171 research outputs found
Laser-controlled fluorescence in two-level systems
The ability to modify the character of fluorescent emission by a laser-controlled, optically nonlinear process has recently been shown theoretically feasible, and several possible applications have already been identified. In operation, a pulse of off-resonant probe laser beam, of sufficient intensity, is applied to a system exhibiting fluorescence, during the interval of excited- state decay following the initial excitation. The result is a rate of decay that can be controllably modified, the associated changes in fluorescence behavior affording new, chemically specific information. In this paper, a two-level emission model is employed in the further analysis of this all-optical process; the results should prove especially relevant to the analysis and imaging of physical systems employing fluorescent markers, these ranging from quantum dots to green fluorescence protein. Expressions are presented for the laser-controlled fluorescence anisotropy exhibited by samples in which the fluorophores are randomly oriented. It is also shown that, in systems with suitably configured electronic levels and symmetry properties, fluorescence emission can be produced from energy levels that would normally decay nonradiatively. © 2010 American Chemical Society
Design and Bolometer Characterization of the SPT-3G First-year Focal Plane
During the austral summer of 2016-17, the third-generation camera, SPT-3G,
was installed on the South Pole Telescope, increasing the detector count in the
focal plane by an order of magnitude relative to the previous generation.
Designed to map the polarization of the cosmic microwave background, SPT-3G
contains ten 6-in-hexagonal modules of detectors, each with 269 trichroic and
dual-polarization pixels, read out using 68x frequency-domain multiplexing.
Here we discuss design, assembly, and layout of the modules, as well as early
performance characterization of the first-year array, including yield and
detector properties.Comment: Conference proceeding for Low Temperature Detectors 2017. Accepted
for publication: 27 August 201
To defer or not to defer? A German longitudinal multicentric assessment of clinical practice in urology during the COVID-19 pandemic
Introduction After the outbreak of COVID-19 unprecedented changes in the healthcare systems worldwide were necessary resulting in a reduction of urological capacities with postponements of consultations and surgeries. Material and methods An email was sent to 66 urological hospitals with focus on robotic surgery (RS) including a link to a questionnaire (e.g. bed/staff capacity, surgical caseload, protection measures during RS) that covered three time points: a representative baseline week prior to COVID-19, the week of March 16th-22nd and April 20th-26th 2020. The results were evaluated using descriptive analyses. Results 27 out of 66 questionnaires were analyzed (response rate: 41%). We found a decrease of 11% in hospital beds and 25% in OR capacity with equal reductions for endourological, open and robotic procedures. Primary surgical treatment of urolithiasis and benign prostate syndrome (BPS) but also of testicular and penile cancer dropped by at least 50% while the decrease of surgeries for prostate, renal and urothelial cancer (TUR-B and cystectomies) ranged from 15 to 37%. The use of personal protection equipment (PPE), screening of staff and patients and protection during RS was unevenly distributed in the different centers\u2013however, the number of COVID-19 patients and urologists did not reach double digits. Conclusion The German urological landscape has changed since the outbreak of COVID-19 with a significant shift of high priority surgeries but also continuation of elective surgical treatments. While screening and staff protection is employed heterogeneously, the number of infected German urologists stays low
Low spin spectroscopy of neutron-rich 43,44,45Cl via {\beta} and (\beta}n decay
{\beta} decay of neutron-rich isotopes 43,45 S,studied at the National
Superconducting Cyclotron Laboratory is reported here. {\beta} delayed {\gamma}
transitions were detected by an array of 16 clover detectors surrounding the
Beta Counting Station which consists of a 40x40 Double Sided Silicon Strip
Detector followed by a Single Sided Silicon Strip Detector. {\beta} decay
half-lives have been extracted for 43,45 S by correlating implants and decays
in the pixelated implant detector with further coincidence with {\gamma}
transitions in the daughter nucleus. The level structure of 43,45 Cl is
expanded by the addition of 20 new {\gamma} transitions in 43Cl and 8 in 45 Cl
with the observation of core excited negative-parity states for the first time.
For 45 S decay, a large fraction of the {\beta} decay strength goes to delayed
neutron emission populating states in 44 Cl which are also presented.
Comparison of experimental observations is made to detailed shell-model
calculations using the SDPFSDG-MU interaction to highlight the role of the
diminished N = 28 neutron shell gap and the near degeneracy of the proton s 1/2
and d 3/2 orbitals on the structure of the neutron-rich Cl isotopes. The
current work also provides further support to a ground state spin-parity
assignment of 3/2 + in 45 Cl
Protein adsorption on preadsorbed polyampholytic monolayers
The adsorption behaviour of five different globular proteins on pure silicon substrates and on preadsorbed polyampholytic monolayers has been investigated as a function of protein concentration. The prelayers were prepared by adsorption of the ampholytic diblock copolymer poly(methacrylic acid)-block-poly ((dimethylamino)ethyl methacrylate) (PMAA-b-PDMAEMA). This polyampholyte adsorbs in densely packed micelles directly from aqueous solution. Ellipsometry was used to determine the amount of adsorbed polyampholyte and protein. While ATR-IR spectroscopy gives information about the adsorption and desorption behaviour of the preadsorbed polyampholytic layer, the lateral structures of the dried films were investigated by scanning force microscopy (SFM). The amount of protein adsorbed was found to be strongly influenced by the preadsorbed polyampholyte compared to the adsorption on the pure silicon substrates. No displacement of the polyampholyte by the proteins was detected. In most cases the protein adsorption was reduced by the preadsorbed polyampholytic layer. The observed trends are explained by the change in electrostatic and hydrophilic characteristics of the substrates. Furthermore, the entropy of adsorption has to be taken into account.Peer reviewe
Microsecond Isomer at the N=20 Island of Shape Inversion Observed at FRIB
Excited-state spectroscopy from the first Facility for Rare Isotope Beams
(FRIB) experiment is reported. A 24(2)-s isomer was observed with the FRIB
Decay Station initiator (FDSi) through a cascade of 224- and 401-keV
rays in coincidence with nuclei. This is the only known
microsecond isomer () in the
region. This nucleus is at the heart of the island of shape inversion
and is at the crossroads of spherical shell-model, deformed shell-model, and ab
initio theories. It can be represented as the coupling of a proton hole and
neutron particle to , .
This odd-odd coupling and isomer formation provides a sensitive measure of the
underlying shape degrees of freedom of , where the onset of
spherical-to-deformed shape inversion begins with a low-lying deformed
state at 885 keV and a low-lying shape-coexisting state at 1058 keV. We
suggest two possible explanations for the 625-keV isomer in Na: a
spherical shape isomer that decays by or a deformed spin isomer that
decays by . The present results and calculations are most consistent with
the latter, indicating that the low-lying states are dominated by deformation.Comment: 7 pages, 5 figures, accepted by Physical Review Letter
Performance of Al-Mn Transition-Edge Sensor Bolometers in SPT-3G
SPT-3G is a polarization-sensitive receiver, installed on the South Pole
Telescope, that measures the anisotropy of the cosmic microwave background
(CMB) from degree to arcminute scales. The receiver consists of ten
150~mm-diameter detector wafers, containing a total of 16,000 transition-edge
sensor (TES) bolometers observing at 95, 150, and 220 GHz. During the 2018-2019
austral summer, one of these detector wafers was replaced by a new wafer
fabricated with Al-Mn TESs instead of the Ti/Au design originally deployed for
SPT-3G. We present the results of in-lab characterization and on-sky
performance of this Al-Mn wafer, including electrical and thermal properties,
optical efficiency measurements, and noise-equivalent temperature. In addition,
we discuss and account for several calibration-related systematic errors that
affect measurements made using frequency-domain multiplexing readout
electronics.Comment: 9 pages, 5 figures, submitted to the Journal of Low Temperature
Physics: LTD18 Special Editio
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