623 research outputs found
Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel
We theoretically investigate the process of coupling cold atoms into the core
of a hollow-core photonic-crystal optical fiber using a blue-detuned
Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam
to couple the atoms, the blue-detuned hollow-beam can confine cold atoms to the
darkest regions of the beam thereby minimizing shifts in the internal states
and making the guide highly robust to heating effects. This single optical beam
is used as both a funnel and guide to maximize the number of atoms into the
fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical
trap (MOT) above a vertically-oriented optical fiber. We observe a
gravito-optical trapping effect for atoms with high orbital momentum around the
trap axis, which prevents atoms from coupling to the fiber: these atoms lack
the kinetic energy to escape the potential and are thus trapped in the laser
funnel indefinitely. We find that by reducing the dipolar force to the point at
which the trapping effect just vanishes, it is possible to optimize the
coupling of atoms into the fiber. Our simulations predict that by using a
low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a
20-{\mu}m radius core hollow-fiber it is possible to couple 11% of the atoms
from a MOT 9 mm away from the fiber. When MOT is positioned further away,
coupling efficiencies over 50% can be achieved with larger core fibers.Comment: 11 pages, 12 figures, 1 tabl
Molecular and isotopic investigations of pottery and “charred remains” from Sannai Maruyama and Sannai Maruyama No. 9, Aomori Prefecture.
This paper presents a preliminary study of the analysis of organic residues of Early and Middle Jomon pottery and ‘charred remains.’ Samples are taken from the Sannai Maruyama site and the Sannai Maruyama No. 9 site in Aomori City, Aomori Prefecture in northern Japan. The following questions are addressed in this study: (i) Do organic residues survive in association with pottery vessels and charred remains? (ii) Can the residues be identified based on molecular and isotopic criteria applied in other investigations? (iii) Are the residues associated with the charred remains common to the residues associated with the pottery vessels? (iv) How do these residues contribute to our understanding of food processing and consumption? Results of our analysis indicate that the lipid composition of the pottery extracts is remarkably similar although some of the sherds exhibited better preservation and a wider range of molecules were detected albeit in lower abundance. There is a marked contrast with the composition of the lipid extracts of the ‘charred remains.’ The lipid compositions of sample sets from Sannai Maruyama and Sannai Maruyama No. 9 suggest aquatic resources in the pottery but with a plant contribution. The ‘charred remains’ from Sannai Maruyama contain plant tissues most likely with a high starch composition such as nuts. Lipids were recovered from the majority of the samples
Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a global health problem, and current therapy for COPD is poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. Imbalance of oxidant/antioxidant balance caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g. NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervening COPD
Cancer-related ectopic expression of the bone-related transcription factor RUNX2 in non-osseous metastatic tumor cells is linked to cell proliferation and motility
10.1186/bcr2762Breast Cancer Research125-BCRR
Reversible gene knockdown in mice using a tight, inducible shRNA expression system
RNA interference through expression of short hairpin (sh)RNAs provides an efficient approach for gene function analysis in mouse genetics. Techniques allowing to control time and degree of gene silencing in vivo, however, are still lacking. Here we provide a generally applicable system for the temporal control of ubiquitous shRNA expression in mice. Depending on the dose of the inductor doxycycline, the knockdown efficiency reaches up to 90%. To demonstrate the feasibility of our tool, a mouse model of reversible insulin resistance was generated by expression of an insulin receptor (Insr)-specific shRNA. Upon induction, mice develop severe hyperglycemia within seven days. The onset and progression of the disease correlates with the concentration of doxycycline, and the phenotype returns to baseline shortly after withdrawal of the inductor. On a broad basis, this approach will enable new insights into gene function and molecular disease mechanisms
Multi-scale sequence correlations increase proteome structural disorder and promiscuity
Numerous experiments demonstrate a high level of promiscuity and structural
disorder in organismal proteomes. Here we ask the question what makes a protein
promiscuous, i.e., prone to non-specific interactions, and structurally
disordered. We predict that multi-scale correlations of amino acid positions
within protein sequences statistically enhance the propensity for promiscuous
intra- and inter-protein binding. We show that sequence correlations between
amino acids of the same type are statistically enhanced in structurally
disordered proteins and in hubs of organismal proteomes. We also show that
structurally disordered proteins possess a significantly higher degree of
sequence order than structurally ordered proteins. We develop an analytical
theory for this effect and predict the robustness of our conclusions with
respect to the amino acid composition and the form of the microscopic potential
between the interacting sequences. Our findings have implications for
understanding molecular mechanisms of protein aggregation diseases induced by
the extension of sequence repeats
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
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