17,117 research outputs found
Wave packet dynamics of potassium dimers attached to helium nanodroplets
The dynamics of vibrational wave packets excited in K dimers attached to
superfluid helium nanodroplets is investigated by means of femtosecond
pump-probe spectroscopy. The employed resonant three-photon-ionization scheme
is studied in a wide wavelength range and different pathways leading to
K-formation are identified. While the wave packet dynamics of the
electronic ground state is not influenced by the helium environment,
perturbations of the electronically excited states are observed. The latter
reveal a strong time dependence on the timescale 3-8 ps which directly reflects
the dynamics of desorption of K off the helium droplets
Evaluation of enzyme immunoassays in the diagnosis of camel (Camelus dromedarius) trypanosomiasis:a preliminary investigation
Three enzyme immunoassays were used for the serodiagnosis of Trypanosoma evansi in camels in the Sudan in order to evaluate their ability to discriminate between infected and non-infected animals. Two assays were used for the detection of trypanosomal antibodies, one using specific anti-camel IgG conjugate and another using a non-specific Protein A conjugate. The third assay detected the presence of trypanosomal antigens using anti-T. evansi antibodies in a double antibody sandwich assay. Inspection of the frequency distribution of assay results suggested that the ELISA for circulating trypanosomal antibodies using specific antisera and the ELISA for circulating antigens can distinguish between non-infected camels and infected camels exhibiting patent infections or not. The ELISA using Protein A conjugate to bind non-specifically to camel immunoglobulin did not appear to discriminate between infected and non-infected animals
Slow plasmon modes in polymeric salt solutions
The dynamics of polymeric salt solutions are presented. The salt consists of
chains and , which are chemically different and interact with a
Flory-interaction parameter , the chain ends carry a positive
charge whereas the chain ends are modified by negative charges. The
static structure factor shows a peak corresponding to a micro phase separation.
At low momentum transfer, the interdiffusion mode is driven by electrostatics
and is of the plasmon-type, but with an unusually low frequency, easily
accessible by experiments. This is due to the polymer connectivity that
introduces high friction and amplifies the charge scattering thus allowing for
low charge densities. The interdiffusion mode shows a minimum (critical slowing
down) at finite when the interaction parameter increases we find then a low
frequency quasi-plateau.Comment: accepted in Europhys. Let
Scaling of Berry's Phase Close to the Dicke Quantum Phase Transition
We discuss the thermodynamic and finite size scaling properties of the
geometric phase in the adiabatic Dicke model, describing the super-radiant
phase transition for an qubit register coupled to a slow oscillator mode.
We show that, in the thermodynamic limit, a non zero Berry phase is obtained
only if a path in parameter space is followed that encircles the critical
point. Furthermore, we investigate the precursors of this critical behavior for
a system with finite size and obtain the leading order in the 1/N expansion of
the Berry phase and its critical exponent
Analytical Rebridging Monte Carlo: Application to cis/trans Isomerization in Proline-Containing, Cyclic Peptides
We present a new method, the analytical rebridging scheme, for Monte Carlo
simulation of proline-containing, cyclic peptides. The cis/trans isomerization
is accommodated by allowing for two states of the amide bond. We apply our
method to five peptides that have been previously characterized by NMR methods.
Our simulations achieve effective equilibration and agree well with
experimental data in all cases. We discuss the importance of effective
equilibration and the role of bond flexibility and solvent effects on the
predicted equilibrium properties.Comment: 29 pages, 8 PostScript figures, LaTeX source. to appear in J. Chem.
Phys., 199
Steep sharp-crested gravity waves on deep water
A new type of steady steep two-dimensional irrotational symmetric periodic
gravity waves on inviscid incompressible fluid of infinite depth is revealed.
We demonstrate that these waves have sharper crests in comparison with the
Stokes waves of the same wavelength and steepness. The speed of a fluid
particle at the crest of new waves is greater than their phase speed.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Effects of rotation on coolant passage heat transfer. Volume 1: Coolant passages with smooth walls
An experimental program was conducted to investigate heat transfer and pressure loss characteristics of rotating multipass passages, for configurations and dimensions typical of modern turbine blades. The immediate objective was the generation of a data base of heat transfer and pressure loss data required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. Experiments were conducted in a smooth wall large scale heat transfer model
A Formalism for Scattering of Complex Composite Structures. 1 Applications to Branched Structures of Asymmetric Sub-Units
We present a formalism for the scattering of an arbitrary linear or acyclic
branched structure build by joining mutually non-interacting arbitrary
functional sub-units. The formalism consists of three equations expressing the
structural scattering in terms of three equations expressing the sub-unit
scattering. The structural scattering expressions allows a composite structures
to be used as sub-units within the formalism itself. This allows the scattering
expressions for complex hierarchical structures to be derived with great ease.
The formalism is furthermore generic in the sense that the scattering due to
structural connectivity is completely decoupled from internal structure of the
sub-units. This allows sub-units to be replaced by more complex structures. We
illustrate the physical interpretation of the formalism diagrammatically. By
applying a self-consistency requirement we derive the pair distributions of an
ideal flexible polymer sub-unit. We illustrate the formalism by deriving
generic scattering expressions for branched structures such as stars, pom-poms,
bottle-brushes, and dendrimers build out of asymmetric two-functional
sub-units.Comment: Complete rewrite generalizing the formalism to arbitrary functional
sub-units and including a new Feynmann like diagrammatic interpretatio
A Formalism for Scattering of Complex Composite Structures. 2 Distributed Reference Points
Recently we developed a formalism for the scattering from linear and acyclic
branched structures build of mutually non-interacting sub-units.{[}C. Svaneborg
and J. S. Pedersen, J. Chem. Phys. 136, 104105 (2012){]} We assumed each
sub-unit has reference points associated with it. These are well defined
positions where sub-units can be linked together. In the present paper, we
generalize the formalism to the case where each reference point can represent a
distribution of potential link positions. We also present a generalized
diagrammatic representation of the formalism. Scattering expressions required
to model rods, polymers, loops, flat circular disks, rigid spheres and
cylinders are derived. and we use them to illustrate the formalism by deriving
the generic scattering expression for micelles and bottle brush structures and
show how the scattering is affected by different choices of potential link
positions.Comment: Paper no. 2 of a serie
Grain Drill Calibration Procedures for Winter Wheat
Intensive wheat management requires attention to details, from planting through harvest. Perhaps most critical is stand establishment. While no-tilling wheat into corn stubble presents a range of problems in depth control and residue management, these problems do not minimize the importance of calibration.
Just as no two drills are manufactured alike, seed rarely is produced in uniform size, nor do individual metering cups deliver the same seed quantities. A few hours of attention to calibration at the start of fall planting will help producers control seed costs and achieve more desirable, uniform stands and better yields
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