2,773 research outputs found
Controllability of spin-boson systems
In this paper we study the so-called spin-boson system, namely {a two-level
system} in interaction with a distinguished mode of a quantized bosonic field.
We give a brief description of the controlled Rabi and Jaynes--Cummings models
and we discuss their appearance in the mathematics and physics literature. We
then study the controllability of the Rabi model when the control is an
external field acting on the bosonic part. Applying geometric control
techniques to the Galerkin approximation and using perturbation theory to
guarantee non-resonance of the spectrum of the drift operator, we prove
approximate controllability of the system, for almost every value of the
interaction parameter
Allantoin Crystal Formation in Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) Females.
Bagrada hilaris is a polyphagous herbivore reported as an invasive pest in the United States. During the course of dissecting Burmeister hilaris unique crystals were observed in both the midgut and oviducts. Crystals were identified using X-ray diffraction techniques. Both acicular (i.e., needle-like, slender, and/or tapered) and cubic (i.e., cube shaped) crystals were observed in six of 75 individuals examined (8.0%). The crystals were mainly observed in females (6.7%), followed by males (1.3%) with no crystals observed in the minimal number of nymphs examined (0%). Crystals of both types were detected in the midgut and lateral oviducts of the females and midgut in males. The acicular crystals often appeared as distinct bundles when present in the midgut and oviducts. Crystals varied in size with the acicular crystals ranging from 0.12 mm to 0.5 mm in length although the cubic crystals ranged in length from 0.25 mm to over 1.0 mm with widths of ∼0.25 mm. The cubic crystals were identified as allantoin although the acicular crystals were most likely dl-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is curious and raises some interesting questions. More research is warranted to further understand mechanisms associated with such crystal formation in B. hilaris and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen
Integrated CO2 capture and utilization using non-thermal plasmolysis
In this work, two simple processes for carbon dioxide (CO2) such as capture and utilization have been combined to form a whole systems approach to carbon capture and utilization (CCU). The first stage utilizes a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times while employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable of capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance toward impurities in the feed, in the form of nitrogen (N2), for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%)
Note and Comment
Legislative Power to Restrict Freedom of Labor Contracts -The struggle between the police power of the legislature and the nineteenth century idea of due process of law continues unremittingly. That increasing social necessities and a more comprehensive and perfect conception of justice have resulted in recent years in restricting the due process clauses in federal and state constitutions to their historically and logically more correct meaning and scope there can be no doubt. Scores, if not hundreds, of decisions by our courts and conspicuously those of the United States Supreme Court have shown complete recognition of the fact that the formalism and the extreme individualism of earlier periods can only produce dangerous economic and social maladjustments in the complex and interlocking organization of our modern society
Functional evolution of quantum cylindrical waves
Kucha{\v{r}} showed that the quantum dynamics of (1 polarization) cylindrical
wave solutions to vacuum general relativity is determined by that of a free
axially-symmetric scalar field along arbitrary axially-symmetric foliations of
a fixed flat 2+1 dimensional spacetime. We investigate if such a dynamics can
be defined {\em unitarily} within the standard Fock space quantization of the
scalar field.
Evolution between two arbitrary slices of an arbitrary foliation of the flat
spacetime can be built out of a restricted class of evolutions (and their
inverses). The restricted evolution is from an initial flat slice to an
arbitrary (in general, curved) slice of the flat spacetime and can be
decomposed into (i) `time' evolution in which the spatial Minkowskian
coordinates serve as spatial coordinates on the initial and the final slice,
followed by (ii) the action of a spatial diffeomorphism of the final slice on
the data obtained from (i). We show that although the functional evolution of
(i) is unitarily implemented in the quantum theory, generic spatial
diffeomorphisms of (ii) are not. Our results imply that a Tomanaga-Schwinger
type functional evolution of quantum cylindrical waves is not a viable concept
even though, remarkably, the more limited notion of functional evolution in
Kucha{\v{r}}'s `half parametrized formalism' is well-defined.Comment: Replaced with published versio
Evolutionary history of mammalian sucking lice (Phthiraptera: Anoplura)
<p>Abstract</p> <p>Background</p> <p>Sucking lice (Phthiraptera: Anoplura) are obligate, permanent ectoparasites of eutherian mammals, parasitizing members of 12 of the 29 recognized mammalian orders and approximately 20% of all mammalian species. These host specific, blood-sucking insects are morphologically adapted for life on mammals: they are wingless, dorso-ventrally flattened, possess tibio-tarsal claws for clinging to host hair, and have piercing mouthparts for feeding. Although there are more than 540 described species of Anoplura and despite the potential economical and medical implications of sucking louse infestations, this study represents the first attempt to examine higher-level anopluran relationships using molecular data. In this study, we use molecular data to reconstruct the evolutionary history of 65 sucking louse taxa with phylogenetic analyses and compare the results to findings based on morphological data. We also estimate divergence times among anopluran taxa and compare our results to host (mammal) relationships.</p> <p>Results</p> <p>This study represents the first phylogenetic hypothesis of sucking louse relationships using molecular data and we find significant conflict between phylogenies constructed using molecular and morphological data. We also find that multiple families and genera of sucking lice are not monophyletic and that extensive taxonomic revision will be necessary for this group. Based on our divergence dating analyses, sucking lice diversified in the late Cretaceous, approximately 77 Ma, and soon after the Cretaceous-Paleogene boundary (ca. 65 Ma) these lice proliferated rapidly to parasitize multiple mammalian orders and families.</p> <p>Conclusions</p> <p>The diversification time of sucking lice approximately 77 Ma is in agreement with mammalian evolutionary history: all modern mammal orders are hypothesized to have diverged by 75 Ma thus providing suitable habitat for the colonization and radiation of sucking lice. Despite the concordant timing of diversification events early in the association between anoplurans and mammals, there is substantial conflict between the host and parasite phylogenies. This conflict is likely the result of a complex history of host switching and extinction events that occurred throughout the evolutionary association between sucking lice and their mammalian hosts. It is unlikely that there are any ectoparasite groups (including lice) that tracked the early and rapid radiation of eutherian mammals.</p
First Kepler results on compact pulsators VIII: Mode identifications via period spacings in mode pulsating Subdwarf B stars
We investigate the possibility of nearly-equally spaced periods in 13 hot
subdwarf B (sdB) stars observed with the Kepler spacecraft and one observed
with CoRoT. Asymptotic limits for gravity (g-)mode pulsations provide
relationships between equal period spacings of modes with differing degrees and
relationships between periods of the same radial order but differing degrees.
Period transforms, Kolmogorov-Smirnov tests, and linear least-squares fits have
been used to detect and determine the significance of equal period spacings. We
have also used Monte Carlo simulations to estimate the likelihood that the
detected spacings could be produced randomly.
Period transforms for nine of the Kepler stars indicate ell=1 period
spacings, with five also showing peaks for ell=2 modes. 12 stars indicate ell=1
modes using the Kolmogorov-Smirnov test while another shows solely ell=2 modes.
Monte Carlo results indicate that equal period spacings are significant in 10
stars above 99% confidence and 13 of the 14 are above 94% confidence. For 12
stars, the various methods find consistent regular period spacing values to
within the errors, two others show some inconsistencies, likely caused by
binarity, and the last has significant detections but the mode assignment
disagrees between methods.
We find a common ell=1 period spacing spanning a range from 231 to 272 s
allowing us to correlate pulsation modes with 222 periodicities and that the
ell=2 period spacings are related to the ell=1 spacings by the asymptotic
relationship . We briefly discuss the impact of equal period
spacings which indicate low-degree modes with a lack of significant mode
trappings.Comment: 27 pages, 4 figures, 17 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Societ
The ground state of a general electron-phonon Hamiltonian is a spin singlet
The many-body ground state of a very general class of electron-phonon
Hamiltonians is proven to contain a spin singlet (for an even number of
electrons on a finite lattice). The phonons interact with the electronic system
in two different ways---there is an interaction with the local electronic
charge and there is a functional dependence of the electronic hopping
Hamiltonian on the phonon coordinates. The phonon potential energy may include
anharmonic terms, and the electron-phonon couplings and the hopping matrix
elements may be nonlinear functions of the phonon coordinates. If the hopping
Hamiltonian is assumed to have no phonon coordinate dependence, then the ground
state is also shown to be unique, implying that there are no ground-state level
crossings, and that the ground-state energy is an analytic function of the
parameters in the Hamiltonian. In particular, in a finite system any
self-trapping transition is a smooth crossover not accompanied by a
nonanalytical change in the ground state. The spin-singlet theorem applies to
the Su-Schrieffer-Heeger model and both the spin-singlet and uniqueness
theorems apply to the Holstein and attractive Hubbard models as special cases.
These results hold in all dimensions --- even on a general graph without
periodic lattice structure.Comment: 25 pages, no figures, plainte
On Petition for a Writ of Certiorari to The United States Court of Appeals for The Eighth Circuit, Brief of Law Professors Paul F. Rothstein, et. al., Office of the President v. Office of Independent Counsel
This Court should grant review not only because this is a case of national importance and prominence, but also because the decision below is a conspicuous departure from settled principles of evidence law. The panel majority concluded that communications between government lawyers and government officials are not protected by the attorney-client privilege, at least when those communications are sought by a federal grand jury. That conclusion conflicts with the predominant common-law understanding that the attorney-client privilege applies to government entities and that where the privilege applies, it is absolute (i.e., it protects against disclosure in all types of legal and investigative proceedings). In particular, the Court of Appeals\u27 decision rests on a fundamental misunderstanding of this Court\u27s decisions in Upjohn Co. v. United States, 449 U.S. 383 (1981), and United States v. Nixon, 418 U.s. 683 (1974).
Moreover, this case warrants further review because the decision below has profound implications beyond the parties to this dispute. The Court of Appeals\u27 ruling, if allowed to stand, will create widespread uncertainty among federal, state, and local officials concerning the extent to which their communications with their agency lawyers, for the purpose of seeking legal advice in the conduct of governmental affairs, are protected by the attorney-client privilege. Unless this Court grants review and resolves this uncertainty, the decision below will likely have an adverse effect on the current and future operation of not only the Office of the President of the United States, but also government at all levels. At the very least, a decision of such vast implications (as in the present case) should be made by the highest court in the land. We accordingly urge the Court to grant the petition for review
Phase Space Reduction and Vortex Statistics: An Anyon Quantization Ambiguity
We examine the quantization of the motion of two charged vortices in a
Ginzburg--Landau theory for the fractional quantum Hall effect recently
proposed by the first two authors. The system has two second-class constraints
which can be implemented either in the reduced phase space or
Dirac-Gupta-Bleuler formalism. Using the intrinsic formulation of statistics,
we show that these two ways of implementing the constraints are inequivalent
unless the vortices are quantized with conventional statistics; either
fermionic or bosonic.Comment: 14 pages, PHYZZ
- …