The antennal grooming behavior in Blartellrr germanica (L.), involves the coordinated use of the foreleg tibia and tarsus, and the mouthparts. The foreleg opposite the antenna is used to bend the flagellum to the mouthparts, after which it is pulled through the labium and maxillum by the resilience of the bend in the flagellum. Antennal grooming behavior is a sequence of five distinct events which define a grooming episode. Under normal conditions each antenna is groomed in 3-6 sec, and both antennae may or may not be groomed in successive episodes. When exposed to unfamiliar environments laboratory (VPI) and field (RHA) strain cockroaches display a distinct sequence of movement and antennal grooming rates (groomingslmin) during the initial 5 min. Antennal grooming in both strains increases from the resting rate (0.23 = VPl, 0.95 = RHA) to the investigative rate (1.10 and 1.80 grooming per min, respectively) after 3 min exposure, but shortly returns to the resting rate. Response to a chemical and nonchemical stimulus rapidly increases the antennal grooming from the resting rate to the irritation rate, at which time the antennae collapse to the substrate.

Amplitude-dependent internal friction of polycrystalline commercial lead has been studied in wide frequency and strain amplitude ranges. The strain amplitude dependence shows two stages characterized by different recovery times. These stages are attributed to different mechanisms: dislocation-point obstacle interaction at moderate amplitudes and interaction between dislocations along with their multiplication at the high ones. Pronounced and nonmonotonous dependence of the amplitude-dependent internal friction and elastic limit on prestrain is revealed. This peculiarity is attributed to transition from relatively homogeneous dislocation distribution to the inhomogeneous one due to formation of the cellular structure.

The response of a floating ice plate to a moving load is given in terms of a pair of Green's functions. General expressions for these Green's functions are derived for the case of an infinite isotropic plate of uniform thickness supported on a fluid base of uniform depth. The distributions of stress and strain in the vicinity of a concentrated load receive significant contributions from waves of length comparable with the plate thickness and their description necessitates an exact description of thickness effects. Circumstances in which the classical thin-plate theory can be recovered are discussed. The steady-state response to a uniformly moving load displays a so-called ‘critical’ behaviour for load velocities in the neighbourhood of a threshold value at which radiation commences. At the critical speed the amplitude is limited by dissipative forces in the ice plate. To describe this a simple viscoelastic term is included in our model. Calculations indicate that thin-plate theory is accurate to within 5% for distances greater than twenty times the ice thickness.

The Young’s modulus and internal friction of YBa2 Cu3 O7−δ were measured from 280 to 80 K at 40 kHz using an ultrasonic composite oscillator technique. Three internal friction peaks intrinsic to the polycrystalline material which were observed at 105, 125, and 225 K disappeared when the sample was deoxygenated. Other structure in the internal friction between 220 and 280 K is ascribed to water vapor. The 225 K peak is reversibly eliminated on exposure to moist air. This is suggestive of internal friction at crystal surfaces or grain boundaries.

The resistivity of first yea sea ice was measured in situ at two locations in McMurdo Sound, Antarctica using the Wenner array technique at audio frequencies. In addition, salinity and temperature profiles were measured. The results are adequately described by a three-layer model made up of a thin conducting surface layer, an insulating layer and finally sea water. The average resistivity of sea ice was found to lie in the range 50–200 Ω depending on salinity, structure and temperature. The resistivity and thicknesses of the surface layer could not be determined uniquely by the model but a maximum value for the resistivity as low as 4 Ω m was obtained. The resistivity of the surface layer was found to be influenced by the removal of the snow cover. The depth predicted by the Wenner sounding was found to be roughly 50% of the actual depth, a result that is consistent with a conductivity in the vertical direction and parallel to the brine channels of four times the conductivity in the horizontal direction within the bulk layer.

Using the ultrasonic composite oscillator technique at high strain amplitudes (8 × 10−6-2 × 10−4) we have measured the equilibrium dislocation charge in bent potassium chloride single crystals doped with Ca2+ (0·02–14 p.p.m.) over the temperature range 400–730°C. The large strain amplitude ensures that dislocation displacement exceeds the Debye-Hückel screening radius so that the resulting polarization is unscreened. In the amplitude-dependent region the isoelectric temperature at which the mean charge vanished was found to decrease slowly with strain amplitude. The temperature and impurity dependences of the charge are well characterized by a straightforward model of vacancy formation at core jogs.

Using the ultrasonic piezoelectric composite oscillator technique, the temperature dependence of dislocation charge in bent KCI single crystals has been measured as a function of Ca impurity concentration. In each case the charge changes sign at an extrinsic isoelectric temperature, T e. The shift in T e with impurity concentration allows the individual thermodynamic vacancy formation parameters, h +, S +, h − and S −, to be measured. Assuming the temperature-independent Schottky parameters of Chandra and Rolfe (1970), we obtain h + = 1·256±0·008eV, S +=453±0·10k, h − = 1·334∓0.008eV and S − = 5·08∓0·10k. The possible temperature dependence in these parameters is investigated.

By using the ultrasonic composite oscillator operating at 40 kHz and strain amplitudes of 10-lO to ~X I O -~, it is possible to determine the interna1 frictipn, the modulus defect and the direct and converse piezoelectric defect due to charged dislocations in bent alkali halide single crystals.A mode1 independent equation linking these terms enables the determination of the electrical charge on the dislocations together with the dislocation displacement.The temperature at which the mean dislocation charge vanishes is the isoelectric temperature, Te and from its temperature dependence the vacancy formation parameters have been calculated.We also find that Te is weakly dependent on the strain amplitude.

On peut utiliser la deformation cyclique plastique de l'acier et du plomb pour absorber l'energie du mouvement d'une structure de base isolee pendant un tremblement de terre

AbstractStrong suppression of molecular ions in positive secondary ion mass spectra (SIMS) is achieved by electric isolation of a specimen (SI) with an electrically charged aperture situated immediately above its surface. This technique is also useful for controlling the surface charging on an insulator. The origin of this phenomenon has been explored using metals and semiconductors as models. The strong molecular suppression effect is found to result from the very high ion kinetic energies (>400 eV) emerging from the surface under SI conditions. The charged aperture is believed to stabilize surface charging by confining it within a small region. SI methods for reducing molecular ions in silicon and mild steel specimens reduce major molecular fragments by 3–4 orders of magnitude.

In the amplitude independent region the dislocation damping is attributed to either phonon-drag (Granato-Lücke theory) or to the compensating charge-cloud surrounding electrically charged dislocations (Robinson-Birnbaum theory). The experimental results for the dependence of the damping on temperature, frequency and dislocation charge are compared with the two theories. Since it is found that in some cases it is necessary to include both forms of damping, a more complete theory is developed which includes both terms. In the amplitude dependent region the dislocation damping was thought to be due to the dislocations breaking away from pinning points or breaking through the compensating charge-cloud. Using the piezoelectric defect results for electrically charged dislocation in KCl the force-displacement hysteresis loop for the moving dislocations is determined together with the force-displacement curves for dislocations assuming phonon and charge-cloud damping. These results are found to be inconsistent with the “break away” models for amplitude dependence but instead to be consistent with the restoring force due to an elliptical compensation charge cloud, with a size proportional to the square root of the dislocation charge.

Using the ultrasonic piezoelectric composite oscillator technique we have measured the temperature dependence of dislocation charge in bent KCl single crystals as a function of Ca impurity concentration. In each case the charge changes sign at an extrinsic isoelectric temperature, Te , and the shift in Te with impurity concentration allows the calculation of the individual thermodynamic vacancy formation parameters. We obtain h+ = 1.244±0.014 eV, s+ = 4.50±0.19 k, h- = 1.346∓ 0.014 eV and s- = 5.11∓0.19K.

A simple third-order elasticity theory of melting, which avoids traditional restriction to crystalline defects, is presented. The melt is described by a set of local strains which vary randomly but which have well defined mean square values. The predicted interrelationships between melting parameters are satisfied for many materials.

Previously reported piezoelectric defect results for electrically charged dislocations in KCl are used to determine the force-displacement hysteresis loop for the moving dislocations together with the force-displacement curves for dislocations assuming phonon and charge-cloud damping. In the amplitude-dependent region, the results are found to be inconsistent with ‘breakaway’ models for amplitude dependence but instead to be consistent with the restoring force clue to an elliptical compensating chahrge cloud, with a size proportional to the square root of the dislocation displacement.

Journal Article Wood Consumption and Growth of Hylotrupes bajulus (L.) Larvae in Three Environments Get access Kevin F. Cannon, Kevin F. Cannon Department of Entomology, Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 Search for other works by this author on: Oxford Academic PubMed Google Scholar Wm. H. Robinson Wm. H. Robinson Department of Entomology, Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061 Search for other works by this author on: Oxford Academic PubMed Google Scholar Environmental Entomology, Volume 10, Issue 4, 1 August 1981, Pages 458–461, https://doi.org/10.1093/ee/10.4.458 Published: 01 August 1981 Article history Received: 20 May 1980 Published: 01 August 1981