1,488 research outputs found
Designs of magnetic atom-trap lattices for quantum simulation experiments
We have designed and realized magnetic trapping geometries for ultracold
atoms based on permanent magnetic films. Magnetic chip based experiments give a
high level of control over trap barriers and geometric boundaries in a compact
experimental setup. These structures can be used to study quantum spin physics
in a wide range of energies and length scales. By introducing defects into a
triangular lattice, kagome and hexagonal lattice structures can be created.
Rectangular lattices and (quasi-)one-dimensional structures such as ladders and
diamond chain trapping potentials have also been created. Quantum spin models
can be studied in all these geometries with Rydberg atoms, which allow for
controlled interactions over several micrometers. We also present some
nonperiodic geometries where the length scales of the traps are varied over a
wide range. These tapered structures offer another way to transport large
numbers of atoms adiabatically into subwavelength traps and back.Comment: 9 pages, 10 figure
Cold trapped atoms detected with evanescent waves
We demonstrate the in situ detection of cold 87 Rb atoms near a dielectric
surface using the absorption of a weak, resonant evanescent wave. We have used
this technique in time of flight experiments determining the density of atoms
falling on the surface. A quantitative understanding of the measured curve was
obtained using a detailed calculation of the evanescent intensity distribution.
We have also used it to detect atoms trapped near the surface in a
standing-wave optical dipole potential. This trap was loaded by inelastic
bouncing on a strong, repulsive evanescent potential. We estimate that we trap
1.5 x 10 4 atoms at a density 100 times higher than the falling atoms.Comment: 5 pages, 3 figure
Ontwikkeling en implementatie van geĂŻntegreerde bestrijding in zomerbloemen : toepassing van beschikbare producten en ontwikkeling van nieuwe natuurlijke vijanden
In 2008 en 2009 werden loslatingen verricht van de roofmijten Neoseiulus cucumeris en Amblyseius andersoni, soms aangevuld met Phytoseiulus persimilis, in de zomerbloemen rozenbottel, chrysant, Veronica, Alchemilla en Delphinium. Hierbij bleek dat roofmijten zich niet in alle gewassen in gelijke mate vestigen. In Alchemilla en Delphinium bleek al spontaan Neoseiulus cucumeris voor te kunnen komen. Als in deze gewassen nog geen roofmijten voorkomen, zal introductie van N. cucumeris zeker slagen, mits er geen breedwerkende middelen worden toegepast. Vooral Alchemilla bleek een goede roofmijtenplant te zijn. Behalve Neoseiulus cucumeris werden ook andere soorten gevonden. Roofmijten die in de handel zijn tegen spint, Phytoseiulus persimilis en Neoseiulus californicus, vestigen zich eveneens goed in dit gewas, in tegenstelling tot Amblyseius andersoni. Verder kunnen spontaan andere natuurlijke vijanden van plagen voorkomen: roofwantsen, gaasvliegen en galmuggen. Trips nam in beide jaren af gedurende de teelt of bleef op een laag niveau. Neoseiulus alpinus is een roofmijt, die eerder is verzameld van Alchemilla en in kweek genomen. Een loslating van deze roofmijt in Alchemilla slaagde in 2008 niet, maar in 2009 wel. In Delphinium was in 2008 vanaf het begin van de waarnemingen Neoseiulus cucumeris in het gewas aanwezig. Na introductie van Amblyseius andersoni werd ook deze soort teruggevonden. Spint kwam in 2008 niet tot ontwikkeling. Buiten de proef kwam plaatselijk cyclamenmijt voor. In 2009 werd in Delphinium zwavel verdampt tegen echte meeldauw. Er was geen goede vestiging van roofmijten in het gewas, ook niet van de roofmijt Phytoseiulus persimilis, waardoor chemische bestrijding van spint noodzakelijk was. In Veronica, chrysant en rozenbottel kwamen in vergelijking met Alchemilla en Delphinium minder roofmijten voor. Trips en spint waren in 2008 en 2009 geen probleem in Veronica, chrysant en rozenbottel. Op rozenbottel kwam zonder introductie Neoseiulus cucumeris voor. Andere soorten roofmijten, die soms spontaan optraden waren Neoseiulus reductus in Delphinium, Amblyseius graminis in Alchemilla en chrysant, en roofmijten die tot een andere groep (Bdelloidea) behoren, met name op chrysant en Veronica
Electrochemistry of potentially bioreductive alkylating quinones : Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents
The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the result of a change in the electron density of the quinone moiety, pre- or post-protonation of substituents, hydrogen bond formation, tautomerization reactions and steric interactions between the quinone moiety and substituents. The information obtained was of benefit in the elucidation of the reduction mechanisms of quinoid antitumour agents such as aziridnylquinones and mitomycins
Numerical study of two-body correlation in a 1D lattice with perfect blockade
We compute the dynamics of excitation and two-body correlation for two-level
"pseudoatoms" in a 1D lattice. We adopt a simplified model where pair
excitation within a finite range is perfectly blocked. Each superatom is
initially in the ground state, and then subjected to an external driving laser
with Rabi frequency satisfying a Poissonian distribution, mimicking the
scenario as in Rydberg gases. We find that two-body quantum correlation drops
very fast with the distance between pseudoatoms. However, the total correlation
decays slowly even at large distance. Our results may be useful to the
understanding of Rydberg gases in the strong blockade regime
An atom interferometer enabled by spontaneous decay
We investigate the question whether Michelson type interferometry is possible
if the role of the beam splitter is played by a spontaneous process. This
question arises from an inspection of trajectories of atoms bouncing
inelastically from an evanescent-wave (EW) mirror. Each final velocity can be
reached via two possible paths, with a {\it spontaneous} Raman transition
occurring either during the ingoing or the outgoing part of the trajectory. At
first sight, one might expect that the spontaneous character of the Raman
transfer would destroy the coherence and thus the interference. We investigated
this problem by numerically solving the Schr\"odinger equation and applying a
Monte-Carlo wave-function approach. We find interference fringes in velocity
space, even when random photon recoils are taken into account.Comment: 6 pages, 5 figures, we clarified the semiclassical interpretation of
Fig.
Cognitive deficits in childhood, adolescence and adulthood in 22q11.2 deletion syndrome and association with psychopathology
22q11.2 Deletion Syndrome (22q11.2DS) is associated with high risk of psychiatric disorders and cognitive impairment. It remains unclear to what extent key cognitive skills are associated with psychopathology, and whether cognition is stable over time in 22q11.2DS. 236 children, adolescents and adults with 22q11.2DS and 106 typically developing controls were recruited from three sites across Europe. Measures of IQ, processing speed, sustained attention, spatial working memory and psychiatric assessments were completed. Cognitive performance in individuals was calculated relative to controls in different age groups (children (6–9 years), adolescents (10–17 years), adults (18+ years)). Individuals with 22q11.2DS exhibited cognitive impairment and higher rates of psychiatric disorders compared to typically developing controls. Presence of Autism Spectrum Disorder symptoms was associated with greater deficits in processing speed, sustained attention and working memory in adolescents but not children. Attention deficit hyperactivity disorder in children and adolescents and psychotic disorder in adulthood was associated with sustained attention impairment. Processing speed and working memory were more impaired in children and adults with 22q11.2DS respectively, whereas the deficit in sustained attention was present from childhood and remained static over developmental stages. Psychopathology was associated with cognitive profile of individuals with 22q11.2DS in an age-specific and domain-specific manner. Furthermore, magnitude of cognitive impairment differed by developmental stage in 22q11.2DS and the pattern differed by domain
Clustering between high-mass X-ray binaries and OB associations in the Milky Way
We present the first direct measurement of the spatial cross-correlation
function of high-mass X-ray binaries (HMXBs) and active OB star-forming
complexes in the Milky Way. This result relied on a sample containing 79 hard
X-ray selected HMXBs and 458 OB associations. Clustering between the two
populations is detected with a significance above 7-sigmas for distances < 1
kpc. Thus, HMXBs closely trace the underlying distribution of the massive
star-forming regions that are expected to produce the progenitor stars of
HMXBs. The average offset of 0.4+-0.2 kpc between HMXBs and OB associations is
consistent with being due to natal kicks at velocities of the order of 100+-50
km/s. The characteristic scale of the correlation function suggests an average
kinematical age (since the supernova phase) of ~4 Myr for the HMXB population.
Despite being derived from a global view of our Galaxy, these signatures of
HMXB evolution are consistent with theoretical expectations as well as
observations of individual objects.Comment: 18 pages, 10 figures, 3 tables, accepted for publication in Ap
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