2,114 research outputs found
The 1988 Solar Maximum Mission event list
Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1988 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x ray burst spectrometer; (3) flat crystal spectrometers; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronagraph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts, or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observation. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included
Colloids with key-lock interactions: non-exponential relaxation, aging and anomalous diffusion
The dynamics of particles interacting by key-lock binding of attached
biomolecules are studied theoretically. Experimental realizations of such
systems include colloids grafted with complementary single-stranded DNA
(ssDNA), and particles grafted with antibodies to cell-membrane proteins.
Depending on the coverage of the functional groups, we predict two distinct
regimes. In the low coverage localized regime, there is an exponential
distribution of departure times. As the coverage is increased the system enters
a diffusive regime resulting from the interplay of particle desorption and
diffusion. This interplay leads to much longer bound state lifetimes, a
phenomenon qualitatively similar to aging in glassy systems. The diffusion
behavior is analogous to dispersive transport in disordered semiconductors:
depending on the interaction parameters it may range from a finite
renormalization of the diffusion coefficient to anomalous, subdiffusive
behavior. We make connections to recent experiments and discuss the
implications for future studies.Comment: v2: substantially revised version, new treatment of localized regime,
19 pages, 10 figure
The 1980 solar maximum mission event listing
Information is contained on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1980 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Hard X-Ray Imaging Spectrometer, (4) Flat Crystal Spectrometer, (5) Bent Crystal Spectrometer, (6) Ultraviolet Spectrometer and Polarimeter, and (7) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from Sun center are also included
The 1984 - 1987 Solar Maximum Mission event list
Information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1984-1987 pointed observations is presented. Data from the following SMM experiments are included: (1) gamma ray spectrometer; (2) hard x-ray burst spectrometer; (3) flat crystal spectrometer; (4) bent crystal spectrometer; (5) ultraviolet spectrometer polarimeter; and (6) coronograph/polarimeter. Correlative optical, radio, and Geostationary Operational Environmental Satellite (GOES) x ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included
Statistical Mechanics of DNA-Mediated Colloidal Aggregation
We present a statistical mechanical model of aggregation in colloidal systems
with DNA mediated interactions. We obtain a general result for the two-particle
binding energy in terms of the hybridization free energy of DNA and
two model dependent properties: the average number of available DNA bridges
\left and the effective DNA conccentration . We calculate
these parameters for a particular DNA bridging scheme. The fraction of all the
-mers, including the infinite aggregate, are shown to be universal functions
of a single parameter directly related to the two-particle binding energy. We
explicitly take into account the partial ergodicity of the problem resulting
from the slow DNA binding-unbinding dynamics, and introduce the concept of
angular localization of DNA linkers. In this way, we obtain a direct link
between DNA thermodynamics and the global aggregation and melting properties in
DNA-colloidal systems. The results of the theory are shown to be in
quantitative agreement with two recent experiments with particles of micron and
nanometer size.
PACS numbers: 81.16.Dn, 82.20.Db, 68.65.-k, 87.14.GgComment: 12 pages, 6 figures, v2: added reference, expanded conclusion, added
journal re
The 1989 Solar Maximum Mission event list
This document contains information on solar burst and transient activity observed by the Solar Maximum Mission (SMM) during 1989 pointed observations. Data from the following SMM experiments are included: (1) Gamma Ray Spectrometer, (2) Hard X-Ray Burst Spectrometer, (3) Flat Crystal Spectrometer, (4) Bent Crystal Spectrometer, (5) Ultraviolet Spectrometer Polarimeter, and (6) Coronagraph/Polarimeter. Correlative optical, radio, and Geostationary Operational Satellite (GOES) X-ray data are also presented. Where possible, bursts or transients observed in the various wavelengths were grouped into discrete flare events identified by unique event numbers. Each event carries a qualifier denoting the quality or completeness of the observations. Spacecraft pointing coordinates and flare site angular displacement values from sun center are also included
Doubly Special Relativity with a minimum speed and the Uncertainty Principle
The present work aims to search for an implementation of a new symmetry in
the space-time by introducing the idea of an invariant minimum speed scale
(). Such a lowest limit , being unattainable by the particles, represents
a fundamental and preferred reference frame connected to a universal background
field (a vacuum energy) that breaks Lorentz symmetry. So there emerges a new
principle of symmetry in the space-time at the subatomic level for very low
energies close to the background frame (), providing a fundamental
understanding for the uncertainty principle, i.e., the uncertainty relations
should emerge from the space-time with an invariant minimum speed.Comment: 10 pages, 8 figures, Correlated paper in:
http://www.worldscientific.com/worldscinet/ijmpd?journalTabs=read. arXiv
admin note: substantial text overlap with arXiv:physics/0702095,
arXiv:0705.4315, arXiv:0709.1727, arXiv:0805.120
Posterior parietal cortex guides visual decisions in rats
Neurons in putative decision-making structures can reflect both sensory and decision signals, making their causal role in decisions unclear. Here, we tested whether rat posterior parietal cortex (PPC) is causal for processing visual sensory signals or instead for accumulating evidence for decision alternatives. We optogenetically disrupted PPC activity during decision-making and compared effects on decisions guided by auditory vs. visual evidence. Deficits were largely restricted to visual decisions. To further test for visual dominance in PPC, we evaluated electrophysiological responses following individual sensory events and observed much larger response modulation following visual stimuli than auditory stimuli. Finally, we measured trial-to-trial spike count variability during stimulus presentation and decision formation. Variability sharply decreased, suggesting the network is stabilized by inputs, unlike what would be expected if sensory signals were locally accumulated. Our findings argue that PPC plays a causal role in processing visual signals that are accumulated elsewhere.SIGNIFICANCE STATEMENTDefining the neural circuits that support decision-making bridges a gap between our understanding of simple sensorimotor reflexes and our understanding of truly complex behavior. However, identifying brain areas which play a causal role in decision-making has proved challenging. We tested the causal role of a candidate component of decision circuits, the rat posterior parietal cortex (PPC). Our interpretation of the data benefitted from our use of animals trained to make decisions guided by either visual or auditory evidence. Our results argue that PPC plays a causal role specifically in visual decision-making, and that PPC may support sensory aspects of the decision, such as interpreting the visual signals so that evidence for a decision can be accumulated elsewhere
Vertex operators and the geometry of moduli spaces of framed torsion-free sheaves
We define complexes of vector bundles on products of moduli spaces of framed
rank r torsion-free sheaves on the complex projective plane. The top
non-vanishing Chern classes of the cohomology of these complexes yield actions
of the r-colored Heisenberg and Clifford algebras on the equivariant cohomology
of the moduli spaces. In this way we obtain a geometric realization of the
boson-fermion correspondence and related vertex operators.Comment: 36 pages; v2: Definition of geometric Heisenberg operators modified;
v3: Minor typos correcte
Science through Machine Learning: Quantification of Poststorm Thermospheric Cooling
Machine learning (ML) is often viewed as a black-box regression technique
that is unable to provide considerable scientific insight. ML models are
universal function approximators and - if used correctly - can provide
scientific information related to the ground-truth dataset used for fitting. A
benefit to ML over parametric models is that there are no predefined basis
functions limiting the phenomena that can be modeled. In this work, we develop
ML models on three datasets: the Space Environment Technologies (SET) High
Accuracy Satellite Drag Model (HASDM) density database, a spatiotemporally
matched dataset of outputs from the Jacchia-Bowman 2008 Empirical Thermospheric
Density Model (JB2008), and an accelerometer-derived density dataset from
CHAllenging Minisatellite Payload (CHAMP). These ML models are compared to the
Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar
(NRLMSIS 2.0) model to study the presence of post-storm cooling in the
middle-thermosphere. We find that both NRLMSIS 2.0 and JB2008-ML do not account
for post-storm cooling and consequently perform poorly in periods following
strong geomagnetic storms (e.g. the 2003 Halloween storms). Conversely,
HASDM-ML and CHAMP-ML do show evidence of post-storm cooling indicating that
this phenomenon is present in the original datasets. Results show that density
reductions up to 40% can occur 1--3 days post-storm depending on location and
the strength of the storm
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