129 research outputs found
Sub-kHz-level relative stabilization of an intracavity doubled continuous wave optical parametric oscillator using Pound-Drever-Hall scheme
We report the relative frequency stabilization of an intracavity frequency
doubled singly resonant optical parametric oscillator on a Fabry-Perot\'etalon.
The red/orange radiation produced by the frequency doubling of the intracavity
resonant idler is stabilized using the Pound-Drever-Hall locking technique. The
relative frequency noise of this orange light, when integrated from 1 Hz to 50
kHz, corresponds to a standard deviation of 700 Hz. The frequency noise of the
pump laser is shown experimentally to be transferred to the non resonant signal
beam
Laser cooling of trapped ytterbium ions with an ultraviolet diode laser
We demonstrate an ultraviolet diode laser system for cooling of trapped
ytterbium ions. The laser power and linewidth are comparable to previous
systems based on resonant frequency doubling, but the system is simpler, more
robust, and less expensive. We use the laser system to cool small numbers of
ytterbium ions confined in a linear Paul trap. From the observed spectra, we
deduce final temperatures < 270 mK.Comment: submitted to Opt. Let
Trapping of single atoms in cavity QED
By integrating the techniques of laser cooling and trapping with those of
cavity quantum electrodynamics (QED), single Cesium atoms have been trapped
within the mode of a small, high finesse optical cavity in a regime of strong
coupling. The observed lifetime for individual atoms trapped within the cavity
mode is ms, and is limited by fluctuations of light forces
arising from the far-detuned intracavity field. This initial realization of
trapped atoms in cavity QED should enable diverse protocols in quantum
information science.Comment: 4 pages, 4 figure
Doppler cooling and trapping on forbidden transitions
Ultracold atoms at temperatures close to the recoil limit have been achieved
by extending Doppler cooling to forbidden transitions. A cloud of ^40Ca atoms
has been cooled and trapped to a temperature as low as 6 \mu K by operating a
magneto-optical trap on the spin-forbidden intercombination transition.
Quenching the long-lived excited state with an additional laser enhanced the
scattering rate by a factor of 15, while a high selectivity in velocity was
preserved. With this method more than 10% of pre-cooled atoms from a standard
magneto-optical trap have been transferred to the ultracold trap. Monte-Carlo
simulations of the cooling process are in good agreement with the experiments
Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure
The combination of ultra-cold atomic clouds with the light fields of optical
cavities provides a powerful model system for the development of new types of
laser cooling and for studying cooperative phenomena. These experiments
critically depend on the precise tuning of an incident pump laser with respect
to a cavity resonance. Here, we present a simple and reliable experimental
tuning scheme based on a two-mode laser spectrometer. The scheme uses a first
laser for probing higher-order transversal modes of the cavity having an
intensity minimum near the cavity's optical axis, where the atoms are confined
by a magnetic trap. In this way the cavity resonance is observed without
exposing the atoms to unwanted radiation pressure. A second laser, which is
phase-locked to the first one and tuned close to a fundamental cavity mode
drives the coherent atom-field dynamics.Comment: 7 pages, 7 figure
Can Echocardiographic Findings Predict Falls in Older Persons?
Background. The European and American guidelines state the need for echocardiography in patients with syncope. 50% of older adults with syncope present with a fall. Nonetheless, up to now no data have been published addressing echocardiographic abnormalities in older fallers. Method and Findings. In order to determine the association between echocardiographic abnormalities and falls in older adults, we performed a prospective cohort study, in which 215 new consecutive referrals (age 77.4 SD 6.0) of a geriatric outpatient clinic of a Dutch university hospital were included. During the previous year, 139 had experienced a fall. At baseline, all patients underwent routine two-dimensional and Doppler echocardiography. Falls were recorded during a three-month follow-up. Multivariate adjustment for compounders was performed with a Cox proportional hazards model. 557 patients (26%) fell at least once during follow-up. The adjusted hazard ratio of a fall during follow-up was 135 (95% Cl, 1.08-1.71) for pulmonary hypertension, 1.66 (95% Cl, 1.01 to 2.89) for 4-initial regurgitation, 2.41 (95% Cl, 1.32 to 4.37) for tricuspid regurgitation and 1.76 (95% Cl, 1.03 to 3.01) for pulmonary regurgitation. For aoitic regurgitation the risk of a fall was also increased, but non-significantly. (hazard ratio, 1.57 [95% Cl 0.85 to 2.92]). Trend analysis of the severity of the difterent regurgitations showed a significant relationship for mitral, tricuspid and pulmonary valve regurgitation and pulmonary hypertension. Conclusions. Echo(Dopler)cardiography can be useful in order to identify risk indicators for falling. Presence of pulmonary hypertension or regurgitation of mitral, tricuspid or pulmonary valves was associated with a higher fall risk. Our study indicates that the diagnostic work-up for falls in older adults might be improved by adding an echo(Doppler)cardiogram in selected groups
The NOX toolbox: validating the role of NADPH oxidases in physiology and disease
Reactive oxygen species (ROS) are cellular signals but also disease triggers; their relative excess (oxidative stress) or shortage (reductive stress) compared to reducing equivalents are potentially deleterious. This may explain why antioxidants fail to combat diseases that correlate with oxidative stress. Instead, targeting of disease-relevant enzymatic ROS sources that leaves physiological ROS signaling unaffected may be more beneficial. NADPH oxidases are the only known enzyme family with the sole function to produce ROS. Of the catalytic NADPH oxidase subunits (NOX), NOX4 is the most widely distributed isoform. We provide here a critical review of the currently available experimental tools to assess the role of NOX and especially NOX4, i.e. knock-out mice, siRNAs, antibodies, and pharmacological inhibitors. We then focus on the characterization of the small molecule NADPH oxidase inhibitor, VAS2870, in vitro and in vivo, its specificity, selectivity, and possible mechanism of action. Finally, we discuss the validation of NOX4 as a potential therapeutic target for indications including stroke, heart failure, and fibrosis
Uber den elektronenmikroskopischen nachweis von viruspartikeln bei der myeloischen leukamie der maus nach injektion zellfreier tumorfiltrate.
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