156 research outputs found
The three-body problem and the Hannay angle
The Hannay angle has been previously studied for a celestial circular
restricted three-body system by means of an adiabatic approach. In the present
work, three main results are obtained. Firstly, a formal connection between
perturbation theory and the Hamiltonian adiabatic approach shows that both lead
to the Hannay angle; it is thus emphasised that this effect is already
contained in classical celestial mechanics, although not yet defined nor
evaluated separately. Secondly, a more general expression of the Hannay angle,
valid for an action-dependent potential is given; such a generalised expression
takes into account that the restricted three-body problem is a time-dependent,
two degrees of freedom problem even when restricted to the circular motion of
the test body. Consequently, (some of) the eccentricity terms cannot be
neglected {\it a priori}. Thirdly, we present a new numerical estimate for the
Earth adiabatically driven by Jupiter. We also point out errors in a previous
derivation of the Hannay angle for the circular restricted three-body problem,
with an action-independent potential.Comment: 11 pages. Accepted by Nonlinearit
Geometric phases and anholonomy for a class of chaotic classical systems
Berry's phase may be viewed as arising from the parallel transport of a
quantal state around a loop in parameter space. In this Letter, the classical
limit of this transport is obtained for a particular class of chaotic systems.
It is shown that this ``classical parallel transport'' is anholonomic ---
transport around a closed curve in parameter space does not bring a point in
phase space back to itself --- and is intimately related to the Robbins-Berry
classical two-form.Comment: Revtex, 11 pages, no figures
Natural incidence of egg parasitoids of <i>Edessa meditabunda</i> (F.) (Hemiptera: pentatomidae) on <i>Crotalaria spectabilis</i> in Campo Novo do Parecis, MT, Brazil
Egg parasitoids of the stink bug Edessa meditabunda (F) were studied on rattlepod Crotalaria spectabilis used in soybean crop rotation in Campo Novo do Parecis, Mato Grosso state, central western Brazil. Seven species of parasitoids were found: two Encyrtidae, one Eurytomidae, and four Platygastridae. The occurrence of Trissolcus euchisti (Ashmead) and Trissolcus elimatus Johnson (Platygastridae) on eggs of E. meditabunda is recorded for the first time. Moreover, this is the first record of T. elimatus and T. euchisti from Brazil.Facultad de Ciencias Naturales y Muse
Natural incidence of egg parasitoids of <i>Edessa meditabunda</i> (F.) (Hemiptera: pentatomidae) on <i>Crotalaria spectabilis</i> in Campo Novo do Parecis, MT, Brazil
Egg parasitoids of the stink bug Edessa meditabunda (F) were studied on rattlepod Crotalaria spectabilis used in soybean crop rotation in Campo Novo do Parecis, Mato Grosso state, central western Brazil. Seven species of parasitoids were found: two Encyrtidae, one Eurytomidae, and four Platygastridae. The occurrence of Trissolcus euchisti (Ashmead) and Trissolcus elimatus Johnson (Platygastridae) on eggs of E. meditabunda is recorded for the first time. Moreover, this is the first record of T. elimatus and T. euchisti from Brazil.Facultad de Ciencias Naturales y Muse
An Adiabatic Theorem without a Gap Condition
The basic adiabatic theorems of classical and quantum mechanics are
over-viewed and an adiabatic theorem in quantum mechanics without a gap
condition is described.Comment: Talk at QMath 7, Prague, 1998. 10 pages, 7 figure
Natural incidence of egg parasitoids of <i>Edessa meditabunda</i> (F.) (Hemiptera: pentatomidae) on <i>Crotalaria spectabilis</i> in Campo Novo do Parecis, MT, Brazil
Egg parasitoids of the stink bug Edessa meditabunda (F) were studied on rattlepod Crotalaria spectabilis used in soybean crop rotation in Campo Novo do Parecis, Mato Grosso state, central western Brazil. Seven species of parasitoids were found: two Encyrtidae, one Eurytomidae, and four Platygastridae. The occurrence of Trissolcus euchisti (Ashmead) and Trissolcus elimatus Johnson (Platygastridae) on eggs of E. meditabunda is recorded for the first time. Moreover, this is the first record of T. elimatus and T. euchisti from Brazil.Facultad de Ciencias Naturales y Muse
The case for prioritizing implementation strategy fidelity measurement: Benefits and challenges
Implementation strategies are systematic approaches to improve the uptake and sustainability of evidence-based interventions. They frequently focus on changing provider behavior through the provision of interventions such as training, coaching, and audit-and-feedback. Implementation strategies often impact intermediate behavioral outcomes like provider guideline adherence, in turn improving patient outcomes. Fidelity of implementation strategy delivery is defined as the extent to which an implementation strategy is carried out as it was designed. Implementation strategy fidelity measurement is under-developed and under-reported, with the quality of reporting decreasing over time. Benefits of fidelity measurement include the exploration of the extent to which observed effects are moderated by fidelity, and critical information about Type-III research errors, or the likelihood that null findings result from implementation strategy fidelity failure. Reviews of implementation strategy efficacy often report wide variation across studies, commonly calling for increased implementation strategy fidelity measurement to help explain variations. Despite the methodological benefits of rigorous fidelity measurement, implementation researchers face multi-level challenges and complexities. Challenges include the measurement of a complex variable, multiple data collection modalities with varying precision and costs, and the need for fidelity measurement to change in-step with adaptations. In this position paper, we weigh these costs and benefits and ultimately contend that implementation strategy fidelity measurement and reporting should be improved in trials of implementation strategies. We offer pragmatic solutions for researchers to make immediate improvements like the use of mixed methods or innovative data collection and analysis techniques, the inclusion of implementation strategy fidelity assessment in reporting guidelines, and the staged development of fidelity tools across the evolution of an implementation strategy. We also call for additional research into the barriers and facilitators of implementation strategy fidelity measurement to further clarify the best path forward
Prediction of Anisotropic Single-Dirac-Cones in BiSb Thin Films
The electronic band structures of BiSb thin films can be
varied as a function of temperature, pressure, stoichiometry, film thickness
and growth orientation. We here show how different anisotropic
single-Dirac-cones can be constructed in a BiSb thin film for
different applications or research purposes. For predicting anisotropic
single-Dirac-cones, we have developed an iterative-two-dimensional-two-band
model to get a consistent inverse-effective-mass-tensor and band-gap, which can
be used in a general two-dimensional system that has a non-parabolic dispersion
relation as in a BiSb thin film system
Quantum Conductance in Semimetallic Bismuth Nanocontacts
Electronic transport properties of bismuth nanocontacts are analyzed by means
of a low temperature scanning tunneling microscope. The subquantum steps
observed in the conductance versus elongation curves give evidence of atomic
rearrangements in the contact. The underlying quantum nature of the conductance
reveals itself through peaks in the conductance histograms. The shape of the
conductance curves at 77 K is well described by a simple gliding mechanism for
the contact evolution during elongation. The strikingly different behaviour at
4 K suggests a charge carrier transition from light to heavy ones as the
contact cross section becomes sufficiently small.Comment: 5 pages including 4 figures. Accepted for publication in Phys. Rev.
Let
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