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Vestibular evoked myogenic potentials (VEMP) have been used to assess otolith function in clinics worldwide. However, there are accumulating evidence suggesting that the clinically used sound stimuli activate not only the otolith afferents, but also the canal afferents, indicating canal contributions to the VEMPs. To better understand the neural mechanisms underlying the VEMPs and develop discriminative VEMP protocols, we further examined sound-evoked responses of the vestibular nucleus neurons and the abducens neurons, which have the interneurons and motoneurons of the vestibulo-ocular reflex (VOR) pathways. Air-conducted clicks (50–80 dB SL re ABR threshold, 0.1 ms duration) or tone bursts (60–80 dB SL, 125–4,000 Hz, 8 ms plateau, 1 ms rise/fall) were delivered to the ears of Sprague-Dawley or Long-Evans rats. Among 425 vestibular nucleus neurons recorded in anesthetized rats and 18 abducens neurons recorded in awake rats, sound activated 35.9% of the vestibular neurons that increased discharge rates for ipsilateral head rotation (Type I neuron), 15.7% of the vestibular neurons that increased discharge rates for contralateral head rotation (Type II neuron), 57.2% of the vestibular neurons that did not change discharge rates during head rotation (non-canal neuron), and 38.9% of the abducens neurons. Sound sensitive vestibular nucleus neurons and abducens neurons exhibited characteristic tuning curves that reflected convergence of canal and otolith inputs in the VOR pathways. Tone bursts also evoked well-defined eye movements that increased with tone intensity and duration and exhibited peak frequency of ∼1,500 Hz. For the left eye, tone bursts evoked upward/rightward eye movements for ipsilateral stimulation, and downward/leftward eye movements for contralateral stimulation. These results demonstrate that sound stimulation results in activation of the canal and otolith VOR pathways that can be measured by eye tracking devices to develop discriminative tests of vestibular function in animal models and in humans. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) require an excellent matrix support material such as porous carbon materials. Orange peel, a discarded, readily available raw material, could potentially be used to prepare biological porous carbon material (BPCM) with abundant pores of uniform size and strong loading capacity through a vacuum freeing method and a carbonization process under nitrogen atmosphere. Herein, paraffin (PA) was encapsulated into BPCM by vacuum impregnation method to obtain environmentally friendly; recyclable PA/carbonized-abandoned orange peel (CAOP) shape-stable PCMs (PA/CAOP SS-PCMs). CAOP was composed of amorphous carbon and a certain degree of graphitization occurred, the best of which was observed following carbonization at 1000 °C. Further, at this temperature, the pores were abundant and PA loading was sufficient. PA/CAOP SS-PCMs were shown to undergo simple physical loading with no chemical interactions and to have good thermal stability and a maximum loading percentage of 88.46%; the calculated maximum loading percentage was of 88.07%. The temperature and latent heat during the melting of PA/CAOP SS-PCMs were 47.68 °C and 180.25 J/g, respectively, and the solidification process occurred 34.47 °C and 177.55 J/g, respectively. The composite exhibited excellent thermal stability and reliability after 200 thermal cycles. Therefore, it has very broad application prospects and value in the fields of energy saving and emission reduction, including solar energy, air conditioning storage cooling systems, and building cladding. [ABSTRACT FROM AUTHOR]

In this paper, ZrO 2 -SiC-Al 2 O 3 ceramic was fabricated by as-prepared ZrO 2 -SiC powders and commercial α-Al 2 O 3 powders, sintered at 1450 °C for 1 h. ZrO 2 -SiC composite powders were synthesized through carbothermal reduction with zircon as raw material and carbon black as the reductant. Through ZrO 2 -SiC-Al 2 O 3 ceramic mechanical properties measurements it was indicated that this ceramic had excellent properties in both bending strength and hardness. In addition, ZrO 2 -SiC-Al 2 O 3 ceramic abrasive wear property was measured. ZrO 2 -SiC-Al 2 O 3 ceramic mass loss increased along with the increase in both wheel rate and applied load. The type of wear particles had an important effect on abrasive wear resistance. ZrO 2 -SiC-Al 2 O 3 ceramic displayed excellent abrasive wear resistance in bentonite and quartz slurries in comparison with SiC slurry. [ABSTRACT FROM AUTHOR]

Abstract: ZrN–Si3N4 composite powders were synthesised from natural zircon and quartz via carbothermal reduction and nitridation reaction. The effects of various raw material compositions and heating temperatures on phase transformation and product morphologies under flowing nitrogen atmosphere were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The phase equilibrium relationships of the ZrO2–SiO2–C–N2 system at different heating temperatures were also investigated based on the thermodynamic analysis. Products with different phase compositions and morphologies were obtained at different conditions. The products were composed of ZrN, β-Si3N4 and a small amount of c-ZrO2 by carbothermal reduction and nitridation of zircon with less than 20wt.% quartz. With 30wt.% quartz, granular ZrN as well as columnar and acicular β-Si3N4 were detected in the products. With 40wt.% or 50wt.% quartz, the products consisted of ZrN, β-Si3N4, Si2N2O, c-ZrO2 and m-ZrO2. The optimum quartz content for synthesizing ZrN–Si3N4 composite powders was 30wt.%. At heating temperatures below 1600°C, the products were composed of ZrN, β-Si3N4, β-SiC, Si2N2O, m-ZrO2 and c-ZrO2. [Copyright &y& Elsevier]

Self-strengthened mullite ceramics with interlocking columnar grains formed through enhanced anisotropic growth by adding La2O3 were prepared from coal gangue and γ-Al2O3 within the temperature range 1400–1550°C and holding time of 4h. The effects of La2O3 on the bending strength, microstructural evolution, and phase composition were studied. The results showed that the bending strength of the as-prepared ceramics was significantly improved by the addition of La2O3. For samples sintered at 1550°C, the bending strength increased from 64MPa to 218MPa as the La2O3 content increased from 0mol% to 10mol%. X-ray diffraction analysis suggested that the formation temperature of secondary mullite was lowered by about 50°C by adding La2O3. Scanning electron micrographs revealed that the La2O3-added mullite mostly existed in long, columnar form, with aspect ratios of 3–6, forming an interlocking network structure. The interlocking mullite columns, together with the enhanced densification behaviour, contributed to the improved bending strength. [ABSTRACT FROM AUTHOR]

Abstract: β-Si3N4 powder was synthesized via carbothermal reduction nitridation (CRN) method using quartz as starting material. The influence of synthesis temperature, C/SiO2 molar ratio and amount of Fe2O3 additive on the phase transformation and micro-morphology of β-Si3N4 powder was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The results showed that the optimal experimental conditions for the CRN synthesis of β-Si3N4 powder were 3h sintering at 1600°C in flowing nitrogen atmosphere with C/SiO2 molar ratio of 2.0 and amount of Fe2O3 additive of 5.0wt.%. The prepared β-Si3N4 grains present a short hexagonal, rod-like morphology. Changes in experimental parameters affect the phase compositions and the morphology of the product. Excessive carbon promoted the formation reaction of β-SiC. Fe2O3 additive exerted a significant promotion on the formation of β-Si3N4 in CRN process by forming the low melting point eutectics. [Copyright &y& Elsevier]

Sound activates not only the cochlea but also the vestibular end organs. Research on this phenomenon led to the discovery of the sound-evoked vestibular myogenic potentials recorded from the sternocleidomastoid muscles (cervical VEMP, or cVEMP). Since the cVEMP offers simplicity and the ability to stimulate each labyrinth separately, its values as a test of human vestibular function are widely recognized. Currently, the cVEMP is interpreted as a test of saccule function based on the assumption that clicks primarily activate the saccule. However, sound activation of vestibular end organs other than the saccule has been reported. To provide the neural basis for interpreting clinical VEMP testing, we employed the broadband clicks used in clinical VEMP testing to examine the sound-evoked responses in a large sample of vestibular afferents in Sprague-Dawley rats. Recordings were made from 924 vestibular afferents from 106 rats: 255 from the anterior canal (AC), 202 from the horizontal canal (HC), 177 from the posterior canal (PC), 207 from the superior vestibular nerve otolith (SO), and 83 from the inferior nerve otolith (IO). Sound sensitivity of each afferent was quantified by computing the cumulative probability of evoking a spike (CPE). We found that clicks activated irregular afferents (normalized coefficient of variation of interspike intervals >0.2) from both the otoliths (81%) and the canals (43%). The order of end organ sound sensitivity was SO = IO > AC > HC > PC. Since the sternocleidomastoid motoneurons receive inputs from both the otoliths and the canals, these results provide evidence of a possible contribution from both of them to the click-evoked cVEMP.

Objectives: In this study, we characterized the frequency tuning of bone-conducted sound-evoked myogenic potentials recorded from extraocular muscles (BOVEMP) in normal human subjects., Study Design: Experimental design., Methods: In a sample of nine subjects, acoustic tone bursts (57 dB nHL, 8 ms plateau, 1 ms rise/fall, alternating polarity) with frequencies from 250 Hz to 2,000 Hz were delivered by a bone oscillator (Radioear B-71) placed on the left mastoid processes. Subjects were required to sit upright and maintain a straight gaze. The BOVEMPs were recorded from surface electrodes placed at four locations around the right eye (superior, inferior, nasal, and temporal) and referenced to an electrode placed at the nape of the neck over cervical vertebrate C7. Signals from electrodes were amplified (10,000 gain) and sampled at 10 kHz and were averaged over 500 repetitions., Results: Short latency biphasic potential were present at each of the four recording sites around the eye. The average latency of the first peak (negative) and the second peak (positive) was 15.7 ± 0.3 ms and 23.3 ± 0.5 ms, respectively. The tuning curve of the BOVEMP was similar at each recording site with largest N1 amplitude following stimulation at 383 Hz (± 17 Hz) and largest P1 amplitude following stimulation at 440 Hz (± 22 Hz)., Conclusions: Since the frequency tuning for the bone-conducted sound-evoked OVEMP (BOVEMP) was different from that of the air-conducted sound-evoked OVEMP (AOVEMP), we hypothesize that the BOVEMP and AOVEMP are generated by activation of different vestibular end organs.

Objective: In this cross-sectional study, we investigated the frequency tuning properties of sound-evoked vestibular myogenic potentials in extraocular muscles (OVEMPs) in normal human subjects., Methods: Acoustic tone bursts (130 dB pSPL, 10 ms plateau, 1 ms rise/fall) with nine frequencies from 125 to 4000 Hz were presented monoaurally to 12 normal subjects while they sat upright and maintained centre gaze. Using surface electrodes, the OVEMPs were recorded at four locations surrounding the contralateral eye (superior, inferior, nasal, and temporal) and were referenced to an electrode placed at the nape of the neck over C7. To measure the amplitudes of the OVEMP, signals from the electrodes were amplified and sampled at 10 kHz and were averaged over 250 repetitions., Results: We found that the OVEMPs recorded at the four sites exhibited similar well-defined frequency tuning with peak amplitude at ≈ 1000 Hz., Conclusion: Although several studies have examined the frequency tuning of the vestibular evoked myogenic potential measured from the sternocleidomastoid muscles (SVEMP), the reported results are quite variable as regards frequency, which produces peak amplitude. The well-defined OVEMP frequency tuning provides an alternative to the SVEMP for assessing vestibular function via acoustic stimulation. Further studies are needed to identify the extent to which each of the five vestibular end-organs is activated by sound and their contribution to the sound-evoked vestibular myogenic potentials.

Multiplicative computation is a basic operation that is crucial for neural information processing, but examples of multiplication by neural pathways that perform well-defined sensorimotor transformations are scarce. Here in behaving monkeys, we identified a multiplication of vestibular and eye position signals in the vestibulo-ocular reflex (VOR). Monkeys were trained to maintain fixation on visual targets at different horizontal locations and received brief unilateral acoustic clicks (1 ms, rarefaction, 85 approximately 110 db NHL) that were delivered into one of their external ear canals. We found that both the click-evoked horizontal eye movement responses and the click-evoked neuronal responses of the abducens neurons exhibited linear dependencies on horizontal conjugate eye position, indicating that the interaction of vestibular and horizontal conjugate eye position was multiplicative. Latency analysis further indicated that the site of the multiplication was within the direct VOR pathways. Based on these results, we propose a novel neural mechanism that implements the VOR gain modulation by fixation distance and gaze eccentricity. In this mechanism, the vestibular signal from a single labyrinth interacts multiplicatively with the position signals of each eye (Principle of Multiplication). These effects, however, interact additively with the other labyrinth (Principle of Addition). Our analysis suggests that the new mechanism can implement the VOR gain modulation by fixation distance and gaze eccentricity within the direct VOR pathways.