30,776 research outputs found
Aluminum foil interconnects for solar cell panels
Commercially available sonic welding system and a specially-designed tip bonds aluminum foil interconnects to titanium-silver solar cell contacts
Energy Gaps and Kohn Anomalies in Elemental Superconductors
The momentum and temperature dependence of the lifetimes of acoustic phonons
in the elemental superconductors Pb and Nb was determined by resonant spin-echo
spectroscopy with neutrons. In both elements, the superconducting energy gap
extracted from these measurements was found to converge with sharp anomalies
originating from Fermi-surface nesting (Kohn anomalies) at low temperatures.
The results indicate electron many-body correlations beyond the standard
theoretical framework for conventional superconductivity. A possible mechanism
is the interplay between superconductivity and spin- or charge-density-wave
fluctuations, which may induce dynamical nesting of the Fermi surface
Mechanisms of superconductivity investigated by nuclear radiation
Investigation focused on the behavior of superconducting magnet and its constituent materials during and after exposure to nuclear radiation. The results will indicate the feasibility of their use in diverse applications and various environments
Transmission electron microscopy of an interplanetary dust particle with links to CI chondrites
The majority of hydrated interplanetary dust particles (IDPs) have compositions that resemble CI and CM chondrites, however, their mineralogies are most similar to the fine grained material in certain altered type-3 carbonaceous and ordinary chondrites. During the transmission electron microscope studies of hydrated IDPs, a unique particle was discovered whose mineralogy is very similar to that reported from CI chondrites. W7013F5 is the first IDP whose mineralogy and chemistry approximates that of CI chondrites. The similarity in mineralogy and mineral chemistry suggests that W7013F5 was altered under conditions similar to those that existed on the CI parent bodies
Aging: a young mind in old bees
A new surprising study suggests that various cognitive abilities and motosensory functions remain perfectly intact as honeybee workers age. How do these findings fit in with a buzzing life
Queen control over reproductive decisions--no sexual deception in the ant Lasius niger
Queen-worker conflicts in social insect societies have received much attention in the past decade. In many species workers modify the colony sex ratio to their own advantage or produce their own male offspring. In some other species, however, queens seem to be able to prevent workers from making selfish reproductive decisions. So far, little effort has been made to find out how queens may keep control over sex ratio and male parentage. In this study we use a Lasius niger population under apparent queen control to show that sexual deception cannot explain queen dominance in this population. The sexual deception hypothesis postulates that queens should prevent workers from discriminating against males by disguising male brood as females. Contrary to the predictions of this hypothesis, we found that workers are able to distinguish male and female larvae early in their development: in early spring workers generally placed only either female or male larvae in the uppermost chambers of the nest, although both types of larvae must have been present. At this time males were only at 11% of their final dry weight, a developmental stage at which (according to two models) workers would still have benefited from replacing queen-produced males by females or worker-produced males. This study thus demonstrates that sexual deception cannot account for the apparent queen control over colony sex ratio and male parentage in L. niger
Social insects as a model to study the molecular basis of ageing
One major gap in the current knowledge of the molecular bases of ageing is that most of the work has been done using short-lived model organisms such as fruitflies, nematodes, yeast and mice. Here, we argue that ants and social bee species provide an excellent complementary system to study ageing, and this for two reasons: first, in contrast to model organisms, ant and bee queens are extraordinarily long-lived, and second, there is a tremendous variation in lifespan among the genetically identical queens, workers (non-reproductive females) and males, with queens living up to 500 times longer than males and 10 times longer than workers. We review recent experimental work aimed at testing the role of antioxidant genes within the conceptual framework of the free radical theory of ageing, as well as studies investigating the role of juvenile hormone, vitellogenin and telomeres as mediators of ageing in social insects
Inelastic resonant tunneling through single molecules and quantum dots: spectrum modification due to nonequilibrium effects
Resonant electron transport through a mesoscopic region (quantum dot or
single molecule) with electron-phonon interaction is considered at finite
voltage. In this case the standard Landauer-B\"uttiker approach cannot be
applied. Using the nonequilibrium Green function method we show that due to a
nonequilibrium distribution function of electrons in the mesoscopic region, the
inelastic scattering rate and spectral function of the dot become functions of
the voltage and have to be calculated self-consistently.Comment: 4 pages, 3 figure
Momentum-resolved electron-phonon interaction in lead determined by neutron resonance spin-echo spectroscopy
Neutron resonance spin-echo spectroscopy was used to monitor the temperature
evolution of the linewidths of transverse acoustic phonons in lead across the
superconducting transition temperature, , over an extended range of the
Brillouin zone. For phonons with energies below the superconducting energy gap,
a linewidth reduction of maximum amplitude eV was observed below
. The electron-phonon contribution to the phonon lifetime extracted from
these data is in satisfactory overall agreement with {\it ab-initio}
lattice-dynamical calculations, but significant deviations are found
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