1,800 research outputs found
Stretching Folding Instability and Nanoemulsions
Here we show a folding-stretching instability in a microfluidic flow focusing
device using silicon oil (100cSt) and water. The fluid dynamics video
demonstrates an oscillating thread of oil focused by two co-flowing streams of
water. We show several high-speed sequences of these oscillations with 30,000
frames/s. Once the thread is decelerated in a slower moving pool downstream an
instability sets in and water-in-oil droplets are formed. We reveal the details
of the pinch-off with 500,000 frames/s. The pinch-off is so repeatable that
complex droplet patterns emerge. Some of droplets are below the resolution
limit, thus smaller than 1 micrometer in diameter
Isotopic dependence of nuclear charge radii and pairing energies
With a residual interaction consisting of density-independent two- and three-body parts, we obtain within Hartee-Fock-Bogolyubov theory at the same time good results on the odd-even staggering of charge radii and on trends of the pairing energies. We present results for Sn and some isotopic chains in the Ba region
Are yellow dung flies domesticated cow dung specialists?
The theory of niche differentiation implies some extent of specialization of species with regard to key resources, notably food. Coprophagous (dung-eating) insect larvae play a critical role in the decomposition of livestock dung in modern and traditional agricultural grasslands. The yellow dung fly (Scathophaga stercoraria L.; Diptera: Scathophagidae) is one of the largest, most common and abundant dung decomposers on pastures in cold-temperate regions across the entire northern hemisphere. As this fly is often associated with domesticated cattle or dairy cows, which are commonly kept for human nutrition worldwide (beef, milk, cheese, etc.), it is sometimes suspected to be a cow dung specialist. However, yellow dung flies are regularly active on and around other dung types, and must have reproduced on dung of wild vertebrates before the domestication of cattle. We therefore experimentally studied the performance of yellow dung fly larvae on dung of various large domestic vs. wild mammals (cow, horse, wild boar, red deer) in the laboratory in Switzerland. Larval performance in terms of juvenile survival, egg-to-adult development time, growth rate, and final adult body size, the major life history indicators of individual reproductive success, did not vary greatly among the various dung types tested. Thus, yellow dung flies can successfully reproduce on multiple types of mammal (vertebrate) dung, wild and domestic, and are therefore dung generalists rather than specialists. We conclude that yellow dung flies are common in European low- and highlands because they could plastically shift to dung of common herbivorous livestock after their domestication without losing the ability to reproduce on dung of common wild mammals
Exact Insulating and Conducting Ground States of a Periodic Anderson Model in Three Dimensions
We present a class of exact ground states of a three-dimensional periodic
Anderson model at 3/4 filling. Hopping and hybridization of d and f electrons
extend over the unit cell of a general Bravais lattice. Employing novel
composite operators combined with 55 matching conditions the Hamiltonian is
cast into positive semidefinite form. A product wave function in position space
allows one to identify stability regions of an insulating and a conducting
ground state. The metallic phase is a non-Fermi liquid with one dispersing and
one flat band.Comment: 4 pages, 3 figure
Hydrothermal activity and magma genesis along a propagating back-arc basin: Valu Fa Ridge (southern Lau Basin)
Valu Fa Ridge is an intraoceanic back-arc spreading center located at the southern prolongation of the Lau basin. Bathymetric observations as well as detailed sampling have been carried out along the spreading axis in order to trace hydrothermal and volcanic activity and to study magma generation processes. The survey shows that widespread lava flows from recent volcanic eruptions covered most of the Vai Lili hydrothermal vent field; only diffuse low-temperature discharge and the formation of thin layers of siliceous precipitates have been observed. Evidence of present-day hydrothermal activity at the Hine Hina site is indicated by a thermal anomaly in the overlying water column. Our studies did not reveal any signs of hydrothermal activity either above the seismically imaged magma chamber at 22°25′S or across the southern rift fault zone (22°51′S). Lavas recovered along the Valu Fa Ridge range from basaltic andesites to rhyolites with SiO2 contents higher than reported from any other intraoceanic back-arc basin. On the basis of the highly variable degrees of crystal fractionation along axis, the development of small disconnected magma bodies is suggested. In addition, the geochemical character of the volcanic rocks shows that the transition zone from oceanic spreading to propagating rifting is located south of the Hine Hina vent field in the vicinity of 22°35′S
Hexagonal microlasers based on organic dyes in nanoporous crystals
Molecular sieves, such as nanoporous AlPO_4-5, can host a wide variety of
laser active dyes. We embedded pyridine 2 molecules as a representative of a
commercially available dye which fits into the channel pores of the host
matrix. Many efficient dye molecules, such as rhodamines, do not fit into the
pores. But the amount of encapsulated dyes can be increased by modifying the
structure of the dyes such that they match the host templates. The resulting
microlasers have properties that depend on size and shape of the
microresonators, and we discuss a model for microscopic hexagonal ring
resonators. In terms of pump needed to reach lasing threshold molecular sieve
microlasers are comparable to VCSELs. For dyes which fit into the pores we
observed a partial regeneration of photo-induced damage.Comment: 10 pages, 16 figure
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