625 research outputs found
Experimental exploration of the optomechanical attractor diagram and its dynamics
We demonstrate experimental exploration of the attractor diagram of an
optomechanical system where the optical forces compensate for the mechanical
losses. In this case stable self-induced oscillations occur but only for
specific mirror amplitudes and laser detunings. We demonstrate that we can
amplify the mechanical mode to an amplitude 500 times larger than the thermal
amplitude at 300K. The lack of unstable or chaotic motion allows us to
manipulate our system into a non-trivial steady state and explore the dynamics
of self-induced oscillations in great detail.Comment: 6 pages, 4 figure
Coherent Optomechanical State Transfer between Disparate Mechanical Resonators
Hybrid quantum systems have been developed with various mechanical, optical
and microwave harmonic oscillators. The coupling produces a rich library of
interactions including two mode squeezing, swapping interactions, back-action
evasion and thermal control. In a multimode mechanical system, coupling
resonators of different scales (both in frequency and mass) leverages the
advantages of each resonance. For example: a high frequency, easily manipulated
resonator could be entangled with a low frequency massive object for tests of
gravitational decoherence. Here we demonstrate coherent optomechanical state
swapping between two spatially and frequency separated resonators with a mass
ratio of 4. We find that, by using two laser beams far detuned from an optical
cavity resonance, efficient state transfer is possible through a process very
similar to STIRAP (Stimulated Raman Adiabatic Passage) in atomic physics.
Although the demonstration is classical, the same technique can be used to
generate entanglement between oscillators in the quantum regime
High-Q nested resonator in an actively stabilized optomechanical cavity
Experiments involving micro- and nanomechanical resonators need to be
carefully designed to reduce mechanical environmental noise. A small scale
on-chip approach is to add an additional resonator to the system as a
mechanical low-pass filter. Unfortunately, the inherent low frequency of the
low-pass filter causes the system to be easily excited mechanically. Fixating
the additional resonator ensures that the resonator itself can not be excited
by the environment. This, however, negates the purpose of the low-pass filter.
We solve this apparent paradox by applying active feedback to the resonator,
thereby minimizing the motion with respect the front mirror of an
optomechanical cavity. Not only does this method actively stabilize the cavity
length, but it also retains the on-chip vibration isolation.Comment: Minor adjustments mad
An Abbreviated Method for the Quality Control of Pollen Counters
We present an abbreviated method for conducting large scale quality control (QC) exercises over limited time periods, which was used for examining the proficiency of technicians involved in the electronic Pollen Information Network (ePIN). The goal was for technicians to have their analysis skills evaluated at least twice: (1) by having at least one of their slides successfully checked by other counters in the ePIN network and (2) by successfully examining at least one additional slide from other sites. Success was judged as a relative difference (RDif %) ≤ 30% between the two daily average pollen concentrations. A total of 21 sites participated in the ePIN QC exercise. All of the results for total pollen had RDif % 30%, three for Betula and two for Poaceae pollen. Of these, three were slides containing < 40 pollen/m3 daily average and two were for sites that had microscopes with small fields of view and examined < 10% of the slide surface. More than 80% of the participants had at least two slides successfully checked by someone else in the network, and all of the participants had one slide successfully examined. The latter is comparable to a traditional ring test where only one slide is sent to participating sites. The method described here enabled a large number of technicians to be examined in a short period of time and represents a viable alternative to other approaches that can take many months to complete
Where photons meet phonons
We
investigate how radiation pressure can be used to influence the mechanical
motion of a micro-mirror suspended from springs. This trampoline resonator is
part of an optical Fabry-Perot cavity. By tuning the laser frequency with
respect to the optical resonance, we are able to optically cool the mechanical
motion of the resonator. When combining this optical cooling with cryogenic
cooling techniques, we are able to bring the mechanical resonator close to the
quantum mechanical ground state. This is a requirement for future experiments
to investigate the fundamentals of quantum mechanics. Quantum Matter and Optic
Vibration isolation with high thermal conductance for a cryogen-free dilution refrigerator
We present the design and implementation of a mechanical low-pass filter
vibration isolation used to reduce the vibrational noise in a cryogen-free
dilution refrigerator operated at 10 mK, intended for scanning probe
techniques. We discuss the design guidelines necessary to meet the competing
requirements of having a low mechanical stiffness in combination with a high
thermal conductance. We demonstrate the effectiveness of our approach by
measuring the vibrational noise levels of an ultrasoft mechanical resonator
positioned above a SQUID. Starting from a cryostat base temperature of 8 mK,
the vibration isolation can be cooled to 10.5 mK, with a cooling power of 113
W at 100 mK. We use the low vibrations and low temperature to demonstrate
an effective cantilever temperature of less than 20 mK. This results in a force
sensitivity of less than 500 zN/, and an integrated
frequency noise as low as 0.4 mHz in a 1 Hz measurement bandwidth
Release of LTB4-like pollen associated lipid mediators (PALMLTB4) from birch pollen in different air polluted areas in West and Southern Germany [Abstract]
Environmental exposure and sensitization patterns in a Swiss alpine pediatric cohort
Background
The level of environmental exposure throughout life may contribute to the prevalence of allergic sensitization and allergic disease. The alpine climate has been considered a healthy climate with little allergen exposure and pollution. We conducted a cross-sectional study to investigate local environmental exposure and concomitant prevalence of allergic sensitization among local school children born and raised in an alpine environment.
Methods
Clinical and demographic data were collected with a questionnaire. Allergen content was assessed in residential settled dust samples, lifetime exposure to pollen and air pollution was calculated using data from national pollen and air pollution monitoring stations, and the allergic sensitization profile was determined with component resolved diagnostics (ISAC®). Univariate and multivariate regression models were used to estimate the relation between exposure and sensitization.
Results
In a cohort of children born and raised in an alpine environment, sensitization to aeroallergens is quite common (38%), especially to grass (33%) and cat (16%). House dust mite allergen was detected in up to 38% of residential dust samples, but sensitization to HDM was low (2.5%). Pollutant levels were low, but an increasing trend was observed in the amount of ozone and PM10. Living close to a busy road was associated with increased odds OR (95% CI) for being sensitized to any allergen 2.7 (1.0–7.2), to outdoor allergens 2.8 (1.1–7.1) and being sensitized plus reporting symptoms of rhinoconjunctivitis 4.4 (1.3–14.8) and asthma 5.5 (1.4–21). Indoor living conditions, including the presence of visible mold, increased the odds of being sensitized to indoor allergens (1.9 (1.1–3.2) and being sensitized plus reporting symptoms of rhinoconjunctivitis 1.9 (1.0–3.6) and asthma 2.1 (1.0–4.1).
Conclusion
In a healthy alpine environment, pollution might still be an important factor contributing to allergic sensitization
Q. rotundifolia and P. hybrida pollen extracts induced basophil degranulation: study using a cell line expressing human FcERI.
Nowadays skin prick tests remain the favourite methodology in allergy diagnosis to aeroallergens. These tests, however, cause discomfort to the patient. Several biochemical methods are available but have limited diagnostic power as biological response, hence allergic reaction, is not predicted by these tests. A biological assay allowing the evaluation of allergic response to allergens is lacking. The aim of this work was to investigate the value of a rat basophil cell line expressing human high affinity IgE receptor (FcERI) for the evaluation of specific response to allergens.
FACS analysis was used to determine FcERI expression (APC-A). Pollen extracts from different species were prepared with ammonium bicarbonate buffer, lyophilized and stored at -80ÂşC until use. Batches of RBL-h21 cells were sensitized with selected pools of human sera (purified IgE was used as control) and were stimulated with pollen extracts or Anti-IgE antibody. Histamine release (% degranulation) was determined a Ăź-hesoaminidase (tracer) assay.
Batches of RBL-h21 cells sensitized (human sera) to grasses (D. glomerata), olive, oak or plane exhibited selective and dose-dependent degranulation upon selective stimulation with pollen extracts in the range of 1-200ÎĽg/mL. Maximal degranulation (>25%) was observed for 50, 120 and 62ÎĽg/mL for grass, oak and plane, respectively, while the lowest concentration with observed effect was 12ÎĽg/mL for any of the extracts.
The results show that RBL-h21 cells sensitized with human sera exhibit specific and dose-dependent degranulation upon stimulation with pollen extract containing allergens suggesting this bioassay may constitute a useful tool to evaluate allergic responses both for research and/or diagnostics
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