705 research outputs found
On Zone-Based Analysis of Duration Probabilistic Automata
We propose an extension of the zone-based algorithmics for analyzing timed
automata to handle systems where timing uncertainty is considered as
probabilistic rather than set-theoretic. We study duration probabilistic
automata (DPA), expressing multiple parallel processes admitting memoryfull
continuously-distributed durations. For this model we develop an extension of
the zone-based forward reachability algorithm whose successor operator is a
density transformer, thus providing a solution to verification and performance
evaluation problems concerning acyclic DPA (or the bounded-horizon behavior of
cyclic DPA).Comment: In Proceedings INFINITY 2010, arXiv:1010.611
Can nocturnal hypertension predict cardiovascular risk?
Nocturnal hypertension and non-dipping of blood pressure during sleep are distinct entities that often occur together and are regarded as important harbingers of poor cardiovascular prognosis. This review addresses several aspects related to these blood pressure abnormalities including definitions, diagnostic limitations, pathogenesis and associated patient profiles, prognostic significance, and therapeutic strategies. Taken together, persistent nocturnal hypertension and non-dipping blood pressure pattern, perhaps secondary to abnormal renal sodium handling and/or altered nocturnal sympathovagal balance, are strongly associated with deaths, cardiovascular events, and progressive loss of renal function, independent of daytime and 24-hour blood pressure. Several pharmacological and non-pharmacological approaches may restore nocturnal blood pressure and circadian blood pressure rhythm to normal; however, whether this translates to a clinically meaningful reduction in unfavorable cardiovascular and renal consequences remains to be seen
A new Spring, a new sound
Special editorial from the outgoing and incoming Editor in Chief
Anomalous proximity effect in gold coated (110) films: Penetration of the Andreev bound states
Scanning tunneling spectroscopy of (110) bi-layers
reveal a proximity effect markedly different from the conventional one. While
proximity-induced mini-gaps rarely appear in the Au layer, the Andreev bound
states clearly penetrate into the metal. Zero bias conductance peaks are
measured on Au layers thinner than 7 nm with magnitude similar to those
detected on the bare superconductor films. The peaks then decay abruptly with
Au thickness and disappear above 10 nm. This length is shorter than the normal
coherence length and corresponds to the (ballistic) mean free path.Comment: 5 prl format pages, 4 figures, to be published in PR
Testing read-once formula satisfaction
We study the query complexity of testing for properties defined by read once formulas, as instances of {\em massively parametrized properties}, and prove several testability and non-testability results. First we prove the testability of any property accepted by a Boolean read-once formula involving any bounded arity gates, with a number of queries exponential in , doubly exponential in the arity, and independent of all other parameters. When the gates are limited to being monotone, we prove that there is an {\em estimation} algorithm, that outputs an approximation of the distance of the input from satisfying the property. For formulas only involving And/Or gates, we provide a more efficient test whose query complexity is only quasipolynomial in . On the other hand, we show that such testability results do not hold in general for formulas over non-Boolean alphabets; specifically we construct a property defined by a read-once arity (non-Boolean) formula over an alphabet of size , such that any -test for it requires a number of queries depending on the formula size. We also present such a formula over an alphabet of size that additionally satisfies a strong monotonicity condition
Sediment Management for Southern California Mountians, Coastal Plains and Shoreline. Part D: Special Inland Studies
In southern California the natural environmental system involves the continual relocation of sedimentary materials. Particles are eroded from inland areas where there is sufficient relief and, precipitation. Then, with reductions in hydraulic gradient along the stream course and at the shoreline, the velocity of surface runoff is reduced and there is deposition. Generally, coarse sand, gravel and larger particles are deposited near the base of the eroding surfaces (mountains and hills) and the finer sediments are deposited on floodplains, in bays or lagoons, and at the shoreline as delta deposits. Very fine silt and clay particles, which make up a significant part of the eroded material, are carried offshore where they eventually deposit in deeper areas. Sand deposited at the shoreline is gradually moved along the coast by waves and currents, and provides nourishment for local beaches. However, eventually much of this littoral material is also lost to offshore areas. Human developments in the coastal region have substantially altered the natural sedimentary processes, through changes in land use, the harvesting of natural resources (logging, grazing, and sand and gravel mining); the construction and operation of water conservation facilities and flood control structures; and coastal developments. In almost all cases these developments have grown out of recognized needs and have well served their primary purpose. At the time possible deleterious effects on the local or regional sediment balance were generally unforeseen or were felt to be of secondary importance. In 1975 a large-scale study of inland and coastal sedimentation processes in southern California was initiated by the Environmental Quality Laboratory at the California Institute of Technology and the Center for Coastal Studies at Scripps Institution of Oceanography. This volume is one of a series of reports from this study. Using existing data bases, this series attempts to define quantitatively inland and coastal sedimentation processes and identify the effects man has had on these processes. To resolve some issues related to long-term sediment management, additional research and data will be needed. In the series there are four Caltech reports that provide supporting studies for the summary report (EQL Report No. 17). These reports include: EQL Report 17-A Regional Geological History EQL Report 17-B Inland Sediment Movements by Natural Processes EQL Report 17-C Coastal Sediment Delivery by Major Rivers in Southern California EQL Report 17-D -- Special Inland Studies Additional supporting reports on coastal studies (shoreline sedimentation processes, control structures, dredging, etc.) are being published by the Center for Coastal Studies at Scripps Institution of Oceanography, La Jolla, California
Constructing Spin Interference Devices from Nanometric Rings
The study of nanospintronic devices utilizing coherent transport through
molecular scale multiply-connected geometries in the presence of moderate
magnetic fields is presented. It is shown how two types of simple devices, spin
filters and spin splitters (or Stern-Gerlach devices) may be constructed from
molecular nanometric rings utilizing the Aharonov-Bohm effect. The current is
calculated within a single electron approximation and within a many-body master
equation approach where charging effects are accounted for in the Coulomb
Blockade regime. We provide rules and tools to develop and analyze efficient
spintronic devices based on nanometric interferometers.Comment: 16 pages, 8 figures, submitted to Phys. Rev.
Superlubricity - a new perspective on an established paradigm
Superlubricity is a frictionless tribological state sometimes occurring in
nanoscale material junctions. It is often associated with incommensurate
surface lattice structures appearing at the interface. Here, by using the
recently introduced registry index concept which quantifies the registry
mismatch in layered materials, we prove the existence of a direct relation
between interlayer commensurability and wearless friction in layered materials.
We show that our simple and intuitive model is able to capture, down to fine
details, the experimentally measured frictional behavior of a hexagonal
graphene flake sliding on-top of the surface of graphite. We further predict
that superlubricity is expected to occur in hexagonal boron nitride as well
with tribological characteristics very similar to those observed for the
graphitic system. The success of our method in predicting experimental results
along with its exceptional computational efficiency opens the way for modeling
large-scale material interfaces way beyond the reach of standard simulation
techniques.Comment: 18 pages, 7 figure
The primary structure of rat ribosomal protein L18a
AbstractThe amino acid sequence of rat ribosomal protein L18a was deduced from the sequence of nucleotides in a recombinant cDNA. Ribosomal protein L18a contains 175 amino acids and has a molecular mass of 20 047 Da. Hybridization of the cDNA to digests of rat nuclear DNA and to a preparation of poly (A)+ mRNA suggests that there are 8β11 copies of the L18a gene and that the mRNA for the protein is about 700 nucleotides in length. Rat L18a is related to Schizosaccharomyces pombe L17 and perhaps to Halobacterium marismortui L19
Casimir forces in a T operator approach
We explore the scattering approach to Casimir forces. Our main tool is the
description of Casimir energy in terms of transition operators, as presented in
Kenneth and Klich, Phys. Rev. Lett. 97, 160401 (2006). We study the convergence
properties of the formula and how to utilize it, together with scattering data
to compute the force. We illustrate the approach by describing the force
between scatterers in 1d and 3d,, and in particular show how it may be applied
in order to study the interaction between two spherical bodies at all
distances
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