5,872 research outputs found
Two classes of nonlocal Evolution Equations related by a shared Traveling Wave Problem
We consider reaction-diffusion equations and Korteweg-de Vries-Burgers (KdVB)
equations, i.e. scalar conservation laws with diffusive-dispersive
regularization. We review the existence of traveling wave solutions for these
two classes of evolution equations. For classical equations the traveling wave
problem (TWP) for a local KdVB equation can be identified with the TWP for a
reaction-diffusion equation. In this article we study this relationship for
these two classes of evolution equations with nonlocal diffusion/dispersion.
This connection is especially useful, if the TW equation is not studied
directly, but the existence of a TWS is proven using one of the evolution
equations instead. Finally, we present three models from fluid dynamics and
discuss the TWP via its link to associated reaction-diffusion equations
Context-Free Path Queries on RDF Graphs
Navigational graph queries are an important class of queries that canextract
implicit binary relations over the nodes of input graphs. Most of the
navigational query languages used in the RDF community, e.g. property paths in
W3C SPARQL 1.1 and nested regular expressions in nSPARQL, are based on the
regular expressions. It is known that regular expressions have limited
expressivity; for instance, some natural queries, like same generation-queries,
are not expressible with regular expressions. To overcome this limitation, in
this paper, we present cfSPARQL, an extension of SPARQL query language equipped
with context-free grammars. The cfSPARQL language is strictly more expressive
than property paths and nested expressions. The additional expressivity can be
used for modelling graph similarities, graph summarization and ontology
alignment. Despite the increasing expressivity, we show that cfSPARQL still
enjoys a low computational complexity and can be evaluated efficiently.Comment: 25 page
Distribution of entanglement in light-harvesting complexes and their quantum efficiency
Recent evidence of electronic coherence during energy transfer in
photosynthetic antenna complexes has reinvigorated the discussion of whether
coherence and/or entanglement has any practical functionality for these
molecular systems. Here we investigate quantitative relationships between the
quantum yield of a light-harvesting complex and the distribution of
entanglement among its components. Our study focusses on the entanglement yield
or average entanglement surviving a time scale comparable to the average
excitation trapping time. As a prototype system we consider the
Fenna-Matthews-Olson (FMO) protein of green sulphur bacteria and show that
there is an inverse relationship between the quantum efficiency and the average
entanglement between distant donor sites. Our results suggest that longlasting
electronic coherence among distant donors might help modulation of the
lightharvesting function.Comment: Version accepted for publication in NJ
Caregiver distress in parkinsonism
This study examined the frequency and degree of caregiver burden in persons with parkinsonism, a group of disorders with four primary symptoms that include tremor, rigidity, postural instability, and bradykinesia. We assessed associations between perceived caregiver burden and physical, cognitive, and functional impairments using well-established tools for persons with parkinsonism. The 49 individuals with parkinsonism ranged in age from 61 to 87 (mean = 75), while their caregivers (N = 49) ranged in age from 48 to 83 (mean = 70). The caregivers were predominantly either wives (82%) or daughters (6%), with other family members, friends, and/or neighbors (12%) making up the rest. The caregivers reported a relatively high ability for coping (mean scores = 4.6/6). Caregiver burden was significantly negatively associated with activities of daily living and motoric difficulties as measured on the Unified Parkinson\u27s Disease Rating Scale (UPDRS). Likewise, caregiver burden was negatively associated with caregiver self-reported sleep and coping ability. Results did not demonstrate an association on the UPDRS among mentation, behavior, and mood. We found a significant negative correlation for mentation between the Folstein Mini-Mental Status Examination and caregiver burden measures; however, we did not find this association with the Dementia Rating Scale-2. Patient\u27s self-reported pain and caregiver burden were not associated
The [CII] 158 um Line Deficit in Ultraluminous Infrared Galaxies Revisited
We present a study of the [CII] 157.74 um fine-structure line in a sample of
15 ultraluminous infrared (IR) galaxies (L_IR>10^12 Lsun; ULIRGs) using the
Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We
confirm the observed order of magnitude deficit (compared to normal and
starburst galaxies) in the strength of the [CII] line relative to the far-IR
dust continuum emission found in our initial report (Luhman et al. 1998), but
here with a sample that is twice as large. This result suggests that the
deficit is a general phenomenon affecting 4/5 ULIRGs. We present an analysis
using observations of generally acknowledged photodissociation region (PDR)
tracers ([CII], [OI] 63 and 145 um, and FIR continuum emission), which suggests
that a high UV flux G_o incident on a moderate density n PDR could explain the
deficit. However, comparisons with other ULIRG observations, including CO
(1-0), [CI] (1-0), and 6.2 um polycyclic aromatic hydrocarbon (PAH) emission,
suggest that high G_o/n PDRs alone cannot produce a self-consistent solution
that is compatible with all of the observations. We propose that non-PDR
contributions to the FIR continuum can explain the apparent [CII] deficiency.
Here, unusually high G_o and/or n physical conditions in ULIRGs as compared to
those in normal and starburst galaxies are not required to explain the [CII]
deficit. Dust-bounded photoionization regions, which generate much of the FIR
emission but do not contribute significant [CII] emission, offer one possible
physical origin for this additional non-PDR component. Such environments may
also contribute to the observed suppression of FIR fine-structure emission from
ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The
implications for observations at higher redshifts are also revisited.Comment: to be published in The Astrophysical Journal, 58 page
Exceptional chemotherapy response in metastatic colorectal cancer associated with hyper-indel-hypermutated cancer genome and comutation of POLD1 and MLH1
Purpose A 73-year-old woman with metastatic colon cancer experienced a complete response to chemotherapy with dose-intensified irinotecan that has been durable for 5 years.Wesequenced her tumor and germ line DNA and looked for similar patterns in publicly available genomic data from patients with colorectal cancer. Patients and Methods Tumor DNA was obtained from a biopsy before therapy, and germ line DNA was obtained from blood. Tumor and germline DNA were sequenced using a commercial panel with approximately 250 genes. Whole-genome amplification and exome sequencing were performed for POLE and POLD1. A POLD1 mutation was confirmed by Sanger sequencing. The somatic mutation and clinical annotation data files from the colon (n = 461) and rectal (n = 171) adenocarcinoma data sets were downloaded from The Cancer Genome Atlas data portal and analyzed for patterns of mutations and clinical outcomes in patients withPOLE- and/orPOLD1- mutated tumors. Results The pattern of alterations included APC biallelic inactivation and microsatellite instability high (MSI-H) phenotype, with somatic inactivation of MLH1 and hypermutation (estimated mutation rate > 200 per megabase). The extremely high mutation rate led us to investigate additional mechanisms for hypermutation, including loss of function of POLE. POLE was unaltered, but a related gene not typically associated with somatic mutation in colon cancer, POLD1, had a somatic mutation c.2171G > A[p.Gly724Glu]. Additionally, we noted that the high mutation rate was largely composed of dinucleotide deletions. A similar pattern of hypermutation (dinucleotide deletions, POLD1 mutations, MSI-H) was found in tumors from The Cancer Genome Atlas. Conclusion POLD1 mutation with associated MSI-H and hyper-indel-hypermutated cancer genome characterizes a previously unrecognized variant of colon cancer that was found in this patient with an exceptional response to chemotherapy
On a kinetic model for a simple market economy
In this paper, we consider a simple kinetic model of economy involving both
exchanges between agents and speculative trading. We show that the kinetic
model admits non trivial quasi-stationary states with power law tails of Pareto
type. In order to do this we consider a suitable asymptotic limit of the model
yielding a Fokker-Planck equation for the distribution of wealth among
individuals. For this equation the stationary state can be easily derived and
shows a Pareto power law tail. Numerical results confirm the previous analysis
Non-Markovian stochastic description of quantum transport in photosynthetic systems
We analyze several aspects of the transport dynamics in the LH1-RC core of
purple bacteria, which consists basically in a ring of antenna molecules that
transport the energy into a target molecule, the reaction center, placed in the
center of the ring. We show that the periodicity of the system plays an
important role to explain the relevance of the initial state in the transport
efficiency. This picture is modified, and the transport enhanced for any
initial state, when considering that molecules have different energies, and
when including their interaction with the environment. We study this last
situation by using stochastic Schr{\"o}dinger equations, both for Markovian and
non-Markovian type of interactions.Comment: 21 pages, 5 figure
Electronic and nuclear contributions to time-resolved optical and X-ray absorption spectra of hematite and insights into photoelectrochemical performance
Ultrafast time-resolved studies of photocatalytic thin films can provide a wealth of information crucial for understanding and thereby improving the performance of these materials by directly probing electronic structure, reaction intermediates, and charge carrier dynamics. The interpretation of transient spectra, however, can be complicated by thermally induced structural distortions, which appear within the first few picoseconds following excitation due to carrierâphonon scattering. Here we present a comparison of ex situ steady-state thermal difference spectra and transient absorption spectra spanning from NIR to hard X-ray energies of hematite thin films grown by atomic layer deposition. We find that beyond the first 100 picoseconds, the transient spectra measured for all excitation wavelengths and probe energies are almost entirely due to thermal effects as the lattice expands in response to the ultrafast temperature jump and then cools to room temperature on the microsecond timescale. At earlier times, a broad excited state absorption band that is assigned to free carriers appears at 675 nm, and the lifetime and shape of this feature also appear to be mostly independent of excitation wavelength. The combined spectroscopic data, which are modeled with density functional theory and full multiple scattering calculations, support an assignment of the optical absorption spectrum of hematite that involves two LMCT bands that nearly span the visible spectrum. Our results also suggest a framework for shifting the ligand-to-metal charge transfer absorption bands of ferric oxide films from the near-UV further into the visible part of the solar spectrum to improve solar conversion efficiency
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