agreement analysis was performed in a subgroup of 12 cases. Results Average (+/- SD) flow velocities were: E-wave, 25.0 (+/- 4.6) cm/s; A-wave. 42.9 (+/- 5.9) cm/s; E/A, 0.58 (+/- 0.07); cardiac cycle, 390 (+/- 21.1) ms; diastole, 147 (+/- 18) ms and D/C, 0.38 (+/- 0.04). Significant correlation was observed between all parameters (except A-wave) and gestational age but not with nuchal translucency (NT). Intraclass correlation coefficients (interobserver, intraobsever examiner I and intraobserver examiner 2) were: E-wave, 0.53, 0.53 and 0.64; A-wave, 0.45, 0.46 and 0.49; cardiac cycle, 0.70, 0.79 and 0.84 and diastole, 0.63, 0.85 and 0.82, respectively. Conclusions The present study establishes normal Doppler parameters for blood flow across the TV at 11 - 13 weeks and 6 days and demonstrates that these parameters do not correlate with NT measurement and have good/moderate reproducibility. Copyright (C) 2010 John Wiley & Sons, Ltd.

Influence of gender on the vestibular evoked myogenic potential

There is no consensus on the relevance of factors that influence gender differences in the behavior of muscles. Some studies have reported a relationship between muscle tension and amplitude of the vestibular evoked myogenic potential; others, that results depend on which muscles are studied or on how much load is applied. Aims: This study aims to compare vestibular evoked myogenic potential parameters between genders in young individuals. Methods: Eighty young adults were selected - 40 men and 40 women. Stimuli were averaged tone-bursts at 500 Hz, 90 dBHL intensity, and a 10-1000 Hz bandpass filter with amplification of 10-25 microvolts per division. The recordings were made in 80 ms windows. Study type: An experimental and prospective study. Results: No significant gender differences were found in wave latency - p = 0.19 and p = 0.50 for waves P13 and N23, respectively. No differences were found in amplitude values - p = 0.28 p = 0.40 for waves P13 and N23, respectively. Conclusion: There were no gender differences in latency and amplitude factors; the sternocleidomastoid muscle strain was monitored during the examination.

Temporal relationship between the auditory brainstem response and focal responses of auditory nerve root and cochlear nucleus during development in the tammar wallaby (Macropus eugenii)

Thirty-two pouch-young tammar wallabies were used to discover the generators of the auditory brainstem response (ABR) during development by the use of simultaneous ABR and focal brainstem recordings. A click response from the auditory nerve root (ANR) in the wallaby was recorded from postnatal day (PND) 101, when no central auditory station was functional, and coincided with the ABR, a simple positive wave. The response of the cochlear nucleus (CN) was detected from PND 110, when the ABR had developed 1 positive and 1 negative peak. The dominant component of the focal ANR response, the N-1 wave, coincided with the first half of the ABR P wave, and that of the focal CN response, the N-1 wave, coincided with the later two thirds. In older animals, the ANR response coincided with the ABR's N-1, wave, while the CN response coincided with the ABR's P-2, N-2 and P-3 waves, with its contribution to the ABR P-2 dominant. The protracted development of the marsupial auditory system which facilitated these correlations makes the tammar wallaby a particularly suitable model. Copyright (C) 2001 S. Karger AG, Basel.

Functional development of the inferior colliculus (IQ and its relationship with the auditory brainstem response (ABR) in the tammar wallaby (Macropus eugenii)

To discover the developmental relationship between the auditory brainstem response (ABR) and the focal inferior colliculus (IC) response, 32 young tammar wallabies were used, by the application of simultaneous ABR and focal brainstem recordings, in response to acoustic clicks and tone bursts of seven frequencies. The ic or the tammar wallaby undergoes a rapid functional development from postnatal day (PND) 114 to 160. The earliest (PND 114) auditory evoked response was recorded from the rostral IC. With development, more caudal parts of the IC became functional until age about PND 127, when all parts of the IC were responsive to sound. Along a dorsoventral direction, the duration of the IC response decreased, the peak latency shortened, while the amplitude increased, reaching a maximum value at the central IC, then decreased. After PND 160, the best frequency (BF) of the ventral IC was the highest, with values between 12.5 and 16 kHz, the BF of the dorsal IC was the lowest, varying between 3.2 and 6.4 kHz, while the BF of the central IC was between 6.4 and 12.5 kHz. Between PND 114 and 125, the IC response did not have temporal correlation with the ABR. Between PND 140 and 160, only the early components of the responses from the ventral and central IC correlated with the P4 waves of the ABR. After PND 160, responses recorded from different depths of the IC had a temporal correlation with the ABR. (C) 2001 Published by Elsevier Science B.V.

Parametric signal regeneration

We present an ultra-high bandwidth all-optical digital signal regeneration device concept utilising non-degenerate parametric interaction in a one-dimensional waveguide. Performance is analysed in terms of re-amplification, re-timing, and re-shaping (including centre frequency correction) of time domain multiplexed signals. Bandwidths of 10-100 THz are achievable. (C) 2001 Published by Elsevier Science B.V.

Associations involving delays (particularly long delays) between certain weather parameters and geomagnetic activity

Four sunspot-minimum periods (1963-1966, 1971-1977, 1983-1987 and 1992-1997) have been examined for the results which are presented. Using several different weather parameters, tropospheric gravity waves, enhanced cold fronts and two rainfall data sets in Eastern Australia, associations at reasonably high levels of significance have been found with enhanced geomagnetic activity (EGA). Statistically this EGA involved either short delays of several days or long delays of about 20 days. The geomagnetic parameters used were (a) the AE index (b) the hourly H component for a number of stations and (c) the daily K-P-sum value. The K-P-sum analyses have shown that the EGA associated with the delays form part of four or five cycles of recurrent geomagnetic activity for 27-day periodicities. Furthermore statistically two recurrent cycles are found to exist concurrently, one apparently related to the short delays and the other to the long delays. Periodicities of 13.5 days are created because the two sets are displaced from each other by approximately this interval. A brief reference is made to the 13.5 periodicity known to exist for geomagnetic activity and the evidence in the literature for active regions on the sun to be displaced by 180 degrees of solar longitude.

Quasimode theory of quantum optical processes in photonic band gap materials

This paper deals with atomic systems coupled to a structured reservoir of quantum EM field modes, with particular relevance to atoms interacting with the field in photonic band gap materials. The case of high Q cavities has been treated elsewhere using Fano diagonalization based on a quasimode approach, showing that the cavity quasimodes are responsible for pseudomodes introduced to treat non-Markovian behaviour. The paper considers a simple model of a photonic band gap case, where the spatially dependent permittivity consists of a constant term plus a small spatially periodic term that leads to a narrow band gap in the spectrum of mode frequencies. Most treatments of photonic band gap materials are based on the true modes, obtained numerically by solving the Helmholtz equation for the actual spatially periodic permittivity. Here the field modes are first treated in terms of a simpler quasimode approach, in which the quasimodes are plane waves associated with the constant permittivity term. Couplings between the quasimodes occur owing to the small periodic term in the permittivity, with selection rules for the coupled modes being related to the reciprocal lattice vectors. This produces a field Hamiltonian in quasimode form. A matrix diagonalization method may be applied to relate true mode annihilation operators to those for quasimodes. The atomic transitions are coupled to all the quasimodes, and the true mode atom-EM field coupling constants (one-photon Rabi frequencies) are related to those for the quasimodes and also expressions are obtained for the true mode density. The results for the one-photon Rabi frequencies differ from those assumed in other work. Expressions for atomic decay rates are obtained using the Fermi Golden rule, although these are valid only well away from the band gaps.

Recent work on gaseous detonations

The paper reviews recent progress in the field of gaseous detonations, with sections on shock diffraction and reflection, the transition to detonation, hybrid, spherically-imploding, and galloping and stuttering fronts, their structure, their transmission and quenching by additives, the critical energy for initiation and detonation of more unusual fuels. The final section points out areas where our understanding is still far from being complete and contains some suggestions of ways in which progress might be made.

Determinants of tissue Doppler measures of regional diastolic function during dobutamine stress echocardiography

Background Diastolic dysfunction induced by ischemia may alter transmitral blood flow, but this reflects global ventricular function, and pseudonormalization may occur with increased preload. Tissue Doppler may assess regional diastolic function and is relatively load-independent, but limited data exist regarding its application to stress testing. We sought to examine the stress response of regional diastolic parameters to dobutomine echocardiography (DbE). Methods Sixty-three patients underwent study with DbE: 20 with low probability of coronary artery disease (CAD) and 43 with CAD who underwent angiography. A standard DbE protocol was used, and segments were categorized as ischemic, scar, or normal. Color tissue Doppler was acquired at baseline and peak stress, and waveforms in the basal and mid segments were used to measure early filling (Em), late filling (Am), and E deceleration time. Significant CAD was defined by stenoses >50% vessel diameter. Results Diastolic parameters had limited feasibility because of merging of Em and Am waves at high heart rates and limited reproducibility. Nonetheless, compared with normal segments, segments subtended with significant stenoses showed a lower Em velocity at rest (6.2 +/- 2.6 cm/s vs 4.8 +/- 2.2 cm/s, P < .0001) and peak (7.5 +/- 4.2 cm/s vs 5.1 +/- 3.6 cm/s, P < .0001), Abnormal segments also showed a shorter E deceleration time (51 +/- 27 ms vs 41 +/- 27 ms, P = .0001) at base and peak. No changes were documented in Am. The same pattern was seen with segments identified as ischemic with wall motion score. However, in the absence of ischemia, segments of patients with left ventricular hypertrophy showed a lower Em velocity, with blunted Em responses to stress. Conclusion Regional diastolic function is sensitive to ischemia. However, a number of practical limitations limit the applicability of diastolic parameters for the quantification of stress echocardiography.