10,868 research outputs found
Quantitative atomic spectroscopy for primary thermometry
Quantitative spectroscopy has been used to measure accurately the
Doppler-broadening of atomic transitions in Rb vapor. By using a
conventional platinum resistance thermometer and the Doppler thermometry
technique, we were able to determine with a relative uncertainty of
, and with a deviation of from the
expected value. Our experiment, using an effusive vapour, departs significantly
from other Doppler-broadened thermometry (DBT) techniques, which rely on weakly
absorbing molecules in a diffusive regime. In these circumstances, very
different systematic effects such as magnetic sensitivity and optical pumping
are dominant. Using the model developed recently by Stace and Luiten, we
estimate the perturbation due to optical pumping of the measured value
was less than . The effects of optical pumping on atomic and
molecular DBT experiments is mapped over a wide range of beam size and
saturation intensity, indicating possible avenues for improvement. We also
compare the line-broadening mechanisms, windows of operation and detection
limits of some recent DBT experiments
Twisted topological structures related to M-branes
Studying the M-branes leads us naturally to new structures that we call
Membrane-, Membrane^c-, String^K(Z,3)- and Fivebrane^K(Z,4)-structures, which
we show can also have twisted counterparts. We study some of their basic
properties, highlight analogies with structures associated with lower levels of
the Whitehead tower of the orthogonal group, and demonstrate the relations to
M-branes.Comment: 17 pages, title changed on referee's request, minor changes to
improve presentation, typos correcte
Abundances in Stars from the Red Giant Branch Tip to the Near Main Sequence in M71: II. Iron Abundance
We present [Ffe/H] abundance results that involve a sample of stars with a
wide range in luminosity from luminous giants to stars near the turnoff in a
globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more
luminous than the RHB, 3 horizontal branch stars, 9 giant stars less luminous
than the RHB, and 3 stars near the turnoff. We analyzed both Fe I and Fe II
lines in high dispersion spectra observed with HIRES at the W. M. Keck
Observatory. We find that the [Fe/H] abundances from both Fe I and Fe II lines
agree with each other and with earlier determinations. Also the [Fe/H] obtained
from Fe I and Fe II lines is constant within the rather small uncertainties for
this group of stars over the full range in Teff and luminosity, suggesting that
NLTE effects are negligible in our iron abundance determination. In this
globular cluster, there is no difference among the mean [Fe/H] of giant stars
located at or above the RHB, RHB stars, giant stars located below the RHB and
stars near the turnoff.Comment: Minor changes to conform to version accepted for publication, with
several new figures (Paper 2 of a pair
Desempenho agronĆ“mico de hĆbridos de sorgo biomassa.
O objetivo deste trabalho foi caracterizar o potencial agronĆ“mico de hĆbridos de sorgo biomassa visando a geraĆ§Ć£o de energia.bitstream/item/57175/1/bol-41.pd
RDF Querying
Reactive Web systems, Web services, and Web-based publish/
subscribe systems communicate events as XML messages, and in
many cases require composite event detection: it is not sufficient to react
to single event messages, but events have to be considered in relation to
other events that are received over time.
Emphasizing language design and formal semantics, we describe the
rule-based query language XChangeEQ for detecting composite events.
XChangeEQ is designed to completely cover and integrate the four complementary
querying dimensions: event data, event composition, temporal
relationships, and event accumulation. Semantics are provided as
model and fixpoint theories; while this is an established approach for rule
languages, it has not been applied for event queries before
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