33,172 research outputs found
Microlensing in phase space II: Correlations analysis
Applications of the phase space approach to the calculation of the
microlensing autocorrelation function are presented. The continuous propagation
equation for a random star field with a Gaussian velocity distribution is
solved in the leading non-trivial approximation using the perturbation
technique. It is shown that microlensing modulations can be important in the
interpretation of optical and shorter-wavelength light curves of pulsars, power
spectra of active galactic nuclei and coherence estimates for quasi-periodic
oscillations of dwarf novae and low-mass X-ray binaries. Extra scatter in the
brightness of type Ia supernovae due to gravitational microlensing is shown to
be of order up to 0.2 stellar magnitudes depending on the extent of the light
curves.Comment: Accepted for publication in MNRAS. 17 pages, 8 figures. The first
part of this little series is available at
http://www.arxiv.org/abs/astro-ph/0604302 . Replaced to add a link to the
first par
Remotely sensed and laboratory spectral signatures of an ocean-dumped acid waste
An ocean-dumped acid waste plume was studied by using a rapid scanning spectrometer to remotely measure ocean radiance from a helicopter. The results of these studies are presented and compared with results from sea truth samples and laboratory experiments. An ocean spectral reflectance signature and a laboratory spectral transmission signature were established for the iron-acid waste pollutant. The spectrally and chemically significant component of the acid waste pollutant was determined to be ferric iron
Simultaneous muscle force and displacement transducer
A myocardial transducer for simultaneously measuring force and displacement within a very small area of myocardium is disclosed. The transducer comprised of an elongated body forked at one end to form an inverted Y shaped beam with each branch of the beam constituting a low compliant tine for penetrating the myocardium to a predetermined depth. Bonded to one of the low compliance tines is a small piezoresistive element for converting a force acting on the beam into an electrical signal. A third high compliant tine of the transducer, which measures displacement of the myocardium in a direction in line with the two low compliant tines, is of a length that just pierces the surface membrane. A small piezoresistive element is bonded to the third tine at its upper end where its bending is greatest. Displacement of the myocardium causes a deformation in curvature of the third tine, and the second small piezoresistive element bonded to the surface of its curved end converts its deformation into an electrical signal
KCNE1 and KCNE2 provide a checkpoint governing voltage-gated potassium channel α-subunit composition
AbstractVoltage-gated potassium (Kv) currents generated by N-type α-subunit homotetramers inactivate rapidly because an N-terminal ball domain blocks the channel pore after activation. Hence, the inactivation rate of heterotetrameric channels comprising both N-type and non-N-type (delayed rectifier) α-subunits depends upon the number of N-type α-subunits in the complex. As Kv channel inactivation and inactivation recovery rates regulate cellular excitability, the composition and expression of these heterotetrameric complexes are expected to be tightly regulated. In a companion article, we showed that the single transmembrane segment ancillary (β) subunits KCNE1 and KCNE2 suppress currents generated by homomeric Kv1.4, Kv3.3, and Kv3.4 channels, by trapping them early in the secretory pathway. Here, we show that this trapping is prevented by coassembly of the N-type α-subunits with intra-subfamily delayed rectifier α-subunits. Extra-subfamily delayed rectifier α-subunits, regardless of their capacity to interact with KCNE1 and KCNE2, cannot rescue Kv1.4 or Kv3.4 surface expression unless engineered to interact with them using N-terminal A and B domain swapping. The KCNE1/2-enforced checkpoint ensures N-type α-subunits only reach the cell surface as part of intra-subfamily mixed-α complexes, thereby governing channel composition, inactivation rate, and—by extension—cellular excitability
Microlensing in phase space I: Continuous propagation of variability moments
A method to calculate the statistical properties of microlensing light curves
is developed. The approach follows works by Deguchi & Watson, Seitz & Schneider
and Neindorf, attempting to clarify the ideas involved and techniques used in
the calculations. The method is then modified to include scattering by multiple
lensing planes along the line of sight and transition to a continuous limit of
this treatment for average quantities is performed leading to a Fokker-Planck
type equation. The equation is solved for a particular model of the random star
field and microlensing effect on the flux temporal variability is extracted.
Applications in astrophysically relevant situations are discussed.Comment: Accepted for publication in MNRAS. 15 pages, 4 figures. The second
part of this little series is available at
http://www.arxiv.org/abs/astro-ph/060419
Multifunctional transducer
Several parameters of a small region of a muscle tissue or other object, can be simultaneously measured using with minimal traumatizing or damage of the object, a trifunctional transducer which can determine the force applied by a muscle fiber, the displacement of the fiber, and the change in thickness of the fiber. The transducer has three legs with inner ends joined together and outer ends formed to piece the tissue and remain within it. Two of the legs are relatively stiff, to measure force applied by the tissue, and a third leg is relatively flexible to measure displacement of the tissue relative to one or both stiff legs, and with the three legs lying in a common plane so that the force and displacement measurements all relate to the same direction of muscle movements. A flexible loop is attached to one of the stiff legs to measure changes in muscle thickness, with the upper end of the loop fixed to the leg and the lower end of the loop bearing against the surface of the tissue and being free to slide on the leg
Myocardium wall thickness transducer and measuring method
A miniature transducer for measuring changes of thickness of the myocardium is described. The device is easily implantable without traumatizing the subject, without affecting the normal muscle behavior, and is removable and implantable at a different muscle location. Operating features of the device are described
Catheter tip force transducer for cardiovascular research
A force transducer for measuring dynamic force activity within the heart of a subject essentially consists of a U-shaped beam of low elastic compliance material. Two lines extend from the beams's legs and a long coil spring is attached to the beam. A strain gauge is coupled to one of the beam's legs to sense deflections thereof. The beam with the tines and most of the spring are surrounded by a flexible tube, defining a catheter, which is insertable into a subject's heart through an appropriate artery. The tines are extractable from the catheter for implantation into the myocardium by pushing on the end of the spring which extends beyond the external end of the catheter
Microlensing of Broad Absorption Line Quasars: Polarization Variability
Roughly 10% of all quasars exhibit Broad Absorption Line (BAL) features which
appear to arise in material outflowing at high velocity from the active
galactic nucleus (AGN). The details of this outflow are, however, very poorly
constrained and the particular nature of the BAL material is essentially
unknown. Recently, new clues have become available through polarimetric studies
which have found that BAL troughs are more polarized than the quasar continuum
radiation. To explain these observations, models where the BAL material
outflows equatorially across the surface of the dusty torus have been
developed. In these models, however, several sources of the BAL polarization
are possible. Here, we demonstrate how polarimetric monitoring of
gravitationally lensed quasars, such as H 1413+117, during microlensing events
can not only distinguish between two currently popular models, but can also
provide further insight into the structure at the cores of BAL quasars.Comment: 17 pages, 3 figures, accepted to PAS
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