Search

Several studies have reported that bone-conducted ultrasound (BCU) is even perceived by the profoundly sensorineural deaf; however, the mechanisms involved remain unclear. We previously reported some unique characteristics of BCU perception that suggest unique neurophisiological mechanisms. For example: (1) the pitch of BCU is 10-odd kHz and is independent of its frequency; (2) no beats occur between BCU and 10-odd-kHz air-conducted sinusoids; (3) BCU masks 10-14 kHz air-conducted sounds; and (4) the dynamic range of loudness for BCU is less than 20 dB. In the present study, several electrophysiological measurements were carried out to clarify the neural pathway involved in BCU perception. Specifically, auditory brainstem responses (ABRs), middle latency responses (MLRs), and cortical magnetic activities evoked by BCU were measured in humans. Substantial ABRs (wave I -V) and MLRs were evoked by BCU as well as air-conducted audible sound. In terms of cortical activities, clear N1m responses were elicited by BCU, with their sources being localized in the auditory cortices. However, BCU showed later, smaller, more posterior, and more lateral sources than audible-frequency sounds, and therefore did not appear to follow a tonotopic organization at the cortical level. These results indicate that: (1) the cochlea substantially contributes to BCU perception; (2) BCU goes through the normal auditory pathway and there is no special organ for BCU perception; and (3) some differences in the inner ear mechanisms may exist between audible sounds and BCU.

The intention of this study is to develop an immersion lithography process using advanced track solutions to achieve world class critical dimension (CD) and defectivity performance in a state of the art manufacturing facility. This study looks at three important topics for immersion lithography: defectivity, CD control, and wafer backside contamination. The topic of defectivity is addressed through optimization of coat, develop, and rinse processes as well as implementation of soak steps and bevel cleaning as part of a comprehensive defect solution. Develop and rinse processing techniques are especially important in the effort to achieve a zero defect solution. Improved CD control is achieved using a biased hot plate (BHP) equipped with an electrostatic chuck. This electrostatic chuck BHP (eBHP) is not only able to operate at a very uniform temperature, but it also allows the user to bias the post exposure bake (PEB) temperature profile to compensate for systematic within-wafer (WiW) CD non-uniformities. Optimized CD results, pre and post etch, are presented for production wafers. Wafer backside particles can cause focus spots on an individual wafer or migrate to the exposure tool's wafer stage and cause problems for a multitude of wafers. A basic evaluation of the cleaning efficiency of a backside scrubber unit located on the track was performed as a precursor to a future study examining the impact of wafer backside condition on scanner focus errors as well as defectivity in an immersion scanner.

Resist process challenges for 32-nm node and beyond are discussed in this paper. For line and space (L/S) logic patterns, we examine ways to balance the requirements of resolution-enhancement techniques (RETs). In 32-nm node logic patterning, two-dimensional (2D) layout pattern deformation becomes more severe with stronger RET (e.g., narrow angle CQUAD illumination). Also pattern collapse more frequently happens in 2D-pattern layouts when stronger RET is used. In contrast, milder RET (annular illumination) does not induce the severe pattern collapse in 2D-pattern layout. For 2D-pattern layouts, stronger RET seems to worsen image contrast and results in high background-light in the resist pattern, which induces more pattern collapse. For the minimum-pitch L/S pattern in 32-nm node logic, annular illumination is acceptable for patterning with NA1.35 scanner when high contrast resist is used. For contact/via patterns, it is necessary to expand the overlapping CD process window. Better process margin is realized through the combination of hole-shrink technique and precise acid-diffusion control in an ArF chemically amplified resist.

Speech-recognition rates decrease in noisy environments. The body-conducted speech, conducted in solids such as body and skins, has a noise-robust characteriscs and can be served for recognition systems even in 98 dBSPL (−20 dBSNR) noise environments. However, the body-conduction can not capture high frequency sounds. Conventional methods to improve sound quality of body-conducted speeches need both speeches themselves and body-conducted speeches. In this paper, a new body-conducted speech retrieval technique in sound quality without a speech signal itself is proposed. First, high-frequency components in the body-conducted speech were emphasized using differential acceleration. Second, a conventional noise reduction method was adopted to make a clear body-conducted speech from a retrieval speech which contains constant noise. The recognition experiments using the proposed method showed that it improved recognition rate in all speakers.

N1m is an auditory evoked brain magnetic field with a magnitude of 100 fT order observed over the auditory cortex, 100 ms after the onset of auditory stimuli. The N1m is often used as a landmark of functional localization in the cortex. However, the mechanism of the N1m has not yet been clarified. The N1m peak amplitude and latency are dependent on the specifics of the stimulus; duration, intensity, and sequence of stimuli. In this study, we examined the dependency of the N1m peak amplitude and latency on the stimulus duration and frequency. Trains of 0.2 ms clicks were used for auditory stimuli by changing the number of clicks and the click interval. Auditory brain magnetic responses evoked by the click trains were recorded from seven human adult subjects by a dc superconducting quantum interference device magnetometer. In the results of this study, the N1m amplitudes significantly increased as the stimulus duration increased and the amplitudes leveled when the stimulus duration reached 32 ms. The amplitudes produced by the trains with the same number of clicks showed greater values for 4-ms-interval trains. The N1m latencies significantly decreased as the stimulus duration increased and leveled at 32 ms. It is concluded that all clicks received within 32 ms were integrated and that this integration mechanism is dependent upon the click interval. Increased synchrony of neuronal cells at the cortical level can explain this integration mechanism.N1m is an auditory evoked brain magnetic field with a magnitude of 100 fT order observed over the auditory cortex, 100 ms after the onset of auditory stimuli. The N1m is often used as a landmark of functional localization in the cortex. However, the mechanism of the N1m has not yet been clarified. The N1m peak amplitude and latency are dependent on the specifics of the stimulus; duration, intensity, and sequence of stimuli. In this study, we examined the dependency of the N1m peak amplitude and latency on the stimulus duration and frequency. Trains of 0.2 ms clicks were used for auditory stimuli by changing the number of clicks and the click interval. Auditory brain magnetic responses evoked by the click trains were recorded from seven human adult subjects by a dc superconducting quantum interference device magnetometer. In the results of this study, the N1m amplitudes significantly increased as the stimulus duration increased and the amplitudes leveled when the stimulus duration reached 32 ms. The amplit...

Abstract Many studies involving the application of geophysical methods in the field of gas hydrates have focused on determining rock physics relationships for hydrate-bearing sediment with the goal being to delineate the boundaries of gas hydrate accumulations and to estimate the quantities of gas hydrate such accumulations contain using remote sensing techniques. However, the potential for using time-lapse geophysical methods to monitor the evolution of hydrate accumulations during production and thus to manage production has not been investigated. In this work we begin to examine the feasibility of using time-lapse geophysical methods for monitoring changes in hydrate accumulations that are predicted to occur during production of natural gas. This is made possible through the coupled simulation of (1) large-scale production in hydrate accumulations and (2) time-lapse geophysical surveys. We consider a geological system, based on a hydrate accumulation in the Gulf of Mexico, which represents a promising target for production. While the current study focuses on seismic measurements, the approach can easily be extended to consider additional geophysical methods, such as electromagnetic methods. In addition to examining the sensitivity of geophysical attributes and parameters to the changing conditions in hydrate accumulations, we aim to determine optimal sampling strategies (e.g., source frequency, time interval for data acquisition) and measurement configurations (e.g., surface seismic reflection, and vertical seismic profiling), while taking into account uncertainties in rock physics relationships. The numerical simulation tool being developed in this work provides a means for designing cost effective geophysical surveys to track the evolution of hydrate properties. This work also serves as a basis for developing a comprehensive method for monitoring production that integrates multiple types of geophysical and hydrological data. Here we describe the modeling procedure and present some preliminary results. Introduction Background. Identifying the extent of gas hydrate accumulations, predicting their behavior, and monitoring their properties is of great importance. Gas hydrates-solid crystalline structures consisting of water and gas molecules (usually methane)-are distributed widely across the earth in permafrost and under the ocean (Sloan, 1998). When conditions in hydrate-bearing sediment (HBS) become thermodynamically unfavorable for gas hydrates (e.g., when the pressure decreases or the temperature increases and moves the system away from the hydrate stability zone), dissociation can occur releasing large amounts of gas and water. Thus gas hydrates are viewed as a promising source of alternative energy (Kvenvolden, 1994; 2002), in hopes that dissociation can be induced in hydrate accumulations in a controlled manner while natural gas is harvested (Makogen, 1997). The presence of HBS also serves as a hazard to hydrocarbon production platforms or infrastructure, the integrity of which is at risk due to ocean floor instabilities arising from dissociation-induced sub-marine landslides or subsidence (Moridis and Kowalsky, 2007). The use of geophysical methods for identifying hydrate accumulations and quantifying the amount of gas hydrates present in the subsurface has been investigated for many years and appears promising (e.g., Hyndman and Spence, 1992; Yuan et al., 1996; Andreassen et al, 1997; Ecker et al., 1998; Ecker et al., 2000; Gueren et al. 1999). There still remains much uncertainty in seismic (Helgerud et al., 1999; Gueren and Goldberg, 2005) and electrical (Spangenberg, 2001; Sun and Goldberg, 2005) rock physics relationships for HBS. The use of geophysical methods to remotely monitor the state of hydrate accumulations undergoing production (at distant locations where well-logging techniques can not be applied) is only beginning to be examined, which is made possible by recent advances in the ability to model the complex processes that occur in such systems which inevitably involve the nonisothermal, multiphase transport of fluids and gas.

Abstract An on-going effort of conducting laboratory triaxial compression tests on synthetic methane hydrate-bearing sediment cores is presented. Methane hydrate is formed within a sand pack inside a test cell under a controlled temperature and confining stress, and triaxial compression tests are performed while monitoring seismic properties. A unique aspect of our experiment is that the formation and dissociation of hydrate in a sediment core, and the failure of the sample during loading tests, can be monitored in real time using both seismic waves and x-ray CT imaging. For this purpose, we built a specially designed triaxial (geomechanical) test cell. This cell allows us to conduct seismic wave measurements on a sediment core using compressional and shear (torsion) waves. Concurrently, CT images can be obtained through an x-ray-transparent cell wall, which are used to determine the porosity distribution within a sample owing to both original sand packing and formation of hydrate in the pore space. For interpreting the results from both seismic measurements and geomechanical tests, characterization of sample heterogeneity can be critically important. In this paper, we present the basic functions of our test cell, and the results of preliminary experiments using a sandpack without hydrate and a sandstone core. These measurements confirmed that (1) clear x-ray images of gas-fluid boundaries within a sediment/rock core can be obtained through a thick aluminum test cell wall, (2) the test cell funcions correctly during loading tests, and (3) both compressional and shear waves can be measured during a loading test. Further experiments using methane hydrate-bearing samples will be presented at the conference. Introduction Because of geomechanical stability concerns, the placement of wells and seafloor platforms associated with oil production is strongly influenced by the presence of gas hydrates on the sea floor or within the sediment lithology. These concerns will be far more pronounced if gas production from oceanic gas hydrate accumulation is to become an economically viable option in the future. Thermal loading and dissociation caused by warm reservoir fluids (originating from a deeper conventional reservoir under production) ascending through wellbores that intersect hydrate-bearing sediments (HBS) can also have adverse consequences for the HBS stability. The current state of knowledge on the properties of HBS that have a direct impact on the seafloor stability is still in its infancy. Additionally, for remote detection, resource evaluation and monitoring of in-situ HBS during exploration and production of oil and gas (including gas production from the hydrates), it is essential to establish concurrently the quantitative relationships among index properties (sediment porosity, hydrate saturation, gas saturation, etc.), geophysical properties (seismic velocities and attenuation, in particular), and geomechanical properties (mechanical stiffness, strength, time-dependent behavior) of HBS. Detailed strength measurements that were conducted on laboratory-made, pure methane (CH4)-hydrate samples (Durham et al., 2003; Stern et al., 1996). Stern et al (1996) indicated that the mechanical, plastic flow properties of CH4 hydrates are very different from those of water ice. Thus, unlike ice (which exhibits yielding and softening), CH4-hydrates exhibit continuous hardening, and solid-state disproportionation and exsolution. These results suggest that geomechanical tests using water ice as an analogue may result (e.g., Nagaeki et al., 2004) in erroneous conclusions for the mechanical properties of oceanic HBR.

Permeability of a fracture can affect how the fracture interacts with seismic waves. To examine this effect, a simple mathematical model that describes the poroelastic nature of wave-fracture interaction is useful. In this paper, a set of boundary conditions is presented which relate wave-induced particle velocity (or displacement) and stress including fluid pressure across a compliant, fluid-bearing fracture. These conditions are derived by modeling a fracture as a thin porous layer with increased compliance and finite permeability. Assuming a small layer thickness, the boundary conditions can be derived by integrating the governing equations of poroelastic wave propagation. A finite jump in the stress and velocity across a fracture is expressed as a function of the stress and velocity at the boundaries. Further simplification for a thin fracture yields a set of characteristic parameters that control the seismic response of single fractures with a wide range of mechanical and hydraulic properties. These boundary conditions have potential applications in simplifying numerical models such as finite-difference and finite-element methods to compute seismic wave scattering off nonplanar (e.g., curved and intersecting) fractures.

We previously demonstrated that late electromyographic responses with a latency of 100 ms were evoked bilaterally in soleus muscles following transcranial magnetic stimulation over the left cerebellum. Efferent fibers from the left cerebellum modulate vestibulospinal tract influences on the extensor muscles of the left hindlimb. Here, we investigated whether the vestibulospinal tract mediates this late response. We activated the vestibulospinal tract by optokinetic stimulation. Our results show that the latency of the soleus electromyographic response is shortened by optokinetic stimulation, but the latency of the motor response evoked by the corticospinal tract is unchanged. These findings support our hypothesis that vestibulospinal tracts mediate late electromyographic responses, and allow the development of techniques to assess the human vestibulospinal system function.

Summary An experimental device for measuring the transverse isotropic (TI) elastic properties of sediments unde r uniaxial strain conditions has been developed. The phased array compaction cell utilizes matched sets of P- and S-wave ultrasonic transducers located along the sides of t he sample and an ultrasonic P-wave phased array source with pinducer receiver on the ends of the sample. The p hased array provides plane P-waves that are used to measu re phase velocities over a range of angles. From thes e measurements, the five elastic constants for TI med ia can be recovered as the sediment is compacted, without the need for sample unloading or reorienting. Descripti ons of the apparatus and data processing and an applicatio n to an unconsolidated sand sample are provided in this pap er. Pwave anisotropy of 20% has been observed in dry sand under an axial stress of 5 MPa.

A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.

Valve sounds are thought to be useful in evaluating the functioning of prosthetic heart valves. In previous reports, two recording instruments have mainly been used, a condenser microphone (instrument A) and an accelerometer (instrument B), respectively. This study aimed to investigate the applicability of these conventional devices in recording mechanical heart valve sounds in daily clinical situations. In addition, two other instruments, namely, a stethoscope including a small microphone in its tube (instrument C) and an electrostethoscope (instrument D), were proposed and examined.Mechanical valve sounds were recorded from postoperative patients using each-device and the signal to noise ratio (SNR) of each was calculated. Frequency characteristics of the two newly proposed instruments were also investigated by recording a sweep signal in an anechoic chamber.The SNR values of the new instruments were significantly superior to those of conventional ones (A, sound signals were not defined from noises; B, 0.97 +/- 0.59 dB; C, 11.5 +/- 4.7 dB; and D, 9.4 +/- 3.5 dB, respectively p0.05). The frequency characteristics of the two newly proposed instruments were also shown to be acceptable (under 10 kHz), though resonance frequency peaks were observed.Two newly proposed instruments can record mechanical heart valve sounds more noiselessly and with more ease than previous ones, and their frequency characteristics are acceptable.

Psychophysical experiments in humans have indicated that the auditory system has a well-defined bandwidth for resolution of complex stimuli. This bandwidth is known as the critical bandwidth (CBW). Physiological correlates of the CBW were examined in the human auditory cortex. Two- and three-tone complexes were used as the sound stimuli with all signals presented at 55 dB sound pressure level (SPL). The duration of stimulation was 500 ms, with rise and fall ramps of 10 ms. Ten normal-hearing subjects took part in the study. Auditory-evoked fields were recorded using a 122-channel whole-head magnetometer in a magnetically shielded room. The latencies, source strengths, and coordinates of the N1m waves, which were found above the left and right temporal lobes approximately 100 ms after the onset of stimulation, were analyzed. The results indicated that N1m amplitudes were approximately constant when the frequency separation of a two-tone complex or the total bandwidth of a three-tone complex was less than the CBW; however, the N1m amplitudes increased with increasing frequency separation or total bandwidth when these were greater than the CBW. These findings indicate critical band-like behavior in the human auditory cortex. The N1m amplitudes in the right hemisphere were significantly greater than those in the left hemisphere, which may reflect a right-hemispheric dominance in the processing of tonal stimuli.

The two cues to the horizontal location sound sources are interaural time differences and interaural level differences. For low-frequency tones, interaural time differences provide effective and unambiguous information. For higher frequency sounds, however, interaural time differences provide ambiguous cues. In order to evaluate the effect of frequency of interaural time differences in the human auditory cortex, the auditory evoked fields to different interaural time differences of pure tone were examined. The results showed that the N1m magnitudes varied with the interaural time differences when the frequency of the pure tone was 800 Hz. The N1m magnitudes, however, did not vary with the interaural time differences when the frequency of the pure tone was 1600 Hz. These results indicate that localization performance might be reflected in N1m magnitudes.

Modeling the effect of seismic stimulation employing Maxwell‐Boltzmann theory shows that the important component of stimulation is mechanical rather than fluid pressure effects. Modeling using Biot theory (two phases) shows that the pressure effects diffuse too quickly to be of practical significance. Field data from actual stimulation will be shown to compare to theory.

The detection of interaural time differences (ITD) for sound localization depends on the similarity between the left and right ear signals, namely interaural correlation (IAC). Human localization performance deteriorates with decreasing IACs. In order to examine activity related to localization performance in the human cortex, auditory evoked magnetic fields to the ITD of bandpass noises with different IACs were analyzed. When the IAC was 0.95, the N1m amplitudes, i.e., the estimated equivalent current dipole moments, increased with increasing ITD. However the effect of ITD on the N1m amplitudes was not significant when the IAC was 0.5. When the ITD was 0.7 ms, the N1m amplitudes decreased with decreasing IACs. There were no systematic changes in the source location of N1m in the auditory cortex related to changes in ITD or IAC. The results suggest that localization performance is reflected in N1m amplitudes.

Red berries of a tropical plant called miracle fruit, Richadella dulcifica, reduce the sour and aversive taste of acids and add sweet and palatable taste. To elucidate the brain mechanism of this unique action of miracle fruit, we recorded taste-elicited magnetic fields of the human cerebral cortex. The initial taste responses were localized in the fronto-parietal opercular/insular cortex reported as the primary taste area. The mean latency of the response to citric acid after chewing miracle fruit was essentially the same as that for sucrose and was 250-300 ms longer than that for citric acid. Since it is known that stimulation with acids after the action of miracle fruit induces both sweetness and sourness responses in the primate taste nerves, the present results suggest that the sourness component of citric acid is greatly diminished at the level of subcortical relays, and mostly sweetness information reaches the cortical primary taste area. We propose the idea that the qualitative aspect of taste is processed in the primary taste area and the affective aspect is represented by the pattern of activation among the different cortical areas.

Changes in the bandwidth affect the perceived loudness of a stimulus even when the level of the stimulus remains fixed. If the bandwidth of a sound is varied while maintaining the overall intensity, the loudness remains constant as long as the bandwidth is less than the critical bandwidth. If the bandwidth is increased beyond the critical bandwidth, the loudness increases with increasing bandwidth. Human cortical responses as a function of stimulus bandwidth were examined by recording auditory-evoked magnetic fields. The results showed that the N1m magnitudes, that is, the estimated equivalent current dipole moments, increased with increasing bandwidth when the bandwidth was increased beyond the critical bandwidth.

A series of rock-property measurements was performed on a suite of rhyolitic tuff samples from the area above the Aberdeen Tunnel of Hong Kong. The goal of this study was to determine the mechanical properties of these samples after weathering. This report contains petrographic descriptions, porosity, bulk and grain density, as well as ultrasonic measurements, elastic modulii calculations, and rock-strength determinations. Variations in rock properties are related to alteration and the presence of fractures in the tuff. Granitic rocks located adjacent to the altered tuffs would be better candidates for underground excavations.

The aim of this study is to identify the relationship between subjective preference and the human brain responses to visual motion under changing period. First, preference judgments using the paired-comparison method for sinusoidal movements of a single circular target in the horizontal direction were performed. Then, MEG data were recorded during presentations of the most preferred and the least preferred moving stimuli. From the initial delay range of the autocorrelation function (ACF) of the alpha wave, the effective duration (/spl tau//sub e/) was analyzed. Results show that the stimulus with most preferred periods has a greater value of /spl tau//sub e/ than that with least preferred periods at the occipital area, especially in the left hemisphere.

Ultrasound can be perceived through bone conduction by the profoundly deaf as well as by normal-hearing subjects. Moreover, speech signals modulated onto ultrasound can be detected through bone conduction. This study explored how well listeners can understand ultrasonic speech and the confusion patterns to evaluate and improve bone-conducted ultrasonic hearing. The intelligibility of Japanese words classified by familiarity and Japanese monosyllables with bone-conducted ultrasound was investigated. Results showed that the intelligibility of familiar words was higher than that of unfamiliar words. Further, the results of a monosyllable intelligibility test with bone-conducted ultrasound and those of a test with air-conducted sound showed a similar pattern of speech recognition with regard to the errors made. The relationship between speech intelligibility and sound level showed that the increase in the intelligibility of bone-conducted ultrasonic speech did not exceed the increase in the intelligibility of air-conducted speech as the sound level rose.

Auditory evoked magnetic fields in relation to iterated rippled noise (IRN) were examined by magnetoencephalography (MEG). IRN was used as the sound stimulus to control the peak amplitude of the autocorrelation function of the sound. The IRN was produced by a delay-and-add algorithm applied to bandpass noise that was filtered using fourth-order Butterworth filters between 400–2200 Hz. All sound signals had the same sound pressure level. The stimulus duration was 0.5 s, with rise and fall ramps of 10 ms. Ten normal-hearing subjects took part in the study. Auditory evoked fields were recorded using a 122 channel whole-head magnetometer in a magnetically shielded room. The results showed that the peak amplitude of N1m, which was found above the left and right temporal lobes around 100 ms after the stimulus onset, increased with increase in the number of iterations of the IRN. The latency and estimated equivalent current dipole (ECD) locations of N1m did not show any systematic variation as a function of the number of iterations.

We observed the brain electrical activities associated with verbal cognitive processes by measuring both EEGs and MEGs evoked by visually cognitive tasks. English words, nonsense words and random dots were presented. We discussed the source estimation at latencies of 150 msec and 360 msec using MEG data. At 150 msec, two equivalent current dipoles are localized in or near the primary visual cortex. The dipole sources for recognition of English words at 360 msec were estimated in both hemispheres, and the dipole moment in the left hemisphere was larger than the dipole moment of the right hemisphere. However, we could not find sources common to all subjects.

This report provides information on the geology and selected physical and mechanical properties of surface rocks collected at Diablo Canyon, San Luis Obispo County, California as part of the design and engineering studies towards a future reactor neutrino oscillation experiment. The main objective of this neutrino project is to study the process of neutrino flavor transformation--or neutrino oscillation--by measuring neutrinos produced in the fission reactions of a nuclear power plant. Diablo Canyon was selected as a candidate site because it allows the detectors to be situated underground in a tunnel close to the source of neutrinos (i.e., at a distance of several hundred meters from the nuclear power plant) while having suitable topography for shielding against cosmic rays. The detectors have to be located underground to minimize the cosmic ray-related background noise that can mimic the signal of reactor neutrino interactions in the detector. Three Pliocene-Miocene marine sedimentary units dominate the geology of Diablo Canyon: the Pismo Formation, the Monterey Formation, and the Obispo Formation. The area is tectonically active, located east of the active Hosgri Fault and in the southern limb of the northwest trending Pismo Syncline. Most of the potential tunnel for the neutrino detector lies within themore » Obispo Formation. Review of previous geologic studies, observations from a field visit, and selected physical and mechanical properties of rock samples collected from the site provided baseline geological information used in developing a preliminary estimate for tunneling construction cost. Gamma-ray spectrometric results indicate low levels of radioactivity for uranium, thorium, and potassium. Grain density, bulk density, and porosity values for these rock samples range from 2.37 to 2.86 g/cc, 1.41 to 2.57 g/cc, and 1.94 to 68.5% respectively. Point load, unconfined compressive strength, and ultrasonic velocity tests were conducted to determine rock mechanical and acoustic properties. The rock strength values range from 23 to 219 MPa and the Poisson's ratio from 0.1 to 0.38. Potential geologic hazards in the Diablo Canyon area were identified and described to provide an overall picture of processes that may affect tunnel construction activities.« less

The effect of frequency on N1m has been investigated by various methods. However, it has not yet been measured using forward masking. In this study, the frequency specificity of N1m was investigated using forward masking. Although the masker frequency had some influence on N1m amplitudes, the results suggested that the frequency specificity of N1m was worse than that of a single-neuron or psychological tuning curve. This is probably because N1m includes various components, both frequency-specific and non-specific, some of which may be less affected by masking. Thus, our results agree with those of previous studies using intervening tones that suggested widespread neural representation in the auditory cortex.

Electrogustometry is a convenient method to examine taste acuity in clinical situations. Some basic properties of neural activity in the cerebral cortex in response to electrogustatory stimulation were revealed by measuring magnetoencephalography (MEG) signals with a whole-cortex-type system in response to varying intensities of anodal DC currents focally applied to the tongue surface in human subjects. Independent component analysis was used to eliminate stimulus artifacts in MEG signals. Electrogustatory stimulation with intensities of induced electric taste evoked responses bilaterally, mainly in the opercular-insular cortex with a mean onset latency of approximately 350 ms, while subthreshold electrogustatory stimulation induced modest responses in the cortex. Stronger stimulation induced a tingling sensation and elicited large transient responses in both the opercular-insular and somatic sensory cortices. This is the first description of the basic properties of human MEG responses to electrogustatory stimulation.

This paper presents a study on the ultrasonic hearing aids and perception tests for both normal hearing subjects and profoundly deaf people and the active location of estimated signal sources in the brain. In these experiments auditory activities by bone-conducted ultrasonic stimuli were measured by magnetoencephalography using a 122-channel whole-head neuromagnetometer. Both normal hearing and profoundly deaf people could perceive the ultrasound stimuli; however the active center in the brain of the latter people was found in a different region (superior temporal area) from the former subjects. These results suggest the reorganization of the auditory central nervous system in humans.

Bone conduction enables ultrasound to be heard. Although several hypotheses about ultrasonic perception have been presented, the perception mechanism of bone-conducted ultrasound has not yet been established. In this study, to investigate ultrasonic perception, the amount of masking produced by 27-, 30- and 33-kHz bone-conducted ultrasonic maskers for air-conducted high-frequency sounds was measured in the frequency range of 8-18 kHz at 1-kHz intervals. The results showed that the air-conducted signals in the frequency range of 10-14 kHz were strongly masked by the ultrasonic maskers. When the masker intensity increased from 5 to 10 dB SL, the growth of masking was more than 10 dB in the frequency range of 9-15 kHz, and the masking spread strongly to lower frequencies. Furthermore, the dynamic range for bone-conducted ultrasound was clearly narrower than that for air-conducted high-frequency sounds. These results suggest that perception of bone-conducted ultrasound depends on inner hair cell activity induced by ultrasound, even without modulation being present, and does not depend on enhancement by the outer hair cells in the basal turn of the cochlea.

In this study, we investigate an estimation of internal sources with poor information about their source profile, which is important in order to analyze the higher functions of the human brain. We used a 64-channel whole-head-type SQUID system to record MEG activities evoked by visually cognitive tasks. Three kinds of stimuli were presented: English words, nonsense words, and random dot patterns. Spatially distributed internal sources with latencies between 320 and 420 msec were estimated by using a sub-optimal least-squares subspace scanning technique. From three subjects data, the following results of distributed source estimations were shown: English words stimuli activated large area, the left temporal region, the parietal and right postero-temporal region, nonsense words activated the paretal region, random dot patterns activated the frontal region.

A material and process development of a tri-level resist system is carried out to introduce the resist system into 130nm and 110nm device fabrication. The tri-level resist system consists of organic films as a bottom layer, spin-on- glass (SOG) as a middle layer and DUV photoresists as a top imaging layer. A wettability and an acidity of the SOG film are adjusted depending on the type of resist materials to obtain a desirable resist profile. The anti-reflective performance of the tri-level resist system is evaluated along with the lithographic performance. A light reflection (reflectivity) in the DUV photoresist film is reduced less than 0.5% for both KrF resist and ArF resist by choosing the nominal thickness of the SOG film and the bottom layer. A conventional DNQ-Novolak type MUV resist is used for the bottom layer in the KrF tri-level resist system. The MUV resist is thermally cured to avoid mixing with the SOG and to increase the optical density at 248nm wavelength. A newly developed spin-on-carbon film is used for the bottom layer in the ArF tri-level resist system. The spin-on-carbon has an excellent dry etch resistance because of its high carbon content (>90%). The dry etch rates of the MUV resist and the spin-on-carbon for CF4/O2/Ar etch chemistry (SiN RIE condition) are 372nm/min and 287nm/min respectively. A pattern transfer using the tri-level resist system is demonstrated for both L/S and hole structures.

A novel hearing aid system based on bone-conducted ultrasonic (BCU) hearing is being developed for use by profoundly deaf people. However, the perception mechanisms involved in BCU hearing remain unclear. In this study, the way in which the mechanical frequency characteristics of human head vibration under BCU stimulation contribute to the hearing process was considered and examined in terms of the effects of the elasticity of the surface tissue that was in contact with a bone conduction vibrator. The results suggest that head vibration under BCU stimulation has low-pass filter-type characteristics with a cut-off frequency of between 30 and 40 kHz, which is attributed to the effects of the elasticity of living human skin. However, the issue of the psychoacoustic characteristics of the BCU hearing process not necessarily reflecting the mechanical frequency characteristics of head vibration remains.

The cortical site which processes information on whole-body linear displacement is unknown. In this study, neuromagnetic responses to a visually-induced linear vection were recorded in 5 healthy, right-handed, adult subjects using a 122-channel whole cortex neuromagnetometer. We presented expanding rectangles on the screen which came into view one after another and accelerated in expanding speed at random cycle, giving the subjects the sensation of linear self motion (linear vection) through an illusory tunnel with occasional acceleration. Clear responses of magnetic fields related to the accelerative event were obtained in both hemispheres around the parietal and temporal regions. The dipole sources of the component were estimated in the cortex around the superior temporal sulcus, insula and medial superior temporal area. Some parts of these regions may have been comprised in the vestibular cortex, suggesting that it processes the sensation of linear self motion and plays an important role in space perception.

Extensional wave attenuation and velocity measurements on a high permeability Monterey sand were performed over a range of gas saturations for imbibition and degassing conditions. These measurements were conducted using extensional wave pulse propagation and resonance over a 1-9 kHz frequency range for a hydrostatic confining pressure of 8.3 MPa. Analysis of the extensional wave data and the corresponding X-ray CT images of the gas saturation show strong attenuation resulting from the presence of the gas (Q{sub E} dropped from 300 for the dry sand to 30 for the partially-saturated sand), with larger attenuation at a given saturation resulting from heterogeneous gas distributions. The extensional wave velocities are in agreement with Gassmann theory for the test with near-homogeneous gas saturation and with a patchy saturation model for the test with heterogeneous gas saturation. These results show that partially-saturated sands under moderate confining pressure can produce strong intrinsic attenuation for extensional waves.

Summary Much of the effort to date on fracture detection and characterization has focused on methods based on an equivalent anisotropy descriptions of the fractured rock mass. However, with the growing use of downhole receiver arrays and higher frequency sources, new prospects may emerge for imaging discrete fractures and fractured zones. This paper examines the seismic signatures of an open, fluid-filled fracture numerically, and outlines an approach for elastic, prestack reverse-time migration of VSP data for imaging fractures. The results of this study highlight the importance of incorporating fracture-generated converted waves into the imaging method, and presents an alternate imaging condition that can be used in elastic reverse-time migration when a direct wave is recorded (e.g., crosswell and VSP acquisition geometries).

It is well known that introduction of a crack-like defect into a structure reduces its stiffness and results in a corresponding downward shift in resonance frequencies. This result is consistent with the Rayleigh-Ritz formulation, which predicts that a reduction in stiffness will decrease resonance frequencies for negligibly small perturbations in mass. Techniques based on frequency shifts and mode shape analysis are being investigated to determine their feasibility for characterizing defects in adhesive-bonded joints in automotive structures. Although counter intuitive, it has been observed that a structure containing a defective joint sometimes exhibits higher resonance frequencies for some modes than a structure with an undamaged joint. Such results have been observed in laboratory experiments on aluminum plates with adhesive-bonded T-joints, and in finite-element simulations for a variety of structures. In all cases, the defects are gaps in the adhesive layer of the joints. While the reduction in mass is very small, it appears that the mass effect can sometimes overwhelm the frequency-decreasing effect of the reduced stiffness. Such behavior depends on the location of the defect, and is speculated to occur when the mode shape corresponding to the frequency is very sensitive to the mass (inertia) but relatively insensitive to the change in stiffness.