2,157 research outputs found
Global atmospheric sampling program
Automated instruments were installed on a commercial B-747 aircraft, during the program, to obtain baseline data and to monitor key atmospheric constituents associated with emissions of aircraft engines in order to determine if aircraft are contributing to pollution of the upper atmosphere. Data thus acquired on a global basis over the commercial air routes for 5 to 10 years will be analyzed. Ozone measurements in the 29,000 to 45,000 foot altitude were expanded over what has been available from ozonesondes. Limited aerosol composition measurements from filter samples show low levels of sulfates and nitrates in the upper troposphere. Recently installed instruments for measurement of carbon monoxide and condensation nuclei are beginning to return data
Quantum dots in photonic crystal cavities
During the past two decades, the development of micro- and nano-fabrication technologies
has positively impacted multiple areas of science and engineering. In the photonics community,
these technologies had numerous early adopters, which led to photonic devices that
exhibit features at the nano-scale and operate at the most fundamental level of light–matter
interaction [28, 39, 18, 29]. One of the leading platforms for these types of devices is
based on gallium arsenide (GaAs) planar photonic crystals (PC) with embedded indium
arsenide (InAs) quantum dots (QDs). The PC architecture is advantageous because it
enables monolithic fabrication of photonic networks for efficient routing of light signals
of the chip [26]. At the same time, PC devices have low loss and ultra-small optical
mode volumes, which enable strong light–matter interactions. The InAs quantum dots
are well suited for quantum photonic applications because they have excellent quantum
efficiencies, large dipole moments, and a variety of quantum states that can be optically
controlled [24, 3]
Theory of Pump Depletion and Spike Formation in Stimulated Raman Scattering
By using the inverse spectral transform, the SRS equations are solved and the
explicit output data is given for arbitrary laser pump and Stokes seed profiles
injected on a vacuum of optical phonons. For long duration laser pulses, this
solution is modified such as to take into account the damping rate of the
optical phonon wave. This model is used to interprete the experiments of Druhl,
Wenzel and Carlsten (Phys. Rev. Lett., (1983) vol. 51, p. 1171), in particular
the creation of a spike of (anomalous) pump radiation. The related nonlinear
Fourier spectrum does not contain discrete eigenvalue, hence this Raman spike
is not a soliton.Comment: LaTex file, includes two figures in LaTex format, 9 page
A bright nanowire single photon source based on SiV centers in diamond
The practical implementation of many quantum technologies relies on the
development of robust and bright single photon sources that operate at room
temperature. The negatively charged silicon-vacancy (SiV-) color center in
diamond is a possible candidate for such a single photon source. However, due
to the high refraction index mismatch to air, color centers in diamond
typically exhibit low photon out-coupling. An additional shortcoming is due to
the random localization of native defects in the diamond sample. Here we
demonstrate deterministic implantation of Si ions with high conversion
efficiency to single SiV- centers, targeted to fabricated nanowires. The
co-localization of single SiV- centers with the nanostructures yields a ten
times higher light coupling efficiency than for single SiV- centers in bulk
diamond. This enhanced photon out-coupling, together with the intrinsic
scalability of the SiV- creation method, enables a new class of devices for
integrated photonics and quantum science.Comment: 15 pages, 5 figure
Rate of comorbidities in giant cell arteritis : A population-based study
Objective. To compare the rate of occurrence of comorbidities, including severe infections, in a population-based cohort of patients with biopsy-proven giant cell arteritis (GCA) with a reference population in Southern Sweden. Methods. The study included a population-based cohort of biopsy-proven GCA cases diagnosed between 1998 and 2010 from the Skane region in Southern Sweden (population: 1.2 million). For each patient, 4 reference subjects were identified from the general population and matched for age, sex, area of residence, and date of diagnosis of GCA. Using the Skane Healthcare Register, comorbidities and severe infections (requiring hospitalization) diagnosed after GCA onset were identified. The rate of the first occurrence of each comorbidity was the result of dividing the number of subjects with a given comorbidity by the person-years of followup. The rate ratio (RR; GCA:reference population) was also calculated. Results. There were 768 patients (571 women) with GCA and 3066 reference persons included in the study. The RR were significantly elevated for osteoporosis (2.81, 95% CI 2.33-3.37), followed by venous thromboembolic diseases (2.36, 95% CI 1.61-3.40), severe infections (1.85, 95% CI 1.57-2.18), thyroid diseases (1.55, 95% CI 1.25-1.91), cerebrovascular accidents (1.40, 95% CI 1.12-1.74), and diabetes mellitus (1.29, 95% CI 1.05-1.56). The RR for ischemic heart disease was elevated, but did not reach statistical significance (1.20, 95% CI 1.00-1.44). Conclusion. Patients with GCA have higher rates of selected comorbidities, including severe infections, compared with a reference population. Several of these comorbidities may be related to treatment with glucocorticosteroids, emphasizing the unmet need to find alternative treatments for GCA
Myonuclear Domain Flexibility Challenges Rigid Assumptions on Satellite Cell Contribution to Skeletal Muscle Fiber Hypertrophy
Satellite cell-mediated myonuclear accretion is thought to be required for skeletal muscle fiber hypertrophy, and even drive hypertrophy by preceding growth. Recent studies in humans and rodents provide evidence that challenge this axiom. Specifically, Type 2 muscle fibers reliably demonstrate a substantial capacity to hypertrophy in the absence of myonuclear accretion, challenging the notion of a tightly regulated myonuclear domain (i.e., area that each myonucleus transcriptionally governs). In fact, a “myonuclear domain ceiling”, or upper limit of transcriptional output per nucleus to support hypertrophy, has yet to be identified. Satellite cells respond to muscle damage, and also play an important role in extracellular matrix remodeling during loading-induced hypertrophy. We postulate that robust satellite cell activation and proliferation in response to mechanical loading is largely for these purposes. Future work will aim to elucidate the mechanisms by which Type 2 fibers can hypertrophy without additional myonuclei, the extent to which Type 1 fibers can grow without myonuclear accretion, and whether a true myonuclear domain ceiling exists
Myonuclear Transcriptional Dynamics in Response to Exercise Following Satellite Cell Depletion
Skeletal muscle is composed of post-mitotic myofibers that form a syncytium containing hundreds of myonuclei. Using a progressive exercise training model in the mouse and single nucleus RNA-sequencing (snRNA-seq) for high-resolution characterization of myonuclear transcription, we show myonuclear functional specialization in muscle. After 4 weeks of exercise training, snRNA-seq reveals that resident muscle stem cells, or satellite cells, are activated with acute exercise but demonstrate limited lineage progression while contributing to muscle adaptation. In the absence of satellite cells, a portion of nuclei demonstrates divergent transcriptional dynamics associated with mixed-fate identities compared with satellite cell replete muscles. These data provide a compendium of information about how satellite cells influence myonuclear transcription in response to exercise
Microcavity controlled coupling of excitonic qubits
Controlled non-local energy and coherence transfer enables light harvesting
in photosynthesis and non-local logical operations in quantum computing. The
most relevant mechanism of coherent coupling of distant qubits is coupling via
the electromagnetic field. Here, we demonstrate the controlled coherent
coupling of spatially separated excitonic qubits via the photon mode of a solid
state microresonator. This is revealed by two-dimensional spectroscopy of the
sample's coherent response, a sensitive and selective probe of the coherent
coupling. The experimental results are quantitatively described by a rigorous
theory of the cavity mediated coupling within a cluster of quantum dots
excitons. Having demonstrated this mechanism, it can be used in extended
coupling channels - sculptured, for instance, in photonic crystal cavities - to
enable a long-range, non-local wiring up of individual emitters in solids
Nonlinear energy transmission in the gap
Numerical simulations of the scattering of a linear plane wave incoming onto
a nonlinear medium (sine-Gordon) reveals that: i) nonlinearity allows energy
transmission in the forbidden band, ii) this nonlinear transmission occurs
beyond an energy threshold of the incoming wave, iii) the process begins (at
the threshold) with large amplitude breathers, and then energy is generically
transmitted both by kink-antikink pairs and breathers.Comment: Latex file, 6 figures, 9 pages, to appear in Physics Letters
INVERSE SCATTERING TRANSFORM ANALYSIS OF STOKES-ANTI-STOKES STIMULATED RAMAN SCATTERING
Zakharov-Shabat--Ablowitz-Kaup-Newel-Segur representation for
Stokes-anti-Stokes stimulated Raman scattering is proposed. Periodical waves,
solitons and self-similarity solutions are derived. Transient and bright
threshold solitons are discussed.Comment: 16 pages, LaTeX, no figure
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