52 research outputs found
Measurement of Radio-Frequency Radiation Pressure
We perform measurements of the radiation pressure of a radio-frequency (RF)
electromagnetic field which may lead to a new SI-traceable power calibration.
There are several groups around the world investigating methods to perform more
direct SI traceable measurement of RF power (where RF is defined to range from
100s of MHz to THz). A measurement of radiation pressure offers the possibility
for a power measure traceable to the kilogram and to Planck's constant through
the redefined SI. Towards this goal, we demonstrate the ability to measure the
radiation pressure/force carried in a field at 15~GHz.Comment: 2 pages 4 figure
Phase-Resolved Rydberg Atom Field Sensing using Quantum Interferometry
Although Rydberg atom-based electric field sensing provides key advantages
over traditional antenna-based detection, it remains limited by the need for a
local oscillator (LO) for low-field and phase resolved detection. In this work,
we demonstrate that closed-loop quantum interferometric schemes can be used to
generate a system-internal reference that can directly replace an external LO
for Rydberg field sensing. We reveal that this quantum-interferometrically
defined internal reference phase and frequency can be used analogously to a
traditional LO for atom-based down-mixing to an intermediate frequency for
lock-in phase detection. We demonstrate that this LO-equivalent functionality
provides analogous benefits to an LO, including full 360 phase
resolution as well as improved sensitivity. The general applicability of this
approach is confirmed by demodulating a four phase-state signal broadcast on
the atoms. Our approach opens up new sensing schemes and provides a clear path
towards all-optical Rydberg atom sensing implementations
Sensitivity Comparison of Two-photon vs Three-photon Rydberg Electrometry
We investigate the sensitivity of three-photon EIT in Rydberg atoms to radio
frequency detection and compare it against conventional two-photon systems.
Specifically, we model the 4-level and 5-level atomic system and compare how
the transmission of the probe changes with different powers of the lasers used
and strengths of the RF field. In this model, we also define a sensitivity
metric to best relate to the operation of the current best experimental
implementation based on shot noise limited detection. We find that the
three-photon system boasts much narrower line widths compared to the
conventional two-photon EIT. However, these narrow line features do not align
with the regions of the best sensitivity. In addition to this, we calculate the
expected sensitivity for the two-photon Rydberg sensor and find that the best
achievable sensitivity is over an order of magnitude better than the current
measured values of 5 uV/m/Hz. However, by accounting for the additional noise
sources in the experiment and the quantum efficiency of the photo-detectors,
the values are in good agreement.Comment: 9 pages, 6 figure
Detection of HF and VHF Fields through Floquet Sideband Gaps by `Rabi Matching' Dressed Rydberg Atoms
Radio frequencies in the HF and VHF (3 MHz to 300 MHz) bands are challenging
for Rydberg atom-based detection schemes, as resonant detection requires
exciting the atoms to extremely high energy states. We demonstrate a method for
detecting and measuring radio frequency (RF) carriers in the HF and VHF bands
via a controlled Autler-Townes line splitting. Using a resonant, high-frequency
(GHz) RF field, the absorption signal from Townes-Merrit sidebands created by a
low frequency, non-resonant RF field can be enhanced. Notably, this technique
uses a measurement of the optical frequency separation of an avoided crossing
to determine the amplitude of a non-resonant, low frequency RF field. This
technique also provides frequency-selective measurements of low frequency RF
electric fields. To show this, we demonstrate amplitude modulated signal
transduction on a low frequency VHF carrier. We further demonstrate reception
of multiple tones simultaneously, creating a Rydberg `spectrum analyzer' over
the VHF range.Comment: Data for figures can be found at:
https://datapub.nist.gov/od/id/mds2-285
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Role of airway Ilc2 And Ilc3 compared to Th2 And Th17 cells in paediatric severe therapy resistant asthma (stra)
Infection and inflammation in induced sputum from preschool children with chronic airways diseases.
BACKGROUND: We hypothesized airway inflammation can be detected non-invasively by induced sputum (IS) or peripheral blood eosinophilia, and IS can detect bacterial and viral infection in preschool children with airway disease, with results comparable to broncho-alveolar lavage (BAL). METHODS: Preschool children with cystic fibrosis, recurrent wheeze, or wet cough underwent IS with nebulized hypertonic saline, chest physiotherapy, and oropharyngeal suction. Samples were analyzed for inflammation by cytology and bacterial culture, viral detection by PCR. Results were compared to BAL and blood in a sub-group undergoing clinically indicated bronchoscopy. RESULTS: 64 children (median age 33 [7-76] months) underwent IS without adverse events. IS was obtained from 61/64. Twenty out of sixty-four underwent BAL and IS, no IS was obtained in 2/23. Thirteen out of twenty-one (62%) had matching bacteria and viruses, 4/21 had positive BAL bacterial growth with negative IS, and 3/21 had negative BAL growth with positive IS. 67% of sputum samples were processed for cytology, 46% had <80% squamous cells; the proportion of squamous cells reduced with increasing age (r = -0.55, P < 0.01). IS was significantly more neutrophilic and less eosinophilic than BAL; 2/21 IS samples contained eosinophils compared to 17/23 BAL. There was a positive correlation between blood and BAL eosinophilia (r = 0.75, P < 0.01). CONCLUSION: IS from preschool children can be used to assess infection. BAL and IS culture concurred in approximately two-thirds. However, inflammation was measureable in only one-third of IS samples and the cell differential was predominantly neutrophilic compared to BAL. Blood eosinophils may provide a better reflection of lower airway eosinophilia in this age group. Pediatr Pulmonol. 2016;51:778-786. © 2015 WileyPeriodicals, Inc
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