27,663 research outputs found
The preparation and evaluation of high-purity, fine-grained tungsten and tungsten alloy castings summary report
High purity, cylindrical castings of high melting point materials such as tungsten and tungsten alloy
Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations
Abstract On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (\u3e2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased \u3e90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi-MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere. Key Points Substorm dynamics are important for highly relativistic electron energization Cold plasma preconditioning is significant for rapid relativistic energization Relativistic / highly relativistic electron energization can occur in \u3c 5 hrs
Link and subgraph likelihoods in random undirected networks with fixed and partially fixed degree sequence
The simplest null models for networks, used to distinguish significant
features of a particular network from {\it a priori} expected features, are
random ensembles with the degree sequence fixed by the specific network of
interest. These "fixed degree sequence" (FDS) ensembles are, however, famously
resistant to analytic attack. In this paper we introduce ensembles with
partially-fixed degree sequences (PFDS) and compare analytic results obtained
for them with Monte Carlo results for the FDS ensemble. These results include
link likelihoods, subgraph likelihoods, and degree correlations. We find that
local structural features in the FDS ensemble can be reasonably well estimated
by simultaneously fixing only the degrees of few nodes, in addition to the
total number of nodes and links. As test cases we use a food web, two protein
interaction networks (\textit{E. coli, S. cerevisiae}), the internet on the
autonomous system (AS) level, and the World Wide Web. Fixing just the degrees
of two nodes gives the mean neighbor degree as a function of node degree,
, in agreement with results explicitly obtained from rewiring. For
power law degree distributions, we derive the disassortativity analytically. In
the PFDS ensemble the partition function can be expanded diagrammatically. We
obtain an explicit expression for the link likelihood to lowest order, which
reduces in the limit of large, sparse undirected networks with links and
with to the simple formula . In a
similar limit, the probability for three nodes to be linked into a triangle
reduces to the factorized expression .Comment: 17 pages, includes 11 figures; first revision: shortened to 14 pages
(7 figures), added discussion of subgraph counts, deleted discussion of
directed network
Cygnus X-3 in outburst : quenched radio emission, radiation losses and variable local opacity
We present multiwavelength observations of Cygnus X-3 during an extended
outburst in 1994 February - March. Intensive radio monitoring at 13.3, 3.6 &
2.0 cm is complemented by observations at (sub)millimetre and infrared
wavelengths, which find Cyg X-3 to be unusually bright and variable, and
include the first reported detection of the source at 0.45 mm. We report the
first confirmation of quenched radio emission prior to radio flaring
independent of observations at Green Bank. The observations reveal evidence for
wavelength-dependent radiation losses and gradually decreasing opacity in the
environment of the radio jet. We find that the radiation losses are likely to
be predominantly inverse Compton losses experienced by the radio-emitting
electrons in the strong radiation field of a luminous companion to the compact
object. We interpret the decreasing opacity during the flare sequence as
resulting from a decreasing proportion of thermal electrons entrained in the
jet, reflecting a decreasing density in the region of jet formation. We
present, drawing in part on the work of other authors, a model based upon
mass-transfer rate instability predicting gamma-ray, X-ray, infrared and radio
trends during a radio flaring sequence.Comment: LaTeX, 11 pages, 6 figures. Submitted to MNRA
Count three for wear able computers
This paper is a postprint of a paper submitted to and accepted for publication in the Proceedings of the IEE Eurowearable 2003 Conference, and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.
A revised version of this paper was also published in Electronics Systems and Software, also subject to Institution of Engineering and Technology Copyright. The copy of record is also available at the IET Digital Library.A description of 'ubiquitous computer' is presented. Ubiquitous computers imply portable computers embedded into everyday objects, which would replace personal computers. Ubiquitous computers can be mapped into a three-tier scheme, differentiated by processor performance and flexibility of function. The power consumption of mobile devices is one of the most important design considerations. The size of a wearable system is often a design limitation
Can Self-Organizing Maps accurately predict photometric redshifts?
We present an unsupervised machine learning approach that can be employed for
estimating photometric redshifts. The proposed method is based on a vector
quantization approach called Self--Organizing Mapping (SOM). A variety of
photometrically derived input values were utilized from the Sloan Digital Sky
Survey's Main Galaxy Sample, Luminous Red Galaxy, and Quasar samples along with
the PHAT0 data set from the PHoto-z Accuracy Testing project. Regression
results obtained with this new approach were evaluated in terms of root mean
square error (RMSE) to estimate the accuracy of the photometric redshift
estimates. The results demonstrate competitive RMSE and outlier percentages
when compared with several other popular approaches such as Artificial Neural
Networks and Gaussian Process Regression. SOM RMSE--results (using
z=z--z) for the Main Galaxy Sample are 0.023, for the
Luminous Red Galaxy sample 0.027, Quasars are 0.418, and PHAT0 synthetic data
are 0.022. The results demonstrate that there are non--unique solutions for
estimating SOM RMSEs. Further research is needed in order to find more robust
estimation techniques using SOMs, but the results herein are a positive
indication of their capabilities when compared with other well-known methods.Comment: 5 pages, 3 figures, submitted to PAS
Systematic derivation of a surface polarization model for planar perovskite solar cells
Increasing evidence suggests that the presence of mobile ions in perovskite
solar cells can cause a current-voltage curve hysteresis. Steady state and
transient current-voltage characteristics of a planar metal halide
CHNHPbI perovskite solar cell are analysed with a drift-diffusion
model that accounts for both charge transport and ion vacancy motion. The high
ion vacancy density within the perovskite layer gives rise to narrow Debye
layers (typical width 2nm), adjacent to the interfaces with the transport
layers, over which large drops in the electric potential occur and in which
significant charge is stored. Large disparities between (I) the width of the
Debye layers and that of the perovskite layer (600nm) and (II) the ion
vacancy density and the charge carrier densities motivate an asymptotic
approach to solving the model, while the stiffness of the equations renders
standard solution methods unreliable. We derive a simplified surface
polarisation model in which the slow ion dynamic are replaced by interfacial
(nonlinear) capacitances at the perovskite interfaces. Favourable comparison is
made between the results of the asymptotic approach and numerical solutions for
a realistic cell over a wide range of operating conditions of practical
interest.Comment: 32 pages, 7 figure
Examining c-di-GMP and possible quorum sensing regulation in Pseudomonas fluorescens SBW25:links between intra and inter-cellular regulation benefits community cooperative activities such as biofilm formation
Bacterial success in colonizing complex environments requires individual response to micro-scale conditions as well as community-level cooperation to produce large-scale structures such as biofilms. Connecting individual and community responses could be achieved by linking the intracellular sensory and regulatory systems mediated by bis-(3β²-5β²)-cyclic dimeric guanosine monophosphate (c-di-GMP) and other compounds of individuals with intercellular quorum sensing (QS) regulation controlling populations. There is growing evidence to suggest that biofilm formation by many pseudomonads is regulated by both intra and intercellular systems, though in the case of the model Pseudomonas fluorescens SBW25 Wrinkly Spreader in which mutations increasing c-di-GMP levels result in the production of a robust cellulose-based air-liquid interface biofilm, no evidence for the involvement of QS regulation has been reported. However, our recent review of the P. fluorescens SBW25 genome has identified a potential QS regulatory pathway and other QSβassociated genes linked to c-di-GMP homeostasis, and QS signal molecules have also been identified in culture supernatants. These findings suggest a possible link between c-di-GMP and QS regulation in P. fluorescens SBW25 which might allow a more sophisticated and responsive control of cellulose production and biofilm formation when colonising the soil and plant-associated environments P. fluorescens SBW25 normally inhabits.ΠΠ½Π°Π»ΠΈΠ· Ρ-Π΄ΠΈ-ΠΠΠ€ ΠΈ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΠ³ΠΎ ΡΡΠ²ΡΡΠ²Π° ΠΊΠ²ΠΎΡΡΠΌΠ° Ρ Pseudomonas fluorescens SBW 25: ΡΠ²ΡΠ·Ρ ΠΌΠ΅ΠΆΠ΄Ρ Π²Π½ΡΡΡΠΈ ΠΈ ΠΌΠ΅ΠΆΠΊΠ»Π΅ΡΠΎΡΠ½ΠΎΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΈΠ΅ΠΉ ΡΠΏΠΎΡΠΎΠ±ΡΡΠ²ΡΠ΅Ρ ΠΊΠΎΠΎΠΏΠ΅ΡΠ°ΡΠΈΠ²Π½ΠΎΠΌΡ ΠΏΠΎΠ²Π΅Π΄Π΅Π½ΠΈΡ Π² ΡΠΎΠΎΠ±ΡΠ΅ΡΡΠ²Π΅ ΠΈ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π±ΠΈΠΎΠΏΠ»ΡΠ½ΠΊΠΈΠ£ΡΠΏΠ΅ΡΠ½ΠΎΡΡΡ Π±Π°ΠΊΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΠΎΠΉ ΠΊΠΎΠ»ΠΎΠ½ΠΈΠ·Π°ΡΠΈΠΈ ΡΠ»ΠΎΠΆΠ½ΡΡ
ΡΠΊΠΎΠ½ΠΈΡ ΡΡΠ΅Π±ΡΠ΅Ρ ΠΈΠ½Π΄ΠΈΠ²ΠΈΠ΄ΡΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΎΡΠ²Π΅ΡΠ° Π½Π° ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΡ ΡΡΠ»ΠΎΠ²ΠΈΠΉ Π½Π° ΠΌΠΈΠΊΡΠΎΡΡΠΎΠ²Π½Π΅ ΡΠ°Π²Π½ΠΎ ΠΊΠ°ΠΊ ΠΈ ΠΊΠΎΠΎΠΏΠ΅ΡΠ°ΡΠΈΠΈ Π½Π° ΡΡΠΎΠ²Π½Π΅ ΡΠΎΠΎΠ±ΡΠ΅ΡΡΠ²Π° Π΄Π»Ρ ΠΏΡΠΎΠ΄ΡΠΊΡΠΈΠΈ ΡΠ°ΠΊΠΈΡ
ΠΊΡΡΠΏΠ½ΠΎ ΠΌΠ°ΡΡΡΠ°Π±Π½ΡΡ
ΡΡΡΡΠΊΡΡΡ ΠΊΠ°ΠΊ Π±ΠΈΠΎΠΏΠ»ΡΠ½ΠΊΠΈ. ΠΠΎΠΎΡΠ΄ΠΈΠ½Π°ΡΠΈΡ ΠΈΠ½Π΄ΠΈΠ²ΠΈΠ΄ΡΠ°Π»ΡΠ½ΡΡ
ΠΎΡΠ²Π΅Ρ ΠΎΠ² ΠΈ ΠΎΡΠ²Π΅ΡΠΎΠ² ΡΠΎΠΎΠ±ΡΠ΅ΡΡΠ²Π° ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ Π΄ΠΎΡΡΠΈΠ³Π½ΡΡΠ° ΠΏΡΡΠ΅ΠΌ ΡΠ²ΡΠ·ΡΠ²Π°Π½ΠΈΡ Π²Π½ΡΡΡΠΈΠΊΠ»Π΅ΡΠΎΡΠ½ΡΡ
ΡΠ΅Π½ΡΠΎΡΠ½ΡΡ
ΠΈ ΡΠ΅Π³ΡΠ»ΡΡΠΎΡΠ½ΡΡ
ΡΠΈΡΡΠ΅ΠΌ, ΠΎΠΏΠΎΡΡΠ΅Π΄ΡΠ΅ΠΌΡΡ
Π±ΠΈΡ-(3',5')-ΡΠΈΠΊΠ»ΠΈΡΠ΅ΡΠΊΠΈΠΌ Π΄ΠΈΠΌΠ΅ΡΠ½ΡΠΌ Π³ΡΠ°Π½ΠΎΠ·ΠΈΠ½ΠΌΠΎΠ½ΠΎΡΠΎΡΡΠ°ΡΠΎΠΌ (Ρ-Π΄ΠΈ-ΠΠΠ€) ΠΈ Π΄ΡΡΠ³ΠΈΠΌΠΈ ΡΠΎΠ΅Π΄ΠΈΠ½Π΅Π½ΠΈΡΠΌΠΈ ΠΈΠ½Π΄ΠΈΠ²ΠΈΠ΄ΡΡΠΌΠΎΠ² Ρ ΠΌΠ΅ΠΆΠΊΠ»Π΅ΡΠΎΡΠ½ΠΎΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΈΠ΅ΠΉ - ΡΡΠ²ΡΡΠ²ΠΎΠΌ ΠΊΠ²ΠΎΡΡΠΌΠ° (Π§Π), ΠΊΠΎΠ½ΡΡΠΎΠ»ΠΈΡΡΡΡΠ΅ΠΌ ΠΏΠΎΠΏΡΠ»ΡΡΠΈ Ρ. ΠΠ°ΠΊΠ°ΠΏΠ»ΠΈΠ²Π°Π΅ΡΡΡ Π²ΡΡ Π±ΠΎΠ»ΡΡΠ΅ Π΄ΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΡΡΡΠ² ΡΠΎΠ³ΠΎ, ΡΡΠΎ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π±ΠΈΠΎΠΏΠ»Π΅Π½ΠΊΠΈ ΠΌΠ½ΠΎΠ³ΠΈΠΌΠΈ ΠΏΡΠ΅Π²Π΄ΠΎΠΌΠΎΠ½Π°Π΄Π°ΠΌΠΈ ΡΠ΅Π³ΡΠ»ΠΈΡΡΠ΅ΡΡΡ ΠΊΠ°ΠΊ Π²Π½ΡΡΡΠΈ ΠΊΠ»Π΅ΡΠΎΡΠ½ΡΠΌΠΈ, ΡΠ°ΠΊ ΠΈ ΠΌΠ΅ΠΆ ΠΊΠ»Π΅ΡΠΎΡΠ½ΡΠΌΠΈ ΡΠ΅Π³ΡΠ»ΡΡΠΎΡΠ½ΡΠΌΠΈ ΡΠΈΡΡΠ΅ΠΌΠ°ΠΌΠΈ, Ρ
ΠΎΡΡ Π² ΡΠ»ΡΡΠ°Π΅ ΠΌΠΎΠ΄Π΅Π»ΡΠ½ΠΎΠΉ Pseudomonas fluorescens SBW25 Wrinkly Spreader, Ρ ΠΊΠΎΡΠΎΡΠΎΠΉ ΠΌΡΡΠ°ΡΠΈΠΈ, ΠΏΠΎΠ²ΡΡΠ°ΡΡ ΠΈΠ΅ ΡΡΠΎΠ²Π½ΠΈ Ρ-Π΄ΠΈ-ΠΠΠ€, ΠΏΡΠΈΠ²ΠΎΠ΄ΡΡ ΠΊ ΡΠΎΠ·Π΄Π°Π½ΠΈΡ ΠΏΡΠΎΡΠ½ΠΎΠΉ ΡΠ΅Π»Π»ΡΠ»ΠΎΠ·Π½ΠΎΠΉ Π±ΠΈΠΎΠΏΠ»ΡΠ½ΠΊΠΈ Π½Π° Π³ΡΠ°Π½ΠΈΡΠ΅ ΡΠ°Π·Π΄Π΅Π»Π° ΡΠ°Π· Π²ΠΎΠ·Π΄ΡΡ
-ΠΆΠΈΠ΄ΠΊΠΎΡΡΡ, Π½Π΅ Π±ΡΠ»ΠΎ ΠΎΠ±Π½Π°ΡΡΠΆΠ΅Π½ΠΎ Π½ΠΈ ΠΊΠ° ΠΊΠΎΠ³ΠΎ ΡΠ²ΠΈΠ΄Π΅ΡΠ΅Π»ΡΡΡΠ²Π° Π²ΠΎΠ²Π»Π΅ΡΠ΅Π½ΠΈΡ ΠΊΠ²ΠΎΡΡΠΌ-Π·Π°Π²ΠΈΡΠΈΠΌΠΎΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΈΠΈ. ΠΠ΄Π½Π°ΠΊΠΎ Π½Π°Ρ Π½Π΅Π΄Π°Π²Π½ΠΈΠΉ ΠΎΠ±Π·ΠΎΡ Π³Π΅Π½ΠΎΠΌΠ° P. fluorescens SBW25 Π²ΡΡΠ²ΠΈΠ» ΠΏΠΎΡΠ΅Π½ΡΠΈΠ°Π»ΡΠ½ΡΠΉ Π§Π-Π·Π°Π²ΠΈΡΠΈΠΌΡΠΉ ΡΠ΅Π³ΡΠ»ΡΡΠΎΡΠ½ΡΠΉ ΠΏΡ ΡΡ ΠΈ Π΄ΡΡΠ³ΠΈΠ΅ Π§Π-Π·Π°Π²ΠΈΡΠΈΠΌΡΠ΅ Π³Π΅Π½Ρ, ΡΠ²ΡΠ·Π°Π½Π½ΡΠ΅ Ρ Π³ΠΎΠΌΠ΅ΠΎΡΡΠ°Π·ΠΎΠΌ Ρ-Π΄ΠΈ-ΠΠΠ€, Π° ΠΌΠΎΠ»Π΅ΠΊΡΠ»Ρ Π§Π-ΡΠΈΠ³Π½Π°Π»ΠΈΠ½Π³Π° Π±ΡΠ»ΠΈ ΠΈΠ΄Π΅Π½ΡΠΈΡΠΈΡΠΈΡΠΎΠ²Π°Π½Ρ Π² ΠΊΡΠ»ΡΡΡΡΠ΅. ΠΡΠΈ Π΄Π°Π½Π½ΡΠ΅ ΡΠ²ΠΈΠ΄Π΅ΡΠ΅Π»ΡΡΡΠ²ΡΡΡ ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΠΉ ΡΠ²ΡΠ·ΠΈ ΠΌΠ΅ΠΆΠ΄Ρ Ρ-Π΄ΠΈ-ΠΠΠ€-ΡΠ΅Π³ΡΠ»ΡΡΠΈΠ΅ΠΉ ΠΈ Π§Π Ρ P. fluorescens SBW25, ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ Π±ΠΎΠ»Π΅Π΅ ΡΠ»ΠΎΠΆΠ½ΡΠΉ ΠΈ Π³ΠΈΠ±ΠΊΠΈΠΉ ΠΊΠΎΠ½ΡΡΠΎΠ»Ρ Π½Π°Π΄ ΠΏΡΠΎΠ΄ΡΠΊΡΠΈΠ΅ΠΉ ΡΠ΅Π»Π»ΡΠ»ΠΎΠ·Ρ ΠΈ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈ Π΅ΠΌ Π±ΠΈΠΎΠΏΠ»Π΅Π½ΠΊΠΈ ΠΏΡΠΈ ΠΊΠΎΠ»ΠΎΠ½ΠΈΠ·Π°ΡΠΈΠΈ ΠΏΠΎΡΠ² ΠΈ ΡΠΊΠΎΠ½ΠΈΡ, aΡΡΠΎΡΠΈΠΈΡΠΎΠ²Π°Π½Π½ΡΡ
Ρ ΡΠ°ΡΡΠ΅Π½ΠΈΡΠΌ ΠΈ, - Π΅ΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΠΌΠΈ ΡΡΠ΅Π΄Π°ΠΌΠΈ ΠΎΠ±ΠΈΡΠ°Π½ΠΈΡ P. fluorescens SBW25
The true reinforced random walk with bias
We consider a self-attracting random walk in dimension d=1, in presence of a
field of strength s, which biases the walker toward a target site. We focus on
the dynamic case (true reinforced random walk), where memory effects are
implemented at each time step, differently from the static case, where memory
effects are accounted for globally. We analyze in details the asymptotic
long-time behavior of the walker through the main statistical quantities (e.g.
distinct sites visited, end-to-end distance) and we discuss a possible mapping
between such dynamic self-attracting model and the trapping problem for a
simple random walk, in analogy with the static model. Moreover, we find that,
for any s>0, the random walk behavior switches to ballistic and that field
effects always prevail on memory effects without any singularity, already in
d=1; this is in contrast with the behavior observed in the static model.Comment: to appear on New J. Phy
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