110 research outputs found
Electron Trapping in a One-Dimensional Semiconductor Quantum Wire with Multiple Impurities
We demonstrate the trapping of a conduction electron between two identical adatom impurities in a one-dimensional semiconductor quantum-dot array system (quantum wire). Bound steady states arise even when the energy of the adatom impurity is located in the continuous one-dimensional energy miniband. The steady state is a realization of the bound state in continuum (BIC) phenomenon first proposed by von Neuman and Wigner [Phys. Z. 30, 465 (1929)]. We analytically solve the dispersion equation for this localized state, which enables us to reveal the mechanism of the BIC. The appearance of the BIC state is attributed to the quantum interference between the impurities. The Van Hove singularity causes another type of bound state to form above and below the band edges, which may coexist with the BIC
Archeological Investigations in the Upper Trinity River Basin in Parker County, Texas
Homer Norris (1929-2018), a commercial artist by profession and a life-time resident of eastern Parker County, in North-Central Texas, in the South Fork and Clear Fork drainages of the upper Trinity River basin, roamed the landscape from at least 30-50 years ago in search of archeological evidence of Native American use and settlement in the basin. He took and maintained detailed notes, records, and drawings of the sites he found and the artifacts he recovered, as well as pertinent information on the context of finds, including those noted eroding out of stream cut banks and in stream beds of the South Fork and Clear Fork in the Anetta-Aledo areas of Parker County, about 15 miles west of Fort Worth, an area of about 5 miles on a side. This information, made available by his daughter Lanie Garmon of Aledo, Texas, from his archeological investigations is detailed herein, along with a summary of how his investigations contribute to a fuller understanding of the native history of this region of Texas
Complex Energy Spectrum and Time Evolution of QBIC States in a Two-Channel Quantum wire with an Adatom Impurity
We provide detailed analysis of the complex energy eigenvalue spectrum for a
two-channel quantum wire with an attached adatom impurity. The study is based
on our previous work [Phys. Rev. Lett. 99, 210404 (2007)], in which we
presented the quasi-bound states in continuum (or QBIC states). These are
resonant states with very long lifetimes that form as a result of two
overlapping continuous energy bands one of which, at least, has a divergent van
Hove singularity at the band edge. We provide analysis of the full energy
spectrum for all solutions, including the QBIC states, and obtain an expansion
for the complex eigenvalue of the QBIC state. We show that it has a small decay
rate of the order , where is the coupling constant. As a result of
this expansion, we find that this state is a non-analytic effect resulting from
the van Hove singularity; it cannot be predicted from the ordinary perturbation
analysis that relies on Fermi's golden rule. We will also numerically
demonstrate the time evolution of the QBIC state using the effective potential
method in order to show the stability of the QBIC wave function in comparison
with that of the other eigenstates.Comment: Around 20 pages, 50 total figure
Analysis technique for exceptional points in open quantum systems and QPT analogy for the appearance of irreversibility
We propose an analysis technique for the exceptional points (EPs) occurring
in the discrete spectrum of open quantum systems (OQS), using a semi-infinite
chain coupled to an endpoint impurity as a prototype. We outline our method to
locate the EPs in OQS, further obtaining an eigenvalue expansion in the
vicinity of the EPs that gives rise to characteristic exponents. We also report
the precise number of EPs occurring in an OQS with a continuum described by a
quadratic dispersion curve. In particular, the number of EPs occurring in a
bare discrete Hamiltonian of dimension is given by ; if this discrete Hamiltonian is then coupled to continuum
(or continua) to form an OQS, the interaction with the continuum generally
produces an enlarged discrete solution space that includes a greater number of
EPs, specifically , in which
is the number of (non-degenerate) continua to which the discrete sector is
attached. Finally, we offer a heuristic quantum phase transition analogy for
the emergence of the resonance (giving rise to irreversibility via exponential
decay) in which the decay width plays the role of the order parameter; the
associated critical exponent is then determined by the above eigenvalue
expansion.Comment: 16 pages, 7 figure
Strongly Coupled Matter-Field and Non-Analytic Decay Rate of Dipole Molecules in a Waveguide
The decay rate \gam of an excited dipole molecule inside a waveguide is
evaluated for the strongly coupled matter-field case near a cutoff frequency
\ome_c without using perturbation analysis. Due to the singularity in the
density of photon states at the cutoff frequency, we find that \gam depends
non-analytically on the coupling constant as . In contrast
to the ordinary evaluation of \gam which relies on the Fermi golden rule
(itself based on perturbation analysis), \gam has an upper bound and does not
diverge at \ome_c even if we assume perfect conductance in the waveguide
walls. As a result, again in contrast to the statement found in the literature,
the speed of emitted light from the molecule does not vanish at \ome_c and is
proportional to which is on the order of m/s for
typical dipole molecules.Comment: 4 pages, 2 figure
The interdependence of behavioral and somatic health: implications for conceptualizing health and measuring treatment outcomes
<b>Purpose:</b> The interdependence of behavioral and somatic aspects of various health conditions warrants greater emphasis on an integrated care approach.<br><br> <b>Theory:</b> We propose that integrated approaches to health and wellness require comprehensive and empirically-valid outcome measures to assess quality of care.<br><br> <b>Method:</b> We discuss the transition from independent to integrated treatment approaches and provide examples of new systems for integrated assessment of treatment outcome.<br><br> <b>Results:</b> Evidence suggests that support for an independent treatment approach is waning and momentum is building towards more integrated care. In addition, research evidence suggests integrated care improves health outcomes, and both physicians and patients have favorable impressions of integrated care.<br><br> <b>Conclusions:</b> As treatment goals in the integrated perspective expand to take into account the intimate relationships among mental illness, overall health, and quality of life, clinicians need to develop outcome measures that are similarly comprehensive. Discussion: Increased recognition, by researchers, providers, and insurers, of the interdependence between behavioral and physical health holds great promise for innovative treatments that could significantly improve patients' lives
Electron trapping in a one-dimensional semiconductor quantum wire with multiple impurities
Universal corrections to scaling for block entanglement in spin-1/2 XX chains
We consider the R\'enyi entropies in the one dimensional spin-1/2
Heisenberg XX chain in a magnetic field. The case n=1 corresponds to the von
Neumann ``entanglement'' entropy. Using a combination of methods based on the
generalized Fisher-Hartwig conjecture and a recurrence relation connected to
the Painlev\'e VI differential equation we obtain the asymptotic behaviour,
accurate to order , of the R\'enyi entropies
for large block lengths . For n=1,2,3,10 this constitutes the 3,6,10,48
leading terms respectively. The o(1) contributions are found to exhibit a rich
structure of oscillatory behaviour, which we analyze in some detail both for
finite and in the limit .Comment: 25 pages, 5 figure
Pediculosis and the Pediatrician
Head lice commonly evoke feelings of disgust, revulsion, anger, and shame among parents and patients. There should, however, be no great cause for such alarm if a physician suspects pediculosis capitis. The recent introduction of several new pediculicidal drugs now allows a choice among four distinct therapeutic agents, which should substantially improve control of isolated cases and epidemics. Physicians must be aware that consumer groups are pressing public health authorities and drug manufacturers to establish proper treatment standards and safety warnings for the use of these agents. In addition, some controversy surrounds the use of lindane in children. This paper reviews the epidemiology and clinical appearance of pediculosis capitis in children, with emphasis on these recent developments. Pubic lice ( Phthirus pubis ) and body lice ( Pedicutus humanus corporis ), both of which are much less common pediatric infestations, are mentioned only briefly.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72607/1/j.1525-1470.1984.tb00447.x.pd
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