1. Listeners use direction-dependent spectral cues introduced by the torso, head, and pinnae to localize the source of a sound in space. Among the prominent direction-dependent spectral features in the free field-to-eardrum transfer function are narrow regions of low acoustic energy referred to as spectral notches. In this paper, we ...

INTRODUCTION: We present simulations of extracellular potential patterns elicited by delivering ectopic stimuli to a parallelepipedal slab of ventricular tissue represented as an anisotropic bidomain incorporating epi-endocardial fiber rotation. METHODS AND RESULTS: Simulations were based on an eikonal model that determines wavefront shapes throughout the slab at every time instant ...

1. Single-fiber responses to sinusoidally amplitude-modulated (AM) tones were recorded from the cochlear nerves of anesthetized guinea pigs. Stimuli were presented at the fiber's characteristic frequency (CF) and covered the intensity range between the fiber's minimum rate threshold and 90-100 dB SPL in 5- or 6-dB steps. The amount of ...

The cable model for electrical stimulation near the terminal of a passive fiber is derived for excitation by an arbitrary, time-varying, applied extracellular field. Unless the termination impedance is comparable to that of mammalian node of Ranvier, the end-conditions require the longitudinal intracellular current at the fiber terminal to be ...

How a neuron finds its synaptic target is one of the key questions of developmental neurobiology. It is a problem that must, at least in part, be explained in molecular terms. In light of this, several groups have recently examined the synapses that are made between individual motoneurons and muscle ...

The courses and terminal patterns of the fasciculus retroflexus (FR) in the interpeduncular nucleus (IP) were studied in the mouse, using the rapid Golgi method. Mainly on the basis of the distribution areas and terminal patterns, the FR fibers are divided into two types. The type 1 FR fibers are ...

Discharge patterns of single eighth nerve fibers in the bullfrog, Rana catesbeiana, were analyzed in response to signals consisting of multiple harmonics of a common, low-amplitude fundamental frequency. The signals were chosen to reflect the frequency and amplitude spectrum of the bullfrog's species-specific advertisement call. The phase spectrum of the ...

Glutaraldehyde-crosslinked bovine pericardium is widely used in bioprosthetic heart valve fabrication. In an attempt to set a scientific basis for more reproducible tissue selection, we produced and analyzed topographical maps of glutaraldehyde-treated bovine pericardium. Whole pericardia were divided into specific anatomical areas and their thickness was measured and mapped on ...

1. OR nurses must be alert to the problem of breakage of the light-carrying fibers inside the scope. As the number of intact fibers in the bundle decreases, the amount of light through the scope decreases, resulting in an unsatisfactory picture on the monitor. 2. Fiber-optic lights, like surgical lights, ...

The aim of this investigation was to study the influence of probe design on the signal output from the dental pulp in experiments with laser Doppler flowmetry (LDF). Eighteen patients 14 to 39 years of age were examined. Recordings were made from a maxillary and a mandibular central incisor and ...

We demonstrate two simple and inexpensive methods of using the force exerted by the light transmitted through an optical fiber to center a lens on the fiber core with submicrometer accuracy. By choosing the appropriate lens one can either focus, collimate, or defocus the light emerging from the fiber. We ...

Electrical stimulation of an ascending path of the locus ceruleus-norepinephrine system was used to elicit release of norepinephrine at noradrenergic terminal fields of the rat thalamus. Overflow into the extracellular fluid space was measured by fast in vivo chronoamperometry. At pretreated carbon fibers, the electrochemical signal consists of a sharp ...

1. Activity of individual eight nerve fibers in the bullfrog, Rana catesbeiana, was measured in response to complex, multiple-frequency stimuli differing in both frequency composition and harmonic structure. Stimuli were chosen to parallel types of stimuli producing "pitch-shift" effects in humans. 2. The fundamental frequency of harmonic stimuli can be ...

The purpose of this investigation was to clarify the detailed histological structure of the human larynx and to clarify the cause of adaptation in high-frequency vibrations using three-dimensional histological reconstructions of human true vocal cords. In a first series of studies, 54 intact adult larynges were obtained from 398 human ...

Phenomena seen in axons exposed to subblocking doses serve as the basis for interpreting clinical and behavioral observations during onset and recovery of peripheral nerve block. To delineate the changes in excitability and in impulse conduction caused by subblocking concentrations of local anesthetics (LAs) in myelinated peripheral nerve fibers, LAs ...

1. The two main types of lateral line organs of lower vertebrates are the superficial neuromasts (SN), with a cupula that protrudes in the surrounding water, and the canal neuromasts (CN), located in the lateral line canal. The scales of the trunk lateral line canal of fish contain SNs as ...

Direction-dependent changes in frequency selectivity were documented in three populations of neurons in the auditory periphery of the leopard frog: low-, mid-, and high-frequency sensitive fibers. These changes were most pronounced in the mid-frequency (720-1199 Hz) sensitive fibers which exhibited positive shifts in characteristic frequencies (CFs) and concomitant narrowed bandwidths ...

We present a new form of all-fiber frequency shifter based on the use of an all-fiber ring resonator as a high-resolution filter illuminated by a phase-modulated input beam. The configuration offers a frequency-tunable output with complete suppression of the unshifted light component and extremely high suppression of unwanted sidebands. A ...

Results are presented of a study of a fiber reflection Mach-Zehnder interferometer that is based on identical couplers. It has been found that, for couplers having splitting ratios within a certain range, it is always possible to switch all the light between transmission and reflection by varying the interferometer phase ...

The effects of collagen fiber orientation and osteon geometry on the mechanical properties of secondary osteons under axial compression/tension and combined loadings (compression, bending and torsion) were investigated using a composite-beam finite-element model. Three cross-sectional shapes of secondary osteons were studied to show the effect of geometry. The results of ...

In a sheep model the posterior cruciate ligament (PCL) was replaced by a patellar tendon autograft (PTAG) using the central one-third of the ipsilateral patellar tendon (PT). The sheep were sacrificed at 16, 26, 52 and 104 weeks postoperation. The PTAG, and, as controls, the contralateral PCL and PT were ...

Various optical methods for assessing the retinal nerve fiber layer (RNFL) depend on reflected light, but little is known about the characteristics of the RNFL as a reflecting structure. The authors investigated the angular dependence of light reflected by the unmyelinated nerve fibers of the toad eyecup using a small ...

Cochlear nerve discharge patterns in response to the synthesized consonant-vowel stimulus /da/ were collected from a population of 223 auditory-nerve fibers from a single cat. For each nerve fiber, discharges were measured from multiple, independent stimulus presentations, with the means and variances of the post-stimulus time histograms and Fourier transforms ...

Recent studies in the bird ear have shown that degenerated hair cells are sometimes replaced by regenerated receptor cells. The present study evaluated the adult mammalian cochlea for evidence of hair-cell and nerve-fiber regeneration. Eighty-eight noise-damaged chinchilla cochleas were examined as plastic-embedded whole mounts by phase-contrast and bright-field microscopy. No ...

A population study of auditory nerve responses in the bullfrog, Rana catesbeiana, analyzed the relative contributions of spectral and temporal coding in representing a complex, species-specific communication signal at different stimulus intensities and in the presence of background noise. At stimulus levels of 70 and 80 dB SPL, levels which ...

The diaphragmatic central tendon (DCT), a collagenous soft tissue membrane, acts as a mechanical buffer between the costal and crural muscles. Its direction of mechanical anisotropy has been shown to correspond to the collagen fiber preferred directions. These preferred directions were determined by gross histological examination, and were thus qualitative. ...

Peripheral A-delta and C fibers are activated during the production of ischemic or tourniquet pain; however, individual metabolic or molecular factors responsible for neural activation are not known. To elucidate these mechanisms the in vitro corneal nerve preparation was used. Electrophysiologic effects of individual metabolic perturbations associated with ischemia (hypoxia, ...

We have investigated the effects of electric field stimulation on membrane repolarization in rabbit papillary muscles and assessed the consequences of these effects for the dispersion of intracellular potentials and the production of a propagation wave front or unidirectional block in relatively refractory tissue. The stimuli studied had electric field ...

This investigation compared the transverse strengths of three denture base resins with and without polyethylene reinforcement fibers. These fibers were incorporated in 10 specimens each of a high-impact strength resin, a rapid heat-polymerized resin, and a light-activated resin. Each specimen was broken on an Instron universal testing machine using a ...

The activity of auditory-nerve fibers was recorded in anesthetized cats in response to sinusoidal electric stimuli applied through a bipolar electrode pair inserted about 5 mm into the cochlea through the round window. The synchronization index was calculated from period histograms for frequencies ranging from 0.2 to over 10 kHz. ...

Temperature change and hypoxia produce consistent, reversible effects on the response of single auditory nerve fibers in the goldfish. Cooling and hypoxia produce reductions of a cell's spontaneous activity, sensitivity, most excitatory or best frequency (BF) at a given signal level, and overall responsiveness to acoustic stimulation. Warming above ambient ...

Regional differences in the architecture and size of lateral line canals and neuromasts were measured in an Antarctic fish, Trematomus bernacchii, and the data were used in models of canal and cupular mechanics to predict the frequency response of these two peripheral structures. These modeled predictions were then compared to ...

A liquid-level sensor, consisting of three optical fibers, is described. A light is projected onto an oil surface through a transmitting fiber. A receiving fiber picks up the light reflected from the oil surface. A reference fiber transmits the light from a light-emitting diode back and forth along the same ...

Spinal isolation (SI), i.e., the isolation of the lumbar spinal cord via a rostral and a caudal cord transection and bilateral dorsal rhizotomy, was used to determine the effects of chronic (6 months) inactivity on the size and metabolic properties of fibers in the cat soleus. Fibers were classified as ...

This paper summarizes animal experiments and in vitro data carried out to study the oncogenic effects of asbestos fibers on mesothelial cells. An interpretation of the results is made in light of current statements on the carcinogenicity of asbestos fibers. Experimental results appear to show that the carcinogenicity of mineral ...

We have examined the activity patterns of single auditory-nerve fibers in the chicken and tested for possible changes during post-hatching development. For this purpose, we recorded from fibres in the cochlear ganglion of chickens of two age groups (about P2 and P21) and investigated their spontaneous and sound-evoked activity patterns ...

To facilitate improvement of investigations on the distribution of mossy fibers in the hippocampal formation, a method is described using Timm's stained preparations after methacrylate embedding with the hydrophilic resin, Quetol 523M. Fixation with a mixture of formaldehyde and glutaraldehyde yielded satisfactory staining results and good structural preservation. During the ...

Responses of auditory-nerve fibers in anesthetized cats to nine different spoken stop- and nasal-consonant/vowel syllables presented at 70 dB SPL in various levels of speech-shaped noise [signal-to-noise (S/N) ratios of 30, 20, 10, and 0 dB] are reported. The temporal aspects of speech encoding were analyzed using spectrograms. The responses ...

The use of bioluminescence as a sensitive marker for detection of Pseudomonas spp. in the rhizosphere was investigated. Continuous expression of the luxCDABE genes, required for bioluminescence, was not detectable in the rhizosphere. However, when either a naphthalene-inducible luxCDABE construct or a constitutive luxAB construct (coding only for the luciferase) ...

The responses of single cat auditory-nerve fibers to naturally spoken voiced sounds (the vowels [a, i, u] and the murmur [m]) presented at normal intensity (70 dB SPL) in various levels of speech-shaped noise were analyzed for the encoding of the glottal-pulse (fundamental) period. To quantify the strength of this ...

The immediate effects of different power densities and light dosages were determined on 77 sites of endobronchial tumors in 28 patients. All received 2 mg/kg of dihematoporphyrin ether 2 days prior to photodynamic therapy (PDT). Light (630 nm) was delivered with a tunable dye laser system through quartz fibers modified ...

Fiber optic Fabry-Perot sensors have been developed whose optical reflectance varies with optical cavity depth (pressure) or with change in a material's refractive index (temperature). These sensors employ a unique combination of features: they are interrogated by an LED; they are designed to operate within a single reflectance cycle; and ...

Germanium-doped silica fibers were prepared for frequency doubling of 1.06-microm wavelength radiation under the simultaneous presence of the first, second, and fourth harmonics of the laser light. It was found that the preparation rate for frequency doubling was dramatically increased by the presence of the fourth harmonic. The experiments also ...

A new low-cost strain measurement system has been developed for the mechanical testing of biological soft tissues. The technique creates four spots of light on a tissue sample surface by piercing the tissue sample with two pairs of small light-conducting optical fibers (one pair for each axis of a biaxial ...

We present seismic and auditory frequency tuning curves of individual bullfrog, Rana catesbeiana, saccular and amphibian papilla axons that responded to both seismic and auditory stimuli. In this study we found: 1) most saccular axons respond well to auditory stimuli with moderate signal strength (50-70 dB SPL) as well as ...

The NaOH cell-maceration method was applied to the oral surface of the mouse soft palate to demonstrate the tridimensional architecture of the connective tissue papillae (CTP) of the "palatal papillae", and of the openings of the glandular ducts. The CTP of the palatal papillae extremely differed from those of any ...

We determined the effects on atrioventricular (AV) conduction of changing the spatial dispersion of acetylcholine (ACh) release from vagal nerve fibers in anesthetized dogs. We paced the atria at a constant rate and stimulated the vagus nerves with one stimulus burst per cardiac cycle. We varied the spatial heterogeneity of ...

A composite model of the auditory periphery, based upon a unique analysis technique for deriving filter response characteristics from cat auditory-nerve fibers, is presented. The model is distinctive in its ability to capture a significant broadening of auditory-nerve fiber frequency selectivity as a function of increasing sound-pressure level within a ...

Normal human left ventricular architecture comprises a highly aligned array of cardiac myofibers whose orientation depends on transmural location. This study was designed to determine whether measurement of integrated backscatter could be used detect the progressive transmural shift of myofiber alignment that occurs from epicardium to endocardium in human ventricular ...

The purpose of this study was to determine the temporal and spatial gradients in the innervation of the chicken cochlea, the basilar papilla, as it develops in the early embryo. A series of white Leghorn chick embryos (Hamburger-Hamilton Stage 20-43) were prepared for serial sectioning and stained by Toluidine blue ...