919 research outputs found
Preparation and decay of a single quantum of vibration at ambient conditions
A single quantum of excitation of a mechanical oscillator is a textbook
example of the principles of quantum physics. Mechanical oscillators, despite
their pervasive presence in nature and modern technology, do not generically
exist in an excited Fock state. In the past few years, careful isolation of
GHz-frequency nano-scale oscillators has allowed experimenters to prepare such
states at milli-Kelvin temperatures. These developments illustrate the tension
between the basic predictions of quantum mechanics that should apply to all
mechanical oscillators existing even at ambient conditions, and the complex
experiments in extreme conditions required to observe those predictions. We
resolve the tension by creating a single Fock state of a vibration mode of a
crystal at room temperature using a technique that can be applied to any
Raman-active system. After exciting a bulk diamond with a femtosecond laser
pulse and detecting a Stokes-shifted photon, the 40~THz Raman-active internal
vibrational mode is prepared in the Fock state with probability.
The vibrational state is read out by a subsequent pulse, which when subjected
to a Hanbury-Brown-Twiss intensity correlation measurement reveals the
sub-Poisson number statistics of the vibrational mode. By controlling the delay
between the two pulses we are able to witness the decay of the vibrational Fock
state over its ps lifetime at room temperature. Our technique is agnostic
to specific selection rules, and should thus be applicable to any Raman-active
medium, opening a new generic approach to the experimental study of quantum
effects related to vibrational degrees of freedom in molecules and solid-state
systems
Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?
(abridged) In the frame of the search for extrasolar planets and brown dwarfs
around early-type main-sequence stars, we present the results obtained on the
early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the
spectra. Our dedicated radial-velocity measurement method was used to monitor
the star's radial velocities over five years. We also use complementary, high
angular resolution and high-contrast images taken with PUEO at CFHT. We show
that Theta Cygni radial velocities are quasi-periodically variable, with a
~150-day period. These variations are not due to the ~0.35-Msun stellar
companion that we detected in imaging at more than 46 AU from the star. The
absence of correlation between the bisector velocity span variations and the
radial velocity variations for this 7 km/s vsini star, as well as other
criteria indicate that the observed radial velocity variations are not due to
stellar spots. The observed amplitude of the bisector velocity span variations
also seems to rule out stellar pulsations. However, we observe a peak in the
bisector velocity span periodogram at the same period as the one found in the
radial velocity periodogram, which indicates a probable link between these
radial velocity variations and the low amplitude lineshape variations which are
of stellar origin. Long-period variations are not expected from this type of
star to our knowledge. If a stellar origin (hence of new type) was to be
confirmed for these long-period radial velocity variations, this would have
several consequences on the search for planets around main-sequence stars, both
in terms of observational strategy and data analysis. An alternative
explanation for these variable radial velocities is the presence of at least
one planet of a few Jupiter masses orbiting at less than 1 AU. (abridged)Comment: 9 pages, accepted in A
THE POWER OF STRUCTURED DESIGNS AND MIXED MODELS IN A REAL WORLD EXPERIMENT
Justifications usually given for adopting an automated system pertain to a reduction in labor and an improvement in quality control. A manufacturer of a prototype instrument that automated some of the steps for culturing bacteria wanted to compare the automated system to the manual system. The manufacturer wanted to compare the two systems in 1) Total time needed to isolate the target bacteria, 2) Ability to isolate the target bacteria, 3) Amount of interference from background (non-target) bacterial growth, and 1) Extent of cross (sample to sample) contamination.
This paper presents the experimental design used to make these comparisons and how the design helped discover some surprising results about laboratory quality control. The experiment presented illustrates the importance of a good experimental design, the power of current statistical tools, and that a thorough and appropriate analysis of a data set requires side-by-side good detective work by both statistician and client
Extrasolar planets and brown dwarfs around A--F type stars. VIII. A giant planet orbiting the young star HD113337
In the frame of the search for extrasolar planets and brown dwarfs around
early-type main-sequence stars, we present the detection of a giant planet
around the young F-type star HD113337. We estimated the age of the system to be
150 +100/-50 Myr. Interestingly, an IR excess attributed to a cold debris disk
was previously detected on this star. The SOPHIE spectrograph on the 1.93m
telescope at Observatoire de Haute-Provence was used to obtain ~300 spectra
over 6 years. We used our SAFIR tool, dedicated to the spectra analysis of A
and F stars, to derive the radial velocity variations. The data reveal a 324.0
+1.7/-3.3 days period that we attribute to a giant planet with a minimum mass
of 2.83 +- 0.24 Mjup in an eccentric orbit with e=0.46 +- 0.04. A long-term
quadratic drift, that we assign to be probably of stellar origin, is
superimposed to the Keplerian solution.Comment: 7 pages, 4 figure
Planets around stars in young nearby associations *** radial Velocity searches: a feasibility study, and first results
Stars in young nearby associations are the only targets allowing giant planet
searches at all separations in the near future, by coupling indirect techniques
such as radial velocity and deep imaging. These stars are first priorities
targets for the forthcoming planets imagers on 10-m class telescopes. Young
stars rotate more rapidly and are more active than their older counterparts.
Both effects can limit the capability to detect planets using RV. We wish to
explore the planet detection capabilities of a representative sample of stars
in close and young associations with radial velocity data and explore the
complementarity between this technique and direct imaging. We observed 26 such
targets with spectral types from A to K and ages fromComment: submitte
Prevalence of Escherichia coli O157:H7 in cow-calf herds in Kansas
Fecal samples from cows and calves and samples of water sources were collected monthly for 8 months from 10 Kansas cow-calf farms to determine the prevalence of E. coli O157:H7. The bacterium was found in 8% of fecal samples from cows that were within 24 hours of calving, 1.4% of fecal samples from cows which were not within 24 hours of calving, 1.4% of calf fecal samples, and 1.5% of water samples. E. coli O157:H7 was identified from at least one sample on all farms
Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties
Since 1999, we have been conducting a radial velocity survey of 179 K giants
using the CAT at UCO/Lick observatory. At present ~20-100 measurements have
been collected per star with a precision of 5 to 8 m/s. Of the stars monitored,
145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43
exhibit significant periodicities. Our aim is to investigate possible
mechanism(s) that cause these observed RV variations. We intend to test whether
these variations are intrinsic in nature, or possibly induced by companions, or
both. In addition, we aim to characterise the parameters of these companions. A
relation between log g and the amplitude of the RV variations is investigated
for all stars in the sample. Furthermore, the hypothesis that all periodic RV
variations are caused by companions is investigated by comparing their inferred
orbital statistics with the statistics of companions around main sequence
stars. A strong relation is found between the amplitude of the RV variations
and log g in K giant stars, as suggested earlier by Hatzes & Cochran (1998).
However, most of the stars exhibiting periodic variations are located above
this relation. These RV variations can be split in a periodic component which
is not correlated with log g and a random residual part which does correlate
with log g. Compared to main-sequence stars, K giants frequently exhibit
periodic RV variations. Interpreting these RV variations as being caused by
companions, the orbital param eters are different from the companions orbiting
dwarfs. Intrinsic mechanisms play an important role in producing RV variations
in K giants stars, as suggested by their dependence on log g. However, it
appears that periodic RV variations are additional to these intrinsic
variations, consistent with them being caused by companions.Comment: 10 pages, accepted by A&
Radial Velocities with CRIRES: Pushing precision down to 5-10 m/s
With the advent of high-resolution infrared spectrographs, Radial Velocity
(RV) searches enter into a new domain. As of today, the most important
technical question to address is which wavelength reference is the most
suitable for high-precision RV measurements.
In this work we explore the usage of atmospheric absorption features. We make
use of CRIRES data on two programs and three different targets. We re-analyze
the data of the TW Hya campaign, reaching a dispersion of about 6 m/s on the RV
standard in a time scale of roughly 1 week. We confirm the presence of a
low-amplitude RV signal on TW Hya itself, roughly 3 times smaller than the one
reported at visible wavelengths. We present RV measurements of Gl 86 as well,
showing that our approach is capable of detecting the signal induced by a
planet and correctly quantifying it.
Our data show that CRIRES is capable of reaching a RV precision of less than
10 m/s in a time-scale of one week. The limitations of this particular approach
are discussed, and the limiting factors on RV precision in the IR in a general
way. The implications of this work on the design of future dedicated IR
spectrographs are addressed as well.Comment: 9 pages, accepted for publication in A&
Neurocranial development of the coelacanth and the evolution of the sarcopterygian head
The neurocranium of sarcopterygian fishes was originally divided into an anterior (ethmosphenoid) and posterior (otoccipital) portion by an intracranial joint, and underwent major changes in its overall geometry before fusing into a single unit in lungfishes and early tetrapods. Although the pattern of these changes is well-documented, the developmental mechanisms that underpin variation in the form of the neurocranium and its associated soft tissues during the evolution of sarcopterygian fishes remain poorly understood. The coelacanth Latimeria is the only known living vertebrate that retains an intracranial joint. Despite its importance for understanding neurocranial evolution, the development of the neurocranium of this ovoviviparous fish remains unknown. Here we investigate the ontogeny of the neurocranium and brain in Latimeria chalumnae using conventional and synchrotron X-ray microcomputed tomography as well as magnetic resonance imaging, performed on an extensive growth series for this species. We describe the neurocranium at the earliest developmental stage known for Latimeria, as well as the major changes that the neurocranium undergoes during ontogeny. Changes in the neurocranium are associated with an extreme reduction in the relative size of the brain along with an enlargement of the notochord. The development of the notochord appears to have a major effect on the surrounding cranial components, and might underpin the formation of the intracranial joint. Our results shed light on the interplay between the neurocranium and its adjacent soft tissues during development in Latimeria, and provide insights into the developmental mechanisms that are likely to have underpinned the evolution of neurocranial diversity in sarcopterygian fishes
Elodie metallicity-biased search for transiting Hot Jupiters IV. Intermediate period planets orbiting the stars HD43691 and HD132406
We report here the discovery of two planet candidates as a result of our
planet-search programme biased in favour of high-metallicity stars, using the
ELODIE spectrograph at the Observatoire de Haute Provence. One of them has a
minimum mass m_2\sin{i} = 2.5 M_Jup and is orbiting the metal-rich star HD43691
with period P = 40 days and eccentricity e = 0.14. The other planet has a
minimum mass m_2\sin{i} = 5.6 M_Jup and orbits the slightly metal-rich star
HD132406 with period P = 974 days and eccentricity e = 0.34. Both stars were
followed up with additional observations using the new SOPHIE spectrograph that
replaces the ELODIE instrument, allowing an improved orbital solution for the
systems.Comment: 6 pages, 4 figures, to be published in A&
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