Spatio-temporal and spatiospectral metrology of terahertz broadband uniformly topologically charged vortex beams.

A comprehensive characterization of the diffraction properties of terahertz (THz) pulsed broadband vortex beams consisting of several electromagnetic field oscillations requires state-of-the-art techniques for studying the evolution of a wavefront as it propagates. For this purpose, we have applied the capabilities offered by THz pulse time domain holography. Accurate metrological study of pulsed single-period THz field propagation allowed us to reveal the spatio-temporal and spatiospectral couplings in broadband uniformly topologically charged vortex beams. Here, we reveal dynamics of such beam propagation in a free space as well as in the experiment with edge diffraction with 50% blocking of the beam focal waist. In this study, we compare the dynamics of freely propagating and edge-diffracted THz vortex. Despite the fact that in the amplitude representation one can observe the emergence of strong asymmetry, analysis of the spectral trajectory of the singular point at some distance from the obstacle and the visualization of phase distribution for individual spectral components testify to the conservation of transverse energy circulation. Similar to the edge diffraction of monochromatic optical vortices, it can be interpreted as self-reconstruction of vortex properties. The given term has not previously been used for the case of pulsed broadband THz beams, to the best of our knowledge.

SHORT DURATION IMMOBILIZATION OF ATLANTIC WALRUS ( ODOBENUS ROSMARUS ROSMARUS) WITH ETORPHINE, AND REVERSAL WITH NALTREXONE.

Forty adult, male Atlantic walruses ( Odobenus rosmarus rosmarus) were successfully immobilized for the attachment of global positioning system loggers on their tusks and collection of various biological samples. A standard dose of 7.8 mg etorphine was used for each animal, regardless of body size. All animals were reversed with an iv or im injection of 250 mg naltrexone, immediately after tag attachment. Twenty-seven of the animals were intubated and ventilated with 100% oxygen during the recovery period. The induction time was, on average, 4 min 51 sec ± 1 min 46 sec. Several animals had venous pH, and Pco2 levels that indicated severe acidosis and hypercarbia. All animals recovered within an average of 5 min 16 sec ± 2 min 47 sec after reversal. The total time from darting to recovery was 15 min 23 sec ± 3 min 33 sec. The use of naltrexone is recommended for reversal of etorphine immobilization in adult, male walruses, and the use of positive-pressure ventilation with oxygen is highly encouraged.

Temporal integration of sound motion: Motion-onset response and perception.

The purpose of our study was to estimate the time interval required for integrating the acoustical changes related to sound motion using both psychophysical and EEG measures. Healthy listeners performed direction identification tasks under dichotic conditions in the delayed-motion paradigm. Minimal audible movement angle (MAMA) has been measured over the range of velocities from 60 to 360 deg/s. We also measured minimal duration of motion, at which the listeners could identify its direction. EEG was recorded in the same group of subjects during passive listening. Motion onset responses (MOR) were analyzed. MAMA increased linearly with motion velocity. Minimum audible angle (MAA) calculated from this linear function was about 2 deg. For higher velocities of the delayed motion, we found 2- to 3-fold better spatial resolution than the one previously reported for motion starting at the sound onset. The time required for optimal discrimination of motion direction was about 34 ms. The main finding of our study was that both direction identification time obtained in the behavioral task and cN1 latency behaved like hyperbolic functions of the sound's velocity. Direction identification time decreased asymptotically to 8 ms, which was considered minimal integration time for the instantaneous shift detection. Peak latency of cN1 also decreased with increasing velocity and asymptotically approached 137 ms. This limit corresponded to the latency of response to the instantaneous sound shift and was 37 ms later than the latency of the sound-onset response. The direction discrimination time (34 ms) was of the same magnitude as the additional time required for motion processing to be reflected in the MOR potential. Thus, MOR latency can be viewed as a neurophysiological index of temporal integration. Based on the findings obtained, we may assume that no measurable MOR would be evoked by slowly moving stimuli as they would reach their MAMAs in a time longer than the optimal integration time.

Facial and systemic mucormycosis caused by Lichtheimia corymbifera in a goat: case report and literature review of fungal infections in goats.

An 8-y-old Pygora doe was presented to the University of California-Davis, Veterinary Medical Teaching Hospital because of non-healing facial swelling of 2-wk duration. The lesion grew despite medical treatment, causing discomfort masticating, little-to-no airflow from the right nasal passage, and led to euthanasia. On gross examination, a large facial mass with a draining tract through the skin and hard palate was identified. On section, the mass was brown-pink, homogeneous, and friable. Abscess-like masses were identified in the lungs and kidney. Histopathology of the face, including oral and nasal cavities, salivary glands, and lymph nodes, as well as the lung and kidney lesions, revealed large areas of necrosis with numerous wide ribbon-like, mostly aseptate, fungal hyphae consistent with zygomycetes. PCR for fungal organisms performed on formalin-fixed, paraffin-embedded tissue from the face identified Lichtheimia corymbifera (formerly Absidia corymbifera) of the order Mucorales and an Aspergillus sp. The lesion was suspected to have started either as a fungal rhinitis or dental feed impaction, subsequently spreading to the face and systemically to the lungs and kidney. We describe here the lesions associated with facial mucormycosis in a goat and present a literature review of L. corymbifera infection in veterinary species and fungal infections in goats.

Brain oscillations evoked by sound motion.

The present study investigates the event-related oscillations underlying the motion-onset response (MOR) evoked by sounds moving at different velocities. EEG was recorded for stationary sounds and for three patterns of sound motion produced by changes in interaural time differences. We explored the effect of motion velocity on the MOR potential, and also on the event-related spectral perturbation (ERSP) and inter-trial phase coherence (ITC) calculated from the time-frequency decomposition of EEG signals. The phase coherence of slow oscillations increased with an increase in motion velocity similarly to the magnitude of cN1 and cP2 components of the MOR response. The delta-to-alpha inter-trial spectral power remained at the same level up to, but not including, the highest velocity, suggesting that gradual spatial changes within the sound did not induce non-coherent activity. Conversely, the abrupt sound displacement induced theta-alpha oscillations which had low phase consistency. The findings suggest that the MOR potential could be mainly generated by the phase resetting of slow oscillations, and the degree of phase coherence may be considered as a neurophysiological indicator of sound motion processing.

Mismatch negativity and psychophysical detection of rising and falling intensity sounds.

Human subjects demonstrate a perceptual priority for rising level sounds compared with falling level sounds. The aim of the present study was to investigate whether or not the perceptual preference for rising intensity can be found in the preattentive processing indexed by mismatch negativity (MMN). Reversed oddball stimulation was used to produce MMNs and to test the behavioral discrimination of rising, falling and constant level sounds. Three types of stimuli served as standards or deviants in different blocks: constant level sounds and two kinds of rising/falling sounds with gradual or stepwise change of intensity. The MMN amplitudes were calculated by subtracting ERPs to identical stimuli presented as standard in one block and deviant in another block. Both rising and falling level deviants elicited MMNs which peaked after 250 ms and did not overlap with N1 waves. MMN was elicited by level changes even when the deviants were not discriminated behaviorally. Most importantly, we found dissociation between earlier and later stages of auditory processing: the MMN responses to the level changes were mostly affected by the direction of deviance (increment or decrement) in the sequence, whereas behavioral performance depended on the direction of the level change within the stimuli (rising or falling).

On terahertz pulsed broadband Gauss-Bessel beam free-space propagation.

Terahertz pulse time-domain holography is the ultimate technique allowing the evaluating a propagation of pulse broadband terahertz wavefronts and analyze their spatial, temporal and spectral evolution. We have numerically analyzed pulsed broadband terahertz Gauss-Bessel beam's both spatio-temporal and spatio-spectral evolution in the non-paraxial approach. We have characterized two-dimensional spatio-temporal beam behavior and demonstrated all stages of pulse reshaping during the propagation, including X-shape pulse forming. The reshaping is also illustrated by the energy transfer dynamics, where the pulse energy flows from leading edge to trailing edge. This behavior illustrates strong spatio-temporal coupling effect when spatio-temporal distribution of Bessel beam's wavefront depends on propagation distance. The spatio-temporal and spatio-spectral profiles for different spectral components clearly illustrate the model where the Bessel beam's wavefront at the exit from the axicon can be divided into radial segments for which the wave vectors intersect. Phase velocity via propagation distance is estimated and compared with existing experimantal results. Results of the phase velocity calculation depend strongly on distance increment value, thus demonstrating superluminal or subluminal behavior.