1,047 research outputs found
Energy levels and lifetimes of Nd IV, Pm IV, Sm IV, and Eu IV
To address the shortage of experimental data for electron spectra of
triply-ionized rare earth elements we have calculated energy levels and
lifetimes of 4f{n+1} and 4f{n}5d configurations of Nd IV (n=2), Pm IV (n=3), Sm
IV (n=4), and Eu IV (n=5) using Hartree-Fock and configuration interaction
methods. To control the accuracy of our calculations we also performed similar
calculations for Pr III, Nd III and Sm III, for which experimental data are
available. The results are important, in particular, for physics of magnetic
garnets.Comment: 4 pages 1 tabl
National and international kidney failure registries: characteristics, commonalities, and contrasts
Registries are essential for health infrastructure planning, benchmarking, continuous quality improvement, hypothesis generation, and real-world trials. To date, data from these registries have predominantly been analyzed in isolated “silos,” hampering efforts to analyze “big data” at the international level, an approach that provides wide-ranging benefits, including enhanced statistical power, an ability to conduct international comparisons, and greater capacity to study rare diseases. This review serves as a valuable resource to clinicians, researchers, and policymakers, by comprehensively describing kidney failure registries active in 2021, before proposing approaches for inter-registry research under current conditions, as well as solutions to enhance global capacity for data collaboration. We identified 79 kidney-failure registries spanning 77 countries worldwide. International Society of Nephrology exemplar initiatives, including the Global Kidney Health Atlas and Sharing Expertise to support the set-up of Renal Registries (SharE-RR), continue to raise awareness regarding international healthcare disparities and support the development of universal kidney-disease registries. Current barriers to inter-registry collaboration include underrepresentation of lower-income countries, poor syntactic and semantic interoperability, absence of clear consensus guidelines for healthcare data sharing, and limited researcher incentives. This review represents a call to action for international stakeholders to enact systemic change that will harmonize the current fragmented approaches to kidney-failure registry data collection and research
Non-Perturbative String Equations for Type 0A
Well-defined non-perturbative formulations of the physics of string theories,
sometimes with D-branes present, were identified over a decade ago, from a
careful study of double scaled matrix models. Following recent work which
recasts some of those old results in the context of type 0 string theory, a
study is made of a much larger family of models, which are proposed as type 0A
models of the entire superconformal minimal series coupled to gravity. This
gives many further examples of important physical phenomena, including
non-perturbative descriptions of transitions between D-branes and fluxes,
tachyon condensation, and holography. In particular, features of a large family
of non-perturbatively stable string equations are studied, and results are
extracted which pertain to type 0A string theory, with D-branes and fluxes, in
this large class of backgrounds. For the entire construction to work, large
parts of the spectrum of the supergravitationally dressed superconformal
minimal models and that of the gravitationally dressed bosonic conformal
minimal models must coincide, and it is shown how this happens. The example of
the super-dressed tricritical Ising model is studied in some detail.Comment: 29 pages LaTe
Tachyon Condensation, Open-Closed Duality, Resolvents, and Minimal Bosonic and Type 0 Strings
Type 0A string theory in the (2,4k) superconformal minimal model backgrounds
and the bosonic string in the (2,2k-1) conformal minimal models, while
perturbatively identical in some regimes, may be distinguished
non-perturbatively using double scaled matrix models. The resolvent of an
associated Schrodinger operator plays three very important interconnected
roles, which we explore perturbatively and non-perturbatively. On one hand, it
acts as a source for placing D-branes and fluxes into the background, while on
the other, it acts as a probe of the background, its first integral yielding
the effective force on a scaled eigenvalue. We study this probe at disc, torus
and annulus order in perturbation theory, in order to characterize the effects
of D-branes and fluxes on the matrix eigenvalues. On a third hand, the
integrated resolvent forms a representation of a twisted boson in an associated
conformal field theory. The entire content of the closed string theory can be
expressed in terms of Virasoro constraints on the partition function, which is
realized as wavefunction in a coherent state of the boson. Remarkably, the
D-brane or flux background is simply prepared by acting with a vertex operator
of the twisted boson. This generates a number of sharp examples of open-closed
duality, both old and new. We discuss whether the twisted boson conformal field
theory can usefully be thought of as another holographic dual of the
non-critical string theory.Comment: 37 pages, some figures, LaTe
Strong Influence of Phonons on the Electron Dynamics of Bi2212
The sudden change of the velocity, so-called "kink," of the dispersing peak
in angle resolved photoelectron spectroscopy is a well-known feature in the
high temperature superconducting cuprates. Currently, the origin of the kink is
being much debated, but a consensus has not emerged yet. Here, we present a
study of the momentum evolution of the kink structure from the nodal region
towards the anti-nodal region, for optimally doped Bi2212 sample. We show that
the observed temperature dependence of the kink structure in both regions of
the momentum space is consistent with a scenario in which phonons contribute
strongly to the kink
Notes on the algebraic curves in (p,q) minimal string theory
Loop amplitudes in (p,q) minimal string theory are studied in terms of the
continuum string field theory based on the free fermion realization of the KP
hierarchy. We derive the Schwinger-Dyson equations for FZZT disk amplitudes
directly from the W_{1+\infty} constraints in the string field formulation and
give explicitly the algebraic curves of disk amplitudes for general
backgrounds. We further give annulus amplitudes of FZZT-FZZT, FZZT-ZZ and ZZ-ZZ
branes, generalizing our previous D-instanton calculus from the minimal unitary
series (p,p+1) to general (p,q) series. We also give a detailed explanation on
the equivalence between the Douglas equation and the string field theory based
on the KP hierarchy under the W_{1+\infty} constraints.Comment: 61 pages, 1 figure, section 2.5 and Appendix B added, references
added, final version to appear in JHE
Structure Formation, Melting, and the Optical Properties of Gold/DNA Nanocomposites: Effects of Relaxation Time
We present a model for structure formation, melting, and optical properties
of gold/DNA nanocomposites. These composites consist of a collection of gold
nanoparticles (of radius 50 nm or less) which are bound together by links made
up of DNA strands. In our structural model, the nanocomposite forms from a
series of Monte Carlo steps, each involving reaction-limited cluster-cluster
aggregation (RLCA) followed by dehybridization of the DNA links. These links
form with a probability which depends on temperature and particle
radius . The final structure depends on the number of monomers (i. e. gold
nanoparticles) , , and the relaxation time. At low temperature, the
model results in an RLCA cluster. But after a long enough relaxation time, the
nanocomposite reduces to a compact, non-fractal cluster. We calculate the
optical properties of the resulting aggregates using the Discrete Dipole
Approximation. Despite the restructuring, the melting transition (as seen in
the extinction coefficient at wavelength 520 nm) remains sharp, and the melting
temperature increases with increasing as found in our previous
percolation model. However, restructuring increases the corresponding link
fraction at melting to a value well above the percolation threshold. Our
calculated extinction cross section agrees qualitatively with experiments on
gold/DNA composites. It also shows a characteristic ``rebound effect,''
resulting from incomplete relaxation, which has also been seen in some
experiments. We discuss briefly how our results relate to a possible sol-gel
transition in these aggregates.Comment: 12 pages, 10 figure
Annulus Amplitudes and ZZ Branes in Minimal String Theory
We study the annulus amplitudes of (p,q) minimal string theory. Focusing on
the ZZ-FZZT annulus amplitude as a target-space probe of the ZZ brane, we use
it to confirm that the ZZ branes are localized in the strong-coupling region.
Along the way we learn that the ZZ-FZZT open strings are fermions, even though
our theory is bosonic! We also provide a geometrical interpretation of the
annulus amplitudes in terms of the Riemann surface M_{p,q} that emerges from
the FZZT branes. The ZZ-FZZT annulus amplitude measures the deformation of
M_{p,q} due to the presence of background ZZ branes; each kind of ZZ-brane
deforms only one A-period of the surface. Finally, we use the annulus
amplitudes to argue that the ZZ branes can be regarded as "wrong-branch"
tachyons which violate the bound \alpha<Q/2.Comment: 33 pages, new results in appendix, minor change
Branes, Rings and Matrix Models in Minimal (Super)string Theory
We study both bosonic and supersymmetric (p,q) minimal models coupled to
Liouville theory using the ground ring and the various branes of the theory.
From the FZZT brane partition function, there emerges a unified, geometric
description of all these theories in terms of an auxiliary Riemann surface
M_{p,q} and the corresponding matrix model. In terms of this geometric
description, both the FZZT and ZZ branes correspond to line integrals of a
certain one-form on M_{p,q}. Moreover, we argue that there are a finite number
of distinct (m,n) ZZ branes, and we show that these ZZ branes are located at
the singularities of M_{p,q}. Finally, we discuss the possibility that the
bosonic and supersymmetric theories with (p,q) odd and relatively prime are
identical, as is suggested by the unified treatment of these models.Comment: 72 pages, 3 figures, improved treatment of FZZT and ZZ branes, minor
change
Nanofabrication by magnetic focusing of supersonic beams
We present a new method for nanoscale atom lithography. We propose the use of
a supersonic atomic beam, which provides an extremely high-brightness and cold
source of fast atoms. The atoms are to be focused onto a substrate using a thin
magnetic film, into which apertures with widths on the order of 100 nm have
been etched. Focused spot sizes near or below 10 nm, with focal lengths on the
order of 10 microns, are predicted. This scheme is applicable both to precision
patterning of surfaces with metastable atomic beams and to direct deposition of
material.Comment: 4 pages, 3 figure
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