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We calculate the hydrodynamic force on a small spherical, unsteady squirmer moving with a time-dependent velocity in a fluid at rest, taking into account convective and unsteady fluid inertia effects in perturbation theory. Our results generalise those of Lovalenti & Brady (J. Fluid Mech., vol. 256, 1993, pp. 561–605) from passive to active spherical particles. We find that convective inertia changes the history contribution to the hydrodynamic force, as it does for passive particles. We determine how the hydrodynamic force depends on the swimming gait of the unsteady squirmer. Since swimming breaks the spherical symmetry of the problem, the force is not determined completely by the outer solution of the asymptotic matching problem, as it is for passive spheres. There are additional contributions due to the inhomogeneous solution of the inner problem. We also compute the disturbance flow, illustrating convective and unsteady effects when the particle experiences a sudden start followed by a sudden stop.
Telenomus podisi Ashmead (Hymenoptera: Scelionidae) is the most important egg parasitoid of Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), and its successful parasitism is related to their searching ability to find suitable hosts under a complex chemical environment using host-reliable cues. Thus, the objective of this study was to elucidate chemical substances on the external layer of E. heros eggs and report its potential kairomonal activity on T. podisi. We tested female wasps in olfactometer system to synthetic compounds obtained from a chemical identification of E. heros egg masses. The synthetic blend was also evaluated in parasitism tests under laboratory and semi-field conditions. We identified 31 substances from egg surface extracts, including monoterpenes, aldehydes and alkanes. Among those compounds, a synthetic solution including camphene, β-pinene, limonene and benzaldehyde-induced chemotaxic behaviour on the wasps and increased the parasitism on E. heros eggs, either in laboratory or semi-field test, suggesting its potential use to T. podisi manipulation and parasitism improvement.
The response of titanium surface irradiated with high intensity (1013 – 1015 W/cm2) Ti:sapphire laser was studied in vacuum. Most of the reported investigations were conducted with nano- to femtosecond lasers in gas atmospheres while the studies of titanium surface interacting with femtosecond laser in vacuum are scarce. The laser employed in our experiment was operating at 800 nm wavelength and pulse duration of 60 fs in single pulse regime. The observed surface changes and phenomena are (1) creation of craters, (2) formation of periodic surface structures at the reduced intensity, and (3) occurrence of plasma in front the target. Since microstructuring of titanium is very interesting in many areas (industry, medicine), it can be concluded from this study that the reported laser intensities can effectively be applied for micromachining of the titanium surface (increasing the roughness, formation of parallel periodic surface structures etc.).
Fifty-six accessions of Triticum monococcum and one accession each of T. beoticum and T. sinskajae were analysed for their storage protein compositions and breadmaking quality as determined by the SDS-sedimentation test. In total 30 different alleles at the Glu-A1m locus coding for high-molecular-weight glutenin subunits (HMW-GS), 25 alleles at the Gli-A1m locus coding for ω- and γ-gliadins and 45 alleles at the Gli-A2m locus controlling the synthesis of α/β-gliadins were detected. Most accessions contained one x-type and one y-type HMW-GS and two genotypes were null for both types of subunits. Two polypeptides within the mobility range of HMW-GS in SDS-PAGE were shown to be ω-type gliadins encoded by genes on the short arm of chromosome 1 A. T. sinskajae and several ‘monococcum’ accessions were shown to share the same alleles at Gli-A1m, Gli-A2m and Glu-A1m, confirming sinskajae as a subspecies of T. monococcum. The SDS-sedimentation volumes of most accessions were very low (11–35 ml), a few accessions showing mean sedimentation volumes as high as 90–93 ml. Through the comparison between biotypes occurring in some accessions of ‘monococcum’, good bread-making quality was found to be associated with the presence of alleles y, c and i at the Gli-A1m locus. All accessions were resistant to leaf rust and rich in protein (≥ 16·5%), and most of them showed resistance to powdery mildew.
The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients, due to self-focusing of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.
We present a series of experimental results, and their interpretation,
connected to various aspects of the hydrodynamics of laser produced
plasmas. Experiments were performed using the Prague PALS iodine laser
working at 0.44 μm wavelength and irradiances up to a few
1014 W/cm2. By adopting large focal spots and
smoothed laser beams, the lateral energy transport and lateral expansion
have been avoided. Therefore we could reach a quasi one-dimensional regime
for which experimental results can be more easily and properly compared to
available analytical models.
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