6,181 research outputs found
Avian lens spectrin: subunit composition compared with erythrocyte and brain spectrin
Chicken lens spectrin is composed predominantly of equimolar amounts of two polypeptides with solubility properties similar, but not identical, to erythrocyte spectrin. The larger polypeptide, Mr 240,000 (lens alpha- spectrin), co-migrates with erythrocyte and brain alpha-spectrin on one- and two-dimensional SDS polyacrylamide gels and cross-reacts with antibodies specific for chicken erythrocyte alpha-spectrin; the smaller polypeptide, Mr 235,000 (lens gamma-spectrin), co-migrates with brain gamma-spectrin and does not cross-react with either the alpha-spectrin antibodies specific for chicken erythrocyte beta-spectrin. Minor amounts of polypeptides antigenically related to erythrocyte beta- spectrin with a greater electrophoretic mobility than lens gamma- spectrin are also detected in lens. The equimolar ratio of lens alpha- and gamma-spectrin is invariantly maintained during the extraction of lens plasma membranes under different conditions, or after immunoprecipitation of whole extracts of lens with erythrocyte alpha- spectrin antibodies. Two-dimensional peptide mapping reveals that whereas alpha-spectrins from chicken erythrocytes, brain, and lens are highly homologous, the gamma-spectrins, although related, have some cell-type-specific peptides and are substantially different from erythrocyte beta-spectrin. Thus, the expression of cell-type-specific gamma- and beta-spectrins may be the basis for the assembly of a spectrin-plasma membrane complex whose molecular composition is tailored to the functional requirements of the particular cell-type
Observation of chiral heat transport in the quantum Hall regime
Heat transport in the quantum Hall regime is investigated using micron-scale heaters and thermometers positioned along the edge of a millimeter-scale two dimensional electron system (2DES). The heaters rely on localized current injection into the 2DES, while the thermometers are based on the thermoelectric effect. In the v=1 integer quantized Hall state, a thermoelectric signal appears at an edge thermometer only when it is “downstream,” in the sense of electronic edge transport, from the heater. When the distance between the heater and the thermometer is increased, the thermoelectric signal is reduced, showing that the electrons cool as they propagate along the edge
Is Seasonal Adjustment a Linear or Nonlinear Data Filtering Process?
In this paper, we investigate whether seasonal adjustment procedures are, at least approximately, linear data transformations. This question is important with respect to many issues including estimation of regression models with seasonally adjusted data. We focus on the X-11 program and first review the features of the program that might be potential sources of nonlinearity. We rely on simulation evidence, involving linear unobserved component ARIMA models, to assess the adequacy of the linear approximation. We define a set of properties for the adequacy of a linear approximation to a seasonal adjustment filter. These properties are examined through statistical tests. Next, we study the effect of X-11 seasonal adjustment on regression statistics assessing the statistical significance of the relationship between economic variables in the same spirit as Sims (1974) and Wallis (1974). These findings are complemented with several empirical examples involving economic data.
Nous examinons si la procédure d'ajustement X-11 est approximativement linéaire. Il y a potentiellement plusieurs sources de non-linéarité dans cette procédure. Le but de l'étude est de savoir si ces sources sont effectivement assez importantes pour affecter, par exemple, des résultats d'estimation dans des modèles de régression linéaire. La seule façon de répondre à cette question est par estimation. Nous proposons plusieurs critères qu'on peut utiliser pour juger si une procédure d'ajustement est approximativement linéaire. Nous examinons également par simulation des propriétés de tests dans le modèle de régression dans le même esprit que Sims (1974) et Wallis (1974).X-11 program; Nonlinearity, X-11 program ; Nonlinearity
Smooth critical points of planar harmonic mappings
In a work in 1992, Lyzzaik studies local properties of light harmonic
mappings. More precisely, he classifies their critical points and accordingly
studies their topological and geometrical behaviours. We will focus our study
on smooth critical points of light harmonic maps. We will establish several
relationships between miscellaneous local invariants, and show how to connect
them to Lyzzaik's models. With a crucial use of Milnor fibration theory, we get
a fundamental and yet quite unexpected relation between three of the numerical
invariants, namely the complex multiplicity, the local order of the map and the
Puiseux pair of the critical value curve. We also derive similar results for a
real and complex analytic planar germ at a regular point of its Jacobian
level-0 curve. Inspired by Whitney's work on cusps and folds, we develop an
iterative algorithm computing the invariants. Examples are presented in order
to compare the harmonic situation to the real analytic one.Comment: 36 pages, 5 figure
A Tuneable Few Electron Triple Quantum Dot
In this paper we report on a tuneable few electron lateral triple quantum dot
design. The quantum dot potentials are arranged in series. The device is aimed
at studies of triple quantum dot properties where knowing the exact number of
electrons is important as well as quantum information applications involving
electron spin qubits. We demonstrate tuning strategies for achieving required
resonant conditions such as quadruple points where all three quantum dots are
on resonance. We find that in such a device resonant conditions at specific
configurations are accompanied by novel charge transfer behaviour.Comment: 11 pages, 4 figure
TETRA Observation of Gamma Rays at Ground Level Associated with Nearby Thunderstorms
Terrestrial Gamma ray Flashes (TGFs) -- very short, intense bursts of
electrons, positrons, and energetic photons originating from terrestrial
thunderstorms -- have been detected with satellite instruments. TETRA, an array
of NaI(Tl) scintillators at Louisiana State University, has now been used to
detect similar bursts of 50 keV to over 2 MeV gamma rays at ground level. After
2.6 years of observation, twenty-four events with durations 0.02- 4.2 msec have
been detected associated with nearby lightning, three of them coincident events
observed by detectors separated by ~1000 m. Nine of the events occurred within
6 msec and 3 miles of negative polarity cloud-to-ground lightning strokes with
measured currents in excess of 20 kA. The events reported here constitute the
first catalog of TGFs observed at ground level in close proximity to the
acceleration site.Comment: To be published in Journal of Geophysical Research: Space Phys. 118,
Creating an Ethical Awareness Using the Internet
Information access via the Internet becomes easier, more information becomes available, and more people access that information. Almost daily there are newspaper articles describing security breaches, viruses or other questionable behavior on the Internet. Therefore, the Information Superhighway provides opportunities that have not been previously addressed either legally or ethically. Information Systems (IS) students must not only learn technology and its uses, but must address the social and ethical issues that constantly arise. This paper uses the Internet to develop examples of ethical and legal issues the students face as they graduate into the business organization. A five step ethical analysis offers five moral dimensions of the information age - 1) Information Rights, 2) Property Rights, 3) Accountability, Liability and Control, 4) System Quality, 5) Quality of Life. These five themes encompass concerns often raised in discussions about ethics and information technology. Using these topics, some examples for integration of ethics throughout the undergraduate IS curriculum using the Internet, have been developed. These examples need not be limited to a specific IS course, but can be incorporated throughout the Information Systems undergraduate curriculum. Students need to develop an awareness of ethical issues surrounding emerging technologies
Nonclassical paths in the recurrence spectrum of diamagnetic atoms
Using time-independent scattering matrices, we study how the effects of
nonclassical paths on the recurrence spectra of diamagnetic atoms can be
extracted from purely quantal calculations. This study reveals an intimate
relationship between two types of nonclassical paths: exotic ghost orbits and
diffractive orbits. This relationship proves to be a previously unrecognized
reason for the success of semiclassical theories, like closed-orbit theory, and
permits a comprehensive reformulation of the semiclassical theory that
elucidates its convergence properties.Comment: 5 pages, 4 figure
Error Correction in Vergence Eye Movements: Evidence Supporting Hering’s Law
In pure symmetrical vergence eye movements, a fusion initiating component quickly brings the eyes close to the desired position. A small error usually remains after this response which must be corrected to attain the small final vergence error (i.e., fixation disparity). Error correction will usually involve both version and version movements so possible mechanisms include: small saccades, smooth pursuit, symmetrical vergence, or some combination. Alternatively, an asymmetrical vergence or uniocular slow eye movement could be used to achieve the highly precise final position. Saccade-free late fusion sustaining components during the steady state to a symmetrical vergence step stimulus are analyzed using independent component analysis. Results suggest that fine correction is most likely the product of closely coordinated version and vergence components
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