675 research outputs found
Magnetic field imaging with atomic Rb vapor
We demonstrate the possibility of dynamic imaging of magnetic fields using
electromagnetically induced transparency in an atomic gas. As an experimental
demonstration we employ an atomic Rb gas confined in a glass cell to image the
transverse magnetic field created by a long straight wire. In this arrangement,
which clearly reveals the essential effect, the field of view is about 2 x 2
mm^2 and the field detection uncertainty is 0.14 mG per 10 um x 10 um image
pixel.Comment: 4 pages, 3 figure
Topoisomer Differentiation of Molecular Knots by FTICR MS: Lessons from Class II Lasso Peptides
Lasso peptides constitute a class of bioactive peptides sharing a knotted
structure where the C-terminal tail of the peptide is threaded through and
trapped within an N-terminalmacrolactamring. The structural characterization of
lasso structures and differentiation from their unthreaded topoisomers is not
trivial and generally requires the use of complementary biochemical and
spectroscopic methods. Here we investigated two antimicrobial peptides
belonging to the class II lasso peptide family and their corresponding
unthreaded topoisomers: microcin J25 (MccJ25), which is known to yield
two-peptide product ions specific of the lasso structure under collisioninduced
dissociation (CID), and capistruin, for which CID does not permit to
unambiguously assign the lasso structure. The two pairs of topoisomers were
analyzed by electrospray ionization Fourier transform ion cyclotron resonance
mass spectrometry (ESI-FTICR MS) upon CID, infrared multiple photon
dissociation (IRMPD), and electron capture dissociation (ECD). CID and
ECDspectra clearly permitted to differentiate MccJ25 from its non-lasso
topoisomer MccJ25-Icm, while for capistruin, only ECD was informative and
showed different extent of hydrogen migration (formation of c\bullet/z from
c/z\bullet) for the threaded and unthreaded topoisomers. The ECD spectra of the
triply-charged MccJ25 and MccJ25-lcm showed a series of radical b-type product
ions {\eth}b0In{\TH}. We proposed that these ions are specific of
cyclic-branched peptides and result from a dual c/z\bullet and y/b
dissociation, in the ring and in the tail, respectively. This work shows the
potentiality of ECD for structural characterization of peptide topoisomers, as
well as the effect of conformation on hydrogen migration subsequent to electron
capture
Bichromatic electromagnetically induced transparency in cold rubidium atoms
In a three-level atomic system coupled by two equal-amplitude laser fields
with a frequency separation 2, a weak probe field exhibits a
multiple-peaked absorption spectrum with a constant peak separation .
The corresponding probe dispersion exhibits steep normal dispersion near the
minimum absorption between the multiple absorption peaks, which leads to
simultaneous slow group velocities for probe photons at multiple frequencies
separated by . We report an experimental study in such a
bichromatically coupled three-level system in cold Rb atoms.
The multiple-peaked probe absorption spectra under various experimental
conditions have been observed and compared with the theoretical calculations.Comment: RevTex, 4 pages, 6 figures, Email address: [email protected]
Taxonomic corpus-based concept summary generation for document annotation.
Semantic annotation is an enabling technology which links documents to concepts that unambiguously describe their content. Annotation improves access to document contents for both humans and software agents. However, the annotation process is a challenging task as annotators often have to select from thousands of potentially relevant concepts from controlled vocabularies. The best approaches to assist in this task rely on reusing the annotations of an annotated corpus. In the absence of a pre-annotated corpus, alternative approaches suffer due to insufficient descriptive texts for concepts in most vocabularies. In this paper, we propose an unsupervised method for recommending document annotations based on generating node descriptors from an external corpus. We exploit knowledge of the taxonomic structure of a thesaurus to ensure that effective descriptors (concept summaries) are generated for concepts. Our evaluation on recommending annotations show that the content that we generate effectively represents the concepts. Also, our approach outperforms those which rely on information from a thesaurus alone and is comparable with supervised approaches
Small-sized dichroic atomic vapor laser lock
Two, lightweight diode laser frequency stabilization systems designed for
experiments in the field are described. A significant reduction in size and
weight in both models supports the further miniaturization of measurement
devices in the field. Similar to a previous design, magnetic-field lines are
contained within a magnetic shield enclosing permanent magnets and a Rb cell,
so that these DAVLL systems may be used for magnetically sensitive instruments.
The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not
require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a
micro-fabricated cell (3 mm square), and requires heaters. These new systems
show no degradation in performance with regard to previous designs, while
considerably reducing dimensions.Comment: 13 pages, 11 figures, published versio
Optical detection of NMR J-spectra at zero magnetic field
Scalar couplings of the form J I_1 \cdot I_2 between nuclei impart valuable
information about molecular structure to nuclear magnetic-resonance spectra.
Here we demonstrate direct detection of J-spectra due to both heteronuclear and
homonuclear J-coupling in a zero-field environment where the Zeeman interaction
is completely absent. We show that characteristic functional groups exhibit
distinct spectra with straightforward interpretation for chemical
identification. Detection is performed with a microfabricated optical atomic
magnetometer, providing high sensitivity to samples of microliter volumes. We
obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz
statistical uncertainty. We anticipate that the technique described here will
provide a new modality for high-precision "J spectroscopy" using small samples
on microchip devices for multiplexed screening, assaying, and sample
identification in chemistry and biomedicine.Comment: 15 pages, 4 Figure
High contrast D line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Electromagnetically induced transparency (EIT) on atomic D line of
rubidium is studied using a nanometric-thin cell with atomic vapor column
length in the range of L= 400 - 800 nm. It is shown that the reduction of the
cell thickness by 4 orders as compared with an ordinary cm-size cell still
allows to form an EIT resonance for ( nm) with the
contrast of up to 40%. Remarkable distinctions of EIT formation in
nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect
of strong spectral narrowing and increase of the absorption for , EIT resonance is observed both in the absorption and the fluorescence
spectra for relatively low intensity of the coupling laser. Well resolved
splitting of the EIT resonance in moderate magnetic field for
can be used for magnetometry with nanometric spatial resolution. The presented
theoretical model well describes the observed results.Comment: Submitted to Applied Physics B: Lasers and Optics, 9 pages, 10
figure
An integrated atom-photon junction
Photonic chips that integrate guides, switches, gratings and other
components, process vast amounts of information rapidly on a single device. A
new branch of this technology becomes possible if the light is coupled to cold
atoms in a junction of small enough cross section, so that small numbers of
photons interact appreciably with the atoms. Cold atoms are among the most
sensitive of metrological tools and their quantum nature also provides a basis
for new information processing methods. Here we demonstrate a photonic chip
which provides multiple microscopic junctions between atoms and photons. We use
the absorption of light at a junction to reveal the presence of one atom on
average. Conversely, we use the atoms to probe the intensity and polarisation
of the light. Our device paves the way for a new type of chip with
interconnected circuits of atoms and photons.Comment: 5 pages, 4 figure. Submitted to Nature Photonic
Associations between grip strength, cardiorespiratory fitness, cardiovascular risk and mental health in forcibly displaced people from a Greek refugee camp
Muscular strength represents a specific component of health-related fitness. Hand grip strength is used as a simple and dynamic marker of maximum voluntary force of the hand and to estimate overall strength. Today, little is known about the relationship between grip strength and health in forcibly displaced populations. In the present study, we examined whether grip strength is associated with various health outcomes in a sample of forcibly displaced people living in a Greek refugee camp. The present analyses are part of a larger pragmatic randomized controlled trial. In this paper, cross-sectional baseline data of 143 participants (71 men, 72 women) will be presented. In addition to grip strength, the following physical and mental health outcomes were assessed: body weight and body composition, blood pressure, total cholesterol, low- and high-density lipoprotein cholesterol, triglycerides, blood glucose levels (HbA1c), post-traumatic stress disorder (PTSD) symptoms, depressive and anxiety symptoms, pain, and quality of life. Linear regression analyses were carried out to examine how grip strength is associated with the health outcomes, separately for absolute and normalized grip strength scores. Grip strength was positively and strongly associated with percentage muscle mass (normalized grip strength: Stand. B = 0.58, p < .001), whereas a negative association existed for percentage body fat (normalized grip strength: Stand. B = − 0.58, p < .001). No statistically significant associations occurred between grip strength and the other cardiovascular risk markers. In contrast, we found that participants with higher normalized grip strength reported higher levels of PTSD (normalized grip strength: Stand. B = 0.36, p < .05) and depressive symptoms (normalized grip strength: Stand. B = 0.29, p < .05). No significant association occurred between grip strength, anxiety, pain and quality of life. Measuring grip strength in forcibly displaced people can be a useful way to assess their overall muscle strength. Grip strength tests are easy to implement, and results can be used to assess the effects of specific intervention measures. Nevertheless, our results question the usefulness of grip strength as a marker of cardiovascular health and mental wellbeing in a refugee camp setting
Effects of a co-designed exercise and sport intervention on cardiorespiratory fitness and metabolic syndrome components among individuals living in a refugee camp in Greece: A randomized controlled trial.
BACKGROUND
The metabolic syndrome epidemic, including in forcibly displaced individuals, requires cost-effective prevention and treatment strategies. Yet, the health needs of forcibly displaced individuals often remain underserved. Our study evaluated the effect of a co-designed exercise and sport intervention on cardiorespiratory fitness and metabolic syndrome components among individuals in a refugee camp in Greece and examined the indirect effect through cardiorespiratory fitness on metabolic syndrome components.
METHODS
We conducted a randomized controlled trial involving an intervention and a wait-list control group with n = 142 (52.8 % women) forcibly displaced Southwest Asians and Sub-Saharan Africans. The intervention group participated for 10 weeks in exercise and sport activities. Outcomes were cardiorespiratory fitness and single metabolic syndrome components. Effects were analyzed with structural equation modeling.
RESULTS
In total, 62.7 % of participants presented with low cardiorespiratory fitness levels (<40th percentile), and 24.6 % met the criteria for metabolic syndrome. In the intervention group, 73.5 % attended the exercise and sport sessions at least once a week. There was evidence for a direct intervention effect on cardiorespiratory fitness, ßdirect = 0.12, p = 0.022, but not for any of the metabolic syndrome components (p ≥ 0.192). Cardiorespiratory fitness significantly facilitated the intervention's indirect effect on abdominal obesity, ßindirect = -0.03, p = 0.012, high diastolic blood pressure, ßindirect = -0.04, p = 0.011, and elevated triglycerides, ßindirect = -0.03, p = 0.025.
CONCLUSION
Implementing exercise and sport activities in a refugee camp in Greece effectively reaches a wider target population and improves cardiorespiratory fitness among forcibly displaced individuals. The intervention contributes to a decrease in abdominal obesity, high diastolic blood pressure and elevated triglycerides indirectly via improved cardiorespiratory fitness
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