1,687 research outputs found
Trapping of Rb atoms by ac electric fields
We demonstrate trapping of an ultracold gas of neutral atoms in a macroscopic
ac electric trap. Three-dimensional confinement is obtained by switching
between two saddle-point configurations of the electric field. Stable trapping
is observed in a narrow range of switching frequencies around 60 Hz. The
dynamic confinement of the atoms is directly visualized at different phases of
the ac switching cycle. We observe about 10^5 Rb atoms in the 1 mm^3 large and
several microkelvins deep trap with a lifetime of approximately 5 s.Comment: 4 pages, 4 figures; updated version, added journal referenc
Multiple packets of neutral molecules revolving for over a mile
The level of control that one has over neutral molecules in beams dictates
their possible applications. Here we experimentally demonstrate that
state-selected, neutral molecules can be kept together in a few mm long packet
for a distance of over one mile. This is accomplished in a circular arrangement
of 40 straight electrostatic hexapoles through which the molecules propagate
over 1000 times. Up to 19 packets of molecules have simultaneously been stored
in this ring structure. This brings the realization of a molecular low-energy
collider within reach
Polyline Drawings with Topological Constraints
Let G be a simple topological graph and let Gamma be a polyline drawing of G. We say that Gamma partially preserves the topology of G if it has the same external boundary, the same rotation system, and the same set of crossings as G. Drawing Gamma fully preserves the topology of G if the planarization of G and the planarization of Gamma have the same planar embedding. We show that if the set of crossing-free edges of G forms a connected spanning subgraph, then G admits a polyline drawing that partially preserves its topology and that has curve complexity at most three (i.e., at most three bends per edge). If, however, the set of crossing-free edges of G is not a connected spanning subgraph, the curve complexity may be Omega(sqrt{n}). Concerning drawings that fully preserve the topology, we show that if G has skewness k, it admits one such drawing with curve complexity at most 2k; for skewness-1 graphs, the curve complexity can be reduced to one, which is a tight bound. We also consider optimal 2-plane graphs and discuss trade-offs between curve complexity and crossing angle resolution of drawings that fully preserve the topology
Spontaneous emission of atomic systems in the presence of incident fields
We characterise the spontaneous emission time and direction from small
numbers of dipole-coupled two-level atoms (2LAs) in the presence of incident
fields. We show how to use adiabatic passage to admit population transfer
between states in the one-quantum subspace for two and three 2LAs. Our method
is a multi-atom generalisation of stimulated-Raman-adiabatic-passage (STIRAP)
for a single multi-level atom. We use numerical results to justify an ansatz
that enables us to give analytical expressions for the directional emission
which depends on the incident fields. Our results admit a characterisation of
the efficacy of population transfer in small numbers of dipole-coupled 2LAs,
and are applicable to proof-of-principle experiments involving dipole-coupled
2LAs.Comment: 10 pages, 6 figure
Mixed-Effects Trait-State-Occasion Model:Studying the Psychometric Properties and the Person–Situation Interactions of Psychological Dynamics
The trait-state-occasion model (TSO) is a popular model within the latent state-trait theory (LST). The TSO allows distinguishing the trait and the state components of the psychological constructs measured in longitudinal data, while also taking into account the carry-over effects between consecutive measurements. In the present study, we extend a multilevel version of the TSO model to allow for the combination of fixed and random situations, namely the mixed-effects TSO (ME-TSO). Hence, the ME-TSO model is a measurement model suitable to analyze intensive longitudinal data that allows studying the psychometric properties of the indicators per individual, the heterogeneity of psychological dynamics, and the person–situation interaction effects. We showcase how to use the model by analyzing the items of positive affect activation of the crowdsourcing study HowNutsAreTheDutch (HoeGekisNL)
Electrostatic trapping of metastable NH molecules
We report on the Stark deceleration and electrostatic trapping of NH
() radicals. In the trap, the molecules are excited on the
spin-forbidden transition and detected via
their subsequent fluorescence to the ground state. The 1/e
trapping time is 1.4 0.1 s, from which a lower limit of 2.7 s for the
radiative lifetime of the state is deduced. The spectral
profile of the molecules in the trapping field is measured to probe their
spatial distribution. Electrostatic trapping of metastable NH followed by
optical pumping of the trapped molecules to the electronic ground state is an
important step towards accumulation of these radicals in a magnetic trap.Comment: replaced with final version, added journal referenc
Anisotropic intrinsic lattice thermal conductivity of phosphorene from first principles
Phosphorene, the single layer counterpart of black phosphorus, is a novel
two-dimensional semiconductor with high carrier mobility and a large
fundamental direct band gap, which has attracted tremendous interest recently.
Its potential applications in nano-electronics and thermoelectrics call for a
fundamental study of the phonon transport. Here, we calculate the intrinsic
lattice thermal conductivity of phosphorene by solving the phonon Boltzmann
transport equation (BTE) based on first-principles calculations. The thermal
conductivity of phosphorene at is
(zigzag) and
(armchair), showing an obvious anisotropy along different directions. The
calculated thermal conductivity fits perfectly to the inverse relation with
temperature when the temperature is higher than Debye temperature (). In comparison to graphene, the minor contribution around
of the ZA mode is responsible for the low thermal conductivity of
phosphorene. In addition, the representative mean free path (MFP), a critical
size for phonon transport, is also obtained.Comment: 5 pages and 6 figures, Supplemental Material available as
http://www.rsc.org/suppdata/cp/c4/c4cp04858j/c4cp04858j1.pd
Reconciling contradictions of open data regarding transparency, privacy, security and trust.
Abstract While Open Data initiatives are diverse, they aim to create and contribute to public value. Yet several potential contradictions exist between public values, such as trust, transparency, privacy, and security, and Open Data policies. To bridge these contradictions, we present the notion of precommitment as a restriction of one's choices. Conceptualized as a policy instrument, precommitment can be applied by an organization to restrict the extent to which an Open Data policy might conflict with public values. To illustrate the use of precommitment, we present two case studies at two public sector organizations, where precommitment is applied during a data request procedure to reconcile conflicting values. In this procedure, precommitment is operationalized in three phases. In the first phase, restrictions are defined on the type and the content of the data that might be requested. The second phase involves the preparation of the data to be delivered according to legal requirements and the decisions taken in phase 1. Data preparation includes amongst others the deletion of privacy sensitive or other problematic attributes. Finally, phase 3 pertains to the establishment of the conditions of reuse of the data, limiting the use to restricted user groups or opening the data for everyone
The SURgical PAtient Safety System (SURPASS) checklist optimizes timing of antibiotic prophylaxis
Background: Surgical site infection (SSI) is an adverse event in which a close relation between process of care and outcome has been demonstrated: administration of antibiotic prophylaxis decreases the risk of SSI. In our tertiary referral centre, a SURgical PAtient Safety System (SURPASS) checklist was developed and implemented. This multidisciplinary checklist covers the entire surgical pathway and includes, among other items, administration of antibiotic prophylaxis before induction of anaesthesia. The aim of this study was to determine the effect of SURPASS implementation on timing of antibiotic prophylaxis. Methods: A retrospective analysis was performed on two cohorts of patients: one cohort of surgical patients that underwent surgery before implementation of the checklist and a comparable cohort after implementation. The interval between administration of antibiotic prophylaxis and incision was compared between the two cohorts. Results: A total of 772 surgical procedures were included. More than half of procedures were gastro-intestinal; others were vascular, trauma and hernia repair procedures. After implementation, the checklist was used in 81.4 % of procedures. The interval between administration of antibiotic prophylaxis and incision increased from 23.9 minutes before implementation of SURPASS to 29.9 minutes after implementation (p = 0.047). In procedures where the checklist was used, the interval increased to 32.9 minutes (p = 0.004). The proportion of patients that did not receive antibiotics until after the incision decreased significantly. Conclusion: The use of the SURPASS checklist leads to better compliance with regard to the timing of antibiotic prophylaxis administration
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