3,973 research outputs found
Charge regulation and ionic screening of patchy surfaces
The properties of surfaces with charge-regulated patches are studied using
non-linear Poisson-Boltzmann theory. Using a mode expansion to solve the
non-linear problem efficiently, we reveal the charging behaviour of
Debye-length sized patches. We find that patches charge up to higher charge
densities if their size is relatively small and if the patches are well
separated. The numerical results are used to construct a basic analytical model
which predicts the average surface charge density on surfaces with patchy
chargeable groups.Comment: 9 figure
Screening of heterogeneous surfaces: charge renormalization of Janus particles
Nonlinear ionic screening theory for heterogeneously charged spheres is
developed in terms of a mode-decomposition of the surface charge. A far-field
analysis of the resulting electrostatic potential leads to a natural
generalization of charge renormalization from purely monopolar to dipolar,
quadropolar, etc., including mode-couplings. Our novel scheme is generally
applicable to large classes of surface heterogeneities, and is explicitly
applied here to Janus spheres with differently charged upper and lower
hemispheres, revealing strong renormalization effects for all multipoles.Comment: 2 figure
Auf deutsch, bitte!:Target language use among in-service teachers of German.
The present study investigates the use of German by teachers in GFL (German as a foreign language) classrooms in Dutch secondary education. It explores to what extent and in which classroom situations German is used, and whether a discrepancy exists between desired and actual use. Furthermore, this study aims to clarify what factors affect Target Language (TL) use including both hindering and fostering factors. In addition, we determine the impact of individual factors and discuss to what extent the curricular and linguistic situation of German in the Netherlands affects TL use. The results are based on a quantitative analysis of a questionnaire regarding their TL use, which was filled in by 32 GFL teachers. These teachers indicate that they speak German mainly when they give positive feedback, standard instructions, and general and individual orders or warnings, when they help during individual work, and when they discuss reading and listening texts. The complexity of the lesson content, students’ reactions to TL use, and the teachers’ own language proficiency are indicated as most important when deciding whether or not to use the TL. Desired and perceived TL use differ marginally
Suitable Strategies for In-plane Orbit Acquisition using Micro-thrusters
The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be corrected through a set of acquisition maneuvers to achieve the desired nominal parameters. When multiple satellites are injected into a single orbital plane, as a part of constellation establishment, they have to positioned in the plane with appropriate semi-major axis ‘a’ and mean anomaly ‘M’. In this paper, three strategies are studied for achieving orbit acquisition. The first strategy is by deriving an analogy to the Linear Quadratic Regulator (LQR). The state dynamics and the control law are of the form X&= AX + BU and U = −KX . The feedback gain K is calculated by minimizing the cost function. Under this strategy the thrust (N) and velocity increment ( ÄV ) are functions of time and only the matrix K needs to be up-linked. Any revision in the current or the target states, will then lead to a simple re-calculation of K and up-linking them. The second strategy assumes that ÄV is same for each maneuver and calculates the number of maneuvers and the ÄV required for each maneuver. If the maneuvers are stopped for reasons like orbit assessment, and thruster performance evaluation, the strategy can be restarted easily without having any penalty on the overall ÄV. Besides these two strategies, a third strategy based on the application of Fuzzy Modified Potential Function is also studied for autonomous orbit acquisition with constraints in the path. By adding Fuzzy logic to the potential function it is shown that, maneuvers can be changed gradually ahead of the constraints. Onboard implementation related aspects are also briefly addressed for all the strategies
Association Between Smoking and Tuberculosis Infection: A Population Survey in a High Tuberculosis Incidence Area
Associations between smoking and tuberculosis disease including death from tuberculosis have been reported, but there are few reports on the influence of smoking on the risk of developing Mycobacterium tuberculosis infection. The aim of this study was to determine the association between smoking and M tuberculosis infection. In a cross sectional population survey, data on smoking and tuberculin skin test (TST) results of 2401 adults aged >15 years were compared. A total of 1832 (76%) subjects had a positive TST (>10 mm induration). Of 1309 current smokers or ex-smokers, 1070 (82%) had a positive TST. This was significantly higher than for never smokers (unadjusted OR 1.99, 95% confidence interval (CI) 1.62 to 2.45). A positive relationship with pack-years was observed, with those smoking more than 15 pack-years having the highest risk (adjusted OR 1.90,95% CI 1.28 to 2.81). Smoking may increase the risk of M tuberculosis infection.\u
Visible and Ultraviolet Laser Spectroscopy of ThF
The molecular ion ThF is the species to be used in the next generation of
search for the electron's Electric Dipole Moment (eEDM) at JILA. The
measurement requires creating molecular ions in the eEDM sensitive state, the
rovibronic ground state , , . Survey spectroscopy of
neutral ThF is required to identify an appropriate intermediate state for a
Resonance Enhanced Multi-Photon Ionization (REMPI) scheme that will create ions
in the required state. We perform broadband survey spectroscopy (from 13000 to
44000~cm) of ThF using both Laser Induced Fluorescence (LIF) and
REMPI spectroscopy. We observe and assign 345 previously unreported vibronic
bands of ThF. We demonstrate 30\% efficiency in the production of ThF ions
in the eEDM sensitive state using the [32.85] intermediate
state. In addition, we propose a method to increase the aforementioned
efficiency to 100\% by using vibrational autoionization via
core-nonpenetrating Rydberg states, and discuss theoretical and experimental
challenges. Finally, we also report 83 vibronic bands of an impurity species,
ThO.Comment: 49 pages, 7 figure
Dynamics of short polymer chains in solution
We present numerical and analytical results describing the effect of
hydrodynamic interactions on the dynamics of a short polymer chain in solution.
A molecular dynamics algorithm for the polymer is coupled to a direct
simulation Monte Carlo algorithm for the solvent. We give an explicit
expression for the velocity autocorrelation function of the centre of mass of
the polymer which agrees well with numerical results if Brownian dynamics,
hydrodynamic correlations and sound wave scattering are included
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