Search

General rigid bead-rod theory yields uniquely the relation between macromolecular architecture and complex viscosity. For this, it relies on the analytical solution of the general diffusion equation for small-amplitude oscillatory shear flow of Bird et al. [Dynamics of Polymeric Liquids, 2nd ed. (Wiley, New York, 1987), Vols. 1–2]. Unfortunately, this general diffusion equation has yet to be solved for any other flow field. In this paper, we do so for steady-shear material functions, namely, viscosity and first normal stress coefficient. We, thus, explain the non-Newtonian behaviors of macromolecular suspensions of any axisymmetric design in steady-shear flow. [ABSTRACT FROM AUTHOR]

Microfluidic design, fabrication, and experiments have developed rapidly, leading to lab-on-chip separation or fractionation. In this work, we design a continuous concentrator for macromolecular solutions. Our design relies on the analytical solutions for orientational diffusion under laminar pressure-driven slot flow through a microchannel [W. Stasiak and C. Cohen, "Dilute solutions of macromolecules in a rectilinear Poiseuille flow," J. Chem. Phys. 78, 553 (1983)]. Using rigid dumbbell theory, we provide analytical solutions for the design of our microfluidic macromolecular hydrodynamic chromatography. We arrive at our design through the use of well-known confinement-driven composition profiles. Using a pair of razor-sharp blades, our design separates the slot flow into a symmetric core inner slot (concentrated) between two outer slots (diluted). We discover a minimum dimensionless blade leading edge separation for complete fractionation, and that this decreases with confinement and also decreases with dimensionless shear rate. [ABSTRACT FROM AUTHOR]

One good way to explain the elasticity of a polymeric liquid is to just consider the orientation distribution of the macromolecules. When exploring how macromolecular architecture affects the elasticity of a polymeric liquid, we find the general rigid bead–rod theory to be both versatile and accurate. This theory sculpts macromolecules using beads and rods. Whereas beads represent points of Stokes flow resistances, the rods represent rigid separations. In this way, how the shape of the macromolecule affects its rheological behavior in suspension is determined. Until recently, general rigid bead–rod theory has neglected interferences of the Stokes flow velocity profiles between nearby beads. We call these hydrodynamic interactions, and we here employ our new method for exploring how these interactions affect the complex viscosity of suspensions of multi-bead rods. These multi-bead rods are also called shish-kebabs. We use the center-to-center distance between adjacent beads as the characteristic length. We proceed analytically, beginning with a geometric expression for the shish-kebab bead positions. Our analytical solution for the complex viscosity presents as one for N = 3 , 5 , 6 , 7 , 8 , ... , one for N = 4 , and another for the rigid dumbbell, N = 2. We find that for shish-kebabs, hydrodynamic interactions (i) increase zero-shear viscosity, (ii) increase zero-shear first normal stress coefficient, (iii) decrease the real part of the dimensionless complex viscosity, and (iv) increase minus the dimensionless imaginary part. We find that the combination of (iii) and (iv) explains crossovers of the parts of the complex viscosity. We further find that for a monodisperse polystyrene solution, the general rigid bead–rod theory with hydrodynamic interaction, for both parts of the complex viscosity, provides stunning improvement over without. [ABSTRACT FROM AUTHOR]

Chains of mechanically interlocking or intersecting organic rings, called poly[ n ]catenanes, afford interesting opportunities to study the role of orientation in suspensions. We call poly[ 5 ]catenanes olympiadanes. In this work, we use general rigid bead-rod theory to arrive at general expressions, from first principles, for the complex viscosity of poly[ n ]catenane suspensions. General rigid bead-rod theory relies entirely on suspension orientation to explain the elasticity of the liquid. We obtain analytical expressions for the complex viscosity of poly[n]catenanes for both n even and odd, for both mechanically interlocking and intersecting rings, and for identically sized rings. We restrict our analysis to evenly spaced poly[n]catenanes of orthogonal adjacency. We find that the parts of the complex viscosity for intersecting and interlocking rings, when made dimensionless with the polymer contribution to the zero-shear viscosity, match. We find good agreement with the available complex viscosity measurements for molten intersecting polystyrene poly[1,3]catenanes, but not so for poly[2]catenanes. We next calculate space filling equilibrium structures of these poly[ 1 – 3 ]catenanes, only to discover that each polystyrene ring looks more like a bead. We find that, for these polystyrene poly[ n ]catenanes and for good agreement with the available complex viscosity measurements, the shish-kebab theory suffices. [ABSTRACT FROM AUTHOR]

The complex viscosity of planar star-branched polymers has been derived from general rigid bead-rod theory, but only for singly-beaded arms. Here, we explore the respective roles of branch functionality, arm length, and nonplanar arrangements, analytically from general rigid bead-rod theory. For nonplanar, we include polyhedral, both regular and irregular. Further, for all structures, we compare with and without the central bead. We fit the theory to complex viscosity measurements on polybutadiene solutions, one quadrafunctional star-branched, the other unbranched, of the same molecular weight ( M w = 200 000 g / gmol). We learn that when general rigid bead-rod theory is applied to quadrafunctional polybutadiene, a slightly irregular center-beaded tetrahedron of interior angle 134° is required (with 1 360 000 g / gmol per bead) to describe its complex viscosity behavior. [ABSTRACT FROM AUTHOR]

Atomically thin flat sheets of carbon, called graphene, afford interesting opportunities to study the role of orientation in suspensions. In this work, we use general rigid bead-rod theory to arrive at general expressions from first principles for the complex viscosity of graphene suspensions. General rigid bead-rod theory relies entirely on suspension orientation to explain the elasticity of the liquid. We obtain analytical expressions for the complex viscosity of triangular and hexagonal graphene sheets of arbitrary size. We find good agreement with new complex viscosity measurements. [ABSTRACT FROM AUTHOR]

Whereas much is known about the complex viscosity of polymeric liquids, far less is understood about the behavior of this material function when macromolecules are confined. By confined, we mean that the gap along the velocity gradient is small enough to reorient the polymers. We examine classical analytical solutions [O. O. Park and G. G. Fuller, "Dynamics of rigid and flexible polymer chains in confined geometries. II. Time-dependent shear flow," J. Non-Newtonian Fluid Mech. 18, 111–122 (1985)] for a confined rigid dumbbell suspension in small-amplitude oscillatory shear flow. We test these analytical solutions against the measured effects of confinement on both parts of the complex viscosity of a carbopol suspension and three polystyrene solutions. From these comparisons, we find that both parts of the complex viscosity decrease with confinement and that macromolecular orientation explains this. We find the persistence length of macromolecular confinement, L p , to be independent of both λ ω and λ γ ̇ 0 . [ABSTRACT FROM AUTHOR]

Empirically, we find that the parametric plots of the imaginary vs real parts of the complex viscosity may depend neither on temperature nor on average molecular weight. Moreover, for a fixed polydispersity, these viscosity Cole–Cole curves amplify both rightward and upward with long-chain branching content. In this paper, we find that general rigid bead–rod theory [O. Hassager, "Kinetic theory and rheology of bead–rod models for macromolecular solutions. II. Linear unsteady flow properties," J. Chem. Phys. 60(10), 4001–4008 (1974)] can explain these rightward and upward amplifications. We explore the effects of branching along a straight chain in small-amplitude oscillatory shear flow. Specifically, we explore the number of branches, branch length, branch position, and branch distribution. [ABSTRACT FROM AUTHOR]

To assess how flow affects school structure and threat detection, startle response rates of solitary and small groups of giant danio Devario aequipinnatus to visual looming stimuli were compared in flow and no-flow conditions. The instantaneous position and heading of each D. aequipinnatus was extracted from high-speed videos. Behavioural results indicate that (1) school structure is altered in flow such that D. aequipinnatus orient upstream while spanning out in a crosswise direction, (2) the probability of at least one D. aequipinnatus detecting the visual looming stimulus is higher in flow than no flow for both solitary D. aequipinnatus and groups of eight D. aequipinnatus; however, (3) the probability of three or more individuals responding is higher in no flow than in flow. These results indicate a higher probability of stimulus detection in flow but a higher probability of internal transmission of information in no flow. Finally, results were well predicted by a computational model of collective fright response that included the probability of direct detection (based on signal detection theory) and indirect detection ( i.e. via interactions between group members) of threatening stimuli. This model provides a new theoretical framework for analysing the collective transfer of information among groups of fishes and other organisms. [ABSTRACT FROM AUTHOR]

Rheotaxis is a robust, multisensory behavior with many potential benefits for fish and other aquatic organisms. Visual (optic flow) cues appear to be sufficient for rheotaxis, but other sensory cues can clearly compensate for the loss of vision. Nevertheless, the nature of multisensory interactions and the relative contributions of different senses under varying conditions are poorly understood - largely because there is so little description of the actual behavior. Here, we examined the effects of different flow speeds and different sensory conditions on the spatiotemporal dynamics of rheotaxis. Although the overall ability of giant danio (Devario aequipinnatus) to head upstream is largely unaffected by either unimodal or bimodal deprivation of visual and/or lateral line senses, the spatiotemporal form of the behavior is altered in subtle ways. When deprived of vision, fish move further upstream, but the angular accuracy of the upstream heading is reduced. In addition, visually deprived fish exhibit left/right sweeping movements near the upstream barrier at low flow speeds. Sweeping movements are abolished when these fish are additionally deprived of lateral line information. These results indicate that fish adopt different sensorimotor strategies to compensate for the loss of one or more senses and that the nature of multisensory interactions is a complex function of flow speed. [ABSTRACT FROM AUTHOR]

Results from sampling for sardine (Sardina pilchardus) eggs at station L4 in the coastal Western English Channel over the period 1988–2008 are presented and discussed in relation to environmental conditions. As previously observed in this area, there is a summer spawning season (mid-March to early July) and one in the autumn (early September to mid-November). The historical trend for increasing autumn spawning has continued. The mean spawning temperatures were 12.6 and 14.5°C for the summer and autumn seasons, respectively. Temperature was negatively correlated with summer egg abundance and positively with autumn egg abundance. A negative correlation between egg abundance and the North Atlantic Oscillation index suggested a link between egg numbers and plankton production. [ABSTRACT FROM PUBLISHER]

Two pairs of degenerate primers were designed from sequences within the potyviral CI (CIFor/CIRev) and HC-Pro-coding regions (HPFo/HPRev), and these were shown to be highly specific to members of the genus Potyvirus. Using the CIFor and CIRev primers, three novel potyviruses infecting crop and weed species from Vietnam were detected, namely telosma mosaic virus (TelMV) infecting telosma ( Telosma cordata, Asclepiadaceae), peace lily mosaic virus (PeLMV) infecting peace lily ( Spathiphyllum patinii, Araceae) and wild tomato mosaic virus (WTMV) infecting wild tomato ( Solanum torvum, Solanaceae). The fragments amplified by the two sets of primers enabled additional PCR and complete genomic sequencing of these viruses and a banana bract mosaic virus (BBrMV) isolate from the Philippines. All four viruses shared genomic features typical of potyviruses. Sequence comparisons and phylogenetic analyses indicated that WTMV was most closely related to chilli veinal mottle virus (ChiVMV) and pepper veinal mottle virus (PVMV), while PeLMV, TelMV and BBrMV were related to different extents to members of the bean common mosaic virus (BCMV) subgroup. [ABSTRACT FROM AUTHOR]

Oil shale processing produces an aqueous wastewater stream known as retort water. The fate of the organic content of retort water from the Stuart oil shale project (Gladstone, Queensland) is examined in a proposed packed bed treatment system consisting of a 1:1 mixture of residual shale from the retorting process and mining overburden. The retort water had a neutral pH and an average unfiltered TOC of 2,900 mg l-1. The inorganic composition of the retort water was dominated by NH4+. Only 40% of the total organic carbon (TOC) in the retort water was identifiable, and this was dominated by carboxylic acids. In addition to monitoring influent and effluent TOC concentrations, CO2 evolution was monitored on line by continuous measurements of headspace concentrations and air flow rates. The column was run for 64 days before it blocked and was dismantled for analysis. Over 98% of the TOC was removed from the retort water. Respirometry measurements were confounded by CO2 production from inorganic sources. Based on predictions with the chemical equilibrium package PHREEQE, approximately 15% of the total CO2 production arose from the reaction of NH4+ with carbonates. The balance of the CO2 production accounted for at least 80% of the carbon removed from the retort water. Direct measurements of solid organic carbon showed that approximately 20% of the influent carbon was held-up in the top 20cm of the column. Less than 20% of this held-up carbon was present as either biomass or as adsorbed species. Therefore, the column was ultimately blocked by either extracellular polymeric substances or by a sludge that had precipitated out of the retort water. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to provide the core description of the modelling exercise within the Shelf Edge Advection Mortality And Recruitment (SEAMAR) programme. An individual-based model (IBM) was developed for the prediction of year-to-year survival of the early life-history stages of mackerel (Scomber scombrus) in the eastern North Atlantic. The IBM is one of two components of the model system. The first component is a circulation model to provide physical input data for the IBM. The circulation model is a geographical variant of the HAMburg Shelf Ocean Model (HAMSOM). The second component is the IBM, which is an i-space configuration model in which large numbers of individuals are followed as discrete entities to simulate the transport, growth and mortality of mackerel eggs, larvae and post-larvae. Larval and post-larval growth is modelled as a function of length, temperature and food distribution; mortality is modelled as a function of length and absolute growth rate. Each particle is considered as a super-individual representing 106 eggs at the outset of the simulation, and then declining according to the mortality function. Simulations were carried out for the years 1998–2000. Results showed concentrations of particles at Porcupine Bank and the adjacent Irish shelf, along the Celtic Sea shelf-edge, and in the southern Bay of Biscay. High survival was observed only at Porcupine and the adjacent shelf areas, and, more patchily, around the coastal margin of Biscay. The low survival along the shelf-edge of the Celtic Sea was due to the consistently low estimates of food availability in that area. [ABSTRACT FROM AUTHOR]

An individual-based model (IBM) for the simulation of year-to-year survival during the early life-history stages of the north-east Atlantic stock of mackerel (Scomber scombrus) was developed within the EU funded Shelf-Edge Advection, Mortality and Recruitment (SEAMAR) programme. The IBM included transport, growth and survival and was used to track the passive movement of mackerel eggs, larvae and post-larvae and determine their distribution and abundance after approximately 2 months of drift. One of the main outputs from the IBM, namely distributions and numbers of surviving post-larvae, are compared with field data as recruit (age-0/age-1 juveniles) distribution and abundance for the years 1998, 1999 and 2000. The juvenile distributions show more inter-annual and spatial variability than the modelled distributions of survivors; this may be due to the restriction of using the same initial egg distribution for all 3 yr of simulation. The IBM simulations indicate two main recruitment areas for the north-east Atlantic stock of mackerel, these being Porcupine Bank and the south-eastern Bay of Biscay. These areas correspond to areas of high juvenile catches, although the juveniles generally have a more widespread distribution than the model simulations. The best agreement between modelled data and field data for distribution (juveniles and model survivors) is for the year 1998. The juvenile catches in different representative nursery areas are totalled to give a field abundance index (FAI). This index is compared with a model survivor index (MSI) which is calculated from the total of survivors for the whole spawning season. The MSI compares favourably with the FAI for 1998 and 1999 but not for 2000; in this year, juvenile catches dropped sharply compared with the previous years but there was no equivalent drop in modelled survivors. [ABSTRACT FROM AUTHOR]

Measurements were made of the density and settling velocity of eggs of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus), using a density-gradient column. These results were related to observed vertical distributions of eggs obtained from stratified vertical distribution sampling in the Bay of Biscay. Eggs of both species had slightly positive buoyancy in local seawater throughout most of their development until near hatching, when there was a marked increase in density and they became negatively buoyant. The settling velocity of anchovy eggs, which are shaped as prolate ellipsoids, was close to predictions for spherical particles of equivalent volume. An improved model was developed for prediction of the settling velocity of sardine eggs, which are spherical with a relatively large perivitelline volume; this incorporated permeability of the chorion and adjustment of the density of the perivitelline fluid to ambient seawater. Eggs of both species were located mostly in the top 20 m of the water column, in increasing abundance towards the surface. A sub-surface peak of egg abundance was sometimes observed at the pycnocline, particularly where this was pronounced and associated with a low-salinity surface layer. There was a progressive deepening of the depth distributions for successive stages of egg development. Results from this study can be applied for improved plankton sampling of sardine and anchovy eggs and in modelling studies of their vertical distribution. [ABSTRACT FROM AUTHOR]

This work presents the results of the nanostructural characterisation of the effect of sucrose as a template added to a sol derived from a tetraethoxysilane acid catalysed process. By increasing the sucrose template ratio, N2 adsorption isotherms showed that the xerogel samples changed from a micropore to a mesopore nanostructure as evidenced by the formation of hysteresis at 0.5 partial pressure. In turn, this led to a direct increase in surface areas, pore volumes and average pore sizes. Sucrose has two molecular components of the same molecular weight: D-fructose and D-glucose. D-fructose resulted in the formation of higher pore volumes and pore sizes, while D-glucose formed higher surface area xerogels. Depending of the template ratio employed in the xerogel synthesis, average pore radius ranged from 8.8 to 26 Å, while surface areas increased by over two fold up to 750 m2·g−1. However, pore volumes increased by as much as six fold, from 0.15 to almost 1 cm3·g−1. [ABSTRACT FROM AUTHOR]

Discusses how, as part of a "European Sardine/Anchovy Recruitment Program" (SARP), sardine larvae (Sardina pilchardus) were sampled off the Atlantic coast of Spain through the spawning season from March to June.

To test the hypothesis that spatial excitation patterns along the lateral-line system underlie source localization, we videotaped the orientation behavior of blinded mottled sculpin in response to a small dipole source (50-Hz vibrating sphere) before and after unilateral denervation of the lateral line system on different body regions (head, trunk and head + trunk). Approach pathways were qualitatively similar to those followed by normal intact animals. Abnormal behavior (turning in circles) was not observed. However, the frequency with which fish placed their intact side facing the source increased by 12–89%, depending on the denervation site. The angular accuracy of orientation decreased by 20° to 60° (100% to 370% change) depending on source location and region of lateral line denervated. Deficits tended to be site-specific. For example, unilaterally denervating lateral-line organs on the head resulted in less accurate orienting responses when the source was located on the denervated side of the head, but not on the opposite side of the head or on either side of the trunk. Site-specific deficits and the absence of abnormal approach pathways argue that animals are relying on a point-by-point spatial representation of source location along the sensory surface rather than computations based on bilateral comparisons. [ABSTRACT FROM AUTHOR]

Extracellular recording techniques were used to record the responses of medial nucleus cells and posterior lateral line nerve fibers in mottled sculpin, Cottus bairdi, and goldfish, Carassius auratus, to a 50-Hz dipole source (vibrating sphere). Responses were characterized in terms of (1) receptive fields that relate responsiveness (spike rate and phase-locking) to the location of the source along the length of the fish, (2) input-output functions that relate responsiveness to vibration amplitude for a fixed source location, and (3) peri-stimulus time histograms that relate responsiveness to time during a sustained period of vibration. Relative to posterior lateral line nerve fibers, medial nucleus cells in both species were similar in showing (1) lower spontaneous and evoked rates of spike activity, (2) greater degrees of adaptation, (3) greater heterogeneity in all response characteristics, and (4) evidence for inhibitory/excitatory interactions. Whereas receptive fields of nerve fibers in both species faithfully reflect both pressure gradient amplitudes (with rate changes) and directions (with phase-angle changes) in the stimulus field, receptive fields of medial nucleus were more difficult to relate to the stimulus field. Some, but not all, receptive fields could be modeled with excitatory center/inhibitory surround and inhibitory center/excitatory surround organizations. [ABSTRACT FROM AUTHOR]

Fish eggs and larvae were analysed from 63 vertically stratified plankton hauls in the Irish Sea and southern North Sea. The dominant species were sprat (Sprattus sprattus), dragonet (Callionymus spp.), dab (Limanda limanda) and to a lesser extent rockling species, sandeel (Ammodytes spp.), whiting (Merlangius merlangus) and flounder (Platichthys flesus). There was little difference between species in the vertical distribution of either eggs or larvae. Most were concentrated in the upper 50 m of the water column, eggs in progressively increasing numbers towards the surface and larvae with a sub-surface peak at a depth of 10–15 m. The vertical distribution of eggs extended deeper in the water column than larvae, possibly due to some combination of eggs being spawned deeper and their passive susceptibility to turbulent mixing. There were no significant differences between day and night distributions and under mixed or isothermal conditions. [ABSTRACT FROM PUBLISHER]

Larvae of sprat (Sprattus sprattus) from mixed and stratified water column sites in the German Bight of the North Sea were assessed for nutritional condition by analysis of total carbon and nitrogen and the lipid fractions triacylglycerol (TAG), cholesterol, and polar lipids. There was no indication of any significant variation in condition index related to diel sampling periodicity, based either on percentage carbon composition or TAG/cholesterol ratio. Inclusion of growth data from otolith ring counts with the carbon and lipid results identified larvae at 9-10 mm in length as being in relatively poor condition. There was some evidence from carbon analysis to suggest that larvae in poor condition were more prevalent at the stratified site than the mixed; however, microzooplankton analysis showed mean food abundance for larvae was slightly higher at the mixed site. The results from the condition analyses and the validity of the methods is discussed in relation to studies of survival of fish larvae. [ABSTRACT FROM PUBLISHER]

A numerical circulation and transport model system was used to simulate the dispersion of larvae of blue whiting, Micromesistius poutassou (Risso) in the eastern North Atlantic. The area of the model extends from the northern Bay of Biscay to the Norwegian Sea and covers the shelf-edge and adjacent waters at a horizontal resolution of around 20 km in 16 vertical layers. Larval input data were based on the long-term mean distribution, abundance and seasonal occurrence of larvae, derived from historical information. The circulation model was run using tidal forcing and climatological density fields as well as both climatological meteorological forcing and actual six-hourly wind stress fields for 1994 and 1995. Transport from the main spawning areas to the west of the British Isles and north of Porcupine Bank was associated with currents along the shelf-edge and in the Rockall Trough. Tracers were either dispersed to the north and north-east along the shelf-edge, extending into the northern North Sea and Norwegian Sea, or were retained in the Rockall Gyre and over Porcupine Bank. A less intense southerly flow from Porcupine Bank was observed both under climatological conditions and in the 1995 simulation, when winds were more variable than in 1994. The results based on the 1995 meteorological conditions showed the most extreme retention of tracers in the Rockall Trough/shelf-edge area west of Scotland and a low penetration of tracers onto the shelf. These results are discussed in relation to the observed distribution of 0-group juveniles and to indices of year-class strength - in particular, in relation to the 1995 year class, which is the highest year-class estimate of blue whiting on record. [ABSTRACT FROM AUTHOR]

In order to determine excitation patterns to the lateral line system from a nearby 50 Hz oscillating sphere, dipole flow field equations were used to model the spatial distribution of pressures along a linear array of lateral line canal pores. Modeled predictions were then compared to pressure distributions measured for the same dipole source with a miniature hydrophone placed in a small test tank used for neurophysiological experiments. Finally, neural responses from posterior lateral line nerve fibers in the goldfish were measured in the test tank to demonstrate that modeled and measured pressure gradient patterns were encoded by the lateral line periphery. Response patterns to a 50 Hz dipole source that slowly changed location along the length of the fish included (1) peaks and valleys in spike-rate responses corresponding to changes in pressure gradient amplitudes, (2) 180° phase-shifts corresponding to reversals in the direction of the pressure gradient and (3) distance-dependent changes in the locations of peaks, valleys and 180° phase-shifts. Modeled pressure gradient patterns also predict that the number of neural amplitude peaks and phase transitions will vary as a function of neuromast orientation and axis of source oscillation. The faithful way in which the lateral line periphery encodes pressure gradient patterns has implications for how source location and distance might be encoded by excitation patterns in the CNS. Phase-shift information may be important for (1) inhibitory/excitatory sculpting of receptive fields and (2) unambiguously encoding source distance so that increases in source distance are not confused with decreases in source amplitude. [ABSTRACT FROM AUTHOR]

Examines the use of a electrophysiological recording technique to determine the moving speeds of prediators which was encoded by anterior lateral line nerve fibers. Properties of peripheral lateral line nerve fibers; Systems analysis of peripheral mechanisms; How the pressure gradient pattern produced by the moving sphere was characterised.

A correction to the article "Rheotaxis performance increases with group size in a coupled phase model with sensory noise" that was published in the December 2015 issue is presented.

Classical conditioning of respiration has been used to study many aspects of hearing in the goldfish, including absolute and masked thresholds, frequency, intensity, and time discrimination thresholds. A restrained fish is presented with a 7-s auditory signal that ends with a brief electric shock across the body. Shock causes an unconditioned suppression of respiration lasting several seconds. Several pairings of the auditory signal with the shock results in respiratory suppression during the signal. Initial conditioning is rapid (conditioned responses appear within the first 10 to 20 trials), several thresholds can be obtained in one day, and thresholds can be obtained for individual animals for several years. Critical factors for success with this method include the measurement of respiration (using a thermistor), method of animal restraint, levels of electric shock, intertrial intervals, false alarm estimation, overall respiratory rate, subject selection, and water conditioning. Details of the methods and procedures that have been found useful in conditioning and threshold definition will be given along with illustrative data on threshold values and stability in masking and intensity discrimination experiments. [ABSTRACT FROM AUTHOR]

Earlier studies on the ability of goldfish to detect amplitude-modulated (AM) noise signals [R. R. Fay, J. Neurophysiol. 44, 312-332 (1982)] suggested that goldfish were fundamentally different from other animals, including humans, in showing a flat modulation sensitivity function and no drop-off in sensitivity out to modulation rates of 400 Hz. To re-examine this anomaly, modulation sensitivity was measured in the goldfish at different sensation levels, using several experimental procedures and an improved technique for specifying the underwater acoustic stimulus at high modulation rates. Modulation sensitivity was found to be independent of sensation level at 10- and 100-Hz modulation. Sensitivity functions were relatively flat at modulation rates below 50-100 Hz with thresholds of AM detection occurring between 30% and 40% modulation. Greater than 60%-70% modulation was required for detection at 400 Hz. Randomly varying the overall intensity of unmodulated comparison noises and modulated noise signals produced little change in sensitivity or in the overall shape of the modulation function. These results show that the ability of goldfish to detect amplitude-modulated noise is not heavily dependent on intensity cues, nor fundamentally different from that of other species. [ABSTRACT FROM AUTHOR]

An in-depth analysis of hearing sensitivity for the jewel cichlid, Hemichromis bimaculatus was made using neurophysiological techniques to measure sensitivity at various levels of the auditory system and psychophysical techniques to measure whole-system sensitivity. For physiological studies, fish were stimulated by sinusoids generated by a loudspeaker or by direct vibration of the fish's head. Microphonic potentials were recorded from the sacculus of the inner ear and evoked potentials were recorded at several depths from the forebrain, midbrain, cerebellum, and medulla. For psychophysical studies, shock avoidance techniques were used in training fish to respond to tones generated by a loudspeaker. While audiograms based on the various neurophysiological and behavioral measures differed in detail, they showed in general that the auditory system of the jewel cichlid responds to sounds between 70 and 600 Hz, with best sensitivity in the region of 100 to 300 Hz. Evidence exists that within the frequency region of best sensitivity, the auditory system responds to both sound pressure and particle motion. The methodological difficulties in obtaining independent measures of sensitivity to pressure and particle motion will be discussed. [Supported by grants from NSF and NIH to R.F. and A.P.] [ABSTRACT FROM AUTHOR]

Behavorial audiograms have been obtained from two different species of squirrelfishes (Family: Holocentridae). Lowest thresholds measured for Myripristis kuntee were -50 dB re dyn/cm2 for frequencies extending from 300 to 2000 Hz, whereas best sensitivity measured for Adioryx xantherythrus was -28 dB at 500 Hz. While the low frequency end of the auditory range was at least 100 Hz for both species, the high end extended up to 800 Hz for A. xantherythrus and to 3000 Hz for M. kuntee. The two species tested can be taxonomically distinguished by anatomical differences in their peripheral auditory system. The genus Myripristis is characterized by anterior projections of the swimbladder which abut against the inner ear cavity, whereas in the genus Adioryx, the swimbladder lacks projections and is situated some distance away from the inner ear cavity [E. M. Nelson, Fieldiana: Zool. 37, 121-130 (1955)]. It is hypothesized that these anatomical variations affect the way sound reaches the inner ear, resulting in the reported differences in thresholds and frequency range of hearing. [Supported by NIH grant NS-15090.] [ABSTRACT FROM AUTHOR]

Old World monkeys were exposed to octave-band or wide-band noise at 117-120 dB SPL, 8 hours daily, five days per week for four weeks. The octave bands were centered at 500, 2000, 4000, or 8000 Hz. Thresholds for frequencies 63-40 000 Hz were measured daily before, during, and for one month after exposure, by the staircase method, using operant conditioning procedures with positive reinforcement. After the final threshold measurements the temporal bones were fixed and the inner ears examined by microdissection and phase-contrast microscopy. Maximum TTS, usually attained on the first day of exposure, ranged from 60 to 100 dB; PTS, from 40 to 60 dB. Both temporary and permanent loss involved at least two or three octaves and for the most part were greatest at, or within the octave above, the center of the exposure band. Hair cell counts showed reasonable correspondence between the location, severity, and extent (5-12 mm) of outer hair cell loss and the degree of PTS, in accordance with the place principle. In addition, most animals showed complete loss of outer and inner hair cells at the extreme basal end, usually correlated with a hearing loss for the highest frequencies. [Research supported by grants from NIH.] [ABSTRACT FROM AUTHOR]