155 research outputs found
Performance predictions for a laser intensified thermal beam for use in high resolution Focused Ion Beam instruments
Photo-ionization of a laser-cooled and compressed atomic beam from a
high-flux thermal source can be used to create a high-brightness ion beam for
use in Focus Ion Beam (FIB) instruments. Here we show using calculations and
Doppler cooling simulations that an atomic rubidium beam with a brightness of
at a current of 1 nA can be created using a
compact 5 cm long 2D magneto-optical compressor which is more than an order of
magnitude better than the current state of the art Liquid Metal Ion Source.Comment: 8 pages, 7 figures submitted to: Phys. Rev.
Precision spectroscopy of helium in a magic wavelength optical dipole trap
Improvements in both theory and frequency metrology of few-electron systems
such as hydrogen and helium have enabled increasingly sensitive tests of
quantum electrodynamics (QED), as well as ever more accurate determinations of
fundamental constants and the size of the nucleus. At the same time advances in
cooling and trapping of neutral atoms have revolutionized the development of
increasingly accurate atomic clocks. Here, we combine these fields to reach the
highest precision on an optical tranistion in the helium atom to date by
employing a Bose-Einstein condensate confined in a magic wavelength optical
dipole trap. The measured transition accurately connects the ortho- and
parastates of helium and constitutes a stringent test of QED theory. In
addition we test polarizability calculations and ultracold scattering
properties of the helium atom. Finally, our measurement probes the size of the
nucleus at a level exceeding the projected accuracy of muonic helium
measurements currently being performed in the context of the proton radius
puzzle
A simple 2 W continuous-wave laser system for trapping ultracold metastable helium atoms at the 319.8 nm magic wavelength
Mid-circuit qubit measurement and rearrangement in a Yb atomic array
Measurement-based quantum error correction relies on the ability to determine
the state of a subset of qubits (ancillae) within a processor without revealing
or disturbing the state of the remaining qubits. Among neutral-atom based
platforms, a scalable, high-fidelity approach to mid-circuit measurement that
retains the ancilla qubits in a state suitable for future operations has not
yet been demonstrated. In this work, we perform imaging using a
narrow-linewidth transition in an array of tweezer-confined Yb atoms to
demonstrate nondestructive state-selective and site-selective detection. By
applying site-specific light shifts, selected atoms within the array can be
hidden from imaging light, which allows a subset of qubits to be measured while
causing only percent-level errors on the remaining qubits. As a
proof-of-principle demonstration of conditional operations based on the results
of the mid-circuit measurements, and of our ability to reuse ancilla qubits, we
perform conditional refilling of ancilla sites to correct for occasional atom
loss, while maintaining the coherence of data qubits. Looking towards true
continuous operation, we demonstrate loading of a magneto-optical trap with a
minimal degree of qubit decoherence.Comment: 9 pages, 6 figure
The Key Events Dose-Response Framework: Its Potential for Application to Foodborne Pathogenic Microorganisms
The Key Events Dose-Response Framework (KEDRF) is an analytical approach that facilitates the use of currently available data to gain insight regarding dose-response relationships. The use of the KEDRF also helps identify critical knowledge gaps that once filled, will reduce reliance on assumptions. The present study considers how the KEDRF might be applied to pathogenic microorganisms, using fetal listeriosis resulting from maternal ingestion of food contaminated with L. monocytogenes as an initial example. Major biological events along the pathway between food ingestion and the endpoint of concern are systematically considered with regard to dose (i.e., number of organisms), pathogen factors (e.g., virulence), and protective host mechanisms (e.g., immune response or other homeostatic mechanisms). It is concluded that the KEDRF provides a useful structure for systematically evaluating the complex array of host and pathogen factors that influence the dose-response relationship. In particular, the KEDRF supports efforts to specify and quantify the sources of variability, a prerequisite to strengthening the scientific basis for food safety decision making
National laboratory-based surveillance system for antimicrobial resistance: a successful tool to support the control of antimicrobial resistance in the Netherlands
An important cornerstone in the control of antimicrobial resistance (AMR) is a well-designed quantitative system for the surveillance of spread and temporal trends in AMR. Since 2008, the Dutch national AMR surveillance system, based on routine data from medical microbiological laboratories (MMLs), has developed into a successful tool to support the control of AMR in the Netherlands. It provides background information for policy making in public health and healthcare services, supports development of empirical antibiotic therapy guidelines and facilitates in-depth research. In addition, participation of the MMLs in the national AMR surveillance network has contributed to sharing of knowledge and quality improvement. A future improvement will be the implementation of a new semantic standard together with standardised data transfer, which will reduce errors in data handling and enable a more real-time surveillance. Furthermore, the
Molecular characteristics of carbapenemase-producing Enterobacterales in the Netherlands; results of the 2014–2018 national laboratory surveillance
Objectives: Carbapenem resistance mediated by mobile genetic elements has emerged worldwide and has become a major public health threat. To gain insight into the molecular epidemiology of carbapenem resistance in The Netherlands, Dutch medical microbiology laboratories are requested to submit suspected carbapenemase-producing Enterobacterales (CPE) to the National Institute for Public Health and the Environment as part of a national surveillance system. Methods: Meropenem MICs and species identification were confirmed by E-test and MALDI-TOF and carbapenemase production was assessed by the Carbapenem Inactivation Method. Of all submitted CPE, one species/carbapenemase gene combination per person per year was subjected to next-generation sequencing (NGS). Results: In total, 1838 unique isolates were received between 2014 and 2018, of which 892 were unique CPE isolates with NGS data available. The predominant CPE species were Klebsiella pneumoniae (n = 388, 43%), Escherichia coli (n = 264, 30%) and Enterobacter cloacae complex (n = 116, 13%). Various carbapenemase alleles of the same carbapenemase gene resulted in different susceptibilities to meropenem and this effect varied between species. Analyses of NGS data showed variation of prevalence of carbapenemase alleles over time with blaOXA-48 being predominant (38%, 336/892), followed by blaNDM-1 (16%, 145/892). For the first time in the Netherlands, blaOXA-181, blaOXA-232 and blaVIM-4 were detected. The genetic background of K. pneumoniae and E. coli isolates was highly diverse. Conclusions: The CPE population in the Netherlands is diverse, suggesting multiple introductions. The predominant carbapenemase alleles are blaOXA-48 and blaNDM-1. There was a clear association between species, carbapenemase allele and susceptibility to meropenem
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