13,659 research outputs found
Carnivory in Adult Female Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae) and Its Effect on Egg Production
Seventy captive adult female wasps of the eumenid genera Ancistrocerus and Euodynerus were observed to feed on multiple prey items. It was shown experimentally that E. foraminatus females that fed on prey had significantly larger egg volumes than adult wasps deprived of prey
Methods for Artificial Rearing of Solitary Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae)
Solitary eumenid wasps of the genera Ancistrocerus and Euodynerus can be reared in small cages. Laboratory-reared larvae of the spruce budworm caterpillars, Choristoneura fumiferana (Lepidoptera: Torlricidae) are suitable prey
Spin-Echo Measurements for an Anomalous Quantum Phase of 2D Helium-3
Previous heat-capacity measurements of our group had shown the possible
existence of an anomalous quantum phase containing the zero-point vacancies
(ZPVs) in 2D He. The system is monolayer He adsorbed on graphite
preplated with monolayer He at densities () just below the 4/7
commensurate phase (). We carried out
pulsed-NMR measurements in order to examine the microscopic and dynamical
nature of this phase. The measured decay of spin echo signals shows the
non-exponential behaviour. The decay curve can be fitted with the double
exponential function, but the relative intensity of the component with a longer
time constant is small (5%) and does not depend on density and temperature,
which contradicts the macroscopic fluid and 4/7 phase coexistence model. This
slowdown is likely due to the mosaic angle spread of Grafoil substrate and the
anisotropic spin-spin relaxation time in 2D systems with respect to the
magnetic field direction. The inverse value deduced from the major echo
signal with a shorter time constant, which obeys the single exponential
function, decreases linearly with decreasing density from , supporting the
ZPV model.Comment: 4 pages, 6 figure
Analytical evaluation of atomic form factors: application to Rayleigh scattering
Atomic form factors are widely used for the characterization of targets and
specimens, from crystallography to biology. By using recent mathematical
results, here we derive an analytical expression for the atomic form factor
within the independent particle model constructed from nonrelativistic screened
hydrogenic wavefunctions. The range of validity of this analytical expression
is checked by comparing the analytically obtained form factors with the ones
obtained within the Hartee-Fock method. As an example, we apply our analytical
expression for the atomic form factor to evaluate the differential cross
section for Rayleigh scattering off neutral atoms.Comment: 7 pages, 1 figur
Shaping the formation of university-industry research collaborations: what type of proximity does really matter?
Research collaborations between universities and industry (U-I) are considered to be one important channel of potential localized knowledge spillovers (LKS). These collaborations favour both intended and unintended flows of knowledge and facilitate learning processes between partners from different organizations. Despite the copious literature on LKS, still little is known about the factors driving the formation of U-I research collaborations and, in particular, about the role that geographical proximity plays in the establishment of such relationships. Using collaborative research grants between universities and business firms awarded by the UK Engineering and Physical Sciences Research Council (EPSRC), in this article we disentangle some of the conditions under which different kinds of proximity contribute to the formation of U-I research collaborations, focusing in particular on clustering and technological complementarity among the firms participating in such partnerships
Temperature and pressure-induced spin-state transitions in LaCoO3
We report the continuous variation of the spin moment of cobalt in LaCoO3
across its temperature and pressure-induced spin transitions evidenced with
K\beta emission spectra. The first thermal transition is best described by a
transition to an orbitally nondegenerate intermediate spin (S=1) state. In
parallel, continuous redistribution of the 3d electrons is also indicated by
partial fluorescence yield X-ray absorption spectra. At high pressure, our
study confirms that the material becomes low spin between 40 and 70 kbar at
room temperature
Correlation in the transition metal based Heusler compounds CoMnSi and CoFeSi
Half-metallic ferromagnets like the full Heusler compounds with formula
XYZ are supposed to show an integer value of the spin magnetic moment.
Calculations reveal in certain cases of X = Co based compounds non-integer
values, in contrast to experiments. In order to explain deviations of the
magnetic moment calculated for such compounds, the dependency of the electronic
structure on the lattice parameter was studied theoretically. In local density
approximation (LDA), the minimum total energy of CoFeSi is found for the
experimental lattice parameter, but the calculated magnetic moment is about 12%
too low. Half-metallic ferromagnetism and a magnetic moment equal to the
experimental value of are found, however, only after increasing the
lattice parameter by more than 6%.
To overcome this discrepancy, the LDA scheme was used to respect on-site
electron correlation in the calculations. Those calculations revealed for
CoFeSi that an effective Coulomb-exchange interaction in the
range of about 2eV to 5eV leads to half-metallic ferromagnetism and the
measured, integer magnetic moment at the measured lattice parameter. Finally,
it is shown in the case of CoMnSi that correlation may also serve to
destroy the half-metallic behavior if it becomes too strong (for CoMnSi
above 2eV and for CoFeSi above 5eV). These findings indicate that on-site
correlation may play an important role in the description of Heusler compounds
with localized moments.Comment: submitted to Phys. Rev.
New Results on e+e- Line Emission in U+Ta Collisions
We present new results obtained from a series of follow-up e+e- coincidence
measurements in heavy-ion collisions, utilizing an improved experimental set-up
at the double-Orange beta-spectrometer of GSI. The collision system U+Ta was
reinvestigated in three independent runs at beam energies in the range
(6.0-6.4)xA MeV and different target thicknesses, with the objective to
reproduce a narrow sum-energy e+e- line at ~635 keV observed previously in this
collision system. At improved statistical accuracy, the line could not be found
in these new data. For the ''fission'' scenario, an upper limit (1 sigma) on
its production probability per collision of 1.3x10^{-8} can be set which has to
be compared to the previously reported value of [4.9 +- 0.8 (stat.) +- 1.0
(syst)]x10^{-7}. In the light of the new results, a reanalysis of the old data
shows that the continuous part of the spectrum at the line position is
significantly higher than previously assumed, thus reducing the production
probability of the line by a factor of two and its statistical significance to
< 3.4sigma.Comment: 15 pages, standard LaTeX with 3 included PS figures; Submitted to
Physics Letters
Current Account and External Financing
This article summarizes the most salient aspects of papers presented at the Central Bank of Chile’s Tenth Annual Conference “Current Account and External Financing” held in November 2006 and soon to be edited into an upcoming book. Many works were included oriented to improve understanding of recent trends and behavior of international financial markets and emerging economies participating in said markets. The papers, that cover both theoretical and empirical aspects, contribute elements to the comprehension of macroeconomic management in a small open economy, taking into account the main changes observed in recent years in matters relating with financial integration.
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