281 research outputs found
A model of interplanetary and coronal magnetic fields
Model of interplanetary and solar magnetic field structure above photosphere using Green function solution to Maxwell equation
Magnetic field observations near Mercury: Preliminary results from Mariner 10
Results are presented from a preliminary analysis of data obtained near Mercury by the NASA/GSFC Magnetic Field Experiment on Mariner 10. A very well developed, detached bow shock wave, which developed as the super-Alfvenic solar wind interacted with the planet Mercury was observed. A magnetosphere-like region, with maximum field strength of 98 gamma at closest approach (704 km altitude) was also observed, and was contained within boundaries similar to the terrestrial magnetopause. The obstacle deflecting the solar wind flow was global in size, but the origin of the enhanced magnetic field was not established. The most plausible explanation, considering the complete body of data, favored the conclusion that Mercury has an intrinsic magnetic field
Lazy states: sufficient and necessary condition for zero quantum entropy rates under any coupling to the environment
We find the necessary and sufficient conditions for the entropy rate of the
system to be zero under any system-environment Hamiltonian interaction. We call
the class of system-environment states that satisfy this condition lazy states.
They are a generalization of classically correlated states defined by quantum
discord, but based on projective measurements of any rank. The concept of lazy
states permits the construction of a protocol for detecting global quantum
correlations using only local dynamical information. We show how quantum
correlations to the environment provide bounds to the entropy rate, and how to
estimate dissipation rates for general non-Markovian open quantum systems.Comment: 4 page
Bioelectric responses at fertilization : separation of the events associated with insemination from those due to the cortical reaction in sea urchin, Lytechinus variegatus
The bioelectric responses at fertilization of the sea urchin Lytechinus variegatus are a complex series of membrane potential and resistance changes that occur concomitant with gamete fusion, ionic fluxes, and the cortical granule discharge. This work attempts to separate the electrical effects of sperm-egg interactions from those of the cortical reactions. Two approaches were taken to discern the electrical events associated with insemination, distinct from cortical granule discharge: (1) fertilization of eggs treated with 3% urethane, 10 mM procaine, or 10 mM nicotine, to prevent the cortical reaction and (2) refertilization of fertilized eggs (denuded with 1 mM aminotriazole containing 1 mg/ml soybean trypsin inhibitor). Cortical granule discharge in the absence of sperm incorporation was investigated by artificial activation with 5 μM A23187 or by fertilization in the presence of 10 μM cytochalasin D, which prevents incorporation. These results are consistent with a model in which the sperm-egg interaction triggers both a rapid (50-400 msec), but minor (≅10 mV), electrical transient that leads to an action potential and then both the Na+-dependent fast block to polyspermy and the late block resulting from the secretion of the cortical granules
Non-local Correlations are Generic in Infinite-Dimensional Bipartite Systems
It was recently shown that the nonseparable density operators for a bipartite
system are trace norm dense if either factor space has infinite dimension. We
show here that non-local states -- i.e., states whose correlations cannot be
reproduced by any local hidden variable model -- are also dense. Our
constructions distinguish between the cases where both factor spaces are
infinite-dimensional, where we show that states violating the CHSH inequality
are dense, and the case where only one factor space is infinite-dimensional,
where we identify open neighborhoods of nonseparable states that do not violate
the CHSH inequality but show that states with a subtler form of non-locality
(often called "hidden" non-locality) remain dense.Comment: 8 pages, RevTe
Alternative fidelity measure for quantum states
We propose an alternative fidelity measure (namely, a measure of the degree
of similarity) between quantum states and benchmark it against a number of
properties of the standard Uhlmann-Jozsa fidelity. This measure is a simple
function of the linear entropy and the Hilbert-Schmidt inner product between
the given states and is thus, in comparison, not as computationally demanding.
It also features several remarkable properties such as being jointly concave
and satisfying all of "Jozsa's axioms". The trade-off, however, is that it is
supermultiplicative and does not behave monotonically under quantum operations.
In addition, new metrics for the space of density matrices are identified and
the joint concavity of the Uhlmann-Jozsa fidelity for qubit states is
established.Comment: 12 pages, 3 figures. v2 includes minor changes, new references and
new numerical results (Sec. IV
The Magnetic Field of the Solar Corona from Pulsar Observations
We present a novel experiment with the capacity to independently measure both
the electron density and the magnetic field of the solar corona. We achieve
this through measurement of the excess Faraday rotation due to propagation of
the polarised emission from a number of pulsars through the magnetic field of
the solar corona. This method yields independent measures of the integrated
electron density, via dispersion of the pulsed signal and the magnetic field,
via the amount of Faraday rotation. In principle this allows the determination
of the integrated magnetic field through the solar corona along many lines of
sight without any assumptions regarding the electron density distribution. We
present a detection of an increase in the rotation measure of the pulsar
J18012304 of approximately 160 \rad at an elongation of 0.95 from
the centre of the solar disk. This corresponds to a lower limit of the magnetic
field strength along this line of sight of . The lack of
precision in the integrated electron density measurement restricts this result
to a limit, but application of coronal plasma models can further constrain this
to approximately 20mG, along a path passing 2.5 solar radii from the solar
limb. Which is consistent with predictions obtained using extensions to the
Source Surface models published by Wilcox Solar ObservatoryComment: 16 pages, 4 figures (1 colour): Submitted to Solar Physic
Evaluation of Dynamic Cell Processes and Behavior Using Video Bioinformatics Tools
Just as body language can reveal a person’s state of well-being, dynamic changes in cell behavior and
morphology can be used to monitor processes in cultured cells. This chapter discusses how CL-Quant
software, a commercially available video bioinformatics tool, can be used to extract quantitative data on:
(1) growth/proliferation, (2) cell and colony migration, (3) reactive oxygen species (ROS) production, and
(4) neural differentiation. Protocols created using CL-Quant were used to analyze both single cells and
colonies. Time-lapse experiments in which different cell types were subjected to various chemical
exposures were done using Nikon BioStations. Proliferation rate was measured in human embryonic stem
cell colonies by quantifying colony area (pixels) and in single cells by measuring confluency (pixels).
Colony and single cell migration were studied by measuring total displacement (distance between the
starting and ending points) and total distance traveled by the colonies/cells. To quantify ROS production,
cells were pre-loaded with MitoSOX Redâ„¢, a mitochondrial ROS (superoxide) indicator, treated with
various chemicals, then total intensity of the red fluorescence was measured in each frame. Lastly, neural
stem cells were incubated in differentiation medium for 12 days, and time lapse images were collected
daily. Differentiation of neural stem cells was quantified using a protocol that detects young neurons. CLQuant
software can be used to evaluate biological processes in living cells, and the protocols developed in
this project can be applied to basic research and toxicological studies, or to monitor quality control in
culture facilities
Active region formation through the negative effective magnetic pressure instability
The negative effective magnetic pressure instability operates on scales
encompassing many turbulent eddies and is here discussed in connection with the
formation of active regions near the surface layers of the Sun. This
instability is related to the negative contribution of turbulence to the mean
magnetic pressure that causes the formation of large-scale magnetic structures.
For an isothermal layer, direct numerical simulations and mean-field
simulations of this phenomenon are shown to agree in many details in that their
onset occurs at the same depth. This depth increases with increasing field
strength, such that the maximum growth rate of this instability is independent
of the field strength, provided the magnetic structures are fully contained
within the domain. A linear stability analysis is shown to support this
finding. The instability also leads to a redistribution of turbulent intensity
and gas pressure that could provide direct observational signatures.Comment: 19 pages, 10 figures, submitted to Solar Physic
Where Do I Come From? Metaphors in Sex Education Picture Books for Young Children in China
This study examines the types of verbal, pictorial, and multimodal metaphors in the genre of sex education picture books for young children in Mainland China. Although being an educational discourse genre that is essentially concerned with transmitting scientific facts, sex education picture books employ a range of metaphors that categorize and construe the biological knowledge of human reproduction in a way that not only facilitates young children’s understanding of scientific concepts but also instills in them particular values and moralities that are socioculturally conditioned. An examination of the source domains from which the metaphors are drawn and the target domains onto which the metaphors are mapped reveals three types of metaphor, namely, personification, domestication, and cross-experience metaphors. The analysis of seven sex education picture books for pre-school children suggests that these types of metaphor are used purposefully for addressing pedagogical as well as ideological concerns in the introduction of sex-related knowledge in Mainland China
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