45 research outputs found
Controlling Stray Electric Fields on an Atom Chip for Rydberg Experiments
Experiments handling Rydberg atoms near surfaces must necessarily deal with
the high sensitivity of Rydberg atoms to (stray) electric fields that typically
emanate from adsorbates on the surface. We demonstrate a method to modify and
reduce the stray electric field by changing the adsorbates distribution. We use
one of the Rydberg excitation lasers to locally affect the adsorbed dipole
distribution. By adjusting the averaged exposure time we change the strength
(with the minimal value less than at
from the chip) and even the sign of the perpendicular field component. This
technique is a useful tool for experiments handling Ryberg atoms near surfaces,
including atom chips
Magnetic-film atom chip with 10 m period lattices of microtraps for quantum information science with Rydberg atoms
We describe the fabrication and construction of a setup for creating lattices
of magnetic microtraps for ultracold atoms on an atom chip. The lattice is
defined by lithographic patterning of a permanent magnetic film. Patterned
magnetic-film atom chips enable a large variety of trapping geometries over a
wide range of length scales. We demonstrate an atom chip with a lattice
constant of 10 m, suitable for experiments in quantum information science
employing the interaction between atoms in highly-excited Rydberg energy
levels. The active trapping region contains lattice regions with square and
hexagonal symmetry, with the two regions joined at an interface. A structure of
macroscopic wires, cut out of a silver foil, was mounted under the atom chip in
order to load ultracold Rb atoms into the microtraps. We demonstrate
loading of atoms into the square and hexagonal lattice sections simultaneously
and show resolved imaging of individual lattice sites. Magnetic-film lattices
on atom chips provide a versatile platform for experiments with ultracold
atoms, in particular for quantum information science and quantum simulation.Comment: 7 pages, 7 figure
Not your average biker; Criminal careers of members of Dutch outlaw motorcycle gangs
Based on criminal career data of a sample of 601 police-identified outlaw motorcycle gang members and an age-matched comparison group of 300 non-gang affiliated motorcycle owners, the current analysis examines various dimensions of the criminal careers of outlaw bikers, including participation, onset, frequency, and crime mix. Results show that Dutch outlaw bikers are more often convicted than the average Dutch motorcyclist, and that these convictions not only pertain to minor offenses but also to serious and violent crimes. We find that outlaw bikers’ criminal careers differ from that of the average Dutch motorcyclist already during the juvenile and early adult years, but also – and more so – during the adult years. These results fit the enhancement hypothesis of gang membership and suggest that both selection of crime prone individuals in outlaw motorcycle gangs and facilitation of criminal behavior whilst in the gang are taking place.Criminal Justice: Legitimacy, accountability, and effectivit
Chinese organized crime and situational context: comparing human smuggling and synthetic drugs trafficking
This article criticizes the 'ethnic' conception of organized crime and puts forward an alternative view that does not put ethnicity first, but rather social networks and situational context. It focuses upon Chinese organized crime, a phenomenon where the preoccupation with ethnicity is paramount, and compares findings from extensive research into two different transnational criminal activities that are carried out by Chinese offenders in the Netherlands. The first topic, human smuggling, is well researched, whereas research into the second topic, trafficking in precursors (the basic ingredients for the production of synthetic drugs), is largely lacking. The article highlights the major theoretical and empirical similarities and differences between these two criminal activities and discusses the relevance of the main findings for theory and research
Magnetic-film atom chip with 10 μm period lattices of microtraps for quantum information science with Rydberg atoms
Glutamate Uptake Triggers Transporter-Mediated GABA Release from Astrocytes
Background: Glutamate (Glu) and c-aminobutyric acid (GABA) transporters play important roles in regulating neuronal activity. Glu is removed from the extracellular space dominantly by glial transporters. In contrast, GABA is mainly taken up by neurons. However, the glial GABA transporter subtypes share their localization with the Glu transporters and their expression is confined to the same subpopulation of astrocytes, raising the possibility of cooperation between Glu and GABA transport processes. Methodology/Principal Findings: Here we used diverse biological models both in vitro and in vivo to explore the interplay between these processes. We found that removal of Glu by astrocytic transporters triggers an elevation in the extracellular level of GABA. This coupling between excitatory and inhibitory signaling was found to be independent of Glu receptor-mediated depolarization, external presence of Ca2+ and glutamate decarboxylase activity. It was abolished in the presence of non-transportable blockers of glial Glu or GABA transporters, suggesting that the concerted action of these transporters underlies the process. Conclusions/Significance: Our results suggest that activation of Glu transporters results in GABA release through reversal of glial GABA transporters. This transporter-mediated interplay represents a direct link between inhibitory and excitatory neurotransmission and may function as a negative feedback combating intense excitation in pathological conditions such as epilepsy or ischemia
‘But the Dutch would call it exploitation’. Crimmigration and the moral economy of the Chinese catering industry in the Netherlands
Approximation of a physiologically structured population model with seasonal reproduction by a stage-structured biomass model
Principal-Agency Theory in Illegal Markets: Cooperation and Conflict Among Chinese Loansharks
Adsorbate dynamics on a silica-coated gold surface measured by Rydberg Stark spectroscopy
Trapping a Rydberg atom close to a surface is an important step towards the
realisation of many proposals of quantum information or hybrid quantum systems.
One of the challenges in these experiments is to overcome the electric field
emanating from contaminations on the surface. Here we report on measurements of
an electric field created by Rb atoms absorbed on a 25nm thick layer
of SiO, covering a 90nm layer of Au. The electric field is measured
using a two-photon transition to the 23 and 25 state. The
electric field value that we measure is higher than typical values measured
above metal surfaces, but is consistent with other measurements above SiO
surfaces. In addition, we measure the temporal behaviour of the field and
observe that we can reduce it in a single experimental cycle, using UV light or
by mildly heating the surface, whereas the buildup of the field takes thousands
of cycles. We explain these results by a change in the ad-atoms distribution on
the surface. These results indicate that the stray electric field can be
reduced, opening new possibilities for experiments with trapped Rydberg atoms
near surfaces.Comment: 9 pages, 9 figure